How to Install Heat‑Set Inserts for Strong, Reliable 3D Printed Threads

Threaded Components in 3D Printing

Threaded connectors, holes, and bolted joints are foundational to virtually every engineered part you manufacture. When working with 3D‑printed parts, the thread quality directly impacts assembly durability. Traditional plastic threads—either printed or hand‑tapped—are prone to stripping and wear, while metal threads deliver the strength and longevity required for high‑performance applications. Metal threaded inserts, typically brass with pre‑formed internal threads, provide a robust solution. Their knurled external surface engages the surrounding material, resisting pull‑out and torque‑out forces.

For thermoplastic 3D printing, heat‑set inserts are the preferred choice. During installation, the polymer melts and reflows around the insert, creating a locally reinforced bond that dramatically improves pull‑out and torque ratings compared to other insert types.

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Designing for and Installing Heat‑Set Inserts

What You’ll Need

• 3D‑printed part with appropriately sized holes for threaded inserts
• Selected heat‑set threaded inserts
• Soldering iron (650–750 °F / 343–399 °C)
• (Optional) Insert‑installation tip for the soldering iron

1. Select Bolt Size and Corresponding Insert

Choose the hardware that will fasten the part. The insert size depends on the thickness of material surrounding the cavity; if less than 2 mm (0.078”) of material remains, opt for a smaller insert. Verify the vendor’s recommended cavity dimensions. In this example, an M3 insert is used with the following specifications:

• Hole depth (D): 3.8 mm
• Major diameter (A): 5.31 mm
• Minor diameter (B): 5.1 mm

2. Sketch the Starting Point for Your Holes

Use your CAD program’s sketch tool to mark the exact location of each hole.

3. Create a Counterbored Hole

With the Hole tool, generate a counterbore that matches the insert’s major diameter (A) and recommended depth. Extend the hole beyond the counterbore base if a relief hole for screw clearance is needed.

4. Chamfer the Inner Bore Edge

Apply a distance‑distance chamfer to the lower outside edge of the counterbore. Use the counterbore height as the first distance and ">(A‑B)/2" as the second distance to achieve the required minor taper diameter (B).

5. Print Your Part

Print the part once the design is finalized.

6. Heat the Soldering Iron

Power the soldering iron and allow it to reach 650–750 °F (343–399 °C). This temperature range melts the thermoplastic without degrading the material.

7. Press Each Insert Into Its Cavity

Place the insert centered on its cavity. Align the iron tip with the insert’s center and apply gentle pressure. As the insert heats, the plastic melts and flows, allowing the insert to sink into the cavity. Keep the iron in contact until the insert fully seats and the top of the part is flush with the insert’s head. For larger inserts, allow a slightly longer heating time.

8. Allow the Part to Cool

After all inserts are seated, let the part cool for a few minutes. This ensures the polymer fully sets around the insert. Use this time to adjust any inserts that did not seat correctly.

Enhancing Threaded Connection Strength

While heat‑set inserts provide excellent pull‑out resistance, placing them on the opposite face of the part can further increase load capacity. When the insert is loaded, its taper engages the counterbore’s taper, distributing forces more evenly. Adding continuous fiber reinforcement around the cavity amplifies this effect by preventing wall deformation under load.

Contact us for a free sample part to evaluate the strength and durability of our materials.

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