Urethane Vacuum Casting

Vacuum casting is a prototype manufacturing process that uses silicone molds to quickly create urethane casting parts for the production of small series of functional plastic parts.

What is Vacuum Casting?

Vacuum casting (also known as urethane casting) is an economical alternative to low-volume injection molding of plastic parts and can be used to closely simulate final molded parts or finished products. Generally, molds are made from silicone rubber and use a CNC or SLA part as a master pattern. These molds duplicate details and textures and give consistent finishes from one part to the next. You can get production-like results including mechanical traits, colors, and finishes.

Urethane Casting | WayKen

Advantages of Vacuum Casting

Cast urethane parts are made of cheap silicone molds, eliminating the need to invest in expensive and time-consuming metal tooling.

Up to 50 functional cast urethane parts can be produced in 10 to 15 days.

 Urethane casting materials range from soft and flexible to rigid and impact-resistant, as well as colored and clear.

Urethane casting provides end-use parts of high precision and fine details with production-level quality.

Urethane casting can provide better surface quality compared with CNC prototyping or 3D printing.

Vacuum Casting Service

Fast Short-Run Production Option For Low Volume Plastic Prototype Parts

How Vacuum Casting Works

The urethane casting process has three steps: master pattern, molding, and casting.

Step 1. Master Pattern Making

The quality of the casting urethane parts is determined by the quality of the master pattern, which is best machined by CNC when you need to hold tight tolerance, glossy finish or even optically clear. In addition, we also will consider making the master by SLA for those parts with more complex shapes and structures.
We can paint parts surface for texture or satin effect to simulate the final mold texture of the product. The silicone molds will copy the details and textures from the original master, so the cast urethane parts will come out the same as the master without any extra finish on the surface.

casting urethane - wayken

Step 2. Silicone Mold Making​

Casting molds are made from liquid silicone resin, also known as RTV molds. The chemical stability, self-releasing properties and flexibility of silicone rubber are excellent that it gives minimal shrinkage and carries fine details effectively from master to mold. The silicone mold making steps are as follows:
  • Paste tape in flat position around the master, so that it is easy to open the mold later, which will also become the parting surface of the final mold.
  • The master model is suspended in a box and place plastic rods to set gates and vents.
  • Silicone is poured around the master and vacuum is used to remove all air. This then is cured in an oven, at a temperature of 40℃. It generally takes 8-16 hours depending on the volume of the mold.
  • Once the silicone rubber is cured, remove the master from the silicone to form a cavity, and the silicone mold is made.
  • Step 3. Vacuum Casting

    WayKen standardized operational procedures assure accurate part replication and consistent mechanical properties. Our casting technicians control all operational parameters: mixing, de-gassing, stirring, preheating, casting, and de-molding, allowing for near-perfect copies of the master pattern to be created. The process of vacuum casting parts is as follows:
  • First, put the silicone mold into the oven and preheat it to 60-70°C.
  • It is very important to choose a suitable release agent before closing the mold and use it correctly to avoid stickiness and surface defects.
  • Prepare the polyurethane resins to preheat it to about 40°C before use. Mix two-component resins in exact proportions, and then fully stir and degas for 50-60 seconds under vacuum.
  • The resin is poured into the mold inside the vacuum chamber under computer control, and cured again in the oven. Average cure time: 1-3 hours for small parts and 3-6 hours for big parts.
  • Remove the casting part from the silicone mold after curing. Prepare to repeat this cycle.
  • Excellent Urethane Casting Services

    We produce small series of functional plastic parts with production-level quality.

    Vacuum Casting Materials

    Urethane resins are polymers with a wide range of properties and uses. WayKen offers various urethane materials to meet your applications, including Hei-Cast from Japan and Axson from France. Materials with certain properties are similar to engineering production plastics, such as ABS, PMMA, PC, PP, PA, and so on. Casting parts can be varied from transparent, translucent to colored, and from soft rubber to hard plastic. Various materials contain those impact-resistant, high-temperature resistant (120℃) or fire-resistant (UL94-V0), and glass-filled resins, and different hardness silicone.

    Vacuum Casting Materials

    Technical Guide for Vacuum Casting

    Standard accuracy

    Standard tolerance on ±0.15mm/100mm, with the highest precision able to reach ±0.05 mm.

    Maximum part dimensions

    The vacuum equipment can hold 2.0M*1.2M*1.0M mold specifications.

    Minimum wall thickness

    The minimum wall thickness is 0.5mm, the best is 1.5mm~2.5mm.

    Lifetime of the silicone mold

    Up to 20 copies per mold, while if the part requires high quality such as clear or complex structures, one mold can only make 12 or even 10 casting parts.

    Standard lead time

    Up to 50 copies can be produced in 7 to 10 days, depends on the part specification and volumes.

    Surface finish and other functions

    Colored, textured, painted, coated, clear polished, insert, and over-molding.

    The Applications of Vacuum Casting

    Urethane casting is an effective way to manufacture low-volume production runs for functional prototypes and plastic parts, and helps you strike the right balance between high-quality, end-use parts and production lead-time.

    The urethane casting is perfect for high quality plastic prototypes. When volumes do not justify investment in injection molding and short run production parts, it can complete weeks before production tooling is ready. Our advanced manufacturing services help you to create custom and complex production parts in low volumes faster than traditional tooling and molding.

    The urethane casting process and relatively inexpensive tooling involved make it easy and economical for any necessary engineering verification and design changes. Additionally, these would be used to do functional test before testing the mass production products and issue report or even get any certification approval.

    The casting urethane part can be a full set aesthetic model with various colors, textures and finishes under the same design idea. If having no idea about what color would be the most suitable for a product, you can make a silicone mold to produce 10-15 castings and paint each with your design colors and textures to discuss internally during meeting among design departments or even management meetings.

    End-user functionality and a high-quality finish makes urethane cast parts ideal for consumer testing and user evaluation. The application of the cast urethane process means that changes can be quickly made for either further testing or market launch. At any trade shows or exhibitions, you can display several modeled pieces to clients who are interested. Urethane molding are also needed for photos in preparing the company brochure or being posted on the official website to more potential clients.

    How Vacuum Casting Benefits Your Project

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