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Practical guide · Lean manufacturing fundamentals

Lean manufacturing principles: the five, where they come from, and a worked example

Short answer

The five lean manufacturing principles are value, the value stream, flow, pull and perfection. James Womack and Daniel Jones set them out in the book Lean Thinking in 1996 as the order in which a company removes waste from the way it makes a product.

Start with value: what this customer will pay for in this product. Then follow the value stream, every step the product goes through, and mark the steps that add nothing. Make the steps that remain flow, one after another without queues. Let the customer pull, so nothing is made until the next step needs it. Then go round again, which is what perfection means here. The five are a sequence and you take them one product family at a time. They are not the same list as the 14 principles of The Toyota Way, which describe how Toyota manages, and they are not 5S, which is a method for organising a workplace.

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What are the five principles of lean manufacturing?

The five principles of lean manufacturing are specify value, identify the value stream, make value flow, let the customer pull and pursue perfection. Womack and Jones set them out in Lean Thinking in 1996, and the Lean Enterprise Institute calls them a five-step thought process. You take them in that order, one product family at a time.

The five lean principles, in order

  1. 1

    Value

  2. 2

    Value stream

  3. 3

    Flow

  4. 4

    Pull

  5. 5

    Perfection

Then back to value, for the same product family or the next one

The order matters: pull only works once the steps flow, and the fifth principle sends you back to the first.
  1. 1

    Specify value

    Define value from the standpoint of the end customer, for one product family at a time. Value is what that customer would pay for if they could watch the work.

  2. 2

    Identify the value stream

    List every step the product family goes through, from order to delivery, and remove the steps that create no value wherever you can.

  3. 3

    Make value flow

    Put the steps that remain in tight sequence so the product moves from one to the next without waiting in a queue.

  4. 4

    Let the customer pull

    Once the product flows, make only what the next step downstream asks for, when it asks for it.

  5. 5

    Pursue perfection

    Repeat the first four. Each pass exposes waste that the last one hid, so the work has no end point.

Two details get lost in the short list. The unit is the product family, not the plant, so a site with four families has four value streams. And pull comes after flow, because a pull signal sent into a process full of queues and breakdowns only starves the customer.

Where the five principles come from

The word lean came first. The Machine That Changed the World, published in 1990 by James Womack, Daniel Jones and Daniel Roos, reported five years of MIT-led research into how car makers build cars, and named what the researchers saw at Toyota lean production. It did not tell a manager in another industry what to do on Monday.

Lean Thinking, by Womack and Jones in 1996, was the answer. It boiled the practice down to the five steps above so that any company could follow them. The principles are therefore an outside reading of the Toyota Production System, written by researchers. Toyota does not describe its own system in these five words.

According to the Lean Enterprise Institute, Womack and Jones cut the five down in 2007 to three questions about purpose, process and people. The five are still the version most plants are taught.

What each principle looks like on the shop floor

A principle is only useful if you can tell, standing at the line, whether you are following it. The table gives one question to ask for each, what the answer looks like when the principle is missing, and the tool most plants pick up first.

The five principles as shop floor questions
PrincipleQuestion to askWhat you see when it is missingFirst tool
ValueWhat would the customer pay for in this step?Inspection, rework and paperwork that nobody outside the plant asked forA walk for the 8 wastes
Value streamWhat happens to the part between the dock doors?Nobody can say how long an order takes or where it waitsA value stream map
FlowDoes the part move on as soon as it is done?Pallets between every operation and batches sized to fill a shiftCells, small lots and takt time
PullWho told this station to make this part now?A schedule pushed to every station, plus expeditingKanban and a supermarket
PerfectionWhat did we change this week?A map on the wall from two years agoKaizen and a standard to hold the gain

The tools are where plants usually start, not the only way to follow a principle.

The guide to lean tools goes deeper on each. To score a plant first, use the lean principles assessment.

A worked example: one bracket family through all five

Illustrative numbers. A fabrication shop makes a family of steel brackets in five steps. The customer orders them weekly and complains about delivery. The team times one bracket through the plant and writes down the work at each step and the wait in front of it.

One bracket through the plant, today and after the changes
StepWork (minutes)Wait before it, today (hours)Wait before it, after (hours)
Cut2124
Bend382
Weld6160
Paint1242
Pack284
Total254812

Lead time today is 48 hours of waiting plus 25 minutes of work: 2,905 minutes. After, it is 12 hours plus 25 minutes: 745 minutes.

