CNC calibration

Cut a 100 mm test square, measure the real size with calipers: new steps/mm = old × (100/actual). ±0.1 mm per 100 mm is normal for plywood.

The bed must be parallel to the spindle: surface a test area with a large bit or check with a dial indicator. An unlevel bed = uneven cut depth.

Missed steps at high accelerations — step down 20% from where steps are stable. Feed rate depends on material and bit — feeds/speeds tables + a test cut.

Screw dead travel: the axis 'undershoots' on direction change. Measured with an indicator, compensated in grblHAL/LinuxCNC. Cause — worn nuts or loose couplers.

A Z-probe (plate/block) — automatic height zero. XY-probing on a corner — workpiece zero. Zero-setup accuracy is half of part quality.