Reducing Fluctuations Upstream

This post will list a number of tools that can help to reduce fluctuations. They can reduce fluctuations in the material flow, including its inventories and the durations and lead times. Since reducing fluctuations (mura) is an underlying important idea throughout lean manufacturing, a lot of tools can help. And, depending on how you interpret tools, this list is not even complete.

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Structure for Reducing Fluctuations

This post looks at how to reduce fluctuations (mura) in manufacturing. It is a continuation of the previous post that looked at why fluctuations are so bad. Be warned, tackling fluctuations is often a tedious task that never ends, but it one of the important fundamentals for lean manufacturing. After all, the more stable a system runs, the more efficient it is. Leveling is one major method to reduce fluctuations that focuses on the production schedule. Line balancing is another one that focuses on the work content. 

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Why Are Fluctuations So Bad?

Fluctuations are bad for manufacturing. In lean, unevenness is one of the three evils, besides waste and overburden. In this post I will give you an introduction to fluctuations. One option to handle fluctuations is decoupling, but this addresses only the symptoms and not the cure. In my next post I will show you how to actually reduce fluctuations.

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When NOT to Balance a Line

Line balancing is one of the important methods for improving your production system. The idea is to give every process the same workload so all processes are busy all the time. However, there are cases where it may be better NOT to balance a line. This post will look into when and why you may choose not to balance your line.

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Toyota’s Six Rules for Kanban

Simple Kanban LoopThe kanban system is the most famous way to establish a pull system. As part of their guidelines for kanban, Toyota has established Six Rules for Kanban. They can be found, for example, in the 1973 Toyota Production System Handbook. This blog post describes these six rules, based on the Toyota handbook. While these rules are all true, they are in themselves not sufficient to establish a kanban pull production. Nevertheless, this post will show you these six rules.

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How to Convert a Job Shop into a Flow Shop – Part 1

Ford Motor Assembly 1917
Ford motor assembly with moving conveyors 1917

Job shops are always very difficult to manage. As I described in my previous posts, the irregular material flow causes fluctuations that are very hard to contain. In my view, the only true fix for a job shop is to convert it into a flow shop. In this post I will talk a little bit about how you approach the idea of converting a job shop into a flow shop … although this is not always possible. However, in many cases it is possible to increase flow-shop-like segments, even though the whole system is still a job shop.

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Why Are Job Shops Always Such a Chaotic Mess? Part 2

Ford Piston Shop 1917
Ford piston shop 1917

Job shops are a mess. Period. The increased and uneven levels of inventory cause a host of other problems. In my last post I described how these inventory imbalances are caused by irregular material flow, how subsequent safety buffers increase inventory even more, and how this causes staff to change their workplace irregularly in a job shop. In this post I will continue the long list of ills in a job shop with staff changeover losses, extra searching and organizing,  fluctuating lead times, and general un-plannability of job shops.

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