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]

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


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[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.

[JoeHarris]

So I tried the calibration tool in MACH3 this evening. Moved a centre finder 600mm up the x axis against a steel rule. To the eye it was bang on. Moved it 500mm on y axis and it was maybe out by 0.5mm over that distance. So why was it out over 50mm when cutting??


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[Clive S]

So I tried the calibration tool in MACH3 this evening. Moved a centre finder 600mm up the x axis against a steel rule. To the eye it was bang on. Moved it 500mm on y axis and it was maybe out by 0.5mm over that distance. So why was it out over 50mm when cutting??


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Is it missing steps? What are you setting for that axis?

[JAZZCNC]

Is it missing steps? What are you setting for that axis?

Clives right it's missing steps but not because of anything you have done or the machine.!!

It's most likely the Step pulse is on then wrong side of the slope. It happens often with IP-M and Leadshine drives or any drive that can select the leading edge.

Easy to see and easy to fix. The test is to knock up some G-code which moves say 500 times from point A to B doesn't matter how far.
So G0 x10 then back to X3 repeated 500 times will be plenty. Then last move back to X0.
What I do is setup dial gauge and zero out against the axis. Then run code, this why only move to X3 so not smacking gauge each move then last move back to it with X0.

If out it will soon become clear.

If doing this the fix is to go into MOTOR OUTPUTS and toggle the Step Lo box. This is the only box other than Enable that IP-M uses on that screen.

Hope this fixes you.

[JoeHarris]

Clive, Jazz, thanks that makes sense - I remember reading but not understanding this in the ipm manual! I’ll give it a go and see. Could not understand how it could be loosing steps on such a light cut.... cheers guys


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[JAZZCNC]

Clive, Jazz, thanks that makes sense - I remember reading but not understanding this in the ipm manual! I’ll give it a go and see. Could not understand how it could be loosing steps on such a light cut.... cheers guys


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99% sure it will be that Joe. (Provided nothings lose or falling off machine which knowng you sure it won't be..lol)
Happens 50% of the time with these controller/drive combo and it's something I check for has matter routine. Can happen on any controller really but with the IP-M or S happens randomly depending on how drives setup. Esp if not used tuning software to check Rising edge setting in drive.

Edit: For anyone else reading this that doesn't have Cslabs controller but as similair problem then the same can apply.
The test and fix is the same. Or if the the drives have option to change the leading edge setting use this. Both work same.