The heart of Reaction Injection Molding (RIM) is versatility. Like its name implies, it is a reactive process. Using polyurethane or foamed polyurethane, the process reacts and adapts, filling an existing mold or encapsulating an existing component. To get an understanding of how it works, picture liquid plastic flowing throughout all the features in your mold, then solidifying.
Encapsulation is an invaluable process that opens up many previously unconsidered possibilities for new product designers. It can be used to encapsulate circuit boards, castings, machined parts and much more, enhancing their performance while minimizing costs.
A great example of the capabilities of RIM comes in the form of a 5 ft. long circuit board that we worked on. The company we worked with was manufacturing the boards for use in commercial air traffic control radar antennas. These antennas are constructed outdoors. Previous production attempts were very labor intensive, and did not give the boards consistently adequate protection from the elements. As a result, the success of the entire project was in question.
What the customer desperately needed was a cost-effective material and manufacturing method that totally encapsulated the fragile circuitry, while remaining radar transparent. Using RIM and a high-density foam polyurethane manufactured by the Bayer Corporation, the encapsulation followed the shape of the board. The mold incorporated gussets and attachment bosses with protruding coaxial connectors. In this way the boards were protected, but could still interact with the systems they needed to.
RIM can handle intricate parts like the 5 ft. circuit board without a problem. When complete, RIM produces parts that are dimensionally stable, chemically resistant, physically tough, wear resistant and aesthetically pleasing. It’s an excellent option for large parts produced in short run or low volume production quantities.
When machining something from solid stock, it’s necessary to chip away excess material. Casting offers a cheaper alternative: Make a mold, pour in molten metal, and get out a finished metal casting. The only downside is that to begin this process you have to purchase tooling made specifically to manufacture your part. This can be a large upfront cost which often time bars people from choosing casting—which is why we bypass tooling.
One-shot casting, as the title of our blog announces, is a quick and inexpensive process for creating prototypes. This is for design engineers looking to evaluate new products. New parts and products don’t come together perfectly the first time. You sketch out a CAD drawing, manufacture what you need, put the part together and it doesn’t work. So you go back to the drawing board, tweak the design to fix the problems, then try again. Then marketing has a new idea, or the product application changes, and you repeat the process once again. One-shot casting is perfectly suited to this trial-and-error process.
We exaggerated a bit when we said we bypass tooling. What we do is bypass expensive tooling. Tooling, although it has a higher upfront cost, is a onetime investment. You can continue to use the same tooling over and over again and it pays for itself when used for a full production run.
One-shot casting utilizes disposable tooling. It doesn’t cost much, but it can only handle small runs. Most often we see orders for 1 to 5 pieces, and we’ve gone as high as 25. So when your design is perfected, you’ll still have to purchase tooling if you want to pursue casting. But one-shot casting will enable you to perfect that design. And the best part? Our clients can go from sending us a CAD file to opening a box containing their finished part in about a week. You’re looking at days to test a design, not weeks. Which means not only do you get to perfect your product for less money, you can get it to market in a fraction of the time.