12 Design tips for plastic injection parts

Plastic injection molding is a popular method for producing parts and products, as it offers a range of advantages such as high efficiency, low cost, and versatility. However, achieving the best design for plastic injection parts requires careful consideration of various factors. In this article, we will provide 12 design tips for plastic injection parts to help you optimize the design process and achieve the best results.

Design Tip #1: Wall Thickness

One of the most critical factors in the design of plastic injection parts is the wall thickness. Maintaining uniform wall thickness throughout the part is essential to ensure proper filling and packing during the molding process. Uneven wall thickness can result in warping, sink marks, and other defects. Typically, the recommended wall thickness for plastic injection parts is between 2-4mm, although this can vary depending on the material and the specific requirements of the part.

When designing the wall thickness, it is essential to consider the material flow and cooling in the mold. Thick sections of the part will take longer to cool, leading to potential shrinkage and warping. On the other hand, excessively thin walls can result in flow marks, burn marks, and other cosmetic defects. Therefore, it is important to carefully evaluate the structural requirements of the part and ensure that the wall thickness is optimized for both mechanical performance and moldability.

Design Tip #2: Rib Design

Ribs are often used in plastic injection parts to improve their stiffness and strength without adding significant weight or material. When designing ribs, it is important to maintain a proper thickness-to-height ratio to ensure that they can be filled properly during the molding process. A good rule of thumb is to design ribs with a thickness that is 60-80% of the adjacent wall thickness, and a height that is no more than 3 times the thickness.

In addition to the thickness-to-height ratio, it is important to consider the placement and orientation of the ribs to ensure that they provide the necessary reinforcement without causing flow restrictions or creating stress concentrations. Properly designed ribs should enhance the overall performance of the part without compromising its moldability or introducing potential defects.

Design Tip #3: Draft Angles

Draft angles are essential in plastic injection molding to facilitate the ejection of the part from the mold. Without proper draft angles, the part may stick to the mold and result in production issues and defects. When designing plastic injection parts, it is important to incorporate draft angles on all vertical surfaces to ensure smooth ejection and minimize the risk of damage to the part or the mold.

The recommended draft angle for plastic injection parts is typically 1-3 degrees per side, although this may vary depending on the specific material and geometry of the part. It is important to carefully evaluate the draft requirements during the design phase and ensure that they are integrated into the part geometry without compromising its functionality or aesthetics.

Design Tip #4: Gate Placement

The gate is the point where the molten plastic is injected into the mold cavity, and its placement is crucial to the overall quality of the part. Proper gate placement can help minimize flow restrictions, reduce weld lines, and ensure uniform filling of the mold cavity. When designing plastic injection parts, it is essential to carefully consider the gate location to optimize the molding process and minimize potential defects.

The ideal gate placement will depend on various factors such as the part geometry, material properties, and production requirements. Common gate types include edge gates, tunnel gates, and hot runner systems, each of which has its own advantages and limitations. It is important to work closely with the mold designer and injection molder to determine the most suitable gate placement for the specific part and ensure that it meets the desired performance and quality standards.

Design Tip #5: Undercuts and Side-actions

Undercuts and side-actions are features that require special attention in the design of plastic injection parts, as they can complicate the molding process and increase production costs. Undercuts are features that prevent the part from being ejected straight out of the mold, while side-actions are mechanisms used to create these features in the mold.

When designing plastic injection parts with undercuts or side-actions, it is important to consider the impact on mold design, cycle time, and part cost. It may be necessary to incorporate additional mold components, such as slides, lifters, or collapsible cores, to accommodate these features and ensure that the part can be successfully molded. It is essential to work closely with the mold designer and injection molder to develop an effective solution for handling undercuts and side-actions and minimize their impact on production.

In conclusion, the design of plastic injection parts plays a crucial role in the overall success of the molding process. By carefully considering factors such as wall thickness, rib design, draft angles, gate placement, and undercuts, it is possible to optimize the design for moldability, performance, and cost-effectiveness. Collaboration between the part designer, mold designer, and injection molder is essential to ensure that the design meets all the necessary requirements and achieves the desired quality and functionality.

In summary, successful plastic injection part design requires a thorough understanding of the molding process and the specific requirements of the part. By following the 12 design tips outlined in this article, it is possible to optimize the design for moldability, performance, and cost-effectiveness. From wall thickness and rib design to draft angles and gate placement, each aspect of the design must be carefully evaluated to ensure that the final part meets the desired quality and functionality. Through collaboration between the part designer, mold designer, and injection molder, it is possible to achieve the best results and produce high-quality plastic injection parts.