Proceedings of SerbiaTrib '13

4. PLASTIC BEARING APPLICATIONSRegarding their advantages, plastic bearings aregood solution for many applications in machinerythat require clean and oil-free operation. They alsoperform well in dirty environments since there is nooil to attract dust and dirt, like the agriculturalindustry. Some manufactures creates individualplanting row units using walking gauge wheels todeliver a consistent planting depth (Figure 4).successfully used with shafts made of bronze andsteels of different hardness and structure.Figure 4. Plastic bearing application in agricultureOil impregnated bronze bearings with graphiteplugs were used to facilitate this movement untilthey began causing severe problems. They wereeven requiring replacement two to three times aseason. But the bronze bearings were experiencinghigh wear and premature failure due to the veryabrasive conditions caused by high levels ofvolcanic ash in the soil, or the high salt content inthe air caused corrosion and seizure. By replacingall 144 bronze bearings with iglide® selflubricatingplastic bearings from igus®, the pick arms lif wasincreased by 5 to 6 times. The actual bearings cost70 to 80 percent less than bronze bearings and weremore reliable.Shipbuilding and hydraulic turbine buildinghave accumulated much experience with the use ofsliding bearings made of UGET carbon plastic [7].These include friction units of a driving rudder setof ships of different types and design (supports forrudders and rudder machines) with regard tostabilizers, interceptors, drives for actuators ofKingston valve type, and scupper screens, as wellas mast elevating extending devices andmechanisms (Figure 5). Sliding bearings have beenpreviously made of bronze, and shafts have beenmade of a corrosion resistant material having ratherlow antifriction characteristics, corrosion resistantsteel or titanium alloys. Therefore, in the absence ofreliable oil lubrication system there is a danger ofseizure of metallic bearings, which may result inthe failure of the whole mechanism. UGET carbonplastic containing poly functional epoxy resin andtissue of low module carbon fibre was developed.Bearings made of UGET carbon plastic areFigure 5. Sliding friction unit of a hydraulic turbineOne manufacturer specializes in vertical, form,fill and seal packaging equipment for handling awide range of products: from green beans to candyto detergent. The machines are capable of reachingup to 160 cycles per minute and withstanding loadsup to 15 pounds, while operating at speeds of 750feet per minute (Figure 6).The manufacturer had been using metal linearball bearings. After the metal bearings scored theshafts and leaked grease on some of the machines,the company decided to replace them with selflubricating linear plain bearings. To date, the linearbushings have surpassed the 10 million cycle markon some of the company’s packaging machineswith little to no noticeable wear.Figure 6. Packaging machine with plastic bushingsIn the quest to improve the way prostate canceris detected and treated, a team of researchers fromthe Worcester Polytechnic Institute (WPI) inMassachusetts have developed a specializedmagnetic resonance imaging (MRI) compatiblepiezoelectric actuated robot [1]. To facilitate13 th International Conference on Tribology – Serbiatrib’13 249