Lean Manufacturing Wastes: Mura
In our previous article, Lean Manufacturing Wastes: Muda, we began to explore the concept of waste and how to reduce it. Wastes in your process add extra costs, either to your customers or to your business. Reducing waste is the most essential step towards developing a smoother and more efficient process.
The 7 Mudas (Transportation, Inventory, Motion, Waiting, Overproduction, Overprocessing and Defects) are often highly visible in your process and easy to single out. Many businesses reduce Muda, see some benefits, and stop there. However, the Lean Manufacturing methodology identifies two more causes of waste: Mura (unevenness) and Muri (overburden). In this article, we’ll take a look at the second waste, Mura.
What is Mura?
Mura is the Japanese word for “unevenness, irregularity, lack of uniformity”. It describes “feast and famine” cycles of work when some periods are significantly busier than others. It is a barrier to flow.
Frantic work as deadlines approach, and then periods with not enough to do – sounds familiar? Mura directly leads to the other two wastes, Muri and Muda, alternating periods of overburden with periods of waiting and underutilization. Reducing or eliminating Mura leads to a smoother, more consistent and more predictable workflow, tackling the other wastes at their source.
Mura in knowledge work
The concept of Mura comes from the Toyota Production System, the historical ancestor of the Lean Manufacturing methodology and Kanban. Originally, it was primarily used to describe unevenness in a factory or manufacturing environment – unevenness in customer demand for a product, large batch production causing inventory swings, uneven production speeds causing a lack of synchronization between processes. However, knowledge and service work still suffer from this waste. Let’s take a look at a few examples of Mura in knowledge environment:
- Uneven customer demand
The customer is always right, but what does the customer want? For early-stage startups, defining customer requirements and keeping track of them as they change can be a nightmare. Planning too far ahead can lead to wastes if customer needs have changed by the time the project is delivered.
- Uneven workload
Sometimes your team is stretched to breaking point. Other times, team members don’t have enough to occupy their time. This often follows uneven customer demand but also goes hand in hand with large batch delivery sizes.
- Irregular working rhythm
Irregular working rhythm happens when tasks pass through your process erratically. Work in progress accumulates and bottlenecks form in some stages of the process, causing an interruption to the flow of work. Irregular working rhythms lead to high variability in throughput and cycle time, leading to a less predictable process.
How to reduce Mura: Kanban
Mura is inextricably linked to the other two wastes, Muri and Muda. Reducing Mura as much as possible is crucial to keeping Muda and Muri at manageable levels – it’s arguably the most important factor in reducing waste, and the most difficult one to implement consistently across an organization.
The Kanban Method has exploded in popularity, mainly because of its simplicity. Kanban focuses on increasing workflow efficiency and helping teams to achieve continuous improvements. It uses several powerful tools for identifying areas of Mura within your process and working to eliminate them. Read on for our top tips for using Kanban to reduce Mura.
Visualize your workflow
Visualization is one of the key principles of the methodology – a picture is worth a thousand words. The Kanban board makes bottlenecks immediately apparent, and changes in the gradient of the cumulative flow diagram are a warning sign of problems brewing and increases in Mura. You can also use charts such as the cycle time scatterplot and throughput histogram to assess your level of Mura over time – more regular and consistent results means your efforts to reduce Mura are working.
Long-term directions, short-term details
Uneven and changing customer demands lead to Mura. Customer demands will inevitably change, so how can you reduce the Mura effect on your team? We recommend developing a Kanban roadmap to set your goals and directions, rather than planning in detail what tasks you will be working on six months from now. In the short-term, project managers and other stakeholders can then translate these goals into work items, prioritize them accordingly and feed them into the backlog. This lets your team pull tasks into the workflow at a steady pace. The Kanban Method suggests an approach of backlog management that reduces the effort of maintaining your backlog and helps teams become more self-managed.
Work in Progress limits and pull policies
Accumulation of work in progress in any one process stage inevitably causes unevenness. Kanban work in progress limits are used to avoid this – new tasks cannot be pulled into a process stage before an outstanding task has moved to the next stage. This can help you maintain a steady flow of tasks. Make sure to have explicit pull policies to ensure tasks enter and leave process stages in the same order, or your cycle times will become more variable.
Find your constraints
Irregular working rhythms are a major cause of Mura. As mentioned above, this frequently occurs because of slow process stages affecting up and downstream stages. The theory of constraints states that the flow of a process can be no greater than its slowest stage – its constraint. Improving the constraint improves the flow, making the working rhythm smoother and more consistent.
There is no magic bullet to eliminate Mura from your workflow once and for all. There are hundreds of factors that can cause unevenness within your process, both within and out of your control. Nevertheless, making these incremental, iterative changes will have a cumulative effect – a more predictable and profitable process.
Where have you noticed Mura in your process? What steps did you take to reduce it? Did you notice a parallel reduction in other wastes? Tell us about your experience in the comments!
Meet the Author
Sonya Siderova is a passionate product manager and a driving force behind Nave, a Kanban analytics suite that helps teams improve their delivery speed through data-driven decision making. When she's not catering to her two little ones, you might find Sonya absorbed in a good heavyweight boxing match or behind a screen crafting a new blog post.