Every startup arriving at a first batch of 20-50 units hits the same question: print all of them in SLS/MJF or go with Vacuum Casting? The answer depends on three variables: quantity, finish and function.
How Vacuum Casting works
Print a high-quality SLA master, cast a silicone mold around it, then inject polyurethane under vacuum. Each mold produces 20-25 identical parts before losing dimensional accuracy.
The crossover cost
Our experience at P3: above 15 identical units, Vacuum Casting beats SLS on cost. Reason: the mold cost amortizes over more units, and per-unit polyurethane cost is significantly lower than nylon powder.
Quality and finish
Vacuum Casting starts from a smooth SLA master, so the finish is excellent – close to traditional injection molding. Paint, in-mold color or transparent material – all possible. SLS gives a grainy finish that needs extra work.
When to choose which
- 1-15 units, strong functionality → SLS/MJF
- 15-50 units, marketing-grade quality → Vacuum Casting
- Over 100 units → consider Injection Molding
- Transparent or flexible materials → Vacuum Casting
Summary
Vacuum Casting is a critical tool in any product engineer’s kit. It bridges prototype to mass production, letting startups reach market with a high-quality beta batch without investing in injection tooling.