Plastic Extrusions

At Cellular Mouldings we commonly uses plastic chips or pellets for plastic extrusion. It is very common in adding colour to molten plastics in the extrusion application series.

The Process

This is where raw plastic materials are processed and formed through by melting.

The polymer resin is heated until it has become molten enough. In order for this to occur a combination of heating and shear heating elements are needed from the extrusion screw. The use of this screw is to ensure that it forces the resin through a die, this will enable to form the desired shape of the resin. As it is pulled through the die it will eventually be cooled and solidified. A caterpillar haul-off is used to provide tension while pulling extruded strands in order to be cut. Providing a consistent pull is needed so that it avoids distortion, poor quality and in-out of tolerance in the production outcomes. This is where the skill is.
The extrusions screw will play a driving force configuration which is entirely dependent on the application.

There are five possible zones in a thermoplastic screw.
Since the terminologies in the industry are not standardised
there are zones which are referred to by different names.

Certain screws have three zones. They are the following:

- Feed zone

- Melting zone

- Metering zone

The feed zone basically feeds the resin into the extruder. Usually its channel depth is the same all throughout. The melting zone is where the melting most of the polymer happens, in this section the channel depth gets smaller over the progression. The metering zone is the melting of the last particles and mixes into temperature and composition. Similar to the feed zone, the channel depth is constant throughout.

Additionally, there is also a second stage for a vented screw. There is a de-compression zone which is almost two thirds down of the screw. Deeper the channel will get and this relieves the pressure allowing any trapped gases from coming out of the vacuum. Eventually, there is the second phase metering zone. Similar to the metering zone mentioned earlier, the channel goes further with greater depth, re-pressurising the melt in order for it to go through the screen’s resistance as well as the die.

Each zone is equipped in the barrel wall for temperature control. For each zone, temperature is very important in terms of characteristics and the quality in which contributes to the final extrusion.

Here is a list on some of the typical plastic extrusion materials:

- Polyethylene (PE)

- Polypropylene, acetal, acrylic, nylon (polyamides)

- Polystyrene, polyvinyl chloride (PVC)

- Acrylonitrile butadiene styrene (ABS)

- Polycarbonate

Our services

Here at Cellular Mouldings we specialise and provide good quality Plastic Extrusions bespoke to your requirements. If you would like to discuss further about a project please get in touch with us through our contact page.