Stepper skiping steps

Hi there. I have a hobby cnc router with nema23 425oz steppers and DM542A drivers from some chinese manufacturer "Longs" i've been learning and making my machine in the past 2 years and i have done quite a lot of cutting with my machine and some crashing ???? and im very happy with everything, but a week ago i started hearing strage sounds from my Z axis, at first i thought it was a bearig but then i saw my Z axis is not constant in hight. Then i realized that i might be losing steps after some observation i find out that the sound im hearing is losing steps. I have tryed every combination for microstepping and i tweek some settings in mach3 (those who are for pulse and revolution 5/5 ) i try to change the wiers that go from my breakout board to the driver to use them from my X axis, same result. When i connect the cables from my X axis driver to the Z axis motor, the axis is moving perectly. Z axis motor was moving but randomly is skipping steps in eather direction with the faulty driver and is skipping a lot of steps! I try to connect the faulty driver on other motors and the resoult is the same motors are skiping steps. Now, while im waiting for the new to come frome China is there anyone who fixed stepper driver or who knows or guide me where can this fault acure in the driver so it behave like this. I did an eye observation all the soldering is fine, i test all the capacitors and they are good. What other component can be faulty for the driver to behaive like this. Randomly missing steps, few per turn, none for few rotations then again missing one per turn, few in a row. Any ideas?

I would check and tighten all wire harnesses and connections first.


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As i sayed, on the same cables that go to the Z axis motor, with the same connector i just plug a "healthy" driver and it works fine. So, the line is ok and the motor is ok

Ok. You could prove it’s the driver by swapping it from some working axis. Or just replace it as they are inexpensive.


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Also check the mechanical setup of the Z axis to ensure it is not binding and causing the axis to stall. Disconnect it from the motor and see that it moves freely.
Sometimes if the axis is too loose such as a loose gib in a dovetail, the slide will “rack” and bind up.
Cheers

Peter.


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If changing driver then make the most of it. Ditch 542 driver and get a 860 instead, run it on 60v and you'll see a massive performance improvement.
Are those Longs steppers the 6.8mh inductance ones or the 3.5mh ones?.

Yeah it is 6.8mh inductance motor but i would rather not change it to 60v that way i would have to make changes to my electrical cabinet, to change power supply and so on,,,i have changed the driver and it is all good now. Thanks for the replays guys.