LaserCanvas
Nesting parts to waste less sheet
Pack the large parts first and fill gaps with small ones, leave at least one or two kerf widths between parts so they cannot join up, and rotate only where grain direction allows. Automatic nesting does the tedious part; the constraints that matter — grain, defects, which edge shows — are still yours.
Why gaps matter more than they look
Two parts placed exactly adjacent share no material. The beam removes a kerf from between them, so each loses half a kerf and both come out undersized. Worse, if they are closer than a kerf the cuts merge and the two parts become one piece with a ragged join.
- Minimum: one kerf plus a margin. In practice 1–2 mm between parts is a sensible default.
- More for thick material, where the cut is wider and heat spreads further.
- More again for anything that will char — adjacent cuts in thin ply can scorch each other’s edges.
Shared cut lines: usually not worth it
The tempting trick is to have two rectangles share one edge so the laser cuts it once — half the time, no wasted strip. It works on paper and disappoints in practice:
- Both parts end up half a kerf small on that edge, and the error is on one side only, so the part is no longer symmetric.
- The shared cut releases both parts simultaneously, so both can shift while the rest of the sheet is still being cut.
- Any bow in the sheet shows up as a mismatch along that one edge.
It is a reasonable technique for rough parts where fit does not matter and material is expensive. For anything that assembles, leave the gap.
What automatic nesting can and cannot know
| It handles | You handle |
|---|---|
| Packing parts into the smallest area | Which parts may be rotated at all |
| Rotating to fit where allowed | Grain direction on visible or load-bearing parts |
| Keeping parts inside the sheet | Avoiding knots, voids and damaged areas |
| Maintaining the spacing you set | Which face is the good face |
Grain is the one that catches people. A box side rotated 90° to fit is structurally different from one that is not — plywood is much stronger along the face grain, and a finger joint whose tabs run across the grain snaps when pressed home. If a part must keep its orientation, lock it before nesting.
Practical habits
- Cut a test piece from the offcut first, not from the middle of a fresh sheet.
- Keep offcuts and label them with thickness and material. Most small parts come from offcuts, not sheets.
- Put the parts that must be perfect in the flattest, cleanest region of the sheet, and the forgiving ones near the edges.
- Cut inner holes before outer outlines, so parts stay held until the last moment.
- Group by operation, not by part. All the engraving, then all the scoring, then all the cutting.
Bigger than the bed
Parts longer than the work area can be cut in tiles if the machine has a passthrough slot, or split deliberately into sections joined by a finger joint or a scarf. Tiling relies on moving the material precisely between tiles — registration marks scored in the first tile give you something to align against for the second.
Every tile must fit inside the machine’s travel, including the registration marks. A tile that is 2 mm too wide fails at the far end of a long job, which is the worst time to find out.
Common questions
How much space should I leave between nested parts?
At least one kerf so the cuts cannot merge, and in practice 1 to 2 mm to allow for char and for any bow in the sheet. Thicker material wants more, because the kerf is wider and heat spreads further. Zero spacing makes every part a kerf undersized.
Is sharing a cut line between two parts a good idea?
Rarely. Both parts come out half a kerf small on that edge, both are released at the same moment so both can shift, and any bow in the sheet shows as a mismatch. It saves time and material on rough parts; for anything that has to assemble, leave the gap.
Can nesting rotate my parts freely?
It can, but you may not want it to. Plywood is much stronger along the face grain, and a finger joint whose tabs run across the grain will snap. Parts where grain direction or the visible face matters should be locked before nesting, and the packer works around them.
How do I cut something longer than my machine?
Either use a passthrough slot and cut it in tiles, moving the material between them, or design the part in sections joined by finger joints. Tiling needs registration marks scored in the first tile to align the second against, and every tile must fit within the machine travel including those marks.