Calculating steps per mm

we are struggling to calculate steps per min on our z axis (with a lead screw with a pitch of 20mm)
The onboard driver is 16 microstep, but for the z axis we are using an external driver that has 10 microsteps which runs a nema 34 1.8 with a 50:1 worm gear
We have followed formulas, and also an online calculator, trying with 16 and a 10 microstep, and tried the values with no success

Are we missing something obvious here ?

does you lead screw have multiple starts? as that needs to be factored in

20mm seems to be a very large value for the screw pitch. Are you sure about that?

Working on 20mm pitch, one turn of the screw would result in 20mm movement.

At 1.8deg/step (200 steps/rev), one step would be 0.1mm. At 1/16 microsteps that would be 160 steps/mm.

At 1/10 microsteps and 50:1 reduction, that would be 10*50*200 = 10000 steps/turn = 10000/20 = 500 steps/mm.

Never heard of 1/10 microstepping?! Is it possible with external drivers?

Quote
frankvdh
20mm seems to be a very large value for the screw pitch. Are you sure about that?

100% sure. This is not a small printer. The print volume is over 4m³
We are using a geckodrive as an external.
Will the microsteps come from the external, or the onboard?

Edited 2 time(s). Last edit at 05/18/2017 05:36AM by Vital1.