Re: [Emc-users] Encoders

[Gene Heskett]

On Tuesday 06 October 2009, Steve Blackmore wrote:
>On Sun, 04 Oct 2009 23:46:48 -0500, you wrote:
>>Steve Blackmore wrote:
>>> Hi Jon
>>>
>>> Encoder is connected to a couple of UA9637ACP differential line
>>> receivers. I'm putting A+ A-, B+ B-, I+ I- in and getting A, B, I out at
>>> 3.5V, should I connect the resistors on the outputs of the line
>>> receiver?
>>
>>Oh, my!  This is getting messy, for sure.  Possibly you do need the
>>pullups on the
>>9637 outputs.  You can certainly try that.  Also, do you have
>>terminators on the differential
>>lines coming into the receiver?  If not, there will be a lot of ringing
>>on every state transition.
>>I usually put a 120 Ohm resistor across the inputs of the line receiver.
>
>Hi Jon - tried 120 Ohm across the inputs - it stopped the line receiver
>working?

Oh.  Dear.  My. Those are either bad encoders, or you have a short to ground 
on one of the two lines from each track of the encoder.

If you put a digital meter on the A+ and A- lines, with one lead on ground 
there should be a full TTL swing on both lines w/o that resistor, and if you 
read from A+ to A- with the resistor, it should alternate polarities and have 
a difference of at least 50 millivolts on both polarities as you move the 
encoder very slowly.

Where are you physically at Steve?  Within a days drive of me perchance?  I'm 
in north central WV, USA.

>The pull ups on the outputs helped marginally but it's much
>better than it was and is quite usable. I'll order some better encoder
>cable and will try and rewire.
>
>
>Steve Blackmore
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Re: [Emc-users] MAXNC Open Loop Mill

[Gene Heskett]

On Tuesday 06 October 2009, Andy Pugh wrote:
>2009/10/6 Wayne Patterson :
>> The machine is also somewhat different then most. It is set up with a
>> Quadrature drive.
>> Unlike a Step and Drive pin. You have two pins the are turned on and off
>> in sequence.
>
>Seems an odd way to do it, but I read that EMC supports that yesterday
>looking for something else. I recall wondering at the time "why?" and
>now I know.
>
>Stepgen mode 1, IIRC
>
Did you ever use an Amiga, and its mouse, and note the mouse was absolutely 
and totally real time?  The quadrature signals from the wheels in it weren't 
encoded into a 1200 baud serial format for sending up the cable, all 4 
signals from both directions went up the cable into a special chip that moved 
the mouse by hardware.  And you couldn't move the mouse fast enough to over 
run that logic.  When LightWave was ported to windows, it was very 
frustrating to the artists who learned LightWave on the amiga, cuz you had to 
move the mouse slowly, and let it sit for a while to make sure your click was 
on the right pixel.

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Re: [Emc-users] Scaling angular axis

[Jon Elson]

John Kasunich wrote:
> Don't use position-interpolated as feedback for position control. 
> Period.
>
> It even says that in the manual (I think).  The problem is that as speed
> approaches zero, and reverses, the interpolator keeps guessing at the
> position until it sees the next encoder count.  Those guesses will drive
> the PID loop nuts.
>   
Worse than just simple delay, a non-deterministic delay.  Yeah, I was 
afraid of
that.

Jon

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Re: [Emc-users] Encoders

[Jon Elson]

Steve Blackmore wrote:
>
>
> Hi Jon - tried 120 Ohm across the inputs - it stopped the line receiver
> working?
It didn't stop the RECEIVER, it stopped the TRANSMITTER from working.
I was already suspecting this, and your report the pull-ups helped 
confirms that the
encoder's transmitter has weak or no pull-up to +5V.  The HalScope 
traces also seemed
to show that.
>  The pull ups on the outputs helped marginally but it's much
> better than it was and is quite usable. I'll order some better encoder
> cable and will try and rewire.
>   
Well, that MAY help.  But, there still seems to be something pretty 
badly wrong with
those encoders, the signals out are just BAD.

Jon

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Re: [Emc-users] Realtime Ethernet

[Jon Elson]

Marc Bodmer wrote:
> Recently I stumbled upon Ethernet Powerlink. They claim to offer
> a true open Realtime Ethernet protocol under the BSD license.
> Cycle times down to 500us with standard Ethernet Slaves and down
> to 100us with special hardware.
>
>   
I'm not sure what "cycle time"means, but that certainly is not a great 
figure.
Maybe, though, it is about where other Ethernet hardware runs, I really 
don't
know. If you wanted to do a several KHz servo cycle, it just can't hack it.
> So far there does not seem to be any very low cost hardware available
> with Powerlink interface yet, But at least there is hardware available
> like digital/analog IO, drives and so on. This is a great plus compared
> to eg. RTNet. (There do not seem to be any products supporting RTNet,
> unfortunately).
>
>   
I don't know if this is compatible with our rtai version of Linux.  Can 
you tell if it is?

I am working on getting the Beagle Board (with TI's OMAP3530 processor) 
set up with a real time
kernel, but that hasn't happened yet.  I have bought another Beagle 
Board and accessories to
ship to Torsten Koschorrek (the RTAI maintainer for ARM-based ports).  I 
am also working
on trying to find out why GPIO pins on the Beagle Board can't be toggled 
any faster than 250 ns,
although the CPU is 150 times faster than that.  The Beagle people don't 
know, so I am now throwing
this in TI's lap.  This is not a killer problem, but it definitely is a 
limitation.  If you have to do a couple
different steps in software to handshake each byte across, it could be 
as bad as half the speed of a
good PC parallel port.  Since all the hardware is INSIDE one chip, it 
ought to be able to flip GPIO
pins something like 10 times faster.

EMC2 has a mode of operation where the GUI is run on another computer 
over Ethernet.  The Beagle
Board is a 500 -600 MHz computer, with none of the insane legacy 
architectural garbage that encrusts
the X86 PC.  It should be a lot closer to the ideal embedded system, 
perfect as a platform for EMC.
(It is a tad expensive, about $200 to get a fully functioning system 
with SD card and Ethernet
adaptor.)

Anyway, work in progress, but if this speed issue can be solved, and if 
Torsten can bring up a
port of RTAI on it, I think we can have a nice EMC2 platform that fits 
in the palm of your hand!
This speed issue won't be much of a concern for software-generated 
steps, either.

