CNC nesting vs panel saw
A panel saw, table saw or track saw cuts straight through the whole piece. A CNC router can follow any path. That difference lets a CNC layout lock parts together in ways a saw cannot separate. Sometimes it saves a sheet; on most cabinet lists it saves nothing.
Guillotine cuts
On a saw every cut runs from edge to edge across the piece being cut. The first cut splits the sheet in two, each piece is split again, and so on. A layout that can be cut this way is called guillotine, and it is CutGrid’s default.
The rule is strict. If four parts surround a fifth like a pinwheel, there is no straight line across the sheet that misses every part, so a saw has nowhere to start.
The same parts, cut with a saw
Three tops at 900 × 560 mm, two shelves at 764 × 300 mm and two panels at 600 × 600 mm, on 2440 × 1220 mm sheets with a 3 mm kerf and 10 mm trim. The parts are 0.9 sheets of area.
With guillotine cuts, CutGrid’s layout needs 2 sheets and leaves 54.8% of the board as waste.
| Part | Width (mm) | Height (mm) | Qty |
|---|---|---|---|
| Top | 900 | 560 | 3 |
| Shelf | 764 | 300 | 2 |
| Panel | 600 | 600 | 2 |
Layout produced by CutGrid’s optimizer for this example. Coloured blocks are parts, dashed areas are offcuts, and the outer band is trim.
- Top
- Shelf
- Panel
The same parts, nested for CNC
In CNC mode the parts may interlock. The same seven parts fit on 1 sheet at 9.6% waste, which is proven to be the minimum. There is no sequence of straight through-cuts that separates this layout, so a panel saw could not cut it.
This example keeps the 3 mm kerf so that only the cutting method changes. On a router the kerf is the bit diameter, often 6 mm, which widens every gap and can change the result. Run your own list with your own bit size.
Layout produced by CutGrid’s optimizer for this example. Coloured blocks are parts, dashed areas are offcuts, and the outer band is trim.
- Top
- Shelf
- Panel
How often CNC nesting wins
Less often than you might expect. On our benchmark of 54 test lists, guillotine layouts used 805 sheets in total and CNC nesting 801, against a lower bound of 733. Rectangular cabinet parts already pack well with straight cuts; CNC nesting pays off on awkward mixes of sizes like the one above.
CutGrid’s CNC mode starts from the best guillotine layout and keeps a free layout only when it is at least as good, so switching it on never costs a sheet.
Which to choose
Choose guillotine if any part of the sheet will be cut on a saw, even if a CNC does the rest. Choose CNC nesting only when the whole sheet goes on the router. When a sheet in a CNC plan cannot be separated with straight cuts, the PDF shows no cut sequence for that sheet.
Common mistakes
Using CNC mode in a saw shop
A CNC layout may be impossible to cut with straight cuts. If the sheet goes to a panel saw, keep guillotine.
Keeping the saw kerf on a router
On a CNC the kerf is the bit diameter, typically 6 mm or more. Set it, or the cutter eats into neighbouring parts.
Expecting a saving on every job
On standard cabinet lists the guillotine layout is usually already as good. Compare both on your own list.
Forgetting hold-down
Small parts cut free on a router can move. Tabs and vacuum zones are set in your CAM program, not in the layout.
Questions
- What is nesting in CNC?
- Arranging parts on a sheet so a router can cut them with as little waste as possible, without the rule that each cut runs from edge to edge.
- Is CNC nesting always better?
- Never worse in CutGrid, because it starts from the guillotine layout. On typical cabinet lists it often finds the same number of sheets.
- Can I export the CNC layout?
- Yes, as a DXF on the Expert plan. The file contains part rectangles and names; toolpaths, tabs and lead-ins are added in your CAM software.