Advantages of Near Net Molding and Finish Machining of Injection Molded Parts

Published on August 18, 2023

A newer injection molding technique that makes parts to “near net shapes” looks to produce molded components that come out as close to their desired dimensions as possible. After coming out of the molds, parts need only minimal machining or other post-production processing to meet the required specifications. This near net shape manufacturing method aims to balance high precision and part cost, cutting production time, reducing waste, and enhancing efficiency overall.

The use of near net shapes in injection molding simply refers to using molds that come as close as possible to the desired dimensions of a part. Before this manufacturing concept, conventionally injection molded parts performed well when only loose tolerances were required. Though parts formed to near net shapes still require machining, this processing method works well for low to mid-range production throughputs.

Using Near Net Shapes to Produce Precision Plastic Components

Precision machining of parts has traditionally been seen as a preferred fabrication technique for components where wall thickness varies significantly, or production runs are lower. Machining also offers a means to make extraordinarily complex parts, which conventional injection molding processes cannot achieve. However, injection molding using near net shapes allows manufacturers to fabricate precision parts at a greater scale.

A newer injection molding technology, the practice of using near net shapes offers considerable savings over the costs of CNC (computer numerical control) machined components. This is especially true when working with materials like PAI (polyamide-imide), PEEK (polyetheretherketone), TPI (thermoplastic polyimide), and other high-performance plastics. Near net shape molds are less expensive and, even with being machine-finished afterward, result in less waste. Using near net shapes with injection molded parts helps companies achieve sustainability goals.

The near net process even works well for larger parts, such as those with blanks weighing up to 6 pounds (about 2.7 kg). It additionally allows for more complex geometries and greater variation in wall thickness, while standard injection molding techniques are unable to produce parts with cross-sectional areas that are too thick. In fact, this technology opens up revolutionary opportunities for the aerospace, medical equipment, oil and gas, semiconductor, and other industries that benefit from precision parts that cost less.

Near Net Shapes and Injection Molding

The injection molding process’s complexity, especially at scale, involves a great deal of complicated engineering. Surfaces of the mold must produce as-molded components with a certain appearance and finish. These molds also require robust construction and must be made from materials that can withstand the extreme temperatures and internal pressures to which they’ll be exposed during high production runs.

Tooling required for near net shapes experiences less demanding pressure, however. Because post-molding machining is integral in achieving the desired finish, the mold’s surface can be of lower quality. Fixturing holes, undercuts, and other complex features can additionally be machined into these near net shapes, which means simpler and less costly mold designs. For mid-range production, mold materials need not be as tough since they don’t go through the rigors of high-volume production typical with traditional injection molding methods.

The near net shape manufacturing process uses extruded or injection molding blanks to produce precision parts with complex geometries for low-volume and mid-volume fabrication. As a widely used manufacturing technique, injection molding already produces plastic components cost-effectively. Yet, with near net shapes integrated into established injection molding methods, parts manufacturers can enhance both accuracy and efficiency. Along with these other benefits of manufacturing with near net shapes, it reduces waste.

Advantages of Near Net Shapes When Fabricating Precision Components

Utilizing near net shapes offers parts manufacturers the means to benefit from both CNC machining and injection molding technologies. The components are first molded to their approximate dimensions quickly and faster than machining can produce. After the parts come out of the mold, these near net shapes are machined to specifications that allow tighter tolerances and more complex part geometries.

Advantages presented using near net shapes in precision plastic parts include:

  • Accelerating the rate at which complex components come onto the market.
  • Allowing manufacturers to use resources more efficiently to increase productivity.
  • Augmenting dimensional accuracy and surface finishes by cutting down on the machining or finishing processes necessary after molding.
  • Bridging the gap between techniques for injection molded and machined components to fabricate parts with complex geometries that would otherwise be too costly or challenging to machine.
  • Decreasing production time by minimizing the need for complex tooling.
  • Increasing the speed at which precision components can be produced.
  • Reducing reliance on costly molds normally required in the injection molding process.
  • Reducing waste by creating molds to near net shapes ensures components closely resemble the desired end product, resulting in less material waste in post-processing.
  • Streamlining manufacturing processes by eliminating the necessity for multiple machining procedures post-molding.

In addition to these advantages, molding to near net shapes allows the use of many different types of plastics. This ensures parts meet specific parameters for compatibility within an application. With a greater range of materials available, precision plastic components can be customized to meet the needs of more industries. Customization can enable manufacturers to become more creative and flexible in their component designs, with near net shapes improving both the performance and functionality of precision parts made from plastic.

Challenges When Considering Near Net Shape Part Fabrication

Though near net shapes provide significant benefits, several considerations should be considered before committing to this fabrication technique. For example, appropriate materials must be selected before fabricating parts with near net shapes. The mechanical properties of a material must be compatible with the application, including its ability to achieve the desired tolerances.

Design considerations also play an important role in fabrication when using near net shapes techniques to make parts. Draft angles, part geometries, tolerances and other features must be considered carefully, so there must be close collaboration between manufacturers and designers. While enabling greater design creativity, near net shapes used for injection molding of parts still have limitations.

Maintaining quality is also necessary, as it is with any precision part. As injection molding with near net shapes is a newer technology, it’s imperative to employ effective inspection procedures for both the injection molding and machining of components. This should include dimensional assessments, functional evaluations, and surface finish analysis to ensure components meet the necessary design specifications.

Ask Spaulding if Near Net Shapes is Right for Your Application

As a company, Spaulding Composites has been working with laminates and thermoset composites for a century-and-a-half. To stay in business this long means keeping abreast of new technologies, like those using near net shapes processing for precision parts. If you’re unsure whether injection molding using near net shapes techniques is right for your application, contact the experts at Spaulding Composites today.