There's many articles on the web for plastic snap fit design. I'm sure some have equations you could plug into Excel for a parametric study. Not quite sure how yours works.
A snap fit means having the ability to distort enough to fit past an obstacle without permanently damaging the part.
In models that means an FEA to determine factors such as how much contact pressure there is, how much strain there is, and from the strain, determine if the material will break from the resulting stress. There's no formula for any of those.
That picture doesn't look like a good snap fit solution - it appears to require far too much distortion to deflect without breaking.
Take a bunch of things that have snap fits apart and see how they work. You can measure to see the required distortion and measure the force required to produce that distortion to get an idea of the material properties involved.
Designing a plastic snap involves careful consideration of the snap fit features, material selection, and manufacturing processes. Here's a step-by-step guide to help you design a plastic snap:
1. Identify the Components: Determine which parts you want to connect using the plastic snap. Typically, one component will have a male feature (protrusion or tab), and the other component will have a corresponding female feature (recess or slot).
2. Material Selection: Choose suitable plastic materials for the components. The material should have the required flexibility for snap fit functionality while also providing the necessary strength and durability for the application.
3. Design the Snap Features:
a. Male Feature: Design the male feature with a tapering or ramped shape that allows for easy insertion during assembly. The male feature should have enough flexibility to bend and snap into the female feature.
b. Female Feature: Design the female feature to accommodate the male feature securely. The female feature should have sufficient clearance for the male feature to snap in easily but maintain a strong hold once assembled.
4. Snap Point: Determine the snap point, which is the location where the male and female features meet during assembly. This point is crucial for a successful snap fit connection. The snap point should be designed to create an audible "snap" sound, indicating proper engagement.
5. Consider Tolerances: Factor in manufacturing tolerances to ensure that the snap fit will work consistently, even with slight variations in component dimensions.
6. Stress Analysis: Perform stress analysis on the snap fit features to ensure they can withstand the forces involved during assembly and repeated snap cycles without breaking or permanently deforming.
7. Prototyping and Testing: Create prototypes of the components with the snap fit features and conduct testing to verify the snap fit's functionality, strength, and reliability. Iterative testing and improvements may be necessary.
8. Wall Thickness: Ensure that the wall thickness of the components around the snap features is adequate to prevent breakage or failure during assembly.
9. Draft Angles: Incorporate draft angles into the design to facilitate mold release during the injection molding process, especially if the components are to be mass-produced.
10. Mold Design: If the snap fit components are to be mass-produced, work with a mold designer to create an injection mold that can produce the desired snap fit features accurately and consistently.
11. Assembly Instructions: Provide clear assembly instructions to users, indicating how to snap the components together correctly and disassemble them without causing damage.
Remember that designing a successful plastic snap requires careful attention to detail, prototyping, and testing to ensure a functional and reliable connection. Collaboration with experienced plastic design engineers and manufacturers can also help you optimize the design for the specific application and manufacturing process.
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