Jon

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Re: [Emc-users] MAXNC Open Loop Mill

[Kirk Wallace]

On Tue, 2009-10-06 at 23:40 +0100, Andy Pugh wrote:
> 2009/10/6 Wayne Patterson :
> 
> > The machine is also somewhat different then most. It is set up with a
> > Quadrature drive.
> > Unlike a Step and Drive pin. You have two pins the are turned on and off
> > in sequence.
> 
> Seems an odd way to do it, but I read that EMC supports that yesterday
> looking for something else. I recall wondering at the time "why?" and
> now I know.
> 
> Stepgen mode 1, IIRC

I use EMC2 quadrature output on my Shizuoka mill:
http://www.wallacecompany.com/machine_shop/Shizuoka/ 

which is used to drive the steppers in half-step mode. Basically, there
is just an amplifier between EMC2 and the stepper.

This gives me close to .0005" per step which is good for most projects,
but a micro stepping drive with step/direction would be better. But, if
I upgrade my mill, the plan is to just go with servos.

-- 
Kirk Wallace
http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/index.html
California, USA


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Re: [Emc-users] Scaling angular axis

[John Kasunich]

On Tue, 06 Oct 2009 10:25 +0100, "Andy Pugh" 
wrote:
> 2009/10/6 Jon Elson :
> 
> > I think the basic problem is that the encoder count is by necessity
> > granular,
> > and a lower INPUT_SCALE "magnifies" that granularity.
> 
> Is 'encoder.X.position-interpolated' inappropriate in this situation?
> 

Don't use position-interpolated as feedback for position control. 
Period.

It even says that in the manual (I think).  The problem is that as speed
approaches zero, and reverses, the interpolator keeps guessing at the
position until it sees the next encoder count.  Those guesses will drive
the PID loop nuts.

The interpolated position output is intended mostly for threading, or
any
other application where some slave axis needs to track a master, and the
master speed is more-or-less constant.  There WILL be errors if/when the
master speed changes abruptly or reverses, which a normal machine axis
does all the time.

Regards,

John Kasunich
-- 
  John Kasunich
  jmkasun...@fastmail.fm


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Re: [Emc-users] Encoders

[Steve Blackmore]

On Sun, 04 Oct 2009 23:46:48 -0500, you wrote:

>Steve Blackmore wrote:
>>
>>
>> Hi Jon
>>
>> Encoder is connected to a couple of UA9637ACP differential line
>> receivers. I'm putting A+ A-, B+ B-, I+ I- in and getting A, B, I out at
>> 3.5V, should I connect the resistors on the outputs of the line
>> receiver?
>>
>>   
>Oh, my!  This is getting messy, for sure.  Possibly you do need the 
>pullups on the
>9637 outputs.  You can certainly try that.  Also, do you have 
>terminators on the differential
>lines coming into the receiver?  If not, there will be a lot of ringing 
>on every state transition.
>I usually put a 120 Ohm resistor across the inputs of the line receiver.

Hi Jon - tried 120 Ohm across the inputs - it stopped the line receiver
working? The pull ups on the outputs helped marginally but it's much
better than it was and is quite usable. I'll order some better encoder
cable and will try and rewire.
   

Steve Blackmore
--

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Re: [Emc-users] Wrapped rotary axes, Fanuc style: for testing

[Steve Blackmore]

On Sun, 04 Oct 2009 00:00:14 +0100, you wrote:

>>> If you're up to adding second commands, there should be no objection
>>> then to adding a current Fanuc lathe command like G32 with F for the
>>> feed word that also does taper threads properly (along the Z axis NOT
>>> the hypotenuse) in addition to the G33 ;)
>>
>>No I wouldn't object to someone adding G32.  Do you plan to contribute
>>this?  I'd happily review this contribution.
>
>Yes - how do I go about it.

Chris - did you spot this, if you tell me what you need I'll be happy to
contribute it.

Steve Blackmore
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Re: [Emc-users] MAXNC Open Loop Mill

[Andy Pugh]

2009/10/6 Wayne Patterson :

> The machine is also somewhat different then most. It is set up with a
> Quadrature drive.
> Unlike a Step and Drive pin. You have two pins the are turned on and off
> in sequence.

Seems an odd way to do it, but I read that EMC supports that yesterday
looking for something else. I recall wondering at the time "why?" and
now I know.

Stepgen mode 1, IIRC

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Re: [Emc-users] MAXNC Open Loop Mill

[Wayne Patterson]

I have both.
I prefer Linux so that means EMC2.
The machine is also somewhat different then most. It is set up with a 
Quadrature drive.
Unlike a Step and Drive pin. You have two pins the are turned on and off 
in sequence.

Andy Pugh wrote:
> 2009/10/6 Wayne Patterson :
>
>   
>> But I have never set up a machine before.
>> 
>
> I assume you are using EMC2 rather than the software supplied by the
> manufacturer?
>
>   

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[Emc-users] Realtime Ethernet

[Marc Bodmer]

Hello EMC Users/Developers

I'd like to bring up the discussion about Realtime Ethernet in EMC
again. There were several discussions about this topic, from RAW
Ethernet packages over RTNet to full fledged EthetCAT or SERCOS.
The problem with the latter seems to be the not so open, so called
open licenses and the special slave hardware involved rendering this
technology not so well suited to the very low budget home cnc builder.

Recently I stumbled upon Ethernet Powerlink. They claim to offer
a true open Realtime Ethernet protocol under the BSD license.
Cycle times down to 500us with standard Ethernet Slaves and down
to 100us with special hardware.

http://www.ethernet-powerlink.org

The open license makes it interesting for opensource projects like
EMC. IMHO

So far there does not seem to be any very low cost hardware available
with Powerlink interface yet, But at least there is hardware available
like digital/analog IO, drives and so on. This is a great plus compared
to eg. RTNet. (There do not seem to be any products supporting RTNet,
unfortunately).

Furthermore the OSASL seems to be working on mainline Linux Kernel
integration of their Ethernet Powerlink stack.
http://www.osadl.org

So, what do you guys think? Could Powerlink based products be a
possible future replacement for the current pci cards and parallel
port hardware in EMC, or at least be a good alternative to it?

Maybe there will be open hardware projects with powerlink interface
like e.g. http://groups.yahoo.com/group/osmc/ or low budget commercial
products like http://pico-systems.com/ and http://www.geckodrive.com/

regards
Marc



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Re: [Emc-users] MAXNC Open Loop Mill

[Andy Pugh]

2009/10/6 Wayne Patterson :

> But I have never set up a machine before.

I assume you are using EMC2 rather than the software supplied by the
manufacturer?

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Re: [Emc-users] More Spindle Soft Start

[Andy I]

Thanks to everyone for their help.  I now have full control of my X2 spindle
and coolant supply via EMC.  Spindle soft starts and is calibrated from
600rpm to 4000rpm + I have lost my fear (to some extent) of changing my .hal
file.
Regards
Andy

-Original Message-
From: Andy Pugh [mailto:a...@andypugh.fsnet.co.uk] 
Sent: 04 October 2009 16:52
To: Enhanced Machine Controller (EMC)
Subject: Re: [Emc-users] More Spindle Soft Start

2009/10/4 Jeff Epler :

> No.  Parameters can't be linked.

