Lean

In the TPS Principles and Practice group on LinkedIn, Aineth Torres Ruiz asked about what mass production is and is not. With the loose talk of “Henry Ford’s Lean vision” going around, the confusion is understandable. In fact, the term “mass production” was coined specifically to describe Ford’s production system in an Encyclopedia Britannica article in 1926, and defined as follows:

“Mass production is the focusing upon a manufacturing project of the principles of power, accuracy, economy, system, continuity and speed.”

The article insists that “Mass production is not merely quantity production, for this may be had with none of the requisites of mass production. Nor is it merely machine production, which may exist without any resemblance to mass production.”

The encyclopedia article does not imply that the system was inflexible, but Ford’s system of that era was designed to build Model Ts and nothing else. Even though the following picture is from 1937, a decade after the end of the Model T era, the dense packing of presses makes you wonder how you were supposed to change dies:

Modern automotive press shops have machines arranged in lines, with space on the side for dies. In this shop, a die change had to be a rare event.

In essence, the term “mass production” is to Ford as “lean manufacturing” is to Toyota, a generic term applied to give broader appeal and generalize an approach developed in a specific company. It is not a derogatory term, and many elements of mass production found their way into TPS, along with parts of the “Taktsystem” from the German aircraft industry of the 1930s. To these external inputs, the Toyota people have been adding their own twists since the 1930s.

Ford’s system itself evolved as it was adopted by competitors. As Peter Winton pointed out in the LinkedIn discussion, the original mass production was the production of large quantities of the same thing. As early as the 1920s, all the high-speed machines and lines dedicated to making the aging Model T at the River Rouge plant were both the strength and the Achilles heel of the system, giving GM the opportunity to grab market share away from Ford by, as Alfred P. Sloan put it “introducing the laws of Paris dressmakers in the car industry.” Ford alumnus William Knudsen’s “Flexible Mass Production” at Chevrolet made it possible through yearly model changes that could be completed in a few weeks. When Ford finally had to change from the Model T to the Model A in 1927, it required a thorough retooling of the Rouge plant, which took 9 months.

Ford’s system itself changed over the decades, and, at least as Lee Iacocca described its practices,  the financially minded leadership that emerged in the 1950s no longer focussed on improving production. In my review of Deming’s Point 5 of 14 on that topic, I had included the following pictures of the same operation performed the same way 30 years later:

In the 1988 paper in which he introduced the term “Lean production,” John Krafcik makes a distinction between “Pure Fordism” and “Recent Fordism,” the main difference being that “Recent Fordism” involves large inventories, buffers, and repair areas. This, of course, implies nothing about what the Ford people have done since 1988.

The concept of a dedicated production line — effective at making one product and incapable of making anything else — is in fact not obsolete. If you have a product with long-term, stable demand, it is a better solution than a flexible line whose flexibility you don’t need. This is why you do a runner/repeater/stranger analysis of the demand for your products, and then investigate trends and seasonal variations. In the Lean approach, you use a dedicated where it fits and other approaches where it doesn’t; most plants, instead, have a one-size-fits-all approach.