Re: [Emc-users] Just took the first flexgear off the printer

[Chris Albertson]

Gene,

There about many settings in Cura for supports.  You can waste tons of
time and plastic experimenting or just use a pair of needle-nose
pliers and pull it off as you did.

The best fix is to get a second extruder on the printer and load it
with water-soluble filament and print support with that.  Then dunk
the part in water. But this at least doubles the price of the printer

On Tue, Jul 21, 2020 at 10:17 PM Gene Heskett  wrote:
>
> Greetings all;
>
> And had a hell of a time removing the internal supports, which probably
> out-weigh the gear, digging it out about 1/4" at a time until I was able
> to actually get a grip on the edge, at which time the last half of it
> popped right out in one piece, clean as a whistle.  But it seems like
> there ought to be a way to pop it all out in one piece as opposed to a
> couple hours work with a miniature back hoe in the form of the e. tech's
> ever present 5" flush cutters. Looks good, meshes well and walks around
> the ring gear like it should. 2nd one building, be done around a late
> dinner time tonight as its an 18+ hour job. Don't know if theres enough
> PLA on that spool for 3 of them. With all the support structure it uses
> a lot of PLA. Cura estimates it but I've forgotten now.
>
> But is there a support removal tool that isn't radioactive?
>
> Cheers, Gene Heskett
> --
> "There are four boxes to be used in defense of liberty:
>  soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> If we desire respect for the law, we must first make the law respectable.
>  - Louis D. Brandeis
> Genes Web page 
>
>
> ___
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> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users



-- 

Chris Albertson
Redondo Beach, California


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Re: [Emc-users] Just took the first flexgear off the printer

[Gregg Eshelman via Emc-users]

Design a sacrificial piece that fits closely but not too closely to the inside 
area that needs supported. There are plenty of models to download that have 
support structures as part of the design, with just the right gap between their 
top surface and the underside of what they're supporting so they'll easily come 
off and leave a good surface.

Make it solid with several internal voids that have a pointed top at the angle 
you have set to not need supports. The walls can be pretty thin, I'd try for a 
spoked design sort of like a spigot handle. Then you'll have the upper surface 
solid and ribs on the bottom to grab with pliers.

To figure out the space you need to not permanently adhere the sacrificial 
support to the model, make a simple model of an inverted U with a straight 
horizontal bar and a block that almost but not quite fills the center. No need 
to make it huge. Adjust the height of the support block until you get the 
results you want.
A nifty thing that can be done with 3D printing is a light press/snap fit. On 
this thing the three towers fit firmly into recesses in the base while the thin 
gears used for adjustment thumbwheels are a perfect sliding fit so a few drops 
of super glue gel hold them. https://www.thingiverse.com/thing:1752729 I tried 
a few times to make a proper thread for the two adjusters but couldn't make it 
work so I went with a loose fit with two coarse spiral grooves and a pair of 
pins on the rotating part. Inspiration was early rifled cannon that used lugged 
projectiles.

I've also used a fit that uses the layer lines to snap together but not so 
tight they're inseparable. Works well for jigs that need to hold together for 
things like holding pieces into 3D printed knobs filled with resin while the 
resin cures.

On Tuesday, July 21, 2020, 11:18:06 PM MDT, Gene Heskett 
 wrote:  
 Greetings all;

And had a hell of a time removing the internal supports, which probably 
out-weigh the gear, digging it out about 1/4" at a time until I was able 
to actually get a grip on the edge, at which time the last half of it 
popped right out in one piece, clean as a whistle.  But it seems like 
there ought to be a way to pop it all out in one piece as opposed to a 
couple hours work with a miniature back hoe in the form of the e. tech's 
ever present 5" flush cutters. Looks good, meshes well and walks around 
the ring gear like it should. 2nd one building, be done around a late 
dinner time tonight as its an 18+ hour job. Don't know if theres enough 
PLA on that spool for 3 of them. With all the support structure it uses 
a lot of PLA. Cura estimates it but I've forgotten now.

But is there a support removal tool that isn't radioactive?
  
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Re: [Emc-users] need a logic bit mux.

[andy pugh]

On Wed, 22 Jul 2020 at 07:20, Gene Heskett  wrote:

> So I need a 1 or 2 second delay before that bit is sent on thru, but
> instant transmission once timed out, giving the driver a chance to get
> all its stuff in one sock from the powerup enabled by the F2 key. I want
> to block any noise during the powerup surge

The title says that you need a bit mux. mux_generic can do bits.

Triggering a mux from a timedelay is one way. But is probably
equivalent to an and2 + timedelay.
It isn't clear what signal you want to block, or under what
circumstances you want to have the delay.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912


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Re: [Emc-users] Just took the first flexgear off the printer

[andy pugh]

On Wed, 22 Jul 2020 at 06:17, Gene Heskett  wrote:

> And had a hell of a time removing the internal supports, which probably
> out-weigh the gear

Perhaps you would have been better printing it the other way round?

I think I recall seeing someone use pause-at-height to apply an
anti-adhesion material  to the support, but can't remember where I saw
it, or what he used.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912


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Re: [Emc-users] @Andrew Beck, how did you get qtpyvcp working?

[andrew beck]

hey did you get this working?  i just saw this sorry


On Sun, Jun 7, 2020 at 1:32 AM Valerio Bellizzomi 
wrote:

> Hi, I would like to use qtpyvcp instead of gmoccapy, can you help me?
> How did you get qtpyvcp on LinuxCNC?
> and how did you configure it?
>
> Regards
>
>
>
>
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Re: [Emc-users] Just took the first flexgear off the printer

[Frank Tkalcevic]

> But is there a support removal tool that isn't radioactive?

Nope.  The secret is to design your parts so you don't need support.  

Unless you have a dual head extruder, then you can use a different material
as the support material.



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Re: [Emc-users] need a logic bit mux.

[Gene Heskett]

On Wednesday 22 July 2020 02:45:48 John Dammeyer wrote:

> > The launch of linuxcnc on the pi is without any motor power until
> > the F2 button is pushed.  So at launch time I get messages about the
> > z drive being tripped.
> >
> > So I need a 1 or 2 second delay before that bit is sent on thru, but
> > instant transmission once timed out, giving the driver a chance to
> > get all its stuff in one sock from the powerup enabled by the F2
> > key. I want to block any noise during the powerup surge.
> >
> > Ideas? Something simpler than a one-shot, and2 + a not, thats less
> > time in terms of the addf chain. Timer, driven from F2 I'm stuck
> > with, but is a lut5 faster than all the logic needed to "get the
> > signal right side up"  IDK.
>
> Hi Gene,
> I had similar issues.  The soft start on the Servo Power supply
> results in the STMBL servo drive faulting out when enabled because DC
> power isn't there yet.
>
> I ended up making a board with a PIC12C509 that is an 8 pin processor.
>  If I'd had an Arduino I'd probably have used that.  I now need a
> bigger one anyway since I want to separate the Spindle Enable from the
> rest of the Enables.
>
> But I used external hardware to do the time delays to make sure things
> started up the way I wanted.  You might also use time delay relays. 
> But they aren't cheap.  Ultimately an Arduino ends up being an easy
> solution.
>
> John Dammeyer

Why should I use any external hardware when LinuxCNC has the stuff built 
in? All I need to do is add it to the .hal file.
> > Thanks.
> >
> > Cheers, Gene Heskett
> > --
> > "There are four boxes to be used in defense of liberty:
> >  soap, ballot, jury, and ammo. Please use in that order."
> > -Ed Howdershelt (Author)
> > If we desire respect for the law, we must first make the law
> > respectable. - Louis D. Brandeis
> > Genes Web page 
> >
> >
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users


Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] Just took the first flexgear off the printer

[Gene Heskett]

On Wednesday 22 July 2020 03:34:01 Chris Albertson wrote:

> Gene,
>
> There about many settings in Cura for supports.  You can waste tons of
> time and plastic experimenting or just use a pair of needle-nose
> pliers and pull it off as you did.

Except I don't own any needle-nosed pliers. I was introduced to suture 
clamps in 1961 while building Titan 1's up in South Dakota. Never looked 
back. If I am wearing a shirt, there's usually a curved nose version 
clipped to the collar. Or 2 of them.

> The best fix is to get a second extruder on the printer and load it
> with water-soluble filament and print support with that.  Then dunk
> the part in water. But this at least doubles the price of the printer

Not something the ender-3 has room for. So I'm stuck useing the tools at 
hand. Since the base of the flexgear has 6 driving holes for bolts that 
drive its output flange, I am tempted to drill a long stick in the bolt 
pattern, put screws into it to engage those holes and twist it out in 
one piece.

Two problems remain, one being that I think the motor mount it makes is 
for a nema-23 and what I have are 17's, but small 23's are cheap, and 
looking at the bearing bar, the shaft hole isn't fitted with a shaft 
grabber of any kind. Might have to cobble up a taper-lock to fit 
whatever motor I use. Smaller than what I made for converting TLM.

The last thing, and biggest, is the housing and end cap. Over 3 days to 
render each pair of parts. By then I'm sure I will have opened the 2nd 
spool of PLA I ordered with the printer.

> On Tue, Jul 21, 2020 at 10:17 PM Gene Heskett  
wrote:
> > Greetings all;
> >
> > And had a hell of a time removing the internal supports, which
> > probably out-weigh the gear, digging it out about 1/4" at a time
> > until I was able to actually get a grip on the edge, at which time
> > the last half of it popped right out in one piece, clean as a
> > whistle.  But it seems like there ought to be a way to pop it all
> > out in one piece as opposed to a couple hours work with a miniature
> > back hoe in the form of the e. tech's ever present 5" flush cutters.
> > Looks good, meshes well and walks around the ring gear like it
> > should. 2nd one building, be done around a late dinner time tonight
> > as its an 18+ hour job. Don't know if theres enough PLA on that
> > spool for 3 of them. With all the support structure it uses a lot of
> > PLA. Cura estimates it but I've forgotten now.
> >
> > But is there a support removal tool that isn't radioactive?
> >
> > Cheers, Gene Heskett
> > --
> > "There are four boxes to be used in defense of liberty:
> >  soap, ballot, jury, and ammo. Please use in that order."
> > -Ed Howdershelt (Author)
> > If we desire respect for the law, we must first make the law
> > respectable. - Louis D. Brandeis
> > Genes Web page 
> >
> >
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users


Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] Just took the first flexgear off the printer

[Gene Heskett]

On Wednesday 22 July 2020 03:39:02 Gregg Eshelman via Emc-users wrote:

> Design a sacrificial piece that fits closely but not too closely to
> the inside area that needs supported. There are plenty of models to
> download that have support structures as part of the design, with just
> the right gap between their top surface and the underside of what
> they're supporting so they'll easily come off and leave a good
> surface.

