Short answer. A pultrusion die sets the shape, surface and cure of every metre you make. Good dies have a tapered entry, controlled heating zones, hard polished (often chrome-plated) working surfaces and allowances for resin shrinkage; most scrap blamed on the machine is really a die problem.
| Part of the die | Purpose | Design points |
|---|---|---|
| Entry (taper) | Guides the wet fibre in and squeezes out excess resin | Smooth taper, enough length to avoid fibre piling up; resin collects here |
| Heating zones | Gel and cure the resin as the package moves | Several independently controlled zones with thermocouples; avoid overheating the entry |
| Forming section | Final shape and surface | Dimensions allow for resin shrinkage; accurate, smooth bore |
| Working surface | Surface finish of the profile; wear resistance | Hardened tool steel, polished and usually hard-chrome plated; reconditioned when worn |
| Core pins (hollow profiles) | Form the inside of tubes | Support and alignment; extra heat management |
| Mounting and cooling | Hold the die and manage heat | Alignment to the puller line; correct cooling after the die |
How a die is made
- Review the profile drawing: wall thickness, radii, draft, tolerances.
- Design the die and fibre layout; decide the heating zones and the allowance for shrinkage.
- Machine the die (milling, EDM, grinding), then polish the bore to a mirror-like finish.
- Heat-treat and plate the working surface.
- Trial run and adjust: first samples decide the final settings.
What to ask a die maker
- How the die handles your resin and fibre system and your line speed;
- what finish and plating are used and how worn dies are reconditioned;
- how many trial profiles are included before approval.
How to choose a supplier: choosing a pultrusion mould manufacturer. Defects and how they link to the die: pultrusion defects and mould problems. The overall process: pultrusion process step by step. See our pultrusion moulds.
Die life and maintenance
- A polished chrome surface wears: schedule inspection and re-polish or re-plating.
- Clean the entry and bore at the intervals set from run history; avoid abrasive tools on the working surface.
- Store dies with protective coating and in a dry place.
- Log runs (metres, resin batch, temperatures) so wear can be linked to production.
Send us your requirement
Guangdong Haikuo Composite Materials Co., Ltd. (Huizhou, Guangdong) designs pultrusion moulds in-house and produces custom FRP profiles. Send a drawing, a sample or just the application and the environment, and we will tell you what is feasible.
Email: helena@frphk.cn | Phone: +86 189 5198 8522