Lean Manufacturing: eliminating waste and producing according to value

In one line

Lean Manufacturing is a production philosophy that seeks to eliminate everything that does not add value for the customer, involving everyone in the plant in that task.

What it is

According to the Icesi University paper, the term Lean Manufacturing was coined in the book The Machine That Changed the World (Womack and others, 1990), which compiled the best practices of the global automotive industry and highlighted those of Toyota. It clarifies that concern for reducing waste did not begin at Toyota: Henry Ford was one of the first to pursue that goal. Lean is, in essence, a relentless pursuit of waste, one that challenges many prejudices inherited from mass production.

Meyers and Stephens add the vocabulary: "lean thinking" comes from the Toyota production system and from Womack and Jones's book Lean Thinking, and lean manufacturing is the concept whereby all production personnel work together to eliminate waste. Its philosophy is that of added value: cost elements that do not add value to the final product are eliminated. And they put forward a concrete design idea: a fundamental principle is the product-oriented layout, with less work in process, quality problems that are easier to see and less floor space.

How it is applied: the techniques and their order

The Icesi University paper proposes an implementation model with continuous improvement (kaizen) at the center and the techniques ordered according to what they contribute:

Technique	What it contributes
Value stream map (VSM)	See the complete process, from order to delivery, and separate what adds value from what does not
5S	Order and cleanliness as a discipline
Flexible work systems	Manufacturing cells with operators who know the whole cell
Standard work	Document the best practice to sustain improvements and to train people
SMED	Drastically reduce changeovers
TPM	Turn the "lost time" spent on maintenance into productive time
Just in time (with kanban)	Produce and move the right quantity at the right moment
Jidoka	Prevent errors in the process, with inspection at the source
Heijunka	Leveled production, with the product mix replicated in the smallest possible interval

Each one has its own article on this site: VSM, 5S, SMED, TPM, just in time, kanban and jidoka. And the shared goal is the list of wastes.

Real example

The University of Azuay thesis on the LACPRIMA dairy plant is a good example of how the technique is chosen according to the problem. It walked through five areas (raw material reception, pasteurization, molding, packaging and coding, and storage) and assigned tools: 5S for the disorder and items out of place, andon for raw material quality control and the lack of signage, poka-yoke for the product waste when filling the molds, a spaghetti diagram for the molds stored in two places and value stream mapping for the unrecorded times. The conclusion of the diagnosis is that the main problems were the lack of records and procedures, which produced a significant amount of unrecoverable waste of raw materials.

Meyers and Stephens, for their part, tell the case of a golf equipment manufacturer that had six months of work-in-process inventory with a process-oriented layout: by switching to a product-oriented one, it cut that to less than two days.

Benefits

• Less inventory, less space and shorter lead times.
• Quality problems are more visible because there is less material piled up between workstations.
• It involves the people who know the process best.

Limitations to keep in mind

• The techniques should not be applied haphazardly: each one contributes a different lesson, as the Icesi University paper warns.
• Reducing inventory exposes the problems that inventory was hiding, and that is uncomfortable before things get better.
• It is a philosophy, and as such it requires cultural change: without people's participation, it ends up as a bunch of posters.

In summary

Lean is looking at the process with the question "does this add value for the customer?" and eliminating what does not. Its techniques (VSM, 5S, SMED, TPM, JIT, jidoka, heijunka) are not a menu: they are chosen and ordered according to the waste you want to attack. Combined with the variation reduction of Six Sigma, it gives you Lean Six Sigma.