How sheet metal nesting cuts laser part cost

The sheet is the bill, the beam is the rounding

A 1,250 × 2,500 mm sheet of 2 mm CRCA carries 3.125 m² of steel and weighs 49.1 kg at 15.7 kg/m² per millimetre of thickness. A 300 × 200 mm bracket drawn on that sheet needs 0.06 m² of net area. Everything else the customer pays for comes from how many of those brackets the nest puts on the sheet: 48 on a tight grid, 33 on a nest drawn with 50 mm of clear margin all round. Sheet metal nesting fixes that count before any machine rate is applied, and no cutting speed recovers it afterwards.

Same machine, same assist gas, same 5 seconds of beam time per part. One nest uses 92% of the sheet and the other 63%, and a 330-part order needs 10 sheets instead of 7.

Beam time is smaller than most buyers expect. The bracket's cut path is roughly 1,250 mm: a 1,000 mm outline plus four Ø10 mm holes. At a deliberately modest 15 m/min on 2 mm mild steel, that is 1.25 m ÷ 0.25 m/s, or 5 seconds, and five pierces add a second or two. Loading the sheet, unloading the skeleton, and walking the parts to deburring are measured in minutes. Sheet metal nesting is therefore a material decision before it is a machine decision, and the arithmetic fits on one line of a quotation.

The practical consequence is uncomfortable for anyone who buys on cut rate. A supplier who quotes a lower rupee-per-metre rate on a poor nest can still be the more expensive supplier, because the metre rate only touches the part of the cost that was already small.

What the nest actually decides

Five things come out of the nest file, and only the first is usually discussed.

Parts per sheet. The pitch is the part envelope plus the web. That single number, multiplied across and down the usable sheet, sets yield.

Pierce count. Each contour, hole and slot needs a pierce unless it is entered from an existing cut. On 2 mm sheet a pierce is cheap; on 6 mm plate it is 1.5 seconds or more, which is why thick-plate nests are judged on pierce count and thin nests are judged on area.

Skeleton stability. The remaining web of sheet has to hold every part in place until the sheet leaves the bed. A skeleton that splits into pieces drops onto the slats, tilts, and stops the cut.

Heat density. Parts packed at a 3 mm pitch in one corner of the sheet cannot shed heat between passes. The web lifts, dross returns on the next contour, and flatness drifts.

Common-line cutting. Where two parts share an identical straight edge, one cut can serve both instead of two contours with a web between them. On a grid of 100 mm squares the cut length per part falls from 400 mm to about 210 mm, which is why a repetitive part is nested edge to edge and a varied one is not.

Only one of those five is visible in a STEP file, and that is why a nest review belongs in the quotation rather than in the last week before dispatch.

Rapid travel is the part of machine time that nesting does influence directly, and it is worth understanding why it rarely decides anything. A head moving from one contour to the next clears a 304 × 204 mm pitch in roughly 0.2 seconds at typical traverse speeds, so even a hundred of those moves adds up to about 20 seconds across the sheet. It matters on a program with 4,000 tiny parts and it is noise on a bracket nest. The order of operations, by contrast, decides whether the cut finishes at all.

Nesting parameters that move the quote

Worked: 330 brackets a month from one sheet size

Take the 300 × 200 mm bracket in 2 mm CRCA with four Ø10 mm holes and a 4 mm skeleton web. Pitch becomes 304 × 204 mm. Across a 1,250 mm sheet you fit four columns at 1,216 mm, leaving 17 mm of grip at the edge. Down 2,500 mm you fit twelve rows at 2,448 mm. That is 48 parts, using 48 × 60,000 mm² = 2.88 m² of the 3.125 m² sheet, or 92.2%.

Now draw the same nest the way it often arrives: 50 mm clear of every edge and a 4 mm web. Usable area becomes 1,150 × 2,400 mm. Three columns fit at 912 mm where four no longer do, and eleven rows at 2,244 mm. That is 33 parts, 1.98 m², 63.4% yield.

A 330-part release needs 7 sheets on the tight nest (336 parts) and 10 sheets on the loose one (330 parts). At 49.1 kg per sheet, that is 344 kg against 491 kg, a difference of 147 kg of steel for an identical order. Per part, the material footprint moves from 0.065 m² to 0.095 m², and from 1.02 kg to 1.49 kg.

The beam time barely moves, because the cut length is the same and the pitch only changes the rapid travel between parts. Any rupee saved by cutting 10% faster is small next to a 31% material difference. That is the decision rule to carry into a quotation review: on sheet from 1 mm to 3 mm, ask for the yield percentage before you ask for the cutting rate.

Skeleton, tip-up and the parts that fall out

A nest is only as good as the sheet that leaves the bed. Keep the skeleton a single connected piece from the first pierce to the last cut, and cut the contours that separate the skeleton last.

Small parts need a micro-joint, a tab of 0.3–0.8 mm left uncut, so they travel with the skeleton instead of dropping through. The tab has to be placed where the deburr operator can reach it and where it will not sit on a visible face. A tab that is too strong turns a laser job into a chisel job.

