Vacuum casting of polyurethane resins can offer many significant advantages over conventional injection moulding. In particular, Silicone rubber or resin tooling can mean production representative parts being available in as little as 2-3 working days from the approval of a master model.
The extensive range of polyurethane resins available enables us to find a good match with the production intent material, including clear, tinted, ABS, Nylon, PP, PC, and various filled plastics. Properties such as high heat resistance (to over 200 deg C) and flame retardant (UL4 V0 rated) can also be accommodated.
There is also a wide array of polyurethane elastomers to choose from, available from 10 to 95 shore A hardness. Virtually all the resins can be coloured to suite.
Because of the low tooling cost involved, vacuum casting can be the ideal solution for low volume production runs.
The vacuum casting process utilizes a vacuum chamber in which polyurethane resin is mixed with a catalyst and then gravity fed into a mould, thereby reducing the risk of air bubbles in the cast part.
The mould can be made in several different ways, although the most common is to use an SLA master model that has been finished to a required standard and then suspended in a container. Feed and vent paths are added at this point before the container is filled with silicone rubber. When cured, the silicone rubber is cut along pre-determined split lines to produce the tool. Such moulds can normally yield around 25-30 parts per cavity, depending on complexity hardness of the polyurethane being cast. For a longer tool life the mould can be made from cast resin or machined from either modelboard or Aluminium.
Because of the low tooling cost relative to injection moulding, vacuum casting can be the ideal solution for low volume production runs.