Candl
An automated tabletop candle-making device.
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Overview
Developing core motion systems for an automated tabletop candle maker
I developed and integrated the wick-placement and stirring mechanisms for Candl, an automated tabletop candle maker. The work centered on repeatable motion, compact packaging, subsystem integration, and designing around the constraints of heating, cooling, sensing, cleaning, and user access.
Integration Challenge
The stirrer needed to translate vertically, rotate through molten wax, and fully retract for cooling and user access. Meanwhile, a thin wooden wick had to be dispensed one at a time, guided into the center of the candle, and held repeatably in position without interfering with the stirring hardware.
Design Focus
I developed a servo-indexed revolver wick cartridge and tapered guide chute, then worked through its integration with the lead-screw-driven stirring assembly. The design routed wick placement through the stirrer’s central workspace while maintaining motion clearances, and incorporated a spring-loaded bayonet interface so the stainless stirring rod could be quickly removed for cleaning.
Technical Work and Learnings
Precision Wick Placement Challenge: Reliably dispense and position a thin wooden wick one at a time without snagging, double-feeding, or shifting during cooling. Solution: Developed a servo-indexed revolver cartridge with discrete wick slots, a stationary dispensing opening, and a tapered guide chute that constrained the wick vertically while still allowing clean release. Learning: Precision dispensing is largely a tolerance and friction problem. Motor accuracy only matters if the physical interfaces consistently guide the part where it needs to go. Shared Mechanical Workspace Challenge: The wick-placement and stirring systems both needed access to the same small region directly above the candle while operating at different points in the process. Solution: Integrated the wick chute through the stirring assembly’s central workspace while coordinating clearances around its rotating platform, lead screw, linear rail, and candle access path. The stirrer could retract vertically so the wick could remain positioned during cooling. Learning: Motion envelopes need to be designed together, not subsystem by subsystem. A mechanism can function perfectly alone and still fail once neighboring systems begin moving through the same space. Stirring + Serviceability Challenge: Mix molten wax and scent uniformly while allowing the wetted stirring component to be removed easily for cleaning and scent changes. Solution: Worked on a vertically translating, gear-driven stirring assembly using a lead screw and linear rail, with a removable stainless-steel stirring rod retained by a spring-loaded bayonet interface. Learning: Cleaning and maintenance should influence mechanism architecture early. Making the wetted component removable simplified serviceability without requiring the entire actuation system to be disassembled. Integration + Tolerance Stack-Up Challenge: High subsystem density and multiple FDM-printed interfaces created alignment, binding, and tolerance-stack issues during final integration. Solution: Iterated printed geometry and clearances, reinforced the cantilevered stirring structure, and used the adjustable 80/20 frame to tune subsystem positioning during assembly and testing. Learning: Interface tolerances become more important as system density increases. Rapid prototyping makes iteration fast, but clearly defined datums, clearances, and mechanical interfaces are what make repeated assembly reliable.
