Squaring using computer vision

Hello! First post on inventables forum.

I thought I’d share my recent experience with the XCarve. I have an XCarve 750mm and recently discovered that the cuts weren’t very square but rather parallelogram like. I took it all apart and re did the assembly to minimize the skewness. I was able to reduce it, but not eliminate it.

So I instead decided to create a transform from expected gcode space to a transformed space that is square. I did this by using the thinnest bit. Line it up to one of the corners of the grid. Keep track of actual mm coordinate and gcode coordinate. Then compute the Homography transform. I then used this transform to remap the gcode to this new space. Square is more square!

Next step is to mount a camera to the x carve and place down fiduciary markers to do this automatically. Has anyone tried calibrating their XCarve this way or in other ways?

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