The only BOM is the .step file. freecad renders it but shows only the 
final assembly. A freecad newbie, I need to figure out how to separate 
the parts, or x-ray vision. The .stl files fill all available space with 
supports with only a 15 thou clearance to the real part, not conducive 
to getting a prybar under it it at all.

> Make it solid with several internal voids that have a pointed top at
> the angle you have set to not need supports. The walls can be pretty
> thin, I'd try for a spoked design sort of like a spigot handle. Then
> you'll have the upper surface solid and ribs on the bottom to grab
> with pliers.
>
> To figure out the space you need to not permanently adhere the
> sacrificial support to the model, make a simple model of an inverted U
> with a straight horizontal bar and a block that almost but not quite
> fills the center. No need to make it huge. Adjust the height of the
> support block until you get the results you want. A nifty thing that
> can be done with 3D printing is a light press/snap fit. On this thing
> the three towers fit firmly into recesses in the base while the thin
> gears used for adjustment thumbwheels are a perfect sliding fit so a
> few drops of super glue gel hold them.
> https://www.thingiverse.com/thing:1752729 I tried a few times to make
> a proper thread for the two adjusters but couldn't make it work so I
> went with a loose fit with two coarse spiral grooves and a pair of
> pins on the rotating part. Inspiration was early rifled cannon that
> used lugged projectiles.
>
> I've also used a fit that uses the layer lines to snap together but
> not so tight they're inseparable. Works well for jigs that need to
> hold together for things like holding pieces into 3D printed knobs
> filled with resin while the resin cures.
>
> On Tuesday, July 21, 2020, 11:18:06 PM MDT, Gene Heskett
>  wrote: Greetings all;
>
> And had a hell of a time removing the internal supports, which
> probably out-weigh the gear, digging it out about 1/4" at a time until
> I was able to actually get a grip on the edge, at which time the last
> half of it popped right out in one piece, clean as a whistle.  But it
> seems like there ought to be a way to pop it all out in one piece as
> opposed to a couple hours work with a miniature back hoe in the form
> of the e. tech's ever present 5" flush cutters. Looks good, meshes
> well and walks around the ring gear like it should. 2nd one building,
> be done around a late dinner time tonight as its an 18+ hour job.
> Don't know if theres enough PLA on that spool for 3 of them. With all
> the support structure it uses a lot of PLA. Cura estimates it but I've
> forgotten now.
>
> But is there a support removal tool that isn't radioactive?
>
> ___
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Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] need a logic bit mux.

[Gene Heskett]

On Wednesday 22 July 2020 03:51:34 andy pugh wrote:

> On Wed, 22 Jul 2020 at 07:20, Gene Heskett  
wrote:
> > So I need a 1 or 2 second delay before that bit is sent on thru, but
> > instant transmission once timed out, giving the driver a chance to
> > get all its stuff in one sock from the powerup enabled by the F2
> > key. I want to block any noise during the powerup surge
>
> The title says that you need a bit mux. mux_generic can do bits.
>
> Triggering a mux from a timedelay is one way. But is probably
> equivalent to an and2 + timedelay.
> It isn't clear what signal you want to block, or under what
> circumstances you want to have the delay.

Only long enough for the driver to stabilize after power up. One or 2 
seconds perhaps. Long before its asked to do any work, like homing.
Once I get rid of the spurious trip I'll trigger an e-stop with it, 
because if it trips, home has been lost anyway.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] Just took the first flexgear off the printer

[Gene Heskett]

On Wednesday 22 July 2020 04:29:41 andy pugh wrote:

> On Wed, 22 Jul 2020 at 06:17, Gene Heskett  
wrote:
> > And had a hell of a time removing the internal supports, which
> > probably out-weigh the gear
>
> Perhaps you would have been better printing it the other way round?
>
In retrospect, I think so, but my mind said I wanted the flex gear on the 
bed for accuracy. So I sliced it face down.

> I think I recall seeing someone use pause-at-height to apply an
> anti-adhesion material  to the support, but can't remember where I saw
> it, or what he used.

I'm still learning about these critters...

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] need a logic bit mux.

[andy pugh]

On Wed, 22 Jul 2020 at 12:12, Gene Heskett  wrote:

> > It isn't clear what signal you want to block, or under what
> > circumstances you want to have the delay.
>
> Only long enough for the driver to stabilize after power up. One or 2
> seconds perhaps

I wasn't asking how long. I was asking what pin.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912


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Re: [Emc-users] need a logic bit mux.

[Gene Heskett]

On Wednesday 22 July 2020 08:03:48 andy pugh wrote:

> On Wed, 22 Jul 2020 at 12:12, Gene Heskett  
wrote:
> > > It isn't clear what signal you want to block, or under what
> > > circumstances you want to have the delay.
> >
> > Only long enough for the driver to stabilize after power up. One or
> > 2 seconds perhaps
>
> I wasn't asking how long. I was asking what pin.
oh. This is what I have atm:
loadrt  debounce cfg=1
loadrt  message names="ZFault" messages="Z axis Faulted"
[...]
addfdebounce.0  jog-thread
addfZFault  jog-thread
# revel in the free time here from not having to run PID's
# every bit of the processing as set by addf order MUST BE DONE
# between the above read, and the below write.
addf hm2_[HOSTMOT2](BOARD).0.write   servo-thread
[...]
# display msg if Z drive in fault 
# hm2/hm2_7i90.0: IO Pin 061 (P3-31): IOPort
# is lowest numbered gpio used yet a/o 6/25/21
# is lowest numbered gpio used yet a/o 6/25/21
setp ZFault.edge 0
setp debounce.0.delay 1
net z-fault-in  <= hm2_[HOSTMOT2](BOARD).0.gpio.061.in => debounce.0.0.in
net z-fault-trig  <= debounce.0.0.out  => ZFault.trigger
net z-fault-trig  => halui.joint.0.unhome halui.joint.1.unhome

Which should more or less go away, the debounce delays everything, so is 
not really whats wanted.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] need a logic bit mux.

[Jon Elson]

On 07/22/2020 01:17 AM, Gene Heskett wrote:

Greetings all;

The launch of linuxcnc on the pi is without any motor power until the F2
button is pushed.  So at launch time I get messages about the z drive
being tripped.

So I need a 1 or 2 second delay before that bit is sent on thru, but
instant transmission once timed out, giving the driver a chance to get
all its stuff in one sock from the powerup enabled by the F2 key. I want
to block any noise during the powerup surge.


OK, so your drives indicate fault status when disabled?  
Yes, a lot of older drives (Copley, Westamp,
Servo Dynamics) do this.  I made up a module with an 
optocoupler, a CMOS NAND gate and
some RC delays to do this.  The servo amps usually take a 5 
V ENABLE/.  When the ENABLE/
is high, the circuit closes the E-stop loop by turning the 
optocoupler on.  When ENABLE/ goes
low, it continues to do this for about a second, then allows 
the servo amp's FAULT output to control the opto.


Jon


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Re: [Emc-users] need a logic bit mux.

[John Dammeyer]

> >
> > But I used external hardware to do the time delays to make sure things
> > started up the way I wanted.  You might also use time delay relays.
> > But they aren't cheap.  Ultimately an Arduino ends up being an easy
> > solution.
> >
> > John Dammeyer
> 
> Why should I use any external hardware when LinuxCNC has the stuff built
> in? All I need to do is add it to the .hal file.
> > > Thanks.
> > >
> > > Cheers, Gene Heskett

My system was dual boot to run both MACH3 and LinuxCNC.  I needed the hardware 
to behave in a deterministic way before the PC took control.

John




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[Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[John Dammeyer]

Ho Jon,
 
I've changed the subject line to be more relevant and corrected the gravity 
value.
 
Now we have 1703 In/Sec^2 for maximum possible acceleration given the load and 
torque ratings.
 
On my system in imperial units I have 2.5 inches/second and I randomly picked 
the accel as 3x that.  Does that mean I could set MAX_ACCEL to say 1700 and get 
away with that or is that number abnormally high?  I know I can try it but I'd 
like to know if the math is accurate.
 
MAX_VELOCITY = 2.5
MAX_ACCELERATION = 7.5
What I'm trying to do with this tool is to take out some of the guesswork or 
the accidental divide instead of multiply.
 
And second question. If someone is using metric units for their system what 
units are used to describe MAX_VELOCITY and ACCEL?
Is it mm/minute? Or mm/second?  Or meters/second?   Is the weight specified in 
grams or kg?
 
I want to be able to make the checkbox convert the imperial < = > metric 
correctly.
 

 
Thanks
John Dammeyer
 
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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[Sam Sokolik]

Is this stepper torque?  The peak torque is only at 0 rpm and drops off
substantially as you increase rpm.  You  would need to look a the torque
curve of the stepper and decide what top rpm you are looking for and
calculate accordingly..

On Wed, Jul 22, 2020, 11:09 AM John Dammeyer  wrote:

> Ho Jon,
>
> I've changed the subject line to be more relevant and corrected the
> gravity value.
>
> Now we have 1703 In/Sec^2 for maximum possible acceleration given the load
> and torque ratings.
>
> On my system in imperial units I have 2.5 inches/second and I randomly
> picked the accel as 3x that.  Does that mean I could set MAX_ACCEL to say
> 1700 and get away with that or is that number abnormally high?  I know I
> can try it but I'd like to know if the math is accurate.
>
> MAX_VELOCITY = 2.5
> MAX_ACCELERATION = 7.5
> What I'm trying to do with this tool is to take out some of the guesswork
> or the accidental divide instead of multiply.
>
> And second question. If someone is using metric units for their system
> what units are used to describe MAX_VELOCITY and ACCEL?
> Is it mm/minute? Or mm/second?  Or meters/second?   Is the weight
> specified in grams or kg?
>
> I want to be able to make the checkbox convert the imperial < = > metric
> correctly.
>
>
>
> Thanks
> John Dammeyer
>
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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[Chris Albertson]

I don't see any relation between max acceleration and max speed.
Acceleration is determined by (1) the mass of the table and (2) the
torque the motor can produce while speed is determined by the max RPM
of the motor.

It is very easy to buy a tiny motor with low torque that spins very
fast.  Or you can find powerful but slow motors.   Multiplying the
speed by three to find acceleration, if it works is just a
coincidence.  The factor could be 0.5 or 10.

There are two whys to go.  A mechanical engineer would start with a
requirement for a certain speed and a certain acceleration.  His boss
would give him those goals and then he would select a motor and drive.
  The other way used by most amateurs is to just buy a motor that
"seems right" and then test it to see what speed and a certain
acceleration you can get from it.

