Product Design Challenge:
Shot in the Dark
The Mystery Machine
For the main design challenge project of this capstone course, TheCreo team designed and built Shot in the Dark: The Mystery Machine, an automated and randomized drinks dispenser and cocktail creator. The machine serves an 8oz. cocktail within seconds, mixing 2 of 11 drinks together in different proportions.
This design was chosen through a thorough selection and review process and design phases which are discussed below.
Brainstorming 240 Needs
To kick off the product design challenge, each team member identified 20 unmet needs which could each be solved through 2 mechanical design solutions. A wide range of product proposals were posited by the team members which ranged from whimsical to serious. Designs included mobility aids for wheelchair users, dual purpose writing utensils, air cooled athletic wear, a fire distinguishing system, and more. During the team meeting, each member presented their own top five needs, which were then narrowed down to five needs for the entire team.
The five top unmet needs identified by the team were the following:
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Preventing snow and ice from infiltrating shoes
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Bringing fun and novelty to any party
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Measuring liquids accurately and easily without measuring spoons or cups
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Sorting bolts automatically by size
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Keeping hands of diabetic individuals warm
Three Needs Review
For the next phase of the design and selection process, these five semifinalist ideas had to be pared down to three preliminary designs for review. The two designs which were eliminated were the snow covers for shoes and the hand-warmers for diabetic individuals on the basis that they were the least creative needs out of the five. The six members of TheCreo worked in pairs to further develop design proposals of the three remaining ideas.
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Liquid Measuring Cap: Nizar and Francisco
The Liquid Measuring Cap was designed to assist in the measurement of oils and sauces in the kitchen, especially for individuals with limited mobility or motor capacity. Rather than fussing with a measuring spoon, this add on cap contained a marked chamber and a set of two valves. By inverting the bottle with the lower valve open, the chamber could be filled to the desired quantity. Closing the lower valve and opening the top valve would let the liquid be poured out.
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Automatic Bolt Sorter: Raj and Mike
The Automatic Bolt Sorter was a portable, motorized device capable to sorting bolts by head size into corresponding containers. A series of belts first received, aligned, and fed bolts single file into the sorting mechanism. In the sorting mechanism, a set of diverging belts sorted bolts on head size based on when the bolt would fall through the widening gap.
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Mystery (Shot) Machine: Chris and Alvin
The Mystery Machine was a tabletop sized Arduino controlled drinks dispenser and mixer powered from a wall socket. An air pump forced air into the bottles selectively through solenoid valves, and the liquid would be conveyed up a feeder tube into the mixing and dispensing nozzle. This air pumping system was selected to prevent contamination of the drinks to/from the motors or valves because the liquid only contacted the feeder tubes.
For the presentation itself, each pair had to clearly identity and discuss the need, the functional requirements, and the solution in a short 2 minute pitch. As a result of the review presentation, the following decisions were made for the product design challenge. The Liquid Measuring Cap was eliminated from the finalist designs because it was considered too simple for the scope of the challenge. The Automatic Bolt Sorter and the Mystery Machine were well received, one for its utility and the other for its whimsy. These two designs were selected as the finalist designs slated to proceed to the Sketch Model prototype phase.
Sketch Model Review
For the Sketch Model Review, each half of TheCreo team was required to construct a Sketch Model prototype which would explore and showcase the high level design and specifications of the product. Each sub-team needed to provide evidence and calculations that their design would function, such as doing torque or fluid pressure analysis in EES. Additionally. the sketch model would show the scale of the product, the overall design and mechanical solution, and serve as a vehicle for understanding the challenges and capabilities of the solution with a focus on proving that the design and solution were viable. TheCreo team worked in groups of three to perform the necessary analysis and construct the sketch models of the two finalist ideas.
