The Plastic Extrusion Process
Britech Industries uses the highest quality nurdles, beads of resin, available to ensure
that our extruded parts are produced to fit our standards for quality and durability.
Plastic extruded parts are very sturdy capable of withstanding variations in temperature
and able to endure high pressure conditions. The extruding process requires very little
finishing of the completed parts, which further lowers the cost of production.
The nurdles are fed into a hopper that is mounted on the barrel of the extruder. They
are slowly fed into the barrel where they are heated and moved along to the die, which
is engineered with the shape of the part. Dies are made from high quality steel that can
handle the pressure of the plastic that is being forced through it. Extruding is a
continuous process where plastic beads are fed from the hopper and finished parts
come out from the die.
The barrel of the extruder is heated to melt the beads as they move toward the die,
which is similar to the process used for injection molding of plastic. Inside the extruder
barrel is a screw that turns at about 120 rpm. As the beads move along the barrel, the
temperature gradually rises allowing the beads to slowly melt to avoid overheating,
which could cause a degradation of the polymer.
As the heat in the barrel rises, so does the pressure and friction. In some cases, the
pressure and friction are sufficient to keep the polymer melted without the addition of
heat. Cooling fans or cooling jackets are available to maintain the temperature. When
the molten plastic leaves the extruder barrel, it is forced through the die that gives it the
shape and design of the finished part.
Once the part leaves the die, a cooling process is employed. This is a critical part of the
process since plastic is a thermal insulator and difficult to cool. The method used to cool
the extruded plastic is designed to keep it from collapsing or losing its shape. The type
of cooling process is very dependent on the type of part being processed, which can
vary from thin sheets to tubes.
