Print Shifting on Y Axis

I fixed the 2 times scaling error I had as a result of using A49 drivers on my MPCNC but now I’m plagued by the prints shifting north on the Y axis after a fair amount of printing. All the axis’ have the same “feel” in terms of holding torque. The manual movement of the x and y feels nice and smooth , likewise the z axis has no stiff bits that I can determine. The belts feel like they are all around the same tension. I’ve read the other posts on the Forum about prints shifting , try maybe reducing the max speed , where on the firmware should this be done?

Almost sounds like you’re missing steps on the y. Try moving it with repetier in one direction then in the other at the same speeds and see if it starts missing steps. Not cutting, just moving.

g0 x500 f200
Then bring it back to the start position and
g0 y500 f200

If you don’t get missed steps, up the feed rate until you do, then back it back a bit. Both axes should be able to run at the same speed. I’m also assuming your router can travel 500mm, if it’s shorter, adjust accordingly.

What is your print settings? How fast are you moving? What is your usable z length? Did you adjust the current on your drivers to match your steppers?

As long as you didn’t mess with the speed or acceleration settings in the firmware it is probably something else.

I print at 30mm/s with a 5" zaxis.

Changed only the firmware from B16_32_fullG-112515 to latest RC7 MPCNC w/LCD and changed axis steps to match A49 stepper drivers only giving 16th steps. The MPCNC has now printed a number of Marvin keyfobs in various sizes perfectly. Printing a 40mm test cube at the moment and it looks good. So it must have been speed values in the old firmware? Anyway thanks all , one happy mpcncer here. Now to mount the spindle and do some test cutting.
Regards Jim

An update , I eventually changed from A4988 to DRV8825 Stepper Motor Drivers on my Ramps 1.4 board , immediately I noticed how strong the holding torque was on all axis’ compared to the A4988’s. After many test prints later no print shifts have occurred at all. I think the 2A steppers I had were not able to be driven fully by the A4988 for some reason , this even after many times of setting the vref pots according to the datasheet formulae. I also don’t get any problem with heating of the steppers so that’s also comforting. All in all I’m very happy with my setup and the novel design of the MPCNC. Already I’m looking forward to some wood carving and some Aluminium chips creation.
Regards Jim