I've spent the last few months putting a laser cnc together and have just got to the stage of testing the stepper motors.

The Y axis (Nema 17, 2 amp) one works perfectly – smooth, quiet and cool – so at least I know I can wire one up correctly.
The Z axis (Nema 23, 3 amp) one is smooth and quiet, but gets pretty hot – too hot to comfortably touch after about ten minutes. If I set the current lower then it doesn't rotate.
The X axis motor (Nema 23, 2.3 amp series, or 4.2 amp parallel) is very noisy, especially when starting and stopping, and it also seems to randomly make its own mind up on which direction it goes in. I have tried every current setting, and, since this one has 8 wires, I have also tried both series and parallel wiring configurations.

The motor drivers are DM542's and the controller is a Ruida 6445G. The testing so far has been with the arrow keys on the controller (not ready for g-code yet, and the laser tube isn't installed).

The Z axis motor is not going to be used much, unlike a cnc router or mill its only used to set the bed height at the start of a job, but it will be sitting there getting hot because of the holding torque, so I'd like to sort it out if possible.
The X axis motor is more of a problem as it will be constantly on the move, so it would be nice if it was reasonably quiet, and important that it moves in the direction its told to!
Any ideas?

Martin – I’m pretty sure that I have got sw4 set correctly but I will check to make sure.
Keith – Also worth me checking this again, but I hadn’t thought of just using one set of coils – I’ll try that tomorrow morning. Fortunately it’s connected up with Wago terminals, so very easy to change.

I’ve had another play about this afternoon. First I removed the Z stepper (the one that was overheating) – I’ll sort it out later.
next to the X axis, and I tried Keith’s suggestion of just wiring one coil from each pair, but it made no difference – still the same vibration on starting and stopping, and still the random choice of direction at each start. I then swopped to a 4 wire Nema17 motor, (same as on the working Y axis) and the vibration problem is still there. Then a swop of the X and Y motor leads, and the problem is transferred from the X to the Y motor, so it looks to me as though the problem lies with the motor driver.
I can’t see the reply now, but yesterday the first response suggested that the DM542 was not the best – maybe the next step is to buy a new driver for the problem axis.

Re the overheating Z motor, there is no provision for adjusting voltage. The dip switch settings adjust the current and the microstepping, except for sw4 as mentioned. Clearly it’s overheating because the holding current is too high, but changing the current setting either results in a motor that doesn’t spin, or doesn’t affect the overheating. Maybe two new drivers are needed.

John – thanks, I will have a look at the jumpers. I recall seeing a setting on the Ruida setup menu to change from Pul/dir to cw/ccw mode, and also to change from leading to trailing edge. I assume that these controller settings have to match the jumper settings?

I’m still a bit puzzled by the talk of changing the voltage – I can’t see how this is done without changing the power supply (mines a 24v Meanwell model).

A small bit of progress – in a fit of frustration at my own inability (!) I decided to remove the wiring to the steppers and drivers completely and start from scratch. The result is now three steppers that run smoothly and don’t seem to get hot. I have no idea what I rectified by rewiring which is slightly annoying, but I’m pretty sure it was a daft mistake on my part.

But I still have problems with the X axis motor not knowing which way to turn, and it hasn’t been solved by substituting a different stepper motor. I have checked the jumpers in the driver – actually no jumpers are fitted to the pins, so it is set to Pul/Dir and active on leading edge. I configured the Ruida controller with these same settings.

I did wonder if the datasheet for the motor has incorrect colours described for the 8 wires, although when I substituted a four wire stepper it exhibited the same behaviour. Another possibility might be some sort of electrical interference, although the cable to the this stepper is the only one that is shielded.

Two things that I find mildly annoying – posts that ask questions but the final solution is never posted, and idiots who can’t admit when they’ve been really stupid.
So in order not to be guilty of both at once, and very red-faced, I think it’s confession time. I have some 4 pin plugs and sockets connecting the steppers back to the control cabinet. I had made such a neat job of these connections – all with heat shrink and numbered labels etc – that I left these alone yesterday when I did the rewiring. It turns out that one of the conductors wasn’t actually soldered onto the terminal, instead the tinned end of the wire had stabbed itself into the plastic and missed the terminal by about half a millimetre. Having melted itself into the plastic it survived my normal tug test, and once covered with heat shrink was out of sight.

A quick test once it was soldered up correctly and it works perfectly.

So, my sincere apologies for wasting everyone’s time – the only silver lining is that it was actually everyone’s responses that forced my brain to eventually work out where the problem might lie – ie that one of the coils wasn’t getting a signal. Actually, another silver lining is that I have at last used the little oscilloscope that I bought as a bit of an impulse purchase a couple of months ago.

Many thanks for everyone’s help.