“Should this part be die cast or injection molded?” It is one of the first questions in a new product programme, and the answer affects tooling cost, unit cost, lead time and the design itself.
Start with the material requirement
Die casting is used for metal parts — most commonly aluminum, zinc and magnesium. Injection molding is used for plastics, from commodity resins to engineering polymers. If the part needs metal’s stiffness, thermal conductivity or EMI shielding, die casting is usually the starting point. If it needs electrical insulation, optical clarity or a wide color range, plastic is the natural choice.
Volume and tool life
Both processes use steel tools, but die-casting dies operate at much higher temperatures and pressures. A well-maintained HPDC die might run 100,000 to 1,000,000 shots; an injection mold can exceed a million cycles depending on the resin and steel. For low volumes, a prototype or bridge tool can be more economical than a full production die.
Wall thickness and features
Die casting can produce thin, stiff metal walls, but very thin sections and large flat areas bring porosity and filling risk. Plastic injection molding handles complex ribs, bosses and snap features well, but thick sections can sink or warp. In both cases, the DFM review should challenge the wall thickness before the tool is designed.
Surface finish and secondary operations
Die-cast parts often need machining, trimming, impregnation or coating. Plastic parts can be molded with texture, color and high gloss, reducing secondary operations. The total cost comparison should include finishing, not just the tool and the shot price.
How we help
We build both die-casting dies and injection molds, so our recommendation is based on the part and the programme — not on which tool we prefer to sell. Send the model, the material requirement and the annual volume, and we will compare the two routes with realistic tooling and unit costs.