What is Extrusion?
Plastic extrusion is a process through which raw plastic materials are melted and formed in different shapes. The process involves specially designed extruders that help the raw plastic to melt down and form a shape through various stages of extrusion process. In heavy industries where long length plastic tubes and profiles are needed, extrusion helps in creating them.
Plastic Extrusion Process:
As mentioned the process involves melting of raw plastic materials and then through a die, formation of the same as required by cooling it down in the extruder. There are few steps through which this process is performed. The steps are as follows:
- Step 1: The raw plastic material such as powder, granules and pellets are placed in the hopper in the extruder.
- Step 2: The raw materials slowly starts travelling from the hopper to the barrel attached with it. While it is running from hopper, gradually the materials start melting down and plastic extrusion process starts.
- Step 3: There are screws installed inside the barrel. These screws help the materials to melt down further. The melted material travels through the rear portion of the barrel towards the front.
- Step 4: There are various temperatures provided into the barrel for melting process. When the run starts the temperature remains little lower. Gradually with the help of multiple Proportion Integral Derivative controllers the temperature increases.
- Step 5: The gradual increase in temperature in plastic extrusion is done to avoid overheating of the barrel. It is seen that the desired temperature is always more than the actual temperature set into the barrel.
- Step 6: Slowly the melted material leaves the screw and create a pressure on the breaker plate that is installed in the front portion of the barrel.
- Step 7: The final step is to enter in the die. The molten plastic material, after running through the breaker plate travels to the die. This is the final place where the melted raw plastic gets the formation and creates profiles.
- Step 8: Finally the material or the created profiles are cooled down by running water. The extruders after the die process usually runs through cold water to cool down the products. The plastic extrusion process with this step is finished.
Things to know while extrusion process: The extrusion process is done carefully to avoid many adversities.
- The first thing that can causes adverse effect is overheating. While running the process the extruder must not be overheated. This can spoil the process or harm the extruder. To avoid this, the heat is spread over the barrel.
- Secondly, the process is continuous. So it is inevitable that there will be multiple profiles are created after the process. If it is plastic tube then same profiles can be created multiple times.
- Thirdly, within the barrel, the screws help the melted plastic to leave the contamination. Once the molten plastic starts roaming towards the breakers plate, it leaves any contaminations present in the raw molten plastic and makes a better profile.
- There is a Screw Driver Motor present in the rear portion of the barrel. This helps the screw to move accordingly during the plastic extrusion process.
- There are diverse patterns of dies in the extruders. Dies such as sheet/film, blown, tubing e.t.c are the common and most popular types of dies used in extruders.
Extrusion is very much helpful for creating continuous profiles. Not only continuous but it can produce longer tubes and sometimes rollers as well. These finished products are highly in demand in industrial activities. Also the extrusion can produce pipes with rubber seal.