The Overall Equipment Effectiveness (OEE) datasets (before and after Lean Six Sigma implementation) contain line-level OEE data per shift. Column labels are: Shift Date, OEE, Availability, Performance, Quality, Sum of Good Production Time, Sum of Slow Production Time, Sum of Planned time, Sum of ideal Production Quantity, Sum of planned Stops Time (sec), Sum of unplanned Stops Time (sec), Sum of Good Quantity, Sum of Total Quantity. Descriptive data are written in the English language. The Downtime datasets (before and after Lean Six Sigma implementation) contain downtime data, such as duration, stop locations, stop reasons, and operator comments. Specifially column labels are: Date, Product Code, Stop Reason, Stop Type, Stop Location, Extra Text (from operator), Stop start time, Stop end Time and Stop duration (min). Descriptive data are written in the English language, except for the extra text field (input by the machine operator) that was kept in Greek to maintain raw data and avoid translation mistakes. Data collection was implemented through real-time OEE tracking specialised software (Evocon). The data correspond to the whole production line, ranging from clay extrusion to brick packaging.