Sheet utilization and order yield are not the same
- Sheet utilization: the share of one full sheet covered by parts. It tells you how good the layout is.
- Order yield: the area of all the parts divided by the area of all the sheets the order consumes. It includes the partly used last sheet, so it is what your material cost depends on.
Where the material goes
- Edge margin for clamping and the sheet's own imperfect edges.
- The gap between parts: kerf plus the web needed to keep the skeleton stable.
- Part shape: round and irregular parts leave more scrap than rectangles.
- The last sheet of the order, and remnants that may or may not be reused.
Estimate it step by step
Enter your sheet size, part size, gap and edge margin in the sheet nesting calculator. It tries both orientations and mixed layouts and returns parts per sheet, utilization and the sheets needed for your quantity. For irregular parts, use the bounding rectangle for a conservative estimate, or your nesting software when you have it.
Then convert the result into the waste percentage of the laser cutting cost calculator, which prices material by area and adds that percentage on top.
Ways to reduce scrap
- Nest different parts of the same thickness together to fill the gaps.
- Choose a sheet size that matches the part dimensions, when your supplier offers several.
- Use common-line cutting for straight-edged parts if your machine and process allow it.
- Label and store useful remnants, and decide whether you charge them to the job.
Formula
- Sheet utilization = Parts per sheet × Part area ÷ Sheet area
- Sheets needed = ⌈Quantity ÷ Parts per sheet⌉
- Order yield = Total parts area ÷ (Sheets needed × Sheet area)
- Waste % for quoting = (Sheets area ÷ Parts area − 1) × 100
Worked example
Illustrative example: 500 parts of 300 × 200 mm (figures are made up for the explanation)
- 1Sheet 2,500 × 1,250 mm, 10 mm gap and 10 mm edge margin → 45 parts per sheet, 86.4% utilization
- 2500 parts ÷ 45 = 11.1 → 12 sheets, with only 5 parts on the last one
- 3Parts area 500 × 0.06 m² = 30 m²; sheets area 12 × 3.125 m² = 37.5 m² → order yield 80%
- 4Waste % for quoting: (37.5 ÷ 30 − 1) × 100 = 25% (15.74% if you reuse the remnant of the last sheet)
- 5At 95 per sheet: buying 12 sheets costs 1,140, or 2.28 per part; charging only the parts' area would give 912
Use about 25% waste for this order. Charging only the parts' area would leave 228 of material unpaid, and using the 86.4% sheet utilization alone, about 84.
The example is illustrative. Its numbers are checked by automated tests.
Assumptions and limitations
- Rectangular parts and a grid layout. Real nesting can do better, especially with mixed or irregular parts.
- The sheet price and sizes are illustrative, not supplier prices.
- Whether a remnant counts as waste depends on whether you actually reuse it.