How the cost per piece is worked out
Material = (part weight + runner weight × (1 − regrind) ÷ cavities) × resin ₹/kg. The runner is shared by every cavity, and the part of it you grind back and reuse costs nothing but the grinding.
Machine = machine hour rate × cycle ÷ 3600 ÷ cavities. One cycle makes one shot; one shot makes as many pieces as the mould has cavities running. Labour works the same way with the operator's hourly cost.
Rejection is applied to the three above: if 2% of pieces are scrapped, the good ones carry the cost of the bad, so cost ÷ (1 − 2%). Packing is added per piece, overhead as a percentage of the direct cost, and margin as a share of the selling price — so a 15% margin is price = cost ÷ 0.85, not cost × 1.15.
Typical figures on an Indian floor
| Input | Where it usually lands |
|---|---|
| Resin, ₹/kg | PP and HDPE ₹95–120, ABS ₹150–190, PA6 ₹220–280, PC ₹260–340 — check this month's circular |
| Machine hour rate | ₹250–350 for 80–120 T, ₹400–550 for 150–250 T, ₹700–1,000 for 350 T and up |
| Operator | ₹16,000–22,000 a month; often one operator to two presses |
| Rejection | 1–3% on a settled job; 5–10% on a new mould or a wet material |
| Regrind | Runners reused at 30–100% for commodity parts; 0% where the customer forbids it |
Where quotes go wrong
The runner is forgotten. On a small part, a 12 g cold runner across four cavities adds 3 g to a 38 g part: 8% of the material, straight off the margin.
The cycle is the setter's best, not the shift's average. A mould that runs 32 s at 10 a.m. and 36 s by the night shift costs 12% more machine time than quoted. Only the press knows the real number.
Rejection is left out because "we'll fix the mould". Put it in; take it out when the mould is actually fixed.
Margin is added as markup. 15% on cost is 13% of price; on a 500,000-piece order that gap is real money.
Cystems does this sum from the floor's own figures, per job, as it runs: how we read your presses.