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Injection Molder and Molding Machines

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Injection molder or injection molding machine is a machine for producing plastic molded parts by molding process. It has 2 main parts, an injection unit and a clamping unit.

Injection molder

An injection molder have 2 methods of fastening the mold -horizontal or vertical. Most injection molder are horizontally oriented because molded parts can easily be removed after ejection by leveraging gravity -the molded parts will just fall down into the container below. Vertical injection molders are used for insert molding applications because inserts are inserted into the core side of the mold before molding.

There are also manual injection molder for hobbyists. It is simple in consruction and does require manual force to inject the resin. An example of such machine is from Galomb, Inc. They make Benchtop injection molder.

Types of injection molding machines

Injection machines are classified mainly by the type of system that drives them: Hydraulic, electric, or hybrid.

Hydraulic injection machines uses ram system for its clamping mechanism. This type of machine is used by majority of molding companies.

Electric injection machines are driven by motors. Unlike the hydraulic machines, which continously pump hydraulics to the cylinder throughout the whole molding cycle, an electric machine only makes use of energy during closing and openning of the clamping unit. It uses toggle system for its clamping mechanism in order to build up tonnage. It is also faster, quieter, and have higher accuracy, but it is also known to be more expensive. The first maker of electric injection machine is Nissei Plastic Industrial Co., LTD.

What is Injection Molding

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Injection molding is an economical and very efficient method of producing injection molded parts. It can produce millions of parts with exactly the same shape, dimension, and quality. Some examples of injection molded parts are the mobile phones, mouse, keyboard, and many components found inside the automobile.

What is an injection mold?

An injection mold is a device made of metal to produce a plastic product faster, less expensive, and more consistent. A comprehensive reference about injection molds can be found in Injection Mold Design Engineering. There are also Injection Molds 130 Proven Designs for your design reference.

How does injection molding works?

Just heat the resin until it melts then force it into the cool mold. Allow it to solidify. Open the mold then take off the molded part.

That’s it!

As the molten resin is being injected into the mold, it enters the mold opening called the sprue. From the sprue this molten material will then be distributed to the runners then it will be fored into the gate and then into the cavity. The cavity must be filled precisely to avoid short shots but it must not be over packed (over packing is forcing more than enough pressure to the resin and it can damage the mold). The molten resin will stay in the cavity for 30 seconds to 1 minute or more until it cools down and solidify. When the resin solidify a molded part is formed. The mold will open and then the molded part will be ejected. The mold closes and its ready for another shot.

Why is an injection mold expensive?

Injection molds are made up of special, high quality steels that have a good machinability property. Some standard mold components such as springs, bolts, and limit switch are prefabricated and costs lower.

assembled-base

Most standard components such as ejector pins, ejector sleeves, sprue bushings, and leader components are not prefabricated which mean they will only be manufactured when you order them. They are not mass produced thus they are expensive. The cavity and core are mold components which make the mold really expensive. It involves careful design engineering and processing. Most of the tools used in making these components are very expensive.