Snap Joint: A Guide to Producing Prototype Plastic Parts with CNC(difference between 316 and 316l Lucy)

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CNC (Computer Numerical Control) is revolutionizing the manufacturing industry by providing precise and efficient production methods. It allows for the creation of complex parts, including prototype plastic parts, with ease and accuracy. One crucial aspect of producing such parts is the incorporation of snap joints, which play a significant role in increasing assembly efficiency and reducing costs. In this article, we will explore the concept of snap joints, their benefits, and how they can be produced using CNC technology.

Understanding Snap Joints:

A snap joint is a type of mechanical fastener used to join two or more components together. It relies on fitting one part into another through an interlocking mechanism, creating a secure connection without the need for additional tools or adhesives. This makes snap joints ideal for rapid assembly processes, often seen in consumer goods like toys, electronics, automotive products, and more.

Types of Snap Joints:

There are several types of snap joints commonly used in plastic part assembly. Let's discuss a few prominent ones:

1. Cantilever Snap:
This type of snap joint features a cantilever beam structure that provides flexibility. The design includes a protrusion on one component and a corresponding recess on the mating component. By applying sufficient force, the beam flexes inward, allowing the protrusion to move past its nominal position. Once the force is released, the beam snaps back into place, holding the parts securely together.

2. Torsion Snap:
In torsion snap joints, rotational motion is utilized for assembly purposes. These joints consist of a protrusion and corresponding recess where the twist mechanism locks them together. When twisting takes place, the rotation generates enough energy to cause snap engagement. Torsion snap joints are widely used across various industries due to their simplicity and reliability.

3. Annular Snap:
Annular snap joints employ hoop stress to achieve a secure connection. The design includes an annular recess that fits with a protrusion on the mating component. Assembling the parts requires applying force to compress and deform the annular snap, which then moves past its nominal position. Once released, the hoop stress enables the joint to hold the components firmly together.

Producing Snap Joints Using CNC:

CNC technology proves to be highly effective in producing prototype plastic parts with snap joints. Follow these essential steps to create top-quality prototype parts using CNC machines:

1. Designing the Components:
Start by designing the individual components of your plastic part. Utilize computer-aided design (CAD) software to create accurate 3D models of each piece. Ensure that you incorporate features like cantilever beams, torsion mechanisms, or annular recesses into their designs according to the chosen type of snap joint.

2. Material Selection:
Selecting the appropriate material for your prototype is crucial. Consider factors such as strength, flexibility, durability, and cost when choosing a suitable plastic material. Common choices include ABS, polycarbonate, Polypropylene (PP), and acetal.

3. Programming CNC Machine:
Once you have finalized the design and selected the material, it's time to program the CNC machine. Convert your CAD files into machine-readable instructions (G-code) using CAM (Computer-Aided Manufacturing) software. This step determines tool paths, cutter speeds, depths, and other parameters necessary for manufacturing.

4. Machining Operations:
The machining process begins by securing the plastic material onto the CNC machine's worktable. The CNC machine will follow the programmed instructions to cut, shape, drill, or mill the individual components based on the desired dimensions and geometry determined in the design stage. Make sure to allocate suitable tooling for different operations and choose appropriate feeds and speeds to ensure precision during machining.

5. Implementing Snap Joints:
After machining the components, the snap joints need to be incorporated. Depending on the type of snap joint selected, additional assembly processes might be required. For cantilever and torsion snaps, the protrusions and recesses must be accurately aligned for smooth engagement. Annular snap joints require a compressive force along with careful fitting of the components together.

Benefits of Snap Joints:

Snap joints fulfill various advantages in prototype plastic parts production, some of which include:

1. Cost-Effective Assembly: Snap joints eliminate the need for costly fasteners like screws or adhesives, reducing production costs and simplifying assembly processes.

2. Rapid Production: The interlocking mechanism of snap joints allows for quick and efficient assembly, enabling manufacturers to meet high demand without compromising quality.

3. Enhanced Design Flexibility: With CNC technology, intricate designs incorporating different types of snap joints can be easily prototyped and tested, giving designers more room for innovation.

4. Simplified Disassembly: Unlike traditional joining methods, snap joints provide easy disassembly, allowing for repairs, recycling, or component replacement without damaging surrounding elements.


The combination of CNC technology and snap joints provides a powerful solution for producing prototype plastic parts efficiently and cost-effectively. By understanding the various types of snap joints available and following the recommended steps involved in their creation using CNC machines, manufacturers can streamline their production processes while maintaining top-quality standards. Embracing these essential manufacturing techniques will undoubtedly pave the way towards success in today's rapidly evolving industrial landscape. CNC Milling CNC Machining