Stepps per mm wrong?

LowRider CNC Troubleshooting
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Lowrider3 dual endstops
Board is a ramps 1.4 no lcd

I have different pulleys than the original, mine has 20 teeth. I used the Prusa calculator and got the correct steps per mm for my pulleys, which is 80. I changed it using the M92 G-code to set the steps per mm in real time. Here is an example with your result for the X axis:

M92 X200.00.

I ran some square print tests, and the results were off. It was supposed to print a 50 mm square, but it did a 38 mm one. When I hit play again, the second time it made a 73 mm square.

So, I’m really lost and don’t know what to do.

Can anyone shine a direction for me

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Getting different results run-to-run means something is mechanically wrong with your build. You need to fix this first. Check grub screws in particular.

For the step calculation RAMPS is usually configured for 32 microsteps by default.

So, I think you need 200 steps/mm, but we can double check this after you solve whatever is mechanically wrong that is giving you inconsistent runs job to job.

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Yep, that’s a hell of a swing for anything besides something slipping.

Going from memory (and it’s an old one so verify) steps x input distance / measured distance give you the steps you want.

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The Ramps firmware is expecting DRV8825 drivers set at 1/32 microstepping (all jumpers in). With the stock 16T pulley, there are 200 steps per mm. If you change to a 20T pulley, you should have 160 steps per mm. If you used a different driver, or if you set up your microstepping differently, you will need to adjust.

I second Jim’s suggestion that getting different movement run to run suggests a mechanical issue causing lost steps. Or is it possible you have not zero the origin of the job?

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this!

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Yeah the grub screws was loose my bad.
Thank you all for this

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It is a great find when it is the grub screws. I hope you sleep well tonight.

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