Help for sign shops

Keep small letters from moving on the last CNC pass

Leave a thin onion skin, cut the small parts first on the final pass, and give small parts a little more space. Most shifting happens in the last few seconds of the cut.

Why small parts move

A small letter has very little area for tape or glue to hold, and tabs on a 1 in letter are hard to place and leave marks to sand off. When the last bit of material is cut away, the part can lift, spin or catch on the bit. If it moves into a neighbor, both parts are ruined.

Onion skin instead of tabs

1. Cut the profile almost to full depth. Stop about 0.01 in to 0.02 in short, so every part is still held all the way around.
2. Run one last full-depth pass of the same profile. The skin is so thin that it leaves no tab mark.
3. Cut the small parts first on that pass and the big ones last, while the sheet is still held well.
4. Keep hold-down good under the small parts: vacuum zones on, or screws or clamps away from the small letters.

Set the onion skin and the cut order in your CAM program (VCarve, Fusion, Carbide Create and others all have a way to set a final pass and the order of cuts).

Leave a little more space

The space between parts must be at least the bit diameter, or the bit cuts into the next part. For very small letters, add a bit of clearance on top, so that a part that shifts at the very end does not get pushed into its neighbor. See router bit size and part spacing.

How NestSigns helps

In NestSigns, type your router bit and part spacing becomes the bit plus 0.05 in clearance. For a job with very small letters you can type a larger part spacing by hand before you nest. The file check marks gaps and thin spots narrower than your bit, and the export (DXF, SVG, PDF, AI or LightBurn) keeps each part as its own closed outline, so your CAM program can set the onion skin and cut order.

Related: All help pages · Router bit size and part spacing · Clean up traced artwork · VCarve nesting · Kerf