Spindle Voltage Offset

All things related to the Centroid Acorn CNC Controller

Moderator: cnckeith

Post Reply
terrymcc
Posts: 61
Joined: Fri Nov 27, 2020 11:34 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: waiting on delivery
Location: Pattison, TX
Contact:

Spindle Voltage Offset

Post by terrymcc »

I am doing the initial start-up on a Mill Turn upgrade. It uses a Nowforever E-100 VFD. I have looked through the forum and see there has been a good bit on spindle accuracy but didn't see anything that seemed to line up exactly with my issue. CNC12 is set up with Max RPM of 5000 and Min RPM of 0. I have not tweaked the VFD frequency at this point. My initial results are attached. One of the main issues appears to be a .08V offset on the analog out. It is .050V at AN OUT of the Acorn when nothing is connected. There shouldn't be any ground loops as the wiring is a twisted shielded pair run directly from the Acorn AN OUT to the VFD AN IN.

As the data shows, at high RPM, .08 volts makes very little difference. However, at low RPM, it makes a big difference. Any thoughts on where this offset comes from and how to accommodate it?

I wanted to see if I can address the offset before trying to calibrate. I haven't seen a specific procedure on calibrating the spindle, but what I have gained from some of the previous threads is that you play with the VFDs Max and Min frequency to bring it closer. Is this correct?

When using a spindle encoder, why isn't the loop closed between the encoder and VFD?

Thanks for any help.
Attachments
Initial Spindle Cal Test.pdf
(215.19 KiB) Downloaded 9 times
martyscncgarage
Posts: 7131
Joined: Tue Mar 28, 2017 12:01 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: Yes
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: Yes
CPU10 or CPU7: Yes
CNC Control System Serial Number: none
Location: Mesa, AZ

Re: Spindle Voltage Offset

Post by martyscncgarage »

Me personally, I wouldn't get overly excited about your called vs. Actual. Your high and low are close. If you really want to TRY and get it closer, you have to experiment with the settings IN the VFD. Nowforever sounds like a Chinese drive. (Good luck with support and assistance)
Spindle Test.JPG
DO understand, Centroid Controls, Acorn included do NOT maintain spindle speed. That is, if the spindle is not running at the actual speed, it does not correct it automatically. The purpose of the Spindle encoder is to let the control know actual spindle speed and to slave the Z axis accordingly for rigid tapping, peck tapping, threading, and Constant Surface Speed in a lathe.

My .02 on the subject
Marty
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
Mesa, AZ
martyscncgarage
Posts: 7131
Joined: Tue Mar 28, 2017 12:01 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: Yes
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: Yes
CPU10 or CPU7: Yes
CNC Control System Serial Number: none
Location: Mesa, AZ

Re: Spindle Voltage Offset

Post by martyscncgarage »

martyscncgarage wrote: Wed Jan 13, 2021 12:00 pm Me personally, I wouldn't get overly excited about your called vs. Actual. Your high and low are close. If you really want to TRY and get it closer, you have to experiment with the settings IN the VFD. Nowforever sounds like a Chinese drive. (Good luck with support and assistance)

Spindle Test.JPG

DO understand, Centroid Controls, Acorn included do NOT maintain spindle speed. That is, if the spindle is not running at the actual speed, it does not correct it automatically. The purpose of the Spindle encoder is to let the control know actual spindle speed and to slave the Z axis accordingly for rigid tapping, peck tapping, threading, and Constant Surface Speed in a lathe.

My .02 on the subject
Marty
P.S. ALWAYS Post a link to the manual of the drive.....
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
Mesa, AZ
terrymcc
Posts: 61
Joined: Fri Nov 27, 2020 11:34 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: waiting on delivery
Location: Pattison, TX
Contact:

Re: Spindle Voltage Offset

Post by terrymcc »

martyscncgarage wrote: Wed Jan 13, 2021 12:01 pm
martyscncgarage wrote: Wed Jan 13, 2021 12:00 pm Me personally, I wouldn't get overly excited about your called vs. Actual. Your high and low are close. If you really want to TRY and get it closer, you have to experiment with the settings IN the VFD. Nowforever sounds like a Chinese drive. (Good luck with support and assistance)

Spindle Test.JPG

DO understand, Centroid Controls, Acorn included do NOT maintain spindle speed. That is, if the spindle is not running at the actual speed, it does not correct it automatically. The purpose of the Spindle encoder is to let the control know actual spindle speed and to slave the Z axis accordingly for rigid tapping, peck tapping, threading, and Constant Surface Speed in a lathe.

My .02 on the subject
Marty
P.S. ALWAYS Post a link to the manual of the drive.....
Thanks Marty. Yes, the VFD is what came on the original machine and is from China (as is the machine I think). I did play with the VFD settings and have it pretty much spot on at both ends and within 150 in the middle. That should be fine.

Continuing to learn and progress. The controls are soooo much better than the Mach mess that came on it.
martyscncgarage
Posts: 7131
Joined: Tue Mar 28, 2017 12:01 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: Yes
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: Yes
CPU10 or CPU7: Yes
CNC Control System Serial Number: none
Location: Mesa, AZ

Re: Spindle Voltage Offset

Post by martyscncgarage »

I have to agree with you the Centroid controls are much better and having the hardware and software come from Centroid is a big plus!
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
Mesa, AZ
Post Reply