Our video can be found at this link:

https://www.dropbox.com/s/b0tfaxj4t1xfb8u/Final%20Movie.mp4

For the cost analysis for our prototype please see the following link:
https://www.dropbox.com/s/za6r3rdqmw86pa8/producton%20cost%20analysis.xlsx

Blog Deliverable 5

1) Cost Analysis

Ashby cost model
AJH 10/21/13
Total run	100000
Desired rate	1000	/day
Run length	100	days
Machine throughput	432	parts/day
Machines needed	3	machines
Machine cost dedicated	1500000	total
	15	$/part
part mass	0.05	kg
mtl cost	2	$/kg
waste frac	0.3
C1 (matl)	0.14	$/part
prod rate	0.3	parts/min
equip cost	500,000	$
load factor	0.9		("uptime")
lifetime	10	yr
	5256000	min
C3 (equip)	0.35	$/part
Ct	10000	$/tool
nt	100000	tool lifetime (parts)
n	100000	total run (parts)
C2 (tooling)	0.1	$/part
	10000	total
Coh	50	$/hr
prod rate	60	parts/hr
C4 (overhead)	0.83	$/part

For our final cost analysis, including a cost per yo-yo graph, see our spread sheet:

https://www.dropbox.com/s/veivodlpqhscq71/producton%20cost%20analysis.xlsx

2) Yo-Yo Design Reflection

Our yo-yo design was influenced by the 2.008 manufacturing equipment in terms of size of the yo-yo. We determined the outer diameter of our yo-yo body from the size of the molds we were given and the sizes of the inserts from the size of our yo-yo body. Also we were restrained by having to make our own shaft collars. We would have been able to put the nuts farther into the yo-yo otherwise.

We would change our design for mass production by adding a rotational alignment feature such as a notch on each piece. This would allow for the machine to align and snap fit our parts automatically. We would also redesign the "spider" insert to have a greater draft and thicker runners such that the part would pop out of the mold more easily (the runners are clipped off of the side of our spider prior to snap fitting). We will also try to minimize material per yo-yo and our waste fraction.

3) Recommendations for Class Improvements

 

We believe that the reading quizzes, although helpful, were often too specific in their questioning and a lot of the time spent preparing for class was used trying to remember specific facts rather than the general or conceptual lessons that meant to be taught.

On the topic of the topics covered in class we think that the class did a very good job of covering almost every type of manufacturing out there in at least some detail, no easy task. We also think, however, that too much time was spent on the specific details of metal manufacturing and cutting, especially the “Nerd Work” as Professor Culpepper called it. Most of these processes are described in detail with a quick Google search and while learning about the physics of it should definitely be a part of every mechanical engineer’s training the time we spent on it was unnecessary. With things such as 3D printing we just covered the basics of the process and how it looked from the outside, yet knew how to run the process. This is how we think that the metal cutting section of the course should run.

With regards to the problem sets we think that too many of the problems seemed unnecessarily convoluted and that giving a problem that might actually appear in the workplace may be more useful. A better way to explain this might be that nearing the end of the semester many of the members on our team realized that the best way to solve many of the problems on the problem set was just to look through the notes and find the applicable solution, which was invariably buried on some page, then plug and chug. Instead of having these kinds of problems we suggest having a problem where the students are made to think critically about the manufacturing line in question and, even though the math may become a bit easier, ask them more specifically about the Cost, Quality, Rate and Flexibility of the process being studied. We feel like these would be more like the questions asked of a manufacturing engineer rather than finding the cutting force of a specific machine, for example.

In addition we would like to thank Dave & Dave for putting up with us and putting all of our teams on their backs.

Blog Deliverable 4

  Glow-in-the-dark snap-fit center. Grooves around the upraised triangles to allow for another snap-fit part and consistent outer radius allows for snap fitting into the base. In total, was a great success of a part.

   Blue version of our Yo Yo base. Consistent inner radius allows for the snap fitting of other parts inside it. In total went very smoothly.

   Our "Spider" snap-fit piece. We often had problems with weld lines and an inability to pop this piece of of its mold (as it would stick onto the triangles and oval). We could improve this piece by increasing the draft on the triangles so that it doesn't stick in the mold as much.

 One of the thermoformed parts. These all came out very well and snapped perfectly into the center of our yo-yo.

 Our completed yo-yo from the back. The clear triangles are glow-in-the-dark!

  Finally, our completed yo-yo from the front! What a pretty yo-yo.

Specifications Comparison Sheet
Specification	Planned Dimension	Measured Dimension
String Groove	.25” +/- .005	.058 +/- .01	Didn't meet design specifications because we shortened the string gap after manufacturing
Base Inner Diameter	2.25+0.0/-.005	2.245 +/- .002	Part was easily injection molded and met specification
Snap Fit Part 1 (Triangles) Outer Diameter	2.21''+.005/-0.0	2.26 +/- .001	Part was easily injection molded and met specification
Snap Fit Part 2 (Spider) Outer Diameter	2.21''+.005/-0.0	2.26 +/- .002	After much tinkering with the injection molding, part met specification
Mass Base	13.12 g+/-10%	15.5 g +/- 8%	Part was outside of design mass, but consistent
Mass Snap Fit Part 1 (Triangles)	9.71 g+/-10%	7.5g +/- 4%	Part was outside of design mass, but consistent
Mass Snap Fit Part 2 (Spider)	2.11 g+/-10%	2.4 g +/- 10%	Part was outside of design mass, but consistent
Mass Thermoform Right	.348 g+/-10%	.340 g +/- 10%	We made multiple runs until we got the process to the point where we liked it.
Mass Thermoform Left	.3812 g+/-10%	.392 g +/- 10%	We made multiple runs until we got the process to the point where we liked it.
Mass Total	. 05078 kg+/-10%	.0541 kg +/- 10%	Since all of the parts were consistent, the whole was consistent.
Max RPM	.047m/s+/-10%	3350 RPM	Roughly what we calculated!

Summarized findings in Deliverable 4 of the "Triangles" Insert

The Triangle Insert's critical dimension was its out diameter, which we needed to control to snap fit the part into the base of the yo-yo. We found this dimension to have a UCL of 2.265 inches and an LSL of 2.255 inches. All of our parts were within this range and thus our part snap fit in successfully!

Link to Deliverable 4:

https://www.dropbox.com/sh/ata8l7eibfgm1lj/2GHzJ_hOIX