Leveling Production

Leveling production is a Lean technique for reducing waste and smoothing out the fluctuations of production. This allows us to create production assets a constant a predictable rate.

Much of the time we spend in production is wasted on work or activities that don't add to the final product. By making these wastes a focus of our effort, we can get a huge increase in productivity.

Kanban

Anyone that has used a Scrum has used a simple Kanban system. In Japanese the word Kan means "signal" and "ban" means "card". Therefore Kanban refers to "signal cards". Kanban represents a "pull system" for work.

A Kanban card is a signal that is supposed to trigger action. You can see Kanban everywhere. The next time you order a barista drink at Starbucks you can see a Kanban system in place. The coffee cup with the markings on the side is the Kanban! (1)

With Scrum, a team member "pulls" a card across a board on a daily basis as accomplish work. No one is pushing the work at them in at a predefined rate.

We can employ some of the practices of Kanban that are not used in Scrum to visualize a complex production stream and allow us to apply lean principles to make that production stream as effective as possible.

Heijunka Boards

A Heijunka board represents the Kanban systems that use cards that represent the capacity and workflow across a value stream.

As mentioned, when you use a Scrum Task board, you are using a very simplified Heijunka board that represents a three or four stage value stream. We can expand this in production by adding the steps to our level production value stream example:

Now we have eight states for each level to be in, which represent the six stages of our value stream, and states at either end that contain levels not started or levels completed. This rotates the typical tasks of the stream into states on our Heijunka board.

This board communicates the flow of work in a level production stream more clearly than a Scrum task board.

Applying Lean Principles

Now that we've represented our value stream for level production, we can begin to apply some of the Lean principles to incrementally improve level production. The first step we can take is to look at the cycle time of our value stream.

Cycle time is the amount of time that it takes for a level to enter from the left in script treatment to the end when the tuning pass is done. In our example above a level takes 16 weeks of cycle time. By reducing cycle time we can be more efficient:

- Faster cycle times means more productivity.
- The more frequently something comes "off the line", the more we can fix problems with the production line.
- We can identify waste more easily and address it.

There are a number of ways to reduce the cycle time. The first way is by finding ways to reduce the size of things in the stream. For our level production example, we can do this by splitting levels up into sections, or "zones".

Each zone takes approximately 12 days to pass through the value stream -- as opposed to 16 weeks for each level. As a result, our Heijunka board looked like this:

A Heijunka board shows the progression of a zone through each stage of the value stream. In the example above, Zone 1 has stepped through each stage and been handed off to the final Tuning Pass stage at the end. This board represents a perfectly balanced flow of work across every step of our value stream.

It won't initially happen this way. There will be gaps that appear in some columns and pileups of work in others, but that's the point of doing this: those problems will be visible as soon as they occur. When we achieve transparency, we can start to fix the problems that we clearly see.

How to Improve the Flow

Now that we have a Kanban up and running, we have to work on making it as effective as possible. The Heijunka board will show us daily where there are gaps or pile-ups in our flow. We not only want to keep things balanced, but we want the flow to be as quick as possible.

In our example, if each zone takes 12 days to pass through the entire stream, we want to find ways of reducing that as far as we can without sacrificing quality below the level the customer will accept.

There are a number of tools we can use to improve the flow:

- Time-boxing
- Leveling workflow
- Reduce waste