Resin casting, also known as RTV casting, is the process of injecting a silicone or urethane resin into a mold to form a part. At Touchstone 3D, we commonly use this process to simulate injection molded parts due to the similarity in design requirements and material properties.
How does it work?
In order to cast resin, you have to first make a mold tool. These tools are typically made from silicone or in some cases 3D printed. Once you have a mold made, the resin can be hand or machine injected (at low pressure) into the mold. Different materials can take anywhere from a few minutes to days to cure, and then the part can be demolded.
Small Batch Runs
When you need to produce an aesthetically appealing prototype, it makes sense to 3D print the design and then sand and paint it. The finishing is time consuming, but you would only need to do it once. But what if you needed to make ten prototypes? Or 50 prototypes? The cost of labor for finishing would quickly become a major problem.
Instead, consider using resin casting. During the mold making process, apply the finishes to the master pattern that the mold comes from. Then every part that comes out of the mold will look like that. This significantly reduces your unit costs.
When to Switch to Injection Molding
For most parts, the break even to switch over to injection molding is typically around 50-100 parts. However you should also consider cash flow and speed. It is significantly faster to produce a silicone mold and resin parts than an injection mold. Resin parts generally cost more per unit than injection molded, but that is usually acceptable for bridge production while you ramp up mass production operations.