Blog Deliverable 4

Thermoformed Radioactive Symbol

Key Features:

·         Laser cut sticker added in post-processing to add color to the thermoformed part

·         Radioactive symbol is sunk into a circular shape

Successes:

·         All parts within tolerance

·         Optimized system parameters four times before production run

Opportunities for Improvement:

·         Add more complexity to design; create a more intricate shape to explore the limits of the thermoform machine

Thermoformed Biohazard Symbol

Key Features:

·         Laser cut sticker added in post-processing to add color to the thermoformed part

·         Biohazard symbol is sunk into a circular shape

·          Intricate design required special consideration of where to place vaccuum holes

Successes:

·         Most parts within tolerance, although parts out of tolerance were still able to fit in YoYo production which suggests over toleranced design specifications

·         Complex design required remachining but came out very well in the end

Opportunities for Improvement:

·         Make the intricate parts of the design thicker to aid in the application of the sticker during post-processing

·         Optimize design parameters more to ensure all parts are within specifications

Injection Molded Core

Key Features:

·         Ejector pins placed on inside which is covered by thermoformed parts so they are never seen

·         Runner hole is on the outside edge and barely noticeable in outside part

·         Thick core makes for a durable and sturdy YoYo with sufficient mass for good YoYo-ing

·         Aggressive spline allows for YoYo to land on string easier during use to perform advanced tricks

Successes:

·         Almost all parts within tolerance

·         Black color came out very nicely

·         Blemish-free from gate, runner, and ejector pin marks after post-processing

Opportunities for Improvement:

·         Optimize parameters further to reduce variability in production process

·         Examine design changes to reduce weight

·         Reduce plastic flow a tiny amount; small amount of flash noticed in some parts

Injection Molded Cap

Key Features:

·         Ejector pins placed on inside which is covered by thermoformed parts so they are never seen

·         Runner hole is on the outside edge and barely noticeable in outside part

·         Cap is specified to be an interference fit with the core to reduce amount of hardware required in YoYo

·         Glow in the dark color for use at night

Successes:

·         Part was over toleranced so despite many parts being outside of original specifications the YoYos could still be assembled properly

·         Blemish-free from gate, runner, and ejector pin marks after post-processing

Opportunities for Improvement:

·         Optimize parameters further to reduce variability in production process and ensure parts are within specifications

·         Examine design changes to add features or complexity to the ring

·         Optimize glow in the dark color additive as parts had variable coloring

Completed YoYo, Biohazard Side

Completed YoYo, Radioactive Side

2.  Table of Design Specifications

Part	Design Spec	Measured Spec	Explanation
Thermoformed Biohazard Symbol	Outer Diameter 1.5” +/- 0.005”	Outer Diameter 1.5055” σ = 0.002”	This part was completed outside of specifications. The process was over the desired outer diameter size for most of the process. This was likely due to the remachining that had to be completed on the part which may have altered the size of the mold piece. Furthermore, the system parameters may not have been optimized correctly after the remachining took place. However, upon assembly we discovered that the tolerances were over specified because the yoyo was able to be assembled and performed fine despite the above tolerance diameter.
Thermoformed Radioactive Symbol	Inner Hole Depth 0.08125” +/- 0.00500”	Inner Hole Depth 0.08135” σ = 0.002”	This part was completed almost entirely within design specifications. It was only during the intentional parameter change during the production run that parts fell out of tolerance. This is a sign of a well optimized process. To give background, over four trial runs were completed before the final production run in order to make sure the parts met all of the design specifications. The parts turned out very nicely and fit seamlessly into the overall yoyo design.
Injection Molded Core	Inner Diameter 2.068” +0.000” -0.005”	Inner Diameter 2.0682 σ = 0.0033”	This part also fell within design specifications for the overall average. However, there was a high standard deviation which according to the Shewhart X-Bar chart led to some units which should have been rejected outside of the units which faced the parameter change. The high standard deviation signifies a lot of variability during the production which could have been a result of the mold heating up over time, non-uniform plastic flow as a result of the colors we used, or a variety of other factors. However, during the measurement of these yoyos’ critical dimension, the people doing the measuring was switched halfway through. It is most likely that inconsistencies in their measuring technique contributed to the large standard deviation rather than something in the process. This is further evidenced by the fact that all yoyos assembled seem to have a good interference fit despite the high standard deviation found in the parts.
Injection Molded Cap	Outer Diameter 2.078” +0.005” -0.000”	Outer Diameter 2.073” σ = 0.002”	This part was completed outside of specifications. The process was over the desired outer diameter size for most of the process. This was likely due to the remachining that had to be completed on the part which may have altered the size of the mold piece. Furthermore, the system parameters may not have been optimized correctly after the remachining took place. However, upon assembly we discovered that the tolerances were over specified because the yoyo was able to be assembled and performed fine despite the above tolerance diameter. However, these pieces were machined for an interference fit and thus some pieces could not fit exactly with the first chosen core but in the end all cap and cores were able to have an appropriate interference fit.

3. Link to Deliverable 4 for Biohazard Part: Biohazard Production Reflections