If you work in the industrial manufacturing industry, you’ve probably heard of injection molding before. Injection molding is a unique manufacturing process for producing plastic injection molds from both thermoplastic and thermosetting plastic materials. During this procedure, materials are fed into a heated barrel, mixed, and forced into a mold cavity. When the mold cools and hardens to the configuration of the mold cavity. Once the part has been designed, often by an industrial engineer, the molds are then manufactured by an injection mold company, where it is then assigned to a mold maker or toolmaker.
More often than not, injection molds are constructed using either steel or aluminum materials. With the recent advances in modern technology, these molds are precision-machined to form the features of the desired parts. This type of molding process is used for a variety of parts in the manufacturing industry, from the smallest metal component to the entire side panel of automobiles, you can find injection molding everywhere.
A Brief History Of Injection Molded Parts
Have you ever wondered how injection molded parts came to be? The earliest record of this manufacturing process dates back to 1868. During this time, a billiard ball maker named John Wesley Hyatt came up with a way to make billiard balls by injecting celluloid into a mould. It wasn’t until 1987 that Hyatt and his brother patented the very first injection molding machine. Due to the resources that were available at the time, this machine was relatively simple, and featured a basic plunger that injected the plastic into a mold through a heated cylinder. As years went on, the industry continued to progress with plastic molded injections of collar stays, buttons, and hair combs. In the 1940s, the concept of injection molded products grew in popularity. This is likely because World War II created a large demand for inexpensive, mass-produced products.
The manufacturing industry saw another improvement in 1946 when a man named James Hendry constructed the very first screw injection molding machine. This machine revolutionized the plastics industry with an auger design that would eventually replace Hyatt’s plunger. In Hendry’s injection molding machine, the auger was placed inside the cylinder, which would mix the injection molded materials before they were pushed forward into the mould. This was a major achievement, as it allowed colored plastic or recycled plastic to be mixed thoroughly before being injected. Today, screw injection molding machines account for 95% of all injection machine companies.
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Injection Mold Applications
As you may have guessed, plastic injection molding is the preferred process for manufacturing plastic parts across the globe. Injection molds can be used to create a variety of products, from containers and automotive parts to electronics and pocket combs, injection molds can be found virtually everywhere. The injection process is ideal for those who want to produce a high volume of plastic parts, because multi-cavity injection molds can be created. There are many advantages to using injection molds, and some of them include:
- A wide range of material selection
- Low labor costs
- Minimal scrap losses
- High tolerances
Equipment Used in Injection Molds
Injection Mold Machinery
During the injection molding process, an injection molding machine, or press, must be used. The molds are tightly clamped to the platen of the machine, where the plastic is then injected to create an injection mold. Most presses are rated by tonnage, which is the calculation of the clamping force that the machine can exert. This is the force that is used to keep the mold closed during the injection molding process. Tonnage can often vary from less than five tons to 600 tons.
These days, electric presses are taking over the old hydraulic injection molding machines. Most manufacturing companies prefer electric presses because they offer 80% less energy consumption and nearly 100% repeatability. It’s important to note that the cost of an electric molding machine is normally 30% higher than a hydraulic press.
The Mold Itself
Mold or die are the common terms used to describe the tooling used in plastic injection molding. In the past, injection molds were very expensive to manufacture, and they were only used when mass production was needed. Most molds are constructed from hardened steel, aluminum, pre-hardened steel, and beryllium-copper alloy. While steel molds generally cost more to construct, they offer a longer lifespan. Pre-hardened steel injection molds tend to be less wear resistant and they are used for lower volume requirements or larger components.
The Injection Molding Process
An injection molding machine consists of two main parts: the injection unit and the clamping unit. The six main steps of the injection molding process are as follows:
- Clamping – The clamp unit consists of metal plates or platen. The initial process begins with the mould being clamped together under pressure. This accommodates the injection and cooling process.
- Injection – This is when the molten thermoplastic material is injected under pressure into the mould through either or screw or ramming device.
- Dwelling – Once the molten plastic has been injected into the mold, more pressure is exerted to make sure all of the mould’s spaces and cavities are filled.
- Cooling – During the cooling process, the plastic is left to cool and solidify within the mould.
- Opening – The movable platen is separated from the fixed platen to separate the new mould.
- Ejection – Completed by the use of rods, a plate, or an air blast, the plastic component is completely removed from the mould.
United Global Sourcing
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