Process selection
Injection Molding vs Die Casting
Both force molten material into a steel tool under pressure, but injection molding runs thermoplastics and die casting runs molten metal. The choice comes down to material properties, part strength, and volume economics.
| Injection Molding | Die Casting | |
|---|---|---|
| Material | Thermoplastics and filled resins | Aluminum, zinc, magnesium alloys |
| Tooling cost | 10,000 to 100,000 USD | 15,000 to 150,000 USD |
| Cycle time | 15 to 60 seconds | 20 to 90 seconds |
| Part strength | Lower, polymer dependent | High, metal structural parts |
| Wall thickness | 0.5 to 4 mm typical | 1 to 6 mm typical |
| Break-even volume | 1,000 to 10,000+ parts | 5,000 to 50,000+ parts |
| Surface finish | Excellent as-molded | Good, often machined or coated |
Choose Injection Molding when
- The part is plastic or does not need metal strength
- You need light weight and low per-part cost at volume
- Complex geometry with living hinges or snap fits
Choose Die Casting when
- The part must carry structural load or dissipate heat
- You need metal durability, EMI shielding, or fire resistance
- Tight dimensional stability across temperature
The verdict
Pick injection molding for plastic parts where weight and unit cost matter, and die casting when the part must be metal for strength, heat, or shielding. Die casting tooling and machine costs run higher, so it needs volume to amortize.
Cost comparison
On cost, plastic resin typically runs 1 to 4 USD per kilogram against 2 to 5 USD for aluminum ingot, and molding machines cost less per hour than die cast cells of similar tonnage. A small plastic housing might cost 0.40 USD molded versus 1.50 USD die cast. Die casting also adds trim dies and often machining, so its unit cost stays higher until secondary operations replace separate metal parts.
Common questions
Is die casting cheaper than injection molding?
Per part, die casting usually costs more because metal, higher melt temperatures, and machine tonnage cost more than plastic. Injection molding is typically cheaper per unit when the part can be plastic.
Which is stronger, die casting or injection molding?
Die cast metal parts are far stronger and more heat resistant than standard injection molded plastics. Glass-filled resins narrow the gap but rarely match cast aluminum or zinc.