Vacuum Casting

Vacuum casting is a prototype manufacturing process that uses silicone molds to quickly create urethane casting parts for the production of small batches of functional 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 CNC machining or SLA part as a master pattern. These molds duplicate intricate details and textures and give consistent finishes from one part to the next. You can get production-like results including mechanical traits, wall thickness, colors, and surface finishes.

Urethane Casting | WayKen

Advantages of Vacuum Casting

  • Low cost for silicone molds
    Cast urethane parts are made of cheap molds, eliminating the need to invest in expensive and time-consuming metal tooling. It is a cost effective method for making high quality prototypes and low volumes of parts.
  • Fast delivery
    Up to 50 functional cast urethane parts can be produced in 10 to 15 days when you choose vacuum casting.
  • A wide selection of materials
    Casting resins materials range from soft and flexible to rigid and impact-resistant, as well as colored and clear.
  • High precision and fine details
    Vacuum casting provides end-use parts of high precision and fine details with production-level quality.
  • Excellent surface finish
    Urethane casting can provide better surface textures 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 vacuum 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 model 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 in that it gives minimal shrinkage and carries fine details effectively from master to mold. The mold making process starts as follows:

  • Paste tape in a 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 casting box and placed with plastic rods to set gates and vents.
  • Liquid silicone is poured around the master and removal all air, creating a vacuum chamber to ensure the master mold is free of air bubbles. Then is cured liquid material 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, cut open the casting box, remove the master model from the silicone to form an empty cavity, and the silicone mold is made.
  • Step 3. Casting Process

    WayKen standardized operational procedures assure accurate part replication and consistent mechanical properties. Our vacuum casting technicians to 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 manufacturing processes of vacuum casting parts are 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 them to about 40°C before use. Mix two-component casting resins in exact proportions, and then fully stir and degas for 50-60 seconds under vacuum to avoid air pockets or bubbles
  • 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 vacuum casting work cycle.
  • Excellent Urethane Casting Services

    We produce a low volume of production quality parts.

    Vacuum Casting Materials

    Urethane resins are polymers with a wide range of properties and use. 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), 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 to ensure the mold is filled properly.

    Lifetime of the silicone mold

    Typical quantities up to 20-25 copies per mold. If the part requires high quality such as clear or complex structures, in typical quantities 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, depending on the mold’s complexity and volumes.

    Surface textures and other functions

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

    The Applications of Vacuum Casting

    Vacuum casting is a great method 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.

  • Low Volume Manufacturing / Short Production Runs
    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 rapid prototyping manufacturing services help you to create custom and complex production parts in low volumes faster than traditional tooling and molding.

  • Aesthetic Models / Color & Texture Studies
    The casting urethane part can be a full set aesthetic model with various colors, textures, and surface finishes under the same design idea. If have no idea about what color would be the most suitable for a final product, you can make a silicone mold to produce 10-15 castings and paint each cast part with your design colors and textures to discuss internally during a meeting among design departments or even management meetings.
  • Engineering Verification / Functional Testing
    The vacuum 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 function testing before testing the mass production products and issue reports or even get any certification approval.

  • Marketing Ready / Display Models
    End-user functionality and a high-quality finish make 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 is 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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