Before we start off, let’s define what a plastic extrusion machine is. A plastic extrusion machine can be defined by understanding what plastic extrusion is.
The extruder’s job is to transform the solid plastic mass or feed stock into a melted form. To do this are two core extruder technologies, single and twin screw.
The single screw extruder is the most widely used technology for extrusion. It has the versatility to process a wide variety of polymer types and can be applied to all common extrusion processes.
The twin screw extruder technology is broken down further to include counter-rotating and co-rotating. The counter-rotating twin screw extruder uses two screws which intermesh and rotate opposite to one another. The co-rotating twin uses two screws which intermesh and rotate in the same direction.
Whether a single screw or twin they are used to accomplish a single purpose – to transform a solid mass into a melt. This transformation process is the beginning of the extrusion process and has an immense impact on the overall process.
The extruder is often called the heart of the extrusion process. Taking this a step further, the extruder screw is frequently called the heart of the extruder. Why is the extruder screw the heart of the extruder or the extrusion process itself? Because if the extruder screw does not perform at an optimum level the rest of extrusion process will suffer. This is why the screw has been the most studied component of the extrusion process outside of polymer chemistry.
Advantages of a Plastic Extrusion Machine Here are some of the benefits you achieve when you use a plastic extrusion machine:
You will have a high output level of production.
When you compare with other types of molding machines, a plastic extrusion machine is cheaper. This is regarding operations and the initial cost of purchasing the machine.
A plastic extrusion machine is flexible thereby you can change the production of your product depending on your needs.
A plastic extrusion machine allows for the thorough melting of the resins thereby you have uniform melt. Also, the availability of the screens ensures that you have a smooth melt.
A plastic extrusion machine has a short lead time of production ensuring continuity in production.
Disadvantages of a Plastic Extrusion Machine Some of the limitations you will experience when you are using this machine are:
Die swell results in size variance of the product. Since there are different causes of die swell, estimating the exact expansion degree is a challenge.
The result is that manufacturers have to do with significant levels of deviations.
Plastic extrusion machine limits the type of products you can make. For instance, in the making of a soft drink bottle, you have to allow for an opening for the cap which most plastic extrusion machine can’t.
Increase in pressure during extrusion may affect the quality of the product. This is because the polymer may not have melt completely by the time it exits the extruder.
What is Plastic Extrusion?
In a basic technical definition, it is the transformation of solid plastic mass converted into a shape that can be used as produced or converted into usable products.
Plastic extrusion is used in the three primary processes of producing a plastic part – extrusion, injection molding and blow molding. There is a uniqueness to each primary process.
Here we will focus on extrusion. Extrusion is a continuous process of converting a solid plastic mass, pellet or powder into a melted form where it is pushed through a die into a shape. This shape is then moved through various secondary operations where it is cooled then cut, coiled or experiences a variety of other possible operations. Extrusion can be broken into specific sub-processes which are sheet, blown or cast film, profile, pipe or pelletizing. Outputs from these processes include:
Plastic sheet turned into drinking cups or food storage containers
Films used for grocery bags or to protect our food from harmful contamination while increasing its shelf life
Plastic pipe to safely deliver water to our homes without the worry of lead contamination or to clad the sides of our homes for an aesthetically pleasing low maintenance look
Each sub-process is unique requiring different dies, post extrusion or downstream equipment to produce the desired product. Regardless of the process, each sub process has a single component in common, an extruder.