Method

Five Lean principles

In French: Les cinq principes du Lean

The five Lean principles form the framework of a transformation: they say where to take hold of it and in what order to proceed, each step making the next one achievable.

The five, in their order

Define value. It is stated from the customer, for a given product or service. This first principle is the one most often rushed, even though it conditions the other four: a perfectly smooth flow that delivers what nobody wants remains complete waste.

Identify the value stream. All the activities that contribute to that value are described, end to end, including those that belong to other departments or to partners. It is the principle that forces one to look beyond one’s own scope.

Establish flow. Work is made to run without stopping or going back, which means treating the causes that interrupt it rather than working around them with stocks.

Pull. Nothing is produced until downstream has consumed. The pace stops being set by a forecast and becomes that of real demand.

Aim for perfection. The cycle starts again, each improvement revealing the next obstacle. It is less an achievable objective than a way of saying there is no final state.

Why the order is not decorative

Each principle makes the next one achievable. One cannot describe a value stream without having said which value is meant; one cannot pull a flow that keeps getting interrupted. Taking the principles out of order produces projects that fail for reasons later blamed on Lean itself.

The most common mistake is to start with the fourth — installing pull flow on an unstable process. The system then immediately reveals every irregularity, the workshop blocks, and the conclusion is that the method does not suit this activity.

The progression therefore requires patience on the first two principles, which produce no visible result and yet take up a large share of the time of a first project.

What they do not say

They do not constitute a problem-solving method: they order an approach, without saying how to analyse a cause or how to prove an effect. That is why they coexist with a structured approach rather than replacing it.

Nor do they say anything about people, whereas that is where most transformations fail. Respect for the teams and the development of their skills do not figure among the five, and they have to be sought elsewhere in the Lean body of knowledge.

They remain silent, finally, on variability, which is the territory of Six Sigma. A flow can be perfectly organised and produce scattered results — the two approaches complement each other precisely because they do not look at the same thing.

The common mistakes

Reciting them as general culture without applying them to a precise scope. The five principles make sense only in relation to a named product or service, with its customer.

Skipping the definition of value because it seems obvious. It is the step where one discovers that two departments in the same process do not serve the same customer, and that discovery generally changes the project.

Taking "aim for perfection" as an injunction to exhaustiveness. The principle describes a cycle that starts again, not a project that never ends.

On the shop floor — Software publishing

A team had installed pull flow on its customer requests, with limits per column, without having described the complete chain. The blockages came from a legal approval located outside its scope and invisible on its board. The system worked perfectly on the two thirds of the journey it covered, and the total lead time had not moved.

The other tools illustrated by this trade: services, it and engineering.

Frequently asked questions

Do the five principles have to be followed in order?

Yes for a first deployment, because each makes the next possible. On the other hand, an organisation that is already advanced goes through them in a loop rather than in a line: it regularly returns to the definition of value, which evolves with customer expectations, and re-describes its chain when it has changed.

Do these principles apply to services?

Entirely, provided the vocabulary is translated: the value stream there is a file’s journey, the flow is interrupted by approvals rather than by breakdowns, and stock is called a queue. The gains there are often greater than in production, because those interruptions are measured by nobody.

What is the difference between the five principles and DMAIC?

The five principles order an overall transformation and say where to take hold of it; DMAIC structures the resolution of a precise problem, with its milestones and its proofs. Several DMAIC projects can be run within an approach guided by the five principles — they operate at two different scales and are not substitutes for each other.

Where should one start, concretely?

With a restricted scope and an identifiable customer: a product family, a type of file. Describing its value stream end to end takes a few days and almost always produces two or three obvious findings nobody had seen, for never having looked at the whole journey rather than one’s own step.