Injection Molding Through Our Partner Network

What we machine on this process

Injection molding is the route we recommend when a part’s net shape is complex, weight matters and volume justifies a mould. Molding runs through our vetted partner network, managed under one quality process, while the metal side — inserts, threaded bushes, precision bores — is machined on our own floor in Qidong City, Jiangsu Province, China. The result is one order, one drawing and one delivery, so a plastic housing with a machined metal boss is not two separate purchases. Because the mould and the metal inserts come from the same drawing, the fit between plastic and metal is planned before the mould is cut. If the same geometry reads better in metal, we quote it as a machined part on our CNC machining floor and let the numbers choose.

Materials and finishes

We mold engineering plastics, with the resin chosen in DFM for strength, stiffness, temperature and chemical behaviour — not pre-assigned from a catalogue. Wall thickness, draft and ribbing are designed around that resin before the mould is cut. Where the part carries metal, we machine aluminium 6061, stainless steel or brass inserts on our floor, and mould them in or press them after. Surface texture and colour are agreed at the drawing stage so the finish is part of the same job. For solid metal parts see our materials page.

Size, tolerance and capacity limits

Molding holds part-scale tolerances that we agree per drawing in DFM; it does not match machined metal. That is why critical fits — a bore, a face, a thread — are carried by a machined metal insert rather than by the plastic. Metal features are machined to ±0.01 mm with general dimensions to ISO 2768-m, within our 800 × 500 mm milling envelope, and the floor runs over 100,000 parts per month. Mould size, shot weight and gate count are evaluated per drawing before tooling is cut, and the plastic’s tolerance envelope is set in that same review so there are no surprises after the first shot.

Documents and shipping

Molding, insert machining and finishing are managed as one job from our factory in Qidong City, Jiangsu Province, China. The moulding partner runs to the same drawing and the same document set as our own floor, so the part is one process with one contact and one delivery. Parts ship with a material certificate (MTR) for any machined metal inserts and pre-shipment photos, so you can see the part before it is packed. Send a drawing through the request a quote form and we return the full route in one reply.

Industries we support

Molded parts serve general machinery, automation, instrumentation, consumer hardware and enclosures — anywhere plastic’s weight, insulation or net-shape cost wins. The common pattern is a plastic body with machined metal fittings: a housing with threaded inserts, a cover with a pressed-in bush, a grip with a steel pivot. For metal housings made from sheet, see sheet metal fabrication; for formed metal at volume, see metal stamping. We also mould plastic onto cast or machined metal frames, so a mixed-material assembly is still one purchase.

Design guidelines for cost and manufacturability

Design for even wall thickness first — a thin-to-thick step causes sink and warp. Add draft on faces that pull from the mould, radius inside corners, and keep ribs no thicker than a fraction of the wall they support. A uniform wall also shortens cycle time and cuts sink marks on visible faces, and generous corner radii where ribs meet the wall help the part fill cleanly. Decide early which features the plastic can hold and which need a metal insert; a bore that must stay round to ±0.01 mm belongs in a machined insert, not in the plastic. Gate and ejector marks are placed on hidden or non-critical faces where the design allows. Mould cost is quoted separately and amortised across volume, so the more you make the lower the true cost per part. Send the drawing and we return DFM feedback within 24 hours.