In a mixed model production line, different products may have different work content at different stations. Hence, some stations may need a longer or shorter time depending on the product. This requires careful planning of the assembly line. If this is not taken into account, it may cause significant idle time with all stations along the line. This is the first of a (very) long series of posts looking at Mixed Model Sequencing (i.e., the behavior of unbalanced workloads, and different ways to address these issues). Continue reading Mixed Model Sequencing – Introduction
In my last post I explained the basics of the bucket brigade as a self-organizing manufacturing line. The key to making this system work is the process for handing over the part to the next worker. An unsuitable hand-over could mean lots of waiting time for the workers. Hence, I would like to go into more detail on how to do the hand-over of the part. Continue reading The Lean Bucket Brigade – Part 2: Details and Caveats
Many topics in lean address how to deal with uncertainty and fluctuations (or mura for unevenness). There is a particularly neat trick for manual lines that self-organizes fluctuations in the workload: the Bucket Brigade (also known as bump-back or bouncing line)! It does have some advantages, but it also has quite a few limitations and prerequisites for it to work. Most importantly it works best only for very short cycle times as for example picking materials. Unfortunately, these requirements are rarely mentioned in literature. Let me show you the basics work in this post before I go into some of the trickier details in the next post. Continue reading The Lean Bucket Brigade – Part 1: Overview
Reducing inventory is one of the goals of lean manufacturing. In my last post I described why we need inventory in the first place, and why too much inventory is bad for you. Now let’s look at how we can achieve a good inventory level. First, an important statement: Inventory is not a lever that you can pull. It is more the result of other good lean improvements. In fact, merely pulling this lever and reducing inventory will actually make things worse. To gain the true benefits of lower inventory, other measures have to be taken. In this post I would like to describe what happens if you simply reduce inventory, and how to do it to achieve a lower inventory without causing mayhem in the process. Continue reading How to Reduce Your Inventory
Inventory is expensive. Depending on your environment, inventory will cost you between 30% and 65% of its value. Toyota is known for (among other things) small inventories. Whereas Western companies often have weeks’ or even months’ worth of inventory, Toyota’s inventory is measured in hours.
It is no surprise that inventory reduction is high on the list for many companies. In fact, the term “lean” by itself implies lower inventories. But why do we have inventory in the first place? And why is (too much) inventory considered evil in lean manufacturing? In this post I would like to tell you the reasons why we have inventory in the first place, and why too much is bad. In my next post I will explain what happens if you simply reduce inventory, and discuss in more detail better approaches on how to reduce inventory. Continue reading Why Do We Have Inventory?
Manufacturing systems have fluctuations. Material may arrive sooner or later. Production may be fast or not. The customer may order more or less. Generally, the less fluctuations you have, the more efficiently you can produce. Toyota puts in an enormous effort to control fluctuation, but even they have fluctuation. In this post I would like to show you the three basic ways how you can decouple fluctuations: inventory, capacity, and time. Continue reading The Three Fundamental Ways to Decouple Fluctuations
One successful approach to leveling is one-piece flow leveling (also known as single-piece flow or continuous flow). Last week I described the theory. This week I talk about implementation, and its combination with capacity leveling. I also look at what else there is in leveling. Continue reading Introduction to One-Piece Flow Leveling – Part 2 Implementation
One successful approach to leveling is one-piece flow leveling, which I would like to talk about today. Another successful approach is capacity leveling. These can also be combined. (But please do yourself a favor and stay a way from a longer fixed repeating schedule EPEI leveling.) As the name already says, you should drive your lot size toward one. In addition to one-piece flow, this approach is also known as single-piece flow or continuous flow. Continue reading Introduction to One-Piece Flow Leveling – Part 1 Theory