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Design Tip: Reduce Injection Moulding Costs

Views: 49     Author: Site Editor     Publish Time: 2024-03-20      Origin: Site


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Reduce the costs with these injection moulding design recommendations

Everyone wants to save money on manufacturing parts. But one of the simplest ways to reduce the cost of injection-molded parts is to increase the quantity of parts.

This is because the initial upfront costs of designing and machining the mold are fixed, and the lower the initial cost proportion, the more cost-effective it becomes. For example, at ZONZE, the same mold can produce up to 200k or more parts.

However, perhaps your production project only requires a few parts. Don't worry. ZONZE produces cost-effective molds for production quantities as low as 25 pieces, often completed within a few days after ordering.

In addition to unit cost, material considerations are also important. Many plastics have similar strength and functionality, but some plastics are inherently easier to mold, thereby reducing part costs. When you submit your design to ZONZE, you can request to try different materials, and we will recommend the most suitable one for you.


Here are 11 injection molding design considerations to reduce your manufacturing costs:

1.Eliminate undercuts.

2.Remove unnecessary features.

3.Use a core cavity approach.

4.Reduce surface finishes and appearances.

5.Design self-mating components.

6.Modify and reuse molds.

7.Pay attention to DFM analysis.

8.Use multi-cavity or family molds.

9.Choose low-volume production options.

10.Consider part size.

11.Use over-molding.


The undercut features complicate the part and, in some cases, make it difficult to eject. If possible, remove them. However, this may not be feasible, for example, if you need a side action or sliding closure. An alternative could be to use sliding actions and through-core inserts, or provide easier mold construction by altering parting lines and draft angles. This can reduce mold costs and avoid additional part manufacturing costs due to extra components in the mold. In addition to the increased manufacturing costs associated with manual loading inserts, this may also impact your part price due to longer cycle times and manual mold operations.

Unnecessary Features

Textured surfaces, molded part numbers, and company logos may look nice, but be prepared to pay a little extra for these and other non-critical features. Many aerospace and military applications require permanent part numbers. Use fonts suitable for the factory, maintain at least 20 pt., and keep depths between 0.010 to 0.015 inches. Additionally, if part ejection is an issue, be prepared to increase draft angles.

Core Cavity

If you need an electronic housing or similar box-shaped part, you can either sink the wall cavities deep into the mold base, requiring long tools to machine ribs into the mold, or you can machine aluminum around the core and mold the part around it. The latter method, known as core cavity, is a more cost-effective way of molding high-wall and ribbed surfaces. Better yet, this makes it easier to provide smooth surface finishes, adequate venting, improved injection, and can eliminate the need for excessively steep draft angles.



Nice-looking parts are great, but they often require sandblasting, EDM, or mold polishing to achieve higher levels of aesthetics. This increases production costs. Anything greater than PM-F0 surface finish requires some degree of manual work, up to SPI-A2 mirror finish using level 2 diamond polishing. Unless required for the job, such fine finishes should be avoided. One thing to consider is letting ZONZE know whether you need the entire mold polished or just a small area. Polishing only the entire side of the mold can save costs. When requesting custom finishes, simply send ZONZE a color-coded image of the critical areas and the desired finish level for each area.

Self-Mating Parts

Perhaps you're designing a snap-fit enclosure for some medical components, or two interlocking halves for a portable radio. Since it's possible to manufacture a single part, why make two complementary parts? Redesign so that the two halves can be assembled together from any direction, creating what's known as a "universal" part. Achieving the desired outcome only requires one mold, saving a lot on production costs.

Mould Mods

Removing metal from existing metal molds is relatively easy. However, adding metal can be challenging. From the perspective of the part, you can add plastic, but you can't take it away. Designs taking this into consideration are referred to as "metal-safe."

Some injection-molded parts undergo multiple iterations until a final feasible design emerges. Instead of purchasing a new mold with each modification, it's better to plan cleverly so that the same mold can be reused multiple times. Start with the smallest, most basic part design and mold as many parts as possible as needed, then rework the mold to include additional part features or larger, higher versions of the same part, and mold again. This reuse approach can save funds for tool development.

Mould-ability-DFM Analysis

Every injection-molded part quote from ZONZE comes with a complimentary Design for Manufacturability (DFM) analysis. This identifies potential areas of concern or opportunities for design improvement. Insufficient draft angles, "unmoldable" features, impossible geometries—these are just a few examples of areas in the part design that can and should be improved before clicking the "accept" button. Be sure to carefully review these suggestions and reach out to ZONZE for any design-related issues.

Multi-Cavity and Family Moulds

Perhaps you're aiming for larger volume parts? Depending on the size and geometry of the parts, you can still achieve high-volume production using aluminum molds with two-cavity, four-cavity, or eight-cavity configurations. This can lower your part prices, although it will impact your mold costs.

Do you have assembly parts? How about combining multiple molding projects into one? There's no reason to build a mold for each individual part, provided everything is made from the same plastic, each part is roughly the same size, and all can fit into the same cavity while still allowing the mold to function properly.

Part Size

Always consider the size range of the parts. In terms of molding, this means how big the part is and whether it can fit properly into the mold, while considering factors such as gates, runners, ejector pins, and all other factors required for the mold to work. ZONZE's current maximum part size for injection molding is 480 millimeters by 751 millimeters, with a maximum depth of 101 millimeters from the parting line. However, such large parts, in turn, require larger molds. This may have an impact on the cost of your mold and parts.


Finally, consider secondary molding options. Depending on the part, it may cost you more upfront, but could potentially save you money later. For instance, pre-molding washers onto the part might add to the cost initially, but could save costs later by avoiding manual installation of washers.

As always, feel free to contact ZONZE with any questions at info@zonzescm.com

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