Design and 3D Print a Life-Size Pointing Hand Key Hook: a Maker's Guide to Functional Art

"Well, that's a boring place for a key, how could I spice this up?" is exactly what I thought upon moving into my off-campus senior housing. In this Instructable, we'll guide you through the process of creating a unique, eye-catching key hook that merges form and function. The goal was to create an art piece that doubles as a functional key hook, replacing a simple nail while adding intrigue and interactivity to the space. That is how I landed on a life-size replica of my own hand and finger holding my keychain on a daily basis.

This project, developed for my Makers Workshop class, showcases the power of rapid prototyping and iterative design. By transforming a digital 3D model into a tangible, life-size hand-shaped key hook, you'll explore the intersection of digital fabrication and practical home decor. Whether you're a seasoned maker or a curious beginner, this project will challenge your creativity and technical skills. Let's embark on this journey of ideation, prototyping, and creation!

Materials:

1. 3D printer filament (color of your choice)
2. Command Strips for mounting

Tools:

1. 3D printer (I used an Ultimaker 3, but any comparable printer will work)
2. Computer with 3D modeling and slicing software (GrabCAD, Bambu Studio or similar)
3. Sandpaper (various grits, for post-processing)
4. Pliers (for removing support structures)

Software:

1. STL file of the hand model (provided in this Instructable)
2. 3D modeling software (if you want to modify the design)
3. Slicer software for your 3D printer

Optional:

1. Primer and paint (if you want a color different than your filament color)
2. Paintbrushes or spray paint equipment

Safety Equipment:

1. Safety glasses (for post-processing)
2. Dust mask (if sanding)

Note: Since the model is scalabale, the exact amount of filament needed will depend on your final print size and settings. Ensure you have enough filament before starting the print job.

1. Download the STL file: Begin by downloading the provided STL file of the hand model (Pointing Hand Hook Model.stl). This file contains the 3D model of the hand that we'll be printing.
2. Open in 3D modeling software: Launch your preferred 3D modeling software. I used GrabCAD, but any similar software that can handle STL files will work.
3. Scale the model: The provided file is intentionally small to allow for customization. In your software, scale the model up to your desired size. I scaled mine about 1000 times larger than the original file to achieve a life-size hand.
4. Check orientation: Ensure the model is oriented correctly for printing. The wrist of the hand should be flat, as this will be the surface that attaches to the wall. I printed it from the wrist up in the middle of the printer plate.
5. Consider modifications: If you want to customize the design, now is the time. You might want to adjust the angle of the pointing finger or add features like a keyhole for more secure mounting. You can use 4D Cinema or other model software (OnShape, TinkerCAD, or SketchUp) to modify the shape of the hand or reorient the model.
6. Export for printing: Once you're satisfied with the size and orientation, export the model in a format compatible with your slicer software (usually STL).

Pro Tip: If you're unsure about the size, try printing a small test piece first. This can help you gauge the scale and make adjustments before committing to the full print.

Maker's Note: While we're using a pre-made STL file for this Instructable, the original model was created using photogrammetry. I took 48 photos of my hand in the desired position, processed them using Agisoft Metashape to create a 3D model, and then refined it in Cinema 4D. This process demonstrates how different technologies can be combined in the maker's journey. If you have the knowledge of those softwares, you too can produce a 3D modeled hand in any conformation that you want!

Remember, preparation is key in 3D printing. Taking the time to properly set up your model will save you time and material in the long run.

1. Import the model: Open your 3D printing slicer software (I used Bambu Studio and GrabCAD) and import the scaled STL file you prepared in Step 1.
2. Orient the model: Position the hand so that the wrist is flat against the print bed. This orientation minimizes the need for support structures and ensures a stable print.
3. Configure print settings: Layer Height: Set to 0.2mm for a good balance between detail and print speed.
4. Infill: Use 10-15% for a lighter print while maintaining structural integrity.
5. Support Structures: Enable supports for overhanging areas, particularly the fingers (In Bambu, use auto tree supports).
6. Shell Thickness: Set to at least 3 perimeters for strength.
7. Adjust internal mesh: Use your slicer's hollowing feature to create a slightly hollow interior.
8. This reduces print time, material usage, and weight without compromising strength, but all is up to personal preference and customization.
9. Generate and review slices: Let the slicer process your model and generate the print layers. Review the preview to ensure all parts of the model will print correctly. You can do this by clicking the slice button in most softwares.
10. Estimate print time and material usage: Take note of the estimated print time and filament usage. This will help you plan accordingly and ensure you have enough material.
11. Save the sliced file: Once you're satisfied with all settings, save the sliced file in a format compatible with your 3D printer.

Pro Tip: Consider printing a scaled-down version first as a rapid prototype. This allows you to test your settings and make adjustments before committing to the full-size print, potentially saving time and material.

Maker's Insight: Slicing is where the digital model becomes a set of instructions for your 3D printer. Each setting can significantly impact the final product, so don't be afraid to experiment with different configurations to achieve the best results. Remember, proper preparation at this stage can make the difference between a successful print and a failed one. Take your time to get the settings right!

