Authors: Nisarg Patel & Cameron Monroe
Over the past few weeks we have been working in pairs on our midterm project. Our project consisted of utilizing all of the prototyping techniques that we have learned so far to create a model of one of the five-hundred and seven mechanical movements. The mechanical movement that we chose was mechanical movement twenty four, spur gears. For this assignment we chose to utilize the spur gear movement to replicate moving wheels on a train. In this blog we will detail our process and our final product for this assignment.
Process:
The process of this project was broken down into 4 stages: 2D drawings, low fidelity prototype, medium/high fidelity prototype, and final model. To begin we started by sketching out our ideas and design of what we wanted on a piece of paper and then shifted that drawing into a SVG file with parts that we would need to create our design.
“This is a drawing of our final train sketch, although a rudimentary drawing it outlines what we wanted our model to look like and do. In essence we wanted our model to look like a train that was suspended into the air by pillars, and it would have a crack at the top left, when cranked, that would turn gears to move the wheels on the bottom of the train.”
“This is what our initial SVG part file looked like during gate 1, at this point in time we were still refining some parts before we would begin our low fidelity prototype.”
After we had an idea of what we were making, we began to actually produce a low fidelity prototype of the concept to see if our idea was viable and where changes could be made early on. For this step, we utilized the laser cutter and cut out parts from cardboard. Cardboard was the chosen material as it was relatively inexpensive and readily available. After our parts were cut out using hot glue we assembled our prototype.
“These are images of what our low fidelity prototype looked like, some gears are missing on this image as they fell off. Overall this model did not function as the cardboard gears were too flimsy to operate properly. However this model did prove that our design was viable with a few changes”
Upon review of our low fidelity prototype, we were advised by our mentors to expand the base and unify it into one piece. Although not shown above, the initial base consisted of 2 separate squares holding the pillars in place. After finishing up gate 2, we moved onto actually creating our medium/high fidelity prototype. For this prototype we utilized plywood to construct our entire model along with metal for our handle to move the gears and a test of our vinyl sticker. We began by slightly altering the SVG file.
Then after using the laser cutter to cut out all the parts we assembled our model using hot glue and wood glue. Then we chose to spray paint some parts of the model as well.
“In this model some gears are missing as the glue did not adhere properly and they fell off. The wheels were made out of metal for this model however we realized that it made the model too heavy to function properly so for the final model we reverted back to plywood wheels. The yellow box is a rendition of our sticker that failed to peel correctly.”
In this prototype, all the metal was cut using the plasma cutter and then post processed using the angle grinder, however we realized that this wasn’t the most accurate, so for our final metal pieces we utilized the waterjet to cut out our handle.
Finally we moved onto assembling our final model. This model was made out of both acrylic and plywood, as having the model completely made of plywood increased friction levels too much for the gears to operate properly. We began by altering our files slightly to only have to train faces, ones that would attach to the base, and move the gears in between the faces as the acrylic was clear. Then using the laser cutter we cut out all the plywood/acrylic pieces (gears and train faces), using the waterjet cutter we cut our metal handle piece, and using the vinyl cutter we cut out our sticker. After using the waterjet to cut our handle piece, we decided to post-process the piece by sand blasting it for a smooth finish and for our plywood pieces we decided to spray paint them. Then using wood glue we assembled our model.
Below is an image of our final model and our cost model for this project.
Cost model:
| Cost Type | Cost | Price | Source | Quantity | Total |
| Materials | 1/4 in. x 2 ft. x 2 ft. Sanded Plywood Project Panel | $7.28 | https://www.homedepot.com/ | 2 | $14.56 |
| ScotchBlue 1.41 in. x 60 yds. Original Multi-Surface Painter’s Tape | $6.98 | https://www.homedepot.com/ | 1 | $6.98 | |
| PITTSBURGH 1 lb. Rubber Mallet | $2.99 | https://www.harborfreight.com/ | 1 | $2.99 | |
| Digital Caliper, Sangabery 0-6 inches Caliper with Large LCD Screen | $7.99 | https://www.amazon.com/ | 1 | $7.99 | |
| Acrylic Sheet | $3.99 | https://www.hobbylobby.com/ | 1 | $3.99 | |
| Vinyl Sheet | $6.99 | https://www.michaels.com/ | 1 | $6.99 | |
| Transfer Paper | $15.99 | https://www.amazon.com/ | 1 | $15.99 | |
| Wood Glue | $2.99 | https://www.rockler.com/ | 1 | $2.99 | |
| Metal Sheet | $24.99 | https://www.amazon.com/ | 1 | $24.99 | |
| Cardboard sheet | $3.09 (for a box) | https://www.officedepot.com/ | 1 | $3.09 | |
| School glue | $0.97 | https://www.walmart.com/ | 1 | $0.97 | |
| Spray Paint | $2.98 | https://www.homedepot.com/ | 1 | $2.98 | |
| Labor | Prototyping Engineer (team) | $36.48/hr | https://www.ziprecruiter.com/ | 12/hr | $437.76 |
| Overhead | Facility Cost (Machine Time – Laser Cutter) | $50/month | https://apps.txrxlabs.org/join-us/ | 1 | $50.00 |
| Software Cost
(Adobe Illustrator) |
$19.99/month (1st year student price) | https://www.adobe.com/creativecloud | 1 | $19.99 | |
| Design | Engineering and Development | $60.70/hr | https://www.talent.com/ | 1 | $121.40 |
The total cost of this project can be estimated to be $723.66. This estimate does not take into account the rental cost for a waterjet cutter, or a vinyl sticker cutter, as these estimates were not found. However assuming a $50 rental cost for both of these machines for an hour this would add $100 to our cost model making the final estimated cost $823.66. Below is an image of our working space after everything was complete.
Reflection: At the end we are proud of our model however, we noticed it only works some of the time as for some reason the top gear does not want to adhere to the axle. We think to improve on this the next time we will increase the thickness of the gears and utilize thicker axles for better movement. Below is an image of our workspace after cleaning and a video of our model (and presentation link).
https://docs.google.com/presentation/d/1iPZGOZtqznI6wU9wfJ3mljlGIJH4JbF7VqUPTz3jkO8/edit?usp=sharing
