Centroid Community CNC Support Forum

I think we have a bad Acorn controller. It was purchased about 2 years ago by the high school FIRST team for our FrankenRouter build. We just got it running for the first time in January of this this year and have not been able to make a single part for our robot as the Z axis has lost position, drifts upward. I am an automation engineer familiar with motion controls and proper wiring with respect to grounding, shielding keep power wires away from signal wiring etc. I also have my own homebuilt CNC that I recently converted from Mach 3 to an Acorn and it works flawlessly.

On the school machine I used the 24vdc drive connectors with 2K dropping resistors because I tend to stay away from 5vdc signals on industrial equipment. However I also made up a D25 connector for the Z axis at 5vdc and it misses steps there as well. We have 4 identical axis motors and 4 identical Leadshine drives. Moving the motors and the drives around the problem only occurs when using the Z output. X&Y work flawlessly and the X and Y axis outputs run the Z axis flawlessly too. So the only common with the problem is the Z axis output from the Acorn. I have also tested all the system voltages and the Acorn is powered by the power supply that came with it and it runs nothing else. That power is also fed from a voltage regulating UPS so power spikes from the spindle or axis drives are extremely unlikely.

So at this point the only part that hasn't been swapped/replaced is the Acorn itself. How do we proceed?

Which leadshine drives are you using? See my Bridgeport Interact build thread:
viewtopic.php?f=60&t=11161&start=20

I had problems with Leadshine H2-2206 drives not liking the 2.5us pulse, I changed parameter 968 to a value of 30 to give a 12us pulse and that made everything run just fine, might be worth just trying that, its a quick thing to adjust. Also the earlier Leadshines don't seem to like signal voltages over 5vdc even though the manuals say 5-24vdc is okay.

correct, connect most leadshine drives to the DB25 5 volt connection on acorn. see the many Leadshine to Acorn hookup diagrams here.
https://www.centroidcnc.com/centroid_di ... =leadshine

post a fresh REPORT.zip

post photos

post a sketch of how you have it wired.

The parameter setting was the problem! Changed it from 300000 down to 100000 and the machine is working fine now.

Still have one issue I don't understand. picking up the part location Acorn keeps applying a tool radius offset to the origin of a part. Does Acorn get the tool radius from the tool diameter in a program? I post from CamBam which I have been using for years and I have never seen this happen before. How do I prevent this from happening?

Can you walk us through how you are setting the part origin on the stock? Are you using a touch probe or other method?

Are you applying tool diameter offsets in CAM, in the CNC12 Tool Library, or both?

Garyhlucas wrote: ↑Tue Mar 11, 2025 7:21 am The parameter setting was the problem! Changed it from 300000 down to 100000 and the machine is working fine now.

Still have one issue I don't understand. picking up the part location Acorn keeps applying a tool radius offset to the origin of a part. Does Acorn get the tool radius from the tool diameter in a program? I post from CamBam which I have been using for years and I have never seen this happen before. How do I prevent this from happening?

please start a new thread for a new subject.

post a fresh report.zip and the offending g code program.

lookup cutter compensation in the CNC12 operator manual.