3D Printing Snap Fit Joints: Design & Implementation

When your prints consist of multiple parts, snap fit joints are a great way to connect those parts. However, 3D printing interlocking features can be challenging.

There are two main types of 3D print snap fit joints. Annular joints consist of a boss and groove and are relatively easy to design. Cantilever snap fit joints are a lot more challenging. In both cases, choosing the wrong materials could shorten the joint’s lifespan. 

While the technical joint name might not mean much, you likely use them often in real life. Annual joints typically hold airtight lids firmly fixed to the container, whereas cantilever joints are used to buckle backpack straps. 

In addition to these two common types, you can also 3D print other kinds of snap fit joints. Find out which they are and when to use them.

5 Common Types Of Snap Fit Joints

There are several types of snap fit joints that you can design and implement in 3D printing.

Here are the most common types based on popularity. 

1. Cantilever Snap Joint

Cantilever snap fit joints are perhaps the most common joints of this type, but they can be challenging to design and implement in 3D printing. 

The reason is their shape. These joints consist of a cantilevered beam that flexes when the two parts are pressed together. The beam then snaps into place, holding the parts together. 

The main difficulty when designing this joint type is determining the tolerances and clearance needed to allow the joint to snap in place easily, but without a risk of becoming loose.

Printing this joint type is also tricky, as individual parts might need support. If they do, post-processing could alter the original measurements and the way the joint snaps in place. 

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The choice of material is also important, as some filaments are too weak to ensure that the part works as intended.

2. Annular Snap Joint

An annular snap fit joint is essentially a circular protrusion that fits into a matching circular groove. The two parts are pushed together until the protrusion snaps into place in the groove – this joint type is often used for airtight containers. 

Due to the simpler design, these joints are the easiest to design and print. You can use a variety of filaments for them, including ABS, PETG, nylon, and TPU.

However, you should still test the joint after printing to make sure it works as intended. Push the male part (with the circular cross-section) into the female part and make sure the lip fits snugly into the groove. 

If it doesn’t, you can fine-tune the clearance and print again. You might also be able to fix the issue by sanding off some of the material.

3. Tapered Snap Joint

This snap fit joint design uses a tapered shape to create a secure connection between the two parts.

One part has a tapered protrusion, while the other part has a matching tapered recess. The parts are pressed together, and the taper creates a wedging action that holds them in place.

When designing this type of joint, make sure that one of the parts has a tapered edge and the other a small undercut or hook that can create a locking mechanism for the joint.

When printing, pay attention to the orientation – the tapered edge must face in the correct direction.

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Print the parts and test them to make sure they fit snugly in place. If they don’t, you’ll have to adjust the undercut or hook shape and print again.

4. Hinge Snap Joint

A hinge snap fit joint is a thin, flexible section of material that allows two parts to pivot against each other. This type of joint is often used for lids or covers, as a replacement for the annular snap joint. 

In this hinge type, one part features a series of thin, connected sections. The other part features the grooves that can accommodate these sections. This design can make it challenging to print such a joint, especially if you want to use rigid materials.

For the best results, you should use hinge snap joints when printing with TPU, TPE, or some other kind of rubber-like filament. You should also aim for a thickness of 0.02mm or less, or the thick parts might be hard to fit together. 

5. Snap Latch Joint

The last type of snap fit joint is the snap latch. 

This is a snap fit design that uses a latch mechanism to hold two parts together. The latch snaps into place to lock the parts, and can be released by pressing a release button or lever.

Since this snap fit joint requires both flexibility and strength, the best material to print it out of is either ABS or PETG. Another crucial thing is choosing the right infill – this joint type requires a high infill percentage or a strong infill pattern, or it might crack.

More complex than other joints, it might also require additional parts, such as a spring or catch, to complete the joint. For this reason, they are seldom used in 3D printing. 

Benefits Of Using Snap Fit Joints

Snap fit joints can be straightforward or a pain to design, but regardless of the type, they all come with advantages.

Here are some of the benefits of using these joint types.

Easy Part Assembly

Snap fit joints make it easy to connect 3D printed parts because they eliminate the need for fasteners like screws, nuts, bolts, and adhesives.

The snap fit joint design relies on the inherent flexibility of the material to allow for parts to be snapped together and held in place securely. 

This makes assembly and disassembly of 3D printed parts quick and easy, without additional tools or hardware. Snap fit joints also provide a clean and streamlined appearance to finished products by eliminating the need for visible fasteners.

Reduced Assembly Time 

By eliminating the need for fasteners, snap fit joints also speed up assembly time. Since all you have to do is to snap the joints in place, the assembly becomes a streamlined process. 

This might not seem like much if you’re only printing one part, but if you have to print several copies of the same object, these joints can help you complete the project faster.

Secure Connection 

When printed from the right material and with the correct infill pattern and percentage, snap fit joints deliver a sturdy connection between the parts. 

They can hold the pieces in place just as well as screws or adhesives would. However, only the snap fit joints have the huge advantage of allowing you to disassemble the part just as fast as you put it together.

Increased Aesthetics 

Another advantage related to the elimination of external fasteners is the improved overall appearance of the part.

Snap fit joint connections are typically hidden from sight, giving the printed part a sleeker look. For this reason, these joints are preferred for artistic or decorative prints.

