- Pick one definition of utilisation and use it for every job
- Read the part area and the material consumed from the nest
- Raise it: nest jobs of one material and thickness together, allow part-in-part and rotations, and nest on remnants first
Three ways to count, and a fourth
| Count the material as | Utilisation = | Where you meet it |
|---|---|---|
| Whole sheets | part area ÷ (sheets × sheet area) | The figure Zorocut shows per sheet and per job after a nest; CypNest's “By whole plate size” material summary |
| Used length | part area ÷ (full sheets + the last sheet up to its used length) | Zorocut's benchmarks; fair for comparing nesters |
| Sheets minus the kept offcut | part area ÷ (sheets − free strips of at least 100 mm both ways) | Zorocut's net-area billing when offcuts are kept |
| The parts' boxes | part area ÷ bounding rectangle of the nested parts | CypNest's “By parts bounding rectangle” summary |
Part area is the net area: the outline minus its holes, so a flange with a large hole counts only its metal. An example: on a 2,500 × 1,250 mm sheet (3.125 m²) the parts have 2.0 m² of net area and the last one ends 2,000 mm along the sheet. Over the whole sheet that is 64 %. Up to the used length (2.0 m × 1.25 m = 2.5 m²) it is 80 %. If the 500 × 1,250 mm strip goes back on the rack, 2.5 m² is consumed and the figure is 80 %; if it goes to scrap, 64 %. One nest, two answers (example).
What the numbers mean
- About 70 %: what Hypertherm calls a typical industry nest, with 30 % scrap.
- Up to about 90 % on rectangles: Zorocut reached 89.36 % on our 117-rectangle test job and 71.11 % on a mix of L-brackets, plates and flanges, with 3 mm spacing and a 10 mm margin, on the used-length definition (our runs, 3 s).
- 68.60–92.24 %: the best published research method on the ESICUP benchmark sets, with zero spacing and 20 minutes of search. The shapes decide much of the figure.
- Low on a small job: two parts on a big sheet read low on whole sheets however well they are nested. That is an offcut to keep, not a bad nest.
How to raise it
- Nest jobs together. Hypertherm's example is taking all the quarter-inch mild steel due in the next 10 days and nesting it at once: more parts, more ways to fill the gaps. Zorocut keeps the customer's name on each part, so one nest can carry several orders.
- Fill the holes. Small parts in the holes of large ones turn slugs into parts; CypNest has a “Nest inside first” option for the same reason, and Zorocut does it on every nest — see part-in-part nesting.
- Allow rotations. Zorocut lets each part turn in 45° steps by default; limit it to 180° or none only where the grain or a brushed finish needs it — CypNest's manual gives the same reason for its 180° option.
- Use remnants first. A strip from the last job is metal already paid for; see remnants.
- Keep the spacing as small as your test cuts allow, and no smaller. A 100 × 50 mm part with 3 mm spacing takes a 103 × 53 mm box (5,459 mm²); with 6 mm, 106 × 56 mm (5,936 mm²) — 8.7 % more metal per part (example). See part spacing.
Utilisation and the price
The figure matters most where it reaches the price. Zorocut bills material three ways: the part rectangle plus spacing, the net part area divided by the nest's utilisation, or the whole sheets used. In the net-area mode a free strip you keep is not counted as consumed, so the customer does not pay for metal that goes back on your rack; set offcuts to scrap and the whole sheets count. CypNest's report offers the same choice between whole plates, the parts' bounding rectangle and their envelope area. See material cost in a quote.
Sources
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