How does Z-zero setup work in VCarve Pro & Aspire: top of material vs spoilboard, Material Setup form, and the Gap Above/Below Model settings?

Z-zero is the single most important setup decision in any CNC workflow. The software and your machine must always agree on where Z=0 is.

The Two Z-Zero Options

Material Surface (top of material):

• Z=0 is the top face of the workpiece
• Best for: V-carving, 3D relief, engraving, and any cut where depth from the surface is critical
• Risk: Profile cuts may not go fully through if the material is slightly thicker than measured

Machine Bed / Spoilboard:

• Z=0 is the spoilboard surface
• Best for: Profile cutouts where guaranteed through-cuts matter more than precise surface depth, and for machines with an automatic tool changer, because the spoilboard height is constant regardless of material thickness
• Risk: V-carve and engraving depths will be slightly off if the material thickness is not exact

Pick one house rule and stick to it. A sensible default is Material Surface for V-carving and 3D, and Machine Bed for through-cuts. Whichever you pick must match how you zero the machine. If a roughing pass removes the original top surface, keep a small piece of the original stock nearby to re-zero from after a tool change, or use Machine Bed so you do not need to.

Material Setup Form

On the Toolpaths tab, the Material Setup section shows a summary of your material settings. Click its Set... button to open the Material Setup form. Review it every time you start creating toolpaths, and again whenever the material thickness changes between jobs.

Thickness: The thickness of the material being machined. Use the measured actual thickness (digital calipers), because nominal "3/4" plywood is often 0.70 to 0.74" in reality.

Side Z-Zero: Material Surface or Machine Bed. This must match exactly how you zero at the machine. A mismatch is the number one cause of depth disasters. On a two-sided job this sets Z zero for the current side only.

Clearance (Z1): The height above the job at which it is safe for the cutter to move at rapid speed. Raise it if you have thick material or clamps in the way.

Plunge (Z2): This is a gap, not a rate. It is the height above the material that the tool rapids down to before slowing to the plunge rate. By default it equals Clearance (Z1), which means there are no rapid plunges. Setting it lower than Clearance (Z1) saves time on jobs with many plunge moves.

Gap Above/Below Model (3D Carving)

For 3D relief, Material Setup also shows where the composite model sits in the material:

Gap Above Model: The distance between the top of the model and the top surface of the material.

Gap Below Model: The distance between the bottom of the model and the bottom surface of the material (the base layer beneath the carving).

Rule: Gap Above + Model Thickness + Gap Below = Material Thickness. The model thickness must be less than the material thickness. If the model is taller than the material, use Scale Model Height (the Set... button in Material Setup) or increase the material thickness.

Critical Mismatch Warning

Setting Z Zero to Material Surface in the software but zeroing the machine on the spoilboard (or vice versa) causes every cut to be off by exactly one material thickness. That can ruin the workpiece and break bits. Always verify both settings match, and do an air cut for any new setup.