Sorry, it turns out that what I thought it was compiling happily was
being overwritten by custom.hal.

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Re: [Emc-users] Where to put controllers?

[Gene Heskett]

On Tuesday 06 October 2009, Dave wrote:
>If I had my druthers, aluminum wire and terminal blocks would not be
>used also 
>But cheapness pervades..
>
>I've been doing control and power engineering work for about 30 years
>now and I have only seen a few instances where alum entrance cable has
>screwed up.
>
>Usually because it wasn't prepped properly.  But you are right, if you
>want bullet proof reliability you don't use alum in electrical
>installation.  I am sure that the space shuttle does not have any
>aluminum terminal blocks in it!
>
>Still, try and find a heavy junction power block for industrial use that
>is not alum   It is pretty much impossible.

Yes, a box I put in to service a standby tx about 5 years ago was all alu for 
its buss bars.  Needless to say, all the connections have been re-snugged, 
several times although its actually wired with copper.

>That is also pretty much all the power company will run any longer.   I
>have some new 15KV lines on the poles in front of my place and they are
>all twisted alum cable.
>
And you would be wise to cop a feel of the crimp sleeves at your weather head 
occasionally.

>>>Chuckle, with suitable emphasis on the cheap part Dave.  Copper is plumb
>outta sight now.
>
>Actually it has come down a lot.  A 500 ft roll of THHN 10 gauge stranded
> was over a hundred bucks a roll for a while.

Ouch!

>The last I checked it is about $55 now.   It is sort of like gas at $2.30 a
> gallon, it is cheap compared with $4.50!  ;-)

Sound like I better go stock up on a box of 12-2/wg then, I'm getting low.

>The copper ground/neutral bus bars I bought at the local home store
> recently for a star ground central point were about $6.50 each.  Cheap by
> industrial prices  ...

Yup, considering there is more machine work in making it than there is 
material in it, that 'work' is what we pay for at the end of the day.

>I was talking with a customer of mine today...  They were talking about
> some slide mechanisms that had to be replaced on a machine I helped
> install last year..   The replacement parts being discussed were "only"
> about $10K they said So everything is relative.  :-)

"Only" eh?  But you are correct.  In broadcasting, I am constantly amazed at 
how somebody can take 75 pounds of sheet alu, heliarc weld it into a specific 
shape for an RF mask filter, and get nearly $20k for the finished product.  
Until you realize that every dimension in it, is calculated to a tolerance of 
maybe .005", and it still has adjustment screws they tune once and locktite 
forever, or until it gets abused and dented.  Since this stuff is usually 
installed on the tx output lines, its normally about ceiling high, catches 
more hell from the errant stepladder while replacing lamps than anything 
else.

The cost of something is always relative to the cost of the something it goes 
with.  A basic truism.

[...]

-- 
Cheers, Gene
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 soap, ballot, jury, and ammo. Please use in that order."
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Re: [Emc-users] Where to put controllers?

[Gene Heskett]

On Tuesday 06 October 2009, Gene Heskett wrote:
[huge snip about strange noises]
>
>Just for grins, I'm going to haul my scope out there and see what I find,
> and I'll report back.  Curiosity bumps need rubbed and scratched you know.

Back from the shop.

I wasn't able to get a extension lead to that star point in my lashup, the 
closest I could get was the chassis of the stepper motors psu, about 30" of 
14 gauge wire away.

Just waving the probe around I was able to find the short un-shielded 
sections between where the shielding of the motor cables stops and the 
motors, a fair amount of noise that was pretty much gone by the time I was 6" 
of air away.  And my running spindle has about 250 volts of combined noise 
and power when connected directly to it.  The best pickup I could get without 
connection was about 15 volts with the probe laying against the cable for 
about 3".  That seems fairly noisy, but I can't hear it but very faintly on 
an AM radio 7 feet away, listening to our local AM'er after daytime hours 
when he has to reduce to 50 watts at sundown.  He plays a mix of county and 
bluegrass that time of the night.  Other neighborhood noises are worse than 
the spindle motor.

Hooked onto the z sled, or to the machine frame, was all the same, and about 
4.5 volts of noise was generated by the xylotex, but it was very fast, all 
settled and quiet well within a microsecond, the majority of it in the first 
15 nanoseconds.  I am inclined to think that I was looking at the 3 foot 
ground lead acting as an antenna because I got an identical display when 
checking the chassis of the psu.  Long ground leads can do some real funkity 
stuff in the less than a microsecond time frames.

Noise that you can see, and which lasts much longer than a microsecond, 
probably should be run down and fixed.  But I didn't see anything to worry 
about.  I should probably shield the spindle motor lead but haven't found a 
shielded cable rated for line voltages and up.  Haven't looked all that hard 
either TBT.

-- 
Cheers, Gene
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Re: [Emc-users] Where to put controllers?

[Dave]

If I had my druthers, aluminum wire and terminal blocks would not be 
used also 
But cheapness pervades.. 

I've been doing control and power engineering work for about 30 years 
now and I have only seen a few instances where alum entrance cable has 
screwed up. 

Usually because it wasn't prepped properly.  But you are right, if you 
want bullet proof reliability you don't use alum in electrical 
installation.  I am sure that the space shuttle does not have any 
aluminum terminal blocks in it! 

Still, try and find a heavy junction power block for industrial use that 
is not alum   It is pretty much impossible.

That is also pretty much all the power company will run any longer.   I 
have some new 15KV lines on the poles in front of my place and they are 
all twisted alum cable. 

>>Chuckle, with suitable emphasis on the cheap part Dave.  Copper is plumb 
outta sight now.

Actually it has come down a lot.  A 500 ft roll of THHN 10 gauge stranded was 
over a hundred bucks a roll for a while.

The last I checked it is about $55 now.   It is sort of like gas at $2.30 a 
gallon, it is cheap compared with $4.50!  ;-)

The copper ground/neutral bus bars I bought at the local home store recently 
for a star ground central point were about $6.50 each.  Cheap by industrial 
prices  ...   

