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Basic Explanation of an injection molding machine
Basic Explanation of an injection molding machine
A machine that forms shapes out of molten plastic or resin designed by engineers for a specific tool or machine parts by pressurized injection to a mold is called the injection molding machine.
Thermoplastic and thermosetting plastic materials are fed into a heated vessel where it is mixed and stirred and forcefully pressed into a nozzle into a formed cavity. The designed cavity is usually made of steel or aluminum and machined to precise dimensions to form the desired features of a part for another machine's requirements. This machine requirement could be from the smallest component up to whole body segments of vehicles.
Injection molding machines is composed of a hopper, where granulated material is poured down through gravity and is trapezoidal or conical in shape, an injection ram or an auger; also known as the screw type plunger, and a heating orifice. The setup is also called the presses, as they hold the molds attached to the machine.
The two main parts of the injection molding machine is the Injection unit and thee clamping unit. The clamping unit can vertically or horizontally fasten the molds. Most of the machines are clamped horizontally, while special processes have vertical usages like insert molding through the force of gravity. Fastening the molds could be done using manual clamps utilizing bolts to fasten the couple to the plates, hydraulic, and magnetic clamping for the molds to be held in place.
Injection molding machines are distinguished by the clamping force the machine can provide. The force can keep the mold sealed during the injection procedure that range from 5 tons to 6000 tons. The force for clamping is denoted by the designed area of the part to be formed. This calculated area of projection is multiplied by the clamp with a force of 2 to 8 tons per in2. Most products have an exposure of 4 to 5 tons/in2.
types of machines:
Injection molding machines are classified primarily by the type of driving systems they use: hydraulic,mechanical, electric, or hybrid. Hydraulic presses have historically been the only option available to molders until Nissei Plastic LTD introduced the premier all-electric injection molding machine in 1983.
About the Author
Roger van der Linden is owner of triple-c ltd that delivers rapid prototyping and plastic injection molded parts and author of the article Introduction to injection molding
Injection Molding Hydraulics - Reading Hydraulic Prints (excerpt)