I have at last got my CNC machine running. I spent hours setting the steps in motor tuning so the X and Y moved 50mm. But when I cut a pocket 40mm sq it measures only 37mm sq what have I done wrong or missed.
Mike
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I have at last got my CNC machine running. I spent hours setting the steps in motor tuning so the X and Y moved 50mm. But when I cut a pocket 40mm sq it measures only 37mm sq what have I done wrong or missed.
Mike
You may be missing steps. If you slow down the max feed rates in your CAM / g code, does the problem go away?
Also check that the maximum step rate from the controller to the stepper driver does not exceed what the stepper driver can handle. You may be able to reduce that somewhere in the settings - values such as 100kHz, 200kHz etc are common. You could try a reduced step rate if you are losing steps.
You should be able to calculate the number of pulses per mm rather than use trial and error. You know the ballscrew pitch and the pulley reduction ratio (if you have one), so the pulses per mm should be fairly simple to calculate directly.
How are you generating your gcode? Given that you have the same error in X and Y (although not sure how exact your measurements are!) it doesn't sound like a missing steps problem - although nothing can be ruled out at this point! But there can be issues with offsets and tool diameter settings in the CAM stage (gcode can be generated that allows for tool diameter at the gcode creation stage or makes no allowance which is done by the control software - Mach3 or whatever).
Can you post the gcode, assuming that it is something fairly short for just cutting a square?
I agree with Muzzer that you should be able to get very close to the correct "steps per" setting by calculation. On my own machine, this calculates as something like 400 steps per mm; accurate testing and measurement, at least as far as I could with my workshop facilities, meant changing this to something like 401 - presumably because of very slight errors in ballscrew pitch.
( Made using CamBam - http://www.cambam.co.uk )Quote:
Originally Posted by Neale
( Untitled 7/9/2023 1:46:45 PM )
( Post processor: Mach3 )
( T4 : 4.0 )
G21 G90 G64 G40
G91.1
G0 Z3.0
( T4 : 4.0 )
T4 M6
( Pocket1 )
G17
M3 S1000
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M5
M30
Here is my GCode.
Were do I fimd what Microsteps to use I am set at128?? Asl were do I find the formula for the setps. A friend sent me one but that came out at 5000 and the machine would not move. Thank you for your help Mike
Had a quick look through the code and it moves the cutter around a 36mm square, cleaning out the interior of the pocket. So the resulting pocket should measure 36+cutter dia. So it sounds like the steps/per is wrong, or it's missing steps. If the pocket is accurately square, it is unlikely to be missing exactly the same number of steps on each axis, and the pocket sides would be stepped as it loses more and more steps on each depth pass. So it's looking like steps/per is wrong...
My best guess, anyway - but this is all long-distance diagnosis so could have missed something!
- Brian