Problem with the Z-axis motor

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Hi,

Sounds as though you might have some inadvertent short circuits somewhere on the Z motor wiring. That doesn't explain the magic touch you have on the X axis stepper though. Tilting the machine may be just enough to remove a short circuit if that is the cause of your problem.

If you have access to a testmeter, with everything unpowered check for continuity between Z motor wiring and the metal chassis - there should be none!!. There are some very sharp edges over which the wiring from the X - Z axes has to pass and these may have cut the insulation.

When I built mine I put insulation (Hellermann sleeves) over the wiring at possible "danger points". In particular look at the point where the wires exit the gantry and are turned at right angles before entering the corrugated black tubing - there are some sharp edges there.

Like you I had the annoyance of the limit switch terminals (I filed mine down to fit the connectors) and the short X-Z cable. I had a few mechanical issues as well that point to a lack of quality control - fortunately I was able to correct these using a mini lathe. I also added a ground connection between the power supply 0V and the chassis metalwork, bearing in mind the comments you had seen about grounding on the German forums

Hi, thanks for the help.

I searched the leads for a problem but they all looked pretty clean. Eventually I decided to switch the x (which is working properly) and z motors on the circuit board to see if the z motor would run off the x circuit. It worked perfectly but when I tried to jog the x motor now connected to the z circuit it tripped again.

This makes me think that the z leads are fine and it could be a problem with the circuit board?

I found a nick in the insulation of the xy end switch lead near the cable collector. I wrapped this in electrical tape, but this hasn't changed the problem. Also I don't think this could have been the problem in the first place because the x motor ran fine.

Anyway, still stumped. How would I check whether the circuit board is running correctly?

That's a tricky one!!

There is no published information that I can find on the control board other than the terminal connections. However if the Z motor and wiring is ok, and the board functions correctly if you jog X and Y but fails immediately you try to jog Z, then it seems probable that the stepper driver chip on the control board has had its day.

Guess the only sure fire way is to replace the board unfortunately, as everything is still under warranty this shouldn't be a problem.

One thing you might do first if you do have a testmeter is to check for a short circuit between each of the four motor drive terminals and both ground and the 30V supply rail - these should be effectively open circuit with power off and the motor disconnected. The motor drive chip is a fairly complex device and powers the stepper coils via a pair of H bridge drivers. Plenty of possible failure modes here and a fault output too, which probably triggers the red LED you see. The link above is probably the device used, though I can't be sure without actually checking on my machine.

It's also possible that there is a stray solder whisker between pins on the Z driver chip ( this is the large multi lead package adjacent to the Z terminals) or its surrounding circuitry. The lead and pcb track spacings are only a fraction of a millimeter so a strong magnifier and a bright light is need here to spot any problems. If you do see anything amiss, try to dislodge it with something non metallic - ie a sharpened cocktail stick, don't risk using a screwdriver as the tracks are fragile and easily damaged.

Hope this helps.

Peter

Swap the wiring of the motors.

Wire Z to X

and X to Z

See where the problem follows...

if it stays with Z motor - then finger points to motor or wiring.

If it follows to the X axis... as in jogging Z (moving x) causes same issue then you know its not the motor.

it could be a grounding issue?

Try grounding the machine to an earth pin and see what happens.

Thanks for the help everyone. I'm still stuck, but after emailing step craft it looks like it might be a unit control problem. The motor and wires are definitely ok.

Can anyone tell me specifically how to earth the machine? I would like to try this as a last option.

Hi,

The picture shows how I grounded to the chassis parts my 420. I had a couple of solder tags that fitted the thread on the pillars - one under each so as not to skew the cover. These link the power supply 0V to the metal chassis , but not necessarily to the rest of the machine because of the insulating powder coating on parts.

I didn't connect to the mains ground as I have no idea what provision might be made in the power unit or in the control computer - a ground loop could create more problems than it solves.

There is always the possibility of static build up during operation, particularoly if machining plastic parts. It's not difficult to build up enough voltage to spark across a gap of several mm - and the consequences could easily be terminal for some sensitive circuits in the control unit. Perhaps the ultimate solution would be earth straps between all the metal parts (might mean removing some powder coating) - best done during initial build, not easy in retrospect.

Hi.
I just got used 2-600.
First it ran fine until i aborted test-run and after that got the same problem as in this topic.
Did you figure out what was the problem?