It both cases you end up iterating to the solution.  The engineer has
to tell his boss "Going that fast is going to make the machine very
expensive.  Are you sure you want those performance numbers?"  The
amateur looks at the results of testing and asking himself "Is it with
it to make otherguess and try another motors or do I live with this
one?"

That said acceleration is related to speed.   (acceleration) x (time) = (speed)
example:  (10 inch per second squared) x ( 0.5 seconds) = (5 inches per second)

In theory, if you had enough time the speed could be anything but
typically the motor only spins so fast and you hit some real-world
limit.

The bottom line is to test, find where it stops working reliably than
to be conservative cut those test results in half, and use that as
your limit.

On Wed, Jul 22, 2020 at 9:09 AM John Dammeyer  wrote:
>
> Ho Jon,
>
> I've changed the subject line to be more relevant and corrected the gravity 
> value.
>
> Now we have 1703 In/Sec^2 for maximum possible acceleration given the load 
> and torque ratings.
>
> On my system in imperial units I have 2.5 inches/second and I randomly picked 
> the accel as 3x that.  Does that mean I could set MAX_ACCEL to say 1700 and 
> get away with that or is that number abnormally high?  I know I can try it 
> but I'd like to know if the math is accurate.
>
> MAX_VELOCITY = 2.5
> MAX_ACCELERATION = 7.5
> What I'm trying to do with this tool is to take out some of the guesswork or 
> the accidental divide instead of multiply.
>
> And second question. If someone is using metric units for their system what 
> units are used to describe MAX_VELOCITY and ACCEL?
> Is it mm/minute? Or mm/second?  Or meters/second?   Is the weight specified 
> in grams or kg?
>
> I want to be able to make the checkbox convert the imperial < = > metric 
> correctly.
>
>
>
> Thanks
> John Dammeyer
>
> ___
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-- 

Chris Albertson
Redondo Beach, California


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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[andy pugh]

On Wed, 22 Jul 2020 at 19:33, Chris Albertson  wrote:

> That said acceleration is related to speed.   (acceleration) x (time) = 
> (speed)
> example:  (10 inch per second squared) x ( 0.5 seconds) = (5 inches per 
> second)

Also bear in mind that speed x acceleration x mass = power

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912


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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[Mark Wendt]

On Wed, Jul 22, 2020 at 2:33 PM Chris Albertson 
wrote:

>
> That said acceleration is related to speed.   (acceleration) x (time) =
> (speed)
> example:  (10 inch per second squared) x ( 0.5 seconds) = (5 inches per
> second)
>

That's true only if your initial velocity is zero.

Mark

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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[Chris Albertson]

> Also bear in mind that speed x acceleration x mass = power

That is actually informative here.  It shows that after you have
guessed and bought some motor that has some given power like say 1/2
HP or 400W or whatever, the power is now fixed.   Also, the mass of
the table is fixed.

So by the above equation, you see that the product of speed and
acceleration is fixed (for you machine or motor) but you can trade
speed for acceleration by changing the gear ratio or lead screw pitch.
You can choose to go twice as fast if you accept 1/2 the acceleration.
Or vice versa.

So if you like for acceleration to be 3X speed there is some gear
ratio or screw pitch the will do just that.

But so far we are only talking about jogs and ignoring cutting force


-- 

Chris Albertson
Redondo Beach, California


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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[Chris Albertson]

Yes, you technically correct.   I should have written

...acceleration is related to speed.   (acceleration) x (time) =
(change in speed)


On Wed, Jul 22, 2020 at 12:05 PM Mark Wendt  wrote:
>
> On Wed, Jul 22, 2020 at 2:33 PM Chris Albertson 
> wrote:
>
> >
> > That said acceleration is related to speed.   (acceleration) x (time) =
> > (speed)
> > example:  (10 inch per second squared) x ( 0.5 seconds) = (5 inches per
> > second)
> >
>
> That's true only if your initial velocity is zero.
>
> Mark
>
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-- 

Chris Albertson
Redondo Beach, California


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[Emc-users] Mesa 7i48 (and 7i71) needed

[Viesturs Lācis]

Hello!

I am in need of Mesa 7i48 board, preferably also 7i71 as well.
I need to retrofit Biesse CNC machine for a client and since I already
have done another Biesse machine for them previously, they would like
to make both setups identical just in case.
I got all the necessary boards from eusurplus.com, but they are out of
stock on 7i48 and also were one piece short on 7i71. They told me that
they have been unable to restock anything for some period of time,
because Mesa is affected by Covid.
I looked at duzi.cz, they have 7i48 (but are out of stock on 7i71),
but they cannot ship the board to my address due to unknown reasons.
They wrote to me to arrange a pickup, but do not respond to any emails
- I need details about the package - dimensions, weight, address of
pickup etc.
I also looked at http://www.shop.cncmonster.de/, but 7i48 is out of stock there.
I did not find any other online store in the EU from the international
dealers listed on Mesa website.
I can survive without 7i71 (but would like to get it as well, if possible).
So the question is - does anybody have recommendations, where can I
purchase them? I would prefer somewhere in the EU (due to tax reasons)
and would prefer to get an invoice to make a bank transfer from my
company account. But that is subject to change if I do not have
options. Maybe somebody has some spare cards and would agree to sell
them?
I would appreciate any suggestions.
Thanks in advance!

Viesturs


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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[Mark Wendt]

Yup, speed is distance/time, as long as a constant velocity is held.  Speed
is constantly increasing as long as your acceleration is constant.
Changing accelerations are a bit more complicated to deal with.

Mark

On Wed, Jul 22, 2020 at 3:13 PM Chris Albertson 
wrote:

> Yes, you technically correct.   I should have written
>
> ...acceleration is related to speed.   (acceleration) x (time) =
> (change in speed)
>
>
> On Wed, Jul 22, 2020 at 12:05 PM Mark Wendt  wrote:
> >
> > On Wed, Jul 22, 2020 at 2:33 PM Chris Albertson <
> albertson.ch...@gmail.com>
> > wrote:
> >
> > >
> > > That said acceleration is related to speed.   (acceleration) x (time) =
> > > (speed)
> > > example:  (10 inch per second squared) x ( 0.5 seconds) = (5 inches per
> > > second)
> > >
> >
> > That's true only if your initial velocity is zero.
> >
> > Mark
> >
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users
>
>
>
> --
>
> Chris Albertson
> Redondo Beach, California
>
>
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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[Peter C. Wallace]

On Wed, 22 Jul 2020, John Dammeyer wrote:


Date: Wed, 22 Jul 2020 09:06:38 -0700
From: John Dammeyer 
Reply-To: "Enhanced Machine Controller (EMC)"

To: "'Enhanced Machine Controller (EMC)'" 
Subject: [Emc-users] Calculating table acceleration. Was: Need help with
Bostomatic BD18-2 to linuxcnc

Ho Jon,

I've changed the subject line to be more relevant and corrected the gravity 
value.

Now we have 1703 In/Sec^2 for maximum possible acceleration given the load and 
torque ratings.


Is this including the ballscrew+motor inertia? this may be larger than the 
linear motions reflected inertia




On my system in imperial units I have 2.5 inches/second and I randomly picked 
the accel as 3x that.  Does that mean I could set MAX_ACCEL to say 1700 and 
get away with that or is that number abnormally high?  I know I can try it but 
I'd like to know if the math is accurate.



Probably not because of the drop in motor torque with speed as Sam mentioned
plus 1700 IPS/S and 2.5 IPS means full speed in about 1.5 ms. I doubt the bare 
step motor could do that...





MAX_VELOCITY = 2.5 MAX_ACCELERATION = 7.5 What I'm trying to do with this tool 
is to take out some of the guesswork or the accidental divide instead of 
multiply.


And second question. If someone is using metric units for their system what 
units are used to describe MAX_VELOCITY and ACCEL?
Is it mm/minute? Or mm/second?  Or meters/second?   Is the weight specified in 
grams or kg?

I want to be able to make the checkbox convert the imperial < = > metric 
correctly.



Thanks
John Dammeyer




Peter Wallace
Mesa Electronics



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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[John Dammeyer]

Hi Sam,
> From: Sam Sokolik [mailto:samco...@gmail.com]
> Is this stepper torque?  The peak torque is only at 0 rpm and drops off
> substantially as you increase rpm.  You  would need to look a the torque
> curve of the stepper and decide what top rpm you are looking for and
> calculate accordingly..

The discussion started with what sort of values and driver to install for a 
specific Servo.  Jon became involved because he sells servo drivers.  And then 
he made a mistake with scaling units and then I made a mistake with scaling 
units and it's really clear a tool to figure this out would be handy.  At least 
as a starting point and then tweaking the actual values still might be 
required.  

For example someone might not take apart their entire XY table assembly to 
weigh it to figure out how big a servo or stepper they need.  Mostly they will 
look at what's out there, listen to feedback and then decide.

My issue is the math still doesn't make sense.   If I try 1700in/Sec^2 the 
servo faults instantly.   MAX_ACCELERATION that works is about 40 in/sec^2 
without faults.  And Actually I run 20 for MAX_ACCELERATION and 
STEPGEN_MAXACCEL at 40 because I use backlash and it's supposed to be 100% 
larger.

So with Jon being the Servo designer I thought perhaps he could answer why 
there's such a large disparity.  Or is there still a math conversion problem 
here?

John



> 
> > Ho Jon,
> >
> > I've changed the subject line to be more relevant and corrected the
> > gravity value.
> >
> > Now we have 1703 In/Sec^2 for maximum possible acceleration given the load
> > and torque ratings.
> >
> > On my system in imperial units I have 2.5 inches/second and I randomly
> > picked the accel as 3x that.  Does that mean I could set MAX_ACCEL to say
> > 1700 and get away with that or is that number abnormally high?  I know I
> > can try it but I'd like to know if the math is accurate.
> >
> > MAX_VELOCITY = 2.5
> > MAX_ACCELERATION = 7.5
> > What I'm trying to do with this tool is to take out some of the guesswork
> > or the accidental divide instead of multiply.
> >
> > And second question. If someone is using metric units for their system
> > what units are used to describe MAX_VELOCITY and ACCEL?
> > Is it mm/minute? Or mm/second?  Or meters/second?   Is the weight
> > specified in grams or kg?
> >
> > I want to be able to make the checkbox convert the imperial < = > metric
> > correctly.
> >
> >
> >
> > Thanks
> > John Dammeyer
> >
> > ___
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> > https://lists.sourceforge.net/lists/listinfo/emc-users
> >
> 
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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[John Dammeyer]

> -Original Message-
> From: andy pugh [mailto:bodge...@gmail.com]
> 
> On Wed, 22 Jul 2020 at 19:33, Chris Albertson < 
>  albertson.ch...@gmail.com> wrote:
> 
> > That said acceleration is related to speed.   (acceleration) x (time) = 
> > (speed)
> > example:  (10 inch per second squared) x ( 0.5 seconds) = (5 inches per 
> > second)
> 
> Also bear in mind that speed x acceleration x mass = power
> 
> --
> atp
 
Let's take step back to the original question
 
One has a motor with a plate that says 3000 RPM, 226 oz-in, 7.8A continuous at 
90V.   The mill has a 5 TPI lead screw and a table that weighs 200 lbs.
 
