Slide bearings - Wolf Kunststoff-Gleitlager GmbH

wobei:∆Sϑz=LagerspielveränderungdurchTemperaturver-änderungvonungeschlitztenBuchsen[m]αBu=AusdehnungskoefizientdesGleitlagersausTab.x[1/?C]∆ϑ=Temperaturveränderung[?C]d2=[m]Buchsenaußendurchmeser[4]∆SϑzαGeh=AusdehnungskoefizientdesGehäusesausTab.x[1/?C]∆ϑα?(d(2?Bu-)+d?αGehw1)d1=Buchseninendurchmeser[m]αw=AusdehnungskoefizientdesGehäusesausTab.x[1/?C]CCCCCC12.2.1. pv-value checkIn order to ascertain the occuring stress exerted on theslide bearing we have to calculate the pv-value.The pv-value reflects the power density inducted intothe system casing-slide bearing-screw.The following condition must be complied in order toavoid a thermal overloading of the slide bearing:Appearing pv-value12.2.1.1.3. Maximum pv-valuepv = p • v[11]in which:pv = maximum pv-value [N/mm 2 • m/min]p = surface pressure taken from 12.2.1.1.1 [ N/mm 2 ]v = sliding speed taken from 12.2.1.1.2. [m/min]PrefaceContentspvpvpvEDin which:EDzul< pvzul[8]= appearing pv-value [N/mm2• m/min]2= permissible pv-value [N/mm • m/min]12.2.1.1.4. Appearing pv-value pv EDThe pv-value (pv ED) appearing on respective switch-onduration (ED) can be calculated according to formula (12).Materialoverview12.2.1.1. pv-value (pv) of the radial slidebearing12.2.1.1.1. Surface pressureskbdIll. 20 Dimensions of the radial slide bearingpFb . din which:2p= medium surface pressure [N/mm ]F= radial stress exerted on the slide bearing [N]b= width of the slide bearing [mm]d= screw diameter [mm]ød 112.2.1.1.2. Sliding speedøDThe sliding speed occuring between the screw and theslide bearing surface can be calculated according toformula (10).vd . n . π1000øD1[9]in which:v= occuring sliding speed [ m/min]d= screw diameter [mm]n= screw speed [min-1][10]12.2.1.1.4.1. Correction factor f for intermittentoperationOn intermittent operation the energy inducted into thesystem is reduced, so that the appearing pv-value canbe corrected downwards. The correction factor f shouldonly be applied when the following condition(13) is completed:Ill. 21: Exemplary course of screw speed above thetime tWolf Kunststoff-Gleitlager GmbH • Heisenbergstr. 63 - 65 • 50169 Kerpen-Türnich • Tel. 02237/9749-0 • Fax. 02237/9749-20pv EDp . v[12]in which:pv = appearing pv-value [N/mm 2ED• m/min]p = surface pressure taken from12.2.1.1.1. [ N/mm 2 ]v = sliding speed taken from 12.2.1.1.2. [m/min]frotation. f= correction factor for switch-on duration taken from12.2.1.1.4.1. [-]screw speed ndowntimet L < tL maxin which:tL= transit time [s]t Lmax = max. permissible transit time taken from[s] ill. 23t LΣt + tP Σ Lt P[13]time tIndex Slide bearings Slide bearings Conditions ofTribologyMathematical Design(with collar) (cylindrical) installationexample guidelines32