Lathe conversion, spindle trouble <resolved>

All things related to the Centroid Acorn CNC Controller

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pep
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Lathe conversion, spindle trouble <resolved>

Post by pep »

Hi all,
First I'm new to the forum and calling out to you from the Netherlands. After an old but sound cnc lathe lost its brains I replaced it with ACORN. I'm just a hobby nerd and this was the first time I touched a VFD. So this was guaranteed an enjoyable steep learning curve. The lathe is a Baron Max and the old computer was a Fagor. About the main components: x and y servos are mitsubishi mr-j2. The spindle mitsubishi A500. Took a lot of figuring out how to connect and talk to the MR-J2 but works great now. Over all a very nice build quality and a great starting point for the Acorn. And Acorn is a great product! Successes so far: the x and z are alive and performing nice. Still need to compensate for a little backlash but the repeated accuracy is within 0,005mm. Also cooling water, gearbox indicators, spindle encoder, worklight, lube etc. is all working.

But now I got stuck and before I implement any further I would like to ask your opinions on how to proceed...

The things that bothers me:
- the spindle is not what it should be. I performed the bench test initially and that went well. I repeated it with the Acorn installed (with the VFD disconnected). Now the value of S500 that I read is too high, somewhere around 3V. This stops the bench test procedure. When I lie to acorn (sorry guys;-)) and tell that S500 returns 1,85V, the rest of the measurements are ok. So any tips on how to solve that would be very welcome. I had quite often the Acorn not responding and a power cycle then helps. But maybe some software got corrupted?

- then another thing that I think has to do with EMI. The VFD voltage that acorn delivers is wobbeling around between +/-0,2V. And this reflects in the RPM of the spindle. Sometimes sounds like Acorn is howling at the moon, wooowooowooowooo LOL. I got the shielding right I think, connected to earth at acorn side. In the cable layout I cannot optimize much more for separating all the cables. Also this was like how the cnc was origionally layed out. Would a little capacitor at the acorn output help out here or any other ideas?

cheers, Pep
IMG_0574.jpg
suntravel
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Re: Lathe conversion, spindle trouble

Post by suntravel »

Hi Pep,

iI would try to follow this here:

https://centroidcncforum.com/viewtopic. ... ing#p55178

Regards

Uwe
tblough
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Re: Lathe conversion, spindle trouble

Post by tblough »

Try a 100nF ceramic (non-polarized) capacitor across the Acorn analog spindle output and see if that helps. Make sure you are using twisted-pair shielded wire for the spindle oitput to VFD connection as well.
Cheers,

Tom
Confidence is the feeling you have before you fully understand the situation.
I have CDO. It's like OCD, but the letters are where they should be.
pep
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Re: Lathe conversion, spindle trouble

Post by pep »

Tnx for the suggestions! The cable is already a twisted pair and shielded, shield connected to earth on the Acorn side. Shielding on both sides to earth can provide a groundloop I think? Or not?
So the capacitor definetly will be the next move. Have to digg one up in the man cave... Will report back the effect.

Any thoughts on the result of the bench test at S500, or just ignore it?

Cheers, Pep
suntravel
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Re: Lathe conversion, spindle trouble

Post by suntravel »

pep wrote: Fri Dec 17, 2021 9:12 am Tnx for the suggestions! The cable is already a twisted pair and shielded, shield connected to earth on the Acorn side. Shielding on both sides to earth can provide a groundloop I think? Or not?
So the capacitor definetly will be the next move. Have to digg one up in the man cave... Will report back the effect.

Any thoughts on the result of the bench test at S500, or just ignore it?

Cheers, Pep
If the benchtest for the spindle is not done on the bench with nothing else connected, noise could be the cause for inconsistent readings....

Regards

Uwe
centroidsupport
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Re: Lathe conversion, spindle trouble

Post by centroidsupport »

pep, you stated "I had quite often the Acorn not responding and a power cycle then helps. But maybe some software got corrupted?"

This is almost always related to noise and is most often caused by an unshielded ethernet cable.

It's extremely unlikely to be related to corrupted software
Need support? READ THIS POST first. http://centroidcncforum.com/viewtopic.php?f=60&t=1043
All Acorn Documentation is located here: viewtopic.php?f=60&t=3397
Answers to common questions: viewforum.php?f=63
and here viewforum.php?f=61
https://www.centroidcnc.com/centroid_di ... _gear.html
pep
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Re: Lathe conversion, spindle trouble

Post by pep »

Okay, good to hear that, so no worries that acorn got corrupted by this. Yes not all the shielding was connected correct in the beginning when Acorn stopped responding . I used the ethernet cable that was in the set, and it is shielded.
Just popped in a capacitor and this improves the stability of the RPM a lot. No more howling wolves. Not completely stable but good enough to go with. In the lowest speed range set at 40 rmp it jumps between 40 and 41.

