09. May. 2018

Muda, Mura, Muri

by Joel Bradbury

You can’t eliminate waste unless you also deal with two other process concerns

One of the most important goals of Lean manufacturing is the elimination of waste. Taiichi Ohno, father of the Toyota Production System (TPS), defined three categories of waste: mura, muri, and muda. While Muda is the most widely known, muri and mura are equally important to understand.

Muda

Muda refers to processes or activities that don’t add value. These types of waste do not help your business or workers in any way. They increase costs and make tasks take much longer than they should. Wastes are defined in TPS as follows:

• Overproduction occurs when items are manufactured before they are required.

• Overprocessing occurs when more work is put into a product or service than is actually required.

• Inventory is important, but storing too many or too few supplies and finished goods increases costs and can take valuable space.

• Transportation is the movement of products and supplies from one area to another.

• Motion is the physical movement of a person or machine required to complete work.

• Waiting is when work or projects come to a halt or slow because machines have yet to finish producing the required goods, products have not arrived, or some other task is holding up the rest of the project.

• Defects occur when errors and rework are created because of your processes.

Finding and eliminating Muda is essential if you want to reduce costs, improve efficiency, and increase profits. However, if you don’t also address mura and muri, these benefits will be inconsistent or may even fade over time.

Mura

Mura is a type of waste caused by unevenness in production and services. It is also caused when standards are nonexistent or are not followed. One common example is when companies ramp up production to meet targets, even when there is no customer demand. This forces the sales department to rush to try to fill orders and creates a burden as the shipping department rushes to ship products before the end of the month.

The result? Defects are manufactured into products. Customers receive inconsistent products or services. The production floor struggles to complete large orders and becomes idle as orders slow. Even more concerning is that mura creates muri (overburden), which in turn undermines efforts to eliminate the seven wastes of muda.

Muri

The third category of waste is the result of tasks or processes that are overly difficult, or ones that overburden workers. For the most part, this is caused when workers:

• Lack proper training

• Have no standards to follow

• Are given the wrong tools for the job

When workers lack the right tools for the job, for example, tasks become much more difficult, taking more time and potentially damaging the product. For instance, working sheet metal with the wrong hammer and dolly will damage the panel you are working on—tripling the time it takes to complete the task and requiring products to be reworked.

In the same manner, using your email inbox to manage the tasks you must complete makes the tasks more difficult than they should be. Keeping emails to remind you of tasks to complete causes hundreds, if not thousands of emails to accumulate. As a result, it takes too long to find important information and may cause you to overlook important information, potentially causing projects to fall behind schedule or causing others to stop their work as they wait for a response.

Muda Mura Muri

Here, floor marking helps keep the area organized, and the shadow board helps workers quickly identify where tools belong

Eliminating Muda, mura, and muri

The purpose of Lean manufacturing is to find and eliminate Muda, mura, and muri, in order to improve quality, safety, and efficiency. One Lean tool that can help you eliminate these forms of waste is the 5S system. 5S helps to declutter, clean, and organize the workplace using the five “S” principles: sort, set in order, shine, standardize, and sustain.

Sort is the first step in 5S. During this phase, you remove tools, supplies, and equipment that are not part of the work process. This declutters the workplace, freeing up space that was previously ill-used.

Set in order is the next step, requiring you to organize the workplace and everything in it to improve the flow of work, based on how work is actually done.

Shine, the third step, requires you to clean the workplace and restore everything to its original condition. This makes it easier to spot equipment and product defects that may have otherwise been hidden.

Standardize, the fourth step, requires you to develop rules that will ensure work is completed consistently and that 5S is applied uniformly and regularly.

Sustain is the final step of 5S. It requires that you work to ensure that 5S becomes a daily habit.

This article first appeared online on May 11, 2016, at Quality Digest, a Kaizen Institute Online partner.

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