The batching tab allows you to hold entities in queue until a specified quantity is reached. For example, parts might be held in front of a heat treating oven until a specified quantity is reached. The group of part is moved into the oven and the entire batch is heat treated for a specific time. The batch is then moved out of the oven. This batching is performed to increase the efficiency of an expensive resource allowing it cycle only when it has a full load.
When the batch is created in the input queue, one entity is moved into the capacity for processing (the batch). The processing time will be for the batch. If the batch is created in the output queue, then the routing time will be for one entity (again the batch).
A basic explanation of how ProcessModel works may prove helpful. When the batch quantity is reached, all entities are then attached to a new entity (the batch). You may change graphics, set attributes, accumulate cost and assign resources to the new entity. Recognize you are making assignments to the new entity. If the batch is unbatched, the batch entity goes away and the attached entities are removed from the batch and continue on. VA Time accumulated as a batch will be divided among the unbatched entities. Cost added to the batch will also divide to the unbatched entities.
If a resource is assigned (Get) to an entity prior batching, the resource will be trapped in the batch. If you have less resources than the quantity of the batch, the models will be unable to process the request to get the next resource and entities will stop at the Get statement. If a resource is assigned to a batch and is unbatched before the resource is released (Free), the resource will be transferred to the first exiting entity from the batch.
When and unbatch occurs, entities will exit the batch in the same order as they entered the batch.
A batch can consist of other batches. When unbatching, only one level of batch is unbatched at a time.
It is possible to accomplish many other types of batching. For example you could
- Batch at the end of a shift regardless of quantity – see the model object “short batches”
- Batch all waiting entities – see the model object “all waiting entities at a specific time”
- Produce separate batches for different entities — see the model object “group similar entity types”
- Batch based on multiple criteria — see the model object “smaller quantity because the batch was open too long”
The batch will assume the name of the last entity entering the batch. For example, if you had Car and Truck entities being batched together, and Truck was the last entity to enter the batch, then the batch name would be Truck, regardless of how many of each entity type were contained within the batch. The batched entity name ‘Truck’ can not be change with the ‘New name’ property in the properties dialog.
Attaching is just creating a batch. So if a batch was -not- created after an attach operation, and you then unbatch, the attached child entities will be detached. However, unbatching should not be used as a detaching method because of the following; When forming a batch, a temporary entity is created and the batching entities grouped together with it. When you unbatch, that temporary entity is destroyed. Therefore, if you unbatch a group of “attached” entities, the parent entity will be destroyed and the child entities will detach and move downstream in the model.
Before Activity
• None No batching occurs before the activity. (No Batch Size field appears.)
• Batch The activity will batch or group incoming entities (whether or not the entities have already been batched) and process them as a batch. The number batched is defined by the Batch Size field.
An input queue with a capacity that meets or exceeds the maximum batch size is required.
An Attribute may be used in the Batch Size field to set the number to be batched. The specified batch quantity is evaluated each time an entity is batched. If the entity attribute is less than or equal to the number already waiting to be batched, the batch is formed (with possibly a new size) and released for processing. This allows the specified batch quantity to vary if desirable. It also allows for the creation of short batches.
• Unbatch The activity unbatches or ungroups the incoming entity (if the entity has not been batched, the unbatching is ignored) and processes each entity individually.
• Rebatch The activity will batch or group the same number of entities back together that were unbatched previously. This means you don’t have to know how many entities were previously unbatched in order to rebatch them—no batch size is required.
An input queue with a capacity that meets or exceeds the maximum batch size is required.
After Activity
• None No batching occurs after the activity. (No Batch Size field appears.)
• Batch The activity will batch or group entities (whether or not the entities have already been batched) after the activity has completed processing. The number batched is defined by the Batch Size field.
An output queue with a capacity that meets or exceeds the maximum batch size is required.
• Unbatch The activity unbatches or ungroups entities after the activity has completed processing. If the entity has not been batched, the unbatching is ignored. No output queue capacity is required, but without sufficient capacity downstream, processing could be delayed while the unbatching occurs.
• Rebatch The activity will batch or group the same number of entities back together that were unbatched previously or arrived in quantities greater than one (in which case the quantity batched is the quantity of the arrival). This means you don’t have to know how many entities were previously unbatched in order to rebatch them—no batch size is required.
An output queue with a capacity that meets or exceeds the maximum batch size is required.
Batch Size Determines the number of entities to be included in each batch. (Used only when batching entities.) An Attribute may be used in the Batch Size field to set the number to be batched. The specified batch quantity is evaluated each time an entity is batched. If the entity attribute is less than or equal to the number already waiting to be batched, then batch is formed (with possibly a new size) and released for processing. This allows the specified batch quantity to vary if desirable. It also allows for the creation of “short batches,” or batches that formed early before the normal size is achieved.
Before using batching, consider that your batch may just as easily be modeled as a single entity (see Job Shop Scheduling 
). Also, remember that batching may require an input queue or output queue. Follow the directions on the properties dialog. If a queue is needed, make sure it has sufficient capacity to hold an equal or greater number of entities than the expected maximum batch size. Also note that all batches or groups are unbatched when the batched entity exits the model in order to complete statistics collection on each entity. However, if a batch or group has had an entity attached to it during the simulation, ProcessModel will not unbatch that particular batch (or any groups within that batch).
Variable Batch Size
Existing “in process” batch sizes change when variable batch sizes change.
First some definitions. A batch is a group of items that will be processed at one time. In ProcessModel when a number is entered into the Batch Size field, all processing at that activity will stop until the batch size is met. That means that a batch could wait for hour or even days for the batch to reach the specified size. Changing the batch sizes allows the modeler to have control over what to do if the batch size isn’t met and yet the batch still needs to close. For example: at Quest Diagnostics human samples are processed within predefined response times. The economic order size is to process 24 at one time , but when the end of the day arrives and the economic order quantity has not been reached, the order must still be closed even if there is only one specimen in the batch. These undersized batches are called Short Batches.
An entity needs to enter the batching location to trigger the review of the batch size. In other words you can’t cause the release of a batch by simply changing a variable, but the next entity to enter will cause the review of the batch size.
The entities waiting to be batched don’t know anything about the batch size value. They are always released into the batch when the number of waiting entities equals or is greater than the “current” batch size.
For example, suppose your initial batch size is 10 and you have 5 entities waiting to be batched. Then your batch size changes to 6 AND a new entity enters the batching activity. Those 5 waiting entities will be released into the batch as soon as one more entity arrives. They will not wait for a batch quantity of 10.
When Variable Batch Sizes Change
Sometimes a batch size is controlled by an attribute on the entity arriving at the batching location and other times by a variable. Use the method that best suites your needs. See the model object Batching \ Short Batches for an example of how to change the batch size.
What is Action Logic?
What is Activity Cost?
What is an Activity Shift?
What is an Activity Submodel?