Gimili's Gauntlet
Abstract
The potential clients in question are mainly afflicted with the dwarfism birth defect. This ailment can be a limiting factor for parameters such as mobility, strength, and reach in the the arm, wrist, hands, and fingers. A mechanical appendage such as an exoskeleton or a gauntlet could be developed to relieve some of these inhibiting factors and reduce the stress of performing daily tasks that would be otherwise simple to the average individual. The device will fit over the individual in question and will be controlled or "puppeteered" by the user. After presenting some initial designs, the best candidate will be chosen based off of ease of use, functionality, life span, and repairability. Afterwards, the design with be modeled in CAD software and be 3D printed; other necessary parts will be ordered. Finally, the project will be assembled and ready for presentation in the open market.
Team members
Team member names from left to right: Jonathan Matlock, Micah Hardyman, Drake Johnson, Sean Harvey
Problem Statement/overview of the need
Design and produce an assistive reaching device that will assist with increasing arm reach, mobility, and grip relative to some other assistive tools on the market.
Design Specifications
1. Relatively light in weight; around 2 lbs. ("loaf of bread")
2. Nearly double the reach of the user
3. Allow better grip dexterity (Fingers for more points of contact, finger spreading action)
4. User friendly (Easy to puppeteer? Easy to fix?)
5. Easy to transport
Background research
This is an example of an assistive reaching device that is currently out on the market. Surprisingly, this design is the most commonly available and really the only base design available via the internet . Buying from separate companies yields very little difference in the mechanism except some variation in aesthetics and the brand name label. As you can see, the design of the device is relatively simple; an aluminum rod with a handle grip that is connected to a claw at the end with a single pinch point and some silicon padding. These devices are relatively inexpensive ranging from $10 up to around 30$.
This device barely gets the job done while barely emptying the checking account. Its simplicity can bring up some issues which our project will expand upon and attempt to remedy. For example, the grip on the handle-claw device is basic and linear with only one point of pressure, which guarantees minimal grip and relies heavily upon the coordination of the user. A simple everyday task like grabbing a plate from up high could turn into a near surgical process. The greatest improvement that the Gimili Gauntlet wishes to bring to the table is the replication of the human hand in the grip which allows for a more dynamic and mobile grip due to "fingers" which can conform to the object in question and increase points of contact and confidence of the user.
Conceptual Design
Design Concept 1
Pulley telescoping mechanism, prismatic cylinders, ball in socket joints.
Design Concept 2
Spring return mechanism for the finger
Design Concept 3
Reach extension by pneumatic cylinders. Similar to telescoping mechanism just a different arrangement.
Evaluate concepts/select candidate
All three design concepts were reevaluated so that a fourth and final design may be constructed.
Design 1: Hand concept would be too difficult to create due to the complexity of individual inputs in each finger along with the excessive mobility permitted by the ball and socket joints; would be impossible to produce a prototype within the time constraint; complicated input mechanism. Sliding prismatic cylinders for telescoping difficult to model.
Design 2: Spring return mechanism is effective and pulley system input inside the device would be rather effective for amplifying grip strength. However, like "Design 1," this is difficult to model and produce within the allotted time frame. Assembly of input mechanism within device is extremely complicated. Would require some sort of bulky housing which defeats the purpose of dexterity.
Design 3: Reach extension by pneumatic cylinder for telescoping; similar to design 1. Individual input for each of the 5 fingers. Basically another overcomplicated design that is unlikely to be finished or properly functioning within the time constraint.
Detailed Design
This section will describe a detailed design process
Description of selected design
All 3 design concepts were completely reevaluated to compose a fourth and final design. This is a much more simplistic design with a one input trigger mechanism that controls five fingers. The fingers are made out of a relatively new and elastic 3d printing material known as NinjaFlex. Fishing line is ran through 2 feet of PVC from the trigger to the fingers for puppeteering.
Detailed description of selected design
1. Ergonomic arm brace with slots for velcro to allow more of an anchor to the user and feels like there is more control and stability
2. Handle Trigger Mechanism with fishing line running through fingers for 1 input that will close and open all 5 fingers.
3. Material composition will mostly consist of ABS plastic, however parts of the finger will be made with Ninja Flex mostly at the joints. This elastic material eliminates the need for any sort of return mechanism.