So the questions that I think were asked or what the discussion was about was:
 
1. Can you run this table lead screw at 3000 RPM if the Servo Drive can handle 
7.8A at 90V.
2. If not what reduction ratio is required between motor and lead screw to run 
the motor at full speed.
 
Jon Elson provided the numbers for linear force created by the lead screw 
pitch. (with some guessing at friction) and the form I created and attached  
with 1:1 ratio shows 600 ipm and and 2.2G acceleration.
 

 
In real life I have the second screen shot with 3:1 belt reduction and as is 
logical, speed drops by 1/3, Torque is multiplied by 3 so Acceleration also 
increased by 3 to 6.66G.

 
If we divided 200 by 60 we get a speed of 3.33 in/sec which, if the 
LinuxCNC ini file has LINEAR=inches, is used for MAX_VELOCITY.  From the ini 
file documentation  
http://linuxcnc.org/docs/2.6/html/config/ini_config.html#sub:ini-variables
 
However the document also says "The maximum acceleration for any axis or 
coordinated axis move, in machine units per second per second."
 
There is no way that my motor can do 2556 in/sec^2.  In fact 40 is a more 
reasonable number. So we can do as Andy suggests and just get to it by trial 
and error.  But what's the point of any of this math if all we do is configure 
by mucking around until it sort of works.
 
So either Jon Elson is horribly wrong with the constant linear force 
calculation to determine force required to accelerate or something else is 
wrong.  I'm just trying to figure out how to calculate, knowing only the above 
parameters, what you'd plug into MAX_ACCELERATION as a starting point.  I 
realize it needs to be tweaked since ball screw verses acme screw makes a 
difference.  Static verses Kinetic friction makes a difference.
 
So is Jon's calculation of Continuous Linear force correct?  Something's 
missing but I can't put my finger on it.
John Dammeyer
 
 
 
 
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Re: [Emc-users] need a logic bit mux.

[Gene Heskett]

On Wednesday 22 July 2020 10:55:47 Jon Elson wrote:

> On 07/22/2020 01:17 AM, Gene Heskett wrote:
> > Greetings all;
> >
> > The launch of linuxcnc on the pi is without any motor power until
> > the F2 button is pushed.  So at launch time I get messages about the
> > z drive being tripped.
> >
> > So I need a 1 or 2 second delay before that bit is sent on thru, but
> > instant transmission once timed out, giving the driver a chance to
> > get all its stuff in one sock from the powerup enabled by the F2
> > key. I want to block any noise during the powerup surge.
>
> OK, so your drives indicate fault status when disabled?

No, it is not specifically disabled, in fact thats not even wired up in 
the drivers since the default is on. But the new 3 phase driver does 
have a fault output, and it is apparently closed during power up 
initialization.

I've assumed this output is similar to the others and I have its minus 
terminal grounded, and am watching its plus terminal with gpio.0061.in 
which will report true except when its tripped, or for a few 
milliseconds at powering up.

They are powred down by removing the electrical power src if linuxcnc 
isn't running, and then its running, the electrical power is only 
activated when f1 is released and f2 is enabled.  That is controlled by 
BIG SSR's driven by motion.motion-enabled. 

So I'm thinking a oneshot, started by motion.motion-enabled, generating a 
true to an or2 for long enough to cover this power up burp.  That 
oneshot and the or2 would have to be above it in the addf order, but 
below motion, so it would be effective when the message module and the 
rest it it looks.  That does sound like it would work.  I'll try it.

I made that work but lost the message, probably by removeing the signal, 
but now I have 2 more messages advising me I must be in joint mode or 
disabled before I can unhome, but it unhomes both axis's anyway!  And 
its all delayed until the next keypress because halui only runs when it 
feels like it.  Can that be fixed somehow? Never mind, a typu. Fixing 
that apparently got rid of the other 2 messages. And I have discovered 
that the motor shutdown allows it to bounce back 15 or 20 thou from the 
chuck jaw I am running into for testing.

So this problem can be marked as solved. See what the freezer has for 
dinner makeins next.  And since I can't eat chicken, take all the canned 
stuff with chicken up to the next door neighbors.  I bought it to feed 
the missus but shes now in a good sam home 50+ miles east of here.
> Yes, a lot of older drives (Copley, Westamp,
> Servo Dynamics) do this.  I made up a module with an
> optocoupler, a CMOS NAND gate and
> some RC delays to do this.  The servo amps usually take a 5
> V ENABLE/.  When the ENABLE/
> is high, the circuit closes the E-stop loop by turning the
> optocoupler on.  When ENABLE/ goes
> low, it continues to do this for about a second, then allows
> the servo amp's FAULT output to control the opto.
>
> Jon
>
>
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Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] mailing list for ender 3 pro owners?

[Chris Albertson]

I pretty much get the same results with my Anet A6. (the A6 id
actually a step up from the A8)  The ender is different from the A6/A8
in the Ender uses a bowden tube rather then a direct feed.  Ender
gains print speed with the lighter head but looses fine control of the
plastic feed.   But this is a small thing.

IMO rafts are a last resort when you can get bed adhesion to work.  If
you need them it means you have not year found a glue or hairspray or
tape that works for you.

I also agree that many people use high infill percentages that do
nothing but waste plastic.  For a large gear like a 180T, I'd even cut
out holes to make spokes.  With 3D printed parts all the strength
comes from the skin

Also don't forget that Cura allows different setting in different
parts of the part.  So the hub can be 60% infill and the web 15%
infill.   Things like this can save hours of print time.

On Fri, Jul 17, 2020 at 3:29 PM  wrote:
>
> On 2020-07-17 23:03, Gene Heskett wrote:
>   What I've found on the web seems to say that black
> > PLA needs more heat for normal stuff and even more for starter
> > adhesion.
> >
>
> I use a fair amount of black PLA+, and run my Anet A8 at 225 nozzle, 60
> bed. I have found some variation in temperature for different colours,
> but nothing that would cause problems here (black, white, red, blue).
> Note this is PLA+ rather than straight PLA, but other users I talk to
> seem to have success with PLA and pretty much the same temperatures.
> I gave up on rafts: too much cleaning up after the print has finished. I
> use a glass bed (attached with crocodile clips) and lay down a coat of
> strong PVA glue, mixed 3 parts glue to 1 part water. Then I use a brim,
> one layer high. Works a treat. In fact it takes a bit of knocking to get
> it off the glass (run it under hot water, and swipe the brim layer with
> a large kitchen knife. The same glue works just fine with the aluminium
> plate bed.
>
> The Anet is basically the same as the Ender, but cheaper (and probably
> not as refined).
> My nozzle is 0.1mm (4 thou) off the bed at Home.
>
> Large prints can take a long time, but I notice that a low infill
> percentage still provides decent strength for most jobs, and speeds
> things up. I usually print at 0.2mm layer height, unless I need fine
> detail. That keeps run times a little shorter.
>
> Other users report that the best prints seem to occur when the ambient
> temperature in the room is high. I print in a cold room (big garage),
> but PLA doesn't seem to mind. I think ABS would.
>
> Marcus
>
>
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-- 

Chris Albertson
Redondo Beach, California


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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[John Dammeyer]

I have to get back to other projects for a while.  I've disabled the metric 
checkbox and made it invisible since the conversion to metric and back isn't 
complete yet.  And since the value to use for MAX_ACCELERATION in the INI file 
is suspect perhaps the whole project is a joke.

I've attached the zip with the Lazarus Source Code.  I've compiled and run this 
on a PC with Windows, BeagleBone and Raspberry Pi.  If you are running Linux 
sudo apt install lazarus 
should be enough.

My first attempt at putting something on GitHub.
https://github.com/jcdammeyer/LinuxCNC

John Dammeyer


> -Original Message-
> From: John Dammeyer [mailto:jo...@autoartisans.com]
> Sent: July-22-20 12:53 PM
> To: 'Enhanced Machine Controller (EMC)'
> Subject: Re: [Emc-users] Calculating table acceleration. Was: Need help with 
> Bostomatic BD18-2 to linuxcnc
> 
> > -Original Message-
> > From: andy pugh [mailto:bodge...@gmail.com]
> >
> > On Wed, 22 Jul 2020 at 19:33, Chris Albertson < 
> >  albertson.ch...@gmail.com> wrote:
> >
> > > That said acceleration is related to speed.   (acceleration) x (time) = 
> > > (speed)
> > > example:  (10 inch per second squared) x ( 0.5 seconds) = (5 inches per 
> > > second)
> >
> > Also bear in mind that speed x acceleration x mass = power
> >
> > --
> > atp
> 
> Let's take step back to the original question
> 
> One has a motor with a plate that says 3000 RPM, 226 oz-in, 7.8A continuous 
> at 90V.   The mill has a 5 TPI lead screw and a table that
> weighs 200 lbs.
> 
> So the questions that I think were asked or what the discussion was about was:
> 
> 1. Can you run this table lead screw at 3000 RPM if the Servo Drive can 
> handle 7.8A at 90V.
> 2. If not what reduction ratio is required between motor and lead screw to 
> run the motor at full speed.
> 
> Jon Elson provided the numbers for linear force created by the lead screw 
> pitch. (with some guessing at friction) and the form I
> created and attached  with 1:1 ratio shows 600 ipm and and 2.2G acceleration.
> 
> 
> 
> In real life I have the second screen shot with 3:1 belt reduction and as is 
> logical, speed drops by 1/3, Torque is multiplied by 3 so
> Acceleration also increased by 3 to 6.66G.
> 
> 
> If we divided 200 by 60 we get a speed of 3.33 in/sec which, if the 
> LinuxCNC ini file has LINEAR=inches, is used for
> MAX_VELOCITY.  From the ini file documentation  
> http://linuxcnc.org/docs/2.6/html/config/ini_config.html#sub:ini-variables
> 
> However the document also says "The maximum acceleration for any axis or 
> coordinated axis move, in machine units per second
> per second."
> 
> There is no way that my motor can do 2556 in/sec^2.  In fact 40 is a more 
> reasonable number. So we can do as Andy suggests and
> just get to it by trial and error.  But what's the point of any of this math 
> if all we do is configure by mucking around until it sort of
> works.
> 
> So either Jon Elson is horribly wrong with the constant linear force 
> calculation to determine force required to accelerate or
> something else is wrong.  I'm just trying to figure out how to calculate, 
> knowing only the above parameters, what you'd plug into
> MAX_ACCELERATION as a starting point.  I realize it needs to be tweaked since 
> ball screw verses acme screw makes a difference.
> Static verses Kinetic friction makes a difference.
> 
> So is Jon's calculation of Continuous Linear force correct?  Something's 
> missing but I can't put my finger on it.
> John Dammeyer
> 
> 
> 
> 



