Injection Molding: Design for Manufacturing

Injection molding part design: 3 key principles

At Canyon Components, we’re experts in injection molded parts. Injection molding offers several advantages that make it a popular and widely used manufacturing process. First, it allows for high production volumes with consistent quality. The ability to rapidly produce identical parts with tight tolerances ensures efficient mass production and reliable product performance. Injection molding also provides a wide range of material options, allowing for versatility in meeting various design requirements, including strength, flexibility, and durability. Available materials include, but are not limited to, PEEK, Polycarbonate (PC), Nylon, silicone, Viton, and more! Additionally, the process offers the capability to create simple shapes like O-rings and gaskets, to complex shapes and intricate details, making it suitable for a broad range of applications across industries.

When designing parts for injection molding, there are three key principles to follow. These are maintaining a uniform wall thickness, eliminating undercuts, and ensuring a draft angle.

Uniform Wall Thickness

Maintaining consistent wall thickness is critical for injection molded parts. This helps provide consistent and predictable structural integrity throughout the component. When wall thickness is uniform, any applied forces and stresses are dispersed evenly throughout the part, minimizing the risk of weak points or potential failure areas. This uniformity also promotes dimensional stability, ensuring that the part maintains its intended shape and size during the molding process. With varying wall thickness, shrinkage can be inconsistent throughout the part, quickly throwing dimensions out of specification.

Uniform wall thickness contributes significantly to the manufacturability and cost-effectiveness of injection molded parts. Maintaining a consistent thickness allows for better control of the flow of molten plastic during the injection process. This results in more efficient filling of the mold cavity, reducing the likelihood of defects such as sink marks, warping, or voids. It also facilitates shorter cooling times, enabling faster production cycles and higher productivity.

Lastly, uniform wall thickness aids in achieving aesthetic appeal and functional requirements. It allows for consistent surface finishes, preventing visible imperfections such as uneven textures or visible flow lines. By maintaining a consistent wall thickness, manufacturers can produce high-quality, reliable, and cost-effective parts for a wide range of applications.

Eliminate Undercuts

Eliminating undercuts is a critical consideration for injection molded part design. Undercuts are features or recesses in the part geometry that prevent straightforward ejection from the mold, requiring complex mold designs or additional secondary operations. By designing parts without undercuts, manufacturers can simplify the molding process, reduce costs, and improve overall production efficiency.

When undercuts are present in a part design, special mold features like side actions or lifters may be required to facilitate their release from the mold. These additional features increase the complexity of the mold design, leading to higher tooling costs, longer lead times, and even additional maintenance requirements. By eliminating undercuts, the mold design can be simplified, resulting in shorter production cycles and lower production costs.

Draft Angle

Draft angle is an essential consideration in the design of injection molded parts due to its significant impact on the ease of part ejection from the mold. Draft angle refers to the taper or angle applied to the vertical walls of a part, allowing for smooth and efficient removal from the mold cavity. Through the incorporation of a draft angle, the frictional forces between the part and the mold are reduced, enabling easy and consistent ejection without causing damage to the part or the mold.

The draft angle serves multiple purposes in injection molding. Firstly, it facilitates the release of the part by preventing it from getting stuck or binding within the mold. As the mold opens, the draft angle enables a gradual and controlled removal of the part, minimizing the risk of deformation, breakage, or the need for excessive force during ejection.

Draft angle plays a crucial role in improving the overall surface finish of the molded part. As the part is ejected, the draft angle helps prevent undesirable marks or scratches caused by friction between the part and the mold. It also allows for smoother flow of the molten plastic during the injection process, reducing the occurrence of cosmetic defects such as flow lines or sink marks.

Designing an appropriate draft angle is essential to ensure the success of the injection molding process. The specific draft angle required can vary depending on factors such as the material being used, the complexity of the part geometry, and the type of mold used. It is typically recommended to incorporate a draft angle of at least 1 to 2 degrees, although more significant angles may be necessary for certain part designs or materials with higher coefficients of friction.

Verification of Design Success: Rapid Prototyping

Once you have designed a part following the design principles discussed above, you can use tools like rapid prototyping to verify your part design. When using rapid prototyping techniques such as 3D printing or machining, designers can quickly and cost-effectively create physical prototypes of their parts or products. These prototypes provide a tangible representation of the design, allowing for a thorough evaluation of its form, fit, and function.

When physically holding and examining a prototype, designers can identify potential design flaws or areas for improvement that may not have been apparent in a digital model. They can assess factors such as the ergonomics, aesthetics, and overall usability of the design. This hands-on approach enables designers to gain valuable insights and make informed decisions about necessary design revisions.

Rapid prototyping also allows for faster iterative design cycles, where modifications can easily be made based on the analysis of a prototype. Designers can quickly revise the digital model, produce a new prototype, and test it again. This iterative process accelerates the design refinement phase, reducing development time and costs associated with traditional manufacturing methods.

Finally, rapid prototyping enables functional testing of the part design. By creating prototypes that closely resemble the final product in terms of materials and properties, designers can perform various tests to evaluate factors such as structural integrity, assembly fit, and performance. This helps to identify and rectify potential issues early in the design process, minimizing the risk of costly errors or delays during production.

By leveraging rapid prototyping technologies, designers can streamline the product development process, improve design outcomes, and ultimately deliver higher-quality products to the market. If you’re interested in procuring prototype parts to start your design evaluation, please CONTACT US HERE.

Where can I get custom injection molded parts?

At Canyon Components, we offer a variety of services surrounding custom injection molded parts. Whether you need part design assistance, rapid prototyping to verify your design, or mass-production of a finished design, we’re here to help!

CONTACT US HERE to learn more.

Sources:

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[2] "Application Overview: Injection Molding". Yaskawa America, Inc. Archived from the original on 2006-04-12. Retrieved 2009-02-27.

[3] Todd, Robert H.; Allen, Dell K.; Alting, Leo (1994). Manufacturing Processes Reference Guide. Industrial Press, Inc.

[4] White, James Lindsay (16 January 1991). Principles of Polymer Engineering Rheology. John Wiley & Sons. ISBN9780471853626.