1. The Unlimbited Arm Abstract Materials Results Procedure
Erika Bowen | Dr. J. B. Sharma, Forrest Ables, and Kathleen Hornick | University of North Georgia
Abstract
Materials
Results
Out of an interest in 3-D printing in the biomedical field, a research project was undertaken to determine the quality of the “UnLimbited Arm - Alfie Edition” prosthetic arm created by Enabling the Future. EnablingtheFuture.org provides open source files necessary to print an elbow-powered prosthetic for individuals in need. The research is designed to print the prosthetic based on Enable’s quality specifications and test its ability to sustain weight in order to access efficiency and quality. As a result of the study, an additional research component was added to deduce why Enable recommended PLA filament over the stronger ABS filament when printing. According to my findings, the arm lifts about 13lbs of weight, is easily customizable or adjustable to specific needs, and is printed in PLA because it is more flexible. Existing problems with the arm are not currently solvable due to the restrictions placed on this prosthetic by Enable’s specifications.
Materials
Quantity
Tensioner screws
(4) Pan head Phillips sheet metal screws #4 x 3/4” (4) Pan head Phillips sheet metal screws #6 x 1” (4) Pan head Phillips sheet metal screws #8 x 1 ¼”
Cord
(16 feet) 80 lbs strength braided fishing line
(10 feet) Flexible cord 1.0mm
(10 feet) Flexible cord 2.0mm
Elastic Bands
(100) Non-latex extra heavy grade dental bands 1/4" size (100) Non-latex extra heavy grade dental bands 5/16" size
Palm Screws
(15) Countersink head Phillips wood screws #4 x 3/8” (15) Countersink head Phillips wood screws #6 x ½” (15) Countersink head Phillips wood screws #8 x 5/8”
Foam Padding
(12" x 5 ¾”) 3/8” thick self-adhesive firm foam padding
Gel Finger Tips
(10) Size 3 Lee Tippi Gel Fingertip Grips
Velcro Straps
(10) Velcro straps, 12” long, 1” wide with buckle
Glow-in-the-dark Hatchbox PLA
(2) 1 kg Spool, 1.75 mm
TOTAL COST
$107.00
Part
Mass with Supports
Time Taken to Print
Cuff
98.24g
7h 1m
Phalanx
31.12g
2h 50m
Fingers
38.69g
3h 7m
Forearm
357.85g
1d 8h 40m
Palm
97.08g
10h 4m
Pins
17.58g
1h 26m
Jig
113.59g
9h 45m
TOTAL
754.15g OR 1.66lbs
66.88h
History of Prosthetic Limbs & enablingthefuture.org
Earliest evidence found in 18th Egyptian dynasty mummy who had big toe amputated and replaced with a wooden and leather toe
The first real attempts at wood, metal, and leather prosthetics materialized in the Greco-Roman period stemming from a need for more and more soldiers in a war plagued society
Roman General, Marcus Sergius was famous for fighting in 4 wars using an upper-limb prosthetic to hold his shield
He was denied priesthood because “it was held that one needed two normal handles to be a priest.”
Ambroise Paré invented both upper-limb and lower-limb prostheses
His ‘Le Petit Lorrain’, a mechanical hand, was utilized by a French Army captain in battle
Advancements in technology and medicine have significantly improved amputation and prosthetic need for society
Stigma around the disabled has also pretty much dissolved entering the 21st century
EnablingtheFuture.org and 3D printing attempts to answer the last lingering problem of cost and access
Since 2011, they have provided the means to cheaply produce upper-limb prosthetics and ship them easily to recipients in need without sacrificing quality
The arm can lift ~ 13lbs
Part
Mass(g)
Time
Cuff w/ PLA 35%
98.24g
7h 1m
Cuff w/ PLA 20%
64.08g
6h 45m
Cuff w/ ABS 20%
72.23g
6h 43m
Procedure
PLA is easier to thermoform and produces no weak spot in the cuff section at 35% infill density
How Does it Work?
