The extrusion process produces a very simple continous product with a very sinple X-section. Simple products made of simple extrusions include:

• picture frames
• door tracks
• pipes and tubing
• film
• wire/insulation
• bumbers
• seals
  ...etc.

The process

The plastic material is basically fed through the transport section onto the infinitly rotating screw via the hopper or feeder. The extruder which converts the plastic granules into the homogenous melt is quite similar to the one used in injection molding. The plastic is heated slowly as it is moved and pressed forward towards the die. The melt is forced and compressed through the die. Once cooled with either water or other coolants, the extrusion is sized and cut to desired length.

Even if the cost of molds/dies is relatively low, secondary operations will add to the costs of plastic extrusions such as cutting to size, trimming, drilling, routing, embossing, etc.

Profiles

Bayer USA INC classifies extruded profiles as such:

• Tubular profiles have even wall thickness. Rounded corners if non circular.
• Hollow profiles with compartments are completly inclosed and can have different wall thicknesses.
• Hollow profiles with compartments and lugs are similar to the above yet have ribs or flanges.
• Solid profiles have no compartments and can be of any X-section.
• Composite profiles are made of several materials, or of several sections or differen colored materials.

Design thoughts and considerations:

• Try to keep the wall thickness uniform in the extrusion
• Avoid complex X-sections and especially hollow shapes within another hollow hence avoiding weld lines.
• Give generous radii to improve flow and to reduce stress.