Ashley Lowber
Mechanical Engineering Portfolio
Designed in a two-person group, this product was inspired by the challenge to create an item using a bi-stable mechanism. The Busy-Free Indicator gives a clear signal regarding the availability of the user -- either they are busy/occupied or free/available, and they can convey this message easily to others. This can take shape in the context of an office (for instance, the user is in a meeting and needs to place the toggle indicator outside their door so that no one enters, or they may place it on their desk with the switch pointed to “free” so other employees know they aren't currently occupied). In further iterations of the product's use, students are able to effectively communicate to their roommates whether or not they should enter a dorm room, or Residential Assistants can indicate to their residents whether or not they are busy working on a problem set. All of these situations, as well as other similar scenarios, revolve around a binary “yes/no” status, which the user can self-select. Our design clearly displays this status both from a close and far range, thanks to the stark contrast between the wood and the negative space).
Busy-Free Indicator: A Bistable Mechanism
The Process: Sketching
My partner and I began the process of brainstorming by considering who our user base would be. As college students, we sought to design a product applicable to the lives of our peers. In discussing several problems that we could tackle, we landed on the idea of using an instrument to indicate the availability of our user in a given scenario. Many of our original ideas were very close to the final product. However, in the first round of sketches we brainstormed different orientations of the mechanism- horizontal, vertical, and diagonal- which would affect where the switch would be placed and how the shutter would move. Originally, we also planned to use lights (a red one behind “busy” and a green or blue behind “free”). Other concepts included a display based on a tug-of-war game or providing a message utilizing a more complex light display.
My partner's sketches
We decided that the simplest design would include a bi-stable toggle mechanism hidden by the anterior wall. This mechanism would allow for the user to manipulate a switch to reveal either of the two words indicating the user's availability to their target audience.
My sketches
Prototyping
The rapid prototyping process allowed us to get a better grasp on how to implement the idea we had selected: a bistable mechanism using a compression string that would allow for the user to operate a switch on the side of the box. One of the main weaknesses that prototyping exposed was the difficulty in adding the shutter to the mechanism. Although attachment directly to the mechanism proved to allow movement of the shutter, this movement was arced and gave the shutter free range of rotation, which we would have to address in the final product. One of the other aspects of the piece that we noticed was the limitation in the size of the rod around which the spring had to fit. These observations gave us a better sense of what the dimensions of the final product would be.
Redesign
We wanted to make sure we could implement this mechanism in a box with real pivots. Taking the advice of the teaching team, we attached mounts to the sides of our box to support the switch mechanism, and modelled a dowel which could support a pivot at the end (so that we could use a shoulder screw). We sketched a tentative redesign with a primary list of materials, using dimensions based on our prototype.
The redesign incorporated the following changes:
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Mounts attached via screws and tabs, not adhesive.
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Tabs and captured nuts on box faces.
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A handle which clamps around both ends of the dowel.
Finally, we needed to replace our straw and paperclip with another mechanism that would allow the rods to slide linearly along each other.
In addition, we created a CAD model of the parts and the overall assembly as the primary verification of functionality. We included a Bill of Materials.
Construction and Final Assembly
The process of building consisted of 3D printing, laser-cutting, and assembly. We used the Ultimaker 3 with Tough Black Resin (our design did not require any supports) to create a rod small enough in diameter for the spring to easily fit around with room to slide. The laser-cutter was used to build the three walls of the box, including the cut-out of the words, as well as the switch, stoppers, and supportive components. One of the main issues we faced with the design of our device was in correcting the rotational freedom of the shutter. The dowel featured in the left photo was eventually dowel pressed into the shutter, which was restricted by both the nature of the switch mechanism as well as wooden stoppers we placed at the top and bottom of the front wall. Secondly, it was difficult to get the rod (with the spring wrapped around it) to fit into the supports. As a result, we had to file away at both the 3-D printed rod, the supports holding the rod and the dowel, and the supports connecting the mechanism to the wall.
The Final Product
One of the aspects of the design that turned out very well was the way in which the direction of the switch (pointing up or down) would indicate which word was revealed, and therefore the user’s current status. The clean cut of the letters and easy-to-manage switch also made the mechanism practical and aesthetically pleasing. The dark color of the wood used for the front and for the shutter additionally makes the status of the user very evident.
