Smart Design Strategies to Cut Injection Moulding Costs

Practical Design Tips to Cut Injection Moulding Costs

Cost reduction is a primary goal for anyone involved in manufacturing parts. One of the most effective ways to lower the cost of injection-molded parts is by increasing production volume.

This is because the upfront costs of designing and machining the mold are fixed. The higher the volume, the more cost-effective each individual part becomes. For example, at ZONZE, a single mold can produce up to 200,000 parts or more.

However, if your project only requires a small quantity of parts, don’t worry—ZONZE offers cost-effective molds for as few as 25 pieces, often completed within a few days after placing an order.

In addition to production volume, material selection plays a key role in cost management. Many plastics share similar strength and functionality, but some are inherently easier to mold, thereby reducing overall costs. When submitting your design, you can request material options, and we will help you choose the most suitable one for your needs.

Here are 11 design strategies to reduce your injection moulding costs.

1. Eliminate Undercuts

Undercuts introduce complexity into the part design and can, in some cases, make ejection difficult. If feasible, remove undercuts from the design. If removal isn’t possible due to functional requirements—such as a side action or sliding closure—consider alternative solutions, like using sliding actions and through-core inserts. Additionally, optimizing parting lines and draft angles can reduce mold complexity, lowering costs. Avoiding extra components in the mold will help prevent additional manufacturing costs, including longer cycle times and manual labor.

2. Remove Unnecessary Features

While aesthetic features like textured surfaces, molded part numbers, and logos can enhance the appearance, they often come with an additional cost. For non-critical applications, it’s best to omit these features. For example, military and aerospace components may require permanent part numbers, but for general purposes, simpler designs will reduce costs. Ensure that any text is factory-friendly (minimum 20 pt font), with depths between 0.010 to 0.015 inches. Furthermore, increasing draft angles can help with part ejection when necessary.

3. Utilize Core-Cavity Molding

For parts such as electronic housings, where deep wall cavities are required, using a core-cavity approach can be a more cost-effective solution. Instead of sinking cavities deep into the mold base, you can machine aluminum around the core to form the part. This technique simplifies mold construction, reduces tooling costs, and allows for smoother surface finishes, better venting, and improved injection performance.

4. Minimize Surface Finishes

While visually appealing parts are desirable, achieving high surface finishes such as sandblasting, EDM, or mold polishing can significantly increase production costs. Unless required for a specific application, avoid finishing beyond the PM-F0 level. Fine surface treatments, like SPI-A2 mirror finish, require extensive manual labor and diamond polishing. To save costs, specify which areas of the mold need polishing—polishing only the critical regions rather than the entire mold can reduce expenses.

5. Design Self-Mating Components

If your design involves components that fit together, consider designing them as self-mating parts. This approach eliminates the need for separate, complementary parts, resulting in reduced tooling costs. By designing parts that can assemble from any direction, you only need one mold, which saves both time and money in production.

6. Modify and Reuse Molds

When modifying existing molds, it’s typically easier to remove material than to add it. A “metal-safe” design accounts for this, ensuring that mold modifications are practical and cost-effective. Rather than purchasing a new mold for each iteration, plan to reuse molds. Start with the simplest design and gradually modify the mold for larger or more complex parts. This reusability can significantly reduce the overall cost of tool development.

7. Perform DFM (Design for Manufacturability) Analysis

ZONZE provides complimentary DFM (Design for Manufacturability) analysis with every injection molding quote. This analysis identifies potential issues, such as insufficient draft angles, unmoldable features, or geometries that may complicate production. By addressing these issues early, you can avoid costly design mistakes and improve manufacturability, ultimately reducing costs.

8. Use Multi-Cavity or Family Molds

For higher-volume production, multi-cavity molds are a great option. Depending on part size and geometry, you can achieve cost-effective mass production with molds configured to produce multiple parts per cycle. These molds, available in two, four, or even eight cavities, reduce part prices by improving throughput while spreading the fixed costs of the mold across more units.

Similarly, family molds allow multiple different parts to be produced in a single cycle, provided they are made from the same material and share similar sizes. This approach eliminates the need for separate molds for each part, saving both time and money.

9. Choose Low-Volume Production Options

If your production volume is low, consider utilizing low-volume production techniques. ZONZE can accommodate production runs starting from as few as 25 parts, which helps keep costs down while still maintaining quality.

10. Consider Part Size

The size of your parts will directly influence mold costs. Larger parts require larger molds, which increases both mold and part prices. Be mindful of part size in your design to ensure that it fits within the mold’s capabilities without exceeding space limitations. ZONZE’s maximum injection molding part size is 480 mm by 751 mm, with a maximum depth of 101 mm.

11. Incorporate Overmolding

Overmolding can be a useful strategy to reduce assembly costs. Although it may increase initial production costs, overmolding eliminates the need for secondary assembly processes, such as manual insertion of washers. This saves time and labor costs in the long run, making it a worthwhile investment for certain parts.

As always, feel free to reach out to ZONZE for any design-related questions or support at info@zonzescm.com.