What is extrusion Moulding?
The extrusion process is used to manufacture those parts, food containers, pipes, garden accessories etc. In this process, the thermoplastic raw material is added from the top hopper into the barrel. The other additives like colorants and UV inhibitors are in liquid or pellet form used and added into a hopper with resin. The manufacturing process is the same as plastic injection molding just this is the continuous process. The injection molding has a similar profile and is in the similar length and the finished product comes from the die and in this process, the fluid is extruded from dying.
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The material is fed from the hopper and it reaches to barrel and come in the contact with the screw. The screw is rotating and push the resin ahead into the barrel and heated to set temperature depends on a resin. In the process, a heating profile is set for a barrel to use three or more PID (proportional-integral-derivative) controlled heat zones that increase the temperature time to time of the barrel at the rear where the resin enters to the front. This setup melts plastic resin gradually as the resin flows ahead in the barrel and minimize the risk of overheating which is harmful to product quality.
At the front of the barrel, the resin leaves and moves ahead through the reinforced screen to remove contaminants. The breaker plate provides extra strength to screen as the pressure is very high around 5000 psi. After a pass from breaker plate, the resin enters into a die. The die gives the shape or profile to the final product, the products have the designed properly as the melted plastic flow through the cylindrical profile to get product’s shape. The flow must be continuous if it is not the product is produced with unwanted stress at some points. This problem cause warping above cooling. We can get any shape if it is a continuous profile.
The cooling process is must required and completed with a water bath. As the plastic is thermal insulated and it is not quickly cooled as steel. The plastic took more time to cool than steel. In the pipe, a sealed water bath is done in a controlled vacuum to keep the shape of the pipe from collapse. There is a set of cooling rollers is used in sheet extrusion process for cooling as it comes from the extruder. The plastic extruders are used for recycled plastic waste or raw material after sorting, cleaning and made it suitable for resin pallet used by the plastic industry.
There are various products are made with extrusion molding. The PVC water pipes are made with extrusion molding. The long cross-section shapes are made with extrusion molding. The insulation on the electrical wire is made with extrusion. The wire is stretch through the die and the insulation is then extruded.
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