Tips for Lean Managers

Ten Reasons Why One Piece Flow Will Not Work

By Jon Miller Updated on April 30th, 2020

Rather than insisting that one piece flow will work, we like to ask people why one piece flow will not work for them. Here are some of the most common reasons we hear, and some ways we respond:

1. We can’t get needed materials in quantity, in quality or in time

You are absolutely right. Fix this first. If you can’t seem to get this issue the attention it needs, implement one piece flow anyway, watch the line stop, make the problem visible so that you get the attention and resources needed to fix the problem.

2. We have unreliable equipment that may break down, causing downstream processes to run out of parts.

See 1 above.

3. Our people will resist this change

So what? That’s what education is for. If the leaders don’t understand and believe in one piece flow enough to take the time to remove resistance through education, don’t bother with one piece flow. This is a weak excuse. Learn about motivation and address this issue as you would a speed bump in the road.

4. Our people are not cross trained to do more than one or two limited tasks

Shame on you for limiting people’s potential to learn and develop to their fullest. Take “boring” out of work by giving people variety, and watch morale soar. People are not motivated to learn new things you say? See 3 above.

5. Long changeover times prevent us from doing one piece flow

If you are really trying to run one piece lot sizes through 1,000 ton stamping presses, bravo, and see 1 above. Flow one at a time wherever you can. In practice you will find that this is more often than not. When changeovers do present a genuine barrier to one piece flow, reduce the changeover time continuously, all the while reducing lot sizes to approach one piece flow.

6. There is too much distance between processes to move one at a time

This is one I usually let the students figure out for themselves.

7. The process produces defects that will stop the line too frequently if we have no buffer

See 1 above.

8. Process cycle times are unstable or variable, creating an imbalance between workers

The first step is to examine your process cycle times through direct process observation, break the work into smaller work elements, take out waste, and recombine them. If chronic variation is still above the 5% to 10% range, see 1 above. If it’s predictable variation, this is only really a problem if you are trying to maximize the utilization of the man-hour, which may result in greater waste such as overproduction, inventory, transportation, defects and processing which adds no value. Proceed with one piece flow and kaizen.

9. Our machines are not designed for one piece flow

This is too true, even in our daily lives. A washing machine is a good example. Need to wash one shirt? You have to wait until you have close to a full load or you waste water and energy. So we batch our dirty clothes. The washboard and basin was the Lean solution, it just needs some jidoka. The same is true with a dryer. You don’t dry one wet shirt in the machine, but you might hang it up to dry if you don’t need it dry right away. Disciplines like 3P (Production Preparation Process) exist to create one piece flow equipment. If you cannot get equipment planners and designers involved early enough to keep bringing in batch equipment, see 3 above. Failing that, you can manage by using SWIP to “pulley & pail” flow through batch processes.

10. We have occasional work that interrupts the process

There is something in TPS called the Water Spider which acts as a line support function to handle relief work and recurring-but-not-every-cycle tasks such as moving materials in, moving finished goods out, building another cardboard box when the previous one has been packed full of finished product. When it is not practical to have a Water Spider, you can have foremen or team leaders help in these areas. Failing that, create Standard Work to reflect the changing work sequence and work balance every so many pieces for these types of recurring tasks.

Turn these ten reasons why one piece flow will not work by 45 degrees, and you get the Ten Reasons for Poor Cash Flow. Turn them by 90 degrees and you have the Ten Reasons for Long Lead Times. Whichever way you turn them, turn them into competitive advantage by addressing each of them and successfully implementing one piece flow.

  1. Chris Sereno

    April 25, 2007 - 2:56 pm

    Are there rules for what goes on a Kaizen newspaper so it does not become a massive action item list?

  2. Nancy Kress

    May 4, 2007 - 12:14 pm

    I need help to figure out #6. What if every item must travel the distance and batching items saves travel time?

  3. Jon Miller

    May 4, 2007 - 1:02 pm

    Hi Nancy. Why must every item travel the distance?

  4. Nancy Kress

    May 8, 2007 - 7:29 am

    Thanks Jon – I’m starting to figure it out!

  5. Alberto

    July 17, 2007 - 8:24 am

    For Chris. I’ve Used Newspapers for A, B and C items, all related to their importance.
    but what should go in a Newspaper is an action item that solves a problem… so if you have massive problems you should have a massive action item list
    about Q6 you should also wonder about the flow of the operation, is the distance really necessary? ( try thinking about U-shapes )

  6. John Bauer

    August 16, 2007 - 7:38 pm

    Jon, does Toyota or any other manufacturer really send a car or other good overseas one at a time? And if you build your factory next to my house, am I really a satisfied customer? If you have one ideal (one piece flow), and don’t recognize the other balancing ideals, don’t you risk being labeled as impractical?

