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Injection molding machines
A world without plastics is hard to imagine: from pens, screw caps for bottles through garbage cans up to the bumper on your own car - there are plastic components in countless colors and shapes everywhere in daily life. These plastic parts are usually produced by injection molding. Injection molding is one of the so-called forming process, i.e. amorphous starting material is specifically brought to a special shape. The basis of injection-molded plastic parts is usually a plastic granule. The initially solid granules are heated and injected under pressure into a mold. This process is however much more complicated than it first sounds. Because, the finished product should correspond as precisely as possible to the relevant specifications regarding color, measurements and surface and yet be as much durable and high quality as possible. The first machine that operates on this principle was made in 1919 for the processing of soft cellulose acetate.
Machine bed, injection unit, clamping unit - How is the plastic injection molding machine built?
Injection molding machines generally consist of three units: the machine bed, the injection unit and clamping unit. The energy chain systems and highly flexible igus® cables can safeguard high holding times in all the units in the injection molding machine. Particularly in applications with heat generation and high dynamics, energy chains protect cables and hoses.
- energy chain, various cables like data cables and media cables in injection unit
- energy chain, different cables in "picker" unit
- Linear guides in sliding door of the clamping unit
- energy chain, various cables like data cables and media cables in the clamping unit
- Machine bed
- The machine bed is the base or the foundation of the machine. The switch cabinets are located here and a drive can also be integrated here depending on the machine. The other units that often can also move are located on the machine bed.
- The initial part of the original forming process takes place in the injection unit. The plastic is heated and liquefied. This takes place in the so-called screw.
- The clamping unit is the tool that determines the shape of the plastic product. It is called clamping unit, because the supply of the material from the injection unit can be closed and opened in the meantime. In the clamping unit are two mounting plates (one fixed and one moving) as well as a front plate. These plates are fixed vertically on one axis.
How does a plastic injection molding machine work?
First of all, the injection molding machine is set up, i.e. it is first filled with material (plastic granules), then equipped with the relevant tool. The tool determines which plastic product is produced and is replaceable. Therefore a injection molding machine can produce virtually any number of different parts.
When the machine runs, the screw rotates and thereby moves the plastic granules to the front of the machine, where a heater heats the material to liquid form (but this cannot be compared to the liquidity of water; the mass becomes more viscous). The movement in the screw builds up pressure. As soon as the pressure necessary for the production is reached, the material is injected into the tool in the clamping unit.
The tool is usually made of steel and is split in two. One part is installed on a fixed mounting plate, the other one on the moving mounting plate. Once both parts are joined, a hollow space is created inside, the so-called cavity. The material now enters this hollow space from the injection unit through a nozzle in the mounting plate. The pressure of the screw should completely fill the cavity. The injection speed is important here, for it influences how the material distributes in the tool; finally, no hollow spaces should be formed. Once the sealing point is reached, the clamping unit shuts off the flow of the material from the tool and the material starts to cool down in the tool. Afterwards, the tool is opened and the completed plastic parts can be removed. Besides the actual injection-molded part, the shape that the plastic part is meant to have in the end, there also exists the gate. That is the part which "projects", because the liquid material has to go into the tool through an opening. This projecting part is then removed by a gate picker.
Depending on the size of production and degree of automation, the injection molding machines can have widely varying dimensions. There are injection molding machines that have to be manually filled with granules as well as machines that suck the material from large tanks through pipe systems.
There are also machines where personnel remove the completed plastic parts from the tool and others which automatically take them with grippers and transport them further through conveyor systems.
The advantage of igus® for the injection molding machine
chainflex® control cables, servo cables and motor cables as well as hydraulic hoses are suitable for the energy supply system of the machine. In the clamping unit, for instance, a relatively frequent movement with a low cycle time occurs. The particular structure of the chainflex® cables with their strain-relief core, braiding in bundles and with high pressure extruded exterior jacket materials like PVC or TPE, are ideal for highly dynamic requirements.
The movements of the cables in the machine can be safely guided with igus® e-chain systems®. The strokes are mostly short, horizontal movements. To support these strokes, e-chains® can be used here. Depending on the nature of the machine, a different arrangement of the e-chain® is possible, for instance side-mounted or unsupported. The e-chains® have a long service life, so that high holding times can be expected.
The flexible structure and the easy installation makes it possible to adapt the filling of the e-chain® anytime, if something needs to be changed on the machine.
Diverse handling processes also exist for the plastic injection molding machine: The igus® e-chain systems® can also be used for material supply and the removal of the completed molded parts as well as the gate and tools.
The igus® plain bearing products can also be installed with drylin® linear guides. The safety doors of the clamping unit can for instance be guided with the lightweight, self-lubricating rail-carriage combination.
By the way, most igus® products are produced with injection molding machines.
Products for use in injection molding machines
Typical igus® products in injection molding machines