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Polyurethane vacuum casting delivers rapid turnaround prototypes efficiently. The process uses a solid master to cast soft silicone rubber molds.
These molds produce up to 20 high-quality prototype parts. The parts have excellent surface finishes and require minimal investment in raw materials.
Vacuum casting also supports multi-material overmolding. This is an additional advantage that many people overlook.
Our company is one of the few in the industry offering overmolding for vacuum-cast parts. Overmolding combines two or more resins step by step.
This process creates a uniform finished part. Below is an explanation of how overmolding works and why it suits product development.
Advantages of Overmolding
Overmolding creates parts with a wide range of textures, hardnesses, and mechanical properties. Manufacturers commonly use this technique to make plastic injection-molded parts.
For example, they use it to add soft grips to power tool handles. Few people realize that polyurethane vacuum casting can achieve similar results. Proper methods make this possible.
Detailed Process Flow for Overmolding
1. Modeling
You need at least two slightly different models for overmolding.
The first model shows the complete appearance of the finished part.
The second model removes the details in the area that will be overmolded.
Modern CAD software simplifies this process. You can erase the overmolding area directly in the software. Then, send the modified model to a 3D printer to create two master models.
2. Creating Silicone Molds
Use the two models to create two separate silicone molds.
The first set of molds produces the base parts. These molds use hard resin to provide structural strength.
The second set of molds is slightly larger. It holds the base part and creates space for the overmolded material.
After casting, remove the base part from the first mold. Place the base part in the second mold. The second mold leaves a small gap between the base part and the cavity wall. This gap defines the overmolding area.
3. Secondary Molding
Design a feed line that connects to the overmolding area.
Inject a softer elastomeric resin into the gap to fill the feed line.
Place the mold in a vacuum chamber. Heat it until the resin fully cures.
This process creates a permanent bond between the two materials. Theoretically, you can use multiple secondary molding resins. In practice, limit the process to two resins. This simplifies the operation and extends the silicone mold’s lifespan.
Applications and Advantages
Overmolding works well for parts requiring different properties. Examples include:
Electronics housings: Use hard material for protection and soft material for comfort.
Industrial equipment parts: Combine durable shells with soft-touch surfaces for a better user experience.
We provide overmolding services that address diverse design needs. Our solutions ensure fast and effective prototyping. If vacuum casting fits your project, upload your CAD drawings. We will provide a free professional quote!