How Do You Put Two 3D Prints Together?

3D printers have a limited size, but that doesn't necessarily mean you can't produce bigger items. If one print is not sufficient, you can glue multiple pieces together. There are some sound ways of joining 3D printed parts - you can glue them together, attach screws or other fasteners, weld pieces together, or design pieces that fit together. These methods assist you in creating bigger objects, merging various materials, and developing things that are capable of movement or disassembly.

Method 1: Use Adhesives to Join 3D Printed Parts

Adhesives create a chemical bond between two surfaces. You apply a liquid adhesive to the parts you want to join, press them together, and wait for the adhesive to cure. Different adhesives work better for different materials and projects, so choosing the right one matters.

Types of Adhesives

Super Glue (Cyanoacrylate)

The super glue sets in seconds, making it ideal for quick repairs to 3D printing materials such as PLA, ABS and PETG. It's easy to find and use. However, the bonds can break under stress, and it doesn't fill gaps well. It sometimes leaves white marks on the surface.

Two-Part Epoxy

Epoxy creates very strong bonds and works with most 3D printing materials. It fills gaps well and you can sand or paint it after it cures. The trade-off is that it takes longer to set, needs mixing, and can be messy. You'll need clamps to hold parts while it cures.

PVA Glue (White Glue)

PVA glue is safe and easy to clean up. It works well for temporary joints or test fits. However, it's not very strong and dissolves in water. Best for educational projects or temporary joints with PLA, ABS, or PETG.

Specialized Adhesives

These adhesives are made specifically for 3D printed parts. They often work well but cost more than regular glues. Check what materials they work with before buying.

Preparing Surfaces for Better Bonds

Good surface preparation leads to stronger bonds:

• Clean off any dust or oils - they can prevent good adhesion
• Lightly sand smooth surfaces to give the glue something to grip
• Wipe everything down with isopropyl alcohol
• For tough-to-bond plastics, consider using a primer

Tips for Applying Adhesives

A few key steps will help you get better results:

• Use just enough adhesive - too much creates mess and can weaken the bond
• Keep parts aligned while the adhesive cures
• Use clamps when needed, especially for structural joints
• Follow the manufacturer's instructions for cure time
• Consider how your joint design affects strength - lap joints often work better than straight butt joints

Think about what your project needs. For quick, simple joins, super glue might be perfect. For something that needs to be really strong, take the time to use epoxy. Match your adhesive to your project requirements, and you'll get better results.

Content created by @cicstancoe using the QIDI 3D X-Plus printer

Method 2: Join Parts with Mechanical Fasteners

Mechanical fasteners like screws, bolts, pins, and rivets physically hold 3D printed parts together. Unlike glue, most mechanical fasteners let you take parts apart later, which is handy for repairs or adjustments.

Types of Fasteners You Can Use

Self-Tapping Screws

Self-tapping screws are easy to use and widely available. They work well with PLA, ABS, and PETG when you design screw holes into your prints. Just be careful not to overtighten them - they can strip the plastic threads. They're good for basic joints and access panels, but may not hold up to frequent disassembly.

Machine Screws and Bolts

When you need stronger connections, especially for parts you'll take apart often, machine screws or bolts with nuts work better than self-tapping screws. They're great for load-bearing joints in any 3D printing material. The trade-off is that your design needs holes for the screws and space for nuts, plus you'll need tools for assembly.

Pins and Dowels

Pins and dowels are simple and cheap. They're excellent for aligning parts or reinforcing glued joints. You can also use them for hinges or decoration. While they're not very strong on their own, they work well combined with other joining methods. The main challenge is getting the holes lined up correctly.

Rivets

Rivets make strong, permanent joints and work well for thin parts. They create a clean look, but you'll need special tools to install them. Be careful with softer plastics - rivets can crush them. Use rivets when you want rigid assemblies that won't need to come apart.

Designing Parts for Mechanical Fasteners

Your 3D model needs holes that match your fasteners' sizes. For screws or bolts, add clearance for nuts and tool access - you'll need space to fit a screwdriver or wrench. Advanced users can create threads in the model for screws, but this requires careful attention to size and spacing. Good planning at the design stage makes assembly much easier.

