Measuring batches that run beyond the shift-limit

Q: When a batch is running at the moment when a new shift-crew comes in, we do not know how much volume was produced yet in that batch. How do we determine an accurate OEE now?

Batch production

  • We are running a 5 shift operation in a fixed schedule.
  • Our machine throws out product in bin’s.
  • When a bin is full, it weight is determined by placing it on a scale while a new bin is placed.
  • It takes between 30 and 90 minutes to fill a bin.
  • The maximum output is 10KG/Min
  • At the end of a shift usually a bin is still being filled and the leaving crew cannot tell yet how much output there was produced for the running bin.
  • The next shift will take this bin and weigh it.

So for a bin it might look like this:

Early shift:

Starts bin
Runs 30 min
Theoretical Output 30×10=300KG
Actual output 250 KG
Output measured 0 KG

Late shift:

Removes and weight bin
Runs 40 min
Theoretical output 40×10= 400 KG
Actual output 300 KG
Output measured 550 KG

The problem:

  • If the early shift enters 30 minutes and 0 KG, their OEE is a bit too low, which is not a real problem.
  • If the late shift enters 40 minutes and 550 KG this creates a problem, since this volume is created during 70 minutes and not in 40.
  • In 40 minutes they could have only produced 400 KG, thus 550 is not possible; it would top over the performance rate.

Of course in the long term it would -more or less- level out, since every shift loses some in the end of the shift and gains some in the beginning, but it is not accurate.

How do we measure an accurate OEE in this situation?

Arno Koch •  Whenever batch-runs exceed the shift-duration, while at that moment the volume cannot be determined, we have to stretch the definition of ‘a shift’.

In the example above, a solution could be: Defining that the last bin that has been started at the end of a shift belongs to that shift.

This means:
The new shift measures the bin, adds the volume ánd production time to the (still measuring) previous shift and now start the new shift-calculation.
The registered shift start-time ánd end-time will now usually will be a bit later than the actual start- and end-time of the crew.

Also the shift duration may now be variable, so in this case sometimes a bit less or more than 480 minutes. This is not a problem; now there will be an accurate OEE calculation per shift ánd per longer period of measured time.

See also:

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