Loading page
Should my part be die cast or injection molded?
Choose injection molding for most housings and covers: plastic parts are lighter, come out finished in color, and mold in 15–60 second cycles at ±0.005 in (±0.13 mm). Choose die casting when the part needs metal: stiffness, strength under load above about 300 °F (150 °C), EMI shielding, heat sinking, or a metal look and weight. Both need hard tooling and a few thousand parts to pay back.
Which is cheaper at your quantity?
The same housing, each process in a suitable material (A380 and ABS).
| Quantity | Die casting | Injection molding |
|---|---|---|
| 10 | $2,257 | $1,047 |
| 50 | $451 | $209 |
| 100 | $227 | $105 |
| 500 | $47.20 | $21.40 |
| 1,000 | $24.80 | $11.00 |
| 5,000 | $6.81 | $4.10 |
| 10,000 | $4.57 | $2.36 |
| 50,000 | $2.35 | $1.06 |
| 100,000 | $1.98 | $0.89 |
Where each pays off
Zinc and aluminum die casting
1101001k10k100k1M+
- Tooling
- 8–14 weeks
- First article
- 1–3 weeks after die tryout
- Production
- 3–6 weeks per release
±0.002–0.010 in (±0.05–0.25 mm) on the first inch, plus about ±0.001 in per added inch (NADCA precision to standard)
Plastic injection molding
1101001k10k100k1M+
- Tooling
- 3–14 weeks
- First article
- 1–2 weeks after tool completion
- Production
- 2–4 weeks per release
±0.005 in (±0.13 mm); ±0.002 in (±0.05 mm) on small critical features
Which should you pick?
Pick Die casting when
- Stiffness or strength must exceed glass-filled nylon
- The part carries load above about 300 °F (150 °C)
- It needs EMI shielding, grounding or heat sinking
- It needs a metal look and weight, as in plated zinc hardware
Pick Injection molding when
- Weight and piece price matter most
- Color and texture should be molded in with no finishing
- The design uses snap fits, living hinges or needs electrical insulation
- Glass-filled nylon meets the load
Key differences
| Die casting | Injection molding | |
|---|---|---|
| Tooling cost | $10,000–$100,000+ | $3,000–$15,000 aluminum; $10,000–$40,000 single-cavity P20 steel |
| Tool life | Aluminum dies 100,000–150,000 shots; zinc dies 1,000,000+ | Aluminum 10,000–100,000; P20 250,000–500,000; hardened H13 1,000,000+ |
| Cycle time | Zinc 5–30 s; aluminum 30–120 s | 15–60 s |
| Minimum wall | Zinc 0.020–0.040 in (0.5–1.0 mm); aluminum 0.040–0.080 in (1.0–2.0 mm) | About 0.020 in (0.5 mm) over short flows; 0.040–0.150 in (1.0–3.8 mm) nominal |
| Surface as produced | Ra 32–125 µin (0.8–3.2 µm); usually coated | SPI A-1 mirror to textured, in molded color |
| Secondary machining | Common on bores, threads and sealing faces | Rare; features are molded in |
| Tooling lead time | 8–14 weeks | 3–6 weeks aluminum; 8–14 weeks hardened steel |
Questions
Can a plastic part replace a die casting?
Often, for brackets, housings and covers under moderate load. 30% glass-filled nylon is about half the density of aluminum and needs no finishing. Metal stays the better call above about 300 °F (150 °C) under load, for tight long-term tolerances, or for high sustained loads.
Which is cheaper per part, die casting or injection molding?
Usually injection molding, because parts are lighter, cycle fast and come out finished. Die casting closes the gap when the plastic version would need metal inserts, shielding coatings or thick sections to carry the load.
Which holds tighter tolerances?
They are similar on small features. Injection molding holds about ±0.005 in (±0.13 mm); die casting holds ±0.002–0.010 in (±0.05–0.25 mm) on the first inch plus about ±0.001 in per added inch. Critical die cast bores are usually machined.
Try both on your part.
The builder prices the same geometry in every suitable process and material, with DFM for each.