Novel polymer cable carrier is low cost and quiet

During a recent trip to Germany, Eureka visited the headquarters of cable chain manufacturer Igus and discovered some interesting innovations. Aside from boasting an incredibly modern, novel design of office and factory (the architect, Sir Nicholas Grimshaw, also designed the London Stock Exchange building) Igus' site is also home to some really innovative products. The company is renowned for its reinforced plastic cable carriers (or 'energy chain' as Igus has branded it), although more recently the firm has been building up quite a reputation for its polymer bearings, bushes and linear slides. But it was in the company's cable chain range that Eureka found some quite novel products. The cable chain test laboratory at the site is impressive. 700 test results per year are recorded there, although the test duration ranges from 1s up to five years. Ralf Kabus, marketing director at Igus, told Eureka that the company's longest running test actually started in 2000 and is still in progress today. Test travel in the lab varies from 15mm up to 120m and there were 80 tests running simultaneously on 35 separate test rigs, supervised by five lab technicians. Cycles per test can be as high as 100 million cycles. Clearly, this is a company where innovation, new product development and customer 'specials' are based on thorough testing. The company's latest innovation on the cable chain side of the business is the 'System E3 Energy Chain'. This is a combination of two other products. The short pitch design of Igus' 'E6' product line, which provides a smooth, quiet operation and low vibration levels (even at high speeds). The E3 system also incorporates the company's 'Zipper-style' chain design, where the link closes on the outer radius for fast, easy cable access and installation. The result is a lightweight, compact design of cable carrier, which lends itself particularly well to smaller E-chain applications such as drawer slides, enclosures, pick-and-place robots, and for the printing, clean room, medical and semiconductor industries. To develop a small, silent, durable but low cost cable carrier was a challenge. A short pitch reduces the polygon-effect, but subsequently increases costs. An elastic spring rather than pin-hole connections has turned out to be useful for mid- to large-sized Energy Chains from the E6 range, but reducing the size of this spring would have increased parts and assembly costs. Soft or extruded straps turned out to be too limited and unstable when in motion, with the same being true for hybrid cables with integrated spring bars. Production would only be justified for large-scale manufacture. The E3 series derives its name from its three basic components: a link made from reinforced polymer, 'igumid G'; a spring connector; and a band of cross bars, which open like a zip. The spring connector replaces the need for a pin-hole connection and avoids movements between the joints, so the chain is almost completely free of wear. To reduce production and assembly costs, the spring band is not mounted individually, but on a length of ten chain links. And, as the modified spring component is made from an electrically-conductive material, this guarantees constant electrical conductivity, even under high bending stresses. Noise levels in lab tests showed a 19-20 db(A) reduction compared to the company's standard Energy Chains, measured at a speed of 1.8m/s and an acceleration of 3m/s2. To put this in perspective, 3 db(A) represents a 50% reduction to the human ear, so the advantages to machines and production environments are clear. During long term tests, system E3 completed 15 million cycles at a bending radius of 44mm and an acceleration of 4g. The test is ongoing. In similar tests, E6 has so far completed 120 million cycles without damage. David Chapman, MD at Igus UK, predicted: "By using System E3, our customers will improve an important function of their machines tremendously, by reducing noise and increasing lifetime. Cost is reduced due to shorter assembly times and because Energy Chains and cables last much longer."