Electric Hoist With 3D Printed Parts

I'm Jason Moran and I am a third year mechanical engineering major at the University of Georgia. The goal of this project was to create an electric hoist with mostly 3D printed parts that can lift about 20 pounds. However, I purposely chose a low torque DC motor that is incapable of lifting 20 pounds by itself and used 3D printed spur gears (or other gear types) and pulleys to produce a mechanical advantage. I also 3D printed a motor mount, casings, shafts, axles, and any other parts that may be needed to properly complete the task. The only parts that were not 3D printed will be the DC motor, ropes, screws, bearings, and other electric components.

PLA 3D Printer Filament

775 DC Motor

608-2RS Ball Bearings (8mm x 22mm x 7mm)

8mm x 300mm shaft

For easy calculations, I decided on a 10:1 gear reduction ratio. Thus means that for each gear set the speed would decrease by a factor of 10, but the the torque would increase by a factor of 10. The rated speed and torque of the 775 DC motor is 20000 rpm and .74 N*cm, respectively. I used Fusion360's gear script to create 2 different gears. one was 120mm in diameter while the other was 12mm in diameter. Both gears had 1mm modules and a 8.2mm hole in the middle to fit the 8mm shafts. I decided on this shaft size because the first bearings I found were 8mm.

Designing the bearing mounts and shafts was more simple. The shaft was just a 7.8 mm cylinder and I used the sketch attached along with the extrude function to make the ball bearing mounts.

I added a switch and a power supply to the motor and glued everything to a wood base.The DC motor came with a mount that I screwed into place. I added M4 holes to the bearing mount to screw them in place on Fusion 360, but I could not find a drill bit to make M4 holes in the wood. That's why the mounts were superglued into place. Each gear set was measured to be 66 mm apart (60 mm diameter big gear and 6mm diameter small gear). The gears had to be glued to shafts as well. Next time, I will probably add set screws so they can temporarily attached instead of permanently. However, the end goal was a success. I used three 10:1 gear sets for a gear reduction of 1000:1. This means the output shaft moved at 200 rpm and 740 N*cm according to the data sheet.