Simultaneous cutting of two separate sheets using plasma and parameters optimisation

Student thesis: Doctoral Thesis

Abstract

This thesis investigates on the ability of using plasma technique for cutting simultaneously two parallel thin layers at different gap distances. Previous research emphasised that plasma cutting can be optimised to improve the quality and reduce phenomena. The investigation performed previously was made primarily in two-dimensional cutting plan. However, there is a lack of publication and research regarding optimisation of a three-dimensional structure cutting. This current work would help engineers to understand the practicability of thermal cutting such as plasma to process zones in the vehicle chassis similar to box sections or double layered areas. This research is aimed at wheelchair accessible vehicle converters that performs modifications in the chassis floor. This work is part of the engineering doctorate program. The research questions raised of this study lie primarily on assessing the possibility of simultaneous cutting of a double sheet (separated with an air distance) using plasma, expressly examining the possibility to reuse the energy heat exiting the first sheet's kerf to perform a cut on the second layer. In addition, optimising the double sheets cutting, analysing the effect of the heat on thin material and reduce the resulting phenomena to their lower level (mainly surface deformation and heat affected zones). Lastly, assess the relationship strength between the parameters and the quality. Experiments were performed in four progressive phases. The first step was made to test the suitability of the plasma to process single thin sheets of 0.6 mm thick. This step was required to analyse the impact of the heat on the surface deformation and then optimise the cutting to improve the quality. The second phase of the tests were performed to verify the plasma ability to process a 3D-Structure such as double layered zones. The third phase of test was made to assess the cutting parameters suitable to process two layers simultaneously at a fixed gap 20 mm. These parameters were used as a reference for the following stage. The fourth phase was performed to optimise the double sheets structure cutting process (separated with an air distance) and minimise the impact of the heat generated during the plasma cutting on the top sheet. The Hypothesis of re-using the heat was tested and proven true, it is possible to re-employ the heat energy exiting the kerf to perform another cut. The tests showed that there was a considerable heat impact on the surface. However, this can be controlled and reduced. Cutting two sheets simultaneously may result to an offset between the top and bottom edge of the cut. Optimisation using the DOE based Taguchi approach resulted to an improvement in quality and the regression analysis showed a good fit of the models constructed, none of the values measured were outside the interval of prediction. Final tests were performed on a vehicle chassis and the results showed that a good automation can reduce the cutting process by approximatively 40min compared to manual cutting.
Date of Award15 Sep 2021
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorWilliam Ion (Supervisor) & Erfu Yang (Supervisor)

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