Introduction to lean manufacturing

Introduction to Lean Manufacturing

Background and Basic Concepts
Lean manufacturing is a concept that originated in Japan as the Toyota Production System (TPS) in the years after World War II. It has since evolved to an integrated methodology for increasing the efficiency and flow of a production system by applying a number of tools that help identify and reduce waste. As waste iseliminated, flow and quality improve while production time and cost are reduced. Because of the benefits achieved in the automotive sector, lean concepts have been used in other manufacturing areas as well as adapted to the construction and healthcare industries among others (Askin, 2002).

In a broad sense, lean manufacturing is a continuation of the concepts of work efficiency proposed by Henry Fordand Frederick W. Taylor, the father of scientific management. Taylor’s advances in time and motion study and standardization are often cited as sources of inspiration for Shingeo Shingo and Taiichi Ohno, the creators of the TPS (Womack et al, 1990). Because of its origins in the Far East, much of the terminology used in lean manufacturing is based on Japanese words.

Sources and Types of WasteThe TPS identified 3 sources of waste that can be found in a system, with the following Japanese words: Muda or non-value adding activity; Mura or inconsistency; and Muri or overburden (Womack et al, 1990). Most lean efforts focus heavily on elimination of Muda but a sound lean approach will balance the need to tackle all three sources of waste in an organized way.

Muda is defined as anyactivity that is wasteful and does not add value in the system thus, Muda exists when more resources are consumed than are needed to produce the goods or provide the service that the customer is willing to pay for. Further classification has identified at least 7 types of Muda: transportation (moving of products that is not necessary for processing); inventory (work-in-process and finished product notbeing processed); motion (people or equipment moving or walking more than necessary); waiting (for the next production step); overproduction (ahead of demand); over processing (due to poor tool or product design); defects (that would require extra steps for inspection and correction). This represents the basic list but other types of Muda can be identified in different systems which can often beuseful when implementing lean concepts.

Mura describes the unevenness or lack of consistency that is present in a system. The variation of a process makes it unpredictable and can lead to defects and a great deal of error which in turn, can lead to inefficiencies. For this reason the sources of variation need to be identified and minimized.

Muri is defined as unnecessary work imposed bymanagement on workers and machines because of poor organization. Muri is in many cases a consequence of traditional corporate cultures and poor system design. Variation and accidents are more common when a person (or machine) is overexerted.

Principles and Tools of Lean Manufacturing
Womack et al (1990) identified 5 basic principles for implementing Lean thinking. The following list explainsthese principles and provides some tools that can be used to accomplish them:

1. Define the value of the product (or service) based on the customer requirements so that the true value can be separated from Muda (waste). This sometimes involves challenging established definitions of value or quality such as low price, variety, and fast delivery.
2. Identify the value stream of the system. Oncethe value of a product (or service) has been established, the different steps followed need to be mapped out using Value Stream Mapping (VSM). This tool will categorize the actions taken into: (a) steps that create value; (b) steps that create no value but are an intrinsic part of the system and cannot be eliminated just yet; (c) steps that create no value (backtracking, scrap, etc) and can be...