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Automatic Bolt Sorter: Raj, Mike, and Alvin
The Automatic Bolt Sorter used two sets of belts to support the sorting and feeding mechanism. The first belt, inclined against a a near vertical plane used gravity to align the bolts axially with the direction of the belt. Because a reliable automatic loader was not able to be designed, the sketch model required that the bolts be loaded by hand individually onto the feeder belt. The aligned bolts then fell onto the narrow V diverging belts, where the shank hung into the gap, supported by the head on both sides until the head fell through the gap into the appropriate container. The entire sorter was about 4ft long, 2ft wide, and 1ft tall, and was constructed from plywood, acrylic, dowels, and canvas belts.
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Mystery Machine: Chris, Nizar, and Francisco
The Mystery Machine prototype was constructed such that the liquid pumping mechanism was actually functional. The entire machine was built into a custom 1/2" thick cardboard shell about 2ft wide, 3 ft tall, and 1ft deep. A dispenser and nozzle was located about halfway up the front of the machine. Inside the shell were a series of 2 liter soda bottles. Straws were used as feeder and air supply tubes; by blowing into the bottle via the supply straw, water was forced up the feeder straw into the cup in the dispenser module. Parts such as the pump and the valves were represented with cardboard forms glued inside. At this point, the Mystery Machine was nicknamed A Shot in the Dark.
As with the 3 Needs Review, both sketch models were well received. The primary criticism provided was that the bolt sorter did not have an automatic loader and that this should be incorporated. As a result, this became the deciding factor in choosing the Mystery Machine as the finalist idea because TheCreo team did not wish to pursue designing the automatic loader. Additionally, the greater variety of tasks such as programming and testing would allow team members to contribute from outside the lab.
Critical Function Review
While the sketch model was intended to give a general review of the solution and design, the Critical Design Prototype was intended to demonstrate the mechanical functions that make up the solution and prove that the product can work reliably and function well. Owing to its sturdy construction, the cardboard shell was reused for this prototype. All the cardboard mockup components inside were removed in preparation to receive the actual components. The source of the air pressure came from a 10W aquarium pump. Air was fed through food safe tubing past a bleed valve to a distribution tree of two valves to two bottles. The air supply pips were put through one of two holes in the bottle cap. The other hole held the feeder tubes which reached to the bottom of the bottle and conveyed the drink up to the dispenser nozzle. The prototype had a basic electronics package to control and power the system. The air pump was powered from a standard 110V wall socket. An Arduino Mega powered by a LiPo battery pack controlled the opening and closing of the selector and bleed valves. The bleed valve was used to dump air pressure when dispensing was complete to prevent residual fluid flow. Because the valve's current draw exceeded that of the Mega, a relay board powered by the same LiPo allowed the Mega to control the power to the valves. Finally the entire system was controlled by a bumper switch on the front of the machine.
For the review presentation itself, one bottle was filled with blue water and the other with yellow. Placing a cup in the dispenser and pressing the button would give a blue, yellow, or green drink. Any spills were captured by the integrated drip tray. The entire prototype worked extremely reliably and was very well received.
Compressed air pushes liquid through feeder tubes
Liquid from three bottles converge at dispenser to cup
Working prototype during review
Compressed air pushes liquid through feeder tubes
CAD Modelling
As the design solidified, the Shot in the Dark was modelled in CAD, specifically in Creo. TheCreo team divided up the different components and each member contributed to designing and drawing parts as well as making the final assembly drawings and diagrams.
Constructing the Alpha Prototype
Compared to the Sketch Model, the Alpha Prototype underwent a number of stylistic changes but the fundamental functions work the same as in the sketch model. After analyzing the placement of the different components, TheCreo team revised the positioning of the components within the Shot in the Dark to reduce the overall height. The dispenser was moved down to replace one of the bottles, giving the final 11 bottle configuration. The main shell was constructed from CNC'd and sawed panels of black 1/4" ABS plastic, secured with brackets and bolts. Smaller components such as the drip tray were glued together with epoxy. Initially, the outer shell was to be glued with epoxy as well but it was found to be too weak. In the Alpha prototype, the compressor has been moved to the rear of the machine for optimal cord placement, and the relays and Arduino board have been enclosed within an electronics box. All tubing has been replaced with higher quality tubing that can withstand conveying alcohol, and universal rubber bottle caps allow many different types of beverage containers to be used.