Introducing...50 completed yo-yos

The completed yo-yo:

Our yo-yo has four individual pieces that come together to create each side of the yo-yo. There is the base, the ring, the cover, and the gears. During the first few attempts at production, we ran into many problems with fit. The base was too large and the ring was too small for a press fit. Additionally, the internal hole for the gears were too large and the pegs were too small for a press fit. However, after a few iterations we came to a final mold pattern that consistently created parts that were able to press fit to create a completed part. At the end, we were successful with the press fit, specifically between the gear and pegs. There is room for improvement with the press fit between the base and ring. While we were able to join them all, it required some effort and a hammer.

Base Ring Cover

Gears

50 yo-yos:

Specifications

Part	Design specification of Critical Dimension	Realized Average of Critical Dimension	Standard Devation	Percentage of Parts In specification Limits	Comments
Large Gear	.219	0.2189	0.001159	99.99%	Press fit worked perfectly every time, though design specification limits might have been too wide
Medium Gear	.219	0.2186	0.001145	99.99%	Press fit worked perfectly every time, though design specification limits might have been too wide
Small Gear	.219	0.2190	0.001214	99.99%	Press fit worked perfectly every time, though design specification limits might have been too wide
Cover	1.92	1.9387	0.01268	23.45%	While the cover ended up being too large and exceeded the specification limits, it ended up still working in the assembly because the ring still fit around it. We designed the cover such that there was significant clearance between the ring and the cover for the assembly to still fit. Because the only constraint of the cover’s inner diameter was to be bigger than the overall diameter of the gear system, and the cover’s inner diameter was bigger than specified, the cover still fit the gears. Our design specification of mean +/- .01 was probably too strict.
Ring	2.325	2.3212	0.003377	63.42%	The ring ended up shrinking slightly more than expected causing decent amount of the parts to be below the design specification limits. However the base also shrunk more than expected, in the end none of the rings were actually too small.
Base	2.315	2.2909	0.004092	0.00016%	The base shrunk much more than expected causing pretty much all the the base parts to be below the the lower specification limit which was the specified mean -0.005. As mentioned before the the ring also was slightly small. In the end the two parts were still able to press fit together abiet with considerable effort. The design specification for this part where also probably too strict considering the parts still assembled even though none of the parts were within spec

Gears - Process capability and run charts

Part	Process Capability
Large Gear	1.437
Medium Gear	1.452
Small Gear	1.367

Overall, the gears holes had similar process capabilities (Large = 1.437, Medium = 1.452, and Small = 1.367). All dimensions were close and fit within the upper and lower control limits.

Team Mike Presents:

Mike, the Yoyo - A Stacy Mo production