# Marlin 1.0 works: Marlin 2.0 destroys Z-axis motion

I have an FLSun 3D Cube, running off an MKS GEN V.1.4 main board. With Marlin 1.0, the Z-axis works great (and has been for three years). When I try to upgrade to Marlin 2.0, moving the Z-axis 10 mm results in extreme motion -50 mm at least, left motor then the right motor, three or four times, very fast. It's loud, it's jarring, and it's at the very least incorrect.

What setting am I missing?

• Are you sure the steps/mm are indentical between your configurations? Too high values for Z max speed or Z acceleration might also cause odd behaviour. – towe Sep 28 '20 at 5:39
• Are you using Marlin 2.0 correctly configured for your printer? If it's configured for a different printer, anything can happen. Where did you get the Marlin 2.0 image? – DoxyLover Sep 28 '20 at 6:52

I believe (from reference) the default steps per mm for the FLSUN 3D Cube are:

                                          X,   Y,    Z, E0
#define DEFAULT_AXIS_STEPS_PER_UNIT   { 100, 100,  400, 150 }


Default marlin 2.0.x are:

                                          X,   Y,    Z, E0
#define DEFAULT_AXIS_STEPS_PER_UNIT   {  80,  80, 4000, 500 }


Such a setting would explain the excessive speeds; while the printer only needs 400 steps for advancing a single millimeter, the stepper receives 4000, this implies a tenfold, hence larger displacement and higher speeds.

• That's what I was missing. Thank you very much. – Bill in Kansas City Sep 29 '20 at 15:38