The rope team: Theory of Constraints

Climbing the highest mountain in Northern Europe, a few thoughts on the Theory of Constraints came to my mind. To get to Galdhøpiggen, 2469 meters above sea level, the most common route takes you over a glacier where rope teams are used for safety reasons. In his must-read book “the Goal”, Eli Goldratt (1984) uses rope teams to illustrate an efficient production system. Why should you run your production as a rope team.? Why not?

In rope team towards Galdhøpiggen, Norway, 21-7-2013

In rope team towards Galdhøpiggen, Norway, 21-7-2013

A rope team is a number of people who tie into a rope at equal distances to each other. If one is unfortunate and falls into a crevasse (a crack in the glacier which might be open or covered by a superficial snow bridge) the rest of the team will easily (and automatically) pull him up again. For a rope team to function at best, everyone should move at the same speed, leaving the rope to hang relatively tight without touching ground.

Why a rope team is optimal

Some years ago, Goldratt’s book “The Goal” was the first business book I ever read, and it left a lasting impression. His simple but brilliant ideas of managing manufacturing operations by controlling the bottleneck (the constraint) and making all other operations move clock-pulsed at the maximum pace of the bottleneck. A drum sets the pace and lets everyone know what it is. To allow for some natural variation in the processes, a small amount of inventory in-front of processes work as buffers. Finally all processes are linked together as in a rope team. Together it makes up the drum-buffer-rope concept—the manufacturing application of the Theory of Constraints.

Our glacier guide on the way to Galdhøpiggen tells us that “the fastest way to move in the mountain is to move slow and even”. That is not a bad advice, and based on his many years of experience in getting diverse groups of people up steep mountains in all kinds of weather. Manufacturing operations are similar. Goldratt’s story about the little slow fat kid named Herbie, who is trekking with a stronger team on a boy scouts excursion, puts it very well (c.f. The Goal, Chapter 13-15):

The plan, I learn, is for the troop to hike through the forest following a blazed trail to someplace called “Devil’s Gulch” (…) After a few minutes, I turn and look back. The column of scouts has spread out to some degree from the close spacing we started with. Instead of a yard or so between boys, there are now larger gaps, some a little larger than others. I keep walking. But I look back again after a few hundred yards, and the column is stretched out much farther (…) I look up and notice that the boy in front of me is going a little faster than I have been. He’s a few feet farther ahead of me than he was a minute ago. So I take some bigger steps to catch up. Then, for a second, I’m too close to him, so I slow down. There: if I’d been measuring my stride, I would have recorded statistical fluctuations. But, again, what’s the big deal? (…)

Herbie falls over beside the trail, his tongue hanging out (…) Dammit, we’re going to be running and stopping all day long if this keeps up (…) Why can’t we all just walk at the same pace as Ron [in the front] and stay together? (…) That’s when I begin to understand what’s happening. (…) Our hike is a set of dependent events… in combination with statistical fluctuations (…) What if I were to say that this troop of boys is analogous to a manufacturing system; sort of a model. In fact, the troop does produce a product; we produce “walk trail”. (…) The idea of this hike is not to see who can get there the fastest. The idea is to get there together. We’re not a bunch of individuals out here. We’re a team.

“Now listen up!” I say. “This is the order you’re going to stay in until we reach where we’re going. Understood? Nobody passes anybody. Everybody just tries to keep up with the person in front of him. Herbie will lead!” Everyone else looks aghast. “You want him to lead?” asks Andy. “But he’s the slowest one!” says another kid. (…) We’re flying now, doing twice the speed as a troop that we did before. And we still stay together. Inventory is down. Throughput is up. Devil’s Gulch is lovely in the late afternoon sun.”

A rope team helps set a controllable pace in the troop of scouts and in a manufacturing plant. To achieve a “swift even flow” is a core idea in the Theory of Constriants, as it also is in mass production, just-in-time manufacturing, lean production, six sigma and mass customisation. It is a generally accepted theory in operations management. If you want to be super efficient, go for the idea of a rope team!

Why a rope team is no Nirvana

On the way down from Galdhøpiggen I took the opportunity to do a little research. Using my trekking company as a focus group, I asked a simple question: “So what do you think about tracking in a rope team? Was it fun?” The answers came quickly: “It’s boring”, “I’d rather walk in my own speed”, “It’s neither good nor bad” and “It’s OK at first”. I also found it boring.

The speed was slower than my usual pace, but, even worse, it was not rhythmic. Stop and go, go faster, go slower. One reason for this was that the team was diverse—young and old, strong and not so strong—which caused variance in pace. Second, I walked at the end of the 30 man rope team, suffering under all the co-variance of the team. I compensated the boring and varying pace by holding pieces of the rope in front of me in my hand (building “inventory”), and then let some rope out when the pace suddenly increased.

