Shot: A shot is one injection of molten plastic into a mould in one machine cycle, filling every cavity and the runners that feed them at once.
Each cycle of an injection moulding machine delivers one shot. The shot weight is the parts plus the runners and sprue that feed them; a hot runner mould has little or no runner waste. The machine must be able to inject that much plastic and hold the mould closed against the injection pressure, which decides the size of press the job needs.
What it means for the price
Machine time is paid per shot, so the price per part is the cost of one shot divided by the number of mould cavities. The shot’s cycle time is mostly cooling, set by the thickest wall in the part. Runner material is either reground and reused or scrapped, which adds to material cost.
Example: a 30-second cycle on a press at €45 per hour costs €0.375 per shot. With four cavities, that is about €0.09 per part. The figures are an example.
Common confusions
A “short shot” is a defect in which the mould does not fill completely; it is not a small shot. Shot size is also not the part’s weight when there are runners. Read what drives injection moulding cost.
Go deeper: Injection moulding cost: tooling, cycle time, resin and the break-even