Learning Forum

[omkar5990]

Hello all,

I am trying to do a cantilever snap fit design study. I am primarily looking at the plastic strains developed in the model, and check whether they are acceptable for the particular material. I am also looking at the stress distributions at the base of the snap fit and check if those would be close to the bending stress value that could be derived from hand calculations using beam theory. I had 3 options in mind:

1) Static structural study with a fixed displacement of the snap fit equal to that of the depth of the over-hang. I  do not plan to include the housing so as to not include contact non-linearity. 

2) Static structural study, but with contact formulation of the snap-fit and the housing, so that I just have to give a displacement boundary condition at the base of the snap fit.

3) Dynamic analysis

I wanted to know which approach would be the best, and how to justify using it. I think the first approach would be the best and the easiest to do and should give reasonable results. 

[peteroznewman]

I agree that #1 is the best way to evaluate the design of the snap-fit cantilever. It can be considered conservative because any deformation in the mating surface which would reduce the deformation of the cantilever were not included.

The advantage of #2 is that if the lead-in angle is too steep and the friction is too high, there can be higher stresses than would be modeled by #1.

Not worth doing a Dynamic Analysis unless there was some evidence that there was a Dynamics problem, like the snap lets go during an impact.

[Sanjeev Kumar]

Snap fit design is a popular engineering technique used to assemble two components together with a secure and snap-in connection, without the need for additional fasteners like screws or adhesives. This method is widely employed in various industries, including electronics, automotive, consumer goods, and more. Key Elements of Snap Fit Design:

1. Male and Female Features: The snap fit design involves two main components: a male part with a protruding feature (tab or hook) and a female part with a corresponding recess (slot or groove). These features are carefully designed to interlock when assembled.
2. Flexibility: The male and female features need to possess sufficient flexibility to allow for easy assembly and disassembly. The male feature should be able to bend and deform as it engages with the female feature during assembly.
3.  Snap Fit Features: The snap fit features are the specific geometries on the male and female parts that enable the snap fit connection. These features are designed to provide the necessary engagement and retention forces to keep the components securely joined.
4. Snap Point: The snap point is the location where the male and female features come into contact and snap together during assembly. It is a critical aspect of the design as it determines the ease of assembly and the strength of the connection.
5. Material Selection: The choice of materials is crucial in snap fit design. The male and female features are often made from materials with different stiffness levels to ensure the required flexibility and snap-in characteristics.
6. Tolerances: Manufacturing tolerances should be considered during the design process to account for slight variations in dimensions that can occur during production. Proper tolerances ensure that the snap fit connection remains functional and reliable.

Advantages of Snap Fit Design:

1.  Simplified Assembly: Snap fits eliminate the need for additional hardware, simplifying the assembly process and reducing production time and costs.
2. Aesthetic Appeal: Snap fits provide a clean and seamless appearance since they do not require visible fasteners on the exterior of the product.
3. Disassembly: Snap fits allow for easy disassembly and reassembly, which is beneficial for maintenance, repair, or recycling purposes.
4. Enhanced Product Integrity: A well-designed snap fit can enhance the overall integrity and strength of the product by distributing stresses more evenly.

Challenges and Considerations:

1. Stress Analysis: Snap fit designs should undergo stress analysis to ensure that the components can withstand the forces applied during assembly and disassembly without failure.
2. Snap Fit Durability: The snap fit should be tested for durability, ensuring that it can withstand repeated snap cycles without losing its effectiveness.
3. Application-specific Design: The snap fit design should be tailored to the specific application and mechanical requirements of the components being connected.

In conclusion, snap fit design offers a reliable, cost-effective, and aesthetically pleasing method for joining components together, making it a widely used technique in the field of product design and manufacturing.