How does the Prism Carving toolpath work in VCarve Pro & Aspire for raised prismatic lettering and signs?

Overview

Prism Carving uses an angled tool (usually a V-bit) to create a raised, beveled "prism" shape on top of the selected vectors, similar to a hand-carved look. The tool profiles at a given depth, leaving sharp angled sides on the shape. It is most often used on lettering, and it is often paired with a Profile or Pocket toolpath to carve the vertical edge around the shapes or clear out the material between them.

This is the go-to toolpath for raised lettering on signs where you want a premium raised-bevel look. It is available in both VCarve Pro and Aspire.

How It Works

Prism Carving cuts angled walls around the selected vectors, using the tool's included angle. The result:

• The shape stays raised, with angled sides running down from the vector area
• The angled walls from opposite sides of a stroke meet in a sharp ridge when the Prism Depth is deep enough (a "full prism")
• If the Prism Depth is too shallow the walls do not meet and the shape keeps a flat top (a "truncated prism")

The prism shape is defined by the vector shape, the tool angle, and the Prism Depth.

Workflow

1. Select the vectors that define the shapes to be raised (text, logos, borders)
2. Open Prism Carving from the Toolpaths tab
3. Set Start Depth: usually 0 (cutting from the surface). If cutting into a pocket or stepped region, enter that depth.
4. Select the Tool: a V-bit, usually 60° or 90°
5. Click Set Depth for Full Prism (with the vectors and the tool already selected). It sets Prism Depth to the minimum that gives a full point on the widest part of the selection. You can also type a Prism Depth yourself
6. Choose the Cut Direction (Conventional or Climb; the material and tool largely decide)
7. Calculate

The Set Depth for Full Prism Button

Click it after selecting both your vectors and your tool. The software sets the Prism Depth to the minimum needed so the angled walls meet at a sharp point on the widest part of the selected vectors, giving a complete prism with no flat top.

The depth is set by the widest point of the selection (W) and the tool angle (A). As a guide from the geometry, a full point needs a depth of about half the widest width divided by the tangent of half the tool angle. For a 1" wide stroke that is about 0.5" for a 90° tool and about 0.87" for a 60° tool. Always let the button calculate it for your real design.

If the depth is too shallow, the prism is truncated and keeps a flat top. If it is deeper than needed, you waste machining time.

Pairing with Pocket or Profile

Prism Carving only cuts the beveled walls. To complete the sign you typically need:

• Pocket toolpath to clear the flat background between letters down to the prism base depth (select a boundary rectangle around the design plus the prism vectors as islands)
• Profile cutout to cut the sign to its final shape

Typical 3-toolpath prism sign setup:

1. Prism Carving (V-bit): cuts the beveled walls around letters
2. Pocket (end mill): clears the background between letters to the same depth as the prism base
3. Profile cutout (end mill): cuts the sign shape from the material

Prism Carving does not offer a "Project toolpath onto 3D Model" option. For raised lettering on a curved surface, build the letters into the 3D model instead.

Tool Requirements

Prism Carving is demanding on tool accuracy:

• Sharp tooling is essential: a dull V-bit leaves torn, fuzzy prism edges
• Measure your V-bit carefully: even a 1 to 2° deviation from the rated angle changes the prism geometry significantly, as does an error in the tip diameter
• Enter the exact tool angle and diameter in the Tool Database before calculating
• Common angles: 60° (steeper bevel, deeper cut) and 90° (gentler slope, shallower cut)
• Do a test cut on scrap before committing to the final material

Prism Carving vs V-Carving vs Chamfer

Common Mistakes

• Not using Set Depth for Full Prism: guessing the depth gives a truncated (flat-topped) prism
• Inaccurate tool parameters: the bevel width does not match expectations. Measure the bit carefully.
• Not adding a clearance pocket: the prism cuts beautifully around each letter but the flat background between them is not cleared
• Using a 90° bit for narrow letters: the wide angle creates a very low, subtle bevel. Use a 60° or 45° bit for a more dramatic bevel on narrow strokes
• Expecting Prism Carving to work like V-Carve: they produce opposite visual results. V-Carve cuts in. Prism raises up.