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[Emc-users] wondering what the status is on S curve jerk control getting added into linuxcnc

[andrew beck]

hey guys

I have a relatively high speed machine (3kw motors 16mm pitch ballscrews)
 35mm linear rails, and weights 5.8 ton.  I think it used to go 20m/min
with the heidenhain control.  I have been noticing a bit of jumping around
when doing parallel finishing 3d passed on it at high speed.  and talked to
a couple of linuxcnc guys and found out that linuxcnc doesn't have any jerk
control.  just sending out a email here seeing what the current progress is
on that.

at high speed high precision linuxcnc definitely needs some work at some
stage.

apart from this I am completely happy with linuxcnc.  this would be a nice
thing to solve though.  and if someone with the right skills wanted to fix
it I would be happy as to chip in to pay something for the time.  as I run
a business in my machine shop where everything runs linuxcnc

in the mean time I will try to get around the issue by programming in cam

regards

Andrew

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Re: [Emc-users] wondering what the status is on S curve jerk control getting added into linuxcnc

[Nicklas SB Karlsson]

> hey guys
> 
> I have a relatively high speed machine (3kw motors 16mm pitch ballscrews)
>  35mm linear rails, and weights 5.8 ton.  I think it used to go 20m/min
> with the heidenhain control.  I have been noticing a bit of jumping around
> when doing parallel finishing 3d passed on it at high speed.  and talked to
> a couple of linuxcnc guys and found out that linuxcnc doesn't have any jerk
> control.  ...

If I get it correct from electric motor equations it like this: Jerk could be 
controlled instantly. Available jerk in direction to increase speed decrease 
with speed while available jerk to decrease speed increase with speed and this 
is because of induced back-emf. I assumed a given constant magnetic flux inside 
motor otherwise decrease magnetic flux which may be possible in some cases will 
decrease back-emf and torque and may allow higher speed if voltage is a 
limitation, there is an optimal flux for best efficiency. Even though control 
algorithm is different it should apply for the common electric motors: DC, 
BLDC, PMSM 3-phase synchron motor, synchronous reluctance motor and ordinary 
3-phase asynchronous induction motor.

Not sure how good motion planner is. Read something about a PhD degree but are 
not sure it was for the motion planner in Linuxcnc.

I wrote simpler motion controller, one axis with jerk limitation and had to 
spend quite much time make the corners fit perfectly at the same time it 
followed the limitation and hit target.

> at high speed high precision linuxcnc definitely needs some work at some
> stage.

Improvements are of course always good. Maybe, but if high speed is used then 
moving thru air "G0 move" or rectracting while speed is lower then machining 
thru part lower precision is acceptable at higher speed. Integrator need som 
time to decrease error so it might be hard work to get both at once.


Regards Nicklas SB Karlsson


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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[Nicklas SB Karlsson]

On Wed, 22 Jul 2020 11:29:36 -0700
Chris Albertson  wrote:

> I don't see any relation between max acceleration and max speed.
> Acceleration is determined by (1) the mass of the table and (2) the
> torque the motor can produce while speed is determined by the max RPM
> of the motor.

Mostly agree though as torque usually depend mostly on current there will be a 
resistive voltage drop at higher torque which will reduce speed at higher 
torque, speed reduction is usually small. For example series connected DC 
motors and induction motors made for direct will reduce speed so there are 
exceptions but do not expect these are used as servo motors anyway.

Change gear ratio and use motor with same power different speed may change 
acceleration due to rotor inertia.

> It is very easy to buy a tiny motor with low torque that spins very
> fast.  Or you can find powerful but slow motors.   Multiplying the
> speed by three to find acceleration, if it works is just a
> coincidence.  The factor could be 0.5 or 10.

High torque motors usually need a gear box or will become heavy. This is 
because flux and current is multiplied to get force while there is choice 
between current or flux in electric motor air gap, there is an optimal choice 
then either air gap area or diameter need to be increased. Magnetic materials 
will saturate then flux get high enough while conductor losses increase with 
current.

> There are two whys to go.  A mechanical engineer would start with a
> requirement for a certain speed and a certain acceleration.  His boss
> would give him those goals and then he would select a motor and drive.
>   The other way used by most amateurs is to just buy a motor that
> "seems right" and then test it to see what speed and a certain
> acceleration you can get from it.

Not sure the boss will ask mechanical engineer about speed and a certain 
acceleration and then give these as a goal to the engineer. It is common boss 
read economics and contract but then it come to technical details odd things 
may happen.


Nicklas SB Karlsson


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Re: [Emc-users] Just took the first flexgear off the printer

[Chris Albertson]

There are 100 tricks.   One is to "cut" the part with a flat plane.
Then print the two halves cut-side down with no support then glue them
together.   If you think, sometimes you can find a good place to cut
that actually makes the part stronger because the joined halves have a
double-thick internal skin.Use the cut plane as a shear-wall.

If you know woodworking then think of joinery and print flat parts
then fits like furniture or cabinets and add some CA glue.Like
wood, the grain ends up going in the long direction and the part is
stronger and also easier to print.

there are endless ways to avoid supports.   Or just put up with it.

On Wed, Jul 22, 2020 at 1:34 AM andy pugh  wrote:
>
> On Wed, 22 Jul 2020 at 06:17, Gene Heskett  wrote:
>
> > And had a hell of a time removing the internal supports, which probably
> > out-weigh the gear
>
> Perhaps you would have been better printing it the other way round?
>
> I think I recall seeing someone use pause-at-height to apply an
> anti-adhesion material  to the support, but can't remember where I saw
> it, or what he used.
>
> --
> atp
> "A motorcycle is a bicycle with a pandemonium attachment and is
> designed for the especial use of mechanical geniuses, daredevils and
> lunatics."
> — George Fitch, Atlanta Constitution Newspaper, 1912
>
>
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-- 

Chris Albertson
Redondo Beach, California


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Re: [Emc-users] Just took the first flexgear off the printer

[Gene Heskett]

On Wednesday 22 July 2020 19:04:00 Chris Albertson wrote:

> There are 100 tricks.   One is to "cut" the part with a flat plane.
> Then print the two halves cut-side down with no support then glue them
> together.   If you think, sometimes you can find a good place to cut
> that actually makes the part stronger because the joined halves have a
> double-thick internal skin.Use the cut plane as a shear-wall.
>
> If you know woodworking then think of joinery and print flat parts
> then fits like furniture or cabinets and add some CA glue.Like
> wood, the grain ends up going in the long direction and the part is
> stronger and also easier to print.
>
> there are endless ways to avoid supports.   Or just put up with it.
>
I got it figured out how to break it out in one piece in about 10 
minutes. 3rd one is 10mm deep on the build plate allready. :)

> On Wed, Jul 22, 2020 at 1:34 AM andy pugh  wrote:
> > On Wed, 22 Jul 2020 at 06:17, Gene Heskett  
wrote:
> > > And had a hell of a time removing the internal supports, which
> > > probably out-weigh the gear
> >
> > Perhaps you would have been better printing it the other way round?
> >
> > I think I recall seeing someone use pause-at-height to apply an
> > anti-adhesion material  to the support, but can't remember where I
> > saw it, or what he used.
> >
> > --
> > atp
> > "A motorcycle is a bicycle with a pandemonium attachment and is
> > designed for the especial use of mechanical geniuses, daredevils and
> > lunatics."
> > — George Fitch, Atlanta Constitution Newspaper, 1912
> >
> >
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users


Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] Problem with Rigid Tapping on USC Equipped Bridgeport

[Matthew Herd]

I got the braking resistor installed, fiddled with all the DC injection braking 
and dynamic braking parameters on the machine, then started turning down the 
deceleration time.  It looks like I only tuned the acceleration time when I 
originally installed the VFD because it was set to the default 10 seconds.  I 
turned it down to 0.6 seconds and tested a reversal of direction up to 1000 
RPM.  Worked great.  Also, since the mechanical brake kicks in automatically 
when stopping, the drive doesn’t fault out even when the varispeed head is set 
to max RPM.  I can’t imagine I’ll need to tap at 1000 RPM, but I estimated that 
1000 RPM to 0 RPM in 0.6 seconds should be approximately equal to 10 
revolutions (assuming a linear deceleration).  I didn’t bother to push it 
further.  No idea how much the braking resistor helps, but it certainly doesn’t 
hurt.

Upon testing, I found that rigid tapping worked as intended, aside from one 
glitch on the first attempt after powering up where it hung in the down 
position and running in reverse.  Not sure of the cause there, but I wasn’t 
able to reproduce the error.  In practice, 560 RPM resulted in an overshoot 
equal to a bit under 3 revolutions.  I figure if I allow 5 revolutions of 
margin to the bottom of the hole, I should be fine.  I tested it repeatedly, 
including running a program tapping two holes in delrin.  Thank you all for 
your help.  I’ll run it a few more times before declaring it solved, but so far 
so good!

As to configuring speed control of the VFD, that’s for another day.  I plan to 
do it eventually, but for now I’m thrilled I didn’t need to resort to more 
sophisticated fixes.  I’m fine with manually setting my speed.

