What nesting means
Nesting is the arrangement of flat parts on a sheet of material before cutting. The goal is simple: cut all required pieces from as few sheets as possible and leave as little scrap as possible. In sheet metal production the material is often the largest cost item, so a few percent of better utilization directly lower the price of every part.
Nesting software takes the part drawings (usually DXF), the required quantities and the available sheets and calculates where each piece goes. The result is passed to the cutting machine – for example as one DXF file per sheet.
Rectangular vs. true-shape nesting
The simplest nesting treats every part as its bounding rectangle. It is fast, but irregular parts such as flanges, brackets or L-shapes waste a lot of material between them.
True-shape nesting works with the real outline of the part. Parts can interlock, small parts can be placed into holes of large ones and concave shapes can be paired. SRSA NEST uses true-shape nesting based on No-Fit Polygons.
Parameters that matter
- Gap between parts – the minimum distance between two parts; it depends on the kerf width and the cutting technology.
- Sheet margin – the distance from the sheet edge that must stay free, for example for clamping or an uneven edge.
- Rotation – which angles a part may be rotated by. A finer step usually gives better utilization but takes longer to compute; rolling direction or a brushed surface may forbid rotation.
- Mirroring – flipping a part. It helps with asymmetric parts but must not be used where the front and back side differ.
- Priority – urgent parts are nested first so they end up on the first sheets.
Sheet utilization
Utilization is the ratio of the area of all parts to the area of the sheets used. Because the last sheet is often only partly filled, SRSA NEST also reports utilization with the last sheet counted only up to the used length – the rest is a usable remnant, not scrap.
Remnants
A remnant is the unused part of a sheet that is large enough to be cut later. Good nesting software separates the remnant with a straight cut, stores it in stock and uses it first in the next job. In SRSA NEST remnants can have any shape (imported from DXF, with holes as defects) and get a high priority automatically.
Manual vs. automatic nesting
Experienced programmers can nest by hand, but it takes time and the result depends on the person. Automatic nesting produces a good layout in seconds and tries thousands of variants. The best practice is a combination: automatic nesting first, then manual fine-tuning where production needs it – which is exactly how SRSA NEST works.
Try it on your own parts: download SRSA NEST, import your DXF files and compare the utilization with your current workflow.