This article, written by Tom Cartwright, originally appeared on Ezine Articles. com.
For high-torque and high-horsepower applications, the timing pulley advantage goes to the metal pulleys. They offer significant differences in tensile strength and size options, but that's where the benefits end. While the term 'plastic' is used to describe a class of timing pulley materials, it is actually glass filled nylon that is the focus of this article. Nylon is a very tough material and excels at making components such as over molded timing pulleys.
Besides being a comparatively inexpensive option to metal pulleys, nylon timing pulleys have an array other options that need to be considered:
Non-Magnetic: Nylon pulleys carry no magnetic signature making them ideal for many mechanisms, devices, processes or electronics that are susceptible to very slight changes magnetic fields. Nylon pulleys are not influenced by strong magnetic fields making them ideal for use around equipment such as MRI machines or magnetic conveyors.
Long Service Life: The working surfaces of the pulley are supported by a web that is designed to manage loads and high speed rotation. The web in turn is supported by a metal insert for the installation of the pulley on the drive or driven shaft. The inserts can be made from aluminum, carbon steel and stainless steel and do have the usual mounting options. To be clear, the term 'insert' can be misleading, since the insert is not pressed or screwed into the nylon pulley, but rather it is a precisely machined part that is over molded during the molding of the nylon pulley.
Lightweight: Nylon's specific gravity is about half of that of aluminum and about one-sixth that of steel. That means nylon is lightweight and produces components with low inertia properties.
Flame Retardant: Nylon timing pulleys can also be made using flame retardant additive which will comply with UL94-V0 UL flammability standards, which basically dictates that the pulleys will not burn without a continuous ignition source. In other words, they are self extinguishing and will not contribute to the spread of fire.
Chemical and Corrosion Resistant: Some general facts about nylon pulleys you should consider: They are both chemical and corrosion resistant; they will not rust or oxidize; can be used in most environmental conditions; and because nylon is a natural lubricant, belt life will not be prematurely shortened.
High Temperature Applications: Nylon pulleys can be used in high temperature locations generally not exceeding 275°F (135°C) but also note that for most pulley driven mechanisms the temperature limits of the timing pulleys far exceed the temperature limits of most belts.
No Static Build-Up: Static build up and it's eventual discharge can be problematic in industries that use pulleys as part their process equipment. Static electricity is a function of high speed mechanical motion, atmospheric conditions (humidity) or location within an electrical field. The result is a build up of charges on surfaces. It can be deadly in explosive environments where high concentrations of flammable dust, volatile solvents or hydrogen gas is present. In many sensitive manufacturing operations, it only takes a few volts of static electricity to destroy sensitive products, such as computer chips. To prevent this potential problem, nylon timing pulleys can be manufactured using additives such as PAN (Polyacrylonitrile) Carbon Fibers, a common material used in the aerospace industries. On its own, nylon is a great insulating material, but the addition of PAN further enhances it's anti-static properties.
The use of plastics in the manufacture of mechanical components has come a long way in the last few decades. New additives blended into resins, such as nylon, have greatly enhanced the performance, versatility and value of timing pulleys and many other similar products. In many applications, nylon is a superior choice over carbon steel or aluminum.
Torque Transmission manufacturers nylon timing pulleys in a variety of standard size and custom sizes - All provide superior performance and economic design. Because our timing pulleys only require a minimal amount of belt tension to prevent slippage, the bearing loads on the driving shaft are greatly reduced. Visit TorqueTrans.com for complete details.
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