Injection moulding: Injection moulding is a process that makes plastic parts by injecting molten plastic under pressure into a closed metal mould, then cooling and ejecting it.
Injection moulding (molding in the US) melts plastic pellets in a heated barrel, and a screw forces the melt into a mould. The plastic cools, the mould opens, and ejector pins push the part out. A cycle for a small part commonly takes tens of seconds, which is why the process is the standard for plastic parts in thousands to millions.
What it means for the price
The mould is a large one-off cost, from a simple aluminium tool to a hardened steel tool with many cavities. Per part, the cost is material plus machine time per shot, divided by the number of cavities. Tool amortisation spreads the mould over the quantity, which is why the price per part falls steeply as volume grows. Parts need a draft angle and even walls to mould cleanly and quickly.
Example: a €6,000 mould spread over 2,000 parts adds €3 to each; spread over 50,000 parts it adds €0.12. The figures are an example.
Common confusions
Injection moulding is rarely the right choice for 50 parts; vacuum casting or 3D printing usually is. Quotometry gives a budgetary injection moulding estimate today, tool and part price, which the shop always reviews before it is confirmed. Read what drives injection moulding cost or see the injection moulding process page.
Go deeper: Injection moulding cost: tooling, cycle time, resin and the break-even