Help diganosing fault with chinese Chinese CNC router

[Ats101]

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.

[JohnHaine]

Two possible causes occur to me. One is that there is an intermittent connection in the z direction wire, but you seem to have ruled that out. The other is that the setup of when the direction signal changes relative to the step pulse is wrong. If they are coincident then the driver can get confused over which way to move. Without detailed information on the controller I can't comment on whether there is a configuration option for this.

Edit: I found the manual in case you don't have a copy. On a quick read I can't find an obvious option to change this.

[Ats101]

Hi John,

Thank you for the reply - I have a copy of the A11 manual and have been through this multiple times.

I will triple check the direction wire connection again.

Can you elaborate on the potential issue with direction signal and step pulse - How exactly do the two relate?

The stepper motor is NEMA 34, and has 8 wires entering/exiting it if that helps with the diagnosis...

[Ats101]

Please see photos for driver, control board and stepper set up. I'm hoping the photos will prompt some more thoughts into the matter.

Many thanks.

[Ats101]

UPDATE:

I swapped X motor driver with the Z motor driver.

I have not yet been able to reproduce the homing the wrong way issue BUT I repeated the lettering V Carve and pocket files in this order:

30 Degree v-bit
1/16 end mill and 1/8 end mill for pocket.

30 degree and 1/16 end mill were flawless. Unfortunately 1/8 end mill toolpath did not go to plan. The lettering was destroyed with what looks like horizontal fluctuation/ abnormal movement likely caused by x axis issue.

Therefore this is likely to be a bad Leadshine DMA860H microstepper driver.

I am fully aware that any electronic product can develop faults but how likely is this?

Has anyone else had driver issues before?

[phill05]

Not had driver problems but quite a few years ago had DSP problems at the time I did away with dsp changed to Mac3 controller never had a problem since.

[Ats101]

Not had driver problems but quite a few years ago had DSP problems at the time I did away with dsp changed to Mac3 controller never had a problem since.

About 30 mins ago, turned on the machine, homed all axes and X moved in the positive direction rather than negative. Fault diagnosed as driver and I have a new one on its way.

What were the symptoms of your DSP problem so I know what to look out for?

Thanks.

[phill05]

Much like your problem we tried changing drivers round but still had the problems, we took out the dsp and replaced the card to try Mach 3 and it worked and never happened again so we left mach in control this was back in 2013.

[Ats101]

Thanks,

Yes I wouldn't be overly surprised if the issues persist after replacing the driver but I am confident it will sort out my problem.

If it doesn't - I will not hesitate a second and convert to Mach3.

Did you do this swap yourself?

[phill05]

Yes picked up a new card from cnc4you put a copy of mach on and away we went