Key takeaways
- Material is 30–50% of the cost of a sheet metal part. Yield is the single largest lever on the number at the bottom of your quote, and it is decided on the drawing, not on the shop floor.
- Ask for the nest plot, not the utilisation percentage. A single number hides whether the 18% you are paying for is skeleton, edge trim or usable remnant.
- Rectangular nesting understates, true-shape nesting recovers. Genuine true-shape nesting with free rotation typically adds 5–12 points of utilisation over a grid layout.
- Sheet size harmony beats clever software. If your panel is 1,020 mm wide on a 1,250 mm sheet, you have already lost 230 mm regardless of the algorithm.
- Cut-to-length coil is a different economics. A published case moved ten part numbers from sheet to coil and took scrap from 15.9% average to 2–3% — but only for the top 20% of parts by volume.
- Fix thickness and material first. A nest that mixes gauges or grades is two nests, and the second one usually runs at half the utilisation.
A telecom OEM asked us to requote a 400-cabinet programme that had been running for two years at a competitor. The part geometry was sensible, the volumes were healthy, and the price was 11% above where the customer's target landed. We did not change a single dimension. We re-nested the three largest panels onto a different standard sheet, harmonised two flange widths that were fighting the sheet boundary, and moved the four highest-volume flat parts to a cut-to-length coil. Material utilisation on the main nest went from 71% to 84%, and the unit price came down 8.6% without touching the design intent. Sheet metal nesting is the least glamorous and most reliable place to find money in an enclosure programme.
This guide explains where material goes in a cutting nest, what the software is actually optimising, the six levers that move yield and what each one costs you elsewhere, when coil beats sheet, how to read the utilisation number on a quote, and a five-step review you can run with your supplier on any existing part. Pair it with our sheet metal enclosure cost guide for the rest of the cost structure, and with the DFM design guide for the drawing rules that make the nest work.
Where Your Material Actually Goes
Buyers are usually shown a single utilisation figure. The useful version splits it up, because each bucket has a different owner and a different fix.
| Destination | Typical share of the sheet | Who controls it | Can it be recovered? |
|---|---|---|---|
| Finished part area | 60–80% | The design | No — this is the product |
| Skeleton (web between parts) | 8–20% | Nest layout, part spacing, common-line cutting | Partly, with true-shape nesting |
| Edge trim and clamp margin | 3–8% | Sheet size choice, machine clamping | Only by changing the sheet size |
| Usable remnant | 0–15% | Remnant library discipline | Yes, on the next job |
| True scrap (offcut too small to use) | 4–15% | Everything above | No |
The number that matters is the last row, not the first. A supplier quoting 85% utilisation on a part whose remnants never get used is charging you for 15% of steel you will never see.
What Nesting Software Really Optimises
Three things, in this order: how the part outline is treated, whether parts can rotate freely, and whether adjacent parts can share a cut.
- Rectangular nesting treats each part as its bounding box. It is fast, and it is what a spreadsheet quote assumes.
- True-shape nesting uses the actual perimeter, tests multiple rotations and lets neighbours interlock. On a typical enclosure part with cut-outs and notches it recovers 5–12 points over a rectangular layout.
- Common-line cutting lets two parts share a single cut path instead of two parallel cuts with a web between them. It removes the skeleton between those parts, reduces pierce count and shortens the cut path — but it means both parts inherit that shared edge, so the shared dimension tolerance has to be acceptable to both.
Two constraints the software cannot override. Grain direction: sheet has a rolling direction, and a bend parallel to the grain is where cracks start, so if your drawing mandates grain the free-rotation advantage shrinks. Our tolerance guide covers where that shows up dimensionally. Clamping margin: every machine needs a strip of sheet it can hold, typically 10–20 mm on a laser and more on a punch, and that strip is scrap.
Six Levers That Move Yield
| Lever | Typical yield gain | What it costs you | Best for |
|---|---|---|---|
| True-shape nesting with free rotation | +5–12 points | Longer programming time | Complex 2D profiles with cut-outs |
| Common-line cutting | +2–6 points | Shared edge tolerance; both parts cut together | Rectangular panels, doors, blanking plates |
| Sheet size re-selection | +3–10 points | Possible price break change | Parts near a standard size boundary |
| Mixing part numbers in one nest | +6–15 points | All parts must share material and gauge; scheduling complexity | Programmes with several flat parts |
| Remnant library management | +3–8 points | Discipline, racking, tracking | Job shops and mixed programmes |
| Cut-to-length coil | +10–14 points | Volume commitment, tooling, narrow width range | The top 20% of parts by volume |
Notice that four of the six are commercial or organisational, not technical. Two suppliers running the same laser can differ by ten points of utilisation purely on whether they keep a remnant rack.
Sheet vs Coil: When Cut-to-Length Wins
The published case that convinced a lot of European OEMs came from an Italian fabricator that moved ten part numbers from standard sheets to a coil-fed punch and laser line. Run from sheet, those ten codes averaged 15.9% scrap. Run from a coil slit to the exact part width, scrap fell to 2–3% — a saving of 78.8 tonnes of raw material in one shift, worth about €47,600 per shift, or roughly €95,200 a year on two shifts.
The catch is the Pareto rule the same case documented: about 20% of part numbers consume 80% of the sheet metal processed. Those are the coil candidates — high volume, stable geometry, rectangular-friendly. The remaining 80% of part numbers use the other 20% of the material and belong on sheet, where flexibility is worth more than yield. If your supplier proposes coil, ask which part numbers and check them against your own volume data.
