Some people say lean manufacturing cannot be learned, it can only be experienced. I agree with this statement, as “lean” is not just a collection of rules. Worse, more often than not, the opposite is true and what has been the “golden rule” nine out of ten times, the tenth time it will be your worst enemy. This is captured well in Christoph Roser’s article “What is the true North in lean?” who uses the analogy of a compass needle that gives you very good directions to the North pole until you get actually close. Then, the compass needle will point you to the magnetic north pole (which is not quite where the geographic pole is) and eventually let you turn in circles.
This does not mean that you cannot experience “lean” by immersing into a good narrative (not what you get today) or by putting theory into practice at home. One of my least favorite tasks is emptying the dishwasher. I cannot really describe why it is so much worse than loading it. Maybe it is because I can feel that I somehow waste my time, but cannot say how.
This article will use the dishwashing task to explain some of the key tenets of lean thinking by
- Letting you ask the right questions. What is your goal?
- Introduce the “seven deadly wastes”, strong indicators of things going not lean.
- Illustrating why “lean” is a continuous improvement process and why simply following rules will not work.
What is your goal?
What it is that makes unloading the dishwasher so annoying? Answering the question on what to optimize is never easy. In manufacturing, you want to manufacture things as cheaply as possible. Do you really? Or, do you want to make things as fast as possible? Indeed, whether you need to optimize for efficiency, i.e. the ratio of what goes in and what comes out, or throughput, i.e. the amount of goods that come out, really depends on your business.
As we cannot really pinpoint what it is that makes unloading the dishwasher so unrewarding, let’s focus on getting it done as quickly as possible. Time is easy to measure using a stopwatch. How can we go about decreasing time then? Is it to try to move as quickly as possible, risking that dishes break every now and then, leading to defects, this first of the “seven deadly wastes”? That might be not sustainable. We are rather interested in simple changes that do not lead to increased tear and wear on both dishes and people, but being able to do more with less.
The first exercise is to identify the different subtasks that emptying the dishwasher entails. The first is taking items out. This is where we really make progress toward our goal. The second is placing items in cupboards and shelves. Finally, we need to move items between the dishwasher and their storage location. Transport is always waste in lean thinking. It is quite easy to detect and reducing it usually goes a long way.
This leads to the first (quite obvious) insight to store dishes as close to the dishwasher as possible.
For example, left or right above the dishwasher for light dishes and left or right next to the dishwasher for heavy pots minimizes not only transport, but also motion. Motion is waste, and optimally one would elevate the dishwasher just enough that bending down is reduced. All of this is often not possible in most kitchens, and most adventures into “lean” often end when the obvious improvements are not applicable. Fortunately, the dishwasher problem – as most trivial looking problems in manufacturing – is surprisingly deep.
Giving up now is actually fatal. Not having access to an optimal storage location is already a problem. Even more effort should therefore be put into optimizing your second choices. Most people don’t do this, however, as they underestimate the big impact that the sum of small changes can have in the long run.
The first question you should ask yourself is whether you can get away with a more compact assortment of dishes and cutlery that can indeed be stored in a more optimal location. All sorts of excess inventory is usually waste, which includes “work-in-progress”, such as dishes sitting in the dishwasher waiting to be loaded. While the answer here is “no” for most people, and there indeed is an occasional need for even the fanciest sauciere, this leads to a consideration of frequency of use.
Frequently used items should be stored in the closest location, those less often used should be stored in the furthest available location.
This is probably already the case for most people and if it is not, this has probably been one of the most useful articles you have read in a year. But there is more we can do.
Now that we have minimized the overall motion that is required to solve the problem by optimally assigning item groups to a set of locations (a computationally hard optimization problem known as the “quadratic assignment” problem), it is worthwhile to take a closer look at what actually happens during that wasteful motion.