Will measure again in a benchtest tomorrow. And also see if I can calibrate the RPM a bit more.
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Re: Lathe conversion, spindle trouble

Post by cnckeith »

unrelated...the report show steps per rev on x and y set to 4095. looks like you have a typo if drive is setup for 4096
Need support? READ THIS POST first. http://centroidcncforum.com/viewtopic.php?f=60&t=1043
All Acorn Documentation is located here: viewtopic.php?f=60&t=3397
Answers to common questions: viewforum.php?f=63
and here viewforum.php?f=61
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martyscncgarage
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Re: Lathe conversion, spindle trouble

Post by martyscncgarage »

You do seem to have some noise. Check your logs, F7 Utility, F9 Logs, F1 Errors
Look for MPU PC Resends.
As Scott (CentroidSupport) mentioned, are you using the shielded cable that came with Acorn?


Excerpt from your log file:
12-15-2021 12:33:38 CNC12 Lathe v4.64
(4) 12-15-2021 12:33:38 9033 Reset Initiated, Press Reset to Clear
(4) 12-15-2021 12:33:41 4032 Reset Cleared
(4) 12-15-2021 12:34:06 5038 SPECIFIED SPIN SPEED < MIN SPIN SPEED
(4) 12-15-2021 12:38:40 5038 SPECIFIED SPIN SPEED < MIN SPIN SPEED
(1) 12-15-2021 12:43:07 Exiting CNC and shutting down machine (68)
(1) 12-15-2021 16:13:46 199 CNC Started
(4) 12-15-2021 16:13:51 944 MPU requested resend # 19
(4) 12-15-2021 16:13:51 946 PC resending # 899
(1) 12-15-2021 16:13:52 CNC12 Lathe v4.64
(4) 12-15-2021 16:13:53 9033 Reset Initiated, Press Reset to Clear
(4) 12-15-2021 16:13:53 944 MPU requested resend # 21
(4) 12-15-2021 16:13:53 946 PC resending # 1002
(4) 12-15-2021 16:14:15 4032 Reset Cleared
(4) 12-15-2021 16:14:18 5038 SPECIFIED SPIN SPEED < MIN SPIN SPEED
(4) 12-15-2021 16:22:05 9033 Reset Initiated, Press Reset to Clear
(4) 12-15-2021 16:22:08 4032 Reset Cleared
(4) 12-15-2021 16:24:04 944 MPU requested resend # 22
(4) 12-15-2021 16:24:04 946 PC resending # 1021
(4) 12-15-2021 16:24:14 5038 SPECIFIED SPIN SPEED < MIN SPIN SPEED
(1) 12-15-2021 16:49:45 4053 Select Auto Spindle, press CYCLE START
(4) 12-15-2021 16:52:23 5038 SPECIFIED SPIN SPEED < MIN SPIN SPEED
(4) 12-15-2021 16:57:18 944 MPU requested resend # 23
(4) 12-15-2021 16:57:18 946 PC resending # 1037
(4) 12-15-2021 16:57:20 944 MPU requested resend # 24
(4) 12-15-2021 16:57:20 946 PC resending # 1046


Also, as Keith mentioned, for a CNC Lathe your steps per motor rev do not look right
What kind of axis drives are you using? What is the encoder counts on the servo motors (assuming they are AC Servos)
Are they directly coupled to the ball screws? Belt reduction? What is the ball screw pitch?

From your report:
Axis Label Motor Encoder Lash Comp. Limit Home Dir Screw
mm/rev counts/rev. (mm) - + - + Rev Comp
1 Z 1.2487 4095 0.0000 1 1 0 2 N N
2 X 0.6244 4095 0.0000 1 1 0 2 N N
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
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martyscncgarage
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Re: Lathe conversion, spindle trouble

Post by martyscncgarage »

When you say you performed the bench test with spindle? You mean the automated spindle test?
YOu didn't have the VFD/Motor connected?
What is the min/max RPM?

Sure would be nice if you would take the time to provide the information requested in this post. More information will get you better suggestions in a timely manner:
https://centroidcncforum.com/viewtopic.php?f=60&t=1043
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
Mesa, AZ
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