Blog created together by Hannah Delatte and Emily Murray  

Using inspiration from past projects, we decided to make a butterfly flapping its wings for our project. To begin, we created a rough sketch of what we wanted our design to look like, which is included below. Our original idea was to have a wooden frame that holds a butterfly structure. When the crank is rotated, the butterfly flaps its wings and a flower to the right of the butterfly rotates, mimicking a butterfly “circling” a flower. The dimensions and materials of our starting design changed throughout the process as we began iterating and talking through our ideas.

 

Originally, we were going to work with mechanical movements #96 and #25, which are for the cams/shafts combination and perpendicular gears, respectively. The cams and shafts would be used to move the butterfly body and wings up and down following the rotation of a crank. The flower would simultaneously rotate, and this would require a transition from vertical to horizontal motion, thus the idea of using perpendicular gears. After consulting with the teaching team, we found out that perpendicular gears would be difficult to execute, so we got rid of the flower idea and just focused on the butterfly. Still, our design heavily imitates mechanical movement #96 for the motion of the butterfly.  

We made two low fidelity prototypes; the first one we cut by hand to get a feel for the dimensions, and the second one we laser cut to get a better idea of how our cams would actually work. For the first one, we used the dimensions included in our design sketch to trace and cut out the frame, cams, and butterfly on a piece of cardboard. We used popsicle sticks as shafts, and also cut out a decorative butterfly. When we assembled everything together, it had absolutely zero functionality. The holes we cut in the top for our shafts to run through were too large, and the popsicle sticks basically just wiggled back and forth instead of moving up and down when the crank was rotated. However, it did give us the idea of adding a second, stabilizing layer for the shafts to run through, which would sit between the top of the frame and the dowel with the cams. 

From here, we made an Adobe Illustrator file and began working on an actual design that we could cut with the laser cutter. Similar to the laser cut box project, we made our frame fit together with finger joints to reduce the amount of wood glue we had to use. We also added that second layer for the shafts, and designed some egg and teardrop shaped cams. We decided that our cams and shafts needed to be thicker for more stability, so each cam and shaft is two pieces fixed together. When we laser cut and put everything together, the build had some functionality and decently represented how we wanted our model to work/look. 

 

 

 

 

 

 

 

 

Moving onto the medium fidelity prototype, we stuck with the Adobe file that we made for our low fidelity (while adjusting the kerf and thickness for the finger-jointed pieces).  While assembling, we used a Dremel to file the dowel down so that it would fit into the bearings. To attach the cams to the dowel, we just used wood glue to stabilize them so that they wouldn’t slide against the dowel. Once everything was assembled, we tested out our butterfly and noticed a couple of problems including:

1. Our cams were slightly too large, and were just a hair away from being able to make a full rotation when the followers were being lifted all of the way. A quick fix for this for our medium fidelity prototype was to sand down the end of the followers until a full rotation of our cams was possible.
2. Our openings for our cam followers/ shafts holding our butterfly were slightly wider than needed, and allowed for more horizontal movement than we wanted. While it wasn’t a problem with this iteration, we wanted to minimize the possibility of our future cam followers moving and falling off of the side of our cams.

We adjusted our cams to be about ½ an inch smaller for our higher fidelity prototype, which worked well and allowed for plenty of room for achieving a full range of motion for our butterfly! For our follower guide holes, we narrowed the tolerance between them and the shafts which significantly reduced the unwanted wiggling of our followers. Additionally, we decided not to glue down the wings of the butterfly to the shaft and instead attach them to the body using metal wiring. This would allow for a more realistic looking butterfly wing flapping instead of the simple up-down motion shown in the medium fidelity. We extended the area of the top of our shafts to be able to hold and catch the butterfly wings as they’re flapping, and to better balance the body.

Since we were able to quickly get our moving parts working, we were able to spend some extra time on the aesthetics of our model. We decided on having a whole butterfly garden theme, complete with details of grass and a variety of flowers. We started with an outline of the body of our prototype to be able to adjust our pieces to be the size and shape we wanted to minimize having to cut them twice. 

We also wanted to be creative with our name plate, so we began ideating how we could include it in the theme of our butterfly garden. We ended up deciding on a simple sign on the front, and we loved how it turned out!

Again, cute was the goal here, so we wanted our metal piece to be more than just a piece of metal. We had decided earlier on that we wanted our handle to have our metal component, and when ideating ways to make our handle we decided on an offset-crank handle design to ensure an easy turn of our shaft. We decided that the shaft of the crank would be metal and the handle/ grip would be wooden, a more comfortable grip than metal. We decided to make this metal component a flower, sticking with our theme.

Initially, the flower was designed too narrow and the thickness between the hole for the shaft and the outer portion of the flower was too small, and the piece broke while being waterjet cut. We recreated the file and made our flower a little thicker, and it cut out perfectly after that! We secured this piece to the shaft with wooden washers we laser cut, and attached the wooden dowel that served as the handle the same way. 

The crank was the last component of our design to be assembled, and we may have procrastinated testing the crank due to unreasonable stress surrounding the whole system not working. Was the stress and procrastination unnecessary? Absolutely. Did the crank and butterfly work perfectly fine? Almost. 

There was a little bit of excess friction being caused by the weight of the wings pressing down on the front of our followers which were hitting our cams, but once we sanded down the front edge of the followers our design rotated more smoothly. We also used a tiny spray of Mr. Dupont for an added lubricant.

After letting out a few victory squeals, we kind of just sat and blankly stared at each other for a bit. We are so proud of our little butterfly, and we hope people can have as much fun with it as we did making it!

 

 

 

 

 

 

 

Link to Powerpoint

Video of finished product

 

COST ANALYSIS:

Cost Type	Cost	Price	Source	Quantity	Total
Materials	Wooden sheet ¼” thick, 2x4ft	$12.98/sheet	Lowe’s	2 sheets	$25.96
	Aluminum sheet	$15.19/sheet	Amazon	0.25 sheet	$3.80
	Assorted acrylic paints	$9.99/20 paints	Hobby Lobby	10 paints	$5.00
	Black spray paint	$2.48/can	Home Depot	1/16 can	$0.16
	Orange spray paint	$5.98/can	Walmart	1/16 can	$0.37
	Steel wire	$6.27/110 feet	Amazon	0.5 feet	$0.03
	Vinyl sticker	$8.99/roll	Amazon	1/30 roll	$0.30
Labor	Laser Cutter Operator	$16.74/hr	ZipRecruiter	2 hours	$33.48
	Waterjet Operator	$15.00/hour	ZipRecruiter	0.5 hour	$7.50
	Vinyl Cutter Operator	$16.00/hour	ZipRecruiter	0.5 hour	$8.00
	Prototyping Engineer (You!)	$38/hour	ZipRecruiter	5 hours	$190
Overhead	Facility Cost (Machine Time)	$1.20/8hr  (laser cutter) + $25/hour (waterjet cutter)	EpilogLaser (laser cutter) + Omax (waterjet cutter)	3 hours (laser cutter)  + 0.5 hour (waterjet cutter)	$0.45 + $12.50 = $12.95
	Quality Control	$41/hour	ZipRecruiter	1.5 hour	$61.5
Design	Engineering and Development	$48/hour	ZipRecruiter	8 hours	$384
Misc.	Waste and Scrap	Rest of wooden sheet (accounted for in materials section)	–	–	–

TOTAL COST: $733.05