On 7/30/23 02:29, John Dammeyer wrote:
Gene,
I think you are misreading the data sheet. The 115K baud is for setting up
the unit. Ie. Pulses per rev. Once that's done the serial isn't used
anymore.
That didn't stick out very well in my skim read, thanks. That leaves
the 8 bit resolution which I a guessing from the squiggles of the wheel,
are repeated at 5 per revolution with the index being geared to the
synch point between the two patterns. We commonly use a 1 kliohertz
servo loop, and if that A/D internal conversion is done at that rate or
higher, the result will be essentially the same as direct optical.
I only use PID's in one machine here, the G0704, and have found that
generally, the are a solution looking for a problem to solve that in the
stepper world does not exist, particularly if the steppers are actually
stepper/servo's. They put the PID to good use because their control is
directly tied to the src of the problem..There the error signal can and
is used to control the magnitude of the motor current on a cycle by
cycle basis. If the motor hasn't gotten into position, the error rises
but is subject to a time limit as to how hard it can hit the motor,
resulting in an alarm output that I tie into the e-stop, this only
happens if the motor hits the immovable object. It can run into a
stationary chuck jaw on my sheldon, see the error at 5 ipm movement, see
the lockup and shut down linuxcnc which shuts down the psu's as all that
in tied to F2 state, the carbide chip in the tool is not damaged and no
mark is made on the chuck jaw, The driver itself drops power to the
motor even faster, so the spring in the z drive bounces back about 5
thou. It takes that powerdown to reset the driver anyway, so it all
Just Works.
And that has never occurred in actual operation, just in my testing by
purposely running it into the stopped chuck.
The Sheldon and the 6040 mill both feed the stepgen back to motion, and
a missed step would be a disaster, The 6040's Z & B are 3 phase
stepper/servo's, XY are plain old oem steppers driven by 2m542's. That
B drive has worked so well on the 6040 that I've I've ordered stuff to
make one like it for the G0704. The BS-1 clone's motor was burned up by
the new atpid and was both too big and too heavy for the G0704 and while
accurate, was also slow at about .5 rpms. The B axis I made for the 6040
can do well within a degree, and do it at 400 revs, is a 3nm 3phase
driving a 5/1 worm which drives the chuck. That honking heavy spindle is
lifted effortlessly by a 1nm 3phase. The OEM Z failed to lift at 10% of
the xy speeds of around 200 ipm.
I use what works.
I had two US Digital opticals on my DC servo's and they were crap. I
switched to CUI units and all my problems went away
They should have just worked. But the $$ and mounting scared me off. The
ultra cheap ($22) for the last one I bought, which has never been
installed, the coupling failed and I replaced it with 2 layers of shrink
tubing, which has worked, and continues to work, year after year for me.
The one I bought to get the coupling is still in the box.
One has to assume the data sheet is correct when they say 8000 RPM with 2048
PPR. The 115k Baud has nothing to do with that.
Depending on where you put it, 8000 might be too slow. That $22 Omron
1000 ppr is rated to 6k. But it came out of the box balanced and does
not have enough swing to drive a 5i25 encoders single ended input, so
there's a pair of rs485 translators in the cable making its low voltage
balanced output into a 5 volt rail to rail signal. Works at 21k revs.
The gear ratio in high gear in the G0704 is about an odd tooth over 7/1
in high gear or 14/1 in low gear. And I can bang that 90 volt 1hp motor
with 125 volts and 18 amps. I'm amazed I haven't chewed up the nylon
gears rigid tapping with it.
In either case, I'll likely set this encoder up for 200 PPR so that even
with micro-stepping I really still don't care for higher resolution since I
have a 25:1 planetary drive after the motor. Assume I run the motor at 600
RPM max speed. That's 10 RPS or 2000 pulses per rev or 20,000 with 10:1
micro-stepping. But wait... 600 RPM divided by 25 is 24 RPM or 0.4 RPS so
2.5 seconds to turn one revolution.
At 200, you may discover quatization noise that limits a PGain. My first
optical for the G0704 spindle was a 66 slot brass disk, aka 264 edges
per rev. quantization error drove the spindle wall to wall and made it
noisy, like it was eating up the bearings in the head gears. The disk I
made came loose and ate the opto's, which is when I rigged the Omron.
Now its so quiet, with 5x higher PGain, that I have to look at it to
verify its turning if set below 500 revs. It was all electronic noise
from too low an encoder count.
I even cheat on the gear change by running the motor at about 20 rpms if
its not fully in gear, so I can be running at full song, reach up and
change gears because the motor is down to 20 revs by the time I've
turned the knob 2 degrees allowing the flat faced gears to mesh as they
meet turning slowly, and the motor speed is restored when that speeds
gear tally switch closes in the last 2 degrees of the knob motion, saves
stopping the spindle and grabbing it by hand to turn it to mesh the
gears again. :o)>
I'm thinking that if it takes 1 turn to release a TTS holder that's still
2.5 seconds. Faster than me with a couple of wrenches. And 25 seconds for
10 turns to release an R8 holder. Also faster than me mucking with the nut.
Unless I would use an electric drill to spin it loose. But then think of
the process.
1. Pick up two wrenches and loosen draw bar.
2. Put down wrenches.
3. Pick up portable drill and spin draw bar. Now maybe impact drill could
do both.
