The ABCs of Post-Extrusion Processes

Did you know that a wide variety of additional operations can be applied to plastic products as they emerge from dies in their extruded form? Approximately 65% of all plastics in use today pass through an extruder, and post-extrusion processes can be applied both inline and offline in a variety of ways. Here’s some basic information about post-extrusion processes to help provide an overview of what’s possible today at plastic extrusion facilities.


Inline or offline?

Some post-extrusion operations may be completed by devices added downstream of the extruder as part of the inline process. These devices may be standard devices, or they might be customized devices created for specific extrusions. Alternatively, post-extrusion processes can be performed offline by people and/or additional equipment at the extrusion facility.

What are some of the most common post-extrusion processes? Here’s a partial list:

  • Cutting – extrusions are cut to a specified length, either finished product length or for convenient shipping purposes.  Tighter tolerances can be achieved as well as angles or miters with an offline cut.  Fly cutters and Guillotines can be used to cut smoother or shorter lengths of extrusions very quickly.
  • Notching – an economical shearing and punching process used to make a notch by using punch tools. The purpose of this is to allow parts to be bent into an angle/corner or frame section.
  • Printing – printing numbers inline offers traceability options.  Identifiers such as websites, phone numbers, time and date, lot/batch, patent I.D. numbers and in some cases barcodes can be added to the parts.
  • Punching – holes/slots of assorted shapes and sizes can be punched in extruded parts for fasteners, venting and alignment.
  • Slitting – spaces can be sliced into plastic extruded parts.
  • Taping – magnetic tape, Velcro, foam and other types of tape, can be added to extruded parts.
  • Vacuum sizing – this process happens inline where the exterior of the part is suctioned to the water cooled forming tool.

Other post-extrusion processes gaining in popularity more recently are:

  1. The addition of liquid flavoring or fragrance. Liquid flavoring, which helps to repel and prevent animals from chewing on certain products or to add a pleasant fragrance, can be added to extrusions as a downstream post-extrusion process.
  2. As extrusions cure plasticizers are released and can affect adhesion of tape, adhesion promoters are applied to allow for good adhesion of tapes that need to be applied to parts.
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