CNC router Drifting between depth passes Please Help

[nikohaller2002]

I recently built a custom CNC router using open loop steppers, GRBL, an Arduino and Universal G Code Sender. I am attempting to use Fusion 360 to generate tool paths which i then input into UGS. Whenever I use G code generated by F360 CAM my pockets will have a stair step look to them (on two sides of this hexagon pocket) but when I use the built in tool path generator in UGS I get perfect pockets with perpendicular walls. This makes me think it's a software problem rather than mechanical or electrical as when I switch software the problem pops up. It loos like the machine shifts over about 0.3mm between each depth pass. Has anyone had any similar problems?

[serge.quiblier]

Hello @nikohaller2002 

I don't think the toolpath generated wrongly.

But are you using the same technological parameters in both programs?

i.e. are you using the same stepover, stepdown, and cutting conditions.

If spindle speed or feed rate are different, it may explain some tool deflection or other similar problems.

Regards.

[nikohaller2002]

Thanks for the reply @serge.quiblier,

The cut parameters are very similar (feed rate, RPM and depth between cut). I've been noticing this problem only exists when performing multiple depth pockets on F360 CAM. Performing profile cuts at multiple depths using F360 is completely fine and has zero signs of shifting so I dont know if it's a particular setting I have for pockets that is messing up the cut.

[serge.quiblier]

What about plunging into the material for each passes.

Do you have the same behavior, i.e plunge vs zigzag ramp vs helical plunge?

What is the part fixturing?

Because, it's either the part moving, or the tool unable to cut correctly.