6 Ways To Reduce Costs for Injection Molded Parts

Are you aiming to reduce costs for your injection-molded parts while maintaining their quality and functionality? Although the injection molding process can appear more expensive than CNC machining and 3D printing, there are ways to optimize your designs and achieve substantial savings. Here are six design considerations for injection molding that can help you cut costs.

1. Reduce Material Cost for Injection Molded Parts

The cost of plastic materials is undeniably on the rise. By minimizing the material used in a part without compromising its functionality, you can lower part costs and reduce injection time, which in turn decreases injection costs. To achieve this, consider the following strategies:

Enhance part strength by incorporating reinforcements instead of thickening the walls.

Remove excess material from the thicker areas of the part.

Additionally, explore alternative materials. Numerous plastics provide similar strength and functionality and are easier to mold, resulting in reduced part costs. By carefully selecting substitute materials without sacrificing quality, manufacturers can achieve further cost savings.

2. Avoid the Overly Stringent Tolerance for Part Design

The more stringent the tolerances for a plastic part, the higher the requirements for mold precision, mold cavities, the injection molding process, and inspection. Consequently, this leads to increased costs for plastic parts. Product developers should understand the significant cost implications of tighter tolerances on both plastic components and mold production. It is advisable to optimize part design to avoid unnecessarily strict tolerances while ensuring the parts' functionality.

To prevent overly tight tolerances in part design, consider these measures:

Use plastics with low shrinkage rates for applications requiring high dimensional accuracy.

Avoid imposing tight tolerance requirements on mating surfaces such as mold cavities, inserts, and slides, as they may introduce additional alignment errors.

Refrain from applying tighter tolerances in areas prone to warping. Instead, add reinforcements, like ribs, to mitigate warping.

3. Use Snap-Fit for Fixing Instead of Screws and other Fasteners

Methods for securing plastic parts include snap-fit, screws, thermal fusion, and ultrasonic welding. Among these, snap-fit is the most cost-effective, offering quick assembly and disassembly. Utilizing snap-fit can reduce part costs while still meeting the necessary assembly and functional requirements of the product.

4. Avoid the Unnecessary Features

Undercuts are often unnecessary features in injection molded parts that complicate mold ejection. These include openings and protrusions on the upper side in the mold's opening direction. Creating undercuts typically requires side-action mechanisms like angled pins and slides, which add to mold complexity and cost. To reduce mold expenses, it's essential to design parts without undercuts. Consider these strategies:

Eliminate external undercuts by redesigning the parting surface, as illustrated in the figure below.

Modify part features to avoid undercuts. Many undercut features can be removed through optimized design, thus eliminating the need for side-action mechanisms and reducing mold costs.

5. Be Careful with the Decorative Features

For the cosmetic appearance and decorative features of the parts, including any text or symbols, it is recommended to have them protrude outward. During mold processing, these features should be recessed, which simplifies machining and helps reduce injection molding costs.

6. Choose Overmolding

Finally, consider the option of using overmolding. Liquid silicone rubber molding is more cost-effective compared to aluminum or steel molds. This process also allows for the easy creation of complex structures like undercuts. However, it's important to consult an engineering expert to determine if this process is suitable for your parts, considering the quantities and specific requirements.