plastic extrusion and custom molding

Plastic extrusion has become quite a popular activity in industries and even technical schools are offering courses to enable individuals to get into this career. One of the fastest growing careers in the world is plastic and rubber mould designing. Custom molding is one activity that all brands seem to desire. They want plastic bottles for their sodas in this form or the other. Brands want to sell the most stylish yet functional water bottles. There are others that want to set up the finest quality plastic and rubber pipes for industrial and even residential purposes. These are just some of the reasons why the career is continually growing in popularity.

What is extrusion?

So people are talking about this process over and ever but in all honesty very few know exactly what it is. Well, generally plastic extrusion is a process whereby plastic melted down and turned into a continuous form. This process is mainly used n the production of items such as pipes, tubing, wire insulation, railing, fencing and so much more. In other words the applicability of extrusion is so high and hence its popularity all over the world. At the most basic level the process involves heating and molding to produce a particular shape.

The process involves use of plastic resin. These are small plastic beads that are fed into the heated barrel of the extruder. The resin is pushed through the barrel by a rotating screw where a temperature of between 392 and 527 degrees Fahrenheit melts the resin. This temperature depends mainly on the polymer that has been used in the creation of the resin. In order to reduce the likelihood of overheating the resin, the heat is increased gradually from one side of the barrel towards the other one.
There is a screen at the front of the barrel which is used to filter out contaminants that might be present in the molten resin. Once the resin has passed through the screen it is sent through a die of particular shape. This gives the product its profile. The profile can be made continuously at whatever length the manufacturer fancies. The final stage is usually the cooling. This is done by use of a water bath. Normally plastic holds heat quite well and therefore cooling can take quite some time to complete. The water bath is usually sealed there is a vacuum that is employed to prevent the product from losing the shape as it cools.

Common types of extrusion

There are various types of plastic extrusion which produce various products. They include:

1. Blow film extrusion

This one is used in the making of things such as plastic shopping bags. The die in this case is normally an upright cylinder where the melted resin is poured.

2. Sheet extrusion

It is also called film extrusion and it is mainly employed in the making of plastic films and sheets. Instead of cooling by water bath, the sheets are cooled by being pulled through a series of about three pinch rollers. The rollers also determine the thickness of the final product in question.

3. Tubing extrusion

This method makes products like medical tubing and straws. The process is rather similar to the basic extrusion but at the die stage a pin is placed inside the die. The melted resin is then pushed into the die and it forms around the pin known as a mandrel.

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