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.