Panel Saw or CNC Router: One Job, Both Ways

A shop with a router and a shop with a panel saw can be handed the same cut list and both ask the same question: how many sheets do I buy? The answer is not always the same number, and it is not always the one people expect. This page runs one list through CutOptim both ways, shows the sheet counts side by side, and then says plainly how often free placement actually helped in our tests. The list is made up, which is why the page carries the made-up-data badge.

CNC mode places the same parts freely on the sheet, with a bit-sized gap between them instead of edge-to-edge saw cuts, so a router can use areas a panel saw cannot reach.

What does the same job need on a panel saw and on a CNC router?

For the example job, 4 sheets on the saw and 3 on the router. The saw plan uses 62.0% of the board and the CNC plan 82.6%. The parts, the sheets and the rule that nothing may turn are identical; what differs is that the CNC plan does not have to cut every line from edge to edge, and that its gap between parts is 9 mm instead of 3.

Two other jobs run the same way give a different picture, and they are on this page on purpose. A kitchen job of four base cabinets and a bookshelf needs 3 sheets either way. A third, generated list needs 3 sheets on the saw and 4 in CNC mode.

Sheets are unlimited in all three runs, and no part may be turned, as with a decor board. The numbers are the app’s own results for these lists; a different list gives different ones.

What is the example job?

A shelving wall of 25 pieces in 12 rows, made up for this page: four long boards, two of each, that run nearly the length of the sheet, and eight other rows of doors, panels and strips. Long boards next to mid-size panels are the kind of list where a free layout has room to differ from a saw layout.

The first number runs along the 2750 mm side of the sheet and no part may turn, so the four long boards lie lengthways. The button below loads this list, one sheet size of 2750 × 1830 mm, a 3 mm saw kerf and the parts set not to turn. That gives the panel-saw plan; the next section switches it to CNC mode.

How do you run it both ways?

1. Open the job

   Use the Open in CutOptim button above. It loads the 12 rows, the sheet and the 3 mm saw kerf, with every part set not to turn, which the Grain icon on each row shows.

2. Run the panel-saw plan

   Click Run optimizer. For this list the plan uses 4 sheets. Note the sheet count and the use of the board.

3. Switch on CNC mode

   Open Settings, the first section of the left sidebar in 2D mode, and tick CNC mode (free placement). The saw-only settings are dimmed because they have no effect.

4. Enter the router gap

   The gap between parts is the bit plus the free space you want, for example a 6 mm bit and 3 mm, which is 9 mm. Type 9 in Blade kerf, or use the CNC / router: tool + allowance link under it to enter 6 and 3 separately.

5. Run again and compare

   Run the optimizer once more. This list now needs 3 sheets. The result shows CNC mode: the parts have x and y positions, there is no cutting sequence, and the cut length is the router’s outline path.

Why does the router gap change the result?

Because the gap uses board, and because free placement is a heuristic, not a formula. On the example list the saw plan needs 4 sheets. CNC mode with a 3 mm gap needs 4 and with 6 mm needs 4, then with 9 mm it needs 3. A wider gap did not make the plan worse here; it happened to make a different layout that fits. On the third job in the table the opposite happens: 3 sheets at 3 mm and 6 mm, 4 at 9 mm.

The lesson is not that a wider gap is better. It is that the result of a free layout moves with the gap by a sheet in either direction and cannot be guessed from the parts list. Use the gap your bit and your allowance really give, and read the result for that gap.

How often does CNC mode save a sheet?

Rarely, in our test. We ran generated lists through the app, two sets of rows with parts that may not turn: 8 to 18 rows of mid-size panels, and 8 to 14 rows plus two to four long boards, on four common sheet sizes (2800 × 2070, 2440 × 1220, 2750 × 1830 and 2770 × 1400 mm), with a 3 mm saw kerf for the saw plan and a 9 mm gap for the router plan. Of the 180 jobs where both plans placed every part, CNC mode needed fewer sheets in 1, the same number in 164 and more in 15.

Two more observations. With the same 3 mm gap for both plans, CNC mode gave the same sheet count as the saw plan in every one of the same 180 jobs. So most of the difference you see comes from the router gap, not from where the parts sit. And jobs where CNC mode wins by a sheet are rare, which is why this page uses one of them as its example: it shows the effect, it does not describe the average. The extra sheets come from the wider gap: at the same gap as the saw, CNC mode never needs more, because it also tries the saw layout.

These are generated jobs, not customer jobs, and the share of wins would be different for other kinds of lists. The guide on nesting panels for a CNC router shows a real job where CNC mode did save a sheet, and explains when that happens: tight stock, decor that cannot turn, and narrow offcut strips. This page’s point is the check: run your own list both ways.

What does a CNC plan give you, and what does it take away?

It gives you a layout a router can cut and a DXF (CNC) with every sheet in one drawing and the part names; your CAM software adds the toolpaths. The PDF, Excel, SVG and the labels work as before, and the PDF says CNC plan so nobody mistakes it for a saw plan. The DXF options and the CAM import are in the guide on DXF for CNC and CAM.

It takes away the saw cutting sequence. A free layout has no edge-to-edge cuts, so there is no list of cuts to follow, and the plan cannot be cut on a panel saw. If part of the job goes to a saw, run that part in saw mode. The CNC mode page in the docs lists what changes in the result.

Common mistakes

• Comparing with different gaps without saying so. A 3 mm saw plan against a 9 mm router plan answers a different question than the same gap on both. Know which one you are comparing.
• Assuming CNC mode is the better plan. In our test it was the same or worse in 179 of 180 jobs. Look at the sheet count of your own list.
• Reading only the sheet count. The use of the board matters when you plan to keep the offcuts: in the example the saw plan leaves its fourth sheet mostly empty, a 2750 × 1433 mm offcut, while the largest offcut of the CNC plan is 2750 × 358 mm.
• Cutting a CNC plan on a panel saw. It has no edge-to-edge cuts and cannot be sawn.
• Using the saw kerf as the router gap. The gap is the bit plus the allowance. A 3 mm gap is not a 6 mm bit.

When should you stay with the saw plan?

When you cut on a panel saw, a table saw or a track saw, because a free layout usually cannot be cut edge to edge. And when your list does not look like the one that wins: cabinet carcasses and similar parts lists tended to give the same sheet count in our test, in which case the saw plan is the simpler and safer choice, with a cutting sequence you can follow.

Number of sheets and use of the board go together: the use is the area of the parts divided by the area of the sheets, so with the same sheet size fewer sheets always means a higher use for the same parts. Compare the sheet count and the offcuts that remain, and look at your own list, not at the examples on this page.

Finally, change only the gap between the two runs and leave everything else the same, the parts, the sheet and the rule against turning. Then any difference really comes from the gap, which protects you from misreading the result for your own job.