History of Lean Manufacturing

This article provides a brief history of “Lean Manufacturing” over several stages:

Fabrication and Manufacturing Prior to the “Toyota Production System”
The “Toyota Production System”
“Lean Manufacturing” After the “Toyota Production System”

Fabrication and Manufacturing Prior to the “Toyota Production System”

The history of “Lean Manufacturing” began with fabrication by a craftsman. At one time, our remote ancestors made flint weapons and tools by chipping rocks. The process required one person to have skill, strength and the right materials. Each stone implement was, presumably, hand crafted when it was needed. Design improvements may have taken centuries.

Throughout recorded history, individual artisans or small teams of craftsmen made more complex goods, generally by working on one product at a time.

Eli Whitney is credited with designing a manufacturing system that used interchangeable parts. If one craftsman were to make a musket, he could adjust the fittings to suit variations in the stock or barrel. Typical manufacturing required skilled engineers to finish assembling products by making the pieces fit together. In Whitney’s 1799 contract with the U.S. Army, the low price was possible because he planned to minimize these variations and eliminate the final adjustments.

The Lean Manufacturing concept is to eliminate the wasted effort for re-work and correcting errors by minimizing variance.

About a century later, Taylor and the Gilbreths applied scientific methods such as time studies, motion studies and worker motivation. Henry Ford’s assembly line organized the work by streaming inputs through processes.

The Lean Manufacturing concept is to eliminate wasted transportation of goods, and to minimize delays between consecutive value-adding processes.

Many argue that Ford’s assembly line did not support changes, such as producing a variety of models or even colours of automobile. After the Second World War, Japanese industries began to learn from American manufacturing gurus, particularly in areas of statistical quality control. Taichii Ohno led improvements that became known as the “Toyota Production System”. “Just in Time”, or JIT, was a key aspect of Toyota’s system.

The Lean Manufacturing concept is to eliminate excess inventory, and wasted movement of materials. Why move work-in-process from the factory to a warehouse, wait and then move a truck-load back to the factory, and finally move a pallet to the next assembly line?

The “Toyota Production System”

At Toyota, Quality Circles and other innovations led to greater respect for the factory workforce. Along with increased automation, this paved the way for cell-based manufacturing. Ohno tasked Shigeo Shingo to reduce the time needed for setup and changeover for assembly steps. A great weakness in any “Ford” factory was the time required to change from making one product to another. Ford therefore needed to maximize batch sizes, in order to minimize downtime. Toyota drastically reduced setup times so that multiple small batches made nearly as efficient use of the machinery as larger batches.

The Lean Manufacturing concept is to minimize batch sizes in order to avoid:

Excess production
Stocking of excess materials
Idle time for operators
Re-work (since defects are typically caught after a batch has been completed, a large batch means more finished goods to be fixed or scrapped).

Lean Manufacturing, under the name “Toyota Production System”, was developed from about 1949 through 1975. Toyota shared its knowledge with other companies, both Japanese and foreign.

“Lean Manufacturing” After the “Toyota Production System”

Over the following decades, several gurus made their mark by spreading this gospel. Norman Bodek was one of the first to publish Ohno and Shingo’s ideas in English. The use of the phrase “Lean Manufacturing” to describe the “Toyota Production System” has been credited to John Krafcik in a 1988 article or to James Womack’s 1990 book, “The Machine that Changed the World”.

A variety of other techniques have been absorbed into “Lean Manufacturing”. For example, the notion of “autonomation” is that machinery should detect errors so that people will respond to abnormal conditions. A machine that detects defects as soon as they occur can be essential in minimizing batch sizes, and especially in minimizing the amount of rework required.

Another recent trend is to combine “Lean Manufacturing” with “Six Sigma”, known as “Lean Six Sigma”.

Oskar Olofsson, 2009

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I am a Swedish-based Lean consultant, and the owner of the World-Class-Manufacturing.com web site.

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