The Goal of Lean Manufacturing: Flow

005 – The Goal of Lean Manufacturing: Flow

The Goal of Lean Manufacturing: Flow



In this episode I’m going to explain one of the goal of lean manufacturing, which is something we call “flow.” Historically, this has also been called “Just In Time” manufacturing, but we’ll treat these as synonyms.

As always, I will be naming resources and making references throughout the cast, but you can always check out the show notes online for easy access to them. Just go to to find this episode’s notes.

This episode is somewhat of a continuation of episode two titled, “The Heart of Lean Manufacturing: Eliminating Waste.” Indeed, eliminating waste is at the heart of lean. But the natural outcome of eliminating this waste from a system is flow. So the creation of flow is a kind of corollary to the elimination of waste. It’s what we’re after: creating flow! So in this episode I’m going to give you a broad overview of flow and what it is.

Defining Flow Conceptually

When I say the word flow you may imagine a picture of the flow of traffic, or flowing water in a stream, or something of that sort. These are all good pictures of the concept of flow. When you’re driving to work, flow is bothenjoyable and productive. It takes you places. But when there are traffic jams, red lights, or construction projects on the road, your commute to work is maddening and unproductive. If you picture a water system of streams and lakes, there are streams and rivers where the water is moving steadily and fast, and there are lakes or even dams where the water pools up and comes to almost a complete stop. A third example I’ll give you is taking a visit to the dentist or doctor. Everyone likes a productive visit–meaning, a visit that keeps you moving and flowing through the medical system. No one likes to be stuck in a large queue of patients in a waiting room or waiting endlessly between nurse and physician visits. We like flow. We like it when there are no lines at the grocery store, when we can walk straight through TSA security at the airport, and when life is eventful, productive, and moving along.

Applying the Concept of Flow to Work and Manufacturing

Now as we continue, I want you to apply this imagery to your workplace. The concept of flowing work is the same.

For example, if you step onto the production floor right now you could probably look around you and find lots of inventory and product waiting to be processed. It may be in bins and buckets or on pallets and in racks. I daresay that I’ve been to some production floors and was not sure if I had stepped into a game of Minecraft where operators were building pyramids of inventory instead of manufacturing product. On a similar note, I’ve heard that Taiichi Ohno and Japanese sensei would often visit manufacturing floors and question associates, “If this is a manufacturing floor, why am I seeing a warehouse?” What he, you, and I are all looking at is inventory that has pooled up just like water in a lake. There’s no flow.

And this is true in the office and service organizations too. Consider your inbox. You may not have good flow going on. Or your desk. Or the stack of paperwork that has been waiting in queue for hours or days to be processed. It’s all the same.

Four Reasons Why Bad Flow is Bad

Now there are a lot of reasons why bad flow is bad. What I’m really talking about are the many consequences of mass or over production.

  • There are long lead times. This means customers are made to wait and scheduling and managing production is a nightmare.
  • The quality feedback loop is long between operators or departments. This means you may not find out that stamping made a mistake until two days and 5,000 parts later.
  • Big lakes of inventory require lots of shelves, floor space, forktrucks, walking, handling, counting, and managing.
  • Even though there’s so much product on the shelf, these systems are often plagued by shortages and backorders.

I didn’t say it, but as you can imagine, bad flow is expensive. It costs a ton of money and is very fatiguing.

Flow is often a consequence of batch size. The bigger the batch size, the worse the flow. But as you reduce batch size the flow rapidly increases. The concept of Just In Time manufacturing is basically to deliver just what is needed and just in time–no more, and no less. I’ve got a few videos to illustrate this point that you’ll want to see if you haven’t seen them already on YouTube or at Lean Smarts. Check out the show notes at to see them.

An Example in a PB&J Sandwich

But in essence, if I were making a PB&J sandwich and did it in a batch size of 1000, it could take me a long time before I finish my first sandwich. First I’d grab 2000 slices of bread and lay them out. Unfortunately there’s not enough counter space in my kitchen to do that, so I may have to borrow some floorspace in the dining room or my neighbor’s kitchen next door. In any case, then I’d put peanut butter on 1000 of the slices. Then I’d put jam on the other 1000 slices. Finally I’d put the two halves together and finish my 1000 sandwiches. If I started at daybreak it may not be until dinner that I’m ready to eat my first sandwich! That’s bad flow.

If instead I did one sandwich at a time, I could deliver my first finished sandwich in a matter of minutes. It requires very little space. It’s very fast. And I can get immediate customer feedback. If I got the order wrong or there was mold on the bread, for example, I’d discover in minutes that there is a problem vs. half a day when making a batch of 1000.

And so flow is superior.

As you eliminate waste in a process, what happens is the value begins to flow more and more and more. It’s like breaking down the dams in the river and removing the boulders from the streams. The value-added actions that create products are unhindered by waste and flow freely.

Pursuing Perfection

The ideal state we’re trying to get to–which is sometimes synonymous with lean folk talking about “true north– is perfection. Perfect flow means no waste, no inventory, no defects, no waiting of any kind. It’s the creation of value at the speed of customer thought. Perfect flow is as if one of your customers thought, “I want an Apple Watch” and *poof* it appears on their hand. That would be magical!

What flow does is provide immediacy for the customer–whether that’s the next department or an end-user. Flow allows for you to deliver what the customer wants as immediately as possible. This is also attractive for cash flow if you’re familiar with accounting.

A Few Sidenotes…

Okay, a few sidenotes here before wrapping up this episode.

First, flow doesn’t mean to just do everything you’re doing faster. Lean thinkers are hard workers, but we don’t just work hard: we work smart (and that’s what lean is all about)! Flow is created when you solve operational problems and eliminate waste. Take the waste out, and value will flow. When you’ve got flow, your work is often easier and not harder. It’s smooth. You’re not searching for lost tools or material or wasting time walking, waiting, or handling parts.

Secondly, flow still holds true even if you have large equipment with lengthy changeover requirements. The smaller the batch size, the better the rest of the system will perform. And also, there are methods out there to reduce changeover times. Check out SMED if you’re unfamiliar with it. I’m also adding a link to the show notes for some amazing work at Denso to create “lot size one” in an aluminum casting operation. Most people would assume, “Casting is a batch process; flow isn’t possible.” But actually, Denso is doing it.

Thirdly, it’s good to train yourself to recognize flow on all levels: both big and small. The flow of an individual operator’s work is relevant to this discussion. One piece flow is ideal and any kind of delays in the process affect the flow of work. But also learn to recognize flow on a bigger scale such as between departments, inventory handling, and your supply chain. There are both large streams of flow and micro currents within your organization.

And lastly, a simple way to learn to see impediments to flow is to constantly ask the question, “Why is this waiting?” You can ask this question about everything:

  • “Why is this decision waiting to be made?”
  • “Why is that operator waiting for something to do?”
  • “Why is that widget waiting to be processed?”
  • “Why are those files waiting to be processed?”
  • “Why is that patient being made to wait?”
  • “Why am I waiting on my children to get out the door?”

I mean it: you can ask this question about everything and begin to tap into the concept of flow.

References & Resources