Planetary Gears with Herringbone Teeth

thingiverse

A collection of interlocking planetary gears with herringbone teeth holds itself together within a central ring gear, necessitating that it be printed in one piece as a single unit due to its intricate design. Print Settings: Printer Brand: Ultimaker Printer Model: Ultimaker 2 Rafts: Not required Supports: Not necessary Infill: 100% Notes: The original design was too compact, causing the gears to stick together after printing. To prevent this, I scaled up the entire model by at least 1.5 times, allowing for sufficient clearance between the teeth and enabling them to break free easily. I used an Ultimaker 2+ with a 0.25 mm nozzle and 0.08 mm layer height for the print. Cooling fans were disabled for smaller components but not for the main gear body. UPDATE: I recently printed another version using 0.1 mm layer height and faster speeds, which resulted in a less smooth operation. To achieve optimal results, I recommend printing with extremely thin layers and very slow speeds to help the gears separate after printing. Alternatively, you can scale up the entire model by more than 1.5 times. UPDATE 2: I uploaded revised models that incorporate design changes: The handle shape has been altered, a handle spacer added to prevent it from rubbing against the ring gear, and a round outer surface has been included for easier handling. UPDATE 3: A new version of the planet gear carrier, available in .sldprt and .stl formats, allows access to the sun gear bolt without disassembly. Post-Printing: After printing, I freed the teeth by scoring the bottom layers where they mesh and then twisting them. This improved movement and a small amount of sewing machine oil further enhanced performance. I improvised with the attaching hardware, using available parts that matched the scaled-up dimensions. The planet gears and carrier spacers are tapped for 1/4 - 20 threads, while the handle is tapped for 3/8 - 16 threads. The handle is securely attached to the sun gear, making them static relative to each other. Carrier spacers act as lock nuts to keep the carrier screws stationary relative to the planet gears, preventing them from coming loose when rotating the sun gear. The planet gear carrier can freely rotate relative to its holding screws. How I Designed This: I utilized a gear generator found at http://hessmer.org/gears/InvoluteSpurGearBuilder.html to create .dxf files for each gear and then imported these drawings into SolidWorks. After cleaning up the sketches (the imported .dxf files had an excessive number of points), I extruded them to half their desired thickness and applied a flex feature on each gear body to achieve the necessary twist. The degree of flexibility varies among gears, requiring some time to understand. If the sun gear's twist is x, then the planet gears need 2x and the ring gear 1/2 x twist. A set of flex features must have negative twist as well, but I am unsure if it's the planet or ring gears. Once all flex features are complete, you will have a set of planetary helical gears. To create herringbone teeth, simply mirror everything across the sketch plane.