Page 441 - ExtendSim User Guide
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Delaying Flow 415
Convey Flow block
could accumulate or “pile up” along the length of the block any time the amount of flow ready to exit the block exceeds downstream demand.
The Convey Flow block has three options controlling how or if flow is allowed to accumulate:
• Accumulate-maximumdensity.Allowsflowtoaccumulateuptoitsmaximumdensityset- ting. If the conveyor's ability to deliver flow exceeds downstream demand, any flow delayed from exiting will begin piling up at the outflow end of the conveyor up to the maximum den- sity level.
• Accumulate-fillemptysegments.Allowsflowtofillinanyemptysegmentsalongthecon- veyor when the block’s ability to deliver flow exceeds downstream demand. (An empty seg- ment is an area along the block’s length that has a density of 0.) This differs from the first option in that one section of flow is not allowed to pile onto another section of flow.
• Non-accumulating.Thisoptiondoesnotallowflowtoaccumulate.Therefore,theblock’s speed slows when its ability to deliver flow exceeds downstream demand.
☞ The Compare Convey Flow model compares the behavior of three Convey Flow blocks, each set to one of these behaviors, under different emptying rates.
Constraining rates
Critical constraints define an unconditional maximum upper bound to the rate of flow. As dis- cussed in the chapter “Rates, Constraints, and Movement”, the Convey Flow block calculates critical constraints for its inflow and outflow connectors separately. The critical constraints are derived from model conditions and settings in the dialog.
• The critical constraint for the Convey Flow block’s inflow is calculated by multiplying the block’s effective speed by its maximum density entry.
☞ The effective speed can be less than or equal to the speed set in the dialog. If the block is non- accumulating, or if it is accumulating but cannot accumulate more, and the block’s ability to deliver flow exceeds downstream demand, the effective speed will be lower than the entered speed.
• Thecriticalconstraintfortheblock’soutflowistheresultofthemultiplicationoftheblock’s speed setting by the density of flow present at the outflow end of the block.
Convey Flow information
The Convey Flow block provides different types of information concerning the distribution of flow along the length of its conveyor. Some of the information is provided by default while other mechanisms for reporting data, like sensors and indicators, must be customized through the block's dialog.
Discrete Rate

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