One Operator Manning Two Processors
In this video, we’re going to model the following scenario: we have one operator that runs two processors. We need this operator to move efficiently back and forth between them, processing several items at one processor before moving over to the next.
We’ll begin by creating our model in FlexSim. We will need a source, which will produce the items in our system; two queue objects, where items will queue before they enter the processors; two processor objects, which the operator will use to process the items; one operator; and a sink, which will allow our items to leave the system.
The last step is to connect our objects. Objects can be connected in one of two ways: by clicking the Connect Objects button on the toolbar, left-clicking with the mouse to connect the objects, and then pressing the Escape key to leave connection mode; or by holding the “A” key and left-clicking to connect. Using your preferred method, start with the source and connect each item downstream toward the sink, except for the operator. We will also need one center port connection, a reference connection that can be made by holding the “S” key or by choosing Connect Center Ports by clicking the arrow next to the Connect Objects button. Choose your preferred method and make center port connections between the operator and each of the processors.
Now that our model is ready, we need to adjust a few parameters to replicate the conditions we’re discussing. Double-click on the first processor to bring up its properties window. We want the operator involved in processing our items, so check the Use Operator for Process box. Click OK to save and close the window.
Next, double-click on the second processor, check the Use Operator for Process box as we did before, but this time click the drop-down menu next to Preemption and select “preempt only”. The default option, “no preempt,” means the processor will not be preempting any activities. By choosing “preempt only” for the second processor, we’re allowing it to preempt the first processor, completing its tasks before allowing the operator to resume other duties; this will become important later. Click OK to save and close.
Finally, we need to set up batching sizes for our queues. Double-click the first queue to open its properties window. Check the box next to Perform Batching and type in “5” for the Target Batch Size. This will force the queue to batch five items before sending them through to the next processor. Then check the box next to “Flush contents between batches.” This will force the entire batch to leave the queue, or flush, before any new items can be brought in. Open the properties window of the second queue and enter in the exact same parameters.
Let’s click reset and run the model. Boxes will be created by the source and will start to enter the first queue. Once five items are in the queue, the operator will walk over and help to process the items; each processed item will move on to the next queue, which begins to batch its own group of five items. Once this is done, the operator will move to the other processor and process the same five items a second time before they leave the system through the sink. Note that even if the first queue batches another five items before the operator finishes at the second processor, he won’t leave his post until the current batch is finished. This is because we set the second processor to preempt other activities.
Thank you for watching. For more information on FlexSim products or to view more tips and tricks for successful modeling, visit www.flexsim.com.