Injection Molding Plastic Materials

A glass-filled engineering resin is a difficult first tool because it couples two costs at once: high melt temperature and abrasive wear. If the part only needs to prove the geometry, cut the first tool in an unfilled grade that behaves similarly and move to the filled grade once the design is settled. Starting in PA6-GF30 means the gate, the vents and the screw all wear while the design is still changing.

Yes, and the wear is concentrated rather than spread. Glass fibre erodes the gate, the sprue bush, the vent lands and any narrow flow path first, because velocity and impingement are highest there. The cavity walls see much less. That is why a glass-filled tool is often specified with a hardened gate insert in an otherwise pre-hardened block.

A physical target is still the reliable route, because a colour read off a screen or a photograph depends on the display, the light source and the camera. If you cannot send a part, send a Pantone reference plus the resin grade, and accept that the first shot is a trial: we will mould coupons and compare them against the reference before the tool is finished.

The 3D part or a drawing, the annual volume, the service environment (indoor, outdoor, chemical contact, temperature), the appearance requirement and any regulatory constraint. With those we reply with a resin shortlist, the shrinkage allowance we would cut the tool to, and the steel grade the resin implies.

Because shrinkage is a range produced by a specific test plaque, not a constant. Wall thickness, gate location, melt temperature, mould temperature, packing pressure and hold time all move the number, and a supplier may quote flow direction, cross-flow, or an average. The value to design to is the one measured on a part with your geometry, which is why we cut a sample cavity before committing a production tool.