Backlash? What is causing this?


Today, while testing the x-carve after over a year of downtime, I saw this issue (it might’ve done that before and I just never noticed). The “left to right axis” in the picture is aligned with the X axis on the machine. This was a 1/2 bowlcut bit cutting an hexagon shape. You can see where the bit “dipped” a bit too far left.

Is this type of over travel cause by backlash? I only see it when the direction changes, only on the X axis for now. How can backlash be measured and calibrated for? I use UCCNC and have parameters for backlash correction.

Thank you

Well a xcarve uses belts which experience stretch, and backlash only applies to screw driven machines, that said both stretch and backlash would result in less of a cut, not extra cut… kinda semantics but I’m here to educate, so please don’t take that part personally.

I think what your seeing there is actually the correct cut location in the corners because it is changing directions it slows down and then cuts to where it should… the rest of the edge is cut less than it should and that is the actual area of fault. Most likely caused by belt stretch, a lose belt, or loose vwheels.
The vwheels use eccentric nuts on the bottom of x and y and may need to be adjusted… .and the belt after sitting probably needs retensioned and may be stretched over time, so I would buy a new one as yours might snap soon after retensioning it.

Hi Seth,

Thanks a lot for your answer. I am always up for learning, so not taking this personally at all.

This makes a lot of sense. I do have 9mm belts so I don’t think they will snap, but I will certainly adjust their tension and v wheel tightness as well.


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