Dear all,

I am new to this forum and looking for some advice about a current issue with my 8x4 CNC router.

The machine is branded under the UK company 'Laserscript' but it is effectively the same/similar to Chinese machines like Blue elephant etc. I acquired the machine a month ago second hand. The machine is from 2022. It does not have ATC and has stepper motors rather than servo motors.

It has the Rich Auto A11 controller.

There is an issue with the Z axis and it may be separate issues rather than the same.

1) On turning the machine on, approx 1 in 6 times when selecting 'home all axis', Z moves down towards the machine bed rather than up towards the limit switch. I would have to hit the emergency stop button, turn the machine on again and hope this time, the Z axis moves up on homing. On the occasions the Z axis is playing up, I have also found that hitting Z+ and Z- causes the Z axis to move the opposite way than expected. Sometimes without warning it corrects itself in which case I can home ok and get on with my work.

2) I have found that the Z axis on occasions is losing steps - I would see it processing the toolpath in mid air rather than in the work piece. This happened yesterday. I cancelled the file and selected Z home. For some reason, Z moved passed the limit switch rather than it stopping- the machine effectively crashed.

3) Also yesterday, I was doing a simple enough V carve and on two occasions Z plunged straight down, through the work piece and into the spoil board. After it did this the file continues to process correctly. The piece turned out ok but with 2 holes.

What I have done so far:

1) checked for loose wires in the control unit. There are no loose wires on the Z axis driver. On the Rich Auto control board, there are no loose wires associated with Z axis either. On the stepper motor end is hard wired i.e there are no clips.

2) The Z axis drivetrain has no play. The grub screws are tight, the belt is tight and the ball screw turns ok.

3) and NO! - its definitely not caused by a loose tool in the collet.

I am stressing over this as this is my livelihood. I think it is an issue with the driver or stepper motor although I have read stepper motors are very robust.

What do you guys think?

Many thanks.