Product development concerns problem solving. Most products are conceived by identifying a problem and envisioning a product as the solution. The development of that product from the initial vision to the retail shelf proceeds through a series of problems and solutions. Experience solves some problems and trial and error solves others. Problems that arise during manufacturing present some of the most frustrating areas in the product development process. This is especially true for injection molded products.
The development process for injection molded products is usually long and arduous. By the end of that process, you’ve spent a lot of time and money on development and tooling. Now you face a production deadline that looks a bit scary, especially when you finally get the parts from the molder and they just aren’t right. Stay calm! A little bit of advanced planning, some knowledge of often underutilized technologies, and a good part review and troubleshooting process can alleviate some of that stress.
One of the biggest mistakes people make is failing to schedule first, second, and third shot reviews of injection molded parts. These reviews should be an expected part of the process. In today’s fast-paced, low-cost environment, optimism leads to skipping this necessary process.
First shots are the first complete parts off the injection molding machine. The designer reviews these parts and checks their dimensions against the files that were provided to the toolmaker. Expect to make adjustments from this review. Second shots are the parts made after those adjustments. With luck, everything has been addressed and your parts are good at this point; however, it is possible—and expected from a scheduling standpoint—that another round of adjustment is necessary.
Another issue is that all today’s available tools and information are not utilized. I have seen molds made improperly because the manufacturer did not read the data sheet for the material to be molded and the length of the runner was too long. Material suppliers possess a great deal of knowledge and material-specific literature for mold design and processing. Use it. Mold flow analysis software is also widely available now. It should be used during the part design and the mold design processes. This software simulates how the plastic will flow through the mold. It will even show the optimal location where the plastic should be injected (gate location). The cost of molds today should mandate this step in every mold build. Another fairly new technology, “scientific molding,” involves the separate control of the molding parameters that yields very consistent parts. Discuss this technology with the molder to see if the parts being molded would benefit from its use.
The part review and troubleshooting process directly affects the bottom line. The parts need to be right. Parts rarely come out completely as expected. It doesn’t much matter why the parts are not the way you expected. With time as your enemy, all that matters is fixing it. This can mean adjusting the mold only a few thousands of an inch to make a snap work better or a latch engage properly. In a best-case scenario, the adjustments are “steel safe,” meaning that you add plastic to the part by removing material from the mold. If you must reduce material from the part, then you must weld material onto the mold and machine it down—a much lengthier process.
Product development entails a series of problems and their solutions. The stress at the end of the process sometimes makes the last steps the most frustrating. Planning for that, doing everything you can to prevent the problems before they happen, and having a good process in place for part review and troubleshooting make it all a bit less painful.