X Axis is drifting and wondered if my settings are to blame?

Hi all,

I've been building a CNC machine as a hobby and learning as I go.

I've got to the stage of actually cutting something and it all seems to work fine (ish) apart from my X axis seems to be drifting out of position.

I tried to carve out some lettering and it seemed to start fine but then, as the cut went on, it was returning to the first letters and chopping through them so obviously wasn't returning to the correct place. It was also drifting off the end of the wooden "blank" that I was cutting on.

I tried reducing my Maximum Velocity and Maximum Acceleration down to 20.0 but I'm not sure if that's still too fast or normal??

I'm also not sure if Step Time / Step Space need adjusting?

The drivers I'm using are DQ860MA
www.wantmotor.com/product/dq860ma.html

The motors are Stepper Motor 8.7Nm Nema34
www.cnc4you.co.uk/Stepper-Motor-8.7Nm-86HS115-4208-Nema34



If someone has a similar setup and could let me know their settings it would be appreciated?

Or if you have an idea on what sort of values should be going into Max Velocity and Acceleration and also Step Time etc it would be great. Or even info on how you work out these settings?

Thanks for any help you can give me.

John

Thanks for the great advice Andy.

I ran another test just now and it's worked fine.

I think I *may* have got to the bottom of it. I put the Step Time / Direction Hold et al to 5,000.

I then ran the machine without switching on my vacuum cleaner.

Eventually I'm fitting a dust shoe and a dust extractor but, for now, I've just been periodically turning on the vacuum and hoovering the dust away. What I noticed was that the light above the table would briefly flicker occasionally when I turned the vacuum on.

I'm now operating on the assumption that my switching the vacuum on is causing noise and maybe making the system lose a few steps here and there? These are accumulating into a large error.

I need to do more testing to be sure but I'm hoping that's all it is. I carved something tonight (just some letters) but the dimensions of them and the sharpness of them looks really good I think.

Keeping my fingers firmly crossed!!

Cheers

John