Wed. Jun 19th, 2024

For many decades metal was the primary material in gears, but plastics have begun to take a significant share of the market. This is due in large part to the fact that they offer advantages over metals, such as superior shock absorption and self-lubrication. They also resist corrosion and are available at half the weight of metal alloys. However, it is important to be aware of the drawbacks of using plastic gear. It is also important to understand how a plastic gear works so that you can design it properly and avoid the many potential failure points that can occur with them.

Many types of plastic can be used to make gears, but two that are particularly popular are acetal and nylon. These are typically molded, but they can also be machined out of raw materials. Both of these are relatively dimensionally stable and are resistant to chemicals, but acetal has better load bearing capacity and is more moisture resistant than nylon.

Both acetal and nylon can be enhanced with additives and fillers that improve the performance of the base polymer, such as increasing strength, durability and toughness. The exact formulation will depend on the application for which the gears are being used, so a mechanical analysis should be conducted to determine the stresses and forces that will be applied to them.

The elasticity of plastics is one of the primary characteristics that distinguish them from metal gears, as they can absorb a lot of shock and vibration. This reduces noise and helps the gears to function more effectively without causing damage or unnecessary wear and tear. Additionally, plastics do not crack under excessive pressure like metals, and they rebound quickly to alleviate the tension.

Another reason to use plastic gear is that it does not require periodic lubrication, as metals do, because it produces its own internal lubricant. This can greatly reduce the maintenance costs and downtime associated with lubrication. The lubricating properties of plastics are dependent on their temperature range, and they can begin to degrade or disintegrate when exposed to extreme temperatures.

A plastic gear is often attached to a metal shaft with a fastener such as a screw, nut or knurled press fit. This is an effective method of attachment because it distributes the load evenly and ensures that the gear will not come loose or break. When selecting an anchoring method, it is important to consider the coefficient of thermal expansion of both the plastic and the metal. This will minimize the stresses that are produced when the plastic shrinks during cooling after molding.

It is also important to note that certain petroleum-based lubricants can break down the plastic and cause it to become brittle. This is why it is necessary to select a non-petroleum-based lubricant for plastic gears. Some common options include white lithium grease and teflonĀ®. It is also advisable to avoid any greases that contain tallow, rosin or paraffin. These lubricants can cause premature wear and shorten the lifespan of the gears.

By Admin

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