Plastic gears, not to be compared with metal ones!
Plastic gears are spreading in the market in recent years, but too often what is asked is how long it can last compared to a steel gear. Of course, plastic and steel have different characteristics, therefore it would also make little sense to want to compare them with respect to the same parameters, especially if closely related to the strength of steel.
Plastic gears: a defined market niche
To date, plastic gears, instead of competing with steel ones, given the obvious difficulty of using them as interchangeable, have created a market niche of use. In particular, they are perfect in typical applications of large size actuatorsis; on the contrary, in gearboxes where the torque is quite large compared to the space available, then steel is the winning material.
Furthermore, the perception of the engineers has also changed a lot and now they are starting to really consider plastic gears as a concrete alternative, thus feeding their market.
Main advantages and characteristics of plastic gears
Certainly the most interesting aspects of plastic gears are the secure load sharing capability: in some cases, in fact, contact relationships reach impressive numbers.
During the studies and experiments, one of the most remarkable results was in reference to the gears with a contact ratio greater than 1; typically, a sagging occurs, because the teeth do not flex. Instead, with those in plastic material, it is possible to have up to 4 teeth in contact without anything jamming. As a result, enormous load sharing is achieved.
Furthermore, another specific characteristic of plastic is that of absorb noise, being a very soft material. In this period, where silence is becoming a value (as for electric cars), it sometimes happens that the engine's gears are the loudest part of the vehicle. Therefore, i have also been producedgears formed from plastic and rubber to make them even softer and quieter, even if alone they cannot be enough to eliminate any noise.