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Understanding Plastic Prototyping

Prototyping is a critical stage in the design process for nearly every project. When developing a product, it’s important to get proof of concept and check the fitment as soon as possible. In decades passed, plastic prototyping consisted of making a prototype mold to finalize a design before investing in production tooling. However, the industry was forever changed by the speed and simplicity of 3D printing. 3D printing is undoubtedly a powerful tool for engineers and designers, however, that doesn’t mean there’s no longer a need for prototype mold building.

3D Printing

If you have a part designed and ready for prototyping, there is almost no reason not to 3D print it for initial testing. Over time, the accuracy of 3D printing has improved significantly, while the cost of the machines (and therefore 3D printed parts) has decreased considerably. This may sound like the end for prototype injection molds, but it’s missing some important points.

  • A 3D printed part is unlikely to perform exactly like an injection molded part. Because of the nature of 3D printing, it does not create the same polymer flow as injection molding. Therefore, material properties like strength and flexibility cannot be adequately replicated.
  • If a specific material is required, it may not be available for 3D printing (though there is an ever-increasing range of materials available for 3D printing).
  • Prototyping using an injection mold simulates the shrink and warp in a production injection molding environment. For molded parts with critical dimensions, a prototype allows for easy adjustments to dimensions that can then be replicated on a production mold.

Check out this article on injection molding and 3D printing for more information on the differences.

Prototype Molds

Due to standardization and specialization, the costs and lead times of prototype injection molds have decreased over time. Injection mold builders often standardize molds so that most of the work and machine time required is complete before a part form is machined in. The standardization of mold bases and mold frames also makes them reusable from project to project, which prevents the direct cost common components from being passed on to the end user.

Many mold builders now specialize only in prototype injection molds, allowing them to streamline lead times. From the quoting process through design and construction, every detail of the project is optimized for efficiency.

Production-Ready Prototype Molds

For projects with a tight time frame, it’s often economical to produce prototype tooling with the additional intent of satisfying initial order quantities. These prototype molds are built to higher quality standards and will last significantly longer than quick turn-around prototype molds. At the same time, in order to keep the cost of mold changes to the prototype low, these molds often have lower cavitation than the actual production mold.

It’s also possible to build a one cavity mold for prototyping. If a production mold is sixteen cavities (creates sixteen parts on each molding cycle), finishing one cavity for prototyping avoids changing all sixteen cavities if an adjustment is needed. Once the one part is acceptable, the remaining fifteen can be completed.

Mold Inserts Only

Injection molds intended for high volume production typically consist of a mold frame and tooling. The mold frame is a series of plates, pins, bushings, and supports that holds the tooling and provides a connection point to the molding machine. The tooling is what has the part form and what comes into contact with plastic to make the part. At Basilius, we’ve developed a proprietary mold base that can accept tooling from various projects. In this case, the end-user only has to pay for tooling instead of the entire mold. Because of this, the mold is less expensive, and the lead time is shorter. Check out this post for more information on mold inserts only (MIO) options at Basilius.

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