DigiKey - Intro to FreeCAD Part 4: How to Use Heat Set Inserts | DigiKey
Heat set inserts are used to securely connect 3D printed parts with screws. They are typically made of brass with a knurled pattern on the outside and threading on the inside. The process involves heating the brass insert to melt the surrounding plastic, securing it in place once cooled. The video provides a detailed guide on designing the right size holes for these inserts using FreeCAD, including setting dimensions based on the insert's specifications. It also covers the practical steps of inserting the heat set inserts into the 3D printed parts using a soldering iron. The recommended temperature settings for the soldering iron are provided, and the importance of using a screw to prevent plastic from entering the threads is emphasized. The video also demonstrates how to mirror features in FreeCAD to efficiently create symmetrical designs.
Key Points:
- Use heat set inserts for secure, detachable connections in 3D printed parts.
- Design holes in FreeCAD with dimensions slightly larger than the insert's smooth diameter.
- Heat the insert with a soldering iron set 50-100°C above the plastic's melting point.
- Use a screw during insertion to prevent plastic from entering the threads.
- Mirror features in FreeCAD to efficiently create symmetrical designs.
Details:
1. 🔧 Introduction to Heat Set Inserts
1.1. Introduction to Heat Set Inserts
1.2. Practical Application and Design Considerations
2. 🛠️ How Heat Set Inserts Enhance 3D Printing
- Heat set inserts, typically made of brass with a knurled pattern and internal threading, strengthen 3D printed parts by allowing secure connections using screws.
- By heating the brass insert to melt the surrounding plastic, it is securely placed once the plastic cools, offering a robust alternative to snaps, glue, or direct plastic threading.
- Inserts provide a reliable solution for parts requiring assembly and disassembly, significantly reducing breakage risks compared to other methods.
- For precise implementation, some inserts come with data sheets specifying hole dimensions, though cheaper versions may require estimation.
- M3 is a widely used screw size for 3D printing projects, with bulk purchases available from suppliers like Ada, highlighting the inserts' practicality for common applications.
3. 📏 Designing Holes for M3 Inserts
- For an M3 insert that is 4 mm long, longer inserts provide more strength due to additional threads for the screw.
- The outer diameter of the knurled section is 4.2 mm, while the outer diameter of the smooth section is 3.75 mm.
- The recommended hole diameter should be large enough for the smooth section but smaller than the knurled section, ideally 0.1 mm larger than the smooth tip's outer diameter, approximately 3.85 or 3.9 mm.
- The hole depth should exceed the insert length by at least 1 mm, reaching approximately 5.2 mm, to accommodate melted plastic beneath the insert.
- A minimum of 1.6 mm of surrounding material is essential to prevent damage or misalignment of the insert.
- Consider the material's thermal properties to ensure proper melting and adherence when inserting.
- Choosing the correct hole size balances ease of insertion with retention strength, impacting the longevity and performance of the assembly.
4. 🖌️ Modeling Techniques in FreeCAD
- When starting a new document, ensure you're in the 'Part Design' workbench to create a body effectively.
- Utilize the Sketch tool on the X and Y plane to draw basic shapes, such as rectangles, for structural elements like posts.
- Apply horizontal constraints automatically or manually to maintain alignment, ensuring consistent design.
- Use symmetry around the origin to create balanced designs, which can simplify complex modeling tasks.
- Enforce equal constraints for dimensions to maintain uniformity across similar elements within the design.
- Leverage the Smart Dimension tool to set precise measurements, like a diameter of 3.9 mm, for accuracy.
- FreeCAD version 1.0 or 0.22 allows extrusion of individual lines from sketches, enhancing design flexibility.
- Prevent overlapping lines by redrawing segments as needed to maintain clarity and avoid errors.
- Address errors like broken pads by carefully selecting and recreating elements as necessary.
- Use the Expression editor for precise padding and gap measurements, specifying units explicitly to prevent calculation errors.
5. 🕳️ Creating Accurate Holes for Inserts
- Begin by using a sketch to define the placement of holes for heat set inserts, utilizing circles and the pocket tool for precision.
- Ensure accuracy by using the hole tool, which requires a reference sketch to function correctly.
- Align circles to axes using the constrained coincident tool, ensuring they remain in place during modifications.
- Utilize the symmetric constraint tool to center circles within squares, avoiding redundant constraints and ensuring even spacing.
- Dimension circles accurately, with a recommended diameter of 3.9 mm for heat set inserts, factoring in part dimensions and allowances.
- For depth, using a 'through all' option simplifies the process, but blind holes can be created to specific depths, such as 5.2 mm, depending on design requirements.
- Adjust drill points and add countersinks or counterbores as needed for screws or bolts, though these are typically unnecessary for heat set inserts.
6. 🔄 Mirroring Features Effectively
- Using the mirror tool in the part design tool allows for efficient duplication of features across an axis, saving time in the design process.
- The mirror function can be applied to various planes such as the vertical sketch axis, XY plane, or custom-made planes, providing flexibility in design workflows.
- Selecting the correct plane for mirroring, like the YZ plane, can ensure that features are accurately mirrored in the desired location.
- Hiding sketches after mirroring helps declutter the workspace, making it easier to focus on further design tasks.
7. 📐 Designing a Functional Cable Clip
7.1. Creating the Cable Clip Design
7.2. Exporting and Preparing for 3D Printing
8. 🔥 Optimal Heating Techniques for Insert Placement
- Special soldering iron tips with cylindrical ends sized to the inner diameter of inserts are recommended for even heating and to prevent plastic contamination in threads.
- These tips are compatible with Hacko soldering stations and are specifically made for number four or M3 inserts, requiring separate tips for different sizes.
- If specialized tips are unavailable, a basic soldering iron with a flat wide tip can be used as an alternative method for insert placement.
9. 🧰 Practical Guide to Insert Installation
- 1. Set the soldering iron temperature to 50 to 100°C (120 to 200°F) above the plastic's melting point; for PLA, this is approximately 225°C to 275°C.
- 2. If necessary, use a soldering station that can reach as low as 500°F.
- 3. Insert a screw into the insert so it's flush with the smooth side, and prepare pliers for holding.
- 4. Heat the top of the screw with the soldering iron to warm the insert, then gradually push the insert into the plastic.
- 5. Stop when the insert is almost flush with the part, using pliers to hold it while the plastic cools.
- 6. Repeat for additional inserts, ensuring to heat the screw and hold the insert with a tool during cooling.
- 7. The screws prevent plastic from entering the insert threads, facilitating easier future screw insertions.
- 8. Use a flat metal object to press the insert flush with the part after heating if the appropriate soldering tip is unavailable.
10. 🚀 Final Tips and Future Insights
- When designing or modifying your keepsake box or Dev board enclosure, incorporate screw holes for stability. Consider using heat set inserts for durability or threaded holes with FreeCAD.
- Ensure compatibility with device-specific screws: Raspberry Pi uses M2.5 screws, while Arduino requires M3 screws, which is crucial for designing enclosures.
- Engage with the community by sharing your designs on platforms like X, Instagram, or LinkedIn using #DKFreeCAD. Tag Digi-Key to increase exposure and community interaction.
- Future tutorials will cover advanced FreeCAD features such as gear tools, feature patterns, and Boolean operations to create custom Servo motor discs.