This, of course, is an absolute “no go”. If all do this, the takt system does not work. In fact, the bullwhip effect would make sure its no fun to walk at the end (maybe people in front of me did is as well?) The worst thing with people building “personal inventories” in rope teams is that it can have catastrophic consequences, because the rope team does not work as intended if people break through snow bridges. People should not do it, but I understand why they do so. Variances increases—so does co-variances—but it still feels more fun for the individual. And work should be fun, shouldn’t it?

Let me make one thing clear; rope teams are efficient and safe. For crossing glaciers there is no alternative. It just so happens that it is often dead boring, making people forget about their tasks and start thinking on other remote things… like writing blogs….

Agreed?

—–

References

Goldratt, E. M. & Cox, J. (1984) The goal: excellence in manufacturing, Croton-on-Hudson, N.Y., North River Press.

On the top of Norway, Galdhøpiggen 2469 MASL

On the top of Norway, Galdhøpiggen 2469 MASL

 

8 thoughts on “The rope team: Theory of Constraints

  1. Posted in LinkedIn’s Lean Six Sigma group.

    Why does the drum-buffer-rope concept lead to boring jobs? Have you ever seen a truly fun application (for the operators) of a super efficient “rope team” production system?

    • Posted in LinkedIn’s Lean Six Sigma group.

      First, my answer is no. I have not seen a funny application for the operators that can substitute the former self control felt with their No-rope walk over the glacier. But, I’ve seen what is happening when the operators day is left with the dull tasks. My experience and reflection is that we like to live with some risk, a risk level handled with the skill and experience gained over the years. It gives some “selfpayment” when you leave the work in the evening, knowing you fixed to day too. But as you mentioned, when the day becomes dull from the dull tasks, there is perhaps need for a system were there are variation so you do not fell into “sleep mode”.

      And were can that be? I think it should be linked up to the customers. There is the “random” world full of variation, and with some clever thinking “a truly fun application” can be made so the operator him self play the drum from what he see from the real worlds randomness included. It can actually become more LEAN with the drum beeing plaid by the operator from what he see in “the fun application”, then from a drummer playing for the operator.

  2. Posted in LinkedIn’s Lean Six Sigma group.

    Thanks for your thoughtful and constructive comment Håvard. I agree with you. In particular I like your reflection on “going home, knowing one did a days worth of work”. One question arises, though: can the fun factory we describe be truly lean? I don’t believe an orchestra of different operators can play drums in tact. It will be a good place to work, but not a super efficient factory (but does it have to be?)…

    • Posted in LinkedIn’s Lean Six Sigma group.

      Torbjørn, first, tanks for liking my input/reply. You ask a difficult question, again. And to give my answer, I think the answer is no, with one condition.

      The factory which I think is the winner need not necessarily be the one that is most LEAN by the “book”. My experience, which is limited to 15 years with varying production in what is one of the most expensive countries to produce in (NOWAY? = Norway!), is that to play on individuals’ feelings for successful performance is what applies. It leads to low absenteeism (It’s LEAN), high commitment (High efficiency) and will (No stop) to succeed with tasks related to the goals they have set for themselves.

      What is important is that the leader facilitates to allow for individual goals. Then the individuals goals get passed from the individual back to the leader. It ensures management/leader insight and opportunity to let each operator correct direction and goals. We also have the expression, to be in the same boat. If one is in the same boat, or playing in the orchestra, is some of the same. To add up to the most comfortable is to keep the time with the other, or to play in time with the others is the most fun, create winning team.

      To make it most comfortable to keep the time with the other, or to play in time with the others to be the most fun, will create winning teams. And a key term there is discipline. With disciplined people dispossessed acting by right thinking requires little bureaucracy. That is really LEAN.
      So the fun application asked for initially should perhaps be formed/designed so operators commonly, disciplined?

      PS: I will never cross a glacier without others and in a rope team, just so that is clear!

  3. Posted in LinkedIn’s Lean Six Sigma group.

    The late Dr. Goldratt’s subsequent books continued the story by applying to marketing and distribution, project management, and even ERP software. TOC works in all environments where there are linked processes and variation. The purpose of the rope in the glacier climb is for mutual safety so that if one person falls, they can be rescued by the others acting as an anchor. The purpose of the rope in TOC and the Herbie story is to tie the pace of all activity to the constraint, so that other resources do not waste their effort by going faster than the constraint. So I think the comparison, while interesting, is quite different.

  4. Posted in LinkedIn’s Lean Six Sigma group.

    Glenn; Thanks for adding the knowledge about Goldratt’s later books. That the main purpose of the rope team is different in manufacturing (flow) and glacier climbing (safety) is correct. But, that fact does not change the insight about its potentially boring jobs. The story about Herbie was clearly used as a metaphor for manufacturing. I think this is a trade off that has not been elaborated enough?

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