Introduction

Snap fastening is a simple and hassle-free approach that joins two distinct elements without requiring any auxiliary equipment or securing devices. This technique is widely used in product design and manufacturing today. It offers faster assembly, reduced part count, and improved aesthetics. It also lowers production costs and simplifies maintenance. In this blog post, we will cover an in-depth overview. We will discuss what snap fitting is and the different types available. We will also explore key design principles for a successful snap fit joint.

Snap Fitting Basics!

A. Definition And Function:

A snap-fit joint is a fastener. It connects two parts together without screws, bolts or other fasteners. It relies on elastic deformation of the material. This creates a connection between two parts. The elastic deformation forms an interference fit. It holds both parts securely together, even under tension or impact loads.

B) Materials Used In Snap Fitting:

ABS, polycarbonate, thermoplastics, and nylon are commonly used. These materials offer high strength and flexibility. They are also resistant to wear and tear. Metals such as steel and aluminum are also used.

The selection of materials depends on the application. Medical devices require biocompatible materials. They need high resistance to sterilization. Automotive parts require materials that can withstand extreme temperatures. Chemical resistance is also essential. The selection of materials plays a crucial role in the effectiveness of snap fittings.

C) Product Design And Assembly – Snap Fitting’s Role:

Snap fittings are employed across a range of industries such as the automobile sector, medical equipment manufacturing, and the consumer electronics domain. This joining technique can be used for rapid prototyping and limited run production.

It is also useful for full-scale mass production. The main advantage of using snap fitting is its ease. It requires no additional tools and minimal labor resources.

Types Of Snap Fits!

Snap fits can be divided into three main types. These are cantilever snaps, torsion snaps, and annular or ball-and-socket type. Each design style offers different advantages. They must be used in the context of the overall application.

Cantilever Snap Joints:

Cantilever snap joints use a spring-style design. It securely attaches two components together. The design has several lobes or bumps on one part. There is a corresponding number of catches on the other part.

When these parts are pressed together, the lobes snap into place. They form a secure joint due to interference or ‘bite’ fit. To ensure this snap-fit does not fatigue and fail, fillet the base of the cantilever lugs. This reduces stress concentrations at these points.

Torsion Snap Joints:

Torsion snap joints use a rectangular or square groove cut into one part. They have a tab on the other. To achieve this design, two faces are machined at 90-degrees. Both contain slots with opposite curvatures.
When these parts are connected, they are rotated in opposing directions. The tab snaps into place with a ‘click’ sound. When designing torsion snap joints, ensure they are not too stiff. Avoid jamming and ensure enough clearance between them when connected.

Annular Snap Joints:

An annular snap fit joint uses a hoop-like configuration. It has multiple tabs on one part. These link together with an internal ring slot in the other for a secure connection. To create this type, two circular faces are machined at a specific angle.
They are combined to form the required slot and tabs. This design allows for extra flexibility. There is more than one tab to snap into place. This is different from other snap fit designs.

Advantages Of Snap Fitting!

Snap fits are a great way to join two parts together. They are quick, easy, and cost-effective. There are several benefits for function-specific applications:

Faster Assembly:

Snap fits can be connected or disconnected without the need for tools. This reduces overall labor costs and decreases time to market. In comparison with other fastening methods such as screws or rivets, the time taken for assembly can be reduced by up to 40%.

Reduction In Part Count:

Snap fits eliminate the need for separate fasteners. This reduces component complexity and lead times associated with procuring them.

Improved Aesthetics:

Snap fits can make products look sleeker. This has a positive impact on consumer perception of quality and user experience when handling the product.

Lower Production Costs:

Using snap fits to join two pieces together can reduce the cost of parts. This is by reducing material waste and machine setup compared with screw or rivet driven fastening methods. Additionally, since there is no need for tools or adhesives, production costs are further reduced.

Simplified Maintenance:

Snap fits provide a reusable connection between two parts. They can be easily disconnected when performing regular product cleaning operations or during general maintenance and repair. This reduces the need to keep a sufficient supply of spare parts on hand. Most snap fit joints are designed for reusability.

Key Design Principles For Snap Fitting!

