The demand for less invasive and more efficient surgery has supplanted a riskier, more complex predecessor. Today, making surgery safer and easier on both the patient and surgeon is a paramount priority for any modern medical institution. Plainly said, for today’s health care networks and medical practices to compete, they all need to embrace surgical medicine that willfully opts-out of older, more dated models, in favor of better, safer and quicker alternatives.
Surgical robots is a growing and rapidly-evolving area of surgical science that commonly requires tungsten cable and cable assemblies to support the motion actuation of the appendages that perform the surgery.
Carl Stahl Sava Industries produces these tungsten cables and cable assemblies.
What is Robotic Surgery?
Robotic surgery is the act of using a surgical robot, which includes robotic appendages and grabbers, to act as the surgeon’s shoulders, upper- and lower-arms, wrists and fingers to perform delicate surgical procedures. Using joysticks, not unlike those used to play today’s most advanced video games or flight simulators, the surgeon manipulates the surgical limbs by adjusting the yaw and pitch axises to grab, hold, incise, close and perform a host of other complex haptic actions during a procedure.
These marvels of modern surgical medicine commonly require tungsten robotic cable assemblies to actuate the robot’s movements. The cables that power the motion control systems in a surgical robot must be small and thin enough to fit inside the robot, yet strong enough to tolerate as many as millions of cycles. While there are many mechanical cable options on the market, choosing a manufacturer that produces mechanical cable for surgical robots is a critical decision. In a market place fiercely competitive and changing constantly, the quality and efficiency with which the cable maker delivers can determine the agility with which the surgical robot maker can compete.
Choosing a Cable Maker and Cable Size
Surgical robots cannot afford to have a mechanical cable failure due to weakening of the cable’s filaments. Thus, tungsten cable is an ideal choice, as wolfram is Earth’s strongest natural metal. Deciding on the mechanical cable diameter depends upon the load capacity requirements of the cable application. For surgical robotics, a higher load capacity is needed to transmit force during surgery that will not run any risk of breaking or fatiguing over time. But strength cannot come accompanied by prohibitive cable diameters, too. So, efforts must be made to use a cable construction that provides the robot with super-strong tungsten cable, without an oversized footprint.
When Sava manufactures tungsten cable, the individual wires that comprise the cable must be small to ensure they satisfy both the robot’s strength and miniature application requirements. This is why Sava makes tungsten cable using wire as small as .00072” in diameter. For example, a 19x37 tungsten cable contains 703 filaments that are smaller than 1,000th of an inch in diameter. By way of comparison, a human hair is between two or three thousandths in diameter, and barely noticeable without the aid of magnification. Imagine 1/3 of that size in the strand construction of surgical robotics cable and one arrives at the ultrafine cables Sava is producing for surgical robots.
Carl Stahl Sava Industries proudly manufacturers the following tungsten cable constructions:
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19x7
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8x19, also referred to as 7x7+8(1x19)
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19x19
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7x49
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7x37
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19x37
Cable Strength and Material Characteristics
When it comes to surgical robotics, there are other reasons why tungsten makes sense however. For example, tungsten is known for its tolerance to heat and mechanical flexibility. And while tungsten cable, applied to surgical robots, is not commonly exposed to excessive heat, its flexibility makes it an optimal cable material. Where stainless steel wire tends to exhibit a stiff and springy character, tungsten is lazy, or “dead” when held in one’s hands. This lifelessness from the tungsten cable allows for it to cooperate better with mating parts and when making contact with other components, where perhaps tight radii are present. What’s more, tungsten can withstand temperatures up to 6,000 degrees Fahrenheit and be bent and stretched repeatedly without losing its original shape.
While most modern surgical robotics applications call for tungsten cable, in some applications, stainless steel may be an acceptable material. 304 stainless steel is the most economical option given it’s the most common form of stainless steel used in mechanical cable manufacturing. However, 316 stainless steel is popular for applications that require increased corrosion resistance properties because it contains less chromium, increased nickel levels and adds molybdenum, which reduces the risks of pitting, while adding to the material’s tolerance of corrosion and high temperatures.
Tolerating Long Lifespans
As discussed, cables for surgical robotics need to be small, but strong. Once again, while performing robotic surgery, the surgeon cannot have a cable fray or break.
Surgical robots often use small pulleys, and they're usually made out of hardened steel or anodized aluminum and can be extremely small in diameter. If the cable doesn't fit properly around the pulley, the poor-fitting mating components could fatigue, which may lead to abrasion, breaks or total cable failures. Cables made for surgical robotics are largely made from tungsten precisely for this reason. Tungsten cables can tolerate long lifespans without damage to the individual wires that make up the cable’s construction. They are built from materials and stranded using construction configurations expressly designed to carry loads over significant periods, no matter their contact with other components.
Key Takeaways
Cables used in the manufacture of surgical robots must serve many masters. They must be made of wires so small, one would have difficulty even seeing them with their naked eyes. Yet as small as the surgical robotics industry requires of its mechanical cable, it expects these ultrafine tungsten cables to be as strong as they are small. Add to this complex equation the need to deliver quickly and efficiently, and it’s easy to see what a challenge these cables are to make.
Striking a balance between small and strong, and quick, but reliable requires levels of cable manufacturing and mechanical engineering expertise keenly capable of producing the most complex tungsten cables on earth. A delicate mix of satisfying the rigid break testing, tolerance and flexibility requirements these cables are known for, all coalesce to bring to market the world’s next big surgical robotics innovation.
