Plastic gear are lightweight, non-rusting, quiet, and able to be molded into complex shapes. They also have a much lower cost than metal gears and are very useful when a large ratio is required in a small space. Additionally, they are easily fabricated with CNC machining or injection molding. These factors make them a popular choice for many different applications.
While plastic gears do have some drawbacks such as the fact that they cannot be welded, these are not enough to prevent them from being used in a wide range of applications. Moreover, they do not require lubrication when mating with other gears which makes them more durable and less susceptible to damage during operation.
Because they are made of petroleum byproducts, plastics are inexpensive and easy to acquire compared to the more expensive raw materials needed for metal gears. This means that the production of plastic gears is a more efficient process. In addition, they can be molded into extremely precise designs that are impossible to achieve with metal gears. Furthermore, unlike metals, which can rust, plastics are odorless and do not have the same noise-generating properties that metals possess.
Whether you need to use plastic gears in an industrial machine, or just want to reduce the noise in your office, these types of gears are available in a variety of styles and sizes. You can even choose from a wide selection of colors, textures, and finishes. Most of these gears are made from polymers and other synthetic materials that have been molded into different shapes and sizes using a heated mold. This technique allows the gear to have a precise shape while ensuring its strength and durability.
The most commonly used plastic gears are either acetal or nylon. These are made from crystalline resins which offer exceptional fatigue resistance and good dimensional stability over a wide temperature range. Moreover, they are also highly resistant to most chemicals which makes them ideal for the mechanical industry.
While a few of the dimensional changes that can occur in plastic gears are very small, there are some cases where this can be problematic. For example, when an AGMA Class Q9 acetal cluster gear is being used to feed paper into a Hewlett-Packard DeskJet 660 color printer, the tight tolerances must be maintained in order for the paper to move without banding (obvious skip lines). In such cases, the molded plastic gear needs to be of high quality in order to guarantee consistent and reliable performance.
When designing plastic gears, it is important to start with detailed application specifications. These will guide the design of the tooth profile and tooth size. It is also necessary to keep in mind that the CAD drawings of the gear may differ from the actual finished product due to shrinkage and cooling effects. The corners of a plastic gear should be designed with radii to avoid stress concentrations and improve the material flow in these areas.