Enabling M852 (Marlin Bed Skew Compensation) in Buddy firmware
I would like to try enabling this in the buddy firmware. Before I go down this road, has anyone successfully done this for a Mk4 based printer?
Currently I've been adjusting skew by pulling the STL into FreeCAD and doing a matrix sheer operation which is a PITA.
I've mechanically been able to reduce skew to -0.15° but I'd like to compensate for the remainder. This equates to -0.5mm on a long diagonal print but it's enough to throw off slightly some screw holes.
Found an old thread on this: https://forum.prusa3d.com/forum/english-forum-original-prusa-i3-mk4-hardware-firmware-and-software-help/how-to-add-skew-correction-to-mk4-2/
Seems the OP wasn't successful...
RE: Enabling M852 (Marlin Bed Skew Compensation) in Buddy firmware
I looked into this a while back and, short answer, it’s not straightforward on the MK4 with Buddy firmware. M852 exists in Marlin, but Prusa’s Buddy firmware is heavily customized and a lot of standard Marlin features are either disabled or reworked. On the MK4, skew correction is expected to be handled mechanically and via input shaping and calibration, not software shear. Enabling M852 would likely mean rebuilding firmware and touching motion math, which is risky and not officially supported. Most people who tried ended up abandoning it. For small residual skew like yours, CAD compensation or slight mechanical tweaks are still the safest options for now.
RE: Enabling M852 (Marlin Bed Skew Compensation) in Buddy firmware
Yep, I dug around in the firmware and even though M852 can be enabled, it won't do anything so it's a NO OP. I'm sure this could be done by grafting on stock Marlin otherwise, just do the sheer operation on the g-code itself as a filter in OctoPrint. Regardless, I think for now I'll just stick with pre-sheering in FreeCAD.