Friday, 4 December 2020

Rule of Thumb for Plastic Parts: 4 Factors Impacting Plastic Part Performance

 


In this blog post, I present you another rule of thumb for your daily polymer engineering operations.

There are several factors which impact plastic part performance. Altogether, we can divide them into four major categories [1]:

- Material and materialselection: 45% of cases related to part failure [2], are due to wrong material selection, together with insufficient specifications.

- Component design: there are 10 basic design rules [3] which serving as a helper when designing for injection moulded products:

1. Wall thickness as thin as possible

2. Continuous wall thickness to prevent accumulation of mass

3. Corners and edges with radius

4. Ribs designed for moulding: 40-60% of wall thickness for ribs

5. Avoid plane and even surfaces

6. Use draft angels 

7. Avoid undercut sections

8. No more accurate machining as necessary

9. Check for possibilities of function integration

10. Past performance of design can be guarantee of future results

- Part processing and assembly: depending on the processing technique involved, it is important to take proper care of the material (e.g. drying), mould (e.g. temperatures), machine conditions (e.g. temperatures).

- Service conditions of the part: this is linked to the first point “material”. If the requirements are well explored, then specifications are properly set which in turn allows optimal material selection. If e.g. the continuous service temperature is too high, reduction of mechanical properties may occur, together with material degradation.  

The four categories are schematically shown in the above figure.

In case of a plastic part failure, several factors combined lead to failure and it is rare that a single factor leads to part failure.

Therefore, keeping all four categories in mind during part design will reduce part failure and allow you to get the best performance out of your part.

Thanks for reading and #findoutaboutplastics

Greetings, 

Herwig 

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Literature:

[1] Jeffrey A. Jansen: Finding Fault, applianceDESIGN, 2006

[2] David Wright: Failure of Plastics and Rubber Products, Rapra, 2001

[3] https://www.findoutaboutplastics.com/2018/04/plastics-part-design-10-holy-design.html


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