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GKS Inspection Services Advances Life-Enhancing Product for Partial Finger Amputees
 The Company
The company is a small privately owned company that designs and fabricates active-function artificial finger prostheses for partial finger amputees. The owner refined the design for over 6 years before he took it to the marketplace. The device is body-powered, light-weight, and allows users to regain complete control of the flexion and extension movements of an artificial finger in a self-contained device. Each finger is custom fabricated to accommodate a variety of finger amputation cases. “Our current direction is to use emerging technologies to improve the lives of people who have lost fingers,” said the owner. The U.S. Department of Defense is funding the company’s research into a functional thumb. The owner holds patents for the
prosthetic finger technology in over 140 countries.
The Challenge
Because most artificial fingers in the past were cosmetic, not articulated and not functional, the owner wanted to combine the most realistic look with the most realistic action. In addition to being functional, he wanted to insure that each finger prosthesis was custom fit to the amputee’s hand, something that is very hard to standardize. Both the number of fingers needed and the size of the hands can differ, making the number of assembly permutations practically infinite. He needed a faster and more accurate way to measure each individual hand so that he could provide the best design and fit possible, as well as timely service. Since the prosthetic finger moves through the muscular movement in the remaining fingers, hand, or wrist, and not batteries, customization was essential to the functionality of the product. Articulation was necessary to give the hand full finger dexterity and function.
 Realizing that in order to create prosthetics for a wider marketplace he needed the digital CAD models that are used in manufacturing, the owner taught himself CAD and recreated his physical designs digitally in SolidWorks. This was excruciatingly time-consuming and because each customer needed a totally new set of specifications, the time involved and the pricing became prohibitive.
The owner explains, “A lot of research and development is being devoted to making functional artificial arms, but the technology stopped when people only lost fingers.” His design links portions of the hand and fingers together so that they work naturally as a unit. The problem was not making the finger look real, cosmetically identical fingers had been made for years, but functional and realistic fingers were new to the scene.
The owner began to search for a quicker and more accurate way to generate the hundreds of measurements he needed to create just one custom hand prosthetic. He found GKS Inspection Services, a division of Laser Design, Inc., through an Internet search and contacted Larry Carlberg, GKS Service Bureau Manager about the possibility of doing a test scan on two small woman’s hand casts that he was working on.
The Solution
Carlberg knew from
his decades of experience that non-contact laser scanning would provide
the ideal solution to the challenge of digitizing the complex natural
shapes of an amputee’s hands. He commented, “Freeform shapes are
ideal for laser scanning, since it is impossible to capture these
organic shapes in any other manner.” Because the laser scanning system
projects a line of laser light onto surfaces while cameras continuously
triangulate the changing distance and profile of the laser line as it
sweeps along, the problems of missing data on an freeform, irregularly
shaped surface is eliminated. The system measures fine details and
captures complex geometry so that the object can be exactly replicated.
Laser scanners quickly measure articles, picking up tens of thousands of
points per second, and generating huge numbers of 3D data coordinates
without the need for templates or fixtures.
 To scan the two
hand casts, Carlberg used the Laser Design Surveyor 3500 3D laser
scanning system with a Pentium 4, 3 GHz processor with 4 GB RAM and a
specialized video card. The laser probe used was an RPS 450, since it
has a deep depth of field with good accuracy. He performed multiple
scans mounting the casts on the Aerotech rotary stage to capture 360
degrees of the casts’ geometry. The Laser Design 3500 machine setup is
automated to merge multiple scans into a single point cloud using the
rotary stage integrated with the native data collection software
Surveyor Scan Control (SSC).
The casts each took
approximately one hour to scan. Compared to manually measuring, the
time savings are enormous. “The process of laser scanning cut 60% off
the time it took to make enough accurate measurements of the hand casts
to create a CAD model,” said the owner. “With over 600 different
variations of each finger-hand configuration, such as how much of the
finger is gone, which fingers are gone, and so on, plus six different
hand sizes, getting the correct measurements is an incredibly
labor-intensive task with manual measuring tools. The speed and
accuracy of laser scanning allows me to standardize assemblies and sizes
and make all the parts interchangeable. In the future, this will reduce
the cost, increase availability and make the process easier and faster
for the benefit of the amputee customers.”
“I can’t think of
an alternative to 3D laser scanning that would provide similar results.
The geometry is just too amorphous to capture without laser scanning,”
Carlberg added. “The output we delivered for these parts is highly
accurate since we create the solid models directly from scan data. The
accuracy of the point data is .002” or .05 mm of the actual hand
cast. To achieve a model of freeform shapes with this kind of accuracy
is impossible by any other means. With such an accurate definition of
the actual hand, the company can fit a prosthetic device perfectly.”
The company owner
agrees. “In the past, hand prosthetics relied heavily on a fabricator’s
artistic ability and creativity. They were visually realistic but not
functional with articulation and mobility. Now technology is catching up
and complexity is increasing so that not only does the prosthetic look
realistic, but it acts realistically too. All our complex components
are hinged in more than one place so organic hand movement is
duplicated. The residual parts of the fingers stabilize the prosthesis
and the grasping functionality is speed-regulated like a real hand’s.
The technology is available today is unbelievable. It has given rise to
a new profession, the anaplastologist, a career which has actually been
around for over 20 years, but now has its own advanced tools rather than
‘making do’ with materials used in the special effects industry.
 “Today, the
realistic look and movement can all be created through measuring and
duplicating technologies. It is quicker, cheaper, and provides better
access to people all around the world. This is an exciting time for the
prosthetics business. Every day we find out new ways that technology
can aid us.”
The Results
“The files were
perfect,” said the owner. “They imported as solids into SolidWorks, and
I was able to do cross-sections and use the side views, which is
essential to creating custom prosthetic finger assemblies.” GKS’ expert
metrologists made the 3D scanning process quick, accurate, and
cost-effective from start to finish, allowing the owner to completely
bypass time-consuming manual measuring. Laser scanning brings the
custom fabrication process for prosthetic fingers several steps closer
to being an off-the-shelf product. “Our company has the most
technologically advanced artificial hand/finger in the world. It fills
a huge gap in the prosthetic industry for finger amputees.” The owner
input the custom data into SolidWorks and fabricated components
customized for that individual’s hands.
The extreme speed
and accuracies of the point data (002” / .05 mm) are typical for GKS’s
work in this type of application. “The success of this story describes
a unique application of utilizing a very fast an accurate scanning
system with an ideally suited software (Geomagic Studio) for developing
quick models of amorphous shapes,” explained Carlberg.
 The owner
concluded, “What you gave me was exactly right. The GKS metrologists
provided all I had hoped for in the scan data and more. I am totally
happy with the results.”
About GKS
GKS Inspection Services has been a leading provider of dimensional inspection, 3D laser scanning and terrestrial scanning services for over 25 years. The company’s Plymouth, MI lab (Detroit metro area) is accredited by the A2LA for Mechanical Testing and Calibration and features numerous CMMs, vision systems, 3D laser scanners, surface analyzers and other inspection equipment. GKS also has U.S. offices in Minneapolis and Seattle and international locations in India, Korea, China, Taiwan and the Netherlands. The company’s metrologists and engineers are experienced in the automotive, defense, electronics and many other manufacturing industries.
More Information
For additional information about how GKS Inspection Services can improve your manufactured product, save you money and decrease your development time, call
Larry Carlberg at 952-252-3432 or send email to
measure@gks.com
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