Designing a kanban system on paper is much easier than implementing it on the shop floor. In many of my previous posts I discussed the design of a kanban system in detail. In these two posts I will discuss the steps needed to actually put the system on the ground. This first post is the preparation, and my next post will be the actual switch to the new kanban system.
- A value stream design of the new system
- The number of kanban you want to use for each part type (either by calculation or – my preference – by estimation)
- The physical type of the kanban
- The data that goes on the kanban
- Coordination with and support from the people actually using the kanban system
Safety Stock and Timing
Depending on the extent of your changes, you may disrupt production. If something goes wrong, you may also need more time than expected. One possibility is to build up some buffer stock before the implementation to avoid stock-outs.
On the other hand, the more inventory you have, the more inventory is in your way for the actual implementation of the supermarket. You may have to store the goods elsewhere to have the space to install a supermarket and make other changes if needed. A good compromise is to plan the change for a seasonal period of low demand when you don’t need much material anyway. For example, if you produce ice cream, don’t tinker with the system during the hottest days of the summer!
For your kanban system to work, you need a supermarket. See my posts for Theory and Practice of Supermarkets – Part 1 and Part 2 for details. The supermarket has to be set up depending on the type and quantity of containers that go in there. Ideally, the supermarket should be able to hold all the products for all the kanban cards in circulation. If you are really short on space, you may be able to get away with less space for some high runners, but then you need a backup plan for where to put the material if the supermarket is full.
If the container size allows it, then supermarkets are well suited for rolling lanes. You add the material on one side and it rolls or slides down to the other end. This way it is very easy to create a first-in, first-out system for a supermarket.
In any case, you would have to get an actual supermarket. There are lots of details that are necessary. Does it fit the material? Does it fit in the space? Do you need electrical connection? Is the storage rated for the weight? Are the emergency doors still accessible? The list is endless, and the questions above are only examples of what you may have to keep in mind. If you have the equipment for the supermarket already on hand, you have to install it. Otherwise you have to first order the equipment and then install it. Of course, it is easiest if the equipment is already there and you can re-use the already installed equipment.
The Kanban Cards
You need kanban cards. Even with a digital system, this usually includes a printer with printed cards attached to the material. Simply print the cards and if necessary insert them in the kanban cover, attach them to the kanban box, or otherwise prepare them. For details on the design of the kanban card, see my post on Kanban Card Design.
Pro Tip: Print a few more cards and put them in your drawer. If for some reason you estimated too few kanban for your system, you can simply pull some more cards out of the drawer and bring them into circulation. You also may need them for the ramp-up if you have more material than kanban cards (see next post). Of course, ideally it should be the other way round: your estimate was too large, and over time you reduce kanban cards from the system. More on that below.
The Flow of the Kanban Cards
When parts are taken out of the supermarket, the kanban card has to go back to the source to get more parts. Walk the way the kanban cards would go back to the source. Don’t add any cards yet; we will do that later. Ask yourself the following questions:
- Who would bring the kanban cards back?
- How often would this happen?
- Where would the kanban cards be stored at the supermarket in the meantime until the kanbans are picked up to be brought back? (Sort of a mail box for kanban cards.)
- Where would the kanban cards be dropped off?
- If you create lot sizes of more than one kanban card of the same part type: Where? How? Who does it?
- How do you organize the waiting of the kanban for processing? It should be a first-in, first-out system, with the kanban card waiting for production the longest (first in line) should be processed first (unless you have a more complex prioritization system in mind — then see my series of posts on prioritization for details).
The Flow of the Material with the Kanban Cards
Now walk the way from the start of the production or transport back to the supermarket. Again, we don’t add any kanban cards yet but merely see how the card would move along the line. The kanban should stay with the part at all times. Is this possible? Of course, if for example the part goes through a tempering oven at 1000°C, the paper kanban card won’t make it. Same for coating processes where the kanban is attached to the part.
- Where would you have to remove the kanban? By whom?
- Where would the kanban be put temporarily?
- When is the kanban attached to the part again? By whom?
You see, there are tons of little details to take care of. I highly recommend doing this together with the workers who will handle the kanban cards, both for the information and the material flow.
Okay, now we are ready and prepared to do the actual switch of the kanban system. This will be described in more detail in my next post. In the meantime, stay tuned, and go out and organize your industry!
P.S.: These two posts are based on a question by Felix.