step size, bed size for RAMPS + A4988

Hello,
I am trying to build a CNC machine with a small XYZ stage. The motors are 24V x 0.6A, 1.8 degree/step. The stage uses M6 leadscrew. The motor drivers are A4988. I am using all 3 jumpers for each driver, so I understand that in the case A4988 it is a 1/16 micro-stepping. I defined the bed size in Marlin as 100 X 100 mm. For the control, I am using a Pronterface software. The problem is that with the default 80 step size, the motor cannot reach the endstop switch and the error appears ("echo:Homing Failed Errorrinter halted. kill() called!"). It seems that the motor stops before reaching the endstop switch because the time defined for the homing procedure has ended. Also, I noticed that the travel distance depend on both the bed size and the step size parameters, since when I am increasing either one of the, the travel distance increased. However, I cannot get the correct settings. According to the calculator of the step size (https://blog.prusa3d.com/calculator_3416/), the correct step size should be 3200. However, with this step size, the motor does not move and only produces pitch sound, so I believe this step size is too high. It seems that I am missing something here. What would be optimal settings for my setup?
Thanks.

Edited 1 time(s). Last edit at 05/30/2023 10:06AM by anton74.

3200 should be correct but it is is a lot of steps / mm for a old 8 bit controller.

I would definitely change it to 1/8 micro stepping and set 1600 steps/mm

you will need to reduce the X and Y DEFAULT_MAX_FEEDRATE { 300, 300, 5, 25 } // X,Y,Z E


See how Z is way slower, because Z is a lead screw (or threaded rod)

Quote
Dust
3200 should be correct but it is is a lot of steps / mm for a old 8 bit controller.

I would definitely change it to 1/8 micro stepping and set 1600 steps/mm

you will need to reduce the X and Y DEFAULT_MAX_FEEDRATE { 300, 300, 5, 25 } // X,Y,Z E


See how Z is way slower, because Z is a lead screw (or threaded rod)

Thanks! A stupid question - what dimensions are the BED_SIZE parameter, millimeters or steps?

Another question - the endstop switch for the Z axis is at the top of the axis, near the motor. The home position should be at the lower end of the Z axis. How should I configure the endstop switch? I believe it should be configured as ZMAX switch, but for some reason the Arduino complains when I configure it as ZMAX - it seems that the homing procedure searches for the ZMIN switch. How can I change it?

Edited 1 time(s). Last edit at 05/31/2023 06:04AM by anton74.

... BED_SIZE ist mostly in milimeters, als steps are too "individually".

The searching direction ist too a parameter, which is set by 0/1 somewhere - check the section, where the axes are predefined (different depending on firmware and version/date) ...

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