Since its inception, the injection molding process has primarily operated in one traditional way — what is known as a cold runner system. Here, the plastic or rubber substrate is heated to melting and injected into the mold at a fixed point (or several fixed points) called the sprue. A key point to remember here is that the molding material is injected from outside the mold (using a piston or other pressurizing method) through “runners” (or conduits for the material) built into the mold, and then into the cavity itself. The runner in this process cools along with the rest of the part and essentially becomes a part of the finished product itself, and must be ejected, potentially separated from the finished part, and then recycled and reground into reusable substrate.
Injection molding is a complex process with a number of “moving parts” — both figuratively and literally — that should be monitored during production. The process is versatile enough to be the manufacturing method of choice for a broad range of products, but unfortunately, it is rarely as simple as just building a mold and running it through an injection molding machine. Several factors inherent to the process can affect the quality of your end product, and should be monitored and measured as closely as possible in order to maintain the safety and integrity of your parts.
Failure of your injection molding part can prove to be one of the most costly production issues that you can encounter. Not only must you absorb the cost of rejected pieces, it’s likely that you’ll also need to adjust the design of your product to be more conducive to the plastic injection molding process. Aside from this additional R&D time and expenditure, this means new tooling costs as well. As the direct costs add up, your time to market is also drawn out longer and longer, creating a double-whammy to your bottom line.