4. Once 10 turns are complete catch R8 tool.
Twenty five seconds for it to be done automatically is actually not so bad.
John
I know, I've been thinking of doing something similar with mine. But I'm
getting lazy in my dotage. And playing with 3d printers too.
-----Original Message-----
From: gene heskett [mailto:ghesk...@shentel.net]
Sent: July 29, 2023 10:37 PM
To: emc-users@lists.sourceforge.net
Subject: Re: [Emc-users] Drilling holes in the back of a stepper motor
On 7/30/23 00:12, John Dammeyer wrote:
Hi Gene,
Best answered with the data sheet.
https://www.cuidevices.com/product/resource/amt11.pdf
A Capacitative device. Not a hall effect. The capacitative may be faster
than a hall. The reason I'm anti hall is the time lag in the hall world
due to the time it takes to do the A/D conversions, which in turn means
the hall encoded setup moves in jerks depending on the speed of that
conversion. The 42C series of small motors, seen as ideal for a 3d
printer, are a disaster because they don't move step by step but jerk by
jerk, frequency of jerk determined to the speed of the A/D. Optical can
determine where the motor is and which direction its turning from any
edge of either A or B signals. At sufficient microstep divisors they can
move quite pretty smoothly. I'd assume this time lag in less for the
capacitative, but at the same time there is the Nyquist effect but the
capacitative conversion is simpler, but the serial output still enforces
a lag in the data stream. Only optical, which at higher and fixed
resolutions is instant. The question remains then "is capacitative fast
enough". And that IDK. The 115 kilobaud output says no to me. That
alone would make me go shopping for a ABI encoder.
But I'm known to be picky. That's an optical $22 Omron 1000 ppr on the
back shaft of the 1 hp in my g0704. With the gear ratio being
switchable, and that encoder rated for 6k revs, but I watch spindle revs
in the tach display. Top spindle is 3k revs. So times a hair over 7100,
its seeing motor revs of nearly 21k revs at full song and not missing a
beat for about 5 years now. Scale for high gear is a hair over 7100 per
spindle rev. I don't use the index, that is generated by a screw glued
to the spindle going by an ATS-667 hall effect. That has its own
direction problem I'm not smart enough to fix. Someday...
Not cheap in Canadian $.
https://www.digikey.ca/en/products/detail/cui-devices/AMT113Q-
V/4835229
John
-----Original Message-----
From: gene heskett [mailto:ghesk...@shentel.net]
Sent: July 29, 2023 9:02 PM
To: emc-users@lists.sourceforge.net
Subject: Re: [Emc-users] Drilling holes in the back of a stepper motor
On 7/29/23 22:36, John Dammeyer wrote:
Here's my solution. Drilled and milled 0.065" aluminum. Two counter
sunk
holes in the back. The modified flat head screws epoxied in serving
as
threaded studs. Then followed standard CUI installation and alignment
instructions.
Now to interface to it and write software to capture the motion and
position
John
Just one question John, is that encoder optical, or hall effect?
Optical is real time, hall effect is not.
-----Original Message-----
From: Curtis Dutton [mailto:curtd...@gmail.com]
Sent: June 26, 2023 6:28 PM
To: Enhanced Machine Controller (EMC)
Subject: Re: [Emc-users] Drilling holes in the back of a stepper
motor
On a past life before I started using servos I had attached encoders
to
my
steppers to stop the machine when steps were missed. I used us
digital
encoders that came with adhesive backed mounts from the factory.
They
worked swimmingly. I still have one in the "spare parts" room. The
encoder
is still securely attached over 10 years later. "double sided tape"
essentially woked very well.
On Mon, Jun 26, 2023, 3:11 PM Todd Zuercher
<to...@pgrahamdunn.com>
wrote:
I was just about to suggest gluing the thing on. You beat me to it.
Todd Zuercher
P. Graham Dunn Inc.
630 Henry Street
Dalton, Ohio 44618
Phone: (330)828-2105ext. 2031
-----Original Message-----
From: Roland Jollivet <roland.jolli...@gmail.com>
Sent: Monday, June 26, 2023 1:17 PM
To: Enhanced Machine Controller (EMC) <emc-
us...@lists.sourceforge.net>
Subject: [Emc-users] Drilling holes in the back of a stepper motor
[EXTERNAL EMAIL] Be sure links are safe.
You have such a large flat surface area there. Design an encoder
mount
plate of similar size where the end result is also has a flat
surface.
Rough and clean the back of the motor up, then use a decent
polyurethane
adhesive to bond it on. During the setup you could use a jig to keep
it
concentric with the shaft.
Design it in such a way that you can still replace the encoder if
need
be.
Roland
On Sun, 25 Jun 2023 at 05:31, John Dammeyer
<jo...@autoartisans.com>
wrote:
I want to add an encoder onto the back of this stepper motor. I
can
install either a US Digital or a CUI since both mounting flanges
can
extend out near the edges of the back mounting plate.
Is there any reason I can't clamp the motor in a vice and pop in
two
holes
and tap them with a bottom tap at the spacing of the mounting
flange?
John
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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, 1940)
If we desire respect for the law, we must first make the law
respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/>
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Emc-users mailing list
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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, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/>
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
_______________________________________________
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, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/>
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