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Activities in Availability

What is ‘Availability’

The availability of the machine is linked to the question: is the machine operating or not?

The definition of ‘operating’ is: the machine has output, regardless the amount or quality of the output. After measuring the time during which the machine was not producing, the availability rate is calculated by dividing the running time with the loading time (the time the machine was scheduled to operate. Some use the term shift-time). 

The ‘Ideal’ machine versus reality

In case of the ideal machine, with an availability rate of 100%, the running time and the loading time are equal.

This would be a hypothetical situation, rarely met. It is used as reference point.

In practice, machines are not running all the time. We would like to know if it makes optimal use of the available production time.

Therefore, the actual situation is referred to the ideal situation. This will visualize time losses occurring due to failures, changeovers and other waiting of the machine. During this time no value can be added to produce marketable products and thus no money can be earned, while costs continue.

What is an Activity

Theoretically every day in the life of a machine could be sliced in parts of time, identifying what was happening: an activity.

Even if nothing was happening this still would be an activity to the machine: it is waiting.

An activity therefore is a predefined time usage. Every activity belongs to a category: It is either Production time, waiting, failure, line-restraint or unscheduled (see: II  6.1.0 Five categories of Activity: [P],[W],[L],[F] & [U]). The instructions below will assist you with entering the Activities while configuring your OEE Coach software.

Activity Master-table

All activities that may occur for each machine, will be pre-defined in a master-table. If activities can occur on more than one machine, you need to enter that activity only once into the master-table Activities. Changing a name here will result in a changed name anywhere where this activity was used.

The objective of defining the parameters for availability is to identify ALL the Activities of the machine. By documenting the various types of Activity of the machine, the OEE-calculation will reveal how the machine uses its available time to manufacture products, but in particular, where time is lost. With this information the biggest time losses can be found and eliminated, thereby increasing the availability rate of the machine.

Perspective of formulating Activities

The perspective for defining the availability rate parameters (and the other parameters) is the machine:

OEE deals primarily with MACHINE effectiveness, not the effectiveness of a TEAM or even the effectiveness of the OPERATOR (although these are, of course, strongly interconnected).

To make the job of defining parameters easier, it is best to try to identify yourself with the machine and ask the question:

I am the machine. What is happening to me?

This makes it easier to think process-oriented and not to lapse into questions of “Whose fault is it” (“It’s the fault of department X!”).

Which losses should be measured?

Operators do not always have immediate influence on losses. However, many losses which are caused or can be influenced by the organization do become evident on the shop floor. Therefore, measure all losses and make them evident to the entire organization. After all, those losses are the problem of the entire organization!

How many Activities to be defined

Keep things simple! Limit the number of different activities to a maximum of 10 to 15 items. Do not add every possible Activity of the machine to the list. At this moment this might be very tempting, but over the years where you register and follow OEE, it is not going to help.

Do not forget that the activities now defined, will remain permanently and that the operator has to search and click over and over in this list!

Hopefully, some of the incidents that are occurring frequently NOW, will no longer occur in the future!

When defining and registering too many activities, a Pareto-diagram will flatten out, preventing clear insight in the biggest problems.

Questions you must ask

Examples of questions that play a role in the availability rate are:

  • Why does the machine not make any products?
  • Is the machine out of order? Is there no need for production?
  • Is a changeover taking place? Is it waiting for input or getting rid of its output?

When using the OEE Industry Standard, the time categories defined there could act as your guideline: ask yourselves from every category how this might occur on your machine.

Situation Diagram

Using the Correct nomenclature

Make sure that you define the type of failure/breakdown in such a way that it is identifiable or can be observed; in other words, you record the phenomenon,not the cause! After all, it is rarely the case that a failure has only one cause. At the moment a stoppage occurs, it is by no means always clear what caused it. If you include in your definition that beforehand a technical expert or a production process expert must be consulted every time before the correct failure can be determined, the OEE-measurement will have lost some of its value as an instrument to improve things on the shop floor. Preferably, do not measure ‘electrical failure’ or ‘mechanical failure’, but rather ‘failure conveyor’, ‘failure labeling machine’, etc.

Have all activities been documented?

The last check to see whether all time uses have been described is the question: If I stand next to the machine, can I, the operator, rank any stoppage (longer than the threshold) under one of the defined activities?

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