Guillotine cutting vs CNC nesting for steel plate
There are two ways to lay out rectangular parts on a steel sheet. Which one is right depends on the machine that will cut it.
Guillotine layouts
In a guillotine layout every cut runs straight across from one edge of the piece to the other. The sheet is first cut into strips, then each strip into parts. This is how a guillotine shear, a plate saw or a panel saw works: the blade cannot stop halfway or turn a corner.
- Use it for: shears, saws, and any process where the operator makes straight through-cuts by hand.
- Advantages: simple cutting sequence, square edges, and leftover pieces are clean rectangles that are easy to store and reuse.
- Trade-off: parts have to line up in rows and columns, so a little more plate is usually left over than with free nesting.
CNC nesting
On a CNC plasma, laser, oxy-fuel or waterjet table, the torch or head can start and stop anywhere and follow any path. Parts do not need to line up, so they can be packed more tightly, with rotated parts filling the gaps between larger ones.
- Use it for: CNC profile cutting tables.
- Advantages: usually the highest material use, especially when a job mixes many part sizes.
- Trade-off: the remaining plate is often an irregular shape, so offcuts are harder to reuse, and the parts must be cut by a machine, not by hand.
Kerf and edge trim still apply
Both methods lose material on every cut. Plasma and oxy-fuel kerf grows with plate thickness, and most shops keep a strip around the sheet edge for clamping or to clean up the mill edge. Set both before you nest, or parts that fit on screen will not fit on the table. See the kerf guide for typical values.
Grain and rolling direction
Rotating a part 90° often saves plate, and the SteelCutList plate optimiser turns parts automatically whenever that fits more on the sheet. If a part must follow the rolling direction — for example because the drawing calls for it on a bend — check that part on the plan before cutting.
Rectangles and real shapes
Most structural plate parts — base plates, cleats, stiffeners, splice plates — are rectangles or close to it. For shaped parts, the common approach in simple nesting tools is to reserve the part's bounding rectangle. SteelCutList can import a DXF for each part: it nests the part by its bounding rectangle, draws the real outline on the plan and the PDF, and uses the true area with holes removed for the part weight.
Which one should you pick?
| Machine | Layout |
|---|---|
| Guillotine shear | Guillotine |
| Plate saw / panel saw | Guillotine |
| CNC plasma or oxy-fuel table | CNC nesting |
| Laser or waterjet | CNC nesting |
In the plate optimiser, choose Guillotine / shear / saw or CNC nesting (plasma, laser) under Cutting method. You can run the same job both ways and compare how many sheets each needs.