First, measure length of hand and forearm of non-affected arm and circumference of affected upper arm
Step 1
Use Thingiverse Customizer to generate STL files then prepare them for printing in MakerBot Print or Afinia Studio
Step 2
After printing, remove supports and thermoform parts that need to be altered
Step 3
Lastly, string together the arm and adjust straps, tension, and foam placement for comfort
Step 4
Conclusion
Flexor tendons  pulls down on fingers
Strings
Extensor tendons  extends hand back out
Rubber bands
Power from the muscle are redirecting into mechanical forces in the elbow
The denser PLA filament was determined to be the best filament in this process of constructing the UnLimbited Arm – Alfie Edition because it is pliable at lower temperatures and its increased density holds vertices together better
This prosthetic is ideal for those living in 3rd world countries and children who are quick to outgrow their prosthetic but is not ideal for the average adult in its current state
Pins begin to pop off past the maximum weight and If an object tends to have a circumference larger than the hand’s closed circumference it becomes hard to hold so its pretty limited when it comes to cumbersome items
The maximum weight the arm can hold could drastically increase if the pins were replaced with nuts and bolts but the break away pins are apart of enablelingthefuture.org quality specifications and are put in place for consumer safety
This 1.66lb arm is lightweight compared to the average adult female arm which is around 10.7 lbs
A prosthetic obtained from specialist can range from $3,000 to $30,000 as of 2018 but this cost-efficient prosthetic only costed $ to build
For what it required, the UnLimbited Arm could change someone’s life
Works Cited
PLA vs. ABS Filament
12” x 1” Velcro Straps with Buckle (Qty 10). (n.d). 3D Universe. Retrieved from velcro-straps-with-buckle?aff=2
3D Printing Filament Guide 2017: ABS vs PLA vs many materials. (2017). 3D Printing Filament Guide. Retrieved from
Arifin, N., Hasbollah, H. R., Hanafi, M. H., Ibrahim, A. H., Wan Abdul Rahman, W. A., Che Aziz, R. (2017, October). Provision of Prosthetic Services Following Lower Limb Amputation in Malaysia. Malaysian Journal of Medical Sciences, 24(5),
Davies, S. [stephen davies]. (2015, December 19). UnLimbited Arm Release. Retrieved from
Davies, S. [stephen davies]. (2016, July 30). UnLimbited Arm Stringing Instructions. Retrieved from
Davies, S. R., Murray, D. (2017, March 14). The UnLimbited Arm v2.1 – Alfie Edition. Thingiverse Customizer [Software]. Available from
Desmond, D., MacLauchlan, M. (2002, December 2001). Psychological issues in prosthetic and orthotic practice: A 25 year review of psychology in Prosthetics and Orthotics International. Prosthetic and Orthotics International, 26,
Elbow Powered. (2018). Enable The Future. Retrieved from
Hagedorn-Hansen, D., Oosthuizen, G. A., Gerhold T. (2015, December 6). RESOURCE-EFFICIENT PROCESS CHAINS TO MANUFACTURE PATIENT-SPECIFIC PROSTHETIC FINGERS. South African Journal of Industrial Engineering, 27(1),
How To Succeed When 3D Printing With Nylon. (2014, September 23). MatterHackers. Retrieved from
Learn The Basics of 3D Printing. (2018). MakerBot. Retrieved from
Nagaraja, V. H., Bergmann, J. H. M., Sen, D., Thompson, M. S. (2016). Examining the needs of affordable upper limb prosthetic users in India: A questionnaire-based survey. Technology and Disability, 28(3),
Phoenix Hand by e-NABLE Assembly Materials Kit. (n.d). 3d Universe. Retrieved from
Prosthetic Costs. (2017, February 20). Disabled World. Retrieved from world.com/assistivedevices/prostheses/prosthetics-costs.php
The All-New MakerBot Print. (2018). MakerBot Print (Version 2.8) [Software]. Available from
The UnLimbited Arm v2.1 – Alfie Edition. (2016, July 14). Thingiverse. Retrieved from
Thurston A. J. (2007, December). PARÉ AND PROSTHETICS: THE EARLY HISTORY OF ARTIFICIAL LIMBS. ANZ Journal of Surgery, 77(12),
Tips For Successful Prints. (2018). Enable the Future. Retrieved from enablingthefuture.org/resources-2/tips-for-successful-prints/
What Material Should I Use For 3D Printing? – Advanced Materials Review #4 – Glow in the Dark Filament. (2016). 3D Printing for Beginners. Retrieved from
In order of decreasing quality
Distorted arc
35% infill PLA
(recommended)
20% infill PLA
Smooth arc
20% infill ABS