We have encountered many problems about the best way to fasten different 3D printing components. For example, when prototyping a hardware product, it is usually necessary to make an assembly structure that is more complex than a single 3D printing component, such as an electronic shell or a robot component.
Sometimes, you may need to print components of the building package of a 3D printer that is too large, so you need to consider ways to assemble the printing parts permanently or intermittently.
One way to assemble 3D parts is to use snap fit components, but another good method is to use threads.
There are many different methods to implement threads in 3D printing parts, so we will introduce the advantages and disadvantages of the most commonly used methods and the specific installation steps to help you get started.
Threaded insert
Our preferred method, and our most frequently recommended method, is to use threaded inserts because they are easy to install and feel good.
Advantages: fast, simple and clean; Unlimited assembly / disassembly; Production quality
Disadvantages: more expensive; The wall thickness needs to be increased
Materials and tools: brass inserts; Soldering iron; Precision knife
Installation steps:
1. Place the insert into the relevant hole to be pushed in
2. With a heated soldering iron, place it in the middle of the insert and apply a small amount of pressure.
3. When the insert starts to heat up, you will see it sink into the hole
4. Once the blade appears flush with the part surface, please use your precision blade to check and trim any excess material
Self tapping screw
Another method of threaded inserts is to use self tapping screws. If you want fast but dirty things, this is the simplest and cheapest way. So if this is your first prototype, or if you are using low resolution materials, such as PLA, self tapping screws are a good choice.
Advantages: easy installation; Minimum design requirements; cheap
Disadvantages: brittle materials may break; Limited assembly / disassembly; Low strength; Materials and tools; Self tapping screw
Installation steps:
1. It's as simple as a screwdriver and a screw... Just screw it
Design thread into 3D model
When designing parts that require very large threads, the best way is to design the threads into the 3D model itself.
Advantages: Custom thread can be designed; Good when the insert is not available (i.e. M50 thread); Suitable for brittle materials
Disadvantages: the thread will wear with time; It is difficult to model accurately; High resolution printing is required; Materials and tools
None (CAD only)
Installation steps:
1. Ensure the accuracy of thread modeling
2. Print components using high-resolution materials
3. For internal threads, use a tap to "finish" the thread. If you do not have a tap available, try using a machine screw.
4. For external thread, please use a steel nut that matches your thread size and use it to complete the thread on the part.
5. Ensure that the through hole of the part is completely tapped - this will ensure that excess material is removed from the tapping feature and the part is ready for fastening.
6. For blind holes, ensure that the tapping depth is sufficient for assembly and ensure that any excess material is cleaned (attempting to screw fasteners into parts with debris may damage your function).
When using this method to add a thread to a printed part, make sure that it is vertically aligned with the thread feature; Special attention should be paid to avoid cross threading, which may cause permanent damage to the parts.
Cut the thread with a tap
This is the most traditional method of using threads. In reduced material manufacturing, once the CNC places the hole at the position where the thread will pass through, a drill tap is used to create the required thread in each hole.
When prototyping with 3D printing, you can create threads in a plastic prototype using the same method as a hand drill tap.
Advantages: better assembly / disassembly than self tapping screws;
Disadvantages: low strength; The plastic wire wears away with time; Time intensive
Materials and tools: drilling and tapping; Screw;
Installation steps:
1. Tap the thread features with the corresponding drill bit to cut the available thread
2. Be careful not to damage components when applying torque
Fixed hexagon nut
Another common strategy for fastening parts together is to create printed pockets for capturing hex nuts.
Advantages: low cost solution; Good clamping force; Easy to install
Disadvantages: only applicable to external surface; Additional material is required to fix the nut; Design constraints
Materials and tools: hex nuts; screw
How to use this method:
1. Measure the size of fasteners - this is a good resource to help you.
2. Add a little tolerance (0.005 – 0.010 inch) to the hole size to accommodate any dimensional error.
3. Before pressing the nut into the bag, apply a little glue on the nut, but stick it to the inner surface of the bag. Otherwise, when torque is applied to the nut, it may be pulled out of the groove
Mechanical precautions
The following three questions can help you consider which approach is best for your project:
1. Do you need to disassemble and reassemble components?
2. What is your strength requirement or retention?
3. What are the inherent geometric or spatial constraints in part design?
In addition, when designing the fastening function, please keep the following three important considerations in mind:
1. Bending along an axis parallel to the printing should generally be avoided, as the components printed in this direction are much weaker in structure.
2. When adding assembly features, please pay attention to the allowable stress and strain of the material.
3. Please carefully check the CAD model before adding fastener features. For example, if you want to add a hex nut, check the height of the hex nut used; If a threaded insert is to be used, check the pitch of the installed insert.