> On Jul 21, 2020, at 8:26 PM, Gene Heskett  wrote:
> 
> On Tuesday 21 July 2020 18:40:35 Scott Harwell via Emc-users wrote:
> 
>> Just got my new Control Engineering in the mail and saw this."Top 5
>> VFD parameter changes explained"
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> Top 5 VFD parameter changes explained
>> 
>> Chris Vavra
>> 
>> Learning Objectives Setting five parameters can take care of most VFD
>> programming. Consider VFD control met...
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> "www.controleng.com/articles/top-5-vfd-parameter-changes-explained/"
>> It may help.
>> Scott
>> 
>>On Tuesday, July 21, 2020, 12:17:05 PM CDT, Matthew Herd
>>  wrote:
>> 
>> Hi Rob,
>> 
>> Thanks for the insights.  I suspected something along these lines,
>> even if I might have other problems with noise.  I can confirm, the
>> spindle stops way too slowly and definitely more than 10 revolutions
>> pass before stopping.  Long story short, I can’t readily run the
>> machine in back gear and the slowest I can go at 60Hz is 560 RPM
>> without backgear.
> 
> But if you get the right control signal setup, you can drive that vfd at 
> 5 hertz! I am doing it. And I can do it for an hour at a time without 
> heating the motor so hot I can't touch it. All you need is to find the 
> register that sets the motors FLA, and transfer the FLA from the motors 
> nameplate to that register. That way you are assured that the motor 
> won't be quickly overheated and burned up at even very low speeds.  You 
> may also have to locate the register that sets the minimum run speed as 
> its likely set to faster than that, possibly even turning itself off at 
> 30 hertz or more.  There are registers also to control how fast it 
> accels or decels.  The biggest problem is in translating the Chinglish 
> in the booklets into your local dialect that you understand.
> 
> One thing I've found is that most vfd's are directly controllable by a
> 12 volt swing from a pwm generator, running the pwm at 10 kilohertz.  The 
> vfd's response averages that into an analog signal equivalent, so a 10% 
> duty cycle pwm will run the vfd at say 12 hertz.  And I've some extra 
> stuff in my .hal to measure the overshoot so I'll demo, live, right now. 
> From 200 rpms, entering an m4 to reverse it, gets me a display of 1.0333 
> revs that it overshot, or just a small hair over 1 full turn from 200 
> revs. This is an E400 drive, running in 1st gear, and it has an 8" 4 jaw 
> chuck that weighs just short of 40 lbs mounted. This particular vfd is 
> controlled by a Mesa SpinX1 which has its own analog 0-10 volt output.
> 
> Your B-Port doesn't have near that amount of flywheel, and it ought to 
> beat that time while spinning at 400 rpms.
> 
>> I’ll play a bit more with how quickly I can stop 
>> the spindle with a braking resistor or I’ll attempt to get the HAL
>> file to engage the mechanical brake to help transition faster. 
>> Nonetheless, 10 revolutions seems fairly ambitious based on my best
>> guess of how long it might take to stop the spindle even with a
>> braking resistor.That’s about 1 second, but should be achievable. 
>> Currently the VFD is configured based on the fastest stop time for max
>> RPM, and there doesn’t seem to be a way to decrease stop time for
>> different in

Re: [Emc-users] Problem with Rigid Tapping on USC Equipped Bridgeport

[Jon Elson]

On 07/22/2020 08:51 PM, Matthew Herd wrote:


Upon testing, I found that rigid tapping worked as intended,

Excellent.  Glad Robert Ellenberg is watching here, as most 
of us had no idea the trajectory planner had this behavior.


I love rigid tapping, and have made two fixture plates with 
a 1" grid of 10-32 holes.  Also, my PWM servo amps have 12 
or 14 4-40 tapped holes in each mounting plate.  I also did 
some brackets for circuit boards that have a bunch of 2-56 
holes.  Those make me bit my lip just a little.


The neatest thing is combo drill-taps, they have a twist 
drill front end and a tap further back.
You drill through sheet material at a low feedrate, then 
back up a bit and do G33.1 to tap

the hole, all with one tool.

Jon


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[Emc-users] Little gear I'm cutting. Thought it may interest people.

[andrew beck]

Hey everyone just a quick video here.  Might interest people.

https://youtu.be/3u1bZxd-KCk

Regards

Andrew

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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[Thaddeus Waldner]

Start with a 226 oz in

/ 16 = 14.125 lb in

5 threads per inch is the same as a belt pulley with a circumference of 0.2
inches

since our unit is in lb in, we need to go from a pulley with diameter of
Pi, to diameter of .2

thus our final force is 14.125 * (pi/0.2) = 221.875 pounds (poundal?) force

divide that by your mass of 200lb and you get

1.109 g

1g = roughly 32in/s^2 so

35.69 in/s^2

This is close to your ballpark guess of 40

Did I make a mistake anywhere?




On Wed, Jul 22, 2020 at 5:24 PM Nicklas SB Karlsson <
nicklas.karlsso...@gmail.com> wrote:

> On Wed, 22 Jul 2020 11:29:36 -0700
> Chris Albertson  wrote:
>
> > I don't see any relation between max acceleration and max speed.
> > Acceleration is determined by (1) the mass of the table and (2) the
> > torque the motor can produce while speed is determined by the max RPM
> > of the motor.
>
> Mostly agree though as torque usually depend mostly on current there will
> be a resistive voltage drop at higher torque which will reduce speed at
> higher torque, speed reduction is usually small. For example series
> connected DC motors and induction motors made for direct will reduce speed
> so there are exceptions but do not expect these are used as servo motors
> anyway.
>
> Change gear ratio and use motor with same power different speed may change
> acceleration due to rotor inertia.
>
> > It is very easy to buy a tiny motor with low torque that spins very
> > fast.  Or you can find powerful but slow motors.   Multiplying the
> > speed by three to find acceleration, if it works is just a
> > coincidence.  The factor could be 0.5 or 10.
>
> High torque motors usually need a gear box or will become heavy. This is
> because flux and current is multiplied to get force while there is choice
> between current or flux in electric motor air gap, there is an optimal
> choice then either air gap area or diameter need to be increased. Magnetic
> materials will saturate then flux get high enough while conductor losses
> increase with current.
>
> > There are two whys to go.  A mechanical engineer would start with a
> > requirement for a certain speed and a certain acceleration.  His boss
> > would give him those goals and then he would select a motor and drive.
> >   The other way used by most amateurs is to just buy a motor that
> > "seems right" and then test it to see what speed and a certain
> > acceleration you can get from it.
>
> Not sure the boss will ask mechanical engineer about speed and a certain
> acceleration and then give these as a goal to the engineer. It is common
> boss read economics and contract but then it come to technical details odd
> things may happen.
>
>
> Nicklas SB Karlsson
>
>
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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[Thaddeus Waldner]

Ah yes

In lb is radius, so the ballscrew factor is 2pi*threads per inch

Which would double the acceleration from my earlier numbers.


> On Jul 22, 2020, at 10:43 PM, Thaddeus Waldner  wrote:
> 
> 
> 
> 
> Start with a 226 oz in
> 
> / 16 = 14.125 lb in
> 
> 5 threads per inch is the same as a belt pulley with a circumference of 0.2 
> inches
> 
> since our unit is in lb in, we need to go from a pulley with diameter of Pi, 
> to diameter of .2
> 
> thus our final force is 14.125 * (pi/0.2) = 221.875 pounds (poundal?) force
> 
> divide that by your mass of 200lb and you get  
> 
> 1.109 g
> 
> 1g = roughly 32in/s^2 so 
> 
> 35.69 in/s^2
> 
> This is close to your ballpark guess of 40
> 
> Did I make a mistake anywhere?
> 
> 
> 
> 
>> On Wed, Jul 22, 2020 at 5:24 PM Nicklas SB Karlsson 
>>  wrote:
>> On Wed, 22 Jul 2020 11:29:36 -0700
>> Chris Albertson  wrote:
>> 
>> > I don't see any relation between max acceleration and max speed.
>> > Acceleration is determined by (1) the mass of the table and (2) the
>> > torque the motor can produce while speed is determined by the max RPM
>> > of the motor.
>> 
>> Mostly agree though as torque usually depend mostly on current there will be 
>> a resistive voltage drop at higher torque which will reduce speed at higher 
>> torque, speed reduction is usually small. For example series connected DC 
>> motors and induction motors made for direct will reduce speed so there are 
>> exceptions but do not expect these are used as servo motors anyway.
>> 
>> Change gear ratio and use motor with same power different speed may change 
>> acceleration due to rotor inertia.
>> 
>> > It is very easy to buy a tiny motor with low torque that spins very
>> > fast.  Or you can find powerful but slow motors.   Multiplying the
>> > speed by three to find acceleration, if it works is just a
>> > coincidence.  The factor could be 0.5 or 10.
>> 
>> High torque motors usually need a gear box or will become heavy. This is 
>> because flux and current is multiplied to get force while there is choice 
>> between current or flux in electric motor air gap, there is an optimal 
>> choice then either air gap area or diameter need to be increased. Magnetic 
>> materials will saturate then flux get high enough while conductor losses 
>> increase with current.
>> 
>> > There are two whys to go.  A mechanical engineer would start with a
>> > requirement for a certain speed and a certain acceleration.  His boss
>> > would give him those goals and then he would select a motor and drive.
>> >   The other way used by most amateurs is to just buy a motor that
>> > "seems right" and then test it to see what speed and a certain
>> > acceleration you can get from it.
>> 
>> Not sure the boss will ask mechanical engineer about speed and a certain 
>> acceleration and then give these as a goal to the engineer. It is common 
>> boss read economics and contract but then it come to technical details odd 
>> things may happen.
>> 
>> 
>> Nicklas SB Karlsson
>> 
>> 
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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[Bruce Layne]

On 7/22/20 11:43 PM, Thaddeus Waldner wrote:
> 1g = roughly 32in/s^2

1 g is 32 ft/sec^2

Feet, not inches.



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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[John Dammeyer]

> -Original Message-
> From: Thaddeus Waldner [mailto:thadw...@gmail.com]
> Sent: July-22-20 8:43 PM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] Calculating table acceleration. Was: Need help with 
> Bostomatic BD18-2 to linuxcnc
> 
> Start with a 226 oz in
> 
> / 16 = 14.125 lb in
> 
> 5 threads per inch is the same as a belt pulley with a circumference of 0.2
> inches
> 
> since our unit is in lb in, we need to go from a pulley with diameter of
> Pi, to diameter of .2
> 
> thus our final force is 14.125 * (pi/0.2) = 221.875 pounds (poundal?) force
> 
> divide that by your mass of 200lb and you get
> 
> 1.109 g
> 
> 1g = roughly 32in/s^2 so
> 
> 35.69 in/s^2
> 
> This is close to your ballpark guess of 40
> 
> Did I make a mistake anywhere?
> 

1 G is 32 ft/sec^2 or 384 in/sec^2 and that's where it falls apart.  Based on 
real life the acceleration value is out by a factor of about 100.

And I don't understand why
" since our unit is in lb in, we need to go from a pulley with diameter of  Pi, 
to diameter of .2"

It could well be that Jon Elson's explanation of linear force is incorrect.  

