Need some help with steps/mm

I'm running Marlin 1.1.0 RC7 on my newly minted D-Bot Core XY and I have some issues with the steps/mm settings. I'm using the DRV8825 drivers with the MS3 jumper set which essentially means they are configured for 1/16 micro step. Also I'm using the standard GT2 belts for the X and Y axis and a 20-tooth pulley on the motors. The Z-axis uses a 2mm pitch acme leadscrew. With these settings I get the X and Y steps/mm as 80 and the Z steps/mm as 1600. However, if I move the axes by 4mm, I get 16mm of travel. What am I missing?

Your math looks right

I would guess you have and eeprom enabled and you updated your configuration.h with the new steps/mm values

The eeprom takes precedence over the configuration.h Send a M503 and check your steps/mm are what you expected.

To reset eeprom to values in configuration.h do a M502 then a M500

Right! M503 shows the same values as configration.h. Though this is still a mystery, I changed the value to 400 from 1600 and now the travel is correct. I can't figure out the math though!

Are you sure that your microstepping jumpers are set correctly?

Are you sure of these are 2mm pitch acme leadscrew, url to source?

If they are multi start vs single start then that changes things, take a look at them end on.. single start you can only see one start and 4 start for eg you see 4...

4 start would explain what you seeing perfectly

Edited 1 time(s). Last edit at 12/17/2016 03:27AM by Dust.