Design Flexibility 

Snap fit joints can be used in various 3D printing applications, including mechanical assemblies, consumer products, medical devices, aerospace components, and automotive parts. 

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For instance, the joints can reduce assembly time and improve the aesthetics of mechanical products. From toys to household items, snap fit joints can be found in a variety of everyday-use 3D printed items.

In the medical industry, these joints can improve the functionality of the final product and ease up maintenance. The same is true for the automotive industry.

For both the automotive and aerospace industries, snap fit joints are also preferred because they can reduce the weight of the final part. 

This type of design flexibility and versatility makes snap fit joints a better choice than traditional fasteners.

Cost-Effective Solution

While snap fit joints are often larger than other fasteners, they could be more cost-effective to print for your parts. Their main advantage is that, more often than not, they can be printed as a single piece, then post-processed into the final joint. 

One of the advantages related to this is that you can speed up the printing process. Printing fewer parts, even if larger, is generally faster than printing more small parts but that must be printed individually. Obviously, this also saves you energy.

On the other hand, by printing snap fit joints as one part you can ensure that the joint parts fit perfectly with one another.

Easy Part Maintenance 

As explained, snap fit joints are as easy to put together as they are easy to take apart. This makes part maintenance a breeze, since you won’t have to unfasten several small fasteners. 

Reassembling the part is also faster, which is another reason why snap fit joints are popular in the medical, automotive, and aerospace fields. 

6 Tips For 3D Printing Snap Fit Joints

Snap fit joints come with multiple advantages, but they can be challenging to print. Here are some of the tips to make your work easier.

1. Use Appropriate Design Techniques 

The most important thing when printing snap fit joints is designing the part accurately. Beyond the software choice – you can use any CAD program – you should pay attention to details such as filet radius and part geometry. 

In 3D printing, the filet radius refers to smoothing the sharp edges and corners of a model. This reduces the likelihood of stress and increases the strength of the final print.

Smooth edges are also important for snap fit joints, allowing the parts to fit smoothly against one another.

Part geometry also plays a role. Through software stimulation, you can analyze and optimize the joint design to optimize tapers, draft angles, and reduce stress.

2. Experiment with Different Joint Types 

When designing a joint, you should also consider the part that you’re going to use it on. Different joint types suit different projects. 

For instance, the cantilever snap fit joint is best suited for small parts that require a strong but not permanent connection. Typically, it is used for miniatures, toys, and other small everyday items. 

Annular snap fit joints are typically used in the manufacture of plastic caps for bottles and container lids. However, you can also use them for other cylindrical parts that must be joined in a semi-permanent way.

Latch snap fit joints are another type of semi-permanent connection, usually seen in flaps, doors, and container lids. It can also be used for other household items. Likewise, hinge joints work for small items such as phone cases and other accessories.

Tapered snap fit joints are best suited for items that require a stronger connection than a cantilever, and are often seen in automotive and aerospace prints.

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3. Consider the Materials 

Another thing to consider when printing snap fit joints is the type of material that you should use: 

  • ABS: This is a strong and durable material that is often used for functional parts. It has good impact resistance and can withstand high temperatures. It is ideal for joints that require high strength. 
  • PLA: PLA is a biodegradable and easy-to-print material. It is a good option for snap fit joints that don’t require high strength.
  • PETG: This strong and flexible material is less brittle than PLA and has better impact resistance. It is a good option for snap fit joints that require strength and some flexibility.
  • TPU: A flexible, rubber-like material that is often used for printing parts that require some degree of flexibility. It is a good option for snap fit joints that need to be flexible and resilient.
  • Nylon: It is a strong and durable material that has good impact resistance and can withstand high temperatures. It is a good option for snap fit joints that require high strength and durability.

4. Pay Attention to Layer Orientation 

While layer orientation depends on the type of joint and the material used, it is recommended to print snap fit joints in the orientation that provides the most strength and stability. 

This may involve orienting the print so that the layers run perpendicular to the direction of the snap fit joint, which can provide greater strength and stability. 

It is also important to consider the tolerances and clearance required for the specific snap fit joint design, as well as any support structures that may be necessary to ensure a successful print.

5. Use Supports Carefully 

The three most important things when using supports are the support settings, their interface, and removal ease. 

Most slicing software allows you to adjust the support settings, such as the support density and the support angle. Adjusting these settings can help you achieve the best support structure for your snap fit joint design.

A support interface is a thin layer of material that is printed between the build plate and the supports. This can make it easier to remove the supports after printing and can help prevent damage to the part.

Lastly, when designing your snap fit joint, make sure to design it in such a way that the supports are easy to remove. This can include adding support removal features such as support pillars or support bridges.

It goes without saying that you should only use supports if absolutely necessary.

6. Consider Post-Processing 

Depending on the material used and printing accuracy, your snap fit joints might need post-processing. Sanding is a common method to remove burrs and small defects, but don’t shave off too much material, or the joint might become loose.

If the material allows it, chemical or vapor post-processing – with acetone or other solvents – might be a better choice. Heat treatment can be used to increase the flexibility of a joint, but remember that improper use could affect joint quality.

Final Thoughts

Snap fit joints are essential structures in 3D printing, but they can be challenging to design and implement. Choosing the right material for the type of joint you’re creating is also crucial, to ensure suitability for the application. Regardless of your purpose, we hope this guide can help you create the perfect parts.

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