SLS-Printed Collapsible Light-Up Keychain
MECHENG755: Design for Additive Manufacturing | March 2024
This project involved designing and fabricating a collapsible lantern-inspired keychain specifically designed for powder-bed fusion (SLS) 3D-printing. The keychain, intended to resemble ornate lanterns, featured a hexagonal outer frame with a dynamic twist-and-lock mechanism, a hollow inner cylinder for housing electronics allowing it to light up, and design elements optimized for SLS printing.
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The design incorporated several features tailored to leverage the strengths of SLS printing:
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Diamond Pattern for Powder Removal: The outer frame’s diamond hole pattern served a dual purpose: facilitating powder removal from internal grooves during post-processing and diffusing light to achieve an ornate aesthetic. The pattern’s internal angles also allowed it to print without supports during FDM print tests.
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Circular Powder-Removal Holes: Strategic placement of circular holes at the bottom of the design streamlined the powder removal process further.
Additional design features included:​
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Collapsible Mechanism: Pins sliding in grooves enabled the lantern to expand and collapse smoothly, with a twist-and-lock mechanism ensuring stability in the expanded position.
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Integrated Push-Button: A push-panel mechanism was developed to house the button for the embedded LED. Guide rails were added to keep the button in place.
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User-Friendly Lid Design: The keyring hole functioned as a locking mechanism for the lid, preventing accidental opening and easing battery and electronics replacement.
Manufacturing and Post-Processing
The design was optimized for both desktop FDM and SLS printing. Prusa Slicer’s paint-on supports minimized post-processing time for FDM parts, while the final part was SLS printed in PA12 nylon. Post-processing involved painting the keychain, adding the electronics (consisting of an LED, button, resistor and two hearing aid batteries) and adding a keyring for a polished look.
This project provided insights into designing for different manufacturing methods, especially the trade-offs between FDM and SLS. Key takeaways included support optimization, designing for intuitive user interaction, and managing the constraints of compact, hollow structures for embedded mechanisms. Future iterations would explore more spacious dimensions to allow for additional moving parts and improved fit for electronics.