Our first realization is that we would want to carry as much as possible everytime we go. This becomes pretty clear when imaging that walking back and forth between the drawer and the dishwasher for every single spoon will take much longer than moving the cutlery by the handful. This directly informs how we carry out the emptying task – we should try to grab as much items as we can before going anywhere.
Many more items can be carried when stacking them, we should therefore focussing on unloading items in groups of identical objects.
It turns out that some items stack better than others. For example,
I can easily grab 10-15 spoons in a single hand or stack 10 or so dishes, but I have a much harder time with glasses, moving only two in each hand. Glasses also don’t stack well with mugs, which don’t fit with wine glasses and so on. This introduces a second “frequency” in our consideration. Some groups of items, such as dishes, can be moved during one or two trips, whereas glasses and mugs require many trips.
Groups of items that require many trips from dishwasher to storage location should be closer than groups of items that can be stored in fewer trips.
(Readers already familiar with lean will notice that batch sizes of one are usually a “golden rule”, but are always a trade-off with motion and therefore not desirable here. This is a typical conundrum in lean thinking, where blindly applying a rule would be very bad.)
Now that we better understand how to speed up the unloading
process, we might also want to think about how to load the dishwasher. In an ideal scenario with storage to the left and the right of the machine, we should load items accordingly. As we want to grab as many items as possible and stack them, items should also be loaded this way. This can usually be achieved without any additional cost, but pays off downstream.
Has everything been said about the dishwasher unloading problem? Far from it.
“Lean” is a continuous improvement process. This is because some improvements will also only become obvious once the first steps are done.
For example, now that you have minimized motion, it might make sense to think about moving item groups on a tray. This bears the question whether reduced round trip time justifies the additional manipulation (placing and picking from the tray). This problem can probably only be solved using a stopwatch. It is also interesting whether motion could be completely reduced by working with a partner who is strategically placed and to whom you can hand over items. Whether this approach is more than double as fast as when you do it alone (super-linear!) will depend on whether you can balance your line, that is reduce waiting – another form of waste – for either you and your partner while one is storing or retrieving an item. Also, now that every second counts, opening and closing cupboards and drawers becomes a nuisance. While good organization and planning can help to open and close each cupboard only exactly once, some might start thinking about structural changes and remove unnecessary doors.
Lean makes it easy to get carried away in details, however. There are two additional wastes that are easily overlooked in a smoothly running system that has been tuned by a genius. First, not everything in the dishwasher might actually need washing, but instead could have been stored right away or after a quick wipe-off. This kind of waste is known as over-processing and is very common, but much harder to detect. But what is really the dumbest thing one could do? Putting dishes away right before setting the table. This is as good as having to throw away what you just made and is known as overproduction. Therefore, always grab dishes from the clean dishwasher and only start it once you start running out on critical items. (Manufacturers manage the equivalent of this process using a so-called Kanban card.)
If you make a living of dishwashing (kind of like manufacturers do by making things), you might also think about structural changes to your operation, creating an optimal setup for your operation. Don’t forget that the dishwasher needs to stay next to the sink, not just for the plumbing, but also for the rinsing, otherwise all your new savings are gone quickly down the drain.
The goal of “lean” is to
- Make a process as fast as possible.
- Make a process as cheap as possible.
- Maximize efficiency.
- Maximize throughput.
- Whatever maximizes your bottom line.
In lean thinking, what is not considered “waste”
- Items that break during the process.
- Unnecessary motions.
- Time an employee waits.
- Overprocessing of items.
- Efficient use of a worker’s time.
Replacing the human worker with a robot that does the job half as fast, but at half the operational cost is a different approach to make this process “lean”. Which statement is correct?
- True. Increasing the bottom line is the overall goal.
- False. The process in itself is sub-optimal and needs to be improved first.
- False. Dishes need to be available as quickly as possible and the lower speed of the robot disrupts “flow”.
- True. Replacing human with machine labor reduces uncertainty and makes the process more predictable.
- All of the above.