John


> 
> 
> On Wed, Jul 22, 2020 at 5:24 PM Nicklas SB Karlsson <
> nicklas.karlsso...@gmail.com> wrote:
> 
> > On Wed, 22 Jul 2020 11:29:36 -0700
> > Chris Albertson  wrote:
> >
> > > I don't see any relation between max acceleration and max speed.
> > > Acceleration is determined by (1) the mass of the table and (2) the
> > > torque the motor can produce while speed is determined by the max RPM
> > > of the motor.
> >
> > Mostly agree though as torque usually depend mostly on current there will
> > be a resistive voltage drop at higher torque which will reduce speed at
> > higher torque, speed reduction is usually small. For example series
> > connected DC motors and induction motors made for direct will reduce speed
> > so there are exceptions but do not expect these are used as servo motors
> > anyway.
> >
> > Change gear ratio and use motor with same power different speed may change
> > acceleration due to rotor inertia.
> >
> > > It is very easy to buy a tiny motor with low torque that spins very
> > > fast.  Or you can find powerful but slow motors.   Multiplying the
> > > speed by three to find acceleration, if it works is just a
> > > coincidence.  The factor could be 0.5 or 10.
> >
> > High torque motors usually need a gear box or will become heavy. This is
> > because flux and current is multiplied to get force while there is choice
> > between current or flux in electric motor air gap, there is an optimal
> > choice then either air gap area or diameter need to be increased. Magnetic
> > materials will saturate then flux get high enough while conductor losses
> > increase with current.
> >
> > > There are two whys to go.  A mechanical engineer would start with a
> > > requirement for a certain speed and a certain acceleration.  His boss
> > > would give him those goals and then he would select a motor and drive.
> > >   The other way used by most amateurs is to just buy a motor that
> > > "seems right" and then test it to see what speed and a certain
> > > acceleration you can get from it.
> >
> > Not sure the boss will ask mechanical engineer about speed and a certain
> > acceleration and then give these as a goal to the engineer. It is common
> > boss read economics and contract but then it come to technical details odd
> > things may happen.
> >
> >
> > Nicklas SB Karlsson
> >
> >
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users
> >
> 
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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[Bari]

On 7/22/20 11:04 PM, Bruce Layne wrote:


On 7/22/20 11:43 PM, Thaddeus Waldner wrote:

1g = roughly 32in/s^2

1 g is 32 ft/sec^2

Feet, not inches.



Comparing Standard Gravity to Other Acceleration Units

Standard Gravity    1 G's
Meters per Second per Second    9.81
Feet per Second per Second    32.174
Inches per Second per Second    386.09


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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[John Dammeyer]

BTW, it looks like the numbers that Jon came up with match with this site.  
I've used their motors.  Nice stuff.
https://www.kollmorgen.com/en-us/developer-network/calculating-linear-force-and-torque-ballscrew/

Using the 
F2 = T x 2 x PI / L

I get the exact same value in oz-in and when converted to lbs matches my 
program.

But as yet I've not figured out how to turn that into a LinuxCNC 
MAX_ACCELERATION value that is useful.

John


> -Original Message-
> From: John Dammeyer [mailto:jo...@autoartisans.com]
> Sent: July-22-20 9:05 PM
> To: 'Enhanced Machine Controller (EMC)'
> Subject: Re: [Emc-users] Calculating table acceleration. Was: Need help with 
> Bostomatic BD18-2 to linuxcnc
> 
> 
> > -Original Message-
> > From: Thaddeus Waldner [mailto:thadw...@gmail.com]
> > Sent: July-22-20 8:43 PM
> > To: Enhanced Machine Controller (EMC)
> > Subject: Re: [Emc-users] Calculating table acceleration. Was: Need help 
> > with Bostomatic BD18-2 to linuxcnc
> >
> > Start with a 226 oz in
> >
> > / 16 = 14.125 lb in
> >
> > 5 threads per inch is the same as a belt pulley with a circumference of 0.2
> > inches
> >
> > since our unit is in lb in, we need to go from a pulley with diameter of
> > Pi, to diameter of .2
> >
> > thus our final force is 14.125 * (pi/0.2) = 221.875 pounds (poundal?) force
> >
> > divide that by your mass of 200lb and you get
> >
> > 1.109 g
> >
> > 1g = roughly 32in/s^2 so
> >
> > 35.69 in/s^2
> >
> > This is close to your ballpark guess of 40
> >
> > Did I make a mistake anywhere?
> >
> 
> 1 G is 32 ft/sec^2 or 384 in/sec^2 and that's where it falls apart.  Based on 
> real life the acceleration value is out by a factor of about
> 100.
> 
> And I don't understand why
> " since our unit is in lb in, we need to go from a pulley with diameter of  
> Pi, to diameter of .2"
> 
> It could well be that Jon Elson's explanation of linear force is incorrect.
> 
> John
> 
> 
> >
> >
> > On Wed, Jul 22, 2020 at 5:24 PM Nicklas SB Karlsson <
> > nicklas.karlsso...@gmail.com> wrote:
> >
> > > On Wed, 22 Jul 2020 11:29:36 -0700
> > > Chris Albertson  wrote:
> > >
> > > > I don't see any relation between max acceleration and max speed.
> > > > Acceleration is determined by (1) the mass of the table and (2) the
> > > > torque the motor can produce while speed is determined by the max RPM
> > > > of the motor.
> > >
> > > Mostly agree though as torque usually depend mostly on current there will
> > > be a resistive voltage drop at higher torque which will reduce speed at
> > > higher torque, speed reduction is usually small. For example series
> > > connected DC motors and induction motors made for direct will reduce speed
> > > so there are exceptions but do not expect these are used as servo motors
> > > anyway.
> > >
> > > Change gear ratio and use motor with same power different speed may change
> > > acceleration due to rotor inertia.
> > >
> > > > It is very easy to buy a tiny motor with low torque that spins very
> > > > fast.  Or you can find powerful but slow motors.   Multiplying the
> > > > speed by three to find acceleration, if it works is just a
> > > > coincidence.  The factor could be 0.5 or 10.
> > >
> > > High torque motors usually need a gear box or will become heavy. This is
> > > because flux and current is multiplied to get force while there is choice
> > > between current or flux in electric motor air gap, there is an optimal
> > > choice then either air gap area or diameter need to be increased. Magnetic
> > > materials will saturate then flux get high enough while conductor losses
> > > increase with current.
> > >
> > > > There are two whys to go.  A mechanical engineer would start with a
> > > > requirement for a certain speed and a certain acceleration.  His boss
> > > > would give him those goals and then he would select a motor and drive.
> > > >   The other way used by most amateurs is to just buy a motor that
> > > > "seems right" and then test it to see what speed and a certain
> > > > acceleration you can get from it.
> > >
> > > Not sure the boss will ask mechanical engineer about speed and a certain
> > > acceleration and then give these as a goal to the engineer. It is common
> > > boss read economics and contract but then it come to technical details odd
> > > things may happen.
> > >
> > >
> > > Nicklas SB Karlsson
> > >
> > >
> > > ___
> > > Emc-users mailing list
> > > Emc-users@lists.sourceforge.net
> > > https://lists.sourceforge.net/lists/listinfo/emc-users
> > >
> >
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> 
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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[Thaddeus Waldner]

Yes!  Thank you. 


> On Jul 22, 2020, at 11:07 PM, John Dammeyer  wrote:
> 
> 
>> -Original Message-
>> From: Thaddeus Waldner [mailto:thadw...@gmail.com]
>> Sent: July-22-20 8:43 PM
>> To: Enhanced Machine Controller (EMC)
>> Subject: Re: [Emc-users] Calculating table acceleration. Was: Need help with 
>> Bostomatic BD18-2 to linuxcnc
>> 
>> Start with a 226 oz in
>> 
>> / 16 = 14.125 lb in
>> 
>> 5 threads per inch is the same as a belt pulley with a circumference of 0.2
>> inches
>> 
>> since our unit is in lb in, we need to go from a pulley with diameter of
>> Pi, to diameter of .2
>> 
>> thus our final force is 14.125 * (pi/0.2) = 221.875 pounds (poundal?) force
>> 
>> divide that by your mass of 200lb and you get
>> 
>> 1.109 g
>> 
>> 1g = roughly 32in/s^2 so
>> 
>> 35.69 in/s^2
>> 
>> This is close to your ballpark guess of 40
>> 
>> Did I make a mistake anywhere?
>> 
> 
> 1 G is 32 ft/sec^2 or 384 in/sec^2 and that's where it falls apart.  Based on 
> real life the acceleration value is out by a factor of about 100.
> 
> And I don't understand why
> " since our unit is in lb in, we need to go from a pulley with diameter of  
> Pi, to diameter of .2"
> 
> It could well be that Jon Elson's explanation of linear force is incorrect.  
> 
> John
> 
> 
>> 
>> 
>>> On Wed, Jul 22, 2020 at 5:24 PM Nicklas SB Karlsson <
>>> nicklas.karlsso...@gmail.com> wrote:
>>> 
>>> On Wed, 22 Jul 2020 11:29:36 -0700
>>> Chris Albertson  wrote:
>>> 
 I don't see any relation between max acceleration and max speed.
 Acceleration is determined by (1) the mass of the table and (2) the
 torque the motor can produce while speed is determined by the max RPM
 of the motor.
>>> 
>>> Mostly agree though as torque usually depend mostly on current there will
>>> be a resistive voltage drop at higher torque which will reduce speed at
>>> higher torque, speed reduction is usually small. For example series
>>> connected DC motors and induction motors made for direct will reduce speed
>>> so there are exceptions but do not expect these are used as servo motors
>>> anyway.
>>> 
>>> Change gear ratio and use motor with same power different speed may change
>>> acceleration due to rotor inertia.
>>> 
 It is very easy to buy a tiny motor with low torque that spins very
 fast.  Or you can find powerful but slow motors.   Multiplying the
 speed by three to find acceleration, if it works is just a
 coincidence.  The factor could be 0.5 or 10.
>>> 
>>> High torque motors usually need a gear box or will become heavy. This is
>>> because flux and current is multiplied to get force while there is choice
>>> between current or flux in electric motor air gap, there is an optimal
>>> choice then either air gap area or diameter need to be increased. Magnetic
>>> materials will saturate then flux get high enough while conductor losses
>>> increase with current.
>>> 
 There are two whys to go.  A mechanical engineer would start with a
 requirement for a certain speed and a certain acceleration.  His boss
 would give him those goals and then he would select a motor and drive.
  The other way used by most amateurs is to just buy a motor that
 "seems right" and then test it to see what speed and a certain
 acceleration you can get from it.
>>> 
>>> Not sure the boss will ask mechanical engineer about speed and a certain
>>> acceleration and then give these as a goal to the engineer. It is common
>>> boss read economics and contract but then it come to technical details odd
>>> things may happen.
>>> 
>>> 
>>> Nicklas SB Karlsson
>>> 
>>> 
>>> ___
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>>> Emc-users@lists.sourceforge.net
>>> https://lists.sourceforge.net/lists/listinfo/emc-users
>>> 
>> 
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> 
> 
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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[John Dammeyer]

I've asked a retired physics professor friend for some enlightenment. 
 
Jon Elson has stated that with T = r x Fsin(theta) and  F=ma that the 
acceleration is Gravity because it's equivalent to dropping the X axis table 
and letting the earth accelerate it.
 
