3 Axis CNC router

[Neale]

I shudder every time I see someone suggesting using the calibration routine in Mach3! If the machine is giving errors this big, then you need to find out why, rather than hide it under the carpet. You are using ballscrews which are almost as accurate as your digital caliper. You know how you have geared (if not 1-1) your motor to the ballscrew. You know what microstep setting you have used. This gives an exact "steps per" value, and if the machine isn't achieving this, you really need to find out why. For example, it might be as simple as needing to check the adjustment of the ballscrew support bearings - and whether they were assembled correctly in the first place (don't trust the Chinese to get this right!).

Double-check everything first, including actual cutter diameter (I spent ages chasing machine errors that were down to cutter diameter errors, although that's not the case with differing errors in X and Y), and don't panic. You'll get to the bottom of it with a bit of systematic testing!

Good luck - we've all been there.

[JoeHarris]

I shudder every time I see someone suggesting using the calibration routine in Mach3! If the machine is giving errors this big, then you need to find out why, rather than hide it under the carpet. You are using ballscrews which are almost as accurate as your digital caliper. You know how you have geared (if not 1-1) your motor to the ballscrew. You know what microstep setting you have used. This gives an exact "steps per" value, and if the machine isn't achieving this, you really need to find out why. For example, it might be as simple as needing to check the adjustment of the ballscrew support bearings - and whether they were assembled correctly in the first place (don't trust the Chinese to get this right!).

Double-check everything first, including actual cutter diameter (I spent ages chasing machine errors that were down to cutter diameter errors, although that's not the case with differing errors in X and Y), and don't panic. You'll get to the bottom of it with a bit of systematic testing!

Good luck - we've all been there.

Thanks everyone! Neale, how tight should the ballscrew tensioning nuts be tightened? I’ve seen that people shim these but not sure how it is done tbh

[JoeHarris]

I shudder every time I see someone suggesting using the calibration routine in Mach3! If the machine is giving errors this big, then you need to find out why, rather than hide it under the carpet. You are using ballscrews which are almost as accurate as your digital caliper. You know how you have geared (if not 1-1) your motor to the ballscrew. You know what microstep setting you have used. This gives an exact "steps per" value, and if the machine isn't achieving this, you really need to find out why. For example, it might be as simple as needing to check the adjustment of the ballscrew support bearings - and whether they were assembled correctly in the first place (don't trust the Chinese to get this right!).

Double-check everything first, including actual cutter diameter (I spent ages chasing machine errors that were down to cutter diameter errors, although that's not the case with differing errors in X and Y), and don't panic. You'll get to the bottom of it with a bit of systematic testing!

Good luck - we've all been there.

Thanks everyone! Neale, how tight should the ballscrew tensioning nuts be tightened? I’ve seen that people shim these but not sure how it is done tbh

[JAZZCNC]

You know how you have geared (if not 1-1) your motor to the ballscrew. You know what microstep setting you have used. This gives an exact "steps per" value, and if the machine isn't achieving this, you really need to find out why.

Actually neal it's not that simple and I pretty much guarantee you that if your using timing belts then the steps per won't work out per the calcs.
This is one reason why mach's calibration is best used for most people who are using belts and only have basic measuring tools.
Even then it still won't be spot on and can be improved upon. But to do this you need Linear scales and to measure over large distance.

When I build a machine I initially set it up using the calcs then I fine tune using linear scales and EVERY TIME the steps per is different to the calcs. Close but it's always bit lower or bit higher.