Jogging lathe Z axis moves in the same direction irrespective of jogging direction

[aziz76]

Greetings,

New user here and my first post. I have a Centroid Acorn unit up and running on a Lathe I converted using Clearpath servos. I tested movements on both axis, and homing both axis work perfectly most of the time. However, it has happened 3 times so far that after homing, I try to move the Z axis away from the home position using the MPG and it moves in the wrong way. Rotating the MPG wheel in the opposite direction results in the same move in the same direction. It does not stop for the home switch either which I have on adjustable arm so it just pushes it out of place. I have to then reset CNC12, and then things work correctly again.

Edit: I am using a C86ACCP board to connect the servos.

I am not able to figure it out. It works 99% of the time without issue. But this did happen on three occasions and has caused me concern. I would appreciate any help.

Cheers

[tblough]

I would check your wiring and connections on the direction signal between the Acorn and drive.

[cnckeith]

2nd what tom said.. sounds like the clearpath is getting the step signal but not the direction signal

[aziz76]

Thank you for that. I did make my own cables, its possible I screwed up somewhere there. I will check it.

Cheers

[tblough]

Since it's intermittent, I suspect a broken wire or loose connection. What kind of wire did you use for cables? I prefer servo rated cables (rated for constant bending and twisting). These are usually much higher strand count (30-50) vs regular wires (10-20).

[aziz76]

Hi Tom,

I’m using the cables supplied by Teknic. I just made two short lengths for inside the enclosure going from the C86ACCP to the bottom panel of the enclosure. I got some extra and cut and crimped on new molex connectors on one side.

I am trying a new cable right now going straight from the C86ACCP to the servo, bypassing my in-enclosure cable. So far so good. I need to test some more since it doesn’t happen every time.

[aziz76]

So I used a brand new cable (unaltered from Teknic) connecting directly to the C86ACCP.

I thought it was ok as I managed to do all my tool offsets, constantly moving the machine around with MPG. But just now it did it again. The DRO shows the Z axis moving in the correct direction but the servo is moving in the opposite direction.

Would appreciate any ideas.

[tblough]

Swap the cables between Acorn and the drives with Z and X at the Acorn. If the problem stays with Z, you have an issue with the Acorn. If the issue moved to X, swap the cables back at Acorn and switch them at the drives. If the problem is still at Z, the problem is the cable.

If the problem moved to X, switch the cables at the drives back. Now switch the cables from the motors to the drives at the drives. If the problem stays at Z, then the problem is in the drive.

Repeat this process with the cables at the motor ends, and finally swap the motors themselves until you locate the problem.

Substitution of known good components in a systemic manner is a basic troubleshooting skill.