For the midterm, we combined our skills and knowledge of multiple concepts including woodworking, advanced manufacturing techniques, laser cutting, metal cutting and post processing, subtractive processing techniques etc to create a mechanical model based on a gearing system.
Inspired by a previously submitted assignment, we chose to create a wooden planetary model consisting of the earth, its moon, and the sun.
Prototyping:
We initially chose to place the movable gear system in a press fitted later cut box, however, we found that the teeth did not fit together as desired, thus, we used two laser cute wood sheets with holes cut in each of the four corners for the vertical supports.
We derived the gears from movement #24 depicted in 507 mechanical movements.
For the low fidelity models, Linda downloaded the p gear files downloaded into Adobe Illustrator and created the gears one with 20 and the other 40 teeth. For the low fidelity models, the gears were cut out in cardboard using the Epilog M2 laser. One circular piece with four holes for support of the top left gear was also cut for the model.
Fabrication
Using the AI files created by Linda in Adobe Illustrator of the top and bottom rectangular pieces (15”x9”) and holes in each of the corners for the vertical support dowel pieces, the 3” diameter 20 teeth gear piece with a 0.4764” hole in the center, 6” diameter 40 teeth gear piece with a 0.4764 hole in the center, 6” diameter 40 teeth gear piece with a 4” circle cut out of the center, a 3” diameter 20 teeth gear piece with a 0.2” hole in the center and four circles cut around the center, a 6” circle with four circles cut around the center 0.2” hole (thickness of the internal gear dowels), and 3 1.5”, 3”, and 6” concentric circles.
The pieces were cut on plywood using the laser cutters. Two pieces each of the gears were laser cut and joined to get her with wood glue in order to reinforce them.
On the left, a 0.4764 inch dowel was attached to a ball bearing and to the bottom wood piece. The 6” gear was glued to the dowel 0.5 inches from the bottom. The 3” gear with a hole measuring 0.4764 inches was attached to the left dowel a few inches above the bottom gear. The right center dowel was marked at the same height for attachment of the acrylic circle support piece underneath the 6” gear ring.
A 0.2in thick dowel was placed on the right side of the bottom piece. Assembly followed with 0.2” thick dowels measured 4.5 inches long used to attach the top outer concentric ring with the 6” gear ring. The 3” gear was attached to the right center dowel 0.5” from the bottom. Four internal support dowels connect the 3” gear with the inner concentric ring at the top using the holes cut in them. Linda took care to precisely arrange the pieces and make sure all moving parts fit before any wood glue was applied.
Metal cutting and post processing:
To fulfill the metal piece requirement, Feyi created an Adobe file of a star (3”x3”) for cutting using the waterjet cutter. Using a 0.278 inch thick aluminum plate, Feyi cut out two stars, filed the sharp points, and sandblasted it for a finished, shimmery look. Linda attached the star to the dowel using glue and sanded the excess wood on the top.
For post processing of the wood pieces, Feyi sanded the entires surfaces of the top and bottom rectangular pieces, the gears, top concentric circles, and the circle pieces that represent the sun, moon, and earth. Afterwards, a light wood stain was applied all over the wood pieces, the sun was spray painted orange and gold, the moon piece flat gray and stone gray and the earth piece blue, and the top rectangular piece was spray painted white.
Using Adobe Illustrator, Feyi created multiple star shapes arranged randomly for printing using the vinyl cutter. The cut out stars were placed on the top piece after the white spray paint had dried. This created a stencil for a white background and the entire top was spray painted black to portray a starry night picture. Beeswax was also applied on all the wood pieces.
Linda created the nameplate (with both Linda’s and Feyi’s names, the class name, semester, and mechanism number) in Adobe, cut it out in acrylic material using the laser cutter and attached it to the top of the structure using wood glue.
| Cost Type | Cost | Price | Source | Quantity | Total |
| Materials | 4×4 1/4” birch plywood sheet | $29.88 | HomeDepot.com | 4 pieces | $119.52 |
| Materials | 5”x5”x3/10” 6061-T6 aluminum plate | $32.09 | Metaldepot.com | 1 piece | $32.09 |
| Materials | 4”x2”x 3/16” A36 steel plate | $23.78 | Metaldepot.com | 2 pieces | $47.56 |
| Materials | 12”x24”x1/8” Acrylic clear sheet | $15.23 | AcmePlastics.com | 1 piece | $15.24 |
| Materials | Sand Paper (180 grit) | $6.68 | HomeDepot.com | 2 sheets | $13.36 |
| Materials | Sand Paper (220 grit) | $5.98 | HomeDepot.com | 1 sheet | $5.98 |
| Materials | Wooden dowels | $12.99 | Amazon.com | 100 pieces | $12.99 |
| Labor | Laser cutting Operator | $10/hr | Self | 2.5 hours | $25 |
| Prototyping Engineer (You!) | $15/hr | Self | 15 hours | $225 | |
| Overhead | Facility Cost (Machine Time) | $10/hr | Epilog M2 laser | 2.5 hours | $25 |
| Facility Cost (Machine Time) | $10/hr | Plasma cutter | 1 hour | $10 | |
| Facility Cost (Machine Time) | $10/hr | Sand blaster | 10 minutes | $1 | |
| Facility Cost (Machine Time) | $10/hr | Waterjet cutter | 1 hour | $10 | |
| Quality Control | $2.50 | $2.50 | |||
| Design | Engineering and Development | $50 | Self | $50 | |
| Iterations | 2 previous versions included a press fitted box, a steel handle, and solid gears | $50 | |||
| Misc. | Waste and Scrap | Pieces of wood that amount to two 4×4 sheets were left unused and steel pieces for a previous iteration of the handle | $76.55 | ||
| Total | $585.23 |
