The word extrusion is taken from the Latin word extrudere meaning (ex) out and (trudere) to push. In the extrusion process, a pellet or dry powder plastic is heated and forced through a die. The majority of extrusion is done by screws although ram extrusion is still used for UHMW powder specifically. The screws will melt and mix the material and force it out of the opening in the die. An extruder can either be single barrel or twin screw/double barrel equipment. The material being extruded determines what which extrusion technology is required. Double barrel extruders are primarily use for compounding in line of basic plastics with different plasticizers, fillers, colorants and other ingredients. Extrusion lends itself to make tube, rod, profiles, film or sheet plastic products in a variety of widths and thicknesses.
Extrusion is one of the primary ways machine stock shape plastics are made. Extrusion has several advantages:
-The high output (compared to other processes) offers lower material costs.
-Depending on the volume, there can be a greater variety in width and length options to maximize yields.
-Relatively low tooling costs.
Extrusion can have some disadvantages:
-Thickness limits for some materials.
-From a machining standpoint, the material may have a higher level of stress in the sheet making secondary or post manufacturing annealing necessary to help relieve stress so the stock shape is more machinable.
- Close tolerance shapes are difficult to achieve.
-Limited to shapes of uniform cross sections (along the length).
Extrusion is one of the most common ways to produce plastic stock shapes. When done by a reputable extruder, using the highest quality materials the machining of these stock shapes can be a successful part of any job shops business. To find the widest selection of quality stock shapes for machining, just click here.