Tooling Design for Injection Molding

Designing the tool and its various components (referred to as tooling) for complex plastic parts and products is a highly technical and often complex process. When the right tooling decisions are made, production is optimized, costs are reduced, and quality and customer satisfaction are improved.

In general, injection-molded products with tight tolerances require complex molds. This is where the rigor of the scientific molding process comes into play — Kaysun engineers rely on their in-depth knowledge and training about material behavior and tool design to construct the highest-quality tool for the project.

The Importance of Material Selection in Your Tooling Design

An important tooling design consideration is selecting the proper grade of steel. The correct steel hardness must be determined to maintain the proper balance between wear and toughness so tooling components don’t wear out prematurely. The tool is one of the most expensive parts of the injection molding process — we engineer them with the proInjection mold metals comparison for tool designper design and materials so they have the longest possible life with minimal maintenance. Some of the main factors to consider are:

  • the size of the production run
  • the complexity of the part
  • the finish quality needed
  • the material to be molded (some plastics are corrosive; others contain abrasive glass fibers)

The hardest metals, such as H13 steel, are best for high-volume, high-complexity parts. Softer metals, such as aluminum, can be sufficient for smaller runs and simpler parts. In general, the softer the metal, the easier and less expensive it is to machine. This diagram compares the expected tool life of aluminum, P20 carbon steel, and H13 hardened steel according to the size of the production run.

Qualifying the Tool and Refining Prior to Production

After considerable preparation regarding product design and process selection, the tool is constructed — a big step toward production. However, to ensure consistent and repeatable production of flawless molded parts, the tool must be challenged completely before it’s called into action. This is one of the most important jobs of the process engineer.

Our engineers love qualifying tools because it is a test of how well they have designed them. They push the tool relentlessly under realistic conditions (and sometimes beyond) to see where adjustments may be needed. Tool qualifying is a critical step in creating a highly efficient and low-cost production process — ensuring top quality and repeatability.

The Process of Scientifically Qualifying a Tool Infographic

In-House Design and Tool Adjustments

Injection molders rely on outside tool builders to custom-build the initial tool. Molds rarely arrive with perfect dimensions; typically, after the tool is qualified, adjustments are required to assure all design specifications are met. For most injection molders, this requires sending the mold out for final adjustments, which can take a month or more to complete. At Kaysun, we make most of these adjustments in-house and “fine tune” tools after initial sampling to improve the tool core/cavity geometry and achieve the desired dimensions.

The main goal of tool design is to create a product with highest possible manufacturability. That means a high-quality process that is simple and efficient, long-lasting, easy to operate and maintain, and that meets all customer specifications — all at the lowest possible cost.

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Tooling Design for Custom Injection Molding