Critical evaluation of the theory of constraints lean six sigma continuous improvement management approach
Van Tonder, Rojanette
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Three methodologies are associated with production optimisation, namely, Theory of Constraints (TOC), Lean and Six Sigma – and each boasts with a number of success stories. This dissertation addresses the possibility of implementing all three these methodologies in a specific sequence at an organisation and also sets out to determine the impact of this implementation. A literature survey was conducted on all three stand-alone methodologies as well as on the combined methodology, which is called the Theory of Constrains Lean Six Sigma (TLS). TLS literature suggests that TOC should be implemented first with a view to identify the constraint in an organisation. Lean implementation should follow in order to eliminate any waste in the organisation. Lastly, Six Sigma should be implemented to optimise the process variability. TOC literature explains that The Goal of any organisation is to make money. All other objectives are only the means of achieving The Goal. The literature further indicates that the constraint in any organisation determines the drumbeat, and that this constraint should be managed by means of the Drum-Buffer-Rope methodology. Lean literature points towards 14 Management Principles by means of which an organisation should be managed in order to become a Lean organisation, while Six Sigma literature is concerned with the DMAIC (Define-Measure-Analyse-Improve-Control) methodology used for improvement projects and the belt system that is used to manage these improvement projects. Jonker Sailplanes, a sailplanes manufacturer in Potchefstroom, South Africa, was used as a case study for the implementation of TLS. A description is given of the processes and procedures that were followed before and after the implementation of TLS. The TLS methodology had to be adapted in order to meet the specific needs of Jonker Sailplanes into an adapted 14-step TLS implementation plan. After implementing TOC and Lean at Jonker Sailplanes, it was found that the organisation was not ready for the transition from Lean projects to Six Sigma projects. The implementation of Six Sigma was therefore referred for future research. One of the most significant findings of the current study was the very positive impact that the implementation of TLS had on the organisation: the production tempo (throughput) of the organisation has increased while the operating expenses per aircraft have decreased. This confirms that the profit per aircraft has increased. A critical evaluation of the implementation of the TLS methodology can therefore maintain that the implementation of TLS at Jonker Sailplanes was a success since the production tempo (throughput) and the organisational profit were increased and the implementation of the methodology was done with relative ease. In terms of interpreting results it was also necessary to set out how Jonker Sailplanes proceeded from a prototyping environment to a production setup, and how specifically identifying the constraint helped to achieve this transition. Furthermore, is it argued that when Lean is implemented before TOC, this could move the organisation away from The Goal, which is to make money. The interpretation of findings suggests that the procedure followed at Jonker Sailplanes was the most appropriate one. Finally, recommendations are made for future studies in terms of how to further improve the impact of the TLS implementation at Jonker Sailplanes.
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