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Screwdriver Magnifying Glass
Prototype
The objective of this project was to work through the design process on a self-selected problem. The end goal was to deliver a 3D printed only prototype and FEA simulation
Identify Problem
Problem: It is hard for farsighted people to see small screws when using a screwdriver. Current magnifying glasses are too bulky or require two hands to operate
Current Solution Short comings:
•Design is bulky which makes it hard to store in toolboxes
•Can only be oriented to look down on objects – limited use
•Sometimes requires a hand to hold magnifier – reduces user comfort
•Many moving parts- not user friendly
Competitive/Benchmark Design Observations:
Metal clamps:
Requires a lot of sliding and rotating to orient magnifying glass into the correct position
Not sure if in practice the magnifying glass can be oriented into every required position
Base Piece:
Design is meant to look down at objects, presumably when placed on a table
Would not be able to use when looking up at a screw. Ex: working underneath a car
Manufacturing:
Metal, glass, and plastic used
Simplifying to an all-plastic design, including magnifying piece, is possible
Opportunities/Gaps
-> Improve ergonomics
-> Reduce size
-> Improve manufacturing
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Requirements and Specifications
Initial Requirements
Screw can be tightened with one hand while product attached <- Differentiator
Size of screw must look larger under magnifying glass
Product must work with common screwdriver types/sizes
Design can be stored in a common toolbox <- Differentiator
Magnifying glass can be pointed in any direction <- Differentiator
Use least amount of parts possible
Initial Specifications
Structural Integrity
Must not fracture under 1lb axial load when sliding on screwdriver shaft.
Withstand minimum radial load of 1lb
Magnification
Objects must be magnified by at least 2.5x.
Screwdriver Fit
Product fits #000, #00, #0, #1, #2, #3 Phillips head screwdrivers.
Product fits 1/8”, 5/32”, 3/16”, 1/4”, 5/16”, 3/8” flat head screwdrivers.
Size
Product does not exceed a size of 5”x5”x5”
Concept Selection
I quickly brainstormed a few concepts, but did not know which one to select. Based off of these criteria, I created a Pugh matrix to determine which concept to pursue. The magnifying glass with a "straw like slit" in the center concept scored the highest in the matrix, therefore it was chosen.
Ease of use- Does the idea have fewer moving parts or oddly shaped that can potentially confuse the consumer?
Size – Does the idea take up more volume?
Ease of Manufacture- Does the idea have a smaller part count and 3D printable?
Fit – Is the idea able to used with multiple size screwdrivers?
CAD Model
I created a CAD model to visualize the product and create the prototype to be 3D printed. There are two parts to the assembly: the magnifying glass for the user to see through and the "straw like" slit to accomodate many types of screwdriver shafts.
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Analysis of Concept
I analyized my CAD model with FEA (NASTRAN) to determine if the slits would fracture when sliding on the shaft of the screwdriver. For this simulation, I chose aluminum 6061 as the material for the slit piece. Aluminum 6061 was selected because it is a very ductile material that will last many uses for this application.
From the analysis it was found that the slits will not fracture while sliding on shaft. The Factor of Saftey and Margin of Saftey are extremely high, therefore a different material can actually be selected to optimize the design.
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Analysis Discussion
Shortcomings: This should be considered a preliminary analysis. The margin of safety is in excess of 3, therefore stress is not a concern. Factor of safety is over 9, which means this part is overdesigned. Material can possibly be removed if it is advantageous, or a different material can be selected to reduce cost. Analysis assumes a smaller screwdriver shaft diameter.
Analysis Improvements: Dividing the faces of the slits into different circle diameters before applying a load may closer replicate other sizes of screwdriver shafts punching through the slits. This model only includes one part; therefore, it may be important to include the whole assembly going forward to test other parts. The magnifying glass will require a separate analysis to test deflection and/or stress while sliding the product on the magnifying glass. This separate test would help determine if the magnifying glass will fracture while sliding or deform plastically thus reducing image quality of the lens.
Physical Prototype
Due to the scope of the project, the prototype was required to be 3D printed using ABS plastic. The finalized product would use acrylic plastic for the magnifying glass (shown in black) and aluminum 6061 (shown in orange) for the slit piece.
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Discussion
Manufacturing
Part Build estimate is 39 minutes or $32.50 at $50/hr. Assuming a 100% markup on the manufacturing cost, the retail cost would be $65. This cost would be too high for a single part as the competitive retail price for a magnifying glass holder is ~$9. The typical markup from manufacturing is ~%50 on a product which leaves roughly ~$32.5 for operating costs, packaging, marketing, etc. 3D printing is not a viable strategy; however, the magnifying glass can be made from acrylic plastic that is injection molded. The “straw like” slit center piece can be made from machined aluminum or a flexible plastic such as PET that is also injection molded.
Broader Design Impact
From a global and environmental perspective, the acrylic plastic lens can be recycled or melted down into new products. Aluminum lasts longer, is more durable, and can also be recycled; however, if a plastic is used for the center piece instead, then it must be biodegradable or recyclable to be environmentally friendly.
When considering economic and societal points of view, the product should be marketed towards an older audience and those who are farsighted. As this product receives a connotation towards older people, those who are insecure about their eyesight or age may not like to purchase or use this product.