Plastic Bearings Can (and Do) Outperform Metal Bearings Day 1: Plastic vs. Metal

Plastic Bearings Can (and Do) Outperform Metal Bearings Polymers in general Natural polymer lubricants Oils and greases Incorporated into solids Plastics and rubbers 2

Plastic Bearings Can (and Do) Outperform Metal Bearings Why use polymer bearings Fluid lubricants not effective Fluid lubricants not safe Maintenance issues Insufficient boundary lubrication 3

Plastic Bearings Can (and Do) Outperform Metal Bearings Possible environments Marine: seawater and fresh water 4

Plastic Bearings Can (and Do) Outperform Metal Bearings Possible environments Agriculture: moisture, dirt, chemicals 5

Plastic Bearings Can (and Do) Outperform Metal Bearings Possible environments Medical: equipment, implantable devices 6

Plastic Bearings Can (and Do) Outperform Metal Bearings Possible environments Packaging: food and pharmaceuticals 7

Plastic Bearings Can (and Do) Outperform Metal Bearings Simple polymers Stachowiak & Batchelor,, Engineering Tribology, 2005, 3rd Ed., Elsevier Inc., Chp. 16, Fig.16.1, pp. 653. Bunn & Howells, (1954), “Structures of Molecules and Crystals of Fluorocarbons”, Nature, 174, pp. 549-551. Makinson & Tabor, (1964), “The Friction and Transfer of Polytetrafluoroethylene”, Proc. Roy. Soc. (A), 281, pp. 49-61. 8

Plastic Bearings Can (and Do) Outperform Metal Bearings Simple polymers Ludema, Friction, Wear, Lubrication: A Textbook in Tribology, 1996, CRC Press, Chp. 8, Fig. 8.15, pp.143. Stachowiak & Batchelor,, Engineering Tribology, 2005, 3rd Ed, Elsevier Inc., Chp. 16, Fig. 16.3, pp. 655. Makinson & Tabor, (1964), “The Friction and Transfer of Polytetrafluoroethylene”, Proc. Roy. Soc. (A), 281, pp. 49-61. 9

Plastic Bearings Can (and Do) Outperform Metal Bearings Limitations of simple polymers High wear rates Frictional heating Solvent damage Soft – easily deforms Mostly low loads Stachowiak & Batchelor,, Engineering Tribology, 2005, 3rd Ed, Elsevier Inc., Chp. 16, Figs. 16.7, 16.9, and 16.26, pp. 657-672. Arnell, Tribology: principles and design applications, 1991, Macmillan, pp. 110. Khonsari,& Booser, Applied Tribology: Bearing Design and Lubrication, 2008, Wiley & Sons, pp.97. 10

Plastic Bearings Can (and Do) Outperform Metal Bearings Composite polymers Improved mechanical strength Improved wear resistance Reduce coefficients of friction 11

Plastic Bearings Can (and Do) Outperform Metal Bearings Composite polymer bearing Solid lubricants lubricate the system independently, mitigating friction and reducing wear rates Base polymers are responsible for low coefficients of friction. Fibers and filler materials reinforce the bearing and allow for high forces or edge loads on the bearing. 12

Plastic Bearings Can (and Do) Outperform Metal Bearings Advantages of composite polymers Improve mechanical and thermal properties Addition of reinforcing fibers and fillers Reduce wear rates Effective under high and low loads 13

Plastic Bearings Can (and Do) Outperform Metal Bearings More advantages Low coefficients of friction with mating materials Biocompatible Self-lubricating Serve as reservoir for boundary lubricants 14

Plastic Bearings Can (and Do) Outperform Metal Bearings Selection criteria Maximum load Sliding speed Environmental conditions Counterface roughness PV limit Wear factor k 15

Plastic Bearings Can (and Do) Outperform Metal Bearings Composite plastic bearings vs. Simple plastic bearings Bronze bearings PTFE-lined, metal-backed bearings Ball bearings 16

Plastic Bearings Can (and Do) Outperform Metal Bearings Composite plastic bearings vs. simple plastic bearings Composites enhance the benefits of plastics Base materials Fillers - increase load capacity Solid lubricants - reduce friction 17

Plastic Bearings Can (and Do) Outperform Metal Bearings Composite plastic bearings vs. simple plastic bearings Friction Wear Parameters: P = 0.7 N/mm2, v = 0.15 m/s, case-hardened steel shaft 18

