Clearpath MCVC Spindle Motor Control - Solved (Mike R is an absolute legend)

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gMike
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Clearpath MCVC Spindle Motor Control - Solved (Mike R is an absolute legend)

Post by gMike »

Hi All,

I am looking to buy this motor to use for my spindle on an acorn board

https://www.teknic.com/model-info/CPM-M ... voltage=75

The Motor above uses PWM for its speed control which I understand is inline with the common VFD PWM

The other choice that I understand is not compatible with the acorn PWM spindle control is a step/direction motor like the one below.

https://www.teknic.com/model-info/CPM-S ... tage=75VDC

General Comments

I know for most machinists this spindle motor might seem unusual, however my end use is micro machining where light weigh power dense motors are the goal. My intention is to use rigid tapping and am planning there required 1:1 high resolution encoder.

The request!

Due diligence will get me only so far and is no replacement for experience, will the MCVC motor above give me trouble free milling and tapping with an acorn boards signal? The manual can be found at the link below, I believe the correct page is 109 (Bipolar PWM with inhibit) noting the input frequency range is 20-30khz

https://www.teknic.com/files/downloads/ ... manual.pdf

Many thanks in advance for the assistance and patience. I know questions of this type have been asked before but I'd like some more confidence the MCVC clearpath motors will work perfectly with the acorn tapping functions. (I want to mill rather than troubleshoot)

gMike
Last edited by gMike on Tue Sep 21, 2021 5:37 am, edited 2 times in total.
Richards
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Re: Clearpath MCVC Spindle Motor Control - Help Requested

Post by Richards »

Teknic sells an analog board (about $75) that converts Acorn's 0-10VDC to digital pulses that are compatible with the ClearPath non-SDSK servos. The problem that I experienced with both the DMM DYN4 servo and a non-SDSK ClearPath servo was "creep". Even when the Acorn was at 0-volts, the spindle slowly turned. That was fixable by using Acorn's outputs to enable/stop/start the spindle, but it was an unexpected problem that needed attention.
-Mike Richards
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Re: Clearpath MCVC Spindle Motor Control - Help Requested

Post by gMike »

Thanks Mike R,

So if I understand your post correctly you have successfully controlled a MCVC motor using the acorn signal with the only problem being the creep. As a follow up question did you try setting a deadband in the clearpath motor itself. I found the snip attached below on page 110 of the clear path manual at this link

https://www.teknic.com/files/downloads/ ... manual.pdf.

Is there a chance that could fix it or did you try that already?

Cheers...gMike
Attachments
Deadband.png
Gary Campbell
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Re: Clearpath MCVC Spindle Motor Control - Help Requested

Post by Gary Campbell »

Add the 0.1 microfarad 50v capacitor and the creep usually disappears.
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Richards
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Re: Clearpath MCVC Spindle Motor Control - Help Requested

Post by Richards »

gMike,
I use the MCPV-3421P-RLN model.

Thanks for the information on the dead-band setting. I've never used that feature.

Gary,
Thanks for the advice on the capacitor. I've never used that either.
-Mike Richards
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Re: Clearpath MCVC Spindle Motor Control - Help Requested

Post by gMike »

Ok great, so as best as I can see from the posts above the MCVC motors will work perfectly with the acorn PWM out.

One last clarification then:
- The maximum base frequency Acorn can work with is 24khz
- The clearpath needs an input frequency of 20khz to 30khz
- Does this mean I can set a base frequency to say 22khz and me comfortably within the envelope of both systems?

I am struggling a little on my first time around to make sure I have these items ok

Thanks...Mike
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Re: Clearpath MCVC Spindle Motor Control - Help Requested

Post by Richards »

I haven't tried PWM with a ClearPath motor. I'll have to hookup my MCPV servo and give it a try.

What I do when trying something out of the ordinary is to spend some time on a bench test. When I was experimenting with an AutomationDirect 120V VFD and a 3/4hp 3-shase motor, I bought a Harbor Freight digital tachometer for about $40 to verify the speeds of the motor. I used that tachometer with a ClearPath MCPV-3421P-RLN servo and Teknic's analog to PWM adapter.

