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Polymer and Plastics Extrusion Equipment

Diamond America has over 20 years of experience in custom extruder design for polymers and plastics, including expert 3D modeling and Finite Element Analysis (FEA) software systems to optimize die and extruder performance and quality.

Plastics extrusion equipment is used for continuous, high-volume manufacture of a wide range of final products that have constant cross section, such as plastic pipes, frames, sheeting and films.

polymer and plastics extrusion equipment Manufacturer Diamond America

Critical factors in the design of polymer extrusion equipment

  1. Compression Ratio

The compression ratio is the ratio of the screw depth at the feed zone by the hopper, to its depth at the metering zone by the die.

Compression ratio varies greatly according to the polymer that is being processed. For example, where rigid PVC requires a compression ratio of around 2.3:1, polypropylene or a more slippery material requires a ratio of nearer 4:1.


The compression ratio is also impacted by the relationship of cross sectional areas at the screw feed and metering points. Finally, barrier designs, mixers, and variable lead screws affect not only the compression ratio, but the final screw output as well. The design of polymer extrusion equipment is indeed a very specialized process.


  1. Die Design

Due to the wide variety of products, ranging from plastic pipes to films, polymer extrusion die design is very diverse and complex and includes dies for:

  • Blown Film extrusion
  • Sheet and Film extrusion
  • Tubing extrusion
  • Over Jacketing extrusion
  • Co-extrusion
  • Extrusion Coating


Dies have to be carefully designed to handle the specific behavior of plastic extrusion melts. Polymers consist of long chains of molecules which become aligned and oriented in a single direction when forced through a die. On release, they tend to diverge randomly when no longer constrained, causing a phenomenon known as ‘die swell’.


Prevention of die swell must be built into the die design by:

  • Decreasing the extrusion rate
  • Increasing the melt temperature, at constant extrusion rate
  • Increasing the length of the die land
  • Increasing the draw down rate without affecting output
    (Draw down rate is the ratio of haul-off speed to natural extrusion speed)

Examples of polymer and plastic extrusion applications, materials and selection criteria:

Building & Construction industry
Rainwater Pipes, GuttersRigid PVCStrong, UV resistant, color fast
Soffits, FasciasCompact/foamed PVCUV resistant, color fast
Windows, DoorsRigid PVCAppearance, can be cut and welded
Door SealsCo-extrusionDual properties in one molded profile
Garden FencingPolystyrene/polyethyleneRecycled material, does not require painting
Light DiffusersAcrylicOptical properties
Conduit and Cable ProtectorsRigid PVCTough, good insulator, chemically stable
Cable HarnessesPTFE Filled PVCFlexible, resistant to chaffing
Household goods
Curtain TracksRigid PVCUV resistant, tough material, can be colored
Fridge SealsRubber, PVC and metalCan be magnetized
Drip Tubes, Catheter TubesPlastic compositesHigh integrity, reinforced, can be sterilized
Aerosol and Spray Dip TubesPolyethyleneTransparent, stable, chemically resistant
Gas Pipes, Water PipesPolyethyleneCorrosion resistant, good integrity
Soil PipesRigid PVCStrong, can be joined using solvent cements

Diamond America Extrusion Test Facility

Diamond America provides a fully equipped test facility for new product process and formulation testing for all applications.

The test laboratory boasts several table top extruders for small batch scaled production, as well as full scale twin feed and bulk extruders.

Experienced engineers are on hand to assist with extruder customization, die design, system controls and the selection of associated extrusion equipment.

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AKRON, OH 44301