Hours a bracket waits in front of each step, before and after

  • Cut: 12 hours before, 4 after
  • Bend: 8 hours before, 2 after
  • Weld: 16 hours before, 0 after
  • Paint: 4 hours before, 2 after
  • Pack: 8 hours before, 4 after

Waiting in front of each step before and after: cut 12 to 4 hours, bend 8 to 2, weld 16 to 0, paint 4 to 2, pack 8 to 4.

Grey ticks are today: 12, 8, 16, 4 and 8 hours, 48 in all. After the changes the waits add up to 12. The work itself stays at 25 minutes.
  • Value: the customer pays for a cut, bent, welded, painted bracket that arrives in the week it was ordered. The 25 minutes of work is the value.
  • Value stream: the bracket spends 2,905 minutes in the plant and is worked on for 25 of them, which is 0.9% of the time. The rest is waiting.
  • Flow: bend and weld move next to each other, so a bent bracket goes straight to the welder and the 16 hour queue in front of weld disappears. Cut runs smaller lots.
  • Pull: paint and pack take from a small marked stock and cut replaces only what was taken. Waiting falls from 48 hours to 12.
  • Perfection: lead time is now 745 minutes, 74% shorter, and work is 3.4% of it. Nearly all the time is still waiting, so the team maps again.

Nobody worked faster: the 25 minutes of work is the same before and after. The gain came from taking out waiting. See what lead time is for the measures.

The five lean principles and the 14 principles of The Toyota Way

Search for lean principles and you will find lists of 5 and lists of 14. They come from different books and answer different questions. The five, from Lean Thinking, say how to improve a value stream. The 14, from Jeffrey Liker's The Toyota Way in 2004, describe how Toyota runs a company, and Liker groups them under four headings: long-term philosophy, the right process, developing people and partners, and solving root problems.

Where each of the five lands in Liker's 14
Lean principleClosest of the 14What the 14 add around it
ValueNone of its ownPrinciple 1 asks for decisions based on a long-term philosophy, even at short-term cost
Value streamNone of its ownPrinciple 12, go and see for yourself, is how Toyota expects you to learn the stream
FlowPrinciple 2, continuous flow to bring problems to the surfacePrinciples 4 to 8: level the workload, stop to fix problems, standardize tasks, use visual control and proven technology
PullPrinciple 3, pull systems to avoid overproductionPrinciple 11, on respecting and helping suppliers, extends pull beyond your own walls
PerfectionPrinciple 14, a learning organization through reflection and kaizenPrinciples 9, 10 and 13: leaders who know the work, developed teams, and slow decisions by consensus

The pairing is our reading. Liker does not map his list to Womack and Jones.

The 14 Toyota Way principles, and the three the lean five also name

Long-term philosophy

  • 1Decide for the long term

The right process

  • 2Continuous flowLean: Flow
  • 3Pull systemsLean: Pull
  • 4Level the workload
  • 5Stop to fix problems
  • 6Standardized tasks
  • 7Visual control
  • 8Proven technology

People and partners

  • 9Grow leaders
  • 10Develop people and teams
  • 11Help partners and suppliers

Solving root problems

  • 12Go and see
  • 13Decide slowly, act fast
  • 14Reflect and improveLean: Perfection

Liker's 14 principles in four groups: long-term philosophy (1), the right process (2 to 8), people and partners (9 to 11) and solving root problems (12 to 14). Principle 2 matches flow, principle 3 matches pull and principle 14 matches perfection.

Yellow marks where a lean principle has a direct counterpart. Value and the value stream have none. The other 11 are what the 14 add.

Read down the right-hand column and the difference is plain. Most of the 14 sit outside the process heading, on leaders, teams, suppliers, decisions and learning, and the five say almost nothing on those. A plant that follows the five, cuts its lead time and drifts back has often changed the process and not the management.

Toyota's own 2001 Toyota Way has two pillars, continuous improvement and respect for people. Liker's 14 are his account of how they show up in practice.

The 14 principles of The Toyota Way, in order

Paraphrased from Liker's book, under his four headings.

  1. 1

    Long-term philosophy

    Decide for the long term, even when it costs money now.

  2. 2

    The right process

    Create continuous flow so problems show up.

  3. 3

    The right process

    Use pull to avoid overproduction.

  4. 4

    The right process

    Level the workload (heijunka).

