Apparent Step Errors

Hi All;

I am a newbie and have built my first CNC table for use with a plasma cutter.

The table is working and the plasma fires and cuts OK, I am using SheetCAM for the CAM software and FreeCAD for the drawings.

I am experiencing some issues and I hope the forum can give me some guidance on how I might fix the issues, in particular the inability to correctly render circles and measurements out on linear direction. I tested using stepconf and the initial tests seemed fine.(Please see attached image)

I believe I am experiencing step issues, but have checked the mechanical side and there are no loose components, so am wondering if it may be due to the micro stepping, have I misconfigured something?

I am running LinuxCNC 2.7.0 and have included the .HAL and .INI files

The table consists of timing belts (15mm wide 5M pitch) and 20 tooth 5M synchronous timing pulleys.

Motors:
2 NEMA23 3A 312 oz/in for the X and Y Axis
1 NEMA23 2.8A 175 oz/in for the Z

For the electronics I am using
A Savebase BoB LPT1
3 DM542 Microstep drivers set for 2.84A and a micro-step of 800 Pulse/Rev
36V Power Supply
5V Power supply for the BoB

Please let me know if I need to provide any more information.
Many thanks in advance for any suggestions or guidance.

You need to calibrate the motors,

So 50/52 * current steps per unit = new steps per unit.

Thanks Fabricator.
I will test this out today.
Cheers John

Thank you Tommy;
I note you have a lot of experience in this space and I appreciate your feedback. Are there any links etc re design that I should read and evaluate?
Cheers John

And sorry, yes it is a direct drive at this stage, based on the unit we had at work using rack and pinion drives.
Cheers John.

Thanks Fabricator, you were spot on for the solution to the linear error, changed in stepconf and it is spot on. The circle resolution still remains an issue.
Cheers John

Can you post a picture of the circles? Are they not round? Or is the diameter incorrect.

If the latter, are you setting the correct kerf offset in SheetCAM?

Hi; The circles are still out as per the original image posted. They seem to be two elipes rather than a smooth circle.
Thanks
John