**2. Origins of lean manufacturing**

Lean Manufacturing has its roots in the Toyota Production System originated at Toyota Motor Company by Taiichi Ohno and Shigeo Shingo [1]. It focuses on developing high quality, low cost products using less time, less space, fewer workers, and fewer tools.

After the First World War, Henry Ford and Alfred Sloan (General Motors) changed artisan manufacturing – used for centuries and directed by European companies– for mass manufacturing. Largely as a result, the United States soon dominated the world economy [2].

In 1950 Eiji Toyoda visited Ford's Rouge plant in Detroit for three months, an uncle had visited it in 1929. The Toyota Motor Company was founded in 1937. In 1950, after 13 years of work and effort they produced 2,685 automobiles, compared with the 7,000 they produced daily.

According to [3] Toyota's way of achieving a "lean" approach was to eliminate all waste, that is, activities that do not add value to the product from the customer's point of view. This allows reducing costs and increasing productivity. However, waste disposal is not enough because it requires a context and a culture, known and understood by all stakeholders (senior management, collaborators and suppliers). The Toyota way in a model is in a pyramid representing Toyota culture from top to bottom. This is the 4P model: 1) a philosophy of long-term thinking; 2) continuous process improvement to eliminate waste; 3) People and partners respect, challenge and grow; 4) Problem solving through continuous improvement and learning.

To locate the origin of the word lean, it is necessary to name JP Womack, and Daniel Jones, two researchers from the United States and from England, respectively, who are referents in this matter, through their work entitled "Lean Thinking" managed to concentrate the fundamentals of thought 'lean' and the concept of waste ('muda'). They also managed to perfect the concepts of value stream, flow, pull, among others.

Currently, a company that does not consider the implementation of this system is not in a position to compete in the world, since it will be absent from aspects such as the quality of products and services, reduction of operating costs and the subsequent increase in sales. However, to find the right tool it is necessary to carry out a detailed analysis of the company's conditions.

It can be said that this system places a company as a world-class one, since it carries out procedures that guarantee productivity, efficiency and the quality of products and services. In addition, several previous works confirm the benefits of implementing this system.

In the study [4] many factories reported positive results with the implementation of lean manufacturing. Some of these benefits are improved quality, high inventory turnover, and productivity increases. All these benefits lead to greater customer satisfaction and loyalty, and higher profits, in addition [5] comments that one of the most important criteria of this system is to get rid of unnecessary issues in manufacturing that do not add value to the product.

We observe in [6] the current situation in the implementation of lean practices in manufacturing plants in India and its impact on operational performance. The study was conducted by applying a questionnaire to 79 plants in different regions from India. Lean manufacturing is a multidimensional construct, finding that 80% of the plants have implemented various dimensions of lean manufacturing; such as focus on the needs of the customer, pulled production systems, reduction of exchange time of molds (SMED), total productive maintenance (TPM), relationship with suppliers, statistical control of processes and inclusive problem solving.

It was also found that productivity, quality at first intention, reduced delivery time and inventories, as well as occupied space, in summary, respondents stated that quality at first intention, reduction of time delivery and increased productivity are the top three drivers of lean adoption in that context.

Finally [2] finds that the constructs of lean, sustainable manufacturing and continuous improvement have a direct, relevant, positive and statistically significant impact on the dependent construct.