Tips for Assembly

• Drill pilot holes for screws in harder plastics
• Don't overtighten - plastic threads strip easily
• Use washers with bolts to spread out the pressure
• For stronger threads, consider heat-set inserts

The key is matching the fastener to your needs. Think about how strong the joint needs to be and whether you'll need to take it apart later.

Method 3: Weld 3D Printed Parts Together

Thermal welding joins plastic parts by melting them together at the joint. You can use a filament welding pen, ultrasonic equipment, or chemical solvents to create these bonds. Each method works differently and has specific uses.

Three Ways to Weld

Filament Welding Pens

A 3D printing pen can work like a welding tool. It's affordable and good for filling gaps or joining complex shapes. It works with PLA, ABS, and PETG. While it takes practice to make clean welds, it's useful for repairs and reinforcing other joints. The main drawback is that it's slower than other methods, and the weld strength depends on your skill.

Ultrasonic Welding

This industrial method creates strong, consistent welds very quickly. It works well with ABS, PC, and PP plastics. However, it requires expensive equipment that most hobbyists won't have access to. It's mainly used in manufacturing where many identical parts need to be joined.

Solvent Welding

Warning: This method needs special care. It uses chemicals to melt and fuse plastics together, creating very strong joints. However, it's mainly for ABS plastic using acetone. The solvents can be dangerous - you need good ventilation and safety equipment. It's easy to weaken the plastic if you use too much solvent. Don't try this with PLA, and beginners should avoid this method.

Important Safety Points

• Only weld similar materials together
• Control heat carefully to prevent warping
• Work in a well-ventilated area, especially with solvents
• Use butt joints or lap joints for the strongest connections

Tips for Using a Welding Pen

• Apply the melted filament with steady control
• Build up the weld in thin layers
• Sand the weld smooth if needed for appearance

You can choose your welding method based on your materials and needs. For most home projects, a filament welding pen offers the best balance of cost and usability.

Method 4: Design Interlocking Parts

Interlocking features connect parts through shapes designed into the 3D model itself. Parts click, snap, or press together without needing glue or screws. Some connections can be taken apart later, while others are permanent.

Types of Interlocking Features

Snap-Fits

These joints have hooks or tabs that flex and snap into matching spaces. They're great for cases, lids, and parts you need to open sometimes. While they're easy to design and don't need tools to assemble, they might get weaker over time and need precise printing to work well.

Dovetail Joints

Dovetails use wedge shapes that lock together. They resist pulling apart and look good too. They work well for furniture and structural parts that need to be strong. They take more skill to design and print correctly, but they create sturdy connections.

Mortise and Tenon Joints

One part has a tab (tenon) that fits into a hole (mortise) on the other part. They're relatively simple to design and good for keeping parts aligned. For extra strength, you can add glue or pins. These joints work well for frames and furniture.

Press-Fit Joints

Parts are designed to fit together tightly through friction. They're simple but need very accurate printing. Press-fits work well for gears, bearings, and knobs. Be careful during assembly - too much force can crack the parts.

Design Requirements and Measurements

Getting interlocking features right starts with good design. Use CAD software to make precise measurements. Account for how your printer and materials might affect the fit. Test small sections first to check if parts fit together properly. Think about your material choice - some plastics flex better for snap-fits, while others are more rigid for press-fits.

Assembly Methods and Techniques

Try fitting parts together before final assembly. Use gentle pressure when connecting parts - a soft hammer or padded pliers can help. For tight fits, a bit of silicone grease makes assembly easier.

Good interlocking features can make assembly faster and eliminate the need for extra fasteners. The key is careful design and testing to get the fit just right.

Make Your 3D Prints Better with Joint Techniques!

Mechanical fasteners enable you to take apart later. Welding creates strong, jointless connections. Interlocking details eliminate extra parts. Select your method based on what you're building and how it needs to operate. Simple builds can use only super glue, while complex builds can use a series of different methods of joining. Test it on tiny pieces of the material first, and always follow safety protocol when applying adhesives or welding materials.