In order to design a successful snap fit joint, it is important to consider several key factors. These include material selection and geometry of the components. Relevant assembly and disassembly considerations are also essential.

A) Material Selection:

Considerations For Choosing A Material

When choosing a material, likely candidates include plastics, metals, and alloys. Popular materials for snap fits include ABS, PVC, HDPE, POM, and PA6/PA12.

Popular Materials For Snap Fittings

When selecting the material to use, consider the requirements for strength and flexibility as well as cost. The most popular materials used in snap fitting include ABS, PVC, HDPE, POM, and PA6/PA12. However, another material such as NX might be chosen depending on your needs.

Plastic Fabrication

The use of plastics for snap fitting is becoming increasingly popular. This is due to their light weight, low cost, and ease of processing using injection molding or other rapid prototype processes such as SLA.

B) Geometry And Dimensions:

Cantilever Snap Joints

When designing a cantilever snap joint, the key focus should be on controlling stress concentrations at critical points like corners. To achieve this, filleting of the base of cantilever can be used. Designers should also consider increasing the width and length of clips where appropriate. This reduces the risk of failure under fatigue loading or tolerance issues during assembly/disassembly.

Torsion Snap Joints

Similar principles apply to torsion snap joints. The added consideration is tapering and minimizing air gaps/seams within a design. This ensures maximum strength.

Annular Snap Joints

Annular, or two-part snap fits also need to be properly designed and tested to ensure maximum strength. They can provide a stronger connection. However, they require precise tooling during the fabrication process due to their complex geometries.

C) Snap Joint Design Factors:

Flexibility

When designing a snap fit, it is important to ensure that the components of the join move freely without binding or excessive force being required for assembly/disassembly. This requires an understanding of the characteristics of different materials and careful engineering during the design process.

Stress Distribution

When mating components together, it is important to consider stress concentrations. These contact points may become hot spots for stress. Designers should consider ways of minimizing these contact points by changing the geometry or using materials with better characteristics for distributing forces.

Engagement Force

Engagement is an important factor in snap fitting designs. It ensures a good connection and an acceptable level of strength in the joint. By making appropriate geometry changes to a design, it is possible to control/adjust engagement forces during assembly or disassembly. This helps reduce the risk of failure under fatigue loading.

Disassembly Force

For parts that need to be taken apart for servicing or other objectives, it can be vital that the joint has an adjustable engagement and disengagement strength. To attain this goal, geometry modifications and optimization with material properties must take place accordingly.

Fatigue Life

The fatigue performance of a snap fit is another important consideration. It determines the durability and longevity of such joint components. Designers should look to improve the interface grade between mating materials by adding fillets and widening clips where possible.

D) Assembly And Disassembly Considerations:

Ease Of Assembly/Disassembly

Good snap fitting designs need to consider the ease with which parts can be assembled. This ensures that no excessive force is required for mating parts in an appropriate timeframe. To ensure this happens, it is often a good idea to add certain features such as smooth edges or extra spacers which help align two pieces and ease the mating process.

Reusability And Repairability

In some cases, parts may need to be removed and reinstalled again after being in use. This means that designers have to take into account factors such as corrosion or material fatigue, which can detrimentally affect the longevity of components when placed under stress repeatedly.

Design For Disassembly

When designing a snap fitting, it is important to consider the ease in which components can be accessed and repaired if needed. This often means providing clearance or access points to facilitate easy removal of parts.

Conclusion

Snap fitting is a great way to improve the functionality and aesthetics of components. It enables faster assembly with fewer parts, as well as simplified maintenance and lower production costs. By understanding key design principles, such as material selection, geometry and dimensions, as well as assembly/disassembly considerations, it is possible to create safe snap fitting designs that meet customer requirements. WorthyHardware provides a great range of snap fittings and materials for prototyping both parts components. Contact us today and start designing your perfect snap fit joints!

Worthy Hardware is a CNC manufacturing and sheet metal fabrication company,including CNC machining services,CNC milling services, CNC turning services, laser cutting services and stamping services.Call us +86-76989919645 or email us [email protected] for more discounts for your projects.