Thursday, December 5, 2013

Blog Deliverable 4- Comparison of the Design vs Measured Dimensions

We compared the part dimensions we measured to the dimensions we should have expected based off our design. The dimensions that are reported here are the critical dimensions of the yoyo parts. Therefore, these dimensions are the ones that we plotted on a histogram in our paper deliverable.

Red RingOuter Diameter1.970 +0.000/-0.0051.9523
Inner Diameter1.711.7266
Orange RingOuter Diameter2.210 +0.000/-0.0052.2279
Inner Diameter1.950 +.005/-0.0001.97
Basketball ThermoformExtruded Top Diameter1.711.7432
Bugs BunnyDiameter2.192.1948
BodyInner Diameter of main pocket2.192.203
Assembled Yo-YoString Gap.0750.1027

The red ring did not meet the target for the dimensions. The red ring inner and outer diameters were about 10-20 thousandths larger than the design specifications. This was likely because we did not account for the shrinkage correctly when designing our molds. Additionally, the rings may not have been balanced well to ensure the same thickness at all points on the ring. This would result in a large variation during the measurement of the rings, so our average measured value may not actually be representative of those parts. However, this did not affect the overall assembly of the yo-yo because we overcompensated for shrinkage for all of our mold designs.

The orange ring did not meet the target for the dimensions. Again these dimensions were 10-20 thousandths larger than the design specifications. As mentioned in the red ring blurb, these differences could be due to the fact that we did not account for the shrinkage correctly. It's also possible that the rings had varying thicknesses, resulting in a large variation in the diameter measurements.

The basketball thermoform did meet the target for the thermoform parts considering the level of variation that can occur during the thermoforming process (+/- 5%). The upper limit would be 1.83", so the thermoform diameter was within the target we were looking for.

The Bugs Bunny thermoform did meet the target. The average measured value for all our parts was less than 5 thousandths larger than the designed dimension value. This is within the process tolerance we used for machining our molds.

The body dimensions did meet the target. Although it was larger than 5 thousandths of an inch, the value was very close compared to the variation of the other parts. Additionally, this part was only about 10 thousandth of an inch larger than the diameter we specified, which actually ended up ensuring for a good snap fit inside the body.

The measured string gap did not meet the design target that we calculated. It was about 0.025" larger, which is about another half of the string diameter. We were aiming for 1.5 times the string diameter, based off Dave's recommendation. We believe that this error can be attributed to the fact that the nut was not embedded in the yoyo body such that one face of the nut is parallel to the bottom body face. The dimensions of the shaft spaces and the nut shaft was measured to be the correct dimension; however the crooked face of the nut caused a misalignment of the shaft with one halve of the body resulting in a larger string gap in the yoyo. We could probably fix this in the future by making a tigher fit for the shaft that the nut fits in. However, again this did not affect the performance of our yoyo too much overall.

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