This research aims to optimize the CAPEX purchasing process in a large polymetallic mining company, evaluating the problems and bottlenecks present in this process. The methodology presented focuses on the exhaustive collection of quantitative and qualitative data, as well as on the implementation of strategies based on Lean methodologies such as Just in Time and Muda. As a result, there is a significant reduction in delivery times for purchase orders, as well as an improvement in efficiency and overall process performance, validated by statistical analysis and simulations in ARENA software. The conclusion is that the implementation of the Just in Time and Muda strategies has proven to be effective in optimizing the CAPEX purchasing process, with positive impacts on operational efficiency and reduction of times with a 95% confidence level. It is recommended to continue exploring the potential of the Just in Time methodology in international environments and to monitor the improvements implemented in the long term.