Help Identifying Problem

[gordread]

I've been working with NextWaveAutomation to identify a problem with my 10 year old Shark HD Pro+. Over the last several months one of the axis (the one that moves the gantry back and forth with respect to the table, I call it 'x', but the default is 'y').

The problem is that the machine will start moving erratically in mid program, in the 'x' direction only. Meaning, it stops, even though the controller program shows that it is still changing, or it actually moves in the opposite direction that it should be. All the while it makes a horrible grinding noise.

I shipped the controller to NextWave, and they replace the controller for that stepper, but they could not actually replicate the problem.

Since I got the controller back I have the same intermittent problem. I have taken the whole deck apart, made sure that the screw was tight in the sockets, and that nothing was slipping. The only thing that I can think the problem still might be is the actual stepper motor itself.

Does anyone have any other ideas? Something I might be missing? Anything else to check? I can't ship the machine to NWA because I'm in Canada and if I have to ship it, I might as well just buy a new machine. At this point I don't mind spending some cash trying things on my own, because I really don't want to drop $5k (or more) on a new machine.

Any thoughts will be greatly appreciate. TIA

Gordon

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[he1957]

IIRC the X and Y motors are the same?

Interchange the wiring (or motors) and see if the problem moves to the other axis.

[awerby]

It sounds like a grounding/shielding issue; Radio-Frequency Interference causes erroneous signals like your motors seem to be picking up. Does this happen when the spindle is on, but not otherwise? Do you have good grounding on the system as a whole? Stepper motors themselves rarely go bad; issues with their misbehavior are almost always the fault of something else.

[gordread]

IIRC the X and Y motors are the same?

Interchange the wiring (or motors) and see if the problem moves to the other axis.

I will do that. When I've switched the wires in the past, the problem went away, but I didn't run an actual job, just jogged the machine. I will switch the wires and actually run a long job and see.

[gordread]

It sounds like a grounding/shielding issue; Radio-Frequency Interference causes erroneous signals like your motors seem to be picking up. Does this happen when the spindle is on, but not otherwise? Do you have good grounding on the system as a whole? Stepper motors themselves rarely go bad; issues with their misbehavior are almost always the fault of something else.

It is intermittent. I've never actually tried it with the spindle off. I don't have any loose wires or anything and the power runs through the controller, which is grounded by a ground plug (north american three prong plug).

Is there something else I should be looking for for grounding issues?

[he1957]

If the problem goes away after you've switched the wiring, look for a wiring problem. If there are connectors (of any type), check the mating and wire terminations. If you have a multi-meter, check the resistance between the end to end wiring as best you can (with the connectors in series between the measurements).

You are looking for high resistance on one (or more) wires between the end points, caused by either the connectors, wire terminations on the connector pins or bad connections at the extremities at either end.

IIRC, these machines had a 4 pin plug/socket arrangement on the control box going to each axis motor. There could be a bad solder joint on a socket on the back panel of the control box (accessed by opening the cover). Be very careful of any high voltages and if you are not comfortable with doing this contact a qualified technician/electrician.