Wrapping up

We used Ashby's Model to estimate cost and assumed that all manufacturing was done in the United States with labor cost $13/hour. The material used was ABS. We assumed that the total cost of the equipment was $100000 and that the life time of the machine was estimated to be 10 years with a load factor of 0.9. The waste fraction was assumed to be 0.3. We approximated overhead costs by considering wages of plant workers and energy consumption by the plant.

For prototyping a run of 100 yo-yos, we calculated a price of $12.81 per yo-yo. A production run of 100,000 would bring that price down to $4.41 per yo-yo.

Ashby cost model
part mass	0.0384	kg
mtl cost	3.902	$/kg
waste frac	0.3
C1 (matl)	0.21	$/part
prod rate	0.23566	parts/min
equip cost	100,000	$
load factor	0.9
lifetime	10	yr
	5256000	min
C3 (equip)	0.09	$/part
*Assume need to buy but will be used again
Ct	840	$/tool
nt	1,000,000	tool lifetime (parts)
n	10,000,000	total run (parts)
C2 (tooling)	0.0008401	$/part
	8,401	total
Coh	58	$/hr
prod rate	14.1396	parts/hr
C4 (overhead)	4.10	$/part
Total cost($/hour)	4.41	$/part
for 100 yoyos
n	100
C2	8.4014
total cost	12.81
for 100000 yoyos
n	100000
C2	0.0084014
total cost	4.41

2.008 shop design constraints

The first iterations of our design involved high levels of detail in areas that would have to be pocketed by the milling machine. This was a poor design decision since the capabilities of the milling machine only allowed a depth of 1/2” pockets for 1/32” radial precision. To improve our design from this stage we decreased the width our yoyo by decreasing the depth our pockets, such that the depth of our pockets maximized the capabilities of the milling machine.

To make the yo-yo more suitable for manufacturing, we would alter the design of our thermoform core. The current pattern is difficult to line up with the die for cutting, slowing down production. A better set of alignment holes would improve the process.

Improving the course

Here are some suggestions from various members of our group.

“Although we all gained familiarity with MasterCam towards the end of the semester, the process could have been a little less painful if we would have had to complete a guided tutorial by ourselves, with Dave roaming around, answering questions about why exactly we are modifying the settings and changing parameters described. Dave’s tutorials were good, but most of the times I just followed along cluelessly, leading to very little awareness. Lectures were also good but not engaging. The first few ones had demos and were exciting (especially the guest lecturers from Stroud), but towards the end, energy dwindled tremendously.”

“I think that it would have been better if the homeworks, lectures, and labs were more related to each other”

"Overall, I loved the class and deeply appreciated how much I learnt by the end, but I think that it would have been better if the homeworks, lectures, and labs were more aligned. Specially I feel that the first Psets were not related to what we were doing in the lab, and this made me a little bit confused. Also, I feel like I would have learnt much more if we were allowed to discuss Psets with other people. "

“I think the lectures should’ve had a quiz component at the end of every lecture. I really appreciate the synthesis that this provides. I also think that expectations for psets were unclear and that the lecture material was very unrelated to the psets. Though I appreciate the learning that happened during the psets, part of what makes learning fun is going to lecture and applying the fundamentals learned there to a word problem. I also think turnaround time could’ve been better. We didn’t know what level of detail was expected for psets until the third pset. I thought the lab component of the class was fantastic though an extra staff member would’ve been useful.”

“I was unable to make it to office hours for many of the homeworks, and found myself struggling as a result. I wish that the lectures had covered the homework material in more depth.”