Plastic gear have gained in popularity because they offer distinct advantages over their metal counterparts. The flexibility of plastics lets them absorb shock and vibration, and their lubricity helps to reduce friction. They also tend to be less dense than metal, reducing inertia. This can be a particular benefit in applications where vibration or noise could be an issue, such as in household appliances and lawnmowers.
There are several ways to produce a plastic gear, but injection molding is typically the fastest for small-volume production. For high-volume production, a die casting process is often used. Both techniques require molds, which must be made from metal or another material, such as rubber, which can be expensive to produce.
When compared to the cost of machining, plastic gears are much more affordable to manufacture. Furthermore, they can be produced in very short time periods. CNC machining is suitable for producing low-volume plastic gears, such as ten or twenty parts in a week or two. Injection molding, on the other hand, can produce thousands of gears in a few months, but a new mold must be made for each production run.
Injection molded plastic gears can be produced to a high level of accuracy, but the precise tolerance depends on the resin chosen for the application. Crystalline resins (such as nylon, or acetal) are the best for gear applications. They have good fatigue resistance, good dimensional stability, and can withstand some corrosion. However, these resins do not dissipate heat as well as metal and can swell due to moisture absorption. This can affect tooth contact area and center distance accuracy.
The elastic compliance of plastic gears allows them to operate with minimal or no lubrication, which can help reduce costs and maintenance. Lubricated gears can be run at lower temperatures than unlubricated ones and have a longer life. However, a lubricated gear can still experience overheating of the tooth flanks and bending fatigue.
Plastic gears are generally easier to maintain than their metal counterparts. They can be wiped clean and may not need to be re-lubricated as frequently. They can also operate under a higher load, and their greater resilience can make them safer than metal gears for operating in wet environments or food preparation.
Overall, plastic gears are a cost-effective and durable alternative to traditional metal gears. They have many different benefits and can be used in a wide variety of applications. However, their sensitivity to ambient conditions must be taken into consideration during design and specification. A thorough analysis of the application, including the environmental conditions, is required to determine a suitable resin and manufacturing process for each individual project. This information should be analyzed using CAD tools designed specifically for plastics. The proper selection of these tools can make the difference between a successful and a failed project. If you are looking for expert design and engineering services, get in touch with us at Stagnoli. We will help you to select the right resins for your applications, and provide a quality, finished product.
