5 Common Mistakes in Custom Extrusion Design and How to Avoid Them

Custom plastic extrusion offers incredible flexibility, but successful outcomes depend heavily on smart design decisions early in the process. Even small oversights can lead to production challenges, increased costs, or performance issues down the line. 

Understanding the most common extrusion design mistakes and how to avoid them helps ensure smoother manufacturing and better long-term results.

1. Inconsistent Wall Thickness

One of the most frequent design mistakes is uneven wall thickness within a profile. Variations in thickness can disrupt material flow, cause uneven cooling, and lead to warping or dimensional instability.

How to avoid it.

Aim for uniform wall thickness whenever possible. If variations are required for strength or function, keep transitions gradual and consult with your extrusion partner to ensure tooling and processing can accommodate the design.

2. Over-Engineering the Profile

Designers sometimes add unnecessary material, reinforcements, or complex features “just to be safe.” While this may seem like a way to increase durability, it often results in higher material costs, heavier parts, and longer cycle times without meaningful performance gains.

How to avoid it.

Focus on performance requirements rather than assumptions. Strategic use of ribs, internal supports, or geometry optimization can provide strength without excessive material usage.

3. Ignoring Material Behavior

Not all plastics behave the same during extrusion or in real-world applications. Overlooking factors like thermal expansion, flexibility, chemical resistance, or UV exposure can lead to premature failure or poor performance.

How to avoid it.

Select materials based on the actual operating environment and performance needs. Consider temperature ranges, mechanical stress, environmental exposure, and expected lifespan when choosing resins and additives.

4. Designing Without Manufacturing Input

Designs created without early input from the extruder often include features that are difficult, inefficient, or costly to produce. Tight tolerances, sharp corners, or complex internal geometries can create tooling challenges and increase scrap rates.

How to avoid it.

Collaborate with your extrusion partner early in the design phase. Experienced extruders can suggest design modifications that improve manufacturability while preserving function and appearance.

5. Overlooking Assembly and End-Use Conditions

A profile that looks good on paper may not perform well in real-world assembly or usage. Neglecting factors like fit, fastening methods, movement, or long-term wear can result in installation issues or premature failure.

How to avoid it.

Design with the full lifecycle in mind–from installation and use to maintenance and replacement. Consider how the extrusion interfaces with other components and how it will behave over time.

Designing for Success

Avoiding these common mistakes requires a balanced approach that considers material science, manufacturing realities, and real-world performance. Custom extrusion is most successful when design and production work hand in hand from the beginning.

By focusing on consistency, material efficiency, and collaboration, manufacturers can create extruded profiles that are easier to produce, more cost-effective, and built to perform reliably over the long term. Smart design choices not only prevent costly revisions–they help ensure that every extrusion delivers lasting value.

Custom Extrusion with Inplex

Looking for quality custom extrusion products and services? Inplex is one of the leading custom extrusion services in the US and has almost 60 years of experience. We pride ourselves on our ability to put the right talent and technology in place to perform the best possible job for our clients.

We own a 42,000 sq. ft. facility in Naperville, Illinois, that is temperature-controlled and features an environmentally friendly closed-loop water cooling system. If you have specific needs or questions, don’t hesitate to contact us!