Plastic Injection Molding, Explained
Plastic injection molding is a manufacturing process that injects molten plastic material into a mold cavity under high pressure. During this procedure, the plastic cools and solidifies inside the mold, creating a unique shape. The plastic injection molding process is widely relied upon in various industries because of its versatility, efficiency, and cost-effectiveness for the mass production of plastic parts. So, how does this method work and how exactly is it used? We’re diving into the specifics.
Steps in the Plastic Injection Molding Process
Injection molding has unique steps used to create cost-effective parts with even the smallest details.
The injection molding process starts with mold preparation. Even the slightest error can result in enormous problems, meaning that the mold needs to be perfect before it can enter the injection molding floor. During the mold preparation process, an engineer will design the mold using specialized computer software. They’ll also decide which type of plastic will be best for that particular product.
Once the mold has been designed and the material selected, the engineer will perform a Moldflow® analysis to ensure it works correctly. This analysis is a computerized simulation of the injection molding process, which can help the engineer understand if there are any tweaks that must be made to ensure a quality product.
Melting and Injection
The selected plastic resin is fed into a hopper, then melted in an injection molding machine. The machine contains a screw or plunger mechanism that continuously moves the molten plastic into a heated barrel. From there, the plastic will be allowed to reach a precise temperature and pressure determined by the engineer.
Once the molten plastic is ready, the injection unit pushes it into the mold cavity under high pressure. This pressure helps ensure that the mold is completely filled and the plastic material reaches all the intricate details of the mold.
After the mold is filled, the plastic material is allowed to cool and solidify inside the mold. The cooling time will differ for each part, as it depends on material type, part thickness, and design complexity. Once the plastic is solidified, the mold opens using mechanical or hydraulic systems. Ejector pins or plates will then push the part out of the mold cavity.
Factors Influencing the Plastic Injection Molding Process
The injection molding process may seem simple, but there are a lot of moving parts. If one of the following factors gets messed up, it could ruin an entire batch of product.
Temperature plays a crucial role in the injection molding process and influences various aspects of the process and properties of the final part. If the temperature is too high for the selected polymer, the resin will have decreased viscosity and higher flowability. It will also likely be degraded by the high temperatures. Lower melt temperatures will also affect the viscosity and fillability, which will result in a sub-par product.
If the pressure during the injection molding process is too high, you might encounter part deformation, flash, difficulty in mold release, tooling stress, and more. If the pressure is too low, you’ll likely have an incomplete fill, poor part quality, sinks and voids, or other issues that will affect the final product.
Cooling and Cycle Time
Sufficient cooling and cycle time is important to avoid issues like warping, shrinkage, or internal stresses. It will also help the ejection process, ensuring the part comes out of the mold in good condition.
Work with SEA-LECT Plastics for Your Injection Molding Needs
Need injection molding services for your brand? Turn to SEA-LECT Plastics. Founded in 1987, we are a premier provider of injection molding, injection molding tooling, and other related services. We maintain round-the-clock operations, a dedicated engineering team, and a global network of suppliers, which allows us to take on even the most challenging injection molding projects.
Our 36,000 square-foot facility features 16 injection molding machines ranging from 33 to 600 tons. With these state-of-the-art machines, our in-house tool and die shop, and Journeyman mold makers and apprentices, we can meet your exact needs.
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 operations and ensure quality for our customers.
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