Vespel and other dry bearings
Vespel and other dry bearings
Du Pont's Vespel SP-262 is well suited to automotive powertrain applications, according to product manager Tom Ruffalo, "Many high performance polymer compositions have a much higher coefficient of thermal expansion than steel, requiring large clearances between the bearing and shaft to prevent binding. Vespel's low expansion rate permits minimal shaft/bearing clearances for noise reduction". Engine applications under development include bearings for exhaust gas recirculation valves, cooling fan bearings, engines valve guides and transmission needle bearings.
Vespel SP-262 performance figures:
PV limits against steel or cast iron (pressure × velocity) Mpa ×m/s: Dry 10.5; Lubricated 42; Lubricated (instantaneous) 140.
Temperature limits °C Continuous service 316; Surface temperature for bearings 393; Brief temperature excursions (allowing for use in aluminium diecasting) 649.
Contact: Du Pont (UK)Limited, Maylands Avenue, Hemel Hempstead HP2 7DP. Tel: 01442 346800; Fax: 01442 346810.
Thomson presented their new FluoroNyliner bushing bearing at the recent Hannover EMO exhibition. It is an anodised aluminium sleeve with a bonded-in machinable PTFE liner.
Contact: Thomson IBL Limited, Westacott Road, Whiddon Valley, Barnstaple EX32 8NU. Tel: 01271 334500;Fax: 01271 334 502.
C-Flex Bearings in the USA offers a range of self-centring spring flexure pivot bearings for frictionless,wear-free rotary applications up to ±30°. They need no lubrication,eliminate backlash, give constant torsional stiffness and have load capacities up to 730 kg. Standard sizes are from 1Ž8in.-1in. diameter. Applications are lever actuators, linear positioners, prismatic scanners, media disc positioners.
Contacts: (UK) Tel: 0148 4850401; Fax: 0148 485415-0; (Germany) Tel: 0622 164560; Fax: 0622 16456-22.
Vesconite self-lubricating polymer bushes fitted to a 2,500 t/hour reclaimer carrier chain extended chain life by a factor of five, gave better performance, and reduced downtime and maintenance. Vesconite works particularly well where lubrication is impractical,such as in dirty environments, immersed in water or where contamination must be avoided.
Contact: Vesconite Sales Limited, PO Box 243, Northampton NN3 3YR. Tel/Fax: 01604 231948.
Greblon solid lubricant coatings from Weilburger have been tested at the National Centre of Tribology(NCT) and shown to outperform nylon 66 and competitivecoatings. Greblon has been used in the automotive and aerospace industries as well as on industrial bakeware products. Coatings can be for mould release or offer low dynamic friction for moving applications.
The NCT has also tested Whitford Plastics' Excalibur, the stainless steel reinforced fluoropolymer system.
In reciprocating"pin-on-plate" friction and wear tests, the Excalibur coatings were shown to have a specific wear rate as much as 50 times lower than that of conventional coatings. Even when the tests were extended to give a sliding distance of 25,000 metres, Excalibur still demonstrated an improvement in wear resistance of over six times that of unreinforced coatings.
The tests were funded by members of ExcalNet Europe, a pan-European group of independent applicators licensed by Whitford to apply the Excalibur system. The programme demonstrated how Excalibur extends the durability of bonded solid lubricant coatings by offering increased mechanical support. The solid lubricant capabilities are also increased due to Excalibur's excellent ability to replenish a thin film of PTFE at the sliding interface.
Excalibur is a unique system. First, the substrate to be coated is blasted with an abrasive to roughen it, and improve adhesion. Then, white-hot particles of a special stainless steel(an alloy patented by Whitford for the process) are sprayed on to the roughened surface. The particles cool and harden, bonded to the surface forming a series of "peaks" and "valleys" that provide a permanent base for the coatings.
The Excalibur dry lubricant application process, "arc spray"
Several coats of tough fluoropolymers are applied, filling the "valleys" and covering the "peaks",producing a coating "locked" into place by the stainless steel reinforcement.
Applications range from industrial bakeware through rubber and plastic moulds to safety equipment.
Contact: Whitford Plastics Limited, Christleton Court, Manor Park, Runcorn, Cheshire WA7 1SU. Tel: 01928 571000; Fax: 01928 571010.
