One of the most important activities in the management of companies is the continuous improvement of products quality concerning their sustainability and better market position. The submitted paper aims to optimise the production process in the production of weldments. The study revealed a significant number of dimensional and threaded defects on the welded chassis of the loader. One possibility of continuously increasing the required performance of a company is to eliminate the number of non-conforming products using the tools of the Six Sigma methodology. This policy must be introduced by a company into the business processes management if a company wants to successfully meet the customers´ needs and improve the processes while cutting the costs of production. The resulting analysis focused on the selected type of defects to reduce their occurrence using the Six Sigma tools, specifically the DMAIC improvement cycle. The presented approach and the results obtained highlight the importance of applying quality tools in practice and their undeniable contribution in improving performance and quality, reducing the number of defects occurring and reducing the cost of poor quality in production, both now and in the future.