3 Axis CNC router

[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]

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.

[Neale]

I saw exactly the same problem on my machine. X and Y were fine, but Z looked as if it were losing steps on complex 3D work. In my case, it didn't show up on single test runs; what seemed to happen was that you lost one step every time you changed direction. Fix was simple - as Jazz said, just change step polarity. I think this is more likely to happen with the CSMIO controllers as they have differential outputs - brilliant for noise rejection, but too easy to get the two wires swapped!

My only reservation about this diagnosis is that I wouldn't expect to see any significant error on a single movement, as the effect is cumulative with movement direction changes. But Jazz's test (I did exactly the same thing when I was chasing the error) will soon show the truth!

[JAZZCNC]

what seemed to happen was that you lost one step every time you changed direction.

That's exactly what happens because the last pulse gets sent after the next direction change happens so it gets dropped.

To be honest, can happen on any system. The reason it tends to happen on these is that of the flexibility both drives and controller give. Meaning it's easy for one or other to be set wrong. Majority of older or lesser drives only allow rising edge which is ok for most sytems until you get controller that use's the falling edge.!!

[JoeHarris]

Thanks Neale, on a single movement there is very little error, only when cutting a test pocket with changes in direction did i see the error so I'm hoping this is the explanation. Whilst I've taken care throughout the build and asked a lot of questions, I have made this machine with basic tools and basic skills, so I'm sure it's not just down to calibration!

[Desertboy]

I read sometimes the seals on the ballscrew can be tight when new so when you first run the machines they can stick a little, the solution run it up and down the full length of the travel a few times. Greasing can help to.

I had a sticky bit right at the end of my travel on one of my Y ballscrews kept firing a stall detect at me, after 10 to 15 running up and down the lengths occasionally stalling the problem disapeared. The area where it stalled is now part of my homing sequence so it gets travelled over regulary never stalled again.