Vacuum casting-process

Posted by roger |

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Vacuum Casting, also known as Resin Casting, is a widely used process for creating low volume 3D models or prototypes. This process is especially suitable for creating small to medium-sized parts with high-quality finishes. Typically, with one soft tool, 20-25 duplicates can be made out of polyurethane material. The Vacuum Casting process consists of five main steps. First, an accurate and highly finished master model is created using various Rapid Prototyping (RP) techniques such as Stereo Lithography (SLA), Fused Deposition Modeling (FDM), Selective Laser Sintering (SLS), Computer Numerical Control (CNC), or an existing part. In the second step, the mother model is placed in a mold box, and liquid silicone rubber is poured over the master. Once the silicone is cured, the mold is cut along the established split line, and the master model is removed, leaving an accurately formed cavity. The third step involves preparing the mold for casting by applying a release agent to the surface. In the fourth step, the mold cavity is used to cast a large variety of polyurethane or epoxy materials, allowing for fast production of high-quality parts in a short lead time.

The costs of Vacuum casting:

The cost of creating silicone molds is much lower than that of steel molds, and the manufacturing of these molds can be done in a short lead time. A lead time of 4-10 days is possible, depending on the complexity and the method used to create the master model. There is a large variety of urethane materials available, and their properties are very close to injection molded materials, ranging from soft rubber grades to hard plastics. Some polyurethane can be colored directly, and it is also possible to sandblast or paint the finished parts. Because of the flexibility of the silicone molds, undercuts in the product can be made without sliders or cores. Inserts can also be placed in the molds, and even over-molding two or more components is possible. However, the tool life time of the silicone mold is limited, and one cavity can only make 20-25 parts before a new mold has to be created. Vacuum Cast parts are not identical to injection molded parts because the conditions and method of manufacture are different. Very thin wall sections are not recommended as there are chances of cracking or warping. Overall, Vacuum Casting is a cost-effective and efficient way to produce high-quality parts in low volumes. Its flexibility in design and material options make it a popular choice in the prototyping industry.

Recommendations:

The Minimum wall thicknesses is recommended not to be smaller than 1 mm. Generally 20 pieces can be made from single mould so multiple of 20 can give you better pricing to cover up the silicon mould cost. E.G. Qty 20 or 40 has better pricing per piece than 30 or 50 pcs.