Selecting a Distribution for the Processing Time

We will now change the processing time of the Station Testing from the default time of 1 minute to a mathematical distribution, let’s say the Normal distribution. This way the processing time for each part will be based on a random number according to the Normal distribution.

• Open the dialog window of the Station Testing and click the tab Times.

• Select Normal from the drop-down list Processing time.

• Change the parameters to 0:55, 0:05, 0:01, 1:30.

Plant Simulation shows the parameters, which this distribution requires, above the text box.

In Plant Simulation we separate seconds from minutes with a colon (:). So 1:30 stands for 1 minute and 30 seconds.

The processing time for the station Testing now follows the Normal distribution with a mean value of 55 seconds and a standard deviation of 5 seconds.

Next, we’ll select a distribution in the Source according to which it produces parts.

• Open the dialog window of the Source.

• Change the Interval to Negexp on the tab Attributes.

• Type in a distribution time of 1:00.

Run the simulation again. You will notice that the parts sometimes have a yellow border around them. This shows that the parts are blocked, i.e., they cannot move on to the next object because it is still occupied by the preceding part. We need to solve this issue.