It turns out that plastic parts can also be very beautiful, but behind the beauty is hidden a major injection defect - internal stress 1 product design is not lacking in beauty, what is missing is the discovery of the beauty of the mind 2 light bullet method 3 to the engineer's enlightenment

Guide:

When the polarized light passes through a transparent plastic part with internal stress, it can produce a colorful stripe pattern on the plastic part, which looks very beautiful.

For our product design engineers, what causes the colorful graphics to be produced under the appearance of beauty---- injection molding internal stress, and can reduce the internal stress through product design methods, thereby improving the strength and quality of plastic parts!

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< h1 class= "pgc-h-arrow-right" > product design is not lacking in beauty, what is missing is the mind to discover beauty

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When polarized light passes through a transparent plastic part with internal stress, a colorful stripe pattern can be produced on the plastic part.

Forget the boring design of plastic parts, and enjoy a group of beautiful pictures together.

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What is the Light Bullet Method:

The photoelastic experimental method (referred to as the photoelastic method) is to use some transparent materials (such as polycarbonate PC, etc.) to produce optical anisotropy when deformed by force (including internal stress), and determine the principal stress difference according to the optical path difference of light with different polarization directions; the stress state and distribution in the model can be obtained by using the same color fringe image.

Light elastic method is an optical stress measurement method, carried out on the photoelastomer, first with a birefringent performance of transparent materials and the actual component shape similar to the model, after the force, to polarize the light through the model, due to the presence of stress, the temporary birefringence phenomenon of light is generated, and then through the analysis mirror after the interference fringe of light, displayed on the screen with light and dark fringes, according to it can be deduced the stress distribution within the component, so this method is particularly suitable for complex shape components.

Please see the video for the specific experimental process of the light projectile method. The video is wonderful and recommended to watch (starting from 20 seconds).

For plastic parts, the interpretation of the interference fringe diagram under polarized light is:

These interference fringes show stress distributions on the plastic part, including stress concentration areas and low stress areas. Areas with dense and cluttered interference fringes are stress concentration areas, while areas with a single interference fringe are low-stress or stress-free regions. The distance between the stripes represents a gradient of stress change, and the same color represents the uniform distribution of stress within that region.

There is truth in the picture.

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After looking at so many pictures, do you see some clues? From the perspective of plastic part design, what are the implications for engineers?

1. Stress concentration is easy to occur in sharp corners

2. Where the wall thickness changes sharply, stress concentration is easy to occur

3. Where the direction of plastic melt flow changes sharply, stress concentration is likely to occur

4. Stress concentration is easy to occur around the hole

5. Gate attachments are prone to stress concentration

6. From the surface of the plastic part, the weld mark is only an inconspicuous trace (or even no trace can be seen), and the light bullet method reveals the true face of the weld mark: the relationship between the two melt streams is like a song of ice and fire, and it is not fundamentally integrated. This results in a much lower strength in the weld mark area than in the main body.

The above enlightenment to engineers is that it is really necessary to fully follow the various design guidelines in the book "Product Design Guide for Manufacturing and Assembly" and the various design guidelines mentioned in this headline number, which is the wisdom of all old engineers. Don't wait until there is a quality problem in the product design, and it is too late to regret it.

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1. Disclaimer: Some of the pictures come from the Internet, are for learning purposes only, and are deleted for infringement.

2. Original works, welcome to reprint, plagiarism must be investigated. If you need to reprint, please contact the author, reprint requirements can not modify the content and retain the author and public headline number information at the end of the article.

About the Author:

Zhong Yuan, published the book "Product Design Guide for Manufacturing and Assembly" (DFMA) in 2011.

Cost-Oriented Product Design: The Cost-Reducing Approach to Design (DFC) will be published soon in 2020.

Welcome to the headline number of "Cost Reduction Design". "Cost Reduction Design" focuses on product design knowledge and concept sharing such as manufacturing and assembly product design (DFMA) and cost-oriented product design (DFC), helping engineers grow and improve their skills, and helping enterprises reduce product costs