Threading in 3D Printed Parts: Methods for Strong and Reliable Connections

Threaded connections are fundamental in mechanical design, allowing parts to be fastened securely while maintaining the possibility of disassembly and reassembly. From industrial machinery to consumer electronics, screws and bolts provide a standardized way to connect components.

With the rise of additive manufacturing, engineers and designers have begun incorporating threads into 3D printed parts to enable modularity and functionality. However, 3D printing introduces unique challenges—layer adhesion issues, material strength limitations, and precision constraints—that can make directly printed threads unreliable.

Fortunately, there are multiple ways to introduce threading into 3D printed parts. Some methods involve designing and printing threads directly, while others rely on post-processing techniques such as thread tapping or threaded inserts to enhance durability. Each approach has its advantages and limitations, and selecting the right method depends on material properties, load-bearing requirements, and production constraints.

Methods to Create Threads in 3D Printed Parts

A. Directly 3D Printing Threads

One approach is to design and print threads directly within the 3D model. Many CAD software packages, such as Fusion 360, SolidWorks, and FreeCAD, offer built-in thread generators that allow for precise modeling.

Pros:

✔ No additional post-processing is required.
✔ Suitable for low-stress applications and rapid prototyping.
✔ Works well for large-pitch threads or coarse designs.

Cons:

✘ Weak interlayer adhesion can cause threads to shear under load.
✘ Fine-pitched threads may be unprintable in FDM due to resolution constraints.
✘ Post-processing (sanding, coating) may be necessary to improve thread engagement.

Best suited for: Low-load, coarse threads where precision is not critical.

B. Thread Tapping After Printing

For stronger, more precise threads, thread tapping is a practical solution. This involves drilling (or printing) a slightly undersized hole and using a tap to cut internal threads into the material.

1，Hand Tapping

Print an undersized hole, rotate the tap slowly, applying even pressure.

2，Machine Tapping: 

Utilize CNC or drill presses for faster, repeatable tapping in production settings.

Common Mistakes to Avoid:

⚠ Over-tightening taps in brittle plastics, leading to cracking.
⚠ Using incorrect hole diameters, resulting in loose or stripped threads.

Best suited for: Functional parts that require precise, strong, and reusable threads.

C. Using Threaded Inserts

For maximum durability, threaded inserts can be embedded into 3D printed parts to provide metal-reinforced threads.

Types of Inserts:

Heat-Set Inserts: Installed by heating and pressing into thermoplastics like ABS, PETG, and Nylon.
Press-Fit Inserts: Used in SLS and SLA prints where mechanical interference holds the insert in place.
Helicoils & Metal Inserts: Provide high-strength threading for industrial applications.

Installation Process:

1. Drill or Print an Appropriately Sized Hole.
2. Apply Heat (for heat-set inserts).
3. Press the Insert into Place.
4. Let the Material Set for a Secure Fit.

Best suited for: High-load applications where long-term durability is a priority.

Conclusion

Threading in 3D printed parts requires a balance between design, material selection, and post-processing techniques. While directly printed threads work for prototypes and low-load applications, tapping offers greater precision and strength. For the most robust and long-lasting threads, threaded inserts remain the superior choice.

At Protosoon, our technicians will Select the right method ensures functional, reliable, and durable threaded connections, making 3D printed parts viable for a broader range of industrial and engineering applications.