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2.6 Waiting Time while [Unscheduled]

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2.6.1 Definition
Waiting Time registered as [Unscheduled]: Activities that normally would have been performed during loading time, can sometimes be scheduled outside loading time.
  • In a two-shift operation, the machine might be setup or cleaned during the night or in the weekend, in absence of the regular crew.
  • Preventive Maintenance could be carried out at a moment no production was scheduled. In a 3 shift operation from Monday to Friday, the PM could be scheduled in the weekend, thus not affecting the loading time.
In this way OEE may be increased by using non-loading time for activities that normally would affect loading time.
Doing so has some serious disadvantages:
  • The activity is necessary to perform the scheduled production; thus cannot be skipped. This means the OEE is artificially high. When Loading Time needs to be extended (e.g. more capacity is needed) and 2 shift becomes 3 shift, or 3 becomes 5 shift, those activities automatically will fall into the loading time, thus dropping the OEE to its real value!
  • Usually, outside the loading time, there is no pressure to get the machine up and running; this might result in a less effective performance of the activity scheduled outside of the loading time.
  • The effect of these activities on the OEE (“by doing more PM, less failures occur”) is not clear.
It is advised to register ALL machine related activities, necessary to perform the operation, as WITHIN loading time, regardless of the normal shift-time. Thus PM on Saturday would be Waiting Time and decreases the OEE!
However, if you choose not to do so, make sure to register ALL the time the machine is being touched or activated outside normal loading time. In this way the potential loss can be identified and made visible.
2.6.2 Categories Idle Time registered as Unscheduled
No Time Usage Max. recommended Time Type
70 Preventive Maintenance outside Loading Time 2 P F I L -
  • Planned PM Outside Loading Time
  • (Annual) Overhaul
PM necessary to maintain a high availability of the equipment, being performed outside of the normal Loading Time. In a 3 shift operation from Monday to Friday, the PM could be scheduled in the weekend, thus not affecting the regular loading time.
Overhaul is a specific form of preventive maintenance. If the machine is unscheduled for a longer period of time to be completely overhauled, it should be considered [PM during loading time] thus (I)dle. Only if the overhaul is performed at a moment the equipment would anyway not be running (e.g. because the facility is closed) it belongs in this block. If it is done in a period where there are no orders, [No Orders] is the reason for stopping the machine, and not the overhaul. Thus [No Orders] is registered! To identify PM during No Orders, make a separate category: [PM during No Orders].
  • Unplanned PM Outside Loading Time
PM during loading time can take longer than originally planned, and continues outside loading time; this can be made visible here. If [PM in Loading Time] takes more time than planned and is being continued outside Loading Time it becomes [Unplanned PM Outside Loading Time].
71 Activities performed outside Loading Time 3 P F I L -
  • Cleaning Outside Loading Time
  • Setup Outside Loading Time
  • Loading Outside Loading Time
Activities that normally would have been performed during loading time, are now performed outside loading time. In a two-shift operation, the machine might be setup or cleaned during the night or in the weekend, in absence of the regular crew.
2.6.3 Principle
OEE visualizes ALL potential losses, even when they are clever or ‘cheap’ organized!
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