Lean Maintenance Calculators
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How to Evaluate Your Lean Maintenance Program



You may want to read the introduction to Lean Maintenance first.

Ongoing evaluation is important to the success of a Lean Maintenance program. Besides giving the program a cost/benefit analysis, ongoing evaluations provide the guidance for further improvements.

What to Measure in a Lean Maintenance Program

The following are useful metrics for any maintenance program, but especially useful for Lean Maintenance:

Let’s examine why these numbers are important, and their targets or trends.

Percentage of work orders for scheduled maintenance versus unscheduled repairs

 

The goal is to increase the ratio of scheduled versus unscheduled work orders, with an achievable target of 90%. Whether you make your schedule based on past repair history or, preferably, using condition-based testing, scheduling has several benefits over repairing after breakdowns:

The target is to schedule about 90% of the tasks. Many maintenance gurus estimate that even fewer breakdowns indicates that too much time and effort are being spent on maintenance.

Percentage of labour time for scheduled maintenance versus unscheduled repairs

The benefits here are the same as for the number of work orders.

The goal here is to schedule the maintenance crew to about 80% of their capacity. This leaves room for maintenance that takes a bit longer than expected, and for unscheduled repairs. Again, if less than 20% of the labour time goes into repairs, then it might be more economical to ease back on maintenance.

 

Percentage of time scheduled for the maintenance team to train operators in testing and preventative maintenance, versus time scheduled for actual maintenance

The goal is to see this number trend upward. The front-line operators should be able to do routine condition testing and routine preventative maintenance. The better they perform these functions, the more time the maintenance staff has for more complex work.

The training should include “how to write up a work order” so it communicates the situation as effectively as possible.

Percentage of monthly downtime for scheduled maintenance versus unscheduled repairs

 

Scheduled maintenance should, ideally, avoid impeding regular production. The machine itself is not available for work, but it should not be required during the maintenance period. Downtime should count only the elapsed time that this machine is unavailable.

In a Lean Manufacturing shop, where work-in-process should flow smoothly from machine to machine, an unscheduled repair could bring the entire factory to a halt. In that case, the elapsed “downtime” is multiplied by the number of other machines kept idle during the repair.

So this percentage should climb significantly and stay high.

Monthly cost of lost production due to scheduled maintenance versus unscheduled repairs

 

This metric is similar to “downtime” in the previous section. In this case, however, we measure the value that the machine(s) should have been contributing during maintenance or repair.

Of all the metrics in this article, the cost of lost production is the most important to management. If a breakdown of one machine stops the entire factory, or even a substantial fraction of it, then the cost of lost production is enormous.

 

Monthly hours or cost of downtime due to lack of required replacement parts

These situations are included in the above metrics, but breaking them out is important in managing the inventory of replacement parts. If a necessary part is out of stock when it is needed,  one or more machines will be idle. Typically the time to procure a part will be much longer than the time to install it.

The question is very important: what did it cost to be out-of-stock of a critical part?

As noted earlier, one benefit of scheduling maintenance is that the scheduler should check on the availability of the replacement parts. This can “pull” the part by initiating a purchase order. This can also put a delay into the schedule: “Do not set the date before the part has arrived”.

Monthly cost of storing replacement parts

 

This number should be balanced against the cost of keeping a machine idle because of a parts shortage. A repair-oriented shop needs to maintain a large inventory of replacement parts, since it has no way of knowing when a breakdown will occur.

A goal of Lean Maintenance is to reduce the “waste” of keeping an inventory of replacement parts. This inventory should decrease over time as parts are used, and only re-ordered in time for the next usage.

Benefits to Pursue in a Lean Maintenance Program

 

The typical goal in a maintenance program is to minimize the cost of keeping the equipment working.

You need to know and understand the costs for preventing and correcting equipment breakdowns:

When you evaluate your maintenance program, you should find that as the improved maintenance makes your factory more reliable, you are reaping these savings and benefits:

In short, when you evaluate your factory’s Lean Maintenance program, you should find that it has led to higher profits.

Oskar Olofsson, 2011

 









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I am a Swedish-based Lean consultant, and the owner of the World-Class-Manufacturing.com web site.

Contact Oskar Olofsson



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