Z axis problems on MPCNC 25mm od

Hello everyone, i made a MPCNC with working dimensions of 600x1200x50mm with mid-span supports on y axis. I have a makita 3710 wich has 30000 rpm and i use single flute bit to cut laminated wood. I have 4mm depth per pass at a feedrate of 2100mm per minute.

The problem that i encountered is when i cut curved lines the bit moves while cutting left and right about 1-2 mm and i get some waves on the part. I didn’t attach anything on the z axis like cables, i attached everything on the xyz parts. I have a slight backlash on z axis but is up and down, not sideways to generate the waves on the finished part. i will post some more pictures tonight.

Offhand 4mm deep at 2100mm/min seems a little fast to me. Have you tried slower to see if it makes any difference? Maybe 700mm/min or so…

I agree, that is fast. What diameter is the bit? For an 1/8" I would start at 8mm/s, and keep moving up until you encounter problems. If you are using a 1/4" (~twice the load) bit you might want to start even slower.

Sorry, i forgot to mention that i use 6mm single flute bit. i will try to slow down or cut at 2mm per pass when i have the time. I attached some pictures of the ‘‘waves’’. Maybe i push it too hard… i will try your sugestions tomorrow. I attached the gcode.



z3.gcode (21 KB)

Other than that , I would suggest trying to put the laminated part of the wood down and not up. My reasoning, besides a probably nicer surface finish, is that almost all glue that is used to laminate the wood is really nasty and can be quite hard. So you might have better luck, if your bit has a “path” it can hold onto, even if it is a soft wood path.


Edit: Realised it too late, but that is of course only applicable if you want to actually cut through and are not planning on only cutting partly through.

unfortunately the laminated wood that i’m cutting has melamine on both sides and the problem appears on top side too and only on curved lines.