Injection Molding Part Design: Avoid These 5 Common Mistakes

Injection molding is a powerful process for creating complex plastic parts, but designing and manufacturing injection molded parts requires attention to detail and a careful consideration of the important design factors. To maximize the success of your part design, it’s important to avoid common mistakes which can cause problems with the molding process. In this article, we’ll discuss five common mistakes to avoid when designing injection molded parts.

Mistake #1: Poorly Defined Wall Thickness

One of the most common mistakes that engineers and designers make when designing injection molded parts is not defining the wall thickness correctly. Wall thickness is an important factor in the injection molding process, as it determines the amount of pressure required for the plastic to fill the cavity. If the wall thickness is too thin, the injection pressure will be too high and can damage the mold or cause deformities in the part. On the other hand, if the wall thickness is too thick, the plastic will not flow properly and the part may not fill completely.

To ensure that your part has the correct wall thickness, you should use a simulation software to determine the required pressure for each section of the part. Additionally, you should consider the effect of shrinkage on the part and ensure that the wall thickness is sufficient after the plastic material has cooled and contracted.

Mistake #2: Insufficient Draft Angle

Another common mistake that engineers make when designing injection molded parts is not providing enough draft angle. Draft angle is the angle at which the walls of the part are sloped to allow for easier removal from the mold. If the draft angle is not sufficient, the walls of the part may stick to the mold and make it difficult to remove. Additionally, a lack of draft angle can also lead to warping or distortion of the part, as the plastic may cool unevenly.

The degree of draft angle required for a particular part depends on the geometry of the part and the type of plastic material being used. Generally speaking, the steeper the draft angle, the easier it will be to remove the part from the mold. When designing your part, it’s important to consider the draft angle and ensure that it is sufficient for the part to be easily ejected from the mold.

Mistake #3: Poorly Designed Corners

Another mistake that engineers commonly make when designing injection molded parts is not designing the corners correctly. The corners of a part can be a difficult area to mold correctly, as the plastic material must flow into the corner and fill it completely. If the corner is not designed correctly, the plastic may not flow correctly and the corner may not fill completely, resulting in an imperfect part.

To ensure that your part has correctly designed corners, you should consider the radius of the corner and the angle of the slope. The corner radius should be designed to be as large as possible to allow the plastic to flow into the corner without any resistance. Additionally, the angle of the slope should be designed to allow for easy release from the mold. By considering these factors, you can ensure that your part will have correctly designed corners.

Mistake #4: Unsupported Features

In addition to poor corner design, engineers and designers often make the mistake of not supporting certain features of the part. Some features of a part, such as overhangs or deep recesses, require additional support during the injection molding process. Without sufficient support, the plastic may not flow into these features correctly and the part may be deformed or have imperfections.

To ensure that all features of your part are supported correctly, you should use simulation software to analyze the flow of the plastic material. This will allow you to identify any areas of the part where additional support is required. Additionally, you should consider using ribs or gussets to provide additional support to any overhangs or recesses.

Mistake #5: Poor Gate Location

The final mistake that engineers and designers commonly make when designing injection molded parts is not placing the gate in the correct location. The gate is the point at which the plastic material enters the mold cavity, and it is important to ensure that it is in the correct location to ensure that the part fills properly. If the gate is placed too close to a corner or in an area that is difficult to fill, it can result in incomplete filling or deformities in the part.

To ensure that your part has the correct gate location, you should use simulation software to analyze the flow of the plastic material. This will allow you to identify the best location for the gate and ensure that the part fills properly. Additionally, you should consider the size and shape of the gate; the gate should be designed to provide the necessary flow rate for the plastic material.

Conclusion

Injection molding is a powerful and versatile process for creating plastic parts, but it requires careful consideration of the important design factors. To ensure that your part design is successful, it’s important to avoid the five common mistakes discussed in this article. By following these guidelines, you can ensure that your part design is optimized for injection molding and will be successful.