I have built my MPCNC, great project and learning a lot. I have drawn the crown and it looks great but I have an issue with Z axis movement. A 10mm movement is 2.5 mm. The stepper is turning the lead screw about 1.25 revolutions.
I have an 8mm lead-screw with 2mm pitch. Control board is BTT SKR1.4 Turbo with TMC2209 drivers.
Marlin code is: V1CNC_SkrTurbo_Dual_8825-2.0.7.2-src
I have editted it for TMC2209 drivers
This is the relevant setting: #define DEFAULT_AXIS_STEPS_PER_UNIT { 200, 200, 800, 200 }
I have modified this using values from the Prusa calculator and manually entered: M92 Z3200.00
This make a worrying noise, M92 Z1600.00 moves it but not enough.
Anything I have missed? X& Y are fine. Using endstops if that matters.
The standard hardware is 8mm with 2mm pitch and 4 starts. So one rotation is actually 8mm. 1.25 revs is 10mm.
It sounds like you have a 1 start. You can replace them, or change the steps/mm to be 4x and reduce the max speed to 3-4mm/s. If you leave the top speed, you will probably lose steps because steppers lose torque at high rpms.
With configuring Z movement on new machines I have found it to be VERY wise to set the acceleration to something really low like 1. Then use the GCode M commands to set steps per mm max feedrates. Set it low and test then change it up and test and test test. Until I find a speed that sounds good and moves well. Then I try testing the acceloration setting until I am happy. Usually end up at 4 on old marlin firmware and 8 on new I think.
Thank you Jeffeb3 and Aaryn. I am testing like mad and I have ordered a 4 start screw so hopefully that will solve it.
I am still going to fiddle. I cannot find a specific mm/rev setting so I am assuming it is tied in with the STEPS_PER_UNIT value. I will drop the feed, which would be M203 Z2.0
I’ll update as appropriate in case it help some else in time…
UPDATE: Changed steps to 3200 and dropped feedrate to 2mm/s and looking good.
/me needs to find a router