Slugs from apertures and windows fall through the bed, which is fine unless they land on the slats under a later contour. Sequence apertures before the contours that pass beneath them, or leave the slug attached and knock it out at deburring.

Long, narrow parts behave differently again. A 2,400 mm × 40 mm stiffener released from a nest curls as the internal stress of the coil unwinds, and it will not sit flat on a bend gauge. Set long parts to run along the rolling direction, cut them after their neighbours have been freed, and expect to check straightness on the first article rather than assume it.

Remnant control is the last piece. A 1,250 × 2,500 sheet on a 48-part nest leaves a margin strip; keep a library of repeat filler parts in the same material and thickness so the strip is used instead of scrapped, and record on the quotation which part carried the remnant. The cost of a remnant is only real if nobody uses it.

Where the 12 kW bed changes the nest

Large-format nesting is a different problem from small-part nesting, because the bed stops being the constraint. The 12 kW fibre laser at Ganesh runs a 40 ft × 16 ft bed, 12,192 × 4,877 mm, so a 2,400 mm canopy panel or a 3,000 mm coach section and the brackets that fit it can share one program. Two identical long parts side by side also balance the heat across the sheet better than one part alone, which helps flatness on thin panels.

The same shop runs 6 kW and 3 kW support machines for smaller nests, and the 200 T press brake with a 4,450 mm bed on the forming side, so a panel cut across the full bed can still be bent in one pass. The laser cutting capability page lists the materials we cut — mild steel, CRCA, stainless, aluminium, brass and copper — up to 20 mm plate.

Nesting for a customer who supplies their own sheet works differently again. The sheet count is fixed by the customer's purchase order, so yield shows up as parts per sheet rather than steel bought, and the remnant belongs to the customer's account. State it on the drawing pack and the reconciliation stops being a conversation at month end.

Thickness moves the arithmetic in a different direction, and buyers often miss it. A 6 mm part needs a web of about 3 mm plus roughly 0.4 mm of kerf each side, so the pitch grows to about 307 × 207 mm. On a 1,250 × 2,500 sheet the count still holds at four columns and twelve rows, so 48 parts and roughly the same yield percentage. What changes is the mass: a 6 mm sheet weighs 47.1 kg/m², so the sheet is 147 kg and each part carries 3.07 kg of steel against 1.02 kg in 2 mm. The yield held and the steel per part tripled, which is why a thickness change on a drawing is a price change even when the outline is untouched.

Reading a sheet metal nesting plan before you approve a price

Ask for three numbers and the quotation becomes checkable. Parts per sheet, sheet size, and the yield percentage. If a supplier cannot state them, the material line is a guess.

Then check the pitch against the part envelope. A 300 × 200 part on a 304 × 204 pitch is a 4 mm web and a tight nest, and it fits four columns by twelve rows. The same part on a 310 × 210 pitch is a 10 mm web, and it fits four columns by eleven rows, so 44 parts instead of 48: about 8% more sheet per part for a nest that is easier to cut and holds flatness better. Neither is wrong, and the second should be priced as the choice it is rather than presented as the only option.

Finally, ask what happens to the remnant. A nest that leaves a 250 mm strip and scraps it has thrown away 10% of the sheet, and a supplier who retains it for the next release of the same part is giving that value back. Put the answer in the purchase order, because it is the one part of the nest that survives the job.

What to put on the DXF before nesting starts

• Material, grade and thickness, plus the mill certificate requirement if the part is structural.
• Grain direction, or a note that it does not matter, so long parts can be rotated.
• Bend lines on their own layer. A nest that ignores a bend line puts a tab where the press brake needs to sit.
• The cosmetic face, and whether slat marks on the reverse are acceptable.
• The edge condition: whether ISO 9013 class 2 or a deburred edge is required on the visible contour only.
• Quantities and the release pattern, because five releases of 66 parts nest differently from one release of 330.
• Whether remnant may be retained and reused on a future release of the same part.

The laser cutting cost estimator takes sheet size, part envelope and thickness and returns the material share, which is a faster way to test a quote than rebuilding the nest by hand. For the thickness effect on price beyond yield, how material thickness changes laser cutting price works through the same washer part from 1 mm to 12 mm.

When nesting is the wrong lever

Nesting pays where the part is large enough to leave a web worth arguing about. A 20 × 15 mm washer yields badly however it is arranged, and a 30-part prototype order cannot amortise a nest study at all.

At the other end, a stable part made in six figures a year should not be nested at all. A press fed from coil uses the strip continuously and beats any flat-sheet nest, and at that volume the tooling is the cheaper decision. The crossover is worked in stamping versus laser cutting by annual quantity, and the 12 kW fibre laser piece covers what the extra power buys on thickness rather than on layout.

We do not claim a certified cutting tolerance tighter than ±0.5 mm as standard, and we do not run a dedicated coil blanking line for a single customer part. Where a project needs either, say so at enquiry stage and the route is decided before the quotation is written rather than after.

The laser cutting and fabrication hub collects the rest of these guides, including laser cutting tolerances for OEM parts for the callouts that survive the nest.