Mura is one of the three types of waste (Mura, Muri, Muda,) and a key component to the Toyota Production System.
Unevenness in an operation; for example, a gyrating schedule not caused by end-consumer demand but rather by the production system, or an uneven work pace in an operation causing operators to hurry and then wait. Unevenness often can be eliminated by managers through level scheduling and careful attention to the pace of work.
The goal of a Lean production system is to level out the workload so that there is no unevenness or waste accumulation.
Mura causes Muda, the seven wastes are symptoms of our failure to tackle Mura and Muri within our processes.
Meaning of Mura
-Unevenness
-Irregularity
-Lack of uniformity
-Nonuniformity
-Inequality
-Variation
Examples of Mura
Tackling the Mura within a process should ensure that workers can work far more efficiently and with minimal stress within a processes. Limited examples below:
- Uneven customer demand
- Inventory swings – from too much to too little
- Uneven production speed or changing production quantities
- Uneven quality of good parts if scrapped it is waste)
- Irregular or erratic working rhythm
- Uneven training of the workers
- Uneven distribution of the workload
How to Avoid Mura
Leveling:
Also called Heijunka in Japanese and roughly means ‘levelisation’. Control inventory at different stages in the process are key to ensuring that “pull” is happening between sub-processes. Leveling production, even when different products are produced in the same system, will aid in scheduling work in a standard way that encourages lower costs.
Takt Time:
Takt time is the heart beat of the process or the drum beat which it should follow. The rate at which a finished product needs to be completed in order to meet customer demand. If a company has a takt time of 10 minutes, that means every 10 minutes a complete product is produced because on average a customer is buying a finished product every 10 minutes.
Just-in-Time:
Mura can be avoided through the Just-In-Time ‘Kanban’ systems and other pull-based strategies that limits overproduction and excess inventory. The key concept of a Just-in-Time system is delivering and producing the right part, at the right amount, and at the right time.
The Hockey Stick Effect
The measures placed on us drive uneven production; the famous hockey stick graph is the most obvious representation of Mura. Everyone works like crazy in the final week of the month depleting every sub assembly and production part that you have to ‘get the numbers out’ before the end of the month. Little thought is given to actual customer demand; they just need to get as many parts finished as possible so targets for the month are met. The first week of the month is then very slow as sub assemblies and supplied parts have been depleted and it takes time to build up production rate again into the month.