Hello “Muda”

One of the biggest focusses of lean manufacturing is the elimination of waste or “Muda.” This was described in our previous column (Machinery & Equipment MRO, April 2004, page 41). The same principles can be applied to the maintenance department — it’s just the way the definitions are applied that is different.

In both manufacturing and maintenance, anything that does not add value to the process is considered waste.

The most common forms of waste are overproduction, inventory, poor quality, inappropriate processing, waiting, motion and transportation.

The Waste of Overproduction: In manufacturing, this has generally developed as a comfort zone to cover for rejects, downtime, absenteeism, etc. In maintenance, it often occurs as a result of following the ‘manufacturer’s recommendations.’

Over-maintained equipment is a waste. The manufacturer’s recommendations are based on typical applications in typical environments.

Unless you work in the typical plant, condition-based maintenance using technologies such as vibration and oil analysis, or history-based maintenance, are better approaches. Effective use of a computerized maintenance management system (CMMS) will help in developing this strategy.

The Waste of Inventory: In manufacturing, ‘work in progress’ or stock items occur often through PUSH (forecasting) scheduling. In maintenance, this type of waste usually refers to spares inventory.

A turnover ratio of 4:1 is considered world class. Again, condition-based or history-based maintenance allow you to keep inventory at a minimum by giving sufficient warning to allow the purchase of required spares. However, a complete analysis of spare requirements and lead times needs to be done before cutting back on inventory.

Sometimes small modifications can allow you to rationalize your spares. Last of all, partner with your suppliers; it’s surprising how much stock they will keep if you just ask.

The Waste of Poor Quality: In manufacturing, this is producing a product that doesn’t meet the customer’s specifications. In maintenance, this can be when repairs do not return the equipment to ‘as good as new’ status. The aim for all repairs should be to enable repaired equipment to resume full functionality.

Having to carry out the same repair twice is a clear indication of poor quality, though not necessarily in the performance of the work — but maybe in the strategy being used.

A worse and more common scenario is carrying out repairs to eliminate symptoms or effects. This usually results when there is no Root Cause Analysis carried out.

This analysis does not have to be a complicated set of cause and effect diagrams, but can simply be a ‘5 Why’ analysis where you question why the failure occurred and then why the possible causes occurred until you have driven down to the fifth ‘Why,’ which will usually identify the root cause.

The Waste of Inappropriate Processing: In manufacturing, this refers to modifying a part due to process or technological inadequacies. Similarly in maintenance, getting to the jobsite and finding the need to ‘fit’ a part is waste. Parts should be checked before being issued to the job and may result in a change to the specification for that part to the supplier.

Using inappropriate technology is also a waste, as is not using a bearing heater when mounting bearings, or using a straight edge and feeler gauge instead of reverse dials or laser alignment.

The Waste of Waiting: In manufacturing, this is any time the operator or machine is idle, but can also refer to when an operator is just waiting for a machine to carry out an automatic cycle. In maintenance, any time waiting for parts, either to arrive or be issued, waiting for information about the work to be carried out, or not having work scheduled, are all forms of this waste.

The goal is to have 75% of all work planned and scheduled with the correct parts issued to the jobs. A useful tool is to have a list of jobs that can be done if a machine goes down, split up into jobs that can be completed in one hour, four hours or eight hours, and prominently displayed at the machine side.

Checking in with production scheduling is another way to reduce this waste as production staff can accurately predict when machines are in changeover, cleaning or being idled for any period of time, allowing maintenance to be done. Production can also ensure that the machines you are scheduling maintenance on will, in fact, be shut down (usually).

The Waste of Motion and The Waste of Transportation: In manufacturing, this refers to unnecessary motion of the operator due to poorly designed workstations and unnecessary transportation of material, which also increases the possibility of damage.

In maintenance, it is the elimination of what is sometimes referred to as the ‘maintenance shuffle’ — getting to the job and finding a specific wrench is needed, getting it and then finding you need another sling to remove the part, etc.

A clear work order listing the tools required will control this. In larger facilities where area maintenance is used, satellite stores with parts specific for that area can also cut down this type of waste. It may also cut down the Waste of Waiting but be careful as it can very easily increase the Waste of Inventory.

Next issue, we will look at SMED (single minute exchange of dies), what it is and how it applies to maintenance.

Cliff Williams is engineering and maintenance manager at Multipak Ltd., Mississauga, Ont., and a consultant with TMS Total Maintenance Solutions of Markham, Ont. He can be reached at williamsc@sprint.ca.