## 3 Literature Review
### PDCA Cycle  
The PDCA cycle, also known as Deming cycle or Shewhart cycle [23], is a lean manufacturing methodology that was developed in 1930, when there was no more exclusive products and a more quality management focusing on competitiveness raised in the global market [24; 25]. According to several authors, the creator of the original PDCA cycle was an American statistician named [PERSON] [25; 26]. However, [PERSON] was who, in the 1950s, developed this method, which, today, is one of the most worldwide known and applied. In its beginnings, the PDCA cycle was used as a tool for the quality control of products [25; 27]. However, rapidly, it was highlighted as a method that allowed developing improvements in process at organizational level [25; 27; 28]. Currently, the PDCA cycle is characterized by its continuous improvement approach [29] and it is recognized as a logic program that allows improving the activities [27; 30]. Several authors state that the PDCA cycle is much more than a simple lean manufacturing tool. Instead, they mention that the PDCA cycle is a philosophy of continuous processes improvement introduced in the organizational culture of companies [20] that is focused in the continuous learning and the knowledge creation [27; 31]. The following rows describe the four stages of the PDCA cycle [32]:  
* Plan: In this phase improvements opportunities are identified, and later priorities are assigned to them. Likewise, the current situation of the process to be analyzed is defined by means of consistent data, the problem causes are determined, and possible solutions are proposed to solve it. * Do: In this phase, it is intended to implement the action plan, select and document the information. Also, unexpected events, learned lessons and the acquired knowledge must be considered. * Check: In this step, the results of the actions implemented in the before step are analyzed. A before-and-after comparison is performed verifying whether there were improvements and if the stablished objectives were achieved. To this, several graphic support tools, such as Pareto chart or Ishikawa diagram, can be used. * Act: This phase consists in developing methods aimed to standardize the improvements (in the case objectives had been reached). In addition, the proof is repeated to obtain new data and re-test the improvement (only if data are insufficient or circumstances had changed), or the project is abandoned and a new one is begun from the first stage (in the case the implemented actions did not yield effective improvements). To perform these steps in an effective manner, other quality tools can be required to be used. These quality tools can help mainly to analyze the problem and define the actions to be implemented [25]. According to several authors [25; 33], among the quality tools most used by the companies, and that serve as support to the PDCA cycle, are the 5S, Failure Mode Analysis and Effects (FMEA), 5W1H o 5W2H, brainstorming, benchmarking; statistical process control (SPC), checklists, Ishikawa diagrams and the Pareto chart, Quality Function Deployment (QFD), the flowchart, histograms, Single Minute Exchange of Die (SMED), Poka Yoke, Servqual, times quality, and Six Sigma. In this project the graphical tools of Pareto chart and the flowchart are used. Literature shows that different applications of PDCA cycle have been implemented with positive results achieving the reduction of costs and defects, as well as improving the quality of process and products. In this regard, [PERSON], [PERSON], and [PERSON] [16] developed an integrated literature based Total Productive Maintenance (TPM), Toyota Production System (TPS), and Total Quality Management (TQM) model through PDCA cycle, and implementation guideline for the application of the model. Previous very few studies of uniqueness, common practices, and implementation guideline of the three systems are preserved. The findings of this research, an integrated cutting-edge model of TPM, TPS, and TQM practices and implementation guidelines are developed.