  7. I Talk

    August 16, 2007 - 11:41 pm

    I tried the concept in printed circuit board assembly line design, but it seems not really practical when put it into actual business environment.
    There are several common problems in electronics contract manufacturing business environment, such as
    1. Unbalance of assembly equipment capacities
    2. Assembly method could be fully auto or fully manual. Too expensive to regularly down the auto line for product changes over.
    3. Non standard of electronics component packing quantity between suppliers
    Any many others reason
    Although I fail in the concept of one piece flow, but I still manage to survive in 3 piece flow.

  8. Jon

    August 18, 2007 - 10:04 pm

    Very good points. I have similar experiences in electronics manufacturing.
    As far as point #1, this is a problem with equipment design. Equipment in this industry is designed to maximize output by process rather than balance flow. Equipment design is not typically slower, smaller, cheaper machines that would allow for “additive” capacity. This challenge can be overcome with Production Preparation Process (3P) techniques used at the time when machine selection (before purchase) is done.
    Issue #2 is similar to issue #1, but this is also a question of line speed and number of lines. If the production model is to have fewer, faster lines then the behavior will be to do push production in large batches rather than stop and changeover the line. More lines that are smaller, slower, and simpler allow for quicker and fewer changeovers and small lot production.
    Issue 3 is a tough one as long as you are buying from low cost countries who ship in cardboard boxes in large quantities, unless you do the right thing which is to receive and repackage for easy of use on the factory floor. Unless your sourcing, materials and manufacturing people are synchronized in their thinking, you will have the problem of the lowest priced part costing a lot in manufacturing flexibility and efficiency.
    It’s great that you’ve made it work with 3 piece flow.

  9. Jon

    August 22, 2007 - 10:06 pm

    Hi John,
    Thanks for your good point about balancing one-piece flow versus other practical matters, such as transportation costs or the cost of having a factory for everything right next door to your house.
    One piece flow is not the ideal nor the end, but a means to an end. The end is reducing waste and making problems visible. One piece flow first exposes the waste, and also guides the design of processes that are more Lean (space, inventory, equipment size, energy use, human motion, etc).
    It would not be a good idea for Toyota to ship one car at a time to each customer. However you can walk to your garden and pick one tomato. So perhaps the automobile of the future that is waste-free and available on-demand one at a time is one that grows in your garden.

  10. Simon

    September 18, 2007 - 8:39 pm

    Continuous one peice flow is like a lot of lean principles – a simplified way of illustrating a method of waste reduction. Waste elimination is of course the foundation of TPS but total waste elimination can never be achieved – hence kaizen never ends.
    What must be understood about continuous one piece flow, as with all other lean ‘tools’, is it’s deeper meaning i.e. reduction of the 7 mudas and the exposure of problems.

  11. William Stevens

    January 16, 2008 - 9:56 am

    One piece flow can cost you in lost production during changeovers. This is hard to believe until you take a snapshot every 15 mins. or so during changeovers. Do this with different amounts of wip between processes and you’ll see that during changeovers, your production increases as WIP increases. IT’S just the opposite the closer you get to one-piece flow. Measure the number of parts that exit during the changeover period.

  12. ept

    April 7, 2008 - 4:19 pm

    The answer to one and two is “watch production stop!?” If this is your plan to make/save money and work as a team, I want no part of it.

  13. Jon Miller

    April 7, 2008 - 5:52 pm

    Hide your problem or expose your problem, you still pay for it. It’s better to pay for fixing it than to run at higher cost, is it not?

  14. lee

    April 12, 2008 - 5:08 am

    My shop deal in polyuthane Foam cut by a pattern (not spelled correctly, But you get the picture.) We make cushions for furniture. My Problem is not the One peice flow but the time it takes to correct a problem. When we have a problem we stop it cost us as a cell money! This should not be the case but when we try to talk to the higher ups about it they get defensive and rush our meeting closed. Makes me think maybe there trying to get me and some of the other employees that have been there for years (13) to quit, go find something else. Enlighten me please what should I do or say to management to get them to understand I can’t afford to loose money. Thanks Lee Bradshaw

