Re: [Emc-users] spindle encoder hardware for the Sheldon

[Gene Heskett]

On Sunday 11 September 2016 13:46:06 Chris Albertson wrote:

> Gene,
>
> I would not use JB Weld on a part that roads and vibrates and has oil
> around it.  If you need a piece of metal to index trigger with, I've
> seen lots of simple ways to do it.  I'm planning on adding this to my
> lathe and mill some months from now as I'd like the ability to cut
> threads.
>
> 1) Drill a small hole in the shaft, You should see a trigger on both
> edges of the hole.  Note that this is the same as making a "bump" of
> 355 degrees length
>
> 2) use an existing keyway just like #1 above
>
> 3) Replace a small allen head set screw in a gear with a larger hex
> head bolt and index off the bolt head
>
> 4) Paint stripe(s) on the shaft and use an optical encoder (an IR
> transmitter/Receiver sees the change in reflectance.)
>
> 5) Drill a small hole in the gear and have the sensor look through the
> hole, looking parallel to the shaft.   Or (5b) place a small bolt and
> nut in the hole and index off the bolt head.
>
> 6) don't like this but,... cut a piece off one of the gear teeth.  The
> "missing" pulse is your index
>
> 7) I found some really good optical encoders on eBay for $15 to $20.
> They look like motors with a cylindrical body and a shaft and lead
> wires coming out of the body.   They have 100 to 600 pulses per
> revolution.  I think they were intended for servo motors.
>
> On Sun, Sep 11, 2016 at 9:13 AM, Gene Heskett  
wrote:
> > Greetings all
> >
> > When making the alu mount for these hall devices, I see ack the
> > specs they aren't that sensitive for distance from the gear as long
> > as its under 3mm's. So I am contemplating cutting out a mount whose
> > face is curved to match that huge but only 60 tooth according to
> > what parts lists I have, gear that is the backdrive gear on the
> > spindle when the backgear is engaged. And milling a flat spot wide
> > enough and deep enough that one of these hall devices would sink
> > into, and that would protect the hall device should temp effects
> > result in the gear actually touching the alu of the mount.  If they
> > are close together but half a tooth out of time, it doesn't seem to
> > me the arc vs gear accuracy would be all that critical. An arc,
> > something in the 6 inch diameter range looks about right.   Is there
> > a proximity effect when two of these are less than an inch apart?
> >
> > If I can mount it offset, effectively putting the center of my 1/2"
> > thick concoction on one edge of this gear, can I jb weld a piece of
> > ferrous in line with a gear tooth, and file it flush with the tip of
> > the tooth?
> >
> > The question about the jb weld is driven by this gear having a 65+
> > yo coat of dried, or wet oil on it, so the jb weld might fall right
> > off.
> >
> > So would a good washing with acetone be good enough, or do I pay
> > hazmat fees to get some mek into my possession?  Or grind/file the
> > end of that tooth shiny and then wash well with acetone?  That
> > sounds easier if I can keep the filings cleaned up.
> >
> > That ought to work as an index generator if there is room in the
> > bowels of the head casting to clear one tooth 1/8" wider than the
> > rest. And it would be an all in one piece setup.
> >
> > Thanks everybody.

All good ideas Chris, making me think. Thanks. The goop is curing now, 
but if this blows up, they are all suitable substitutes. The drilling a 
hole idea, but move it to the edge of the rim and bend the leads of one 
of these to make it face the side of the gear should also work.

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)
> > Genes Web page 
> >
> > 
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> > 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)
Genes Web page 

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Re: [Emc-users] spindle encoder hardware for the Sheldon

[Gene Heskett]

On Sunday 11 September 2016 13:05:59 Andy Pugh wrote:

> > On 11 Sep 2016, at 17:13, Gene Heskett  wrote:
> >
> > that would protect
> > the hall device should temp effects result in the gear actually
> > touching the alu of the mount
>
> How hot do you expect the gear to get to expand by 3mm?

Chuckle. I did find out how hot my piece of alu could get if it rubs, 
burn you fingers hot! This occurred after I thought it had clearance but 
as I tightened down the mount screw it tipped fwd about 30 thou and did 
a nice job of polishing it with the gears teeth. So I undertook to sand 
it where the cast grain had marked it, and keep sanding until it still 
cleared when tightened.  Then I washed up the right rim of the gear, and 
ground about 3/8" of steel screw square, and slightly narrower than a 
tooth, gave it a coat of Go-2 (aka goop) and clamped it in place with 
the top flush with a tooth, and a few thou narrower than a tooth so 
(hopefully) the backgear will not knock it loose.  That was a good place 
to quit & let the Go-2 cure till tomorrow.

