Slide bearings - Wolf Kunststoff-Gleitlager GmbH

CCCCCC5.2.4. Operating bearing clearanceThe operating bearing clearance appears when the bushingis working on operational conditions. It basicallydiffers from the installation bearing clearance regardingthe dimensional changes, which are caused by the stressexerted on the slide bearing and the influence of theambient temperature.5.2.4.1. Changes in bearing clearance due tohumidityThe slide bearings made from plastic alloys of the ZXseriesdo not undergo a considerable change in bearingclearance due to atmospheric humidity.Even when operating directly in water, no ZX-materialshows a considerable dimensional change.5.2.4.2. Changes in bearing clearance due totemperatureOwing to the fact, that the linear coefficients of expansionof plastic alloys of the ZX-series are seven times biggerthan those of steel alloys, the operating bearing clearanceis reduced with increasing temperature depending on thecasing and the slide bearing material.The operating bearing clearance of non-slitted bushingsyields from the following formula (6):∆S ϑZ= ∆ϑ•( •( α - α ) - d 1 • α )in which:∆S ϑZ∆ϑ= change in bearing clearance due to temperaturechanges of non slitted bushings[mm]= temperature changes [ºC]d 2 = outside diameter of the bushing [mm]α Buα Gehd 1α wd 2GehBu= coefficient of expansion of the slide bearingtaken from table 6 [1/ºC]= coefficient of expansion of the casingtaken from table 6 [1/ºC]= inside diameter of the bushing [mm]Bearing clearance[6]= coefficient of expansion of the screw taken fromtable 6 [1/ºC]WThe operating bearing clearance of slit-shapedbushings yields from the following formula (7):material∆S ϑS= ∆ϑ•(d 2 • αGeh - d 1 • αW- 2•skBu • αBu)in which:∆S ϑS = change in bearing clearance due to temperature∆ϑd 2α Buchanges of slit-shaped bushings [mm]= temperature changes [ºC]= outside diameter of the bushing [mm]= coefficient of expansion of the slide bearingtaken from table 6 [1/ºC]α Geh = coefficient of expansion of the casingd 1α wsk Bu =taken from table 6 [1/ºC]= inside diameter of the bushing [mm]coefficient ofexpansion up to50 °C(1/K)coefficient ofexpansion up to80 °C(1/K)coefficient ofexpansion up to100 °C(1/K)coefficient ofexpansion up to150 °C(1/K)ZX-100A 6,6*10 -5 6,9*10 -5 8,7*10 -5 13,2*10 -5ZX-100EL63 14*10 -5ZX-100K 6*10 -5 7*10 -5 8*10 -5 12*10 -5ZX-100MT 5,5*10 -5 6,2*10 -5 7,1*10 -5 10,7*10 -5coefficient ofexpansion up to200 °C(1/K)ZX-324 5,6*10 -5 5,9*10 -5 9,5*10 -5ZX-324V1T 5,6*10 -5 5,9*10 -5 9,5*10 -5coefficient ofexpansion up to250 °C(1/K)ZX-324V2T 6,2*10-5 6,5*10-5 10,4*10-5ZX-324V3T 4,8*10 -5 5,0*10 -5 9,6*10 -5ZX-324VMT 3,5*10 -5 3,8*10 -5 6,9*10 -5ZX-410 5,5*10 -5 5,8*10 -5ZX-530 6,0*10 -5 9,0*10 -5ZX-550 12*10 -5 16*10 -5ZX-720 14,4*10 -5 19,2*10 -5ZX-750V1 3,2*10 -5ZX-750V2 3*10 -5ZX-750V3 3,6*10 -5ZX-750V4 6,2*10 -5 6,5*10 -5 10,4*10 -5steel 1,2*10 -5cast iron 1,05*10 -5aluminium 2,38*10 -5brass 1,85*10 -5Table 6: Thermal coefficient of linear expansion[7]= coefficient of expansion of the casing taken fromtable 6 [1/ºC]wall thickness of the bushing [mm] = (d2- d1) / 2Attention:Slit-shaped bushings which are sticked in do not changetheir inside diameter due to temperature changes (seechapter 4.2.1.).PrefaceContentsMaterialoverviewIndex Slide bearings Slide bearings Conditions ofTribologyMathematical Design(with collar) (cylindrical) installationexample guidelinesWolf Kunststoff-Gleitlager GmbH • Heisenbergstr. 63 - 65 • 50169 Kerpen-Türnich • Tel. 02237/9749-0 • Fax. 02237/9749-2017