Why (and How) You Should Implement Plastic Bearings
 

Why (and How) You Should Implement Plastic Bearings

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Learn about the characteristics of plastic plain bearings, the different polymer materials available, and the many benefits that these types of bearings boast in comparison to metal bearing ...

Learn about the characteristics of plastic plain bearings, the different polymer materials available, and the many benefits that these types of bearings boast in comparison to metal bearing alternatives. Discover the advantages and limitations of plastic versus bronze bushings and ball-bearing systems, alongside specific application examples. Join igus in finding out how to implement plastic bearings into rotating, oscillating, and linear applications, and learn about potential applications for plastic bearings.
Watch this webinar to learn:
-What plastic bearings are and how they work
-Advantages and limitations of plastic bearings versus various alternatives
-How to design plastic bearings into different applications
-Review applications in which plastic bearings have already been implemented

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Why (and How) You Should Implement Plastic Bearings Why (and How) You Should Implement Plastic Bearings Presentation Transcript

  • Why (and how) You Should Implement Plastic Bearings
  • Before We Start  This webinar will be available afterwards at designworldonline.com & via email  Q&A at the end of the presentation  Hashtag for this webinar: #DWwebinar
  • Presenters Moderator Leslie Langnau Matt Mowry Design World igus Nicole Lang Donna Meyer igus University of Rhode Island
  • Why (and how) to implement plastic bearings into your application.
  • • Development • Advantages • Simple polymers vs. composite polymers • Selection criteria
  • Polymers in general • • • • Natural polymer lubricants Oils and greases Incorporated into solids Plastics and rubbers
  • Why use polymer bearings? • • • • Fluid lubricants not effective Fluid lubricants not safe Maintenance issues Insufficient boundary lubrication
  • Possible environments MARINE: seawater and fresh water
  • Possible environments AGRICULTURE: moisture, chemicals, dirt
  • Possible environments MEDICAL: equipment, implantable devices
  • Possible environments PACKAGING: food and pharmaceuticals
  • 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.
  • 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.
  • 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.
  • Composite polymers • Improved mechanical strength • Improved wear resistance • Reduce coefficients of friction Stachowiak & Batchelor,, Engineering Tribology, 2005, 3rd Ed., Elsevier Inc., Chp. 16, Fig.16.29, pp. 677. Tsukizoe & Ohmae, Friction and Wear of Polymer Composites,1986, K. Friedrich, Ed, pp.205-231.
  • Composite polymer bearing 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. Solid lubricants lubricate the system independently, mitigating friction and reducing wear rates
  • Advantages of composite polymers • • • • Improve mechanical and thermal properties Addition of reinforcing fibers and fillers Reduce wear rates Effective under high and low loads
  • More advantages . . . • • • • • • • Low friction coefficients with mating materials Inert Biocompatible Self-lubricating Serve as reservoir for boundary lubricants Tune material properties Make into any shape: molding or machining
  • Selection criteria • • • • • • Maximum load Sliding speed Environmental conditions Counterface roughness PV limit Wear factor k Stachowiak & Batchelor,, Engineering Tribology, 2005, 3rd Ed, Elsevier Inc., pp. 658-659. Arnell, Tribology: principles and design applications, 1991, Macmillan, pp. 1111-112. Khonsari,& Booser, Applied Tribology: Bearing Design and Lubrication, 2008, Wiley & Sons, pp. 356-358. Blanchet, (1997), ‘‘The Interaction of Wear and Dynamics of a Simple Mechanism,’’ ASME J. Tribol., 119, pp. 597–599.
  • Composite plastic bearings vs. - simple plastic bearings - bronze bearings - PTFE-lined, metal-backed bearings - ball bearings
  • Composite plastic bearings vs. simple plastic bearings • Composites enhance the benefits of plastics • Base materials • Fillers - increase load capacity • Solid lubricants - reduce friction
  • Composite plastic bearings vs. simple plastic bearings Polyamide 6.6 100 Polyamide 6.6 100 Polyacetal (POM) 90 Polyacetal (POM) 90 igus L280 70 60 80 igus H370 igus J 80 70 igus L280 60 igus J igus H370 50 50 40 40 30 30 20 20 10 10 0 0 material material Friction Wear Parameters: P = 0.7 N/mm2, v = 0.15 m/s, case-hardened steel shaft
  • 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 “Shaft oscillation or slow speed, intermittent use, pulsating or uneven loads are conditions that inhibit full-film lubrication from developing or being maintained” – from oilite manufacturer’s product information