I am down to about 1.5 usable 1/4" SC end mills, and found some on ebay, 
and I getting low on alu scraps & found a 20 lb kit of all 7078-T6 & 
bought that too. Ack the shipping notices I may as well loaf till about 
Wednesday, which should start to trickle in the rest of the stuff I need 
for the Z screw. Some rubber bellows type boots so I'll know what size 
of cups I need to make to fit those.  Spacers, etc will have to wait 
till I've found a suitable piece to make a new table insert for my 
bandsaw.  That was never table surface high, and it let a small piece 
tip into the blade which crushed the plastic OEM insert, and the piece 
visited all 4 walls of my little shop building but couldn't be found. So 
I closed it up for the night, and when I pulled the door open the next 
morning it rolled out onto the shops front deck.  Go figure. ;-)

BJ is sending me enough stuff to rebuild the toy lathe, so eventually I 
hope I can get back to making stuff for the Sheldon on it.

And I finally figured out what that 6" cover on the left face of the 
Sheldon's stand is for.  The only way you can change the 2 upper drive 
belts is to take off the belt on the 4 step pulleys, remove the upper4 
step pulley, undo the screws holding the double pulley, then drive the 
shaft out thru that hole far enough to uncouple the dual pulley, take 
the bearing caps off both ends of the spindle and lift it out, belts, 
pulley, and all. I might have to rig a sky hook for that. Belts run with 
a rumble, backing damage I expect as they were loose enough the backs of 
the belts have worn a grove in the casting lip where the bed and left 
foot meet.  Just one more thing I'll have to do at some point. :(

By that time, another of those 1kw induction modules should arrive.

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)
Genes Web page 

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Re: [Emc-users] spindle encoder hardware for the Sheldon

[Andy Pugh]

> On 11 Sep 2016, at 17:13, Gene Heskett  wrote:
> 
> that would protect 
> the hall device should temp effects result in the gear actually touching 
> the alu of the mount

How hot do you expect the gear to get to expand by 3mm?



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[Emc-users] spindle encoder hardware for the Sheldon

[Gene Heskett]

Greetings all

When making the alu mount for these hall devices, I see ack the specs 
they aren't that sensitive for distance from the gear as long as its 
under 3mm's. So I am contemplating cutting out a mount whose face is 
curved to match that huge but only 60 tooth according to what parts 
lists I have, gear that is the backdrive gear on the spindle when the 
backgear is engaged. And milling a flat spot wide enough and deep enough 
that one of these hall devices would sink into, and that would protect 
the hall device should temp effects result in the gear actually touching 
the alu of the mount.  If they are close together but half a tooth out 
of time, it doesn't seem to me the arc vs gear accuracy would be all 
that critical. An arc, something in the 6 inch diameter range looks 
about right.   Is there a proximity effect when two of these are less 
than an inch apart?

If I can mount it offset, effectively putting the center of my 1/2" thick 
concoction on one edge of this gear, can I jb weld a piece of ferrous in 
line with a gear tooth, and file it flush with the tip of the tooth? 

The question about the jb weld is driven by this gear having a 65+ yo 
coat of dried, or wet oil on it, so the jb weld might fall right off.

So would a good washing with acetone be good enough, or do I pay hazmat 
fees to get some mek into my possession?  Or grind/file the end of that 
tooth shiny and then wash well with acetone?  That sounds easier if I 
can keep the filings cleaned up.

That ought to work as an index generator if there is room in the bowels 
of the head casting to clear one tooth 1/8" wider than the rest. And it 
would be an all in one piece setup.

Thanks everybody.

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)
Genes Web page 

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Re: [Emc-users] touch probe

[Gene Heskett]

On Saturday 10 September 2016 20:50:10 Jon Elson wrote:

> On 09/03/2016 08:47 PM, Chris Morley wrote:
> > motion.feed-inhibit would be the one to use.
> >
> > only (maybe) homing and synch moves are un fazed by it.
>
> This appears to be a new feature in 2.8 or so, my older
> version doesn't have this pin, but it does have
> motion.feed-hold, so I used that.  So, when the probe is in
> use, a loss of valid signal from the probe causes a feed hold.

I just checked, I have both in the latest 2.7.7-sim, and in the 2.8 pre's 
I am cutting things with.  No clue when it appeared.  Better question 
might be "what is the difference in how they work?"

