What is the difference between vacuum casting and injection molding?

Vacuum casting and injection molding are both manufacturing processes for producing parts from plastics. The main differences between the two are:

1. Cost of Tooling - Injection molding requires expensive molds to be created before parts can be produced, whereas vacuum casting uses much less expensive silicone molds.

2. Volumes of Production - Injection molding is typically used for large volume production runs while vacuum casting is more suited for low to medium volume runs.

3. Time - Injection molding typically takes weeks to manufacture the molds, while vacuum casting molds can be created in a few days.

4. Complexity - Vacuum casting is better suited to produce parts with complex geometries and undercuts, while injection molding is more suited for geometrically simpler parts.

5. Materials - Vacuum casting is often used with softer plastic like polyurethanes, silicones, and rubbers. Injection molding works with many more material types, including harder, high-temperature materials like ABS, polycarbonate, and Nylon.

6. Quality - Injection molding typically produces parts with a better surface finish and tighter tolerances than vacuum casting.

Overall, Injection molding is better suited for large-volume, higher-cost production runs, while vacuum casting is better suited for lower volume runs of less complex, softer parts with a lower cost per part.