Vacuum Casting
Bring your product from the design and prototyping stage through to full production with our experts.
What Is Vacuum Casting?
Vacuum casting, also known as urethane casting, presents a cost-effective substitute for low-volume plastic injection molding. Its capability to closely mimic final molded parts or finished products makes it an appealing choice. Typically, silicone rubber molds are utilized, employing CNC machining or SLA parts as master patterns. These molds expertly replicate intricate details and textures, ensuring consistent finishes across all parts. The process yields production-like results, encompassing mechanical traits, wall thickness, colors, and surface finishes.
Advantages Of Vacuum Casting
Rapid Delivery: Opting for vacuum casting allows the production of up to 50 functional cast urethane parts within a swift 10 to 15-day timeframe.
Versatile Material Selection: The casting resins cover a wide range of options, from soft and flexible to rigid and impact-resistant, available in various colors and clarity levels.
Precise and Detailed Output: Vacuum casting ensures high precision and fine details, delivering end-use parts of exceptional quality akin to production-level standards.
How Vacuum Casting Works
Step1. Master Pattern Making
The quality of casting urethane parts relies on the master pattern’s precision, achieved best through CNC machining when tight tolerances, glossy finishes, or optical clarity are essential. For more intricate shapes and structures, we may opt for SLA to create the master.
To simulate the final mold texture of the product, we can apply paint to the parts’ surface for texture or a satin effect. Silicone molds will replicate the details and textures from the original master, ensuring that the cast urethane parts match the master model without any additional surface finishing required.
Step2. Silicone Mold Making
The casting molds, also known as RTV molds, are crafted using liquid silicone resin. Silicone rubber’s exceptional chemical stability, self-releasing properties, and flexibility ensure minimal shrinkage and effective replication of fine details from master to mold. The mold making process unfolds as follows:
- Place tape around the master in a flat position, serving as the parting surface for the final mold, facilitating easy mold opening later.
- Suspend the master model in a casting box, using plastic rods to establish gates and vents.
- Pour liquid silicone around the master while eliminating all air to create a vacuum chamber, ensuring the master mold is bubble-free. Cure the liquid material in an oven at around 40℃ for 8-16 hours, depending on the mold volume.
- Once the silicone rubber cures, cut open the casting box, remove the master model, and unveil the empty cavity, forming the silicone mold.
Step3. Casting Process
Kevorapid standardized operational procedures ensure precise part replication and consistent mechanical properties. Our skilled vacuum casting technicians meticulously control all operational parameters, including mixing, de-gassing, stirring, preheating, casting, and de-molding. The manufacturing process for vacuum casting parts is as follows:
- Preheat the silicone mold in the oven to 60-70°C.
- Select an appropriate release agent, apply it correctly before closing the mold to prevent stickiness and surface defects.
- Preheat the polyurethane resins to around 40°C. Mix two-component casting resins in precise proportions, thoroughly stirring and degassing for 50-60 seconds under vacuum to eliminate air pockets or bubbles.
- Pour the resin into the mold within the vacuum chamber under computer control. Cure the resin again in the oven, with an average cure time of 1-3 hours for small parts and 3-6 hours for larger ones.
- Remove the casting part from the silicone mold after curing, and prepare for the next vacuum casting work cycle.
Applications Of Vacuum Casting
Short Production Runs
- Urethane casting excels in crafting top-notch plastic prototypes. It proves advantageous when production volumes don’t warrant injection molding or short-run parts. With the added benefit of finishing weeks ahead of production tooling, our advanced rapid prototyping manufacturing services enable swift creation of custom and intricate production parts at low volumes, outpacing traditional tooling and molding methods.
Verification / Functional Testing
- The vacuum casting technique, along with its affordable tooling, simplifies the process of engineering verification and design changes. Moreover, it serves as a valuable tool for function testing before mass production, generating reports, and obtaining necessary certifications.
Aesthetic Models
- Incorporating urethane casting allows for the creation of a complete aesthetic model, featuring diverse colors, textures, and surface finishes, all within the same design concept. When uncertain about the ideal color for the final product, utilizing a silicone mold to produce 10-15 castings offers the chance to paint each part with different design colors and textures. This facilitates internal discussions within design departments or management meetings to determine the most suitable options.s.
Marketing Display Models
- Urethane cast parts are perfect for consumer testing and user evaluation, offering excellent end-user functionality and a top-notch finish. The versatility of the cast urethane process allows for swift adjustments, whether for further testing or market launch. At trade shows or exhibitions, showcasing multiple modeled pieces to interested clients is possible. Additionally, utilizing urethane molding for photos enhances the company brochure and official website, attracting more potential clients.
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.
