A customer sends you 180 designs for a festival run. You nest them tight and the packer reports: total packed area 1.84 m². Your roll is 60 cm wide. Your press tray is 60 × 100 cm. That means every sheet you can physically print and press is capped at 60 × 100 = 0.6 m². You need to split 1.84 m² across four sheets. Or five. Or six. And the difference between four and six is about 25 USD of film on a single job.
This post is about the split decision. It is one of the highest-stakes moments in gang-sheet production and most shops handle it with a shrug.
The constraint chain
Every multi-sheet decision is made inside a chain of physical limits that do not flex. In order of how often they bite:
- Roll width. 30, 45, 60, 120 cm are the common DTF widths. On non-DTF substrates the options are different but the idea is the same — you cannot print wider than the printhead carriage reaches.
- Press tray size. This is the sneakier one. A 60 × 100 cm roll can still hit a shop that only has a 40 × 50 cm A-frame press. The transfer has to land inside the press tray. If it does not, it prints fine and then fails to transfer. Check the press size before you plan the split, not after.
- Shipping carton size. Long transfers get folded. Folded transfers crease. Creased transfers print wrong. If the customer is picking up in person, not an issue; if shipping, factor the carton dimension into the max sheet length.
- Cure conveyor length. If the shop runs a conveyor cure oven rather than an A-frame, the effective sheet length is bounded by the oven throat. Uncommon in small shops, dominant in volume production.
- Customer preference. Rarely binding but worth asking — some customers prefer one big sheet per order for handling, some prefer small sheets per design for reorder traceability.
These constraints compose. The binding one is whichever returns the smallest allowed sheet area. Everything downstream works from that number.
The three split strategies
Given a total packed area A and a per-sheet cap C, you need at least ⌈A / C⌉ sheets. That is the theoretical floor. The strategy question is which items go on which sheet — and it drives how close you get to that floor.
Strategy 1: Fill-then-spill
Fill the first sheet as tight as possible. When the next item will not fit, open a new sheet and continue. Repeat until all items are placed.
- Best case: close to theoretical minimum sheets.
- Worst case: the last sheet has one or two pieces and a lot of blank film. You pay for the whole sheet even if 80 % is empty.
- Right for: small mixed orders, low item count, low visual uniformity (the customer will not notice piece-to-sheet layout).
Strategy 2: Balanced split
Divide all items into N piles of roughly equal area where N = ⌈A / C⌉, then pack each pile onto a sheet. Every sheet is similarly full.
- Best case: consistent sheet-to-sheet density, no wasteful tail sheet.
- Worst case: if items have very different sizes, the packer cannot hit the density of Strategy 1 on the tight sheets.
- Right for: large orders, items of similar size, customers who care about the visual of the gang sheet itself.
Strategy 3: Group-by-kind
Put all items of the same design on the same sheet (or adjacent sheets if the quantity exceeds one sheet). This ignores density optimisation for a logistical win — it makes reorders trivial and it makes partial fulfilment (say, 80 % of the order shipped today, the remainder tomorrow) straightforward.
- Best case: cleanest post-print workflow, easiest for the operator cutting and bagging.
- Worst case: lowest utilisation of any strategy; you pay in film for the shipping/reorder benefit.
- Right for: wholesale orders, recurring designs, customers who pay for the handling benefit.
The 15 % rule
On a typical mixed order of 50+ items with modest size variation, the three strategies end up roughly:
- Fill-then-spill: 90–94 % sheet utilisation, one tail sheet at 50–70 %.
- Balanced split: 82–88 % sheet utilisation, consistent.
- Group-by-kind: 60–75 % sheet utilisation, very consistent.
That is roughly a 15 % spread between the tightest and the easiest-to-handle strategies. On a 2 m² order at 25 USD/m² film, that is 7.50 USD per job. On 20 jobs a week that is 150 USD a week, 7 800 USD a year.
Whether it is worth that gap is a real operational question — if group-by-kind cuts cutting time by 15 minutes per sheet, the labour savings can outweigh the film waste. Run the numbers on your own shop before defaulting to either end.
Where the split lines actually go
If you decide to split by area rather than by kind, there is one more trap: the split line should not cross artwork. Even millimetre-accurate cutters leave a 0.3 mm kerf. If a split happens through the middle of a design, that design will ship with a millimetre of the neighbouring piece still attached, or conversely with a millimetre trimmed off its own edge.
The split lines need to land in the gaps between pieces. A decent packer places items with at least a 3–5 mm gutter. The split planner should nudge every split line to the nearest gutter, not to the mathematically optimal Y coordinate. This is mechanical — a planner that ignores it produces beautiful utilisation numbers and ugly prints.
What NestSheet does at the split
NestSheet asks for the split strategy up front (fill-then-spill, balanced, or group-by-kind), then packs each sheet and places split lines only on gutter rows that are wide enough for the cutter’s kerf. Per-sheet filenames encode the Y-range and the part index so operators never have to guess which sheet is which, and a manifest.json inside the zip records the order-to-sheet mapping for reorder traceability.
Nothing about this is exotic — any good gang-sheet tool should do this. The point is that the split decision is not a side-effect of the packer. It is a deliberate product choice with real money on the line. Pick the strategy on purpose, not by accident.
