Harry J. - Praxis I Dossier

Projects

This page contains the details on the design projects I have done over the semester. After reading through the descriptions, you can (and should) read my takeaway from the design experiences.

Praxis I Brief I: Preventing Carpal Tunnel Syndrome

My Praxis team, consisting of Connor Fraser, Charles Kim, Monica Pramanick, and myself, have identified an opportunity for engineering design in the prevention of Carpal Tunnel Syndrome.


Framing

We framed the issue so that we would tackle CTS in the case of office workers so that our efforts would be at the same time focused on a specific problem, yet have a wide body of stakeholders for our designs.


Diverging and Converging

For this brief, we came up with many solutions ranging from alternate mouse designs to adjustable armrests to alleviate stress placed on the wrist and the carpal nerve within it. To converge, we used a Pugh Chart to compare and decide on our best solutions.

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Representing

We used different forms of prototyping to represent our ideas: for our adjustable armrest we used a 3D drawing of the solution to show the form, whereas for our computer input solutions we used a low-fidelity physical representation to approximate both form and function. The following is a representation of a computer stylus.

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Representations of the adjustable armrest design

Download SketchUp file


Praxis I Brief II: Juice Box

A design opportunity our Praxis team has also picked up on was the elimination of straw wrappers on juice boxes.


Framing and Reframing

Our team received this besign brief from another team, which had originally framed the brief as "eliminating" the straw wrapper from the juice box design in order to reduce trash. We reframed the issue as not eliminating the wrapper, but reducing the net trash created and making as much of the box recyclable as possible. Furthermore, we imposed our own values upon the problem, which are Design for the Environment and Design for Children, as children are major stakeholders in juice box use.


Diverging

We initially conceived a few designs that involved embedding the straw within the juice box, as this would create a unibody container.

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Representing and Reframing Again

We made prototypes of the first two designs (first, second, and fourth from left in picture), and what we learned is that a) the prototypes were very hard to make as creating an inset requires a lot of folding (the cardboard in juice boxes isn't easy to fold), and b) the inset straw compartments sacrifices container volume. Moreover, having two layers of cardboard makes the box bulkier and creates more trash to be recycled, which increases the box's energy footprint; this goes against our value of Design for the Environment.

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It turned out the the prototyping process not only helped us compare the many ideas we had in preparation of converging, but also helped us reframe the solution:

While building the prototypes, I found a bandage wrapper and suggested that instead of modifying the juice box, the straw wrapper could be improved. From then on, we reframed the solution from "juice-box-centric" to "straw-wrapper-centric". The third prototype from the left was an alternative straw wrapper made from the bandge wrapper with a straw replacing the bandage. It is to note that because the bandage wrapper is designed to be sterile on the inside, using this type of wrapper would allow the straw to remain food-safe.

From this experience, we learned that prototyping can, in addition to representing our ideas, generate more ideas for a solution.


Converging

We improved upon the idea stemming from our prototype and aligned the idea with our values by researching the recyclability of materials for Design for the Envorinment and food safety and interaction with children for Design for Children.

In the end, we designed a straw wrapper that would stay permanently affixed to the juice box so that the user won't create another separarate piece of trash, increasing the chance of littering. Also, we designed the wrapper so that the motions used to open the straw wrapper are minimal and are very similar to the currently used design, requiring only a pulling motion so that children may easily adapt to the new design.


Final Representing

Monica on our team turned our idea into a neat final prototype that represents what our design would look like on the market.

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CIV102: Matboard Beam

As part of the CIV102 course, students were to build a beam using limited supply of matboard and contact cement. Believe it or not, quite a bit of the design process was involved.


Framing

My CIV team (Eric Boszin, Matthew Chan, and me) have initially considered the assignment by attempting to design the beam around the load it carries. The assignment requires that it holds a 400N train and then two point loads of 200N in different tests. To assure the integrity of the beam during testing, we tried to design a beam that held a maximum total load of 1600N while being the as efficient with the limited material given as possible.


Diverging

The initial designs that were suggested were all variations upon the box beam, with one cell (1), two cells (2), or three cells (3). Hovever, a major problem arose: none of the three designs can reach the max projected load with the amount of materials we were given.

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Reframing and Diverging

Instead of being requirement-centric with a maximum load and trying to design for efficiency, we reframed the design to constraint-centric by designing for the highest load using our materials. We came up with three designs that required much less resources: the I-beam (5), the pi-beam (6), and the dual-webbed I-beam (4).

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Converging

We chose a dual-webbed I-beam design as it is more resistant to cross-sectional shear and also bending both concave up and down. By analyzing Navier's and Jourawski's equations, we determined a higher second moment of area will be more resistant to tensile/compressive and shear stresses, so we decided on a height of 150mm and width of 100mm, with 75mm between the webs.


Initial Representing

To test out our design, we built a prototype using the designed dimensions. The extra matboard went into making vertical stiffeners evenly spaced along the length of the beam. Once the beam was finished, we tested it by having me stand on the testing points. It failed very quickly.

From that test, we learned that the glue must be evenly spread, and any imperfections during gluing will cause the joints to fail first under shear stress. Moreover, with point loads at the center of the cross-section, there must be diaphragms that span the whole width of the cross-section, instead of stiffeners on each side. On the bright side, we learned that one side of the beam stayed intact, and that means more resources can be diverted from that area to the areas that failed.

