Muda, Muri, Mura


Muda means waste, and represents those processes, or activities that don’t add value to the process flow of the product.
They increase costs and make tasks take much longer than they should.
Muda is a main pillar in the JIT (Just In Time) system because waste is considered, as a huge financing cost. In the JIT system, Muda appears as overproduction, storage costs, defects.
In lean manufacturing, the first step represents identifying activities with added and no added value.
Here are the 7 Waste of MUDA:

2. Mura

Mura means unevenness (irregularity or variability). Mura is the reason for Muda (waste) because variations in the process cause waste.
On the production line, for example, parts pass through several workstations during the assembly process. The waiting time represents the time, while the product is situated within workstations or the time before, and after the process.
The waiting time is different between workstations because one of the operations is more complex, and may take longer than the other ones. Some of the stations waiting for the product, and the other ones, will be overloaded. In this case of Mura, the solution is the balance between workstations.

SPC- Process Variation

Unfortunately, in many companies, the production system is like the waiting time between stations, some of the days they produce less, and the other one too much to cover the orders.
The solution for Mura could be the average demand calculation, to achieve repetitiveness in orders. First, it needs to be specified demands for a month next for a week.
The goal is to achieve 4 days of repetitive standard orders, and 1 day could be flexible, to complete unanticipated customer orders.

3. Muri

Muri shows the overburden of people and equipment.
It can be associated with the situation when operators or machines are utilized for more than 100% to finish their task. Why are they overburden?
Muri means parts that don’t fit correctly as they were planed initially, so in this case, the operator struggling with extra work or special tools to finish the task.
Balancing manufacturing processes helps to avoid MURI.
Sometimes, overburden results from the excess elimination of Muda (waste) and using the remaining equipment, and operators for the maximum capacity.
In the scheme below, you get an idea of, how to apply these principles correctly.
First, get rid of Muri on the shop floor, then Mura to balance operations. When these two are under control, it’s time to dig in Muda, to identify the gaps.

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