  5. 5

    The right process

    Stop to fix problems and get quality right first time.

  6. 6

    The right process

    Standardize tasks as the base for improvement.

  7. 7

    The right process

    Use visual control so nothing hides.

  8. 8

    The right process

    Use only reliable, tested technology that serves people.

  9. 9

    People and partners

    Grow leaders who know the work and teach it.

  10. 10

    People and partners

    Develop exceptional people and teams.

  11. 11

    People and partners

    Respect suppliers by challenging and helping them.

  12. 12

    Solving root problems

    Go and see for yourself (genchi genbutsu).

  13. 13

    Solving root problems

    Decide slowly by consensus, then act fast.

  14. 14

    Solving root problems

    Learn through reflection and kaizen.

Which principle should you work on first?

Match the symptom you see to the principle behind it.

Which principle to work on first

  • What you see

    Customers complain and nobody agrees what good is

    Work on

    Value

    Write what one customer values as a number

  • What you see

    Nobody can say how long an order takes

    Work on

    Value stream

    Time one part from dock to dock

  • What you see

    Parts sit in queues between steps

    Work on

    Flow

    Move two steps together, shrink the lot

  • What you see

    Stock builds in front of some steps while others starve

    Work on

    Pull

    Add a small marked stock and replace only what is used

  • What you see

    Gains fade after a few months

    Work on

    Perfection

    Set a date for the next map and name an owner

Read the left card as what you see on the floor. The yellow card is the principle behind it and the first move.

How to apply the five principles in a plant

  1. 1

    Pick one product family

    Choose one with a real customer complaint and enough volume to see a change inside a few weeks. Leave the rest of the plant alone.

  2. 2

    Ask the customer what they value

    Delivery in the week ordered, a defect rate, a lot size. Write it as a number someone can check.

  3. 3

    Walk the stream and time it

    Follow one part from receiving to shipping. Record the work and the wait at every step, as in the example. The value stream plan holds the result.

  4. 4

    Fix flow where the wait is longest

    Take the biggest queue first. Move the two steps together, cut the lot size, or shorten the changeover that forces the batch.

  5. 5

    Add pull where flow has to stop

    Where steps cannot sit side by side, put a small marked stock between them and replace only what is used.

  6. 6

    Measure, then go round again

    Compare lead time with the customer's number, write the new standard down and map the family again.

One line or cell run this way is a model area: a place where the five can be seen working first.

Common mistakes with the lean principles

  • Starting with tools. A plant runs 5S and kanban everywhere without having asked what the customer values, and tidies steps that should not exist.
  • Defining value from inside. Value is set by the customer of that product family, not by what the plant is proud of or what the cost system rewards.
  • Pull before flow. Kanban cards on a process with long changeovers and unreliable machines produce shortages, and the cards get the blame.
  • Mixing the lists up. The five principles, the 14 of The Toyota Way, 5S and the 8 wastes are four different things.

Go deeper

This page is the short version. These guides cover each part in full.

All our articles on this subject are in the lean manufacturing fundamentals topic.

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FAQ

Questions about lean manufacturing principles

  1. Specify value from the customer's point of view, identify the value stream for each product family, make the value-creating steps flow, let the customer pull, and pursue perfection by repeating the cycle. They are taken in that order, one product family at a time.

  2. James Womack and Daniel Jones, in the book Lean Thinking, first published in 1996. They based the five on their study of Toyota, which they and Daniel Roos had reported in The Machine That Changed the World in 1990.

  3. The five come from Lean Thinking and describe how to improve a value stream: value, value stream, flow, pull, perfection. The 14 come from Jeffrey Liker's The Toyota Way and describe how Toyota manages, including long-term philosophy, leaders, people, suppliers and decision making. Flow and pull appear in both lists.

  4. Lean production is the name the MIT researchers behind The Machine That Changed the World gave in 1990 to what they saw at Toyota. The Lean Enterprise Institute describes the practice as a way of delivering what the customer values with less waste. It is Toyota's system described for other companies.

  5. Kaizen is the Japanese word for continuous improvement. In lean it means small changes made by the people who do the work, checked, and then written into the standard. It is the fifth principle, perfection, in daily practice, and the third foundation of the TPS house.

  6. Continuous improvement is the habit of making the work a little better every day instead of waiting for a large project. Each change is tried, checked against the result and, if it works, becomes the new standard. In the five principles it is perfection: go round again.

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