Core Concepts in Injection Mold Tooling

Tooling is one of the essential processes in injection molding. It refers to the design and construction of custom molds that go into the cavity and are injected with molten resin or ceramics to create a part. For clients, it’s the most involved and important part of the process and requires careful attention.

In today’s article, Wunder-Mold experts explain essential aspects of the tooling process in detail and highlight important things to consider along the way. 

What is the tooling process?

In injection molding, the tool is also referred to as the die or mold and its design significantly impacts the quality of the final part. It consists of several key elements, including material selection, part line location, venting, gating, bubblers, runners, and more. Throughout these different stages of the tooling process, it’s important to consider the following aspects:

Material properties

First, it’s crucial to consider both the chemical and physical properties of the raw material. This can directly affect tool design, since it may be necessary to take into account different features depending on the type of ceramic or plastic, such as flow characteristics, shrinkage rate, and more. 

For example, if you’re using polypropylene (PP), an important characteristic to consider is its relatively high shrinkage rate. This means it’s necessary to design the mold slightly larger than what the part is required to be to compensate for this shrinkage that occurs while the material cools and solidifies. 

Wall thickness

Another important step is to carefully plan the wall thickness of the molded parts. If your application requires thicker walls, it may be necessary to design more robust tooling and have longer cycle times. On the other hand, thinner walls can be more delicate to handle. It’s essential to find an adequate balance between speed and strength. 

In addition, many applications require different thicknesses within the same part, which significantly affects the tooling. It’s essential to work closely with your manufacturers to plan where these thinner and thicker areas should be positioned and design an optimal mold. 

Material shrinkage

Whether you’re working with ceramic or plastic materials, they will shrink as they cool from a molten into a solid state. This shrinkage depends on the specific characteristics of the resin or ceramic powder and it’s crucial to take it into account when designing the tooling. Planning for how shrinkage can affect fit or function, adding material to account for it, and applying ribbing and other structural elements can help create the final part that matches your requirements. 

Proper cooling

It’s extremely important to design the tooling so that it ensures even and efficient cooling, allowing the parts to be ejected from it at the optimal time. There are several ways to make sure that mold facilitates proper cooling, including using materials that are good heat conductors, leaving sufficient space around the part, and incorporating cooling lines. Inefficient cooling can lead to defects, longer cycle times, and other problems. 

Ejection mechanisms

At the end of the process, parts need to be ejected from the tooling. This is where ejection pins and mechanisms play an important role as they push the parts out when they’re cooled and solidified. The number, size, and position of the pins will depend on a part’s design. However, their position should not impact the function or appearance of the final part. It’s essential to include these mechanisms in the initial design and test them to secure smooth part ejection. 

Prototyping

Creating and testing a prototype before starting a full run helps ensure the parts satisfy all requirements, verify the tooling design, and address any potential problems. While this step does involve added time, it helps save both time and money in the long run by detecting and solving issues early on.