Lean Principles Explained: Value, Flow, Pull, Perfection

Disclosure: M365.FM host Mirko Peters works at iFAKT GmbH. This page describes the company factually; paid partnerships and links are labelled as advertising.

By Mirko Peters · 2026-11-11

The five lean principles are value, value stream, flow, pull and perfection. See what each means on the shop floor and how to apply them in the right order.

The five lean principles are define value, map the value stream, create flow, establish pull and pursue perfection. Each principle of lean helps a plant decide what to improve and in which order. This article is for plant managers who know the tools of lean but want to understand the logic behind them. It explains each principle with a shop floor view, a worked example of flow with numbers and the mistakes that make plants apply the principles out of order.

Key points

• The five lean principles are: define value, map the value stream, create flow, establish pull and pursue perfection.
• Value is defined by the customer, by product family. A step that the customer would not pay for is a candidate for removal.
• Flow means moving one item, or a small consistent batch, through the steps without stopping. Use pull where flow is broken.
• The principles work as a cycle. Each round of improvement exposes the next problem, which is why perfection is a direction.
• Apply the principles in order on one product family before you spread them to the rest of the plant.

What are the five lean principles?

The Lean Enterprise Institute describes lean thinking and practice as a five-step thought process proposed by Womack and Jones in 1996 to guide managers through a lean transformation. The five steps are:

1. Value. Define value from the end customer's view, by product family.
2. Value stream. Map every step in each product family's value stream and remove steps that add no value.
3. Flow. Arrange the value-creating steps in close sequence so the product moves smoothly.
4. Pull. Let customers pull value from the next upstream activity.
5. Perfection. Repeat the process until value is created with no waste.

These principles of lean manufacturing connect to the Toyota Production System, whose goal Toyota describes as thoroughly eliminating waste and shortening lead times. In a lean management system, they also give leaders a common language: what does the customer value, where does the product wait, does it flow, and what do we improve next? To eliminate waste and apply lean principles with discipline, take them in sequence.

The order matters. Plants that start with pull or kanban before they know what the customer values often build a neat system around the wrong steps. The same page offers a shorter version of the idea from 2007: purpose, process and people. Purpose asks what problem the customer wants solved. Process is the steps. People are the owners and teams who run and improve them.

How do you define value?

Value starts outside the plant. A step has value if the customer would pay for it, and if it changes the product in a way the customer wants. Machining a part has value. Moving the part to another hall does not, even if it is needed today.

Define value for one product family at a time, because different products pass through different steps. For each family, write down:

• Who is the customer, internal or external?
• What do they need: quality, delivery time, price, flexibility?
• Which steps change the product, and which only wait, move or check it?

This sounds simple. In practice, plants often discover that their idea of value is based on what the machines can do, not on what the customer asked for. A short customer conversation is cheaper than a long improvement project in the wrong direction. Value can sit in a product or service, and customer satisfaction is the test of it.

How do you map the value stream?

The value stream is all the steps that a product family goes through, from raw material to delivery, with the information that controls them. Mapping it means drawing the steps with their times, the queues between them and the stock that sits in between.

A value stream map usually shows three things that no single department sees:

• Where the product waits. The map shows how long the product sits in queues compared with the time it is worked on.
• How information flows. Who tells each step what to make, and when?
• Which steps add value. The map separates them from the rest, which you can then reduce or remove.

Draw the current state first, walking the process yourself and writing down real times, not times from the system. Then draw a future state with the biggest waits removed, and agree on the first steps to reach it. Mapping the value stream also helps you reduce waste and improve processes across the whole workflow. Keep it to one product family and one sheet of paper.

How do you create flow and pull?

Flow comes first, and it is the core principle that ties the others together. The Lean Enterprise Institute defines continuous flow as producing and moving one item at a time, or a small and consistent batch of items, through processing steps as continuously as possible, where each step makes only what the next step requests. It also notes that this can be achieved in different ways, from moving assembly lines to manual cells. The Shingo Institute adds that flow is created by removing waste, unevenness and overburden.

In practice, flow means shorter distances between steps, smaller batches, balanced work content and fewer stops. Steps that belong together sit together, ideally in a cell.

Flow is not always possible. Some steps have to run in large batches, or machines stand far apart. For these cases, the Shingo Institute offers a rule of thumb: flow where you can, pull where you can't. It describes pull as a production control system in which upstream work starts only when a downstream operation signals a need, using a kanban.

So a pull system is the link between steps that cannot flow. It limits the stock between them and tells each step what to make next. It avoids building parts that nobody has asked for yet.

How do you pursue perfection?

The fifth principle is not a final step. The Lean Enterprise Institute says to repeat the process until a state of perfection is reached, in which value is created with no waste. You will never get there fully. That is the point: each round exposes the next problem.

In practice, perfection becomes a routine of continuous improvement. The same source calls for frequent improvement cycles for each process, and for standard work, so that each improvement is held and becomes the base for the next. Use a simple rhythm: pick a problem, find the cause, test a change, measure the result and update the standard.

Do not wait for the perfect map or the perfect plan. Start with the biggest waste you can see and make it visible every day.

Example: batches versus one-piece flow

This is an illustration with made-up numbers.

A product passes through three steps in sequence: cut, drill and deburr. Each step takes 1 minute per part. A batch has 100 parts. We ignore setup time and transport to keep the numbers clear.

Batch and queue. Each step processes all 100 parts before the next step starts.

• Cut: 100 minutes.
• Drill: another 100 minutes.
• Deburr: another 100 minutes.
• All 100 parts are complete after 3 × 100 = 300 minutes. The first part comes out at minute 201, because deburring starts only after drilling the entire batch.

One-piece flow. Each part moves to the next step as soon as it is ready.

• The first part comes out after 3 minutes.
• Each next part follows one minute later.
• All 100 parts are complete after 3 + 99 = 102 minutes.

The work content is identical, but the batch is done after 102 minutes instead of 300, and the first part is available after 3 minutes instead of 201. There is a second effect. If the drill is set wrongly, batch and queue finds the defect only when the first parts reach deburring, so up to 100 parts are affected. In flow, the next step sees the defect after one part. Real plants have setups, transport and uneven times, so the gain will differ. The point stays the same: flow shortens lead time and exposes problems early.

Common mistakes

• Applying lean as a tool kit. Starting with kanban or 5S without defining value gives you tools without a direction.
• Defining value from the inside. If the machines or the departments define value, not the customer, you optimize the wrong steps.
• Mapping and stopping. A value stream map that is not followed by action is a poster.
• Forcing flow where it cannot work. Use pull between steps that must run in batches or sit far apart.
• Treating perfection as a project. If the improvement stops when the project ends, the process drifts back.
• Leaving out the people. The owner of the value stream and the teams on the floor must take part in all five steps.

How software can help

A pen and paper are enough for the first map. As soon as you have many products, steps and data sources, software helps to keep the map current and shared. iFAKT's Polaris VSM provides data-based value stream mapping that models material and information flows collaboratively and makes waste and bottlenecks visible. Whatever tool you use, check the map against what you see on the floor, and use it to choose the next improvement.

Next step

Choose one product family, write down what its customer values and draw its current value stream on one sheet of paper. Then use the lean principles in order: remove the biggest wait, create flow where you can and use pull where you cannot.