Plastic Bearings Can (and Do) Outperform Metal Bearings Composite plastic bearings vs. bronze bearings 1930’s technology High speed and rotational movement necessary to draw oil out and create a lubricant film Shaft oscillation, slow speed, linear and intermittent use can all inhibit this process 19

Plastic Bearings Can (and Do) Outperform Metal Bearings Composite plastic bearings vs. bronze bearings Bronze bearings: + Low coefficient of friction (if maintained) + High speeds are possible + High p x v value - Limited application temperatures - Poor chemical/corrosion resistance - Not ideal in dirty environments - Must be reamed at install - Unsuitable for linear motions - Low impact load capability 20

Plastic Bearings Can (and Do) Outperform Metal Bearings Composite plastic bearings vs. bronze bearings Bronze bearings: + Higher load possible + No external lube or maintenance required + Better in aggressive environments + Ideal for rotating, pivoting and linear use + Great for impact loads and high-vibrations + Can use non-hardened shaft materials + Lightweight 21

Plastic Bearings Can (and Do) Outperform Metal Bearings Composite plastic bearings vs. bronze bearings Better lifetime than bronze Grease and oil-free Dirt and dust resistant Ideal in pivoting/intermittent applications Increased lifetime Easy to assemble (no reaming) Better suited for impact loads 22

Plastic Bearings Can (and Do) Outperform Metal Bearings Composite plastic bearings vs. PTFE, metal-backed bearings 1950’s technology steel/bronze outer layer is rolled ID contains thin layer of bronze Impregnated with PTFE and lead 23

Plastic Bearings Can (and Do) Outperform Metal Bearings Composite plastic bearings vs. PTFE, metal-backed bearings PTFE, metal-backed bearings: + Good thermal conductivity/heat dissipation + Ability to withstand high operating temperatures + Max. speed 1,000 fpm + PV 50,000 psi/fpm continuous + PV 100,000 psi/fpm short term - Thin wear surface - Corrosive - Heavier than plastic bearings - Difficult installation procedures 24

Plastic Bearings Can (and Do) Outperform Metal Bearings Composite plastic bearings vs. PTFE, metal-backed bearings Composite plastic bearings: + Suitable for a wide range of applications + Dimensionally Interchangeable + More wear surface + Lightweight + Corrosion-Resistant + Better for dirty environments + Predictable lifetime 25

Plastic Bearings Can (and Do) Outperform Metal Bearings PTFE-lined vs. igus® bearing wear Oscillating movement Parameters: Pressure = 1 MPa, Velocity = 0,01 m/s 26

Plastic Bearings Can (and Do) Outperform Metal Bearings PTFE-lined replaced with composite plastic “iglide® bearings cost slightly less, but the most important advantage is that they don’t need to be replaced by riders. They last for the entire life of our pedals.” Dirt and dust resistance Lightweight Corrosion resistance Proven to require less maintenance than the alternative in this application, plus a longer life 27

Plastic Bearings Can (and Do) Outperform Metal Bearings Recirculating ball bearings Balls run through a linear raceway Contain a lubrication-bath May require constant maintenance Additional components are often required: Zerks, lube lines, seals, etc. with plastic spacers standard version: one ball pushes the next 28

Plastic Bearings Can (and Do) Outperform Metal Bearings Recirculating linear ball bearings + Higher combination of dynamic load vs. speed + High precision possible (micron level) + Low friction (if properly maintained) + Suitable for highly cantilevered loads Expensive - Must be lubricated/maintained - Require hardened steel shafting - Poor in dirty environments - Not ideal for clean applications 29

Plastic Bearings Can (and Do) Outperform Metal Bearings Plastic linear bearings Lower cost of ownership Suitable for harsh environments (dirt, chemicals, water) ideal for high- impact loads (shocks/vibrations) Higher static loads than ball bearings Suitable for soft shafting (aluminum/300-SS) Suitable for short strokes Quiet/lightweight 30

Plastic Bearings Can (and Do) Outperform Metal Bearings Recirculating ball bearings replaced Vertical-Form-Fill-Seal packaging machine: Welding jaws + Increased machine’s cycles-per-minute by 20% + Ball bearings limited by accelerations and bad environments + Lower cost than ball bearings 31

Plastic Bearings Can (and Do) Outperform Metal Bearings Questions? Please post your questions into the chat window. I can also be contacted at the email address and phone number below. Nicole Lang igus® Product Manager Po Box 14349 East Providence, RI 02916 Tel: 401-438-2200 ext. 141 Fax: 401-438-7270 Email: nlang@igus.com 32