> Anyway, I got the thing working!  It seems this probe has a
> rather large deflection of about .008" with a 100 mm
> stylus.  I'm going to get a shorter stylus, as the entire
> thing is an awfully long stack, and the whole idea is to be
> able to measure not only X and Y, but length, too, so having
> to move the knee defeats the purpose.

Am I mistaken, ISTR you had a motor on the knee, Jon. I'd imagine a 
method to link that to the quill has been worked out by now so that it 
just displayed the total z. Stiction might be a problem, preventing good 
backlash measurement for compensation, but if lubed in the last 48 
hours, I'd have to assume zero backlash.

Side comment, having bought a gallon of Mobil Vactra iso 68, and finding 
I can't buy an oiler with a pump in it that still works a week after 
being filled with Vactra, it isn't always stiction free for a z move 
unless its been well soaked at the top of the gib, and the head (or 
knee) run up and down a couple times to distribute it.  Is Vactra iso 68 
the best oil for post or knee lube?

Or would something like STP be a better lube for posts and knees? It at 
least doesn't dissolve the valve seat for the one way ball valve in the 
pumper of an oiler.  I purposely bought one whose ball seated directly 
against the coned bottom of the pumper cup.  Brought it home & filled it 
up with Vactra, checked how it pumped, it worked just fine. The next day 
I picked it up and the pumper was already toast. Apparently the piston 
seal was something vactra liked really well.

If someone knows of a pumper type oiler that Vactra can't destroy, I am 
all eyes. I must have $50 in oilers sitting around, effectively brand 
new and totally useless.

> I did find that the chain of logic is pretty slow.  I probed
> at 1, 5 and 10 IPM, and saw a definite shift in the
> measurement as speed went up.  There can't be more than 1 ms
> delay in the FPGA, and the digital inputs are sampled at 1
> ms, so I'm not sure I understand where this is coming from.
> 1 IPM is 1/60th inch/second, and I have 20,000 counts/inch
> on X and Y, so that is 333 counts/second.  Given a couple ms
> delay, that is just a couple encoder counts + or -. But, I
> was seeing a change of .011" when I went from 1 IPM to 10
> IPM.  (I got a shift of .003" at 5 IPM.)  With a
> double-touch probing routine, it is not too slow to make the
> final touch at 1 IPM.

I think my last version of my pcb hole finder, using electrical contact 
to detect it, runs the final touch at .5 ipm, but the backaway to make 
the slow move is only 5 thou. And its generally repeatable to under a 
thou on average. I can etch a pcb on the toy, finishing up that side by 
running the hole drill file about 40 thou into the board, turn it over 
and etch & drill the other side, pull it back out of the pallet, and I 
cannot detect a step where the drill stopped in the middle of the pcb 
thickness, then came in from the other side with a very strong glass.  I 
did it that way after finding the micarta pallet, if the drill went 
thru, raised a nearly un-detectable ridge around the hole that pushed 
the 2nd side of the board out of flat by 2 or 3 thou.

> I probed both sides of a gauge block to try to determine the
> effective tip diameter.
> When I compensated for the .008" deflection to trigger the
> probe, calculations worked out for the effective tip
> diameter.  The tip appears to be smaller than the measured
> diameter due to the deflection that is needed to activate
> the probe.  (The whole reasoning behind Blum's design is to
> make the deflection to trip it the same from all
> directions.  Apparently, the classic 6 balls and 3 rods
> Renishaw probe has a 3-lobed sensitivity pattern with large
> peaks and valleys.  Blum claims they get 1 um variation in
> the distance to trip the probe from any direction in the XY
> plane.)
>
Whats the amplitude of those peaks and valleys.  More than a thou?

I'm obviously thinking in terms of diminishing returns per dollar.

> Once all this settles down, I will make edge finding probe
> routines that set the XY zero for any of the 4 corners of a
> part, and also sets the Z of the top of the part.
>
> I made an adapter from the FPGA board to the CNC control,
> and it has some flaky contacts, so I may remake the whole
> thing (it is just 3 LEDs, 5 resistors 

Re: [Emc-users] Plasma Torch Height Control

[John Thornton]

Does is have connections to measure the tip voltage?

JT

On 9/10/2016 8:32 PM, Alexander Brock wrote:
> On 09/10/2016 01:21 AM, John Thornton wrote:
>> What kind of plasma torch do you have?
> This one:
>
> http://www.stamos-welding.com/s-plasma-125h
>
> Best Regards,
> Alexander
>
>
>
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>
>
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