But F=mg is the force due to gravity.  I might well be that since we're dealing 
with horizontal motion here that the acceleration value is different so we're 
talking about F=ma.  
 
We know the Force because we know the torque and the effective radius and that 
the force is perpendicular so sin(theta) is 1 and can be ignored.   We know the 
mass.
 
When we set up MAX_VELOCITY and MAX_ACCELERATION in the ini file the velocity 
is in in/sec.  The acceleration we don't know.  We can keep trying values until 
the servo drive reports a following error because the step pulses have exceeded 
the encoder pulses by the preprogramed alarm point.  Then back off until we are 
comfortable.  And if the motor isn't connected then it spins up way faster than 
when it has to move the table.
 
But does the accel value in F=ma have to be gravity?  And if not, what then?
 
John Dammeyer
 
 
> -Original Message-
> From: Bari [mailto:bari00...@gmail.com]
> Sent: July-22-20 9:21 PM
> To: emc-users@lists.sourceforge.net
> Subject: Re: [Emc-users] Calculating table acceleration. Was: Need help with 
> Bostomatic BD18-2 to linuxcnc
> 
> 
> On 7/22/20 11:04 PM, Bruce Layne wrote:
> >
> > On 7/22/20 11:43 PM, Thaddeus Waldner wrote:
> >> 1g = roughly 32in/s^2
> > 1 g is 32 ft/sec^2
> >
> > Feet, not inches.
> >
> 
> Comparing Standard Gravity to Other Acceleration Units
> 
> Standard Gravity��� 1 G's
> Meters per Second per Second��� 9.81
> Feet per Second per Second��� 32.174
> Inches per Second per Second��� 386.09
> 
> 
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Re: [Emc-users] wondering what the status is on S curve jerk control getting added into linuxcnc

[andrew beck]

Yes I'm not worried about servo following error spikes.  But I'm shaking my
whole machine to death.  As the acceleration is instantly on.  In contrast
a friend's okuma can go at 40m/min without shaking.  Which is amazing to
watch.  They are both similar size

On Thu, Jul 23, 2020, 9:42 AM Nicklas SB Karlsson <
nicklas.karlsso...@gmail.com> wrote:

> > hey guys
> >
> > I have a relatively high speed machine (3kw motors 16mm pitch ballscrews)
> >  35mm linear rails, and weights 5.8 ton.  I think it used to go 20m/min
> > with the heidenhain control.  I have been noticing a bit of jumping
> around
> > when doing parallel finishing 3d passed on it at high speed.  and talked
> to
> > a couple of linuxcnc guys and found out that linuxcnc doesn't have any
> jerk
> > control.  ...
>
> If I get it correct from electric motor equations it like this: Jerk could
> be controlled instantly. Available jerk in direction to increase speed
> decrease with speed while available jerk to decrease speed increase with
> speed and this is because of induced back-emf. I assumed a given constant
> magnetic flux inside motor otherwise decrease magnetic flux which may be
> possible in some cases will decrease back-emf and torque and may allow
> higher speed if voltage is a limitation, there is an optimal flux for best
> efficiency. Even though control algorithm is different it should apply for
> the common electric motors: DC, BLDC, PMSM 3-phase synchron motor,
> synchronous reluctance motor and ordinary 3-phase asynchronous induction
> motor.
>
> Not sure how good motion planner is. Read something about a PhD degree but
> are not sure it was for the motion planner in Linuxcnc.
>
> I wrote simpler motion controller, one axis with jerk limitation and had
> to spend quite much time make the corners fit perfectly at the same time it
> followed the limitation and hit target.
>
> > at high speed high precision linuxcnc definitely needs some work at some
> > stage.
>
> Improvements are of course always good. Maybe, but if high speed is used
> then moving thru air "G0 move" or rectracting while speed is lower then
> machining thru part lower precision is acceptable at higher speed.
> Integrator need som time to decrease error so it might be hard work to get
> both at once.
>
>
> Regards Nicklas SB Karlsson
>
>
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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[Chris Albertson]

Why on Earth do people still use US units?   OK if your final result must
be expressed that way, but do the math in metric then convert at the end.

Using US units is like doing long division in Roman numerals.  It can be
done but is way-hard so is it far easier to convert to Arabic number do the
division that converts back to Roman. In Rome a simple problem like
MCXXVI / VII requited the equivalent of graduate-level education.  But
today with our better number system, we teach 10-year-olds to do this with
paper and pencil.

The US system is like using Roman numbers.  It is so hard that most people
get wrong answers.   The proof is in this thread.   So far EVERY
calculation is wrong


One huge mistake I saw is confusing mass and force.  there is no such thing
as a 200-pound mass.  The US unit of mass is the "slug" Your calculations
are off by a factor of about 32 if you try and use pound as mass units.

Doing Physics using US customary units is so horrible that they have not
taught this in schools for the last 40 years.  No one but old folks would
even know this stuff.   I remember my Physics professor at UCLA in the late
1970s saying "just don't bother with feet, slugs and BTUs and miles"   In
high school, we did have to do a few of the problems using feet per second
and slugs of mass.

I think I was of the generation who saw the switch.  We had to use slide
rules in 10th grade but in 11th the decision was made to use calculators
and very soon after that all science education was metric only.

I taught high school science for a while and never once would ever talk
about US units like feet or pints or pounds. The students had no problems
with this as their middle school teachers did the same.   No one who is
educated in the last few decades would know how to work with "feet per
second squared"

Here is a great explanation of US units for mass and force, after reading
it you will see why no one should ever bother with this
https://en.wikipedia.org/wiki/Slug_(unit)



I think the advice I got at UCLA was the best "don't even bother learning
this"


On Wed, Jul 22, 2020 at 9:22 PM Bari  wrote:

>
> On 7/22/20 11:04 PM, Bruce Layne wrote:
> >
> > On 7/22/20 11:43 PM, Thaddeus Waldner wrote:
> >> 1g = roughly 32in/s^2
> > 1 g is 32 ft/sec^2
> >
> > Feet, not inches.
> >
>
> Comparing Standard Gravity to Other Acceleration Units
>
> Standard Gravity1 G's
> Meters per Second per Second9.81
> Feet per Second per Second32.174
> Inches per Second per Second386.09
>
>
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-- 

Chris Albertson
Redondo Beach, California

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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[John Dammeyer]

Hi Chris,

> -Original Message-
> From: Chris Albertson [mailto:albertson.ch...@gmail.com]
> 
> Why on Earth do people still use US units?   OK if your final result must
> be expressed that way, but do the math in metric then convert at the end.

> 
> I taught high school science for a while and never once would ever talk
> about US units like feet or pints or pounds. The students had no problems
> with this as their middle school teachers did the same.   No one who is
> educated in the last few decades would know how to work with "feet per
> second squared"
> 
Appreciate the comments.  But even if I used the servo motor 1.6Nm the pitch of 
the lead screw is 0.2" so I could easily convert that to 5.08mm  or 0.00508m 
for that matter.  In Canada much of what we do is metric.   And my program has 
a check box that lets a user switch along with converting all the imperial 
units to metric and back.  

But that's beside the point I think.  None of what you said explains how to 
calculate the MAX_ACCELERATION in the INI file given parameters like 
motor/leadscrew torque, leadscrew pitch, max speed and table weight (mass).

Any ideas?
John




> 
> Chris Albertson
> Redondo Beach, California
> 
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Re: [Emc-users] wondering what the status is on S curve jerk control getting added into linuxcnc

[dave engvall]

A couple of sources:
http://www.mesanet.com/pdf/motion/softdmc.pdf  50 us cycle -:)

Some years ago a masters candidate in ME at UBC did her thesis on motion 
control with jerk limiting and sine wave accel. I used to have a copy of 
it but cannot find it.
IIRC is would be post 2005 and author's name was something like Silvia 
M(a)cFarland.
On the one axis motion controller what cycle time were you using and did 
faster cycle times smooth it any?


Dave

On 7/22/20 1:51 PM, andrew beck wrote:

hey guys

I have a relatively high speed machine (3kw motors 16mm pitch ballscrews)
  35mm linear rails, and weights 5.8 ton.  I think it used to go 20m/min
with the heidenhain control.  I have been noticing a bit of jumping around
when doing parallel finishing 3d passed on it at high speed.  and talked to
a couple of linuxcnc guys and found out that linuxcnc doesn't have any jerk
control.  just sending out a email here seeing what the current progress is
on that.

at high speed high precision linuxcnc definitely needs some work at some
stage.

apart from this I am completely happy with linuxcnc.  this would be a nice
thing to solve though.  and if someone with the right skills wanted to fix
it I would be happy as to chip in to pay something for the time.  as I run
a business in my machine shop where everything runs linuxcnc

in the mean time I will try to get around the issue by programming in cam

regards

Andrew

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Re: [Emc-users] Calculating table acceleration. Was: Need help with Bostomatic BD18-2 to linuxcnc

[Thomas J Powderly]

John

We used to measure the acceleration rather than calculate it.


We loaded the axis with whatever tooling and 'normal' work piece,

then,  in open loop,

we applied a voltage that would achieve the max velocity, very briefly.

just a bit longer than necc to get to the max velocity ( some hundred of 
millisecond, not whole seconds )


then we measured how long it took to get to the max velocity

_that_ is your practical acceleration in one direction

the test is called a ';step' response

it has nothing to do with stepper motors

it has to do with the immediate 0 to max velocity command

that's the 'step'

on a dual trace storage scope you should monitor the velocity command 
and the velocity.


hth

tomp

( this acc will be greater than the whole machine can achieve turning 
sharp corners and reversing


 but its a real, practical start value )


On 7/23/20 12:57 PM, John Dammeyer wrote:

Hi Chris,


-Original Message-
From: Chris Albertson [mailto:albertson.ch...@gmail.com]

Why on Earth do people still use US units?   OK if your final result must
be expressed that way, but do the math in metric then convert at the end.



I taught high school science for a while and never once would ever talk
about US units like feet or pints or pounds. The students had no problems
with this as their middle school teachers did the same.   No one who is
educated in the last few decades would know how to work with "feet per
second squared"


Appreciate the comments.  But even if I used the servo motor 1.6Nm the pitch of the 
lead screw is 0.2" so I could easily convert that to 5.08mm  or 0.00508m for 
that matter.  In Canada much of what we do is metric.   And my program has a check 
box that lets a user switch along with converting all the imperial units to metric 
and back.

But that's beside the point I think.  None of what you said explains how to 
calculate the MAX_ACCELERATION in the INI file given parameters like 
motor/leadscrew torque, leadscrew pitch, max speed and table weight (mass).

Any ideas?
John





Chris Albertson
Redondo Beach, California

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