Lean Manufacturing Principles Introduction

The history of Manufacturing can be summarized in three evolutions: First, Handcraft, where products are made to customer requirements. It is a single piece manufacturing which means each product is unique and each quality varies from one product to the other. The inventory is very low and the product itself is expensive in which only the rich can afford. The second step toward manufacturing is called “Mass Production” wherein assembly lines are set-up, and the labors are divided among workers as done by Henry Ford in 1914. Standards are set to meet local and international customers. Thus each product has the same quality with each other. And the last evolution of manufacturing is called the “Lean Manufacturing”.

The Lean Manufacturing Idea has been develop in Japan, and the name is given in the US. Lean is the manufacturing system of the Japanese automotive industry. It needs less production factors than the traditional mass manufacturing. With other words, less than half of the development time and less than the half of inventories capacities are sufficient for the production. At the same time more product variety with higher quality levels can be offered.

The success of the Lean Manufacturing idea is founded on the involvement of the employees with teamwork. Employees of all areas of the company can be integrated in teams, e.g. design, research, engineering, accounting, sales etc. Depending on the project, the scope can be planning process, accounting, manufacturing or sales process. Every employee takes over responsibility for his task. Employee motivation and identification increases while the defect rate is decreasing.

The philosophy of lean manufacturing of a production system is based on 5 Principles: Define values in the eyes of the customer. Identify the value stream and eliminate waste. Make flow at the pull of the customer. Involve and empower the employees. Continuous improvement in pursuit of perfection.

In the evolution of the Lean Manufacturing, there are several terms used:

1. Batch production. After every process step, the product will be stored and not transferred to the next step until certain quantities have been manufactured.
2. Single piece flow (one piece flow). A product will be consistency transferred piece by piece, from one step to the next.
3. Just in time. Simple means at the right time, the right quantity, the right product, material or information at the right location.
4. KanBan (Card signal). It is a method to control the material flow in the manufacturing area. The needed stocks are close to the manufacturing. And the number of stocks will continuously adjust regarding the changing needs. Not too much or not too less.
5. Takt Time. The calculated time frame which is needed to process a product or information in order to fulfill the customer requirements. Takt time is calculated as the available hours over the customer demand.
6. Cycle time. The time which is needed to perform a work step or process.
7. Push-pull methodology. A push is where manufacturing is pushing the finished product to the customer while Pull is where the customer is pulling the product from the manufacturer. In Lean manufacturing, the pull system is used.
8. Visual controls. A technique for a simple control of the production processes and tools to identify fast process deviation  such as andon signals, Kanban signals, floor markings, information and metric boards, and work instructions.
9. 5S. A systematic method in five steps to organize the work place.(Seiri = Sorting, put not needed material away. Seiton= Storage, a defined place for everything.  Seiso = Shinning, dispose dirt, waste, oil and others. Seketsu = Stadardizing, all rooms and places are equal. Shitsuke = Sustaining, regular reviews, control plans and others.
10. Standard Work. A standardized work process which includes the following elements; work steps, safety, visual display, timing and takt time. It is a tool for manufacturing of quality products, a basis for continues process improvements a documentation of a standard for a work process.
11. Kaizen (Kai=change; Zen=good). A method for process optimization. A series of one after the other following activities for improvements in a pre-defined area. This kind of activities can be performed in a time limited work shop (e.g. 5 days) over a longer time in several steps.
12. Poka Yoke. A method to design processes in that way that the occurrence of defects are not possible anymore. This applies to production as well as administration. The equipment can be designed in a way that no defect parts will be accepted in the process. Another good example is that form sheets for creditors and debtors have different colors.
13. Monument. Under monument, we understand large and not moveable equipments or work processes. The organization and or technical effort for a simplification or change would not be acceptable.
14. Spaghetti Chart. Displays the material and information flow between building and areas on the site.

Overall, production and manufacturing processes in accordance to lean principles are an industrial revolution, which are not limited to the automotive production or to Japan. The consequences should be similar like the change in spring 1914. At that time in Detroit, Henry Ford replaced the hand craft production by an assembly line. Within some month the time effort for the assembly of major parts of a car were reduced from 750 to 90 minutes.