Why plastics gears

Two important advantages offered by plastics gears have been mentioned already - quiet running and cheapness. There are several others, and they may be listed as follows. 

Frictional properties Plastics gears can often be run satisfactorily without external lubrication, as long as suitable material pairs are selected to mesh together. Dry running conditions can be important in office machinery to avoid contamination by paper dust. Suitable oil and grease can be used where appropriate. In other cases, the moulding materials selected can contain internal lubricants. More detail is given in Section 4.6. 

Low mass The low densities of plastics materials gives an assembly of low mass, and hence low inertia. This can be useful under start-up conditions, and may even allow the use of a lower-power motor. 

Corrosion resistance This can be important in aggressive environments. 

The office-copier gearbox example invokes several of these features. The resilient nature of plastics materials, combined with the design freedom permitted by moulding allows a very resilient design which runs quietly, thus giving a superior product at much reduced cost. 

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