I was talking with a customer of mine today...  They were talking about some 
slide mechanisms that had to be replaced on a machine I helped install last 
year..   The replacement parts being discussed were "only" about $10K they 
said So everything is relative.  :-)


Dave


Gene Heskett wrote:
> On Tuesday 06 October 2009, Dave wrote:
>   
 This relaxes the joint pressure, air gets in, and
 
>> alu does what it normally does when exposed to the oxygen in the air, form
>> an insulating film with 100% coverage, and a 30-50 volt breakdown in about
>> one millisecond.  Alu is great, in its place, but inside an electrical box
>> of any kind its just a damned fire starter with a long fuse timing.
>> <<
>>
>> While I agree that copper is much superior to alum. and alum wiring when
>> used in places like house wiring didn't turn out so well, however alum
>> power cable is pretty much the standard for service entrances.  Also many
>> panel power components are made of alum - often with plating to prevent
>> the oxidatation problems.
>> 
>
> Even for power drops they are a fire starter.  In my 25 years of being the CE 
> at WDTV, we were knocked off the air and had to replace all the 750mcm cable 
> from the substation pole to the tx building twice due to grand and glorious 
> fireworks from a Burndy Hy-Press installed alu sleeve failing just outside 
> the weather head.  Twice.  The last time the fire went largely un-noticed by 
> the operator on duty in the building, and the heat telegraphed down our 
> copper 750mcm so well that when we laid the weather head on the ground and 
> pulled it apart, the insulation was cooked for about 3 feet into the weather 
> head.  The power guys wanted to run alu into the weather head and into the 
> meter base inside the building, but I scrounged up enough 750mcm in copper 
> that we could rebuild it in copper.  But they refused, claiming they didn't 
> have any copper that heavy, to string anything but alu from the weather head 
> to the substation pole.  And only 600mcm to boot.  I was seen as grumbling 
> about it when I walked away, defeated cuz that run wasn't ours.
>
> My house is all copper, but the service drop they replaced with a heavier 
> cable when I added a 200 amp service 4 years ago, is alu..  And every time 
> I'm on the roof, I 'cop a feel' of each crimp sleeve to make sure there's no 
> heat.  So far, so good, like the guy that plans to live forever said.
>
> I bought a house in Nebraska that had alu jumpers from the meter head 
> outside, to the service box inside, about an 8 inch run.  I put out 2 fires 
> in the middle of the night in that box or in the meter head, the 2nd time 
> they got replaced with some 000 I had at the transmitter, color code be 
> damned.  And its a felony to break the seal on a meter head in Nebraska.  I 
> called Ron, the line super at Wayne County Public power the next morning both 
> times and told him to send somebody by with a new seal.  He already knew me 
> well, so the next question was "what the hell were you doing in there?" 
> knowing the answer was related to alu wire before he asked it.
>
>   
>> It's like everything else, if you do it the right way, no problems, ignore
>> the rules and they will come back and bite you.
>> 
>
> If one goes around and inspects it, tightening loose connections, it can be 
> pretty good.  The average home owner cannot do that and has no clue that it 
> needs to be done from time to time.  He gets his wake up call when his 
> insurance denies his claim because there was alu wire found in the ashes of 
> what was a $350k home..
>
>   
>> Most alum terminal blocks and even 

Re: [Emc-users] Where to put controllers?

[Gene Heskett]

On Tuesday 06 October 2009, Dave wrote:
>>>This relaxes the joint pressure, air gets in, and
>
>alu does what it normally does when exposed to the oxygen in the air, form
> an insulating film with 100% coverage, and a 30-50 volt breakdown in about
> one millisecond.  Alu is great, in its place, but inside an electrical box
> of any kind its just a damned fire starter with a long fuse timing.
><<
>
>While I agree that copper is much superior to alum. and alum wiring when
> used in places like house wiring didn't turn out so well, however alum
> power cable is pretty much the standard for service entrances.  Also many
> panel power components are made of alum - often with plating to prevent
> the oxidatation problems.

Even for power drops they are a fire starter.  In my 25 years of being the CE 
at WDTV, we were knocked off the air and had to replace all the 750mcm cable 
from the substation pole to the tx building twice due to grand and glorious 
fireworks from a Burndy Hy-Press installed alu sleeve failing just outside 
the weather head.  Twice.  The last time the fire went largely un-noticed by 
the operator on duty in the building, and the heat telegraphed down our 
copper 750mcm so well that when we laid the weather head on the ground and 
pulled it apart, the insulation was cooked for about 3 feet into the weather 
head.  The power guys wanted to run alu into the weather head and into the 
meter base inside the building, but I scrounged up enough 750mcm in copper 
that we could rebuild it in copper.  But they refused, claiming they didn't 
have any copper that heavy, to string anything but alu from the weather head 
to the substation pole.  And only 600mcm to boot.  I was seen as grumbling 
about it when I walked away, defeated cuz that run wasn't ours.

My house is all copper, but the service drop they replaced with a heavier 
cable when I added a 200 amp service 4 years ago, is alu..  And every time 
I'm on the roof, I 'cop a feel' of each crimp sleeve to make sure there's no 
heat.  So far, so good, like the guy that plans to live forever said.

I bought a house in Nebraska that had alu jumpers from the meter head 
outside, to the service box inside, about an 8 inch run.  I put out 2 fires 
in the middle of the night in that box or in the meter head, the 2nd time 
they got replaced with some 000 I had at the transmitter, color code be 
damned.  And its a felony to break the seal on a meter head in Nebraska.  I 
called Ron, the line super at Wayne County Public power the next morning both 
times and told him to send somebody by with a new seal.  He already knew me 
well, so the next question was "what the hell were you doing in there?" 
knowing the answer was related to alu wire before he asked it.

>It's like everything else, if you do it the right way, no problems, ignore
> the rules and they will come back and bite you.

If one goes around and inspects it, tightening loose connections, it can be 
pretty good.  The average home owner cannot do that and has no clue that it 
needs to be done from time to time.  He gets his wake up call when his 
insurance denies his claim because there was alu wire found in the ashes of 
what was a $350k home..

>Most alum terminal blocks and even the grounding/neutral bars you can buy
> at home depot etc are either tin plated copper or tin plated alum.

Even tin plated alu would scare me, cuz that tin plate can't have a 
continuous metal to metal connection to the alu.  Cleanly cut alu will form 
an oxide coating in a millisecond that is good for 40 volts, and if it lays 
around a day between machining and plating, it will be good for 400 volts. 
alu oxide is two things, first the second hardest substance commonly 
available, and second, a good enough insulator that it has been used as a 
replacement for the mica or silicon rubber insulators between power 
transistors and their heat sinks.  I've actually seen it use in older 
transistorized tv's under the horizontal output transistor, which may have as 
much as 1600 volts on it at the instant its turned off at anywhere from 15 to 
120 khz.

>The ones I have used before are tin plated copper.   They work great and
> they are cheap.

Chuckle, with suitable emphasis on the cheap part Dave.  Copper is plumb 
outta sight now.

>Dave
>
>
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 soap, ballot, jury, and ammo. Please use in that order."

