Engrave/v-carve issue

My engravings have been terribly ugly recently. As you can seeing the pictures, the corners of the “D” went deeper as it went Z+. Also the right leg of the “A” and top, those are supposed to all me straight lines. The “Q” is messed up as well. These are just examples, the whole carve is like this.

I wondered it was flex because I was removing too much in one pass, but removing the last little bit with another pass doesn’t help. I’ve messed with everything and theres no noticeable flex anywhere. I had to tighten the set screws on the gears of the y-axis because I found there was play, so I checked the z-axis but its great. Unfortunately, there is absolutely no actual info on belt tightness, just discussion about some expensive belt tension meter. But I tightened the z belt, that didn’t help.

By my observations, I would say its a problem with Z-axis, like something is loose and when theres a direction change, there’s play, but all is tight with no play.
Any suggestions?
I’m using Fusion 360 CAM

Were the cuts around the outside also done with the same engrave? They’re not looking too straight. The vgroove cutters/engraving are much less tolerant of z backlash. - things to check: turn the machine on and try and move the carriage around - this looks like there’s a lot of backlash somewhere, that might point you in the right direction. After that, wheels - gunk in the groves, broken edges, gunk built up on the extrusions (top and bottom of the extrusion), loose eccentrics, flat spots.

For the mechanical aspects, we have articles on:

For the belts, I wrote up my notes on this at:

(linked from: Shapeoko CNC Router, Rigid, Accurate, Reliable, and Affordable )

w/ the carriage lowered all the way, I’m now getting D 4 (left) and B flat 3 (right) (using a guitar tuner app)

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My first guess would be that you’re V-bit has an unaccounted flat, so you’re carving a bit too deep. That is always more noticeable in the corners.

Is the collet tight? Bit slipping maybe? 1/4” shank bit in 1/4” collet? I know that sounds funny, but some have used metric 6mm shank bits in 1/4” collet, which is close, but can slip.


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I’ve checked all this, seems all good, just the z axis has some flex but as far as I can tell it’s just flex in the parts, I never have liked how far the point of the bit ends up being from the main carriage and point where the router is fixed to the carriage, just seems like it would be more forgiving of flex if it was closer to the fix point…if the makes sense.

I downloaded a tuner app, but I know absolutely nothing about music or reading it, can’t figure it out.

Just start the tuner app, pluck the belts and see what notes the tuner indicates the belts are at.

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