Date: Feb 12, 2010 Source: Todays Machining World (
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For nearly two decades, Ron Farquharson was just plain frustrated with his body-powered prosthetic arm. Sure, it seemed like state-of-the-art to some, since he was able to hold jobs and get around like a "normal" person. "But what Ron really liked to do was cook," said Farquharson's friend, Johnnie Rouse, somewhat laughing at the thought. "There was no real safe way for someone with a hook or a battery-powered arm to hold knives, or at least no really easy and effective way of doing it."
Farquharson had lost his right lower arm in an industrial accident in June 1971. Fifteen hundred pounds of hydraulic press fell on his hand and crushed it. Doctors fitted him with a prosthesis with a number five hook on it. Farquharson learned how to use it well, but as time went on, he figured there had to be something better. His friend, Rouse, had a machine shop, and by the mid-1980s, encouraged Farquharson to come up with something that was better, since no one else seemed to be moving that way.
"Ron came to the shop with some drawings and I thought, "I can do that‚" he said. "So we worked on it and soon we had the N-Abler. I would guess that is the story of all successful inventions."
Though exact national figures are hard to come by, it is clear that amputation, and thus the need for prosthetics for arms and legs, is increasing. A New York Times story earlier this year said that by February of 2006, 387 soldiers had come back from Iraq as amputees.
"Whether it is because of the Iraq War or just the aging of the baby boomers and the propensity for older people to lose limbs from diabetes and other diseases, there is just more of a need for these products," said Joanne Kanas, a certified prosthetist/orthotist, the professional who fits amputees for their prosthetics and sometimes constructs them. She works in the Linwood, New Jersey, office of Hanger Prosthetics and Orthotics and, as such, sees many new and old products.
The machined parts of the prosthetics, she said, can be quite simple or as complex as a small computer, depending on the device. In recent years, some prosthetics have become electronic, which requires processors and wires and equipment equivalent to that used in EKG machines. Yet even with that amount of sophistication, many of her clients opt for old-fashioned -- sometimes jury-rigged -- mechanical devices.
Take, for instance, Mike Sciullo, who lives in the quite beach town of Brigantine, only a couple of miles north of the cacophony of the casino Mecca of Atlantic City. Twelve years ago, soon after coming home from a hard day at his photography business, Sciullo, then 67, fell asleep and went into septic shock. By the time he woke up from a coma in the hospital eight weeks later, his extremities had lost too much circulation, had developed gangrene, and had to be amputated. His right hand has a wrist, but no fingers, while his left arm is incomplete below the elbow. His legs are lost below the knee.
Thus, he has three different types of prosthetics. His left arm has a hook and his legs are plastic-covered with interior mechanical parts. His right arm has a clapper-like device with a stainless steel hinge and copper rivets and burrs to hold the device together, with a simple Velcro to attach it to a support around the wrist. The flap acts like a thumb, but has several settings depending on how tightly Sciullo wants to grasp something.
"The copper sometimes oxidizes because I use it so much, so maybe that wasn't the greatest idea," he said. "But I got used to it and you do not want to change what works."
"Sometimes it is like that," she said. "If you are an amputee, you are a client for life. If you are a normal person and turn a knee and it gets rehabbed, you may never go to the doctor again. Once you have a mechanical item, though, it wears or gets broken and you have to come back. That doesn't mean it is complicated machinery. Sometimes it is just rivets from Home Depot."
Or sometimes it is workmanship from a lone machine shop -- Johnnie Rouse's, for instance.
Rouse makes the Texas Assistive Devices -- that's the name of the company Farquharson now owns -- N-Ablers primarily on three CNC mills and two CNC lathes. The N-Abler V, which is the successor to the first four versions of the artificial hand device, is somewhat like a wrench set. A metal wrist-like device hooks onto whatever stump of the arm is available. Then there are different kinds of inserts that go into the "hand" end of the device, depending on what the wearer wants to do. Farquharson's favorite is his cooking knives.
"I've always like to cook and I couldn't do it. I just couldn't feel I was safe," he said. "Now my hand can become like a knife."
Depending on what the amputee needs, Rouse will mill it. It could be a hook or a thumb-finger or even something for recreation.
"We have made fishing rods to go in the N-Abler. It can be anything, so long as it has the proper tolerance and strength," said Rouse.
In the last decade, much of the prosthetic market has gone to using high-strength aluminum and titanium, since they are lighter than stainless steel -- the more traditional metal in mechanical prosthetics -- and are strong as well.
"We tend to use an aircraft grade of aluminum, perhaps 70-75, which is low weight and high tensile strength, sometimes stronger than commercial grade titanium with one-third the weight," said Rouse.
Even in myoelectric arms, like the Utah Arm created by Motion Control, Inc., of Salt Lake City, the aircraft grade aluminum is the standard for most mechanicallymachined parts.
"We have made attempts to do machined parts in plastic, but it has not been successful," said Harold Sears, the president of Motion Control. "The strength to weight ratio is not good enough, and the plastic is too brittle when it comes to something people use a lot, like a prosthetic arm."
Machinists make molds at an in-house factory for most of Motion Control's products, said Sears. The Utah arm, because it is controlled by electronic sensors, has 916 parts, but much of that, he said, is circuitry and not machined parts.
"On the other hand, it is a bit of an urban myth that electronic parts are replacing everything in prosthetics," said Sears, even though he manufactures those sophisticated electronic parts. "It is difficult to make an arm that is right for all occasions, and sometimes it is the older styles that are just right."
In some cases, the prosthetics in use today are still a vestige of what was state-of-the-art in the middle of the 20th Century. There was a lot of research done on prosthetics during and right after World War II and the Korean War. Soldiers were coming home limbless and there was a social and practical need to find the best way to make them whole again.