[Emc-users] MAXNC Open Loop Mill

[Wayne Patterson]

Hello,
Is there anyone on the list using a MAXNC open loop CNC Milling machine?
I just got mine in a few days ago and I am excited about using it. I 
have some toys I want to build. =)
But I have never set up a machine before. So I was hoping that someone 
on the list has been through this before and could give me some pointers 
and warn me of some pitfalls.
Thanks for any and all help.
LennyWayne

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Re: [Emc-users] Where to put controllers?

[Gene Heskett]

On Tuesday 06 October 2009, Ian W. Wright wrote:
>Thanks guys,
>
>That's that then, controllers in a cabinet again!
>
>Gene,
>Having worked on installing mainframe computers for many
>years I do normally use star earths for anything electronic
>and my previous controller cabinet certainly has this - a
>central bolt - for all the stepper control stuff and the
>wiring for each stepper was done in shielded cable with the
>shielding tied to the star point and the shielding extended
>right up to, but not tied to the motors..

100% right so far.

>The spindle - a
>mains high speed brush motor, however was separately fed via
>a thyristor speed control board from a relay in the control
>cabinet. The motor has suppressors across the brushes

Ouch!  If the motor is being fed by an HF switching VSD, like mine is, that 
would put a heavier than normal stress on the HexFet such a speed controller 
uses to control the motor.

The problem with the noise filters is that they contain capacitors used as 
bypasses to shunt the noise to ground, and the charge they absorb at the 
instant either the thyristor in your control, or the HexFet in mine, are 
turned on.  Then those capacitance's need to be recharged to operating 
voltage and can absorb 10 of amps for a microsecond or so.  That sure can 
telegraph back through the mains wiring for that drive.

I had the top cap off of my spindle motor once because I was curious as to 
how much trouble it might be to renew the brushes in my PM field universal 
motor.  I did not find any noise suppression in mine.

So in my case, all I have is the relatively square wave at about 150 volts 
peak, at about 25 khz, which _should_ be at least as noisy as the brush 
arcing.  However there is not another power load on the machine, so the green 
wire in the motors power cord, which now goes back to the VSD I took out of 
the gear head and put into the same box as the PMDX-106, that ground carries 
on to the PMDX-106, and on through the control signal cable running the 
PMDX-106, and hence eventually to my central 'star' point.

The only theory I can come up with quickly is that while the machine itself 
may be grounded via whatever it might have for a power cord, lighting maybe, 
but that the Z might not be tied to the frame very well due to the lube on 
the ways.  Any number of scenarios can be imagined depending on the machine 
configuration.  In my case, the whole Z drive is bolted solidly to the top of 
the z post, so that is fairly well grounded.  But the Z sled and gibs could 
lead to some isolation of the noise, again due to the lube on the ways.

If you have a decent scope, float its power cord with a 3 to 2 adapter, and 
ground the probes to a heavier wire that is tied to the star point, and just 
go poking around to see where the noise is coming from.  Bear in mind that 
long ground will be a good antenna, picking up quite a bit of noise all by 
itself, but after a while, you get the feel for what is different.  Because 
we're looking for something that is pretty noisy, I'd turn up the gain and 
just go look for maximum noise that is not the chopper of the axis drives.

Just for grins, I'm going to haul my scope out there and see what I find, and 
I'll report back.  Curiosity bumps need rubbed and scratched you know.


>and to
>earth and all the earths on this side of things were tied to
>an earthing point on the machine and so I suppose that there
>is a vague possibility that interference could have tracked
>back through the mains wiring although here again, the mains
>to both parts was fed from the same wall socket. However, I
>am skeptical of this as the only axis that was affected was
>the Z-axis - the one nearest the spindle motor.

And that, to me, is the puzzling part.  There can be borderline situations 
where just one axis is sensitive enough to be effected, but the instances of 
it being the z are all out of proportion.

>I tried
>several spindle motors without curing the problem ( the axis
>would very slowly feed down into the work ) and only solved
>it when I changed to a synchronous-type of motor. Maybe
>there was something amiss with the stepper which made it
>susceptible to interference - I don't know.
>
>Ian
>___
>Ian W. Wright
>Sheffield  UK
>
>---
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 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
The

Re: [Emc-users] Scaling angular axis

[Peter C. Wallace]

On Tue, 6 Oct 2009, Eric H. Johnson wrote:

> Date: Tue, 6 Oct 2009 11:19:11 -0400
> From: Eric H. Johnson 
> Reply-To: "Enhanced Machine Controller (EMC)"
> 
> To: "'Enhanced Machine Controller (EMC)'" 
> Subject: Re: [Emc-users] Scaling angular axis
> 
> John,
>
> Ok, got it. Fractional values for PID values just didn't seem right, but
> after closer inspection I see how it would work out that way. It wasn't that
> close to a divide by 360 however, more like divide by 60, at least for P. I
> and D were already too small to establish a meaningful proportionality.
>
> I had not really thought through the consequences of giving scaled, real
> world positions to the pid component's command and feedback pins, as opposed
> to raw encoder positions, as is the case with most other types of motion
> systems I have used.
>
> ISTM there are advantages to using raw encoder values rather than real world
> positions for PID tuning, in that it eliminates the effects of a number of
> variables such as gear ratio and acceleration (real world, as opposed to
> encoder counts per sec^2). It also means that the same motor / encoder pair
> should have the same, or very close to the same pid values, regardless of
> gearing or other scaling (linear vs. angular for example).
>
> Regards,
> Eric

Maybe there's a way to use the PWM scale to compensate for input scale so you 
end up with commensurate PID values...



Peter Wallace
Mesa Electronics

(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination.


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Re: [Emc-users] Scaling angular axis

[Jon Elson]

Andy Pugh wrote:
> 2009/10/6 Jon Elson :
>
>   
>> I think the basic problem is that the encoder count is by necessity
>> granular,
>> and a lower INPUT_SCALE "magnifies" that granularity.
>> 
>
> Is 'encoder.X.position-interpolated' inappropriate in this situation?
>   
I'm afraid I can't answer that.  The systems I have worked on were done 
before the
interpolated position or velocity estimation was used, and my drivers 
(blush) still
don't have this feature.  It certainly sounds like it might help, but 
when put into a
servo loop, you have to be careful with anything that could introduce delay.

Jon

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Re: [Emc-users] Where to put controllers?

[Dave]

>>This relaxes the joint pressure, air gets in, and 
alu does what it normally does when exposed to the oxygen in the air, form an 
insulating film with 100% coverage, and a 30-50 volt breakdown in about one 
millisecond.  Alu is great, in its place, but inside an electrical box of any 
kind its just a damned fire starter with a long fuse timing.
<<

While I agree that copper is much superior to alum. and alum wiring when used 
in places like house wiring didn't turn out so well, however alum power cable 
is pretty much the standard for service entrances.  Also many panel power 
components are made of alum - often with plating to prevent the oxidatation 
problems.  

