Two mould families, two different jobs
Compression moulding places a preformed blank of compound into a heated cavity and closes the press. Tools are simpler and cheaper to cut, which suits larger parts and moderate tolerances. Injection moulding forces compound into a closed cavity; the tool is more complex, but it holds tighter tolerances and handles multi-material parts and high volumes.
The choice is made from the part, not from preference: wall thickness, undercuts, tolerance, annual volume and whether the part is assembled from more than one material all push the decision one way or the other.
Sample mould and production mould are not the same tool
A sample mould proves the geometry. A production mould is built for the cycle count, with the cavitation, cooling and steel that volume requires. Some projects can move straight to a production tool; most benefit from proving the shape first, because a change made after steel is cut is expensive.
| Stage | Lead time at our plant |
|---|---|
| Sample mould | 5–10 days |
| Production mould | 7–12 days |
| Design sign-off | About 2 days |
| First samples after sign-off | About 3 days |
What stretches a tooling schedule
- Changes after steel is cut. The largest single cause. Freeze the geometry before machining starts.
- Incomplete drawings. Missing wall thickness, draft or a tolerance callout forces a design conversation mid-schedule.
- Trial-shot iterations. A first shot that shows flash, short fill or a dimension out of tolerance needs a correction and a second shot.
- Cavitation. A multi-cavity tool takes longer to cut and longer to balance than a single-cavity tool.
- Surface finish. A textured or polished cavity adds hand work.
- Steel grade and heat treatment. Hardened tooling for a long programme takes additional processing time.
Questions worth asking about the mould
- How many cavities, and why that number for my volume?
- Which steel, and is it hardened?
- What is the expected cycle count before refurbishment?
- Who owns the tool, and where is it stored between runs?
- What does a running change cost, and how is it quoted?
- Is maintenance included, and for how long?
A supplier who answers these without hesitation has run tooling programmes before. One who treats the mould as an unexplained lump sum has not, or does not want the questions.