Sheet Size Harmony: Why Your Panel Dimensions Matter
| Standard sheet | Common in | Implication for enclosure panels |
|---|---|---|
| 1,250 × 2,500 mm | Europe, Asia | Door blanks up to ~1,180 mm wide nest cleanly two-up |
| 1,500 × 3,000 mm | Europe (large format lasers) | Suits 1,200 mm wide cabinets; check machine capacity |
| 1,000 × 2,000 mm | Asia, job shops | Two 600 mm panels across, but a 1,020 mm panel wastes a strip |
| 4 × 8 ft (1,219 × 2,438 mm) | North America | Watch metric conversions — 1,200 mm parts leave a 19 mm sliver |
| 5 × 10 ft (1,524 × 3,048 mm) | North America | Good for 1,500 mm panels; not all lasers take it |
The rule is simple and brutal: a part dimension that leaves a strip narrower than the next useful part is a part dimension that is being paid for as scrap. A 1,020 mm wide panel on a 1,250 mm sheet leaves 230 mm — wide enough for a second useful part, so it is fine. A 1,140 mm panel on the same sheet leaves 110 mm, and that is usually true scrap.
Reading the Yield Number on Your Quote
Ask for utilisation per sheet, per part number, and ask which method produced it.
| Part type | Fair utilisation band | Red flag |
|---|---|---|
| Simple rectangular blanks, doors, panels | 82–92% | Below 78% on a repeat job |
| Complex brackets with cut-outs and notches | 62–78% | Below 58% without an explanation |
| Mixed nest across several part numbers | 78–90% | A single blended number for the whole order |
| Round or radiused parts | 55–72% | Above 80% claimed — geometrically unlikely |
| Cut-to-length coil | 95–98% | Below 92% |
A blended number across an entire order is the most common way a weak nest gets hidden. A 90% average can be a 95% panel carrying a 60% bracket.
Seven DFM Rules That Improve Yield
- Put the panel dimensions on a 50 mm module. Parts that tile are parts that nest.
- Harmonise flange widths and hole sizes across the family. Fewer distinct features mean tighter interlocking and fewer tool changes.
- Standardise bend radii to one value per thickness. It helps the brake setup as much as the nest, and it is covered in the bending guide.
- Allow free rotation unless grain direction is genuinely required — say so explicitly on the drawing, because silence is usually read as "grain fixed".
- Design mirror-image parts as mirror images. Left and right brackets that are truly mirrored interlock in a nest; two different brackets do not.
- Accept common-line edges where the shared tolerance is acceptable. Removing the web between two panels is free yield.
- Keep one material and one gauge per nest. Mixed gauges force separate nests, and the small one usually runs at half the utilisation of the large one.
The Five-Step Yield Review
- Ask for the nest plot for every part number, with utilisation stated per sheet. If the supplier cannot produce it, they are not measuring it.
- Group parts by material and gauge. Anything that can share a nest should share a nest.
- Check every large panel against the standard sheet sizes in the destination market. A 30 mm change in a panel width is usually invisible to the product and worth several points of yield.
- Run the Pareto analysis on annual volume. The top 20% of part numbers by tonnage are the only coil candidates worth evaluating.
- Re-quote after harmonisation, then lock the drawing. Yield gains are lost the moment someone adds a one-off flange to a released panel.
Frequently Asked Questions
What utilisation should I expect on my enclosure panels?
For straightforward rectangular panels and door blanks, 82–92% is a fair band. For complex brackets with cut-outs, 62–78% is realistic. Anything quoted as a single blended percentage across a whole order should be broken down per part number before you accept it — the blend is where a poor nest hides.
Does a higher utilisation always mean a lower price?
Usually, but not always. Common-line cutting raises yield while tying two parts to the same cut, which reduces scheduling flexibility; mixing part numbers raises yield but increases work-in-progress. Ask what changed to get the gain, and check it against your delivery pattern.
Is coil-fed production worth it for my volumes?
Only for the high-volume, dimensionally stable part numbers. The reference case showed scrap falling from 15.9% to 2–3% on ten codes, but those codes were chosen precisely because they consumed the bulk of the tonnage. Below a few thousand pieces a year per part number, the scheduling and tooling overhead usually eats the material saving.
Can I keep my remnants for my own future orders?
Yes, and you should say so in the PO. Remnant ownership and tracking is a commercial term, not a technical one. Without it, offcuts quietly become the supplier's stock, and the yield gain on your next job disappears.
Does nesting affect quality?
It can, through heat. A tight nest concentrates heat in a small area and can distort thin sheet or produce parts that move as the skeleton releases. A competent nest leaves enough web and sequences the pierces to spread the heat — worth asking about on anything under 1.2 mm. Our quality control and inspection guide sets out what to check on first article.
Where to Go Next
Yield is one line of a quote. The material selection guide determines what that line costs per kilogram, and laser cutting vs stamping determines which process reads the nest at all. If the parts are still in design, run this review inside the prototype-to-production guide before the drawing is released — and if the programme is stainless, note that the yield lever is worth three to four times more per point than it is on carbon steel, which is exactly why our hygienic washdown builds are nested before they are quoted.
Yield improvement is also the cheapest alternative to a fixture — our tooling investment guide puts it first on the list for exactly that reason.