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Designing Extrusions for Plastic

What do I need to think about before designing a plastic extrusion?

Choice of Compound

The properties of your extrusion will vary depending on your choice of the compound, so you need to choose a compound that will give the appropriate performance requirements you need for your design.

The key points to bare in mind at this stage are;

  • Tolerances, to ensure the assembly of your final product is possible since some compounds are more prone to shrinkage than others
  • Impact & stress resistance, if your profile needs to endure prolonged pressure or damage without deteriorating  
  • Chemical & environmental resistance, especially if your profile is intended to be used underwater 

Click here for details on the properties of the most common compounds.


Thickness of Sides

The easier it is to extrude your design, the less costly the process will be. It is good practice to try and keep the wall thickness of your design constant as it’s easier to extrude. There will be certain situations where you may require varying thicknesses, for example, to guarantee the right strength. These variances can generally be accommodated but they will have an impact on the speed of extrusion and may possibly also affect the final surface finish.


Shapes & Symmetry

The more complex a shape is, the more difficult it is to extrude. Wherever you can, try to design simple shapes that are symmetrical with only gradual changes in the thickness of their sides.

You should also think about whether your design needs to be solid or hollow – that can also affect the ease of the extrusion process and the cost of the initial tooling. In certain situations, hollow shapes are easier to produce than solid ones.

You might also find that it’s more cost-effective to create two or more sections that can be assembled after the extrusion, instead of creating a single, complex extrusion.

Rounded corners are easier to extrude as the compound 'flows' through rounded corners much more readily. Where possible radius all internal and external corners.


Fabrication & Finishing

Decide on the details your extrusion requires. This can include added holes, bends, prints, mitres, adhesives, protective coats or any other alterations and additions needed for your profile to attain full functionality.

Please advise us if you require punched holes/slots in the profile, we may be able to undertake this during the extrusion process with no added cost other than tooling, otherwise we will work and quote on a job by job basis.



The cost of the final extrusion is a function of its weight and complexity along with the compound type required. We will advise and quote for a range of design considerations. Tooling for hollow profiles is typically more expensive than solid profiles but still offers great values when compared to alternative production methods.


In Addition

  • Stock holding & handling, since storing and shipping particularly long profiles can be difficult and costly, it is worth considering extruding two sections than can later be joined. 
  • Having CAD drawings and 3D models developed is important since it gives an opportunity to visualise and test the concept, as well as allows proper revisioning in the future.