Experimental investigation of plasma cutting two separate thin steel sheets simultaneously and parameters optimisation using Taguchi approach

This article investigates the ability of using plasma machining for cutting simultaneously two parallel thin layers at different gap distances. The main aim of this work is to identify whether this technology if mechanized can be more appropriate than using a circular saw to process a three-dimensional structure material such as double layers, box sections or rails. This research is aimed at those working in the automotive industry and converting vehicles. Test models were built for the experiments using 0.7 mm thick steel sheets DCO1 grade, similar material used for some underbody vehicle chassis parts. Serie of cuts were carried out first to analyze the ability of the plasma to perform a simultaneous cutting in two separate sheets with an air gap, followed by tests to minimize the deformation and heat affected zones on the top sheets adopting Taguchi methodology. Parameters analyzed included cutting speed, intensity, pressure, and gap distance between the two sheets. The specimens collected were assessed for quality including Kerf, dross, hardness, offset distance between the top and bottom cut edge, sheet deformation and heat affected zones. The experiments showed the possibility to use plasma to cut in more than one sheet with one pass even if layers are separated with air distance. Analysis of variance showed that the input-controlled parameters which had the most influence on the top sheet deformation and HAZ were respectively intensity and gap. Regression equations showed a good model fit and the relationship between the input and output variables were strong. Results revealed that plasma could be an alternative tool if optimized to process three-dimensional structure parts, but it is dependent on the tolerances and the quality required.