It's like everything else, if you do it the right way, no problems, ignore the 
rules and they will come back and bite you.  

Most alum terminal blocks and even the grounding/neutral bars you can buy at 
home depot etc are either tin plated copper or tin plated alum.  

The ones I have used before are tin plated copper.   They work great and they 
are cheap.

Dave 


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Re: [Emc-users] Where to put controllers?

[Ian W. Wright]

Thanks guys,

That's that then, controllers in a cabinet again!

Gene,
Having worked on installing mainframe computers for many 
years I do normally use star earths for anything electronic 
and my previous controller cabinet certainly has this - a 
central bolt - for all the stepper control stuff and the 
wiring for each stepper was done in shielded cable with the 
shielding tied to the star point and the shielding extended 
right up to, but not tied to the motors.. The spindle - a 
mains high speed brush motor, however was separately fed via 
a thyristor speed control board from a relay in the control 
cabinet. The motor has suppressors across the brushes and to 
earth and all the earths on this side of things were tied to 
an earthing point on the machine and so I suppose that there 
is a vague possibility that interference could have tracked 
back through the mains wiring although here again, the mains 
to both parts was fed from the same wall socket. However, I 
am skeptical of this as the only axis that was affected was 
the Z-axis - the one nearest the spindle motor. I tried 
several spindle motors without curing the problem ( the axis 
would very slowly feed down into the work ) and only solved 
it when I changed to a synchronous-type of motor. Maybe 
there was something amiss with the stepper which made it 
susceptible to interference - I don't know.

Ian
___
Ian W. Wright
Sheffield  UK

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Re: [Emc-users] Where to put controllers?

[Gene Heskett]

On Tuesday 06 October 2009, dave wrote:
>On Tue, 2009-10-06 at 09:47 -0400, Gene Heskett wrote:
>> On Tuesday 06 October 2009, Ian W. Wright wrote:
>> >HI,
>> >
>> >I'm in the process of building a second little mill - this
>> >time a stepper-driven gantry type and I'm wondering what the
>> >pros and cons might be of different driver locations. On the
>> >first mill I had all the controls in a big box under the
>> >bench with heavy wires going to each motor but I'm wondering
>> >now whether any advantage might be gained in this project by
>> >positioning the driver cards adjacent to each motor. This
>> >would shorten the cables carrying power to the motor but
>> >would mean carrying signal cables from the parallel port
>> >around the machine together with DC power wires to each
>> >card. One reason for considering this is that, on my
>> >previous machine, I had a problem with the Z-axis stepper
>> >picking up interference from brushed spindle motors and so I
>> >had to change to a 'universal' AC motor drive for the
>> >spindle which was heavy and limited in speed. I tried
>> >various methods of screening the Z-axis motor leads and put
>> >ferrite beads over them but nothing seemed to work. As I'd
>> >like to use a high speed spindle based on a DC motor on this
>> >mill, I wondered if it might be easier to shield the
>> >'signal-in' wires rather than the power wires to the motor.
>> >Any thoughts?
>> >
>> >Ian
>>
>> I may sound like a broken record Ian, but the 'star' grounding
>> configuration, and running all signal and motor drive circuits through a
>> cable similar to Belden "Star-Quad" with all the shielding for even the
>> motors output drive tied to the central point of this star, where the
>> central point where it all comes together is at the common point.  The
>> cumputers ground line from the parport, and the minus rail of the motor
>> power psu are all connected, possibly to a single long bolt, or in my
>> case I ran a handy piece of 12 gauge bare copper that goes from the motor
>> - terminal on the xylotex, around to the side of the box I made for the
>> xylotex board, so that the shields of the motor cables were tied to it. 
>> My motor cables are about 6 feet long, and the shields stop short of the
>> motor, no connection on that end.  The machines ground is also connected
>> there via a rather circuitous route going through the spindle motors
>> power cable, the one cable that is not shielded, via the PMDX-106 and the
>> interconnecting cable back to the breakout strip on the xylotex.
>>
>> I have not had any noise problems.
>>
>> Belden's search facilities can be confusing.
>>
>> Another supplier might be Canare
>> 
>
>I've been known go to Home Depot and buy a Cutler-Hammer neutral bar;
>and tie everything to that. Seems to work.
>
That, and no place else for each branch that leaves it.  Same idea as by 
piece of 12 gauge and a hot soldering iron.  Either will work provided the 
screws are tight enough to present a gas tight joint for extended amounts of 
time.  You cannot do that with alu conductors of course as they cold flow at 
20x the rate of copper.  This relaxes the joint pressure, air gets in, and 
alu does what it normally does when exposed to the oxygen in the air, form an 
insulating film with 100% coverage, and a 30-50 volt breakdown in about one 
millisecond.  Alu is great, in its place, but inside an electrical box of any 
kind its just a damned fire starter with a long fuse timing.

>Dave
>
>
>---
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The NRA is offering FREE Associate memberships to anyone who wants them.


The opulence of the front office door varies inversely with the fundamental
solvency of the firm.

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Re: [Emc-users] Scaling angular axis

[Eric H. Johnson]

John,

Ok, got it. Fractional values for PID values just didn't seem right, but
after closer inspection I see how it would work out that way. It wasn't that
close to a divide by 360 however, more like divide by 60, at least for P. I
and D were already too small to establish a meaningful proportionality.

I had not really thought through the consequences of giving scaled, real
world positions to the pid component's command and feedback pins, as opposed
to raw encoder positions, as is the case with most other types of motion
systems I have used.

ISTM there are advantages to using raw encoder values rather than real world
positions for PID tuning, in that it eliminates the effects of a number of
variables such as gear ratio and acceleration (real world, as opposed to
encoder counts per sec^2). It also means that the same motor / encoder pair
should have the same, or very close to the same pid values, regardless of
gearing or other scaling (linear vs. angular for example).

Regards,
Eric

Write down the PID gains that work when the scale is 18400.  Then, since you
are dividing the scale by 360 to get 51.1, you should be able to also divide
the gains by 360, and the resulting PID results should be identical.
Take the old gains, divide by 360, and try them as a starting point for
tuning.



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Re: [Emc-users] Where to put controllers?

[Dave]

>>I've been known go to Home Depot and buy a Cutler-Hammer neutral bar;
and tie everything to that. Seems to work. 

I've done the same thing, it works well.  Screw the bar to the steel backplane 
and make that the center of the "star" ground.

