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

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

3. 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

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

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

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

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

8. 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
Makinson & Tabor, (1964), “The Friction and Transfer of Polytetrafluoroethylene”, Proc. Roy. Soc. (A), 281, pp 8

9. 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 9

10. 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
Arnell, Tribology: principles and design applications, 1991, Macmillan, pp. 110.
Khonsari,& Booser, Applied Tribology: Bearing Design and Lubrication, 2008, Wiley & Sons, pp.97. 10

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

12. 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

13. 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

14. 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

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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. 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

28. 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

29. 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

30. 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

31. 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

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