Plastic Gears
Plastic gears are continuing to displace metal gears in a widening arena of applications. Their unique characteristics are also being enhanced with new developments, both in materials and processing. In this regard, plastics contrast somewhat dramatically with metals, in that the latter materials and processes are essentially fully developed and, therefore, are in a relatively static state of development.
Plastic gears can be produced by hobbing or shaping, similarly to metal gears or alternatively by molding.
Among the characteristics responsible for the large increase in plastic gear usage, the following are probably the most significant:
- Cost effectiveness of the injection-molding process.
- Elimination of machining operations; capability of fabrication with inserts and integral designs.
- Low density: lightweight, low inertia.
- Uniformity of parts.
- Capability to absorb shock and vibration.
- Ability to operate with minimum or no lubrication.
- Relatively low coefficient of friction.
- Corrosion-resistance.
- Quietness of operation.
Tolerances often less critical than for metal gears, due in part to their greater resilience.
Consistency with trend to greater use of plastic housings and other components.
One step production; no preliminary or secondary operations.
At the same time, the design engineer should be familiar with the limitations of plastic gears relative to metal gears. The most significant of these are the following:
- Less load-carrying capacity.
- Lower accuracy.
- Greater dimensional instabilities, due to their larger coefficient of thermal expansion and moisture absorption.
- Reduced ability to operate at extremely high and low temperatures.
- Initial high mold cost in developing correct tooth form and dimensions.
- Can be negatively affected by certain chemicals and even some lubricants.
- Improper molding tools and process can produce residual internal stresses at the tooth roots,resulting in over stressing and/or distortion with aging.
- Costs of plastics track petrochemical pricing, and thus are more volatile and subject to increases in comparison to metals.
At GearLab we have a great experience in design and production of plastic gears for a wide range of applications. We have successfully delivered optimal plastic gearboxes for automotive applications, e-bikes transmissions, and several industrial.
Contact Us to request a free consultation for your application!
