Understanding Plastic Shrink Rates in Injection Molding
Injection molding is a popular process, used to create plastic parts and products. It involves injecting molten plastic into a mold and allowing it to cool and solidify, which results in the final product. There are many considerations that go into injection molding, and an often overlooked factor is plastic shrink rates. Here, we’ll delve into the concept of plastic shrink rates and explore why they matter.
Plastic Shrink Rates, Explained
Plastic shrink rates — also known as shrinkage — refer to the reduction in size or dimensions of a plastic part as it cools and solidifies after being injected into a mold. This phenomenon occurs because plastic materials undergo changes in volume during the cooling process. It’s crucial to understand and predict these shrink rates as it’s essential for designing molds and producing accurate and high-quality plastic parts.
Factors that Affect Shrinkage
Now that we understand what plastic shrinkage is, let’s dive into the factors that affect it.
Different types of plastic will give you different degrees of shrinkage. Thermoplastics like polypropylene may shrink less than thermosetting plastics like phenolic resin.
The temperature of the mold itself plays an important role in plastic shrinkage. A higher mold temperature will usually result in less shrinkage, while a lower mold temperature will produce more shrinkage.
The design of your part will produce varying levels of shrinkage. Thicker sections will shrink more than thin sections.
The amount of cooling time you give for your part has a huge impact on overall shrinkage. Rapid cooling will lead to higher shrinkage.
How to Manage Shrinkage Rates
Adequately managing plastic shrink rates is important to achieve the desired dimensions and tolerances for your plastic parts. These strategies can help you address shrinkage effectively:
Choosing the right plastic material with known shrinkage properties for your specific application is a fundamental step. Material data sheets typically provide information on shrink rates. It can also help to work with an experienced injection molding partner to choose your materials. They can help you pick the correct material for your operation.
Mold designers consider shrinkage when creating your mold. They may adjust the cavity size and shape to account for the expected shrinkage.
Mold Temperature Control
It’s imperative to control the mold temperature throughout the injection molding process. Heating or cooling systems can help manage shrinkage. Additionally, some molds have multiple temperature zones to control different parts of the mold simultaneously.
Adjusting injection parameters like speed and pressure can influence shrinkage. You may need to experiment and test to find the optimal settings for a particular material and part design.
You may need to add post-molding processes — such as annealing or stress relieving — to minimize or correct shrinkage-related issues.
Work with an Experienced Injection Molding Company
The best way to ensure proper shrinkage is to work with an experienced injection molding company like SEA-LECT Plastics. Founded in 1987, we are a premier provider of injection molding, injection molding tooling, and related services. We offer round-the-clock operations, a dedicated engineering team, and a global network of suppliers, which ensures we can take on your injection molding project.
Our 36,000 square-foot facility features 16 injection molding machines ranging from 33 to 600 tons. These state-of-the-art machines, coupled with our in-house tool and die shop, ensure we can meet your exact needs.
But why should you trust us over another injection molding supplier? We prioritize high-quality products and an enjoyable customer experience. That’s why we maintain an ISO 9001:2015 certification and regularly invite auditors to validate quality in real-time production. We’ve also worked to create a turnkey manufacturing process, allowing us to streamline the process and ensure quality for our customers.
Start Managing Shrink Rates Today
Ready to learn more about how we can help you manage your plastic shrink rates? Reach out to our team for an initial consultation.