Best thing you can do for CNC components is to put everything into a steel box 
and use a star ground.  Position the box to minimize wiring distances.   Put 
the PC into the same box if you can.  That will allow signal wires to be very 
short minimizing the chances for noise pickup.  If you have a spindle VFD, 
consider putting it in a separate box or put a filter on the front end and the 
motor leads.  Some VFDs are incredible noise makers. 

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=160367025737&ssPageName=STRK:MESE:IT

The guy selling these is extremely reputable..  (a shameless plug) ;-)  I have 
other versions of the same PC with PCI slots also for Mesa boards etc.

You can actually mount something like this on the inside of the panel door 
saving space on the backplane for the drives, power supply etc.

Automationdirect.com has some decent prices on enclosures, but surplus 
electrical houses also sell used enclosures usually very cheaply.

Dave





dave wrote:
> On Tue, 2009-10-06 at 09:47 -0400, Gene Heskett wrote:
>   
>> On Tuesday 06 October 2009, Ian W. Wright wrote:
>> 
>>> HI,
>>>
>>> I'm in the process of building a second little mill - this
>>> time a stepper-driven gantry type and I'm wondering what the
>>> pros and cons might be of different driver locations. On the
>>> first mill I had all the controls in a big box under the
>>> bench with heavy wires going to each motor but I'm wondering
>>> now whether any advantage might be gained in this project by
>>> positioning the driver cards adjacent to each motor. This
>>> would shorten the cables carrying power to the motor but
>>> would mean carrying signal cables from the parallel port
>>> around the machine together with DC power wires to each
>>> card. One reason for considering this is that, on my
>>> previous machine, I had a problem with the Z-axis stepper
>>> picking up interference from brushed spindle motors and so I
>>> had to change to a 'universal' AC motor drive for the
>>> spindle which was heavy and limited in speed. I tried
>>> various methods of screening the Z-axis motor leads and put
>>> ferrite beads over them but nothing seemed to work. As I'd
>>> like to use a high speed spindle based on a DC motor on this
>>> mill, I wondered if it might be easier to shield the
>>> 'signal-in' wires rather than the power wires to the motor.
>>> Any thoughts?
>>>
>>> Ian
>>>   
>> I may sound like a broken record Ian, but the 'star' grounding 
>> configuration, 
>> and running all signal and motor drive circuits through a cable similar to 
>> Belden "Star-Quad" with all the shielding for even the motors output drive 
>> tied to the central point of this star, where the central point where it all 
>> comes together is at the common point.  The cumputers ground line from the 
>> parport, and the minus rail of the motor power psu are all connected, 
>> possibly to a single long bolt, or in my case I ran a handy piece of 12 
>> gauge 
>> bare copper that goes from the motor - terminal on the xylotex, around to 
>> the 
>> side of the box I made for the xylotex board, so that the shields of the 
>> motor cables were tied to it.  My motor cables are about 6 feet long, and 
>> the 
>> shields stop short of the motor, no connection on that end.  The machines 
>> ground is also connected there via a rather circuitous route going through 
>> the spindle motors power cable, the one cable that is not shielded, via the 
>> PMDX-106 and the interconnecting cable back to the breakout strip on the 
>> xylotex.
>>
>> I have not had any noise problems.
>>
>> Belden's search facilities can be confusing.
>>
>> Another supplier might be Canare
>> 
>>
>> 
> I've been known go to Home Depot and buy a Cutler-Hammer neutral bar;
> and tie everything to that. Seems to work. 
>
> Dave
>
>
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Re: [Emc-users] Where to put controllers?

[dave]

On Tue, 2009-10-06 at 09:47 -0400, Gene Heskett wrote:
> On Tuesday 06 October 2009, Ian W. Wright wrote:
> >HI,
> >
> >I'm in the process of building a second little mill - this
> >time a stepper-driven gantry type and I'm wondering what the
> >pros and cons might be of different driver locations. On the
> >first mill I had all the controls in a big box under the
> >bench with heavy wires going to each motor but I'm wondering
> >now whether any advantage might be gained in this project by
> >positioning the driver cards adjacent to each motor. This
> >would shorten the cables carrying power to the motor but
> >would mean carrying signal cables from the parallel port
> >around the machine together with DC power wires to each
> >card. One reason for considering this is that, on my
> >previous machine, I had a problem with the Z-axis stepper
> >picking up interference from brushed spindle motors and so I
> >had to change to a 'universal' AC motor drive for the
> >spindle which was heavy and limited in speed. I tried
> >various methods of screening the Z-axis motor leads and put
> >ferrite beads over them but nothing seemed to work. As I'd
> >like to use a high speed spindle based on a DC motor on this
> >mill, I wondered if it might be easier to shield the
> >'signal-in' wires rather than the power wires to the motor.
> >Any thoughts?
> >
> >Ian
> 
> I may sound like a broken record Ian, but the 'star' grounding configuration, 
> and running all signal and motor drive circuits through a cable similar to 
> Belden "Star-Quad" with all the shielding for even the motors output drive 
> tied to the central point of this star, where the central point where it all 
> comes together is at the common point.  The cumputers ground line from the 
> parport, and the minus rail of the motor power psu are all connected, 
> possibly to a single long bolt, or in my case I ran a handy piece of 12 gauge 
> bare copper that goes from the motor - terminal on the xylotex, around to the 
> side of the box I made for the xylotex board, so that the shields of the 
> motor cables were tied to it.  My motor cables are about 6 feet long, and the 
> shields stop short of the motor, no connection on that end.  The machines 
> ground is also connected there via a rather circuitous route going through 
> the spindle motors power cable, the one cable that is not shielded, via the 
> PMDX-106 and the interconnecting cable back to the breakout strip on the 
> xylotex.
> 
> I have not had any noise problems.
> 
> Belden's search facilities can be confusing.
> 
> Another supplier might be Canare
> 
> 
I've been known go to Home Depot and buy a Cutler-Hammer neutral bar;
and tie everything to that. Seems to work. 

Dave


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Re: [Emc-users] Where to put controllers?

