Gears are essential parts for a lot of different machinery. They can be found in things like conveyor systems, power tools, and even cars. They transmit power, motion, and information in the form of torque, which is the force that turns a shaft. There are a number of factors that need to be considered when designing a gear, including its strength, weight, cost, and precision. Many of these are influenced by the type of material that is used to make the gear. One of the most commonly used materials for gears is plastic. Plastic gears are able to provide the same functionality as metal gears, but often with a much lower cost and increased flexibility. They are also able to withstand more varied conditions than their metal counterparts.

While early adventures with plastic gears had some quality problems, modern plastic gears routinely withstand conditions that would have killed metal gears. It is important for engineers to remember to think about the conditions that their gears will be exposed to and design them accordingly. The most common types of engineering plastics are polyamides (nylons) and acetals, also known as Delrins or acetal copolymer. These can be machined or molded, depending on the application. It is important to do mechanical calculations when selecting a specific polymer, especially for high-speed applications that require a greater load capacity.

When using plastic gears, it is important to keep in mind that they will need lubrication. The type of lubricant needed will depend on the conditions that the gear will be subjected to. Petroleum-based lubricants are generally not recommended because they can damage the plastic. Instead, engineers should opt for a solid-state lubricant that contains molybdenum disulfide or graphite.

It is also important to be aware that certain types of plastics are more reactive than others to chemicals. The most reactive types include polystyrene, ABS resins, polycarbonates, and polyvinyl chloride. They may also be sensitive to some alkali cleaners and solvents. The least reactive types include nylons, acetals, polyethylene, and polypropylene.

Lastly, plastic gears are able to resist moisture and water much better than their metal counterparts. This can be a huge benefit in some situations, such as in marine environments where saltwater can corrode and degrade metal gears. It is also useful in equipment that will be subjected to a lot of shock and vibration, as these can cause sudden failures in metal gears.

Plastic gears are a great alternative to metal for applications that need low-speed, lightweight, quiet operation, and chemical resistance. These are some of the reasons they are becoming a common replacement for metal gears in office automation equipment, food production equipment, and light-load drive equipment (3/4 hp or less). Thermoplastic polymers, such as technopolymers and hyperpolymers, have made plastic gears more capable than ever before. They can provide the same performance and longevity of metal gears, but at half the weight. They also offer increased flexibility for dimensional expansion and quieter operation.

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