Vacuum casting
How vacuum casting works
The manufacturing process in vacuum casting can be divided into 3 steps.
1) Making the master model: To create the silicone mold, you first need a master model. If the product already exists and you simply want to reproduce it, you can use the existing component. In most cases, you produce a newly developed part that does not yet exist. In this case, the component you want to cast must first be 3D printed. As a rule, the stereolithography process is used for this. This is ideal due to its high dimensional accuracy and easy-to-machine surface. Once the component has been printed, the surface is processed. This means that the construction steps are ground and, if desired, the surface is polished. To achieve a particularly elegant surface, the master model is also painted.
2) Creating the silicone mold: As soon as the master model is ready and visually corresponds to the specifications, the model is fixed in a frame. Liquid silicone, which has previously been mixed with a hardener, is then poured around the model. The silicone then hardens at approx. 40°C for several hours. When fully cured, the silicone is firm but flexible. After you have separated the frame from the silicone mold, you can split the silicone mold into two halves. This is done by cutting the mold with a sharp blade. Where to divide the mold, i.e. the parting plane, is determined before the mold is created. This is necessary because the master model has to be processed to this end. Once you have divided the silicone mold into two halves, you can remove the master model and obtain a negative mold into which you can cast.
3) Casting: This step is the part in which the components are ultimately produced. The right polyurethane is selected depending on the material properties you want to achieve. Vacuum casting offers an extremely large selection and can simulate almost any series material such as PP, POM, PA, ABS or TPU. Inserts such as standard parts or electronic components can also be encapsulated.
Advantages of vacuum casting
Vacuum casting offers a whole range of advantages, both technically and economically. The investment costs are many times lower compared to injection molding, with almost identical quality. Vacuum casting also stands out from additive manufacturing processes in a number of ways.
Fast and inexpensive mold production: The production of the silicone mold costs only a fraction of metal mold production. And it is ready within a few days.
Precision: With the necessary experience, components can be produced with tolerances in the µm range.
Optics: Any surface, color or transparency can be easily achieved with vacuum casting. At the same time, there is no need to compromise on stability.
Large components: Even oversized components up to 2,000 x 1,000 x 1,000mm can be produced in one piece.
Inserts: Standard parts such as bearing bushes or electronic components can be inserted into the silicone molds and encapsulated. We have the same options here as in injection molding. You reach your limits very quickly here, especially in 3D printing.
Variety of materials: There is an enormous variety of materials in vacuum casting. The materials here are based on the usual materials used in injection molding. You can choose freely between hard and soft, flexible and soft or transparent and colored. Any material property can be achieved here.
Multi-component: 2K or 3K components are easy to produce in vacuum casting. Either hard/soft, soft/soft or hard/hard combinations are possible.
Vacuum casting: The applications
Vacuum casting is the perfect cross-industry alternative to injection molding for the production of small batches. Vacuum casting is significantly more economical, especially for quantities of up to 2,000 units, where the tool costs in injection molding are proportionally very high.
Materials:
Polyurethanes or epoxy resins are processed in vacuum casting. Depending on their chemical composition, these can take on completely different properties and thus simulate series materials. Material properties, such as those of PA, POM, ABS, TPU, PP, PC and many more, can be matched almost exactly. This allows either realistic prototypes to be produced for tests and inspections or small series to be manufactured.
Post-processing in vacuum casting:
- Varnishing
- Vaporizing
- Coating
- Glass bead blasting
- Assembly
