Hi!
This came up as a discussion in another thread today…
When my X (long axis) should move 200mm it actually moves around 199mm. I have bought hardware from Ryan and have Ramp 1.4 with reprap LCD.
Is this where I start to change the steps per mm in Marlin like this, or is something else wrong with my machine?
Current steps x (200 / measured distance traveled)
Usually the measured number is larger due to belt stretch. So you may want to look into why that is the case before adjusting steps per mm. Adjusting steps per mm is kind of a last thing you do on the tuning totem pole. The equation you wrote is correct otherwise.
200 mm is not so much. Try to measure the longest path you can of each axis. It will be also easier to calculate the right step per mm value (but as said you should not change it unless you use different pulley on the motors)
Check that nothing is loose, especially the grub screws on the pulleys. Check that it goes back to zero (if it is off by 1mm, then the error is backlash and not a scale).
Interesting, I will try this!
Is it the belt and other hardware that define steps per unit “100, 100, 400, 100”? But what if belt has been tighten differently and such?
The belt has fiber inside that is very hard to stretch. Once you reach a reasonable tight, it takes a lot of tension to stretch it.
The rest of it, there are exactly 200 whole steps per rotation on the motors. There are exactly 16T on the pulleys and the drivers step exactly 16 microsteps per step. So the rest i is literally exact.
The belt can be off though. I just try to avoid encouraging calibration until you’ve eliminated any other problems.