Polymer chain is lube-free

Dean Palmer reports on a new range of lube-free chain that uses polymer rollers and bushes, offering users a quieter, greener product that withstands frequent wash down While plastic chain is certainly not new to the engineering world, a range of chain products that use a polymer bush and roller is not something Eureka has come across before, apart from custom-designed 'specials'. The 'Syno' polymer bush chain, developed by Renold Chain, is a range of lubricant-free chain products that are not only quieter and less harmful to the environment than their steel counterparts, but are also capable of working in harsh environments, including industries in which frequent wash down or lubricant contamination is a problem. Mike Christmas, engineering director at Renold Chain explained to Eureka the origins of the product: "We started developing the product two years ago. Food manufacturing and water treatment customers wanted lubrication-free chain that didn't contaminate their product and would cause minimal damage to the environment. The Syno polymer bush chain is our first real chain that tackles these issues." The chain uses two specially developed polymers, one for the bush and another for the roller. The plastics were developed in conjunction with a major global plastics manufacturer (who cannot be named). The polymer bush is located between the pin and the original steel bush. The polymer has excellent performance, is very durable and was developed so that it could be injection moulded into a round shape. As Christmas joked: "We wanted a polymer that had 90% of the characteristics of a high performance engineering plastic [such as PEEK], but at 10% of the cost. Otherwise we'd have an excellent chain product that nobody would want to buy." The plastics developer constructed an articulation rig and four different prototype polymers for Renold to test. "The polymer had to withstand battering from the sprocket and be corrosion resistant so we looked at ways of adding a multiple layer zinc coating to the polymer," added Christmas. While one would expect the performance of steel to be superior to plastics for endurance life tests, Christmas revealed that the new polymer bush chain "achieved within 90% of the performance of the equivalent steel chain". The chain is currently being beta-tested by a major European automotive customer. Christmas continued: "The chain is being used on a transfer workstation on the factory floor, running 24 hours a day. So far, there have been no problems with it." The chain is lubricant-free and actually works better without lubricant, although lubricating the chain by accident won't damage the product. Another advantage of the polymer chain is that it can take 50% higher bearing loads than steel equivalents, due to its higher galling (caused by two components rubbing together) resistance. The product is also lighter, around 5 to 10% according to Christmas. This makes handling easier but more importantly, reduces the centrifugal (or centripetal acceleration) force on the chain when operating. The new range extends Renold's Syno range, which also includes stainless steel chain, for corrosion resistance, and nickel-plated chain for hygiene-sensitive applications. The new polymer bush chain is manufactured to both BS and ANSI standards. Sizes range from 1.75 to 2.5 inch pitch for BS chain and 1.5 to 2.5 inch pitch for ANSI chain, although the company hinted that once the product is established, smaller ranges will be developed.