We all know about muda, but what about mura? It is just as important to tackle, since it causes a lot of problems for both the customer and the employees.
What is mura and why is it bad?
Mura is about variance. The word mura comes from Japanese. It means unevenness, irregularity and lack of uniformity. Mura blocks flow. You can recognize mura by production which knows peak and slow periods, which tend to lead to frantic production or slow times. It leads to lay offs in slow times and overtime and burn out in busy periods.
Mura can mean variance in supplies, customer demand, product mix and production methods. Any variance will cause degradation in performance of machines, processes and people. To counter this degradation in performance buffers will be put in place. These buffers in capacity, inventory and time cost money and will lead to additional wastes.
How to counter variance in supply chain?
Mura in your supply chain can be deadly for a lean company. When companies do not share variations in customer demand and delivery times each supply partner will be caught off guard when demand grows or shrinks. This will lead to bigger inventories and wait times. There are several ways to reduce this effect:
- Share information about variations in customer demand and their causes with your supply partners
- Try to reduce the number of supply links in the process. This reduces complexity in your supply chain
- Try to reduce the distance between the supply links. This reduces complexity in your supply chain
How to counter variance in processes?
Mura in your processes leads to high changeover times and to production which does not meet customer demand. To lower the changeover time you can develop modular products. This will lead to less changeovers even when you switch in product, because you can use these modules for several products.
You also get mura in processes when the takt times are not balanced. Inventory and production are dependent on who works in which step. You also need to look at the physical lay out of your process as well. When distances inside a process are long, this distance will add risk to moving products upstream.
If you want to reduce variance in your processes you need to work in standardized processes. You can use instructions, visual cues, 5s and kaizens to do this.
What to do about mura in your customer demand?
Customers are not like robots. They will not order your products in exactly the same order or batch sizes. This means that producing to customer demand can be quite a challenge. When you change production with each change in customer demand, you will always be behind schedule. This way of planning will lead to a highly unpredictable production mix. This variance will lead to muda and less predictable production. In order to reduce this effect you can use the heijunka box, kanban, SMED (single minute exchange of die).