Z Axis getting deeper when carving

[GRS]

Hi All,

Its been quite a while since I've posted on here so glad I'm still a member . I have an unusual problem though on my home built cnc router.

It worked fine for around 4 years then all of a sudden the Z axis started going deeper and deeper as carving jobs were being run, very noticeable in the work.

I had done some testing with air cuts and still the zero was out , lower by a few mm .
Anyhow I also changed stepper motors over from Y to Z and still the same issue , so onto ebay and got a new z axis installed this , still the same issue. Spoke to a friend who helped me with my build , especially all the electronic as that's not my strong point !!
He suggested it may be the driver board so off to ebay again and secured all the parts and got a new driver board built and installed , moment of truth with much excitement .... still the same , even bought a brand new stepper motor in frustration to see if that was it , no still the same issue.

I am at an absolute loss ,I have almost re built this machine with no luck.

Also need to tell you that I run Mach 3 on my machine and share this with a cnc X2 mill which works perfectly so I know it's not the Mach 3 programme or my PC
I am using a Die Grinder as my spindle ( always have )

I did some research on here and came across some discussion on resonance ? Also some talk of problems when the wiring for the motors and the spindle are running together , leaky feed or something ? Like I say electronics is not my lot.

I will be forever grateful if someone could pin point my problem and have a solution that works.

Thanks for reading

Cheers Gary

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[awerby]

It sounds like a mechanical problem. Something in the Z axis assembly is impeding the motion upwards that used to be smooth, so you're losing steps going up. This results in the DRO reporting a higher position than is actually achieved, since there's no feedback mechanism to tell it that it never got where it was supposed to. So then, when it goes down to the cutting height, the tool is lower than it's supposed to be.

To confirm (or disprove) this theory, run your Z axis up and down a few times, and measure the position of the tool at the top and bottom of the stroke. If I'm right, you'll notice that the measurements and the DROs disagree.

[racerxman1200]

Check your G-code program for any sub-programs that might add an incremental distance amount to the Z-axis. Always check and recheck the program!

www.hydraulicandpneumatics.con

[GRS]

Hi guys'

Thanks for the input there , Andrew my Z axis is a THK LM Guide Actuator ,not a home made one and it does not loose steps as I have tested this also and even bought another one and replaced just in case this was the problem and have also tested the new one.
Racerx , I am not sure how to check your suggestion ?
Thanks anyhow , I'll push on in my quest

Cheers Gary