Do you want to know more about lean ideas, and how you can start implementing them using your favorite authoring tool? Keep reading!
These are some of the main principles in lean thinking:
- Define value from your customers’ perspective
- Map the value stream for each product that provides that value, and challenge all non-value-adding activities. Focus on eliminating waste.
- Visualize your work to help find waste and problems.
- Make the product flow continuously through the value stream, reducing ques and batch work. Focus on flow efficiency over resource efficiency.
- Pull work through the value chain, don’t push it.
- Continuously improve – striving for perfection, never reaching it. Reduce the number of steps and amount of time and information that’s needed to create the customer value. It’s a mindset!
- Problems are opportunities to improve. Use the “5 Whys” method to get to the root cause of a problem, and use “A3 thinking” to find and test countermeasures to the problem.
Does this really work?
It seems to work just fine for successful companies like Toyota, Nike, Caterpillar, Intel, John Deere, Ford, and the Virginia Mason hospital in Seattle.
In Malmö, Sweden – an experiment with lean healthcare brought down the time a breast cancer patient had to wait for a diagnosis from 42 days to 2 hours. That’s a 500-time reduction in lead time.
Resource efficiency versus Flow efficiency
Lean thinking means focusing on flow efficiency over resource efficiency. So what’s the difference between the two?
Focusing on resource efficiency means that if we’re running a hospital, we’d want to keep our doctors busy 100% of the time, because we pay them a lot of money – and we want our money’s worth. To ensure that they are always busy, there will be a queue of work: patients in the waiting room.
Focusing on flow efficiency means that we want as much value-adding time as possible for the patient, even if that means the doctor is only busy 60% of the time. This approach costs more, but adds significantly more value to the patient. The excess capacity means that the doctors can focus on finding problems and making improvements to the process, making it flow even better, or even become more resource efficient at the same time.
Can’t we have both?
The desired state is of course to have a high degree of resource efficiency AND a high degree of flow efficiency. It’s very hard to attain, and there is almost always a trade-off between flow and resource efficiency. The more variation there is in a process, or in the input, the harder it becomes to combine high resource efficiency with high flow efficiency. This means that a factory making a million units of the same widget will have an easier time combining resource and flow efficiency than, for example, a hospital – where the process inevitably has more variation. Usually, whenever people enter the equation, the variation goes up – and we can’t control and standardize people the way we standardize products. In the diagram below, the effective front is somewhere along the red line, and variation “pushes” the line down, creating more and more of an “either or” situation, where a high flow efficiency comes at a higher cost to resources efficiency. Standardization of processes and of inputs is a key factor in reducing variation.
Can we have some more science please? Sure – let’s bring on the math!
To model and explain why lean principles work, we can apply some queueing theory.
Kingman’s formula connects resource efficiency to waiting times
Kingman’s approximation states:
where τ is the mean service time (i.e. μ = 1/τ is the service rate), λ is the mean arrival rate, ρ = λ/μ is the utilization, ca is the coefficient of variation for arrivals (that is the standard deviation of arrival times divided by the mean arrival time) and cs is the coefficient of variation for service times. (https://en.wikipedia.org/wiki/Kingman%27s_formula)
The formula tells us that the lead time increases when process or input variation increases:
It also tells us that increased resource efficiency leads to a higher sensitivity to variation. If resource efficiency is high, variation has a higher impact on waiting times:
Lean thinking focuses on flow efficiency over resource efficiency, reducing waiting time in the process. Lean thinking also focuses on creating standards to reduce variation, thus also reducing waiting times.
Little’s law connects lead times to Work-In-Progress
Little’s Law tells us that the average number of customers in the store L, is the effective arrival rate λ, times the average time that a customer spends in the store W, or simply: Assume customers arrive at the rate of 10 per hour and stay an average of 0.5 hour. (https://en.wikipedia.org/wiki/Little%27s_law)
This means that the lead time increases when the number of flow units increase, or when the cycle time increases. This is why it’s so hard to pick the right line at the supermarket or at the airport security check. Even if there are just two people in the queue, input variation (someone forgot to leave their nail clippers at home) will increase the cycle time , whereas the other queue with 10 people could very well move faster because those 10 people are all efficient business travelers – and the process variation is less significant.
Lean thinking focuses on reducing the work in progress (WIP), thus reducing the lead time given that the cycle time stays the same. Reducing the work in progress also has a psychological effect – giving you space to think about improvements, ideally giving to room to find and eliminate waste to reduce the cycle time – creating an ever lower lead time.
How do I get started?
If you’re a techwriter, a great entry point to get started with lean thinking is to start using a Kanban TOC to manage your writing projects.
A Kanban Table-of-Contents is a TOC where you have mapped your process/value stream and added your work items to a backlog:
In this case, the work item is a set of documentation for a new feature in the product. The work item in turn is a separate TOC, containing all the topics you need to write or update for the given feature:
As work progresses, you move the work item TOC to the next node in the Kanban TOC, keeping track of where in the process the work is.
At the same time you make sure to limit the Work-In-Progress at any given node to three items. This means that if something is stuck, you see it immediately, and you can swiftly address the problem, figure out the root cause, and try out some form of countermeasure to get the work items moving again.
Questions or comments? Let me know! 🙂
Interested in knowing more? Come see my presentation at TCUK in Glasgow next week.