Rotary 4th Axis CNC "duh" moment

Snapmaker 2.0
1

I’m an idiot. Sharing in case someone else has the same brain fart.
This is not my first CNC, but it is my first 4-axis CNC, so forgive me if this is obvious.

I was encountering an issue where, after setting the xyz origin and starting the toolpath, the bit would just hover above the workpiece and never actually start the cut. I left it running and it sat there for hours, with the piece just spinning and the toolhead hovering in place.
After about 12 hours (I forgot I left it going - oops) I heard it starting to cut. What the heck?

The reason? The B-axis does not roll over at 360 degrees like my dumb brain assumed. It keeps counting up for the whole cut.
My B-axis was in the 100,000’s and the Snapmaker believed it had to jog all the way back to 0 to cut.

TLDR: Don’t neglect to reset your B-axis origin, folks. Save yourself the headaches. Don’t be dumb like me.

Hope this helps some other poor, unfortunate 4-axis noob.

1 Like
2

Also keep in mind if you use the bit assistant to change bits between a roughing and finishing pass. Even if you reset your B (Luban actually does this at the end of a program), after the bit assist the snapmaker adds an arbitrary amount of thousands of degrees to B for no apparently reason. :smiley:

After doing bit assist, go back into the control screen, whatever the B is now at, divide by 360, drop the decimals, multiply by 360, spin B to that number, set B origin again. (i.e. B170,000/360=472.2222~, 472*360=169,920) So B169,920 == 0 .