Plastics and some carbon compounds were gaining in manufacturing of all sorts, but the primary material for prosthetics was stainless steel. The military, which was doing much of the research, was not into style. Most artificial arms and legs of the post-World War II era were strictly poles and pincers. They had easily-machined parts and it was mostly a one-size-fits-all scene. Stainless steel was durable if sometimes cumbersome, but it worked, and subcontracting parts was simple, since there weren't many of them on each arm or leg. If a prosthetic allowed someone to walk or at least open a door, and it didn't come apart too often, it was deemed good enough for use.
"Sometimes it wasn't as sophisticated as that," said Sarah McConvill, a development engineer for Otto Bock Health Care, one of the largest prosthetic manufacturers in the world, based in Germany but with facilities in Utah and Minnesota. "You often went to the prosthetist and he or she would take some big pieces of wood. The art was carving it down for a custom wooden prosthesis and using belts or straps to keep it on the stump. It was just an external wooden element that mainly acted for support. It was not very functional, but it filled the pant leg and allowed the person to walk."
After the Vietnam War, though, according to Texas Assistive Devices‚ Rouse, research on artificial limbs went dormant.
"Universities had other things to do and, frankly, there wasn't all that much of a market or a constituency to have better products," said Rouse. "It certainly wasn't sexy to be looking for a better artificial leg at the time."
Yet like much else in the economy, the baby boom started to have an effect on the market. Diabetes and accidents and other traumas started happening to them, plus the Vietnam veterans, who were much more vocal than their World War II and Korean War counterparts about veterans' benefits, wanted better choices for artificial limbs.
"The next big jump came in the late 1980s, when there were a couple of people deciding that these cool space-age carbon-fiber reinforced composites could be applied to a prosthetic foot," said McConvill of Otto Bock. "They had these neat properties. They were light but strong. That was a huge jump. That is when you saw more amputees running or playing basketball or at least doing a normal level of activity."
Sciullo, for instance, has carbon-fiber springs in his artificial feet. When he walks, the spring along the front part of his foot allows him to push down on what would be the ball of his foot, and as he steps forward, another spring in his "ankle" bounces the foot back. Once again, said Kanas, Sciullo's prosthetist, these are simple machined parts.
Otto Bock's version of the carbon fiber reinforced artificial foot.
"I order them from Otto Bock and each one is custom-made, depending on someone's height or weight or activity level," she said. "On the other hand, though, they are standard type parts.
"I don't think you could just go to your local machine shop and pick up one, though," she said, noting that this is a person, not a model car, who is using the part. "If this part wears out, I would want someone standing behind me who would fix it right away and correctly, so it's good to have manufacturers like Otto Bock or some other long-term business there. Still, I guess, there are a lot of people out there who could do this kind of work if they find a market."
Liberating Technologies found its own niche market in electronically powered upper arms. The Massachusetts company was spun off in 2001 from insurance giant Liberty Mutual, which decided it wanted to have control over some of the products they were insuring.
"There are not really all that many amputees each year, and of them, only 15 percent are upper limb, and only a portion of them need products like ours, elbows and shoulders," said Bill Hanson, Liberating Technologies president. Unlike hands and feet, though, elbows and shoulders have few, if any, upper arm muscles to work with, so the advance into electronics is a boon to those who need that kind of prosthetic.
Hanson's company does buy circuit boards and the electrodes that hook to the stump like EKG monitors, but they do the soldering in-house, either by hand or by machine. The Boston Arm, the flagship Liberating Technologies product, uses a standard three-phase brushless motor in the elbow, connected to the circuit board and the electrodes.
"We are forever battling the problem of weight. You can imagine what it was like to have a wooden or even a stainless steel arm. You really had no place to anchor it, so it was almost just a cosmetic thing," Hanson said. He said that research is now going on to figure out how to get cheaper and more malleable titanium and have it essentially screw into a stump. "It's done a lot in the dental field and more and more overseas. But people here are worried about infection, so it needs a bit more work."
Back in Texas, Rouse said he mostly loves just refining his machine-shop products. Rouse said he is now using Mazak 5-10C machines for precision turning and is also using a Haas TL-1 for slightly less high tolerance work.
"The average tolerance in the industry is five-thousandths and a normal tolerance for parts for good prosthetics is one or two thousandths, but I like to hold plus or minus a couple of tenths of a thousandth," he said with pride. "Each wrist we do has about 30 parts, and each N-Abler insert has another 10 or so, but you don't want these wearing out all the time. It's a person you are talking about here."
Sciullo, who uses his left-hand hook and right-hand flapper device made by Kanas with great dexterity, said he isn't interested in moving into electronic devices. He has a myoelectric arm, but keeps it in storage, rarely ever even trying to use it.
"If something wears on my mechanical limbs, I can see it coming beforehand or, even if it breaks, I can go to Joanne and someone can easily machine something for me," he said. "If I were dependent on electronics, who knows? They would have to send it out and I would be without for maybe weeks, or at least days. Sometimes progress is not what it seems."
The machinists like the feeling of custom work done immediately toward a greater end as well.
"Johnny and I had the opportunity to go to Walter Reed Hospital and talk to amputees who came from Iraq," said Farquhhrson. "They just wanted to get their limbs and either go back to be with their platoons or get on with their lives. Some got sophisticated stuff, but others worked with machined limbs like ours."
"It is a wonderful thing though, to make what is otherwise a simple item. I have a veterinarian, for instance, for whom we put in a scalpel part in the N-Abler, and now he can work like anyone else," said his partner, Rouse. "What other machinist can make things like this that put lives back together?"
