Urethane casting, also known as silicone molding or Vacuum casting, is an economical alternative to pre-series injection molding of plastic parts. Usually, the mold uses CNC machined parts or 3D Printing parts/SLA parts as prototypes, made of silicone material, and polyurethane PU material is cast through the process of vacuum injection to make parts. Duplicate parts can accurately replicate the structure, details, and texture of the prototype and provide a consistent surface finish to obtain results similar to injection molding production.
Generally, before mass production of products, small batch production will be carried out in advance to test product performance and market demand, so as to avoid blind production causing product backlog and unnecessary losses.
If it is a pre-series production, the preferred process is urethane casting, because this process is suitable for the one-time molding of complex structural workpieces, which can effectively shorten the development time and save research and development costs.
PROTO MFG’S Advantages of Plastic Urethane Casting
1. Reduced Labor Costs;
2. Flexible Production Quantity;
3.Tight tolerances: Can be 0.1mm
4. Ability to Produce Complex Parts
5. Works for a wide range of Material Type
Step 1: Make a Prototype
The quality of the complex depends on the quality of the prototype, and when you need to maintain high precision, high finish or even optical clarity, the prototype is best machined by CNC machining.
In addition, for parts with complex shapes and structures, we will also consider using SLA to make prototypes.
We can spray texture or matte effect or silk screen on the surface of the prototype to simulate the final mold texture of the product.
The silicone mold will accurately reproduce the details and texture of the prototype, and the surface of the final replica will maintain a high degree of consistency with the original. And the tolerance can be within 0.1mm.
Step 2: Make the Silicone Mold
The pouring mold is made of liquid silicone, also known as RTV mold. Silicone rubber’s chemical stability, self-release properties and flexibility allow for minimal shrinkage and efficient replication of part details from prototype to mold. The production steps of the silicone mold are as follows:Adhesive tape is applied to the flat places around the prototype for easy mold opening later, which will also become the parting surface of the final mold.The prototype is suspended in a box, and glue sticks are placed on the parts to set the sprue and vent holes.Fill the box with silicone and vacuum it, then cure it in an oven at 40°C for 8-16 hours, depending on the volume of the mold.
After the silicone rubber is cured, the box and the glue stick are removed, and the prototype is taken out of the silicone to form a cavity, and the silicone mold is made.
Step 3: Urethane casting
PROTO MFG’s standardized operating procedures ensure accurate part reproduction and consistent mechanical properties. Our technicians control all operating parameters: mixing, venting, agitation, preheating, pouring and demoulding, providing near-perfect replicas of prototypes. The process of vacuum injection molding is as follows:First put the silicone mold into the oven and preheat to 60-70℃.
To prepare polyurethane resin, preheat it to about 40°C before use, mix the two-component resin in the correct ratio, then fully stir and degas under vacuum for 50-60 seconds.The resin is poured into the mold inside the vacuum chamber, and the mold is cured again in an oven. Average curing time: 1-3 hours for small pieces, 3-6 hours for large pieces. Remove the casting from the silicone mold after curing. Repeat this cycle.
Featured Capability of Materials
Featured Capability of Finishing
It is used in the processing of various small and medium-sized electronic product shells. It is made by CNC/silicone/aluminum molds and other simple molds. It does not need to open steel molds. The quality is stable, the cost is low, and the delivery time is fast.
Electronic product urethane casting:
Processing method: CNC milling & Urethane casting
Material: ABS, PE, acrylic, PC, PEEK/plastic/aluminum alloy, etc.
Surface treatment: deburring, polishing, oil spraying, UV, silk screen printing
Processing cycle: 3-7 seven working days
Testing standard: customers provide 3D drawings
Data format: STP/IGS/XT/PRO
Product features: Environmentally friendly materials, high manufacturing precision, baked varnish on the outside, bright luster, product standards, and beautiful appearance.
We provide high-quality mechanical parts production solutions to support your product development and go to the market needs with Urethane casting technologies. Proto MFG’s manufacturing solutions will give you Stable, committed, on-time, quality, and smooth communication to create, test and refine in ways you never thought possible so you can go to market faster.