I understand your hesitation in buying the ClearPath motor before you are certain that it will work using your available parameters. Teknic has a great test and return policy. If a motor doesn't work for your application, you can return it. Your only cost is shipping.

What I can do is to experiment with Centroid's PWM signal on one of my Acorns and the MCPV servo, along with trying different dead-band settings to see what happens. It might take a few days. (We have a large garden and we're in the middle of our "bottling" season, so the perishable produce takes precedence at this time of the year.)
-Mike Richards
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Re: Clearpath MCVC Spindle Motor Control - Help Requested

Post by Richards »

From a very quick scan of the Teknic manual, page 109 describes the FOLLOW DIGITAL VELOCITY COMMAND parameters. It looks like the motor will turn in one direction when the PWM signal is 0-50% and in the other direction when the PWM signals is 50-100%. The dead-band percentage ensures that the motor will completely stop at 50%. Are my assumptions correct?

After a quick scan of the Acorn's PWM signal, it looks like the cable to the relay board will have to have a wire cut. I have a spare Acorn board that I can configure to use without the relay board connected (so I don't have to cut the cable). It looks like Output 2 on the DB25 header and one of the ground lines from the DB25 header connect to Input B on the ClearPath cable. I'm unclear about how to configure the Acorn so that the S command controls the PWM signal. Do I simply turn on the PWM signal in Wizard? If the S command controls the PWM signal, which parameters do I set in Wizard for proper operation to get the PWM signal to control the motor's direction as well as its speed?

It looks like I will need to do the following to properly test the ClearPath servo using Acorn's PWM signal:

1. Connect both signals of ClearPath Input A to Acorn GND.
2. Connect ClearPath B+ to Acorn DB25 Output 2. Connect B- to Acorn GND.
3. Connect Enable+ to 5VDC and Enable- to Acorn GND.
4. Configure ClearPath to use FOLLOW DIGITAL VELOCITY COMMAND. Set dead-band to 5% initially.
5. Configure Wizard to use PWM for speed control. (I need detailed list of parameters to change)
6. Use Acorn's MDI commands to test speed and direction of the ClearPath motor.

To make this test as painless as possible, please post your list of configuration steps for both the ClearPath servo and for Acorn's Wizard. I'll study the manuals more after church today.
-Mike Richards
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Re: Clearpath MCVC Spindle Motor Control - Help Requested

Post by gMike »

Hi Mike R,

"Teknic has a great test and return policy." I live in Australia so the postage is more significant thought not a deal breaker

"What I can do is to experiment with Centroid's PWM signal on one of my Acorns and the MCPV servo" Woohoo!!, that's exactly the confidence I am looking for before I commit my precious workshop budget : ). This is a great community, really appreciate this!

"we're in the middle of our "bottling" season"...not hard to guess what you do for a living #jealous : )

"The dead-band percentage ensures that the motor will completely stop at 50%. Are my assumptions correct?" Yes, that's my understanding too

" I'm unclear about how to configure the Acorn so that the S command controls the PWM signal. Do I simply turn on the PWM signal in Wizard? If the S command controls the PWM signal, which parameters do I set in Wizard for proper operation to get the PWM signal to control the motor's direction as well as its speed?" I'm also unclear, there is not much commentary written about this, perhaps its obvious to the pros but not me. I PM'd the Tecknic rep to chime in but no sign yet, if I get an email I'll post here.

"To make this test as painless as possible, please post your list of configuration steps for both the ClearPath servo and for Acorn's Wizard." I am at the final stage of procurement so I can only put down my speculation
- Max motor speed = 6000RPM
- Max Spindle/Encoder Speed 10000RPM (via pulleys)
- Motor is the CPM-MCVC-2346D-RLN as linked above
- PWN dead zone @5% sounds right

I want to reiterate my thanks for helping with this problem, really appreciated!

Cheers...gMike
gMike
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Re: Clearpath MCVC Spindle Motor Control - Help Requested

Post by gMike »

Also just been researching and this seems bang on



cheers...gMike
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