Vacuum Casting

Vacuum casting is an indirect soft tooling process, indirect because it requires a master pattern before a mold tooling can be formed, and soft because a typical silicone rubber is usually used for building the mold which can only support castings in small batches ^[1]. In terms of production versatility, vacuum casting is comparable to modern injection molding, but the investment cost is much lower. However, due to the relatively high cycle time (each casting cycle is up to 90 minutes) and limited mold service life (each mold is usually below 50 casting cycles), vacuum casting is rarely used for medium or large series production.

Are you looking for a reliable vacuum casting specialist for your project? Look at Alfa Chemistry! Our skilled and experienced technical experts are committed to providing you with professional vacuum casting services. Our service industries include, but are not limited to, automotive, medical, consumer goods and electronics. If you need, please feel free to contact us.

Advantages of Vacuum Casting

The main advantages of using vacuum casting for manufacturing are as follows.

High precision: Vacuum casting allows the creation of highly fine parts with smooth surfaces.
Shorter delivery times: It takes several weeks to manufacture steel or aluminum molds, while it takes only a few days to manufacture silicone molds.
Lower upfront investment: Vacuum casting is one of the most cost-effective ways to produce high-quality, small-batch plastic parts. Compared with injection molding, vacuum casting requires much lower upfront tooling investment.
Excellent surface finish: The parts produced by vacuum casting have smooth and detailed surface finish, which also makes the process very ideal in the industry where aesthetics are valued.

How Vacuum Casting Works

The working process of vacuum casting is as follows:

• 3D Modeling
• Create a digital 3D model of the desired object using computer-aided design (CAD) software.
• In order to achieve the best results, injection molding principles must be followed.

• Master Pattern Building
• Choose a manufacturing method to create the master pattern.
• Early master patterns were made using CNC or hand tools. However, the currently used processes, such as 3D printing, stereolithography and various other processes have become a faster and more affordable choice.
• If you have a cast model which can be used as the master pattern, you can use it directly.
• Silicone Mold Making
• The master pattern is fitted with cores, inserts and casting gates and suspended inside the casting box. Risers are put on the part to ensure proper air escape during molding.
• Silicone is then poured around the master under vacuum into the casting box, allowing it to fill every detail perfectly.
• The mold was left in the oven and cured at 40 °C for about 8-16 h.
• When the silicone rubber has cured and dried, the box and risers are removed.
• A scalpel is used to carefully split the mold to reveal the negative shape cavity of the part.
• Casting Materials Mixture and Pour
• Select the appropriate casting material based on the desired properties of the final cast parts (e.g., hardness, flexibility, transparency).
• Mix the components of the casting material, adding any colorants or additives if needed.
• The casting material is poured into the mold under a vacuum to avoid any air pockets or voids.
• Seal the mold to prevent leaks.
• Cast Parts Curing and Demolding
• After casting the resin, the mold is placed in a heating chamber to cure.
• After curing, the casting is removed from the mold, and the gate and risers are removed.
• Finish with additional finishing.

Our Vacuum Casting Materials

According to the characteristics of your project, you can choose the following different vacuum casting materials.

Materials	Features
ABS-like polyurethanes	Good impact resistance Well-balanced physical properties
PA-like polyurethanes	Durable and rigid Lightweight
PC-like polyurethanes	Good transparency Good UV resistance
PP-like polyurethanes	High impact resistance Good flexibility
PMMA-like polyurethanes	Good transparency Good UV resistance

If you are interested in our vacuum casting service, please do not hesitate to contact us immediately.

Reference

1. Tang, Y.; et al. Micro-mould fabrication for a micro-gear via vacuum casting. Journal of materials processing technology. 2007, 192: 334-339.