Deliverable 5: Closing Time

And so, after much work and strife, the semester comes to a close.







Cost Analysis



For prototyping 100 parts, our estimated total cost is $927. The cost breakdown is as follows:




set screws: $48

shaft sleeve bearings: $34

body nuts: $11

bowtie nuts: $11

polypropylene: $13

polystyrene: $20

aluminum: $70

shoulder screws: $1

bearings: $130

MATERIALS SUBTOTAL: $337

Labor for 71 man-hours at $8.25/hour : $590


COST PER YOYO: $9.27


For producing 100,000 parts, we would expect a number of variations. First of all, the cost of our outsourced parts (bearings and nuts to weigh down the bowtie) would decrease per part since we would be buying them in greater batches and could therefore negotiate lower prices in exchange for ordering a larger quantity. In addition, the costs in material of fabricating a mold would decrease per unit part since each mold would be used to manufacture a greater number of parts. Overall, our already low marginal operational and material costs would become more significant, at the expense of our high fixed cost.

The cost breakdown for full-scale production is:

set screws: $19,000

shafts: $11,220

nuts (body): $3,216

nuts (bowtie): $6,432

polypropylene: $12,600

polystyrene: $12,000

aluminum for molds: $700

shoulder screws :$30

bearings: $140,000

MATERIALS SUBTOTAL: $205,198

Labor: this is difficult to estimate, as the industrial process would likely be much different than the process we used in lab. I would expect a much greater level of automation, especially in the molding process. This, of course, would increase our mold prices considerably, but we would be able to make millions of units much more easily.

COST PER YOYO: $5.00>X>$2.05





Adaptation of Design



The 2.008 manufacturing equipment provided a series of constraints on our parts. All molds needed to be machinable on a CNC mill and lathe from Aluminum stock. The adaptation of our design to suit the manufacturing equipment is presented on a part-by-part basis.



Body: Other than changing the color, there are a couple other things we could have done to improve the body. We could have thickened the top rim to make it easier for material to flow throughout the mold better. We also could have lowered the window ledge to allow for a thicker ring and a stronger press fit.



Bow-tie: Other than optimizing for better bearings and a better body design, the only other change would possibly be putting ejector pins not on the actual bow-tie so as to lessen the chances of damaging the parts.



Window: The window was thermoformed out of a sheet of high impact polystyrene ‘HIPS.’ All sharp edges in the part were rounded to prevent discontinuities in thickness at the edges.




Ring: If made again, the ring would have been made thicker to produce a strong press fit. The thin ring deforms easily, thus weakening the yo-yo. All other aspects of the ring work well at all levels of production.





    For larger scale manufacturing, we would have done several things differently. Actual weights would be used instead of nuts in the bow ties. The ball bearings would be of higher quality. These two options would be more feasible at the larger scale since these outsourced components would be much cheaper if bought in bulk.

    More emphasis would have been placed on maximizing rate and minimizing cost at the expense quality. We would reduce the thickness of the yo-yo body in order to decrease cost and increase rate of production. This would not be worth the extra effort for small scale production, but would make a huge difference at the large scale. For the thermoformed window, we would have sacrificed quality to increase production rate by increasing the oven temperature and decreasing the heating time of our production run for each part. Although we would have a higher risk of small defects forming in the part, each part would take less time to manufacture. We could also make multiple molds so that multiple parts could be thermoformed simultaneously, which would further increase our production rate. These alterations to the design reflect our shift in priorities at the larger scale.

Constructive Recommendations for Improvement



   We appreciated the hands-on lab experience and being taught to operate heavy machinery. We also really liked having the freedom to design our own paperweights and yo-yo parts. Both Daves were really friendly and helpful towards students who were learning to use the machines and CAM software for the first time.



   The first couple of MasterCAM tutorials were difficult to follow for people who had no previous experience with this software. The pace was too fast and difficult to keep up with. Since all of the step-by-step instructions were oral, falling behind made it very difficult to catch up. It would have been extremely helpful to have a written handout detailing each step in the tutorial that could be referred to throughout the tutorial session. This would be helpful because students have various levels of experience with MasterCAM coming into the class. This way, slow students who fall behind could refer to the handout and catch up. At the same time, more experienced students could read ahead and complete tasks at their own pace, allowing Dave to progress through the steps of the tutorial at a slower pace that caters towards the new users of the software who require the most assistance.



   It would be nice to have some basic tools available in lab after hours. For assembly, our team required pliers and deburring tools for finishing operations, and an arbor press in order to assemble press-fit components. However, since these tools were all in the lab space that was locked at night, we had difficulty assembling our yo-yos outside of lab hours. A small arbor press and toolbox with pliers, files, and deburring tools in the 24-hour space right next to the lab would come in extremely handy.

    Team cabinets for storing our molds and parts were useful and convenient to have near the machining equipment. However, since they were inside the lab, they could not be accessed after lab hours. In the future, it would be nice to have team cabinets in the 24-hour space as opposed to the lab so that team equipment could be accessed at any time. There were some occasions when members of our team needed access to one of our molds in order to complete a deliverable assignment but could not do so until the following morning.