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Rapid Vacuum Casting (Urethane Casting) Service

Vacuum Casting, also known as Urethane Casting or Silicone Molding or Silicone Casting, is a popular method for prototyping. This process is ideal for new product engineering tests, concept proofing, market testing, trial production, pre-production evaluation, and low-volume production. Vacuum casting is favored for its cost-effectiveness, fast lead times, and ability to closely simulate final molded parts or finished products.

Vacuum Casting is an excellent method for producing 10 to 50 high-quality prototypes. Our rapid vacuum casting service offers a versatile range of materials that can simulate ABS, PMMA, Rubber, PP, Nylon, and more. We also provide post-finishing services, including coloring, matte or glossy finishes, plating, painting, and other custom options. This flexibility, combined with our commitment to quality and speed, makes Alpha-Mold a leader in delivering prototypes that meet the highest standards. With our expertise, you can accelerate your product development timeline while ensuring strict quality control.

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How Urethane Casting Works?

Urethane Casting is similar to injection molding as both processes require a mold with a cavity shaped like the final part. The key difference is that urethane casting uses a "soft" silicone mold, while injection molding uses a "hard" metal mold that has been CNC machined. Although silicone molds wear out more quickly, urethane casting is far more cost-efficient for small-batch production runs and prototype plastic parts that still require production-level quality and excellent surface finishes.

The urethane casting process involves three key steps:

1. Creating the Master Pattern:

The master model is typically created through CNC machining or SLA 3D printing. The quality of cast urethane parts largely depends on the precision of the master pattern. For parts requiring tight tolerances, a glossy finish, or optical clarity, CNC machining is the preferred method for creating the master. For parts with more complex shapes and structures, SLA (Stereolithography) may be used to achieve the desired detail.

2. Silicone Mold making:

Liquid silicone is poured over the master model to create a mold. The silicone captures every detail of the master, ensuring the final cast parts are accurate replicas. Once cured, the mold is carefully cut into two halves, and the master pattern is removed, leaving a cavity in the shape of the part.

3. Pouring and Curing:

Liquid urethane or silicone is then poured into the silicone mold. The mold is placed in a chamber to help remove air bubbles in the liquid material—pressurized for opaque parts and vacuum-sealed for clear parts. After curing, the mold is opened, and the newly formed part is removed. This process is repeated until the desired quantity is achieved. The part may undergo additional finishing processes like painting, polishing, or assembly.

You can get production-like results including mechanical traits, wall thickness, colors, and surface finishes with rapid vacuum casting prototyping.

Advantages of Vacuum Casting

Fast Delivery

Alpha-Mold can provide up to 20 parts in 7 days, depending on part specification and volume. This quick turnaround is ideal for prototypes and low-volume production runs.

Low cost for silicone molds

Silicone molds are significantly less expensive than traditional steel or aluminum molds, making vacuum casting a budget-friendly option for low-volume manufacturing without compromising too much on quality.

Superior surface finish to injection molding

The vacuum casting process effectively removes air bubbles, resulting in parts with smooth, detailed surface finishes. This method often surpasses the surface quality of CNC machined or 3D printed parts, making it an excellent choice for final prototypes or small batch production.

Versatile Color Options

Custom coloring is easily achievable by adding pigments directly to the resin, allowing for a wide range of color choices to meet specific design requirements.

Repeatability

Each silicone mold can produce approximately 20 identical parts before it needs to be replaced, ensuring consistent quality across multiple runs while maintaining cost efficiency.

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Disadvantages of Vacuum Casting

Limited Material Choices

Vacuum casting typically uses polyurethane-based resins, which can mimic certain properties of plastics or rubbers but lack the variety and performance of engineering-grade materials like metals or high-performance thermoplastics.

Lower Durability

The materials used in vacuum casting are not as durable or heat-resistant as injection-molded parts or CNC-machined components, making them less suitable for high-stress or high-temperature applications.

Size Constraints

Vacuum casting molds are often limited in size, making it challenging to produce large or complex parts without segmenting the design, which may require additional assembly or compromise the structural integrity.

Limited Production Volume

Vacuum casting is ideal for small production runs (usually fewer than 50-100 units). For higher quantities, the method becomes less cost-effective compared to injection molding or other high-volume manufacturing processes

Tooling Wear and Lifespan

The silicone molds used in vacuum casting have a limited lifespan, typically degrading after 20 uses, depending on the complexity of the part. Frequent remolding increases production time and costs.

Relative Longer Lead Times

Although faster than traditional injection molding, vacuum casting still requires time to create silicone molds, making it slower compared to rapid prototyping methods like 3D printing for urgent projects.

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