Deliverable 5

Cost Analysis

The cost of making just 50 yo-yos versus making many hundreds or thousands of yo-yos is dramatically different. At low volume, the cost is heavily dependent on the price of molds and the amount of time spent designing the pieces, but as volume increases, the ratio of those costs to the cost of material and injection molding goes down. Some basic costs which are unavoidable, no matter how fast or efficient we are are the material costs, which include the plastic, the nuts and bolts, and the axle sleeves, which come out to $1.80/Yo-Yo. When looking at the cost of running the injection molding machine, the thermoforming machine, and assembly, the cost is even more. These are all places that could have reduced costs by increasing the number of cavities, and having an automated assembly process.

Cost of manufacturing Yo-Yos at scale

To accommodate the constraints of the lab equipment, our molds were all kept under the 3in^3  volume limit. If we were manufacturing on a much larger scale, this would be the first parameter we would change. By adding multiple cavities, we can more than double our production rate, without adding any sort of design changes to the pieces. Additionally, because we did not have fantastic results with the bearing, it might have been easier to eliminate the bearing and connector piece, and have a press fit section on the body piece for the hamster to attach to. Another alternative would have been to use different bearings. Because this was our first foray into manufacturing and injection molding, the LMP essentially had all the tools we needed to complete our project; it may have been possible to come up with a more complicated design that required different tools, but our design had plenty of challenges already, and we were able to overcome them with what we were given.

2.008 Recommendations/Feedback
Though stressful at the beginning, the push to have designs, specifications, process plans, machine paths and timelines all within the first few weeks really pushed us to get on top of our project, and reduced stress later down the road. The first few labs were a good introduction to Mastercam, which no one on our team had any experience with, but at 3 hours long, they were hard to focus on the whole way through, and if you made one mistake (which we all did), it was almost impossible to catch up without bringing someone else down. I think the lectures contained a lot of interesting material, but it felt like something I could look up on my own; I didn't feel like going to lecture greatly contributed to my learning, especially when the information for the psets was contained directly in the lecture slides. If the lectures were more interactive, with less slides and more in depth examples, I think that help clarify or cement the concepts for me.
 - Marshall

In all, I feel that the class goes over some great material and gives students the exposure to a lot of manufacturing ideas and theories that I did not previously know/think about.  I now often find myself trying to figure out how certain products I encounter daily are made.  In terms of logistics, I believe that the projects in the class were great and well organized in terms of deadlines.  However, I feel that 2.008 needs a lot of improvements: mainly in communication between lectures and projects and better lecture presentation.  Early on the class becomes very stressful due to the fast turnover and timelines (I agree that it is good to have them early). This unnecessary stress could be easily mitigated if it were communicated better both in lab and in lecture.   As of now, students freak out and are uncertain what exactly is due and when it is due.  The lecture presentations had good material but failed to capture the attention of students in general.  I did not feel like they helped me learn as I found myself doze off for a minute and then be lost for the rest of it.  Instead, I would quickly read the slides and get that main information from the lecture.  To solve this problem, there just needs to be more energy and involvement right off the bat to get the class going in the right direction.  With all that said, I will definitely take away a lot from the class and it will definitely help me in the future.
 - Adrian

I really enjoyed 2.008. My future career goal is to become a great design engineer, and I feel that having a solid foundation and understanding of how things are made is essential to being a smart, productive and efficient designer. I really enjoyed 2.008 lectures. The use of demos, videos, and visuals made the lectures entertaining and interesting. Many classes at MIT stress math too much. I realize that understanding and knowing how to apply equations to solve problems is essential to being a good engineer, but often times at MIT the equations are more important than having conceptual understanding of what the equations mean. I loved how 2.008 stressed a conceptual understanding of the material. I believe more discussion in lecture could have been better, or maybe short recitations during the week that would allow the class to discuss different manufacturing processes. As far as labs go, another person on the staff would be really helpful, as I often had to wait around for one of the Daves to become available. Also, my team wasted many hours trying to figure out MasterCam. I think that 2.008 should upgrade to a better software or provide a more comprehensive tutorial. What
Dave went over in lab covered the basics, but it still left a lot of questions unanswered. I also think that more time could have been spent discussing statistics (Control charts, process capability, etc) and how to use what we learned in class to solve problems on psets and in the real world.
 - Jacob

I always enjoy hands-on project classes the most and 2.008 was definitely no exception.  Getting to see many manufacturing methods in class was very eye-opening and the in-class demonstrations were very not just interesting, but also beneficial to grasping concepts conceptually.  Doing the paperweight project early in the semester before moving on to our yo-yos was very helpful in letting us get used to the machine shop and Mastercam software.  It would have been useful to have step-by-step documentation for different Mastercam procedureds, as not all of the needed ones were covered in lab and the others were often difficult to replicate on different parts.  Following along the same vein, having an official spec sheet for the yoyo requirements would have been very handy as we often had to delay our design process while clarifying certain dimensions.  Some specific shop constraints that we had to design around were the tools available in the ProtoTRAK mill and Daewoo Puma Lathe.  We were also in a lab section with 3 teams as opposed to the normal 2, so this made the lab seem very crowded at times and made getting help from the two Dave's take longer than we would have liked.  I would also have liked to see the process parameters for the injection molding machine addressed as in-depth as machining, since the numbers we put in for injection pressure, temperature, velocity, etc., seemed to be more guess and check at times.  I would have also liked to have done more design problems on the pset in order to get us thinking about how to design for the various process beyond the yoyos that we manufactured.  Overall I greatly enjoyed the class and thought there was a very good balance of conceptual breadth, technical depth, and hands-on experience!
 - Kendall

I loved the hands-on portions of 2.008, and I really appreciated how helpful the Daves were in the shop. They were very flexible with us and helped us improve our designs a lot throughout the manufacturing process, which was great! I also really loved the occasional lectures we had from outside professionals -- in particular, the Stroud Consulting lecture and the 3D printer guest speakers were great. I think that 2.008 could be improved with some more connections between the psets and the lectures -- the pset problems were very specific, and required a lot of knowledge that was hard to remember from lectures (especially when not all of the information from the lecture is posted online). It was odd that the lectures seemed so conceptual, and yet most of the pset questions (and the test questions) were very detailed and specific. Also, 2.008 is the only Course 2 class I've taken that has non-collaborative psets; I think that students benefit greatly from working together on psets, and so I was kind of frustrated with this policy. Also, I think that there should have been more office hours, because it was hard to get help on the psets when needed. I also definitely needed more preparation materials for the test -- the one practice test that was posted had incomplete solutions, so it made it difficult to study. Overall, I think that I learned a great deal from this class, and it's a really great feeling to come out of a project class like this with such a cool (and fun) final product.
-Jessie