Hi I'm a furniture maker from Norfolk and long time lurker. I've been using CNC routers for about two years now.

I've got a problem with my x axis losing position or possibly binding I've had trouble actually pinning down what's causing the issue. It can happen after 10 minutes or 8 hours which has made troubleshooting difficult.

The x axis randomly loses position in both the positive or negative direction, usually by less than the distance it was suppose to move during that piece of g code. I've had no issue with the Y or Z axis and it can happen when moving just on the x axis or when multiple axis's are moving at the same time

It hasn't happened during jogging. How often it happens and by how much it loses position seems to be independent of feed rate, acceleration or step and direction pulse length settings in mach3(which is a genuine license). I've tried running it with the spindle, extraction, water pump and everything else in the workshop off and it still happens. The frame is grounded on each axis and and the spindle cable is grounded at both ends. The few times I've been there to actually see it happen, the motor makes a high pitch noise then carries on.

I've tried swapping over the stepper motor, driver and all the wiring between the stepper motor, driver and BOB. As well as using different pins on the breakout board. After swapping over the wiring the issue seems to happen a lot less often for a time then goes back to being random. I've marked the coupling where it attaches to the ball screw and motor to check for slipping and checked the balscrew for any damage.. A fresh install of mach3 and changing the kernel speed also didn't help. I've tried turning off micro stepping which is set at 10 for the other axises.

I set up a bit of test gcode that move it 120mm left to right for an hour. I tried this with different direction pulse lengths which caused the x position loss being 120mm repeatably in either direction but after restarting the system it seems to go back to being random.

The machine is one I picked up off eBay, I was planning on building one myself but this was pretty similar to what I had planned and cheaper than I could buy the components. The bed is about 700mm x 800mm. Uses uc400eth CP0-10v BOB, 4.5Nm steppers and CWD556 drivers from CNC4You and Hiwin HGR25 rails and 5mm pitch ball screws. it worked perfectly for the first few months, cuts within the 0.02mm accuracy of my veniers on aluminium although it's mainly used for wood. The seller has been very helpful. He was only selling because his shed was built on a slope that its slowly falling down.

I'd like to swap to axbbe and UCCNC but I don't want to spend any more money until I've identified the problem. My next step was going to be shielding the stepper motor wire but I seem to be running out of things to try so I would love some advice on what I can try next.

Thanks

Sam