Vacuum cast polyurethane gives outstanding cosmetic finish.
Plastic production part that looks metallic!!
Vacuum casting is ideal for producing small quantities of parts, especially if aesthetics are important.
The master part, typically produced by Stereolithography (SLA) or CNC machining, is dressed and textured as required before establishing parting planes, feeds etc. The master is then mounted within a frame and liquid silicone cast around it.
After curing, the master is cut out to leave a cavity into which a variety of polyurethanes can be cast under vacuum.
The silicone has sufficient flexibility that undercuts can be released by flexing the tool, although deep draws may require additional tooling splits.
Tool life varies with resin cast, but is typically around 20 parts, by which time the tool surface has started to harden and the tool flexibility deteriorates. Using multiple masters and producing multi-cavity tools can produce greater quantities, although cavity life will remain around 20 parts.
The process is relatively labour intensive and typically requires between 2 and 5 days to produce first castings. This is in addition to the time required to manufacture and dress the master part. Timescales are dependent upon part size as this affects material curing times.
In assessing whether vacuum casting is a viable option, it may be worth also considering RIM or Injection Moulding. See our article 'Injection Moulding or Vacuum Casting, which one should I use?' for useful comparisons.
Alternatively, if quantities are low it may prove faster and more cost effective to make multiple Selective Laser Sintered (SLS) parts. These alternatives are dependent upon part size, complexity and time available.
"This batch really did have the 'wow factor', they are absolutely perfect!"
Tim Collings, Troika Systems Ltd