5 Factors Affecting Plastic Injection Molding Cost

Due to its ability to create large volumes of the same part, plastic injection molding is a very popular manufacturing process. This technique can be employed for a variety of different plastics, which are melted by applying heat and pressure. The melted plastic is then injected into a mold to form the desired component.

Plastic injection molding costs can vary widely, and are often affected by the five factors discussed below.

1.Part Design

The more complex your part is, the more complex its mold must be. Complex, custom plastic injection molding parts are usually more expensive because they require more tooling than simple parts. Machining complex parts may require secondary EDM procedures for undercut features, in turn requiring more production time. Plus, larger parts require more material, which increases costs.

2.Part Material Used

The type of resin used also greatly affects plastic injection molding costs. Along with quantity of parts, additives, compounding, and molding temperatures, resin availability, grade, and color should all be considered when selecting a resin. Resin choice may also affect mold maintenance requirements, leading to higher costs, as is the case with abrasive resins.

Each type of thermoplastic requires different temperatures. Higher-temperature resins increase mold costs, as discussed below. Thermoplastics offering lower costs include polypropylene, polyethylene, and polystyrene, while higher temperatures and higher costs are often associated with liquid crystal polymers, polysulfone, and polyphenylene sulfides.

3.Mold Material Used

Various steels are available for mold creation, but the specific type required for a job will depend on the type of materials used for plastic injection molding. Higher-temperature thermoplastics necessitate steel with higher hardness, or molds plated with steel. Consider the mold maintenance required and the need for replacement molds when selecting mold materials.

Different mold materials offer different service lifespans. Molds with higher useful lifespans offer more value but are made of more durable steel, increasing the cost of the mold. When selecting a mold material, consider cycle time, surface finishes, and production volume, as all of these factors will impact the mold’s useful lifespan. Tool steel is typically selected for its resiliency and durability, though less expensive materials such as aluminum may be suitable for molds, especially when lower-production runs are required.

4.Volume and Cavities

The more cavities required to form your part, the longer the press time. Longer press times limit the ability to produce parts rapidly, increasing costs. Producing higher volumes of parts requiring numerous cavities will also involve higher production costs.

5.Mold Manufacturer Location

The location of your mold manufacturer will impact overall plastic injection molding costs based on the shipping and handling costs required to get the mold to the processing location. When using a mold manufacturer in China, for instance, consider the minimum wages of each province. Proximity to seaport will also affect transportation costs.

Choosing an offshore manufacturer for plastic injection molding can increase shipping and handling costs. If your parts are made entirely overseas, the cost required for your products to reach you may cancel out any savings from low production prices.

Planning a Plastic Injection Molding Project

Before undertaking a plastic injection molding project, consider the various factors that can affect the final cost of your parts. Smart design, optimal material choice, and careful manufacturer selection can greatly improve part quality while keeping costs in check.

Resources:

• Plastic Injection Molding 101 – Determining the Cost of a Mold | The Rodon Group
• 8 Factors that Affect Plastic Injection Molding Costs – Proto-Cast
• What is Plastic Injection Molding? – Romeo RIM
• The True Cost Of A Plastic Injection Mold – PM Plastics Co
• Everything You Need To Know About Injection Molding

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