The number of parts you need shapes almost every decision in injection moulding, from the tool you build to the price you pay per part.
Low Volume Moulding
For prototypes and lower quantities, the goal is to keep tooling cost down. Simpler, single-cavity or aluminium tools reduce the up-front investment, at the expense of a slightly higher cost per part. This is ideal for new products, niche items and modest annual volumes.
High Volume Moulding
For large runs, the priority shifts to driving down the cost per part. Hardened steel tooling, multi-cavity tools (making several parts per cycle) and optimised cycle times spread cost efficiently across huge quantities. The tooling costs more, but each part costs less.
Cavitation Explained
A multi-cavity tool produces several parts in a single moulding cycle, slashing the cost per part at higher volumes. But more cavities mean a more complex, more expensive tool, so cavitation is matched to your quantity.
Which Is Right for You?
It comes down to your annual quantity and how it might grow. We're set up for both low and medium volumes and will advise on the most economical tooling and process for your numbers. See injection moulding costs.
Sources & Further Reading
For independent background on the process, see the British Plastics Federation's guide to injection moulding and the overview on Wikipedia.