1. Prepare the printer: Clean the print bed thoroughly to ensure good adhesion. Level the bed if necessary, following your printer's instructions. Load your chosen filament color into the printer.
2. Start the print: Transfer the sliced file to your 3D printer. I used an Ultimaker 3, and was able to press print in the software but the process is similar for most printers. For our Bambu printer, I had to load a microSD card with the file. Initialize the print job and watch the first few layers to ensure proper adhesion to the print bed.
3. Monitor the print: While you don't need to watch it constantly, check on the print periodically. Look for any signs of issues like layer shifting, warping, or filament tangles.
4. Print duration: The full-size hand typically took 5-6 hours to print, however this can change based on your own printer and and material preference. Use this time to plan the installation location and gather mounting materials.
5. Post-print cooling: Once the print is complete, allow it to cool completely on the print bed. This prevents warping and ensures dimensional stability.
6. Remove from print bed:Carefully remove the print from the bed once it's fully cooled. If it's stuck, use a thin spatula or the provided removal tool, being careful not to damage the print.

Pro Tip: If your printer has a camera feature, use it to monitor the print remotely. This allows you to check progress and catch any issues early without having to be physically present.

Maker's Insight: 3D printing is an additive manufacturing process, building your design layer by layer. This method allows for complex geometries that would be difficult or impossible with traditional manufacturing techniques. Watching this process unfold can be quite fascinating! Remember, patience is key in 3D printing. Rushing the process or removing the print too early can lead to defects or warping. Take your time and let the printer do its work!

1. Remove support structures: Carefully break away support materials, starting from the base of the print. Use pliers for stubborn areas, being cautious not to damage the model. Take extra care around delicate areas like the fingers.
2. Surface finishing: Sand any rough areas, particularly where supports were attached. With high quality printers you will not have to do this step. I personally did not sand my model, because I was satisfied with the finishing. If you desire to sand, you can start with coarse-grit sandpaper (e.g., 120 grit) and progressively move to finer grits for a smooth finish. Pay special attention to the pointing finger, as this will be the main contact point for keys and you may want to keep it rough to prevent the key from sliding.
3. Inspect the model: Check for any printing defects or weak points. Ensure the pointing finger (the hook) is sturdy and well-formed. Look for any layer lines or imperfections that might need additional sanding.
4. Optional painting: If desired, apply primer suitable for 3D printed plastics. Once the primer is dry, you may paint the hand in your chosen color. Consider using spray paint designed for plastics for best adhesion and a smooth finish.
5. Final touch-ups: After painting (if applicable), do a final inspection. Touch up any areas that might need additional attention.

Pro Tip: If you want a super smooth finish, consider using a filler primer before painting. This can help hide layer lines and give a more polished look.

Maker's Insight: Post-processing is where your 3D print truly comes to life. While it might be tempting to skip this step, taking the time to refine your print can dramatically improve its appearance and functionality. Remember, the goal is to create a piece that's both visually appealing and practical.

Design Iteration: If you notice any issues during post-processing, document them. This information is valuable for refining your design or print settings in future iterations. Continuous improvement is a key part of the maker's journey!

1. Choose a mounting location: Select a wall space that's easily accessible and visually appealing. Consider the height for comfortable key hanging and retrieval, also keep in mind that no one could bump into it as the model is slightly pointy. Ensure the surface is clean and dry.
2. Prepare for mounting: Gather your Command Strips. These were chosen based on user interviews expressing a preference for non-permanent, easily accessible mounting solutions. Clean the back of the 3D printed hand with rubbing alcohol to ensure good adhesion.
3. Apply Command Strips: Attach strips to the back of the hand model according to the manufacturer's instructions. Ensure even distribution for balanced weight support. I recommend using at least two strips for stability.
4. Mount the key hook: Remove the protective backing from the Command Strips. Carefully align the hand with your chosen wall location. Press firmly against the wall for about 30 seconds to secure the adhesive.
5. Wait before use: Allow the adhesive to set for about an hour before hanging any keys.
6. User testing: Hang various key rings to test functionality and weight capacity. Observe ease of use and gather feedback from household members or roommates. Test with different types of keychains to ensure versatility. Remember, you don't have to hang just keys. With customization features during the printing process, you could modfiy the design and thickness of the midel to hang coats or other items.
7. Make adjustments: If the hook is too high or low, don't hesitate to remove and reposition. Command Strips allow for easy adjustment without damaging walls.

Pro Tip: If you find the pointing finger isn't at the ideal angle for your keys, you can make slight adjustments by applying heat (like from a hair dryer) and gently bending the finger. Be careful not to overheat the plastic!

Maker's Insight: Installation is more than just putting your creation on the wall. It's about ensuring your design functions as intended in its real-world context. This step is crucial for validating your design decisions and identifying any necessary improvements.

Iterative Design: Based on user testing, you may want to adjust the hook's position, angle, or even the overall design. This iterative process is crucial in design thinking and product development. Don't be afraid to go back to previous steps if you identify areas for improvement!

Conclusion

Congratulations! You've successfully created a unique, functional piece of art that serves as both a key hook and a conversation starter. This project demonstrates the power of combining digital fabrication techniques with practical problem-solving.

Tips and Troubleshooting

1. If your print has layer adhesion issues, try increasing the print temperature slightly.
2. For better wall adhesion, consider using a brim in your slicer settings.
3. If the finger seems too weak, increase the infill percentage in the finger area.

Customization Ideas

1. Try different filament colors to match your decor.
2. Scale the model up or down to fit your space.
3. Modify the STL file to include multiple fingers for hanging more items.

Safety Considerations

Always wear safety glasses when removing support structures or sanding. Ensure proper ventilation when painting. Follow all safety guidelines for your 3D printer.

Final Thoughts

This project taught me a lot about the iterative design process, from initial concept to final product. It's a perfect example of how we can use technology to solve everyday problems in creative ways. I hope this Instructable inspires you to look at everyday objects differently and create your own functional art pieces! Remember to share your creations in the comments. Happy making!