  15. Jon Miller

    April 15, 2008 - 6:15 pm

    Hello Lee,
    It does cost money to stop, but it also costs money to make bad products or to have machine problems. Most companies don’t measure these costs too well. They only know that when the machine is running, it is making money (in theory at least).
    As far as trying to speak to the higher ups in a constructive way there are a few things you can try. The first step is to get on the same side. It should be “we” fighting the same problems, not fighting each other about which problem to attack or how to solve it. Even if you disagree about those things, you can always come back to what you agree about.
    The second thing is to speak in their language. If they understand numbers, try to use numbers (cost of defects, downtime, etc.) to help them see. If they understand stories and anecdotes more than management by fact, try to tell them some compelling stories about the problems you face and how this affects customers, or the performance issues higher ups care about.
    And most important, approach people with mutual respect. If you feel like you are being pushed out, that is not a good feeling. The higher ups may also feel like they are being pushed to an uncomfortable place by exposing these problems. If you can start by agreeing that it is safe and OK to expose these problems and talk about them with mutual respect, the rest becomes easier. If this is fundamentally missing, the best you can do is to stay positive and give respect for as long as you are able.

  16. Brian Quimod

    April 23, 2008 - 7:43 pm

    I agree with mentioned reasons abovet hat hinder 1 pc flow. I had encounter those problems during my study to implement 1 pc flow. but i firmly believe that all of those problems can be eliminated if we are going to take it one by one and solve. Those stated reasons can be solved and of course it would take time, money and effort to implement 1 pc flow.It’s all worth it.
    Posted by: brian i. quimod

  17. nitin

    August 8, 2008 - 7:24 am

    jon gr8 to know yr point of view its really interesting but can i get overall idea in full abt one pc flow work structure i’m in sheet metal component manufacturing for diesel engines

  18. David

    February 1, 2009 - 8:01 am

    The past couple of years we have been working on lean concepts , torn down wall , set up lines for product to flow and have gotten away from depts . Only in the past month have we really moved to cells and one pc flow , equipment that was always through equipment we have figured out how to feed back to the operators , What really hit me is that we always knew where the bottle neck was but when you are thinking of everything in batch how many pcs per hour it is very hard to see . but when you break it down to parts per second in a cell to determine cycle time of a product and go through the 3p process , with some very basic inexspensive ideas we were able to shave 1 second off a cycle of one product , no big deal right ? over 4 million cycles it is a big deal! now as you eliminate that bottle neck in your cell you have created another one to work on , wow we eliminated 2 seconds off that cycle , ok now your back to the original bottle neck , back and forth continually working on what restricts your cell in hours not days or months , we have no engineers or people waiting around to work on this stuff . but you need to react fast so your employees see you are committed to making their jobs easier and before you know it they are throwing ideas at you so fast you can not keep up . this is a journey for me over a couple of years and I think measuring in seconds instead of hours really helped me see ..

  19. Jackson

    October 6, 2009 - 1:23 pm

    Jon, I work for an offset web printer of short run magazines where we print about 60 titles a month. Some titles require 5000 copies others 50,000. Covers are printed on different stock and seperately from the bodies. After printing the copies must be gathered, bound and mailed. The presses can easily outrun the equipment in our bindery and every title has a specified date to be mailed. We have been using 5S, SMED, and employee suggestions methods to uncover opportunities for waste reduction. I understand the purpose of one piece flow is to discover waste and make problems visible but am stuck as to how to move to smaller batch sizes let alone one piece flow. What am I missing?

  20. Jon Miller

    October 6, 2009 - 4:38 pm

    Hi Jackson,
    It sounds like you are facing a technology barrier. Printing presses are not designed for flow but to maximize output of that individual process. The way to achieve one piece flow in the printing industry is to shift to using many slower low cost printing presses. Unfortunately this is not the prevailing technology. I don’t think you are missing anything. If you did attempt one piece flow you would simply be exposing the big problem that your machines are big, expensive and built for speed instead of flexibility.
    It’s good to keep you eye on the one piece flow goal wherever possible, and in the mean time make the most you can from ways to implement lean in a batch industry.
    See this article for more on that:
    Best wishes,

  21. LeanConsult

    November 14, 2010 - 8:02 pm

    People who are preaching 1 piece flow and recommending stop the line..plz own a mfg plant and try to experiment your idea and see who much money and effort it takes to make ur plant one piece flow for every freaking thing…it is not that easy for a small business owner to invest in a multi million dollar machine which can do fancily do my stamping and then heat treat one piece and kick it to temper…in one piece..
    There is a saying that those who cannot make it teach

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