Why is my bit cutting air above the board - or plunging through into the spoilboard? (Z-zero mismatch)

Why this happens

When the error is exactly your material thickness, the diagnosis is nearly certain: the Z-Zero setting in Job Setup does not match how you physically zeroed the machine.

Job Setup has two Z-zero options:

• Material Surface: the file assumes Z0 is the TOP of the workpiece
• Machine Bed: the file assumes Z0 is the top of the spoilboard

If the file says Material Surface but you zeroed on the spoilboard, everything cuts one material thickness too deep. If you zeroed on top but the file says Machine Bed, it cuts air.

A secondary cause: a touch plate whose thickness is not configured (or is configured wrong) in the control software offsets every cut by the plate thickness.

The fix

1. Open Job Setup and check which Z-Zero option is selected.
2. Make your physical zeroing routine match it exactly, every job, every time.
3. If using a touch plate, verify the plate-thickness offset in your controller (not in the software).

Pro tips

• Zeroing to the spoilboard + the "Machine Bed" setting guarantees perfect through-cuts regardless of material thickness variation. Many production users prefer it for cut-out parts.
• Top-of-material zeroing is better when surface-referenced depth matters most (V-carving, shallow engraving on planed stock).
• Write your zeroing convention on the machine. Mixed conventions between saved files is the classic way this bites again months later.