A production mould is not a shaped block of steel, it is a machine: it opens and closes under high force, injects, cools, ejects and does it again several hundred thousand times without being adjusted. Buying one means buying a capital asset with a maintenance requirement, and the contracts that go wrong are the ones that treated it as a purchase of parts.
What is in the tool
A mould base, cavity and core inserts, a runner system either hot or cold, cooling circuits, ejection, and whatever mechanisms are needed to release undercuts. Standard components make up much of it, which is why toolmakers work from catalogue bases: it is cheaper, faster and easier to maintain than making everything bespoke.
Steel, life and what to specify
Specify the tool against a number of shots rather than a period of time. Aluminium suits hundreds to low thousands. Pre hardened steel covers most mid volume work. Hardened and sometimes coated steel is what abrasive glass filled resins require if the cavity is to hold its dimensions. Under specifying life is the commonest false economy in the whole process.
Cooling is the tool's real performance
Cycle time is dominated by cooling, and cooling is decided by the layout of the water circuits. A tool with well designed cooling can pay back its extra cost in machine time within months. Conformal cooling channels, made by printing the insert rather than drilling it, are the strongest current argument for additive manufacturing in tooling.
Ownership, maintenance and the handover
Agree in writing who owns the tool, where it is stored, who does routine maintenance, who pays for wear items and for damage, and what shot count records you receive. Agree what condition the tool is handed over in if it moves. And expect a requalification if it does move, because a tool on a different machine with different cooling needs its process developing again.
Questions people ask about injection molding tooling
How long should an injection tool last?
As long as it was specified to. Quote it in shots, choose the steel accordingly, and maintain it. A tool run beyond its design life produces flash and dimensional drift.
Who maintains the mould?
Usually the moulder running it, under an agreement that says what is routine and what is chargeable. Ask for maintenance records and a shot counter reading.
Can I move my tool to another moulder?
If you own it and the contract allows. Expect requalification, because a different machine and different cooling change the process window.
What makes a tool expensive?
Cavity count, steel grade and life, the number of moving actions, and the surface finish or texture. Part size matters far less than buyers expect.