Produccion

Finite Scheduling: Its Advantages and Pitfalls
Finite scheduling is especially useful in simulating short-term schedules.
To use finite scheduling effectively requires three key elements:understand finite scheduling, we need to start with the standard backward scheduling logic found in most MRP (Material Requirements Planning) systems.
The backward scheduling logic simply takes the order duedate from MRP and starts subtracting the day or fractions of a day from the order due date. The setup and run (S&R) times are extracted from the routing file. The setup time is taken as is andthe run