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Have you considered optimizing your part design to improve overall quality while simultaneously reducing production costs and shortening lead times? Through strategic design choices—particularly in features like ribs and undercuts—you can significantly enhance both manufacturability and final part performance. The following six design tips outline proven techniques for developing efficient, cost-effective, and structurally sound injection molded components.
1. Design Ribs with Uniform Wall Thickness
Ribs are integral to the structural integrity and functionality of plastic parts. In addition to reinforcing the component, they serve as flow channels for molten plastic and support alignment or positioning of internal elements. To prevent molding defects and ensure consistent quality, ribs should maintain a uniform wall thickness relative to adjacent features.
For example, in the original bearing cap design, clamping at point A was hindered by insufficient claw length, while point B posed alignment challenges. In the revised design, the conical surface at point B was replaced with a cylindrical surface at point C for improved clamping. Alternatively, an additional cylindrical surface at point D can also be introduced to facilitate secure fixture engagement.
2. Add a Bevel to Rib Tops to Prevent Air Traps
Incorporating a slight bevel or chamfer at the top of each rib allows trapped air to escape during the injection process. This small adjustment helps prevent voids and surface defects while supporting smooth material flow.
3. Align Ribs with the Flow Direction of the Melt
Ribs should be oriented in the same direction as the flow of molten plastic. This alignment improves fill consistency, reduces the chance of flow hesitation or turbulence, and lowers the risk of cosmetic flaws such as short shots or air entrapment.
Undercuts complicate mold design and typically require the use of side-actions or lifters—mechanisms that increase tooling complexity and cost. Whenever possible, undercuts should be minimized or eliminated through thoughtful design changes.
4. Avoid External Undercuts by Redefining Parting Lines
Revisiting the parting line layout can help eliminate the need for side-actions. For instance, certain exterior undercuts can be avoided altogether simply by adjusting the part’s parting plane, allowing for direct ejection without the need for additional mold complexity.
5. Redesign part features to avoid part undercut
Many undercuts are the result of specific design features that can be reimagined or relocated. Modifying these elements often enables the use of simpler two-part molds and removes the need for costly mechanical slides or collapsible cores.
6. Redesign part features.
The part contains an undercut that would typically require side-actions for demolding. However, by redesigning the part features, side-actions can be avoided, as demonstrated by four optimized design approaches.
