Comparative fatigue lives of rubber and pvc wiper cylindrical coatings

Three coating materials for rotating, cylindrical, coated wiping rollers were fatigue tested in two Intaglio printing presses. The coatings were a hard, cross-linked, plasticized polyvinyl chloride (PVC) thermoset (P-series); a plasticized PVC (A-series); and a hard nitrile rubber (R-series). Both two- and three-parameter Weibull analyses and a cost-benefit analysis were performed. The mean value of life for the R-series coating is 24 and 9 times longer than that of the P- and A-series coatings, respectively. At a very high probability of survival, the R-series coating is approximately 2 and 6 times the lives of the P- and A-series, respectively, before the first failure occurs. The cost and replacement rate for the R-series coating is significantly less than those for the P- and A- series coatings. When all coatings are run to failure, using the mean (life) time between removal (MTBR) for each coating to calculate the number of replacements and costs provides qualitatively similar results to those using a Weibull analysis. For these coatings, at a given operating temperature, the higher that temperature above the glass transition temperature, the longer the fatigue life.