  • Composite plastic bearings vs. bronze bearings Bronze bearings: + low coefficient of friction (if maintained) + slightly more precise (low thermal expansion) + 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
  • Composite plastic bearings vs. bronze bearings Composite plastic bearings: + higher load possible iglide® composite bearing: <21,500 psi bronze bearing: <8000 psi + 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
  • 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 • • • •
  • 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
  • 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 - contain lead - heavier than plastic bearings - difficult installation procedures
  • 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
  • PTFE-lined vs. iglide® bearing - wear Oscillating movement 5 4.5 4 3.5 3 igus J igus L280 igus Z PTFE-Lined 2.5 2 1.5 1 0.5 0 HC AL Case-HardSteel Machine Grade 304SS Parameters: Pressure = 1 MPa, Velocity = 0,01 m/s
  • 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
  • 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
  • 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 - limited accelerations possible
  • 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
  • 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
  • Implementing iglide® plastic bearings in your application
  • iglide® plastic bearings • Check temperature, static-surface pressure, speed. • Max. P x V value is  28 571 Psi * fpm in a permanently dry-running application. • Typical application involves low speeds < 60 fpm or high loads up to 14,500 psi (rotating oscillating.) • Use hardened shaft in applications > 700 psi • When the total sliding distance is less than 6,000 miles • Use a clearance of 0.002” – 0.004” (0.05 - 0.10 mm)
  • PV Value • In a plain bearing, friction heat is created when the shaft moves inside the bearing. • We determine p*v by the values present in the application for pressure and speed. • By multiplying these two factors we find the p*v (measure for the amount of heat created): o Pressure in psi o Velocity in fpm
  • PV Value 2 ways to dissipate the heat from the bearing: Via the bearing into the housing Via the shaft outside the bearing
  • Factors influencing PV • Thermal conductivity of shaft, housing and bearing material. • Coefficient of friction. • Maximum temperature limit of the bearing material. • Ambient temperature in the application. • Wall thickness of the bearing and length.
  • The 2:1 Rule
  • Other considerations • • • • • • • Shaft material Shaft roughness Shaft hardness Housing material Environment Chemicals Certifications (ex. FDA compliance, UL94 horizontal burn test etc.)
  • What is iglide®? iglide® bearings are engineered plastics  More than 30 iglide® materials:  iglide® bearings are available in more than 30 tribopolymers to meet your specific needs.  More than 150 additional materials for special custom requests or needs.  All tested and predictable. more than 30 dry-tech tribopolymer materials dry-tech
  • The igus® test facility Over 10,000 plastic bearing tests annually Focus on coefficients of friction and wear under all possible conditions and at a wide range of speeds. Factors such as dirt and climate also tested.
  • Founded: October 1964, Cologne Germany Approx. 1,600 employees in inland and overseas 28 igus® subsidiaries worldwide and distributors in more than 42 countries. Product groups: - Energy Chain® cable carriers - Chainflex® continuous-flex cables - ReadyChain® pre-harnessed systems - iglide® polymer plain bearings - igubal® self-aligning plastic bearings - DryLin® linear bearings igus®, Inc. •US, Canada, Mexico •More than 50 Sales Engineers Throughout North America and in our Rhode Island office available for support •Available for visits within 24-48 hours •Stock held in East Providence, RI •No Minimum Orders •Over 10,000 sizes available in stock ready to ship within 24 hours
  • Contact Us sales@igus.com Tel. (800) 521-2747 or (401) 438-2200 Twitter: http://www.twitter.com/igus_Inc http://www.igus.com
  • Questions? Design World Leslie Langnau LLangnau@wtwhmedia.com Phone: 440-234-4531 Twitter: @DW_RapidMFG igus Matt Mowry Mmowry@igus.com Phone: 888-803-1895 ext. 140 Twitter: @igus_inc University of Rhode Island Donna Meyer dmmeyer@egr.uri.edu igus Nicole Lang Nlang@igus.com Phone: 888-803-1895 ext. 111 Twitter: @igus_inc
  • Thank You  This webinar will be available at designworldonline.com & via email  Tweet with hashtag #DWwebinar  Connect with  Twitter: @DesignWorld  Facebook: facebook.com/engineeringexchange  LinkedIn: Design World Group  YouTube: youtube.com/designworldvideo  Discuss this on EngineeringExchange.com