Wrinkling of Webs Approaching Heated Rollers

Abstract

There are several reasons webs wrinkle when passing over rollers. Some of the reasons for wrinkles on web are roller misalignment, tapered rollers, decrease in web tension, difference in web thickness etc. The scope this research is to investigate web instability due to the effect of temperature on web material passing over a heated roller. A heated roller was setup on the small scale web transport machine. Wrinkling experiments were run by passing LDPE web material over the heated aluminum roller in bare condition and also with high friction tape. Input parameters like Young's Modulus, web lateral expansion value required for FE simulations was also found by tests. Both static and non-linear FE simulations were performed and results were compared with the experimental observations and theoretical calculations. Experimental results show the LDPE web expands on a bare aluminum roller. Troughs are generated on entry span of the heated roller. Wrinkles are formed on the heated roller surface. In high friction case, no troughs or wrinkles are observed. The static and non-linear FE simulation results correlated well with the experimental observations and theoretical calculations. It has been shown herein that, web instabilities like troughs and wrinkles can be generated on these LDPE webs due to increase in temperature. On bare aluminum roller, the web has a non normal entry due to expansion which results in steering of outer edges inward leading to formation of troughs on the entry span and then finally wrinkles on roller surface. In high friction roller case, the outer edges on the heated roller do not expand due to high friction, which provide no inward steering and hence no troughs or wrinkles are formed.