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In the end, the prototype was rather short-lived, but the takeaway from the representation benefitted us greatly as we gained crucial information as to how a beam might fail and which parts of our design to improve in order to counter that.


Further Converging

To improve on our design, we used an Excel program to generate a series of designs based on our prototype, all with 100mm widths but with varyign heights. We generated maximum shear and tensile/compressive stresses based on shear, bending moment, and buckling and found an optimal height of 144mm.

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Final Representing

After optimizing our design, we built a beam with the generated dimensions and added diaphragms in critical spots. The following are the diagram of our final design and a picture of the final product.

The beam held a maximum of 890N in testing (versus 1660N predicted) and had a deflection of 2.9mm at 400N. The discrepancy of calculated max load and experimental max load can be attributed to diaphragm failure, which was not considered during calculations, and imperfections in joints.

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DfX Walkabout: Design for Serviceability in Arduino


The Arduino UNO board is an open-source microcontroller board intended to allow easy prototyping of electronic circuits. The product features many choices in terms of its Design for Serviceability, the ability to be troubleshot and maintained. [1]

Design for Serviceability can be separated into many components, namely a) ability to determine sources of errors, b) ability to fix the errors, and c) standardization of components for easy troubleshooting. With these categories in place, we can say that a design is DfServiceability at the most basic level if it satisfies a). For a design to adequately Designed for Serviceability, it should satisfy both a) and b), and well Designed for Serviceability if it satisfies a), b), and c).

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The board allows users to easily evaluate the logic on the various lines of the board. Every pin on the ATmega368P IC is broken out onto the row of female pins on the sides of the board. The SPI ports of the two microcontrollers on the board are broken out and easily accessible in order to facilitate firmware updates and upload custom code outside of the bundled Arduino IDE. Some key lines on the board are also connected to an LED to allow visual evaluation. The UART pins on the board are connected to LEDs labeled “TX” and “RX”, and GPIO pin 13 on the board is linked to LED “L” for a simple on-board access to a visual peripheral. In this case, the Arduino satisfies condition a) for Design for Serviceability.

The Arduino board has some ability to protect itself from electrical abuse. The gold part on the left in the picture is a resettable fuse which breaks the circuit if the current to the USB port exceeds 500mA. [2] At least for the power module, the board satisfies condition b).

On most versions of the board, the main ATmega368P chip is in a DIP package and attached to a socket, which makes the IC removable. If the original chip is damaged, it can be replaced. Also, the chip can be removed and placed in a final product once the prototyping phase of a project is over. Because the ATmega chip is a relatively common and easily sourced part, this section of the Arduino not only satisfies condition b) but also c).

However, all of the other parts are soldered onto the board. This makes replacing any part other than the main chip difficult and puts the board at risk of getting another part burned during the replacement. Moreover, many key parts of the chip are in a SMD (Surface Mount Device) package, such as the UART-to-FTDI converter chip and the power regulation module, which requires advanced soldering skills to remove and replace. This choice is made in order to fit the whole circuit on the standard Arduino footprint and allow the board to be compatible with older versions of the board.

In general, the ability to evaluate the logic on the Arduino board satisfies condition a). Moreover, as the parts used in the Arduino are overall very common and standardized, the board satisfies condition c) too. However, because many of the parts are in an SMD package and very difficult to replace, the Arduino board cannot satisfy condition b) as a whole.

Overall, the Arduino is adequately Designed for Serviceability, with some parts such as the ATmega 368 chip being very well Designed for Safety, but also with some sections only satisfying the most basic condition, like the power regulation module.

An alternative to improve Design for Serviceability on the Arduino would be a design with through-hole versions of the power regulation module, as they are key to keeping the whole board and its peripherals safe from being applied too much power. A through-hole package is easier to de-solder compared to SMD, and because the parts require a bigger solder pad size, the pins would also be more accessible for test probes.

Sources:

[1] Patrick Esposito. 2012, May 3rd. Design for Serviceability [Online]. Available: http://www.pddnet.com/article/2012/05/design-serviceability

[2] Arduino LLC. Arduino UNO [Online]. Available: https://www.arduino.cc/en/Main/arduinoBoardUno


Reading Response: Prototype Prototyping


In response to the readings "Prototyping, Iterating and Making New Things" by C. Milne and "Build a tower, build a team" by T. Wujec, I suggested a method for facilitating the creation of multiple similar products called meta-prototyping. The process involves treating the prototyping process as a product itself and using elements of the design process to design prototyping tools that can be reusable for many projects.

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I arrived to the concept while sketching out ideas for a blog theme for tumblr. I started using different ways to represent the idea using quick prototyping methods from simply drawing and annotating to using post-its. The whole process turned out to be not unlike the design models from the Praxis I course, from "Frame, Diverge, Converge, Represent" to the Pugh model.


This, combined with the concept of iterative prototyping introduced in Milne's reading, led to the idea that "meta-prototyping" can lead to a series of prototyping tools that forms a larger protytyping process which involves multiple prototypes of different fidelities, gaining information from each in order to refine a design.

Link to original slideshow

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Finished reading through the projects?

You can head on over to the next page to read the takeaway from my experiences this semester.

Take me away to the takeaway!