Plastic Vacuum Casting
Rapid Prototyping is still a relatively new technology for the fast production of single plastic components that are functional and close or identical to parts made in series, within a few hours.
One branch of this new technology is vacuum casting. A silicone mould is made based on a master model, which has been built with one of the new generative technologies or in a conventional way. Then the silicone mould is filled with a two-part polyurethane resin under vacuum.
50 plastic prototypes can easily be made without complicated and expensive steel moulds. The parts cannot be distinguished from conventionally made serial plastic parts. The check of “fit, form and function” can be done very quickly.
Plastic Vacuum Casting Specifications
MK Technology produces vacuum chambers in different versions and sizes. They have the following advantages.
- Solid construction, steel wall thickness up to 20 mm, door thickness 40 mm
- Reusable cups and funnels
- Electronic differential pressure system
- Precise pre-selection of pressure by go-to function
- Easy program memory
- Time saving by automatic silicone de-gassing
- Perfect visibility through large glass doors and transparent cups
- Chamber and components: Made in Germany
Two ovens are necessary for vacuum casting. The first oven, which is permanently in operation, is for storing the resins, especially opened units, at a temperature of 35°C. This slight tempering prevents the resin from crystallising, this is especially important for isozynath-components.
A second oven is necessary, because a constant temperature of 70°C is required. The silicone moulds are pre-tempered at this temperature to enable perfect casting results. After the cast the silicone mould is put back into the oven, to temper the plastic part for reaching the optimal final strength.
For tempering the resins a standard oven is sufficient. The oven for tempering the mould should be equipped with ventilation to guarantee an optimal heat distribution.
In principle, the size of the oven should fit the size of the chamber. A system 2 XL with a maximum mould length of 2 meters requires an oven for parts up to two meters, otherwise large parts cannot be tempered. Depending on the resin used, this can lead to important strength problems and brittleness.
In order to avoid using a large and cost intensive oven for small moulds, it sometimes makes sense to purchase a third smaller oven for this purpose.
Application of the accessories can increase the practical value of a vacuum chamber. For example, the heating cup allows the production of wax models for the metal investment casting.
If the user is not sure if the accessories are needed or not, they should at least order the electrical preparation. It is not expensive and allows for an easy and fast refitting.