The Extrusion Process

The extrusion process begins with the raw material or feedstock in a hopper where it is fed into the extruder by means of a screw press.  As the raw material is fed into the machine it is in turn heated to a more fluid state as it passes down the barrel of the extruder.  As the now fluid material is compressed it is pressed through a die and the extrudate is received.

Extrusion Dies

If you are looking to source your extruded product for the first time, creating the die for your product is the most difficult procedure.  Creating the die for an extrusion process is not as simple as it may seem.  As the material exits the die during the extrusion process it will morph and change shape due to something called die swell.  Because of this change in shape after exiting the die, every die must be made into a different shape that the actual desired end product.  A skilled die designer will be able to accurately predict what the final shape of the extrudate will be based on the temperature and shape of the die.  It is difficult to calculate the end shape, this is often done with a combination of experience and trial and error.

Defects in Extrusions

There are numerous ways that defects can appear in extrusions, most are related to high velocities through the die or uneven flows going through the die.  In extrusions it is important that the flow exiting the die is even and uniform.  If too much melt is exiting the center of the die and the edges are slow you will see defects in the final extrusion that make the profile a bamboo effect called “bambooing”.  If you are reaching too high of velocities as the melt leaves the die you will experience a defect known as melt fracture, this is the most common type of extrusion defect and causes the final extrusion to have a bumpy or uneven surface.

Using a skilled die designer and sourcing with an experienced extrusion manufacturer you can help ensure that your extrusion comes out as desired the first time and is ready for production.  Contract Auction is the perfect resource for both finding the right die designer for your specific project, as well as a qualified extrusion manufacturer.  Post your project now to quickly get your production underway.