4. Purely mechanical motion and translation with the angular displacement of the trigger equalling the displacement of the fingers; minor torque loss
5. Does not rely on springs for a return mechanism
6. 5 fingers all the same length. 1 input controls all fingers. Fishing line ran through finger and knotted at the tips and then tied to the bottom of the trigger.
7. Sturdy enough to handle average 2 pound plate. Deflects .5 inches at 7 lbs so mostly ideal for anything under 5 lbs.
8. Sling added to allow easy transport of the device.
Analysis
Engineering analysis 1
Mechanism Modeling Analysis of fingers and thumb. Rectangular 2 Point Contact 2-D Geometry.
Engineering analysis 2
Stress Analysis of Finger and arm at 3 psi
Engineering analysis 3
Deflection analysis of the PVC pipe for 4 different cases of load application
CAD Drawings
Bill of Materials
qty, item, description, source, part number, price
1, PVC Piping, 10 feet 1 inch diameter;part of "forearm", Lowe's, $3.67 (Was provided by school Machine Shop)
1, Marine Grade Velcro Strap, 3 feet, adjustable strap for gripper, Walmart, $3.56
1, PLA Reel, 3D Printing Material, Makerbot, ~$40.00
1, Gorilla Glue, Adhesive for attachment of parts, Lowe's, $5.00
1, Omniflex 50 lb. Test Fishing Line, String for input into appendages, ~$3.00
Assembly Instructions
Construction of the design was easily accomplished primarily using Gorilla Glue and clamps, though the PVC was secured firmly using only a press fit into the body. Assembly began by attaching the handle and the arm brace to the main body using Gorilla Glue and clamps. After the glue cured the trigger was pinned into place and filed down for ergonomics. Next the collar that attaches the PVC pipe to the body was filed to shape so that a press fit was all that was needed. It was then attached to the body using the same method as the handle. The PVC column was then fitted and glued to the base of the hand. after the glue cured the column was press fitted to the body. The construction of the hand was then started by holding the body still as the fingers were glued and clamped into place. Then the fingers were strung and attached to the trigger by looping them together in a way that ensures slack is only drawn from the fingers that can move. finally a sling was looped onto the column and screwed to the body for easy transport.
Fabrication Process
Testing and implementation
Testing involved using the device to move and place objects of varying dimensions and weights at different elevations. By this method many positive characteristics were found, such as its grip strength and dexterity. It was also found that it has a high success rate at grabbing objects of complex geometry though cylindrical objects are far more cumbersome. As for the grip strength though we were unable to increase it was found that it still more than sufficient to grasp any thing tested. The current scaling of the devise is also well suited to out testers, seeing that if held downwards the total length ends just before the floor allowing great ease in picking things up off the ground while still maintaining good reach. Lastly it has proved to have good reliability in lifting or lowering objects without dropping or slipping.
Photos of Completed design
3D Printing
Some of the parts were printed and include ABS and Ninjaflex.
ABS
Most of the ABS parts were printed on the Replicator 2X by makerbot in the iMakerSpace (iCUBE). There was also an attempt to print parts out of a flexure material made by makerbot for their printers however; it was decided that the material was not nearly elastic enough to efficiently use the product.
Ninjaflex
For this project we decided to use Ninjaflex; a material used in 3D printing as a formulated thermoplastic elastomer (TPE). Trial and error is a large part in getting this to material to work. Not much is known about working with this material because of how meticulous the process of getting it to extrude, stick to the plate, get it to cool efficiently, and what the resulting material will produce in terms of elasticity. Here in this .zip file for an M2 - Makergear in the iMakerSpace (iCUBE) is an .ini file developed during this project to produce the knuckles; while leaving the fingers ABS.
Instructions for safe use
Provide a clear summary of safe use for the family. Do not use the device unless supervised by an adult that has been fully understood the safe use of this product.
Project Summary, Reflection
The design and prototyping that lead to the successful design were highly beneficial. The design was changed several times throughout the process allowing us to see how projects evolve through the prototyping process. In the end we were pleased to present a very stable and useful prototype that demonstrated our ability to build a fully functioning design.
