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10 Myths You Believed About Injection Molding

Written by RevPart

In manufacturing, it’s always a good idea to understand the best practices for the process you intend to use to create a part — whether it’s plastic molding, 3D printing, CNC machining or beyond. Best practices exist for every process, and they have been developed for a reason: they can help ensure the quality of your product; they can make your production process more efficient; and, overall, they can save you significant time and money throughout your development and ongoing production processes.

molding machine

Best practices can sometimes overlap with what’s often called “conventional wisdom.” Many times, however, “conventional wisdom” ends up being the underlying reason for a shop to tell you that it can’t or won’t carry out a specific process or application. In most of those cases, it’s not that something isn’t possible — it’s that the shop doesn’t possess the capability or ingenuity to provide what you need in a mutually beneficial way. Read on to learn more about some of those plastic molding myths:

1. Myth: Injection molding is only suitable for long production runs. In fact, injection molding can be a cost-effective solution for producing a part in nearly any quantity, from prototypes of a few pieces up to large-scale, six- or seven-figure runs. Even for functional prototypes produced from just one cycle, injection molding can provide a solution. Below, you’ll see how.

2. Myth: Manufacturing a mold is exceedingly expensive. This does not have to be the case. While tool steel molds require extensive time and provide unparalleled strength for full production runs — and thus cost a commensurate amount of money to produce — other materials can be used to create molds for shorter run applications. Molds can be 3D printed or even CNC machined from other materials, all at a lower cost than the traditional tool steel mold.

3. Myth: Non-steel molds can only produce very low quantities. Many shops will tell you that even a lower-cost mold made of different material is a poor investment, because it’s only suitable for a few injection cycles, producing a low number of prototype parts. In fact, many non-steel molds can produce thousands of parts with no loss of quality, with some reaching as many as 10,000 pieces. In those quantities, depending on your production and distribution plan, you may be able to use a non-steel mold to produce the pieces you’ll be selling.plastic molding

4. Myth: Short-run molds are easily damaged. Much like the above, the “conventional wisdom” around non-steel molds is that after a few production cycles, cavities can start to become damaged, resulting in unsuitable quality for pieces. The truth is, however, that the quality of the parts produced can be consistent for hundreds or thousands of cycles — again, producing parts numbering in the thousands.

5. Myth: Plastic molding is unsuitable for prototyping. For many of the above reasons, plastic injection molding has a reputation of not being an appropriate process for prototyping parts. It may be called “not cost-effective” or “too time-consuming.” All too often, another process is used to create a prototype, which doesn’t provide the same similarity to the finished product as injection molding might. In reality, injection molding, when the right processes are used, can easily provide cost-effective prototypes in as little as a few days; letting the entrepreneur or other product developer get a sense of how the actual finished product will look, feel and function.

6. Myth: Lead times of several months should be built into molding projects. For tool steel molds, this is true. Molds for long production processes of 10,000 pieces or more do take that amount of time to manufacture. When other materials or processes are used to create the mold, however, the mold can be produced in just a few days, with delivery possible within a week. This time frame can change the entire schedule of your product development process while still providing high-quality prototypes and parts.

7. Myth: Injection molding can’t be both complex and fast. When fast, cost-effective molding is discussed, it’s all too often written off as only possible for simple geometries. This is not the case, however: When creating prototyping and short- run molds, the same compound and complex constructions that tool steel molds can provide can also be fulfilled by 3D printed molds. These processes include:

  • Overmolding
  • Double-shot molding
  • Insert molding
  • Two-shot molding
  • And more

8. Myth: Only certain materials are suitable for injection molding. Because of the way the injection molding process works, a common misconception is that only specific, specially formulated materials are suitable. Heating time, cavity filling, cooling time and injection are indeed complex processes where the makeup of the base resin must be carefully calibrated and monitored to ensure that the entire cycle occurs as it should. The truth, however, is that plastic molding is extremely versatile. What’s more, it’s possible to use a wide range of materials with different qualities and characteristics such as ABS, PET, PVC, polypropylene and many more. Food and medical-grade materials can also be perfectly suited to the injection molding process.plastic molding

9. Myth: Injection molded parts must be customized, painted or otherwise finished post-production. A common misconception is that injection molded parts cannot be aesthetically pleasing, only retaining the (typically unattractive) base color of the resin. Some shops will tell you that any design elements or embellishments must be added in a finishing process after molding has been completed. In fact, injection molds can be designed so that many of these aspects of the part are included as part of the mold. These include special textures or finishing, as well as Pantone matching to create resins of nearly any color. With these capabilities, prototyping for final appearance (which is important for consumer products and other applications) becomes much easier.

10. Myth: The RFQ process for injection molding is complicated and time-consuming. Because of the extensive time and cost that many shops will tell you is inherent to the injection molding process, they will also build in an unnecessarily complex RFQ process. In fact — especially when creating prototype and short-run molds — the process can be as easy as uploading a technical drawing. Thus, helping you get on your way toward a prototype and, eventually, a finished product, that much faster.

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