Injection mold tooling is the most important part of the injection molding process. Good tooling ensures that each part is made to the same exacting specifications, and lasts as many cycles as necessary to make the full batch. The quality of a molded plastic product largely depends on the quality of the mold itself, from its durability to its surface finish to its strength–so it’s important to get the design of the mold tooling just right. Here are a few things to keep in mind when designing injection mold tooling for your project.
Choose the Right Material
Mold tooling regularly undergoes a lot of stress, from high temperatures to wear and tear from the plastic itself, so getting the right material for the tool is important. Hardened tool steels are common in mold tooling, as they offer much higher durability and strength, and will last a lot longer under the harsh conditions in injection molding. However, these steels can be more expensive, so for short run or prototyping they may not be the most cost-effective choice. Metals like aluminum and stainless steel on the other hand offer decent performance at cheaper costs, but won’t last nearly as many cycles as tool steel.
Incorporate Uniform Wall Thickness for Molded Parts
The design of injection mold tooling is heavily influenced by the design of the part–and certain design aspects can have a big impact on the finished product’s performance. The wall thickness of a part, for instance, will have a big impact on how well the molding process actually goes. The more uniform the wall thickness, even if it is on the thin side, the stronger the part will be when it cools. If your design requires features with different wall thicknesses, then make sure that the transitions between them are gradual and slow. This will help you avoid defects like warping when the part cools.
Pay Attention to Parting Lines
Parting lines are an inevitable aspect of molded components–they occur wherever the two halves of the mold meet. Choosing where the parting line will be is a crucial part of the design, as it can negatively affect the part’s appearance at best, or even its mechanical properties at worst. Pay attention to where the parting line will be and avoid putting features like a fillet or radius across the line.
Take Advantage of Mold Flow Analyses
Injection molding isn’t as simple as pouring molten plastic into the mold and letting it cool. Knowing how the plastic will flow and ensuring that the plastic fills every inch of the mold cavity is crucial for avoiding defects. Early testing such as mold flow analyses allow engineers to examine how plastic will flow into the cavity, and provide insight as to where to add features such as gates, ejection locations, and parting lines, optimizing the design to ensure it will create the desired products.
Final Thoughts
Injection molding is a complex process that requires a lot of forethought and consideration to ensure that the resulting products meet the necessary precision, performance, and aesthetic requirements. The above suggestions are just a few of the things to keep in mind–a little research can go a long way to improve injection mold tooling designs!
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