A Lean Primer

The main objective of Lean is to provide the best possible service to the customers through the elimination of all forms of waste. Waste can take the form of material or energy waste, inventory, defects or waste of capacity.
The elimination of waste requires a continuous improvement process in which workers are capable to quickly detect problems and are empowered to solve them effectively. It also requires a high stability of the production system achieved through production smoothing, that is, a manufacturing process focusing on a constant volume and product mix.

Specifically, the one of some manufacture had identified several techniques that helped the firm create one of the best run manufacturing processes in the world and achieve best quality and service at the lowest cost.
A strong emphasis is put on production smoothing, through constant volume and constant product mix. This is achieved using "takt time". Takt time is the frequency of consumer demand and the goal is to make sure this frequency is closed to the frequency of in which parts are produced in the system.

If the frequency of production is greater than the frequency of demand, then we start building inventory, i.e. waste. If the frequency of production is smaller than the frequency of demand, we have wait time, shortages and low service levels.
In order to implement constant volume and constant product mix, a strong focus is dedicated to the ability to implement quick changeovers and to reduce lot sizes (ability to make every piece every day).

In this context, empowering employees and team work becomes necessary. In fact, the low levels of WIP (Waste Inventory Planning) inventories (buffers) uncover problems as soon as they arise. Workers must have the ability to stop the production line, and to start production again, problems need to be fixed as soon as possible. This not only leads to detecting problems very quickly, but it also fosters problem solving capabilities.

In fact, the ability to stop the production line and the need to solve problems very quickly is part of the characteristics of lean manufacturing. In this manufacturing strategy, flexibility becomes extremely important, and it is achieved through workers' cross-training.

Guiding Principles

Lean techniques have been clearly driven by the requirements of assembly line manufacturing and tuned for the manufacture. Achieving similar results in different manufacturing environments requires the understanding of lean's four key principles :

• Take a holistic view
The production environment is a system that needs to be optimized as a whole. The objective is the close coordination of operations that are physically separated.

• Attention to details
Operational details are strategically important in lean manufacturing. The focus on setup reduction is a good example : instead of ignoring setups or taking them as a fixed constraint of the system, engineers try to reduce the setup time so that non-productive operations are minimized.

• Control WIP
Controlling WIP is an important objective that is achieved through the use of cards. The key idea is to change the manufacturing process from a "push based" manufacturing process to a "pull based" manufacturing process. Demand triggers production activities and gives the right frequency of production.

• Reduce cycle time
Reducing cycle time is a key objective in lean manufacturing and it is achieved by reducing setups, reducing delays, coordinating machine maintenance with production operations, and optimizing space in order to better utilize workers, equipments and workstation.