Explaining Injection Mold Components

How Does Injection Molding Work?

The medical device injection molding process involves injecting raw materials, such as plastic, into mold cavities to develop high-quality medical device components. Not only does injection molding produce plastic injection parts quickly, with the injection cycle taking only seconds, but it also allows for improved ergonomics, reduced weight, and increased functionality.

Injection Mold Components

Below are the different injection mold components and how they work:

Hopper

The hopper is a crucial component in the injection molding process. It’s where the plastic material is poured before the molding begins. The hopper keeps moisture away from the plastic and has tiny magnets to prevent any pesky metallic particles from sneaking in. Once the plastic material is securely in the hopper, it makes its way into the barrel.

Barrel

The barrel plays a crucial role in the injection molding process. As the plastic material enters the barrel, it’s heated into a molten state, ready to flow through the barrel. As the plastic material travels through the barrel, a screw inside injects it into molds or cavities in the clamping unit. This allows the plastic to take on different shapes and patterns.

Screw Motion or Reciprocating Screw

The reciprocating screw, an injection mold component introduced in the 1950s, has revolutionized the process ever since.

This innovative design ensures even distribution of heat throughout the plastic mass, thanks to its continuous mixing action. This not only helps maintain the temperature, but also removes any previous colors or materials from the machine, resulting in a high-quality device. What sets the reciprocating screw apart is its ability to provide intense heat to the plastic. As the screw diameter decreases toward the tip, the plastic pellets are pulled along the flights, compressed, and cut. This process creates friction that generates the perfect temperature for the plastic to be molded without any defects.

Clamping Unit

The clamping unit is responsible for opening and closing the injection mold, as well as ejecting the molded products. There are two main types of clamping systems: hydraulic and toggle.

When the machine is ready to inject plastic into the mold, the clamping unit closes the two large plates that hold the mold. This allows the plastic to flow into the cavity and create the desired part. Once the plastic has cooled and solidified, the clamping unit opens the mold and the part is collected in a bin. In addition to the hydraulic or toggle system, the clamping unit also includes machine ejectors, a movable platen, a stationary platen, and tie bars. These components all work together to ensure a smooth and efficient injection molding process.

Injection Unit

The injection unit is a central component of injection molding machines. It’s responsible for melting the raw material and guiding it into the mold.

The injection unit consists of the hopper, barrel, and screw. First, the polymer pellets are dried and placed in the hopper. Then, they are mixed with coloring pigment or other reinforcing additives. Next, the pellets are fed into the barrel, where they are heated, mixed, and moved towards the mold using the screw motion. The screw and barrel have the same geometry, optimized to build up pressure and melt the material.

Extraction Pins or Ejector Pins

Ejector pins are an injection mold component that’s part of the ejection system. Injection molds consist of two parts, A and B sides. Once the melted material has cooled, the mold is opened and the A-side is lifted, leaving behind the formed part and the B-side. Ejector pins are located on the B-side and are responsible for pushing the formed part out of the mold.

Nozzle

Nozzles are a critical part of the injection molding process, located at the bottom of the machine’s ejector system. They play a crucial role in pushing melted plastic from the barrel into the mold. Nozzle filters also reduce clogging from foreign materials or contamination in the melted plastic. This results in less downtime and smoother operations. Mixing nozzles are another incredible innovation, improving the dispersion and mixing of additives, leading to better quality molded parts and cost savings.

Split Molds

Split molds, a type of injection mold component, divide a plastic part into two halves. The line that separates these halves is called a parting line. Here’s how they work: the mold cavity is formed by injecting the jaws diagonally on the nozzle side. When the mold opens with a pull tab, the jaws are moved diagonally to the outside, releasing the injection molded part. The jaws can also be guided on the ejector side. Using hydraulic cylinders, springs, or air, they’re moved during or after the mold opens.

Heaters

Injection molding machines use various types of heaters to maintain temperatures and melt molding materials, such as band heaters, coil/nozzle heaters, cartridge and strip heaters, and cloth heating jackets. Whether it’s heating molds and platens or melting molding material, injection molding heaters play a crucial role in the process.

Hydraulic Unit

Hydraulic units ensure smooth movement during the manufacturing process, preventing any irregularities that could compromise the quality of the final product. This hydraulic system controls various sub-circuits, such as the nozzle approach, injection of the plunger screw, and the closing of the mold. It also helps maintain a steady flow of plastic material into the mold, ensuring a seamless process.

Tooling maintenance is a crucial part of the injection molding process.

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Key Takeaways

Are you in need of a reliable, efficient mold manufacturing service for your medical devices?

Remington Medical offers top-of-the-line contract manufacturing solutions, including injection mold manufacturing. This process is ideal for producing large quantities of parts, making production more efficient and cost-effective. With injection molding, each part produced in the production line is identical to the one before it, every time. Our injection molding machines can also easily adjust to meet your specific needs, ensuring high-quality production throughout. Contact us today to learn more about our process.