X-Axis motors going opposite directions

[FrogLegs]

Help Please!
Was merrily cutting away yesterday and it looked like the x axis had skipped a bit. Shut the machine down quick before my parts were ruined. The gantry got out of square by quite a bit. After zeroing, and cutting power, it would jump skew about 1.5 inches. Re-squared it today by zeroing, loosening gantry bolts, then tightening up again. Cleaned and oiled the linear bearings. Pushed the gantry with the power off and it moved Ok.

Then tried moving x axis with the pendant and it immediately knocked out of square again. One motor is moving the gantry one direction while the other motor is moving the gantry the opposite direction. Tried single stepping the motors and they were moving in opposite directions. Over loaded stepper motors can do some odd motions so did one more check on the mechanics. Took the pinons off the two motor shafts. The bearings are smooth the whole length. Cleaned and inspected the pinions and racks. Turned the motors manually. All looks fine.

Reassembled and single stepped X axis. Motors went opposite directions and threw off my second squaring of the gantry.

Checked one more thing. The motors change direction when their homing switches are made. Maybe there is an errant homing switch signal. Checked at the switch. All good. Checked at the control box, still good. Since the switches are normally closed, only open in the zero position, wiggled the wires in between the switch and the box. No apparent short.

There is no apparent mechanical issue and no apparent wiring issue. So what would cause the two x axis motors to intermittently run opposite directions?

Thanks

StarLab 4x8
Stepper motors
Really big Hypertherm

[djreiswig]

Motor direction setting in Mach3 or CommandCNC. The A motor should have it's direction inverted from the X motor.

Direction wire issue at the motor or motor driver.

If it just skipped, I would suspect a wiring connection.

[adbuch]

Hi,
It sounds like a setting to me. You don't say which controller software you are using, but there is usually a setting for the dual gantry drive setups that allows for reversing the rotational direction of one of the Y motors so they work in tandem and not in opposition.
David

[robertspark]

If you are using Mach3, I have heard of and experienced occurrences where the profile becomes corrupted and mach3 looses its settings or part of its settings....

I have heard that this can happen if you exit mach3 without allowing it to shut down because it apparently writes information to the profile when the programme closes ..... why it would do a partial re-write and corrupt the file I'm sorry that is beyond my knowledge .... but it can happen as I've experienced it...... hence that is what the e-stop / mushroom button is for..... not the big switch on the wall unfortunately.

If you could post more information I'm sure someone could help, are you running Mach3, Mach4.... linuxcnc.... ??

It may be possible to contact the manufacturer and ask for a copy of their profile.... just load it and it "should" just run and work..... (in theory)..... but you will at least get the pins and ports settings straight away ....

[adbuch]

I have had instances where Centroid Acorn CN12 did similar things. Changed some of the settings on its own. This can be very frustrating. I run Mach3 on one of my cnc routers and have never had any problems whatsoever.
David

[weldguy]

I would guess its a broken wire or motor gone bad. To determine if its a motor/wire or software/driver issue just plug the left motor in the right and right into the left. If the problem moves to the other side look at your step driver or look for changed software settings, if problem remains on the same side its a wiring/motor issue.

[BTA Plasma]

Axis suddenly going haywire is a drive or wire issue. If one motor will simply not go one way that is a home switch issue. Call in if you need further assistance with your Star Lab. The number is on the front of the gantry.

[FrogLegs]

Info that should have been provided originally: It is a stepper motor table with a CandCNC ESP II-A driver box running Linux Command CNC Ver 1.2.1. Issue occurred both within a program, and running manually, both with the pendant and the PC.

Checked the configuration profile. Everything looked correct. Internal and external driver box cable connectors were checked and no issues found.

The idea to swap the motor cables was interesting. Swapped the two x axis motor connectors and the issue moved to the other x axis motor and stayed with driver #4. Can't run much because the gantry is getting rather skewed. Then plugged the Y axis motor into driver 4. Was able to run that motor more because it is a single motor. Found that in one direction, the motor was running the right direction. In the other direction, it also was continuing to run the same (wrong) direction.

Was hoping that this would be the type problem with a solution like "Hey dummy, you need to adjust the left whatzit" and I could be on my merry way cutting metal again. Problem appears to be at an electronic component or board level. Called Matt. Replacement part are being sent.

Thanks to all for help and advice!

[FrogLegs]

Bulltear send out a replacement G251-4 PCB. Swapped the board and the problem was gone. Cut parts yesterday.

Was tempted to swap the A2531 optocouplers on the original board to see if that was the issue. But at that point, it was idle curiosity and no time for that.
PH

[adbuch]

Glad to hear you've solved your problem.
David

[BTA Plasma]

Happy to help!!