A Guide to Injection Molding Tooling

Just like how the tooling used in thermoforming determines the success of the project, the same is true for injection molding. To achieve accuracy and precision, both to the design and from one part to the next, you need to choose the right materials and features to get the job done. However, injection molding tooling is much more complicated than the kind used to thermoform plastics and requires technical knowledge and experience. To help you better understand the process, our injection molding company in North Carolina is providing a closer look.

Understanding Injection Molding Tooling

While thermoforming tooling is a one-sided mold in which the plastic is clamped into place and pulled taut against the shape through vacuums and air pressure, injection molding is a completely different process. With injection molding, the thermoplastic is melted to a liquid state and forced into a mold using a high-pressure injection tool, allowing it to fill the crevices of the mold to achieve the desired shape. Once cool, the piece is ejected or released from the mold and moved on to finishing.

The tooling used is a two-part mold, the injection mold where the cavity is located, and the ejector mold. By closing the two, the part cavity is created which is filled with the melted plastic. Outside of the cavity, waterlines are strategically placed to cool the plastic and reduce warping and flaws in the end result. Inside the cavity, the melted plastic flows through a runner with a gate at the end to control the direction of the plastic. These runners and gates must be precisely placed to ensure an even share of plastic and steady, predictable cooling.

There is a second mold, called the ejector mold that allows the plastic component to exit. Once the plastic has molded and cooled, a clamping unit moves the ejector away from the injection while pins move the plastic away from the injection mold. The ejector mold has tapered walls that allow the plastic to smoothly eject and release from the mold and move onto the next phase of finishing.

Materials Used in Injection Molding Tooling

In order to tolerate the high pressure of the injection, a harder metal must be used. The most common materials are hardened steel, aluminum, or copper alloy, and while steel is the most expensive, they offer high durability compared to aluminum and copper alloy. Once the metal is chosen and the design is in place, the tooling is constructed through CNC machining or electrical discharge machining.

What Factors Affect Injection Molding Tooling Design?

When determining the tooling design and materials used to construct the mold, a team of engineers and designers work together to look at what is necessary. These factors include:

• The properties of the thermoplastic;
• Whether special tooling such as threading, slides, and lifters are necessary;
• Component size, thickness, and tolerances that may need a higher quality of tooling material;
• Even cooling for gate and vent locations;
• The pressure of injection needed to fill the cavity;

Before the final tooling is designed and constructed, there are preliminary design models and prototyping that are reviewed and approved.

Call Advanced Plastiform, Inc. for a Free Quote on Injection Molded Plastics

If you need custom injection molded plastics, reach out to us today. We have an experienced design, engineering, and manufacturing team to ensure you get highly precise and accurate plastics with low per-unit pricing and a fast turnaround time. We work with industries and companies across the Southeast and Mid-Atlantic region, including North Carolina, South Carolina,  Pennsylvania, Maryland, Tennessee, Georgia, and Virginia.