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Choosing the Right Mechanical Cable Material

Wednesday, June 17, 2020

The mechanical cables used to actuate motion in virtually any surgical robot, endoscopic device, aerospace, and military equipment vary by material one application to the next. The chemical elements comprising the mechanical cables manufactured for such purposes are determined by what the cables need to achieve, for how long, and under what circumstances. For example, using stainless steel cable, where extreme heat is present, would perform worse than tungsten mechanical cables, because the latter is far more tolerant of intense temperatures. Likewise, where the application to call for prolonged exposure to salt water, using galvanized steel cable, as opposed to its stainless steel counterpart, would not make sense either, as galvanized steel corrodes more easily in such conditions.

Here's a brief guide to choosing the right material for your mechanical cables. 

Tungsten

Tungsten cable is growing in popularity due in good part to the evolving growth of the world's surgical and industrial robotics markets. Although tungsten mechanical cable is considerably more expensive than steel alternatives, tungsten is remarkably resistant to extreme temperatures, is extremely flexible, and is stronger than equivalent stainless steel cables. Tungsten's melting point, at 6,192 °F, compared with stainless steel's 2,750 °F, makes tungsten an ideal material where heat-tolerance is a priority. Conversely, stainless steel is not the best choice in applications where exposure to excessive heat is a variable. Stainless steel mechanical cable anneals at extremely high temperatures, reducing the material's integrity under prolonged such conditions.

Tungsten may cost as much as ten times more than a stainless steel cable of the same size, but its strength is about 20% greater. Tungsten is likewise more flexible and abrasion resistant at equivalent sizes of stainless steel. A tungsten cable manufacturer can construct tungsten cable using wire that is no more than .0005 inches in diameter, making it well suited to surgical robots, where the cable must be extremely flexible and strong, yet consume very little space within the devices themselves.

For these reasons, tungsten mechanical cable is the preferred choice of cable material for surgical robots, industrial robots, and a bevy of other medical and industrial device applications.

Speaking of surgical robots, as well as other robotic devices, a tungsten mechanical cable supplier produce cables that perform optimally in such markets where ultrafine cables must transmit heavy loads relative to instrument and device size. What's more, in surgical and industrial robots, which typically cost hundreds of thousands or even millions of dollars to build and purchase, tungsten extends product lifespan by virtue of the increased cycle counts commonly achieved using these materials in cable manufacturing. 

Stainless steel

Stainless steel is a corrosion-resistant alloy made from iron, chromium-nickel and other elements, containing no less than 10.5% chromium, with specific ratios varying depending on the alloy. There are several kinds of stainless steel commercially available, possessing different chemical components in different proportions. In the United States, for example, among the most common stainless steel is 304, which comprises a chromium content minimally of 18 percent, along with 8 percent nickel, which blended is what becomes 304 stainless steel, and comprises no more than .08 percent carbon. This ratio ensures a high tensile strength for mechanical cables commonly used in the manufacture of a wide array of mechanical medical devices, as well as industrial, aerospace and defense products. Elsewhere, particularly in Europe, 316 stainless steel is more common. Like all steels, 316 is primarily made from iron and contains high degrees of chromium and nickel as well. Combined with 2-3 percent of Molybdenum by weight, 316 stainless steel offers superior corrosion resistance than 304 stainless steel.

Stainless steel is the best choice for applications in which the environment may introduce the risk of corrosion. That makes stainless steel mechanical cable an ideal choice for cable expected to be used outdoors, underwater, in an air or spacecraft, or in any other situation that would expose the cable to the elements. In particular, it's highly resistant to corrosion by acids and bases. Likewise, one would choose stainless steel mechanical cable in a host of surgical and medical devices, or any other finely calibrated instrument that could endanger the life of a human being or the performance of such critical machines due to flakes of rust or other foreign microscopic particles coming in contact with forbidden areas. 

Galvanized steel 

Galvanized steel is steel that has undergone a galvanization process known as hot dip galvanizing or HDP. HDP is the process of dipping the steel in molten zinc that forms a coated zinc layer around the steel, which protects the material against corrosion. 

Galvanized steel mechanical cable is almost always less expensive than stainless steel and is stronger as one reaches cable diameters of up to 1/8, 3/16, ¼ diameter, or greater. A 1/8-inch galvanized steel cable is 10 to 15 percent stronger than a stainless steel cable of the same size. Some galvanized cables can be as much as 20 percent stronger than a stainless steel cable of the same diameter.

Galvanized steel is also not as corrosion-resistant as stainless steel. However, because of its zinc coating, it is safe enough for most outdoor applications. Its low cost-to-benefit ratio makes it an engineer's go-to material for many mechanical cable assemblies meant for indoor applications such as hanging heavy signage or suspending, lifting or counterbalancing large items. Galvanized steel cable also performs well outdoors, in solutions such as pens for livestock, to the cables used to anchor telephone wires.

Because galvanized steel cable is not ideal where corrosion is likely, engineers do not use this mechanical cable material in marine, acidic, or alkaline environments for instance, since this variety of steel does not tolerate salt water conditions well. Galvanized steel is also not an ideal material if aesthetics are a priority. Because the zinc coating on galvanized steel cables possesses a flat, unattractive matte finish that cannot be polished to a shine, stainless steel is a better choice where optics count. By way of comparison, stain steel cable is commonly used in porches, beach houses, staircases, and other architectural applications where color, shine, and optics are critical to achieving the desired look, as well as mechanical integrity. 

Need Help?

Talk to our team of mechanical cable materials experts today and ensure your project uses the very best solution for your application. No matter your mechanical cable assembly needs, Carl Stahl Sava Industries can help. Contact us or visit our website today to review our product details and see what's compatible with your project.