## 3 The Case Study of Renault Cacia Factory  
This article follows qualitative, exploratory, and descriptive case study research. Specifically, it investigates the maintenance projects at a well-known Renault factory (also known as Renault Cacia) that has been operating in Portugal for over 40 years [62]. Given that case studies typically aim to understand and describe a particular real-life phenomenon [63], the choice of Renault Cacia as the unit of analysis seemed appropriate. First, it is a reference in the international segment of the automotive industry, producing  
Figure 3: Factory maintenance: (**a**) Predictive maintenance (example); (**b**) Condition-based maintenance (example). large volumes of gearboxes and other mechanical engine components. Further, it carries out several successful maintenance projects that end up justifying the relevance of this research. Through the use of several data collection techniques, ranging from semi-structured interviews to participant observation and analysis of organizational documents, we sought to understand how the latest maintenance projects were carried out at the factory. Thus, this study reports on the: (1) contributions of the project leaders, operators, maintenance group, and elements of the engineering department; (2) analysis of the operators' behavior and reactions to the implementation of new maintenance projects at the factory; (3) analysis of the technical documents of the test bench, notably the component maintenance plan, the technical recommendations of the factory suppliers and the Failure Mode and Effect Analysis (FMEA) reports. The group of interviewees included informants with high technical knowledge and who could observe the phenomenon from different angles. As such, they were chosen from different areas, i.e., project leader, maintenance group, and engineering department. We used an interview protocol that served to establish a consistent standard to compare participants' responses, assisting in identifying and mitigating inconsistencies [64]. The interviews were transcribed and discussed with all informants so that there were no errors in interpretation and to understand all contextual details, a procedure that allowed to increase the research validity [65]. It is worth highlighting the valuable contribution of Renault engineers, who actively participated in the validation of the article results. The participant observation and documental analysis were very relevant as secondary sources in that they allowed corroborating the information collected through the interviews [66]. The participant observation was useful because it allowed seeing the phenomenon first hand, but also because it allowed close interaction with operators. To corroborate the data collected from the interviews, we photographed a series of maintenance activities [67]. A diary was used [68] to record all observations in loco (i.e., description of the photographs) and informal conversations that occurred throughout the research. This data collection source allowed to clarify issues that were raised during the interview phase. Lastly, the official documents (e.g., FMEA reports) associated with the project enabled a better understanding of the overall process and associated technologies. The secondary sources allowed to increase the research's reliability, as they contributed to triangulate and corroborate the data obtained during the interviews phase [66]. The studied process includes a part of the JT4 gearbox project, namely, one of its components--the JT4 mechanism crankcase (MC). This structure is a metallic container of a single reference that protects and fits into other gearbox components, as can be observed in Figure 4.  
The initial step of the research was to understand the manufacturing process of the crankcase mechanism, whose line is called module 1 (M1). Renault Cacia buys the raw parts abroad, which logistics providers transport to the storage area of the production line using automated guided vehicles (AGV).