[Gene Heskett]

On Tuesday 06 October 2009, Ian W. Wright wrote:
>HI,
>
>I'm in the process of building a second little mill - this
>time a stepper-driven gantry type and I'm wondering what the
>pros and cons might be of different driver locations. On the
>first mill I had all the controls in a big box under the
>bench with heavy wires going to each motor but I'm wondering
>now whether any advantage might be gained in this project by
>positioning the driver cards adjacent to each motor. This
>would shorten the cables carrying power to the motor but
>would mean carrying signal cables from the parallel port
>around the machine together with DC power wires to each
>card. One reason for considering this is that, on my
>previous machine, I had a problem with the Z-axis stepper
>picking up interference from brushed spindle motors and so I
>had to change to a 'universal' AC motor drive for the
>spindle which was heavy and limited in speed. I tried
>various methods of screening the Z-axis motor leads and put
>ferrite beads over them but nothing seemed to work. As I'd
>like to use a high speed spindle based on a DC motor on this
>mill, I wondered if it might be easier to shield the
>'signal-in' wires rather than the power wires to the motor.
>Any thoughts?
>
>Ian

I may sound like a broken record Ian, but the 'star' grounding configuration, 
and running all signal and motor drive circuits through a cable similar to 
Belden "Star-Quad" with all the shielding for even the motors output drive 
tied to the central point of this star, where the central point where it all 
comes together is at the common point.  The cumputers ground line from the 
parport, and the minus rail of the motor power psu are all connected, 
possibly to a single long bolt, or in my case I ran a handy piece of 12 gauge 
bare copper that goes from the motor - terminal on the xylotex, around to the 
side of the box I made for the xylotex board, so that the shields of the 
motor cables were tied to it.  My motor cables are about 6 feet long, and the 
shields stop short of the motor, no connection on that end.  The machines 
ground is also connected there via a rather circuitous route going through 
the spindle motors power cable, the one cable that is not shielded, via the 
PMDX-106 and the interconnecting cable back to the breakout strip on the 
xylotex.

I have not had any noise problems.

Belden's search facilities can be confusing.

Another supplier might be Canare


-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
The NRA is offering FREE Associate memberships to anyone who wants them.


"It's a dog-eat-dog world out there, and I'm wearing Milkbone underware."
-- Norm, from _Cheers_

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Re: [Emc-users] WG: Re: WG: Re: axis and batch processing

[Chris Epicier]

Dear Ken



> To generate lots of debug messages:
>    In your.ini file section [RS274NGC] add
> the line
>       LOG_LEVEL = 999

I guess this is wat I was looking for! thanks!

>      
> Then the file emc_log will get a log containing the
> interpreter activity 
> regarding o-words, subroutines, etc. You probably don't
> want this 
> enabled when you are doing something useful because the
> file will be 
> very large.
> 
> I suspect that you will find that the file prefix is wrong.

I have some small files ready, that I generated to keep things simple but being 
able to produce the same mistake. I will be back to try and debug this when 
back in my workshop (about 1 week). 


> Put the log 
> up on pastebin and we can take a look at it.

What is the "pastebin"? Once I am there, I might put an external link to the 
log files, so the digest will be as small as reasonable possible. However, If 
later people try to look up matters, they will see a broken link.


> One neat thing you can do is load a file containing lots of
> subroutines. 
> If you have enabled LAZY_CLOSE in your ini file, you will
> then be able 
> to invoke the subroutines from the MDI.

This sounds like a very neat thing. From time to time I have to repeat just one 
subroutine (to date I load the individual files manually w/o sub endsub stuff). 
Then this will become extremel handy. Thanks for the hint!

greets

chris




  

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Re: [Emc-users] Scaling angular axis

[Andy Pugh]

2009/10/6 Jon Elson :

> I think the basic problem is that the encoder count is by necessity
> granular,
> and a lower INPUT_SCALE "magnifies" that granularity.

Is 'encoder.X.position-interpolated' inappropriate in this situation?

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Re: [Emc-users] Where to put controllers?

[Leslie Newell]

Hi Ian,

The signal lines are FAR more sensitive to noise than the stepper lines. 
It is virtually impossible to pick up enough noise on the motor lines to 
affect the motor. I don't think your Z axis problem was directly related 
to pickup on the motor wires. It is possible that there was some noise 
picked up and it was re-radiated in your control cabinet.

I always try to keep the signal lines as short as possible, especially 
in noisy environments.

Les

Ian W. Wright wrote:
> HI,
>
> I'm in the process of building a second little mill - this 
> time a stepper-driven gantry type and I'm wondering what the 
> pros and cons might be of different driver locations. On the 
> first mill I had all the controls in a big box under the 
> bench with heavy wires going to each motor but I'm wondering 
> now whether any advantage might be gained in this project by 
> positioning the driver cards adjacent to each motor. This 
> would shorten the cables carrying power to the motor but 
> would mean carrying signal cables from the parallel port 
> around the machine together with DC power wires to each 
> card. One reason for considering this is that, on my 
> previous machine, I had a problem with the Z-axis stepper 
> picking up interference from brushed spindle motors and so I 
> had to change to a 'universal' AC motor drive for the 
> spindle which was heavy and limited in speed. I tried 
> various methods of screening the Z-axis motor leads and put 
> ferrite beads over them but nothing seemed to work. As I'd 
> like to use a high speed spindle based on a DC motor on this 
> mill, I wondered if it might be easier to shield the 
> 'signal-in' wires rather than the power wires to the motor. 
> Any thoughts?
>
> Ian
> _
> Ian W. Wright
> Sheffield  UK
>   


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Re: [Emc-users] Where to put controllers?

[Andy Pugh]

2009/10/6 Ian W. Wright :
>  One reason for considering this is that, on my
> previous machine, I had a problem with the Z-axis stepper
> picking up interference from brushed spindle motors

If you really had enough energy coupling from the spindle motor wires
to the stepper wires to create false steps then something really quite
scary was going on.
The several amps at several volts that flows in the stepper motor
cables should be immune to all interference short of a nuclear EMP,
whereas the logic-level signals are very easily swamped by RFI (see
the discussions on pull-ups in the encoder thread)

I am no expert, and we do seem to have one who will probably give you
chapter and verse later in the day, but I would say that moving the
drivers to the motors was quite a bad idea.

-- 
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[Emc-users] Where to put controllers?

[Ian W. Wright]

HI,

I'm in the process of building a second little mill - this 
time a stepper-driven gantry type and I'm wondering what the 
pros and cons might be of different driver locations. On the 
first mill I had all the controls in a big box under the 
bench with heavy wires going to each motor but I'm wondering 
now whether any advantage might be gained in this project by 
positioning the driver cards adjacent to each motor. This 
would shorten the cables carrying power to the motor but 
would mean carrying signal cables from the parallel port 
around the machine together with DC power wires to each 
card. One reason for considering this is that, on my 
previous machine, I had a problem with the Z-axis stepper 
picking up interference from brushed spindle motors and so I 
had to change to a 'universal' AC motor drive for the 
spindle which was heavy and limited in speed. I tried 
various methods of screening the Z-axis motor leads and put 
ferrite beads over them but nothing seemed to work. As I'd 
like to use a high speed spindle based on a DC motor on this 
mill, I wondered if it might be easier to shield the 
'signal-in' wires rather than the power wires to the motor. 
Any thoughts?

Ian
_
Ian W. Wright
Sheffield  UK

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