When my CNC cuts tabs, it is leaving divots

My CNC has recently started to leave divots along the edge of the cut where the tabs are placed.
Does anyone have any suggestions of where to look first.


Last time that happened to me, one of my 3D-printed gears had broken and the Y axis had a LOT of wobble in it.

My usual advice here - grab the spindle and try to move it. Does it move? If so, find out why and fix it. Could be something as simple as a loose belt allowing more “give” on that axis than it should, or loose bolts, etc.

Thanks, I’ll give that a try.

You can also check tram. If the z axis is not trammed right then the vertical path it traces will have an angular component and the bit will cut a bigger diameter hole than anticipated.

Are you using 3D tabs? If not - do so.
What happens with regular tabs is the X/Y motion stops and the Z raises/lowers. This allows any deflection in the Z to ‘undeflect’ (hehe) and causes these grooves. Using 3D tabs the spindle does not stop moving. You may still get marks like these but they will be much smaller.
You will see similar results if you do not ramp in to a profile cut. For the same reasons.

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