Machine Design

Plastic Chain

The variety of plastic chain available includes traditional designs with discrete links that connect to form almost any length, and newer designs that include one, two, and three parallel strength members. The traditional chain form of separable links is available from 0.125 to 6-in. pitches, and newer styles from 0.098 to 0.5 in.

The advantages of chain over belts is that it can be assembled around obstacles, is readily connected to form almost any length, and has favorable load and life ratings. Typically, a 0.125-in. pitch chain of acetal resin has a break strength of 7 lb, a working load of 5 lb or less, and need not be replaced until elongation exceeds about 3%. Large pitch link chains typically use a steel pin to link units together. Models with 6-in. pitch typically have an average ultimate strength of 5,500 lb and an allowable working load of 1,500 lb.

New style chains, sometimes called cable drive chain, combine features of link chain and synchronous belts. Generally, these chains are molded plastic links on 7 7 stainless-steel wire-rope strength members. On single strength member chains, plastic links or drive pins are either dowels or cross shaped. Pitch-to-pitch accuracy is 0.0005 in. Pitches are as small as 0.1 in. on single strand designs while transmission power ranges to 7.5 hp on larger three-cable styles.

Cable chains are available in stocked circumferences and can be spliced on site. Typically, on-site splicing derates the chain load by about 50%.

Advantages of the cable chain are that there is no play between teeth and cogs, they operate with commercial spur gears, mount on discs or inside rings to produce the effect of external or internal gear teeth, and require no lubrication.

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