RTM injects resin into a closed mould containing a dry fibre preform, so both faces of the part take the mould surface. Dimensions are controlled by the rigid tool rather than by hand, which makes RTM the process for parts needing a finished surface on both sides and tight dimensional repeatability.
Closed moulding with two finished faces
Dimensional tolerance controlled by the tool, not the operator
Class-A gel coat on the visible surface
Inserts and cores moulded in place
Higher fibre content than hand lay-up
200–5,000 parts per mould
| Glass fibre preforms |
| Carbon fibre preforms |
| Polyester and vinyl ester |
| Epoxy for structural parts |
| Core materials for sandwich |
| Gel coat and in-mould coating |
| Specification | Details |
|---|---|
| Quantity | 200–5,000 parts |
| Mould lead time | 20–35 days |
| Thickness | 1.5–15 mm |
| Tolerance | ±0.5 mm on matched features |
| Tool life | 1,000–10,000 parts |
| Cycle time | 20–60 min depending on size |
Coloured gel coat both faces
In-mould texture and grain
Paint-ready surfaces
Machined and bonded inserts
RTM gives better dimensional control and a finished surface on both sides because the mould is matched and rigid. Infusion is cheaper at low volume and better for very large single-skin parts.
A matched pair of moulds, usually steel or aluminium framed composites so they resist injection pressure and heat. Tooling cost is higher than hand lay-up but the tool lasts far longer.
Yes, and RTM is used for structural automotive and rail components. Fibre architecture is designed to the load path and validated by coupon and part testing.
Glass & carbon fiber parts for automotive, motorsport, marine.
Hand lay-up and spray-up FRP for one-off panels, prototypes and small series. Low tooling cost, glass or carbon fibre, gel-coated finishes.
Vacuum infusion and RTM Light for consistent, low-void composite parts. Better fibre ratios and repeatability than hand lay-up, for 50-1,000 parts.
Sheet moulding compound compression moulding for high-volume composite parts. Class-A finish, fast cycles and repeatable dimensions above 1,000 parts.
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