Effect of flow forming on ultimate stress of flow formed Polyethylene Pipes

Flow forming is an advanced, chip-less and cost-effective forming process to produce precise, seamless, axi-symmetric tubular products. This study was carried out to investigate the applicability of flow forming on polyethylene pipes and the effect of process parameters on ultimate stress of flow formed parts. The experiments were carried out using a HDPE80 tubular preform. Thickness reduction ratio, Feed rate and rotation speed of mandrel were considered as variables. A set of roller and mandrel was designed and manufactured to convert an NC lathe to a single roller flow forming machine. This present investigation uses Taguchi method, which is a powerful design of experiments tool. This method provides a simple, efficient and systematic approach to determine optimal forming parameters. An L9 orthogonal array of Taguchi method was applied to carry out the design of experiments. A tensile test machine was used to measure the tensile properties of specimens. The analysis of result was performed based on ―average of results‖ and analysis of variance. Through ANOVA analysis it was revealed that the thickness reduction ratio is the most significant variable that affects the ultimate stress followed by rotation speed of mandrel. The maximum ultimate stress of 17.5 MPa was obtained when variable parameters were adjusted at optimum values. Comparison of optimum value of ultimate stress and normal specimen showed 66% improvement of ultimate stress that is totally significant.