Simulates a machine operating on a single item for a specified processing or delay time. When the machine is ready, it pulls an item from a resource or operation (buffer, conveyor, transporter, batch, and so on) and processes it for the time specified. Once an item is processed, it is held until it is picked up by another block. The machine is only ready to process the next incoming item when the processed item is taken by another block.
The process time may be the constant number provided in the dialog or the value at D when the item is received. The D connector overrides the dialog value and allows you to set a variable processing time based on the manufacturing environment.
Setting the down connector to a non-zero value causes this block to be shut down. You would use this feature when an external event such as a power failure occurs; it is common to use the Schedule block or the Generator block from the Discrete Event library for this. You can specify in the dialog that the down value should be interpreted as the duration of the downtime, or that the machine is shut down until the down connector value returns to 0. After a shut down the machine ignores all further shutdown messages until it is in operation again.
You also can specify that an item in the machine be thrown away if the machine goes down while the item is in the machine (such as when parts are spoiled by the machine going down).
Dialog Choices
Arrivals: Number of items that have entered the block.
Boolean T connector: If selected, sets the t connector to report a 1 when the machine is in use and a 0 when it is not. If it is not selected, the t connector will report the amount of time since the last event, at each event when the block is active.
Departures: Number of items that have left the block.
Processing time: Number of time units an item must stay in the machine before it is released. This is overridden by the D connector.
shut down while “down” connector value > 0.5: Uses the value at the down connector as a threshold. Whenever the value is greater than 0.5, the machine is shut down.
Throw away item when shutdown occurs: If selected, the item being worked on is discarded when the down time is over. This is useful when the down time results from a breakage. Otherwise, when the machine starts up, it just continues working on the existing part.
use “down” connector value as duration: Takes the value at the down connector as the duration of the down time.
Utilization: The percentage of time the block was in use over the course of the simulation run.
Utilize blocking: Determines if blocked delay time is added to the utilization information or not. If this checkbox is checked, utilization information will include blocking.
Utilize down time: Determines if down time delay time is added to the utilization information or not. If this checkbox is checked, utilization information will include down time delay.
Connectors
The input is items to be processed.
The output is the items after processing.
D: Delay time. Time the item is processed in the machine. This overrides the option in the dialog.
down: Allows an external event to shut down the machine.
S: Shutdown. Puts out a 1 while the machine is shut down and a 0 when it is not shut down. If you plot this, you can see both the time when the machine shuts down and the duration of the downtime.
T: Time in use. Puts out a non-zero value while the block is in use. This value represents the amount of time since the last event, at each event when the block is active. You can connect it to an Accumulate block to find the total time in use during the simulation. If the "Boolean T Connector" check box is selected, the T connector will continuously output a 1 when the machine is in use and a 0 when it is not. This is useful for determining whether or not a machine is currently operating. Note that when a machine is down, it is not in use and the T connector outputs zero.
U: Utilization. The percentage of time the block was in use over the course of the simulation run. The total time that items were in the block is used in the calculation, including delay times and times while items were blocked (when items were finished processing but remained in the block because the next block was not ready to pull them). Note that when a machine is down, it is not being utilized and the utilization will decrease.
Animation
A green circle appears in the middle of the block as long as an item is being delayed. This circle turns red if the item is ready to leave the block, and its path is blocked. Another blue one appears when the machine is down.
