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When designing a plastic extrusion, it's crucial to consider a range of factors that will impact the final product's quality, functionality, and cost-effectiveness. Extrusion is a process where plastic material is melted and shaped into a continuous profile, making it ideal for creating everything from simple tubes to complex profiles. However, the design process involves more than just sketching a shape. You need to think about material selection, as different plastics have varying strengths, flexibility, and heat resistance. Wall thickness consistency is another key factor; uneven walls can lead to weak spots and product failure. Additionally, the extrusion process itself must be optimised to ensure smooth production, considering factors like die design, cooling methods, and potential post-extrusion processes.
In this blog we will consider what you need to think about when it comes to designing a plastic extrusion.
Choice Of Compound
The properties of your extrusion will vary depending on your choice of compound; it is important to choose one that will give the appropriate performance requirements you need for your design.
Key points to consider:
- 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
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. Your chosen plastic extruder provider will be able to advise further and even before this stage, ensuring the design is right and producing a prototype will help even further.
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 as this 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 your plastic extruder if you require punched holes / slots in the profile. At BWC Profiles for example, we will look 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.
Cost
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 value when compared to alternative production methods.
- Stock holding & handling: since storing and shipping particularly long profiles can be difficult and costly, it is worth considering extruding two sections than can be joined at a later date
- Having CAD drawings and 3D models developed is important since it gives you and your plastic extruder provider an opportunity to visualise and test the concept, as well as allows proper revisions in the future
We hope our blog on factors to consider when designing extrusions for plastic has been useful. At BWC Profiles, we have a dedicated plastics facility with an experienced and knowledgeable team who can help thoroughly plan each step so you can avoid common pitfalls and create a high-quality product that meets both your specifications and industry standards. For more information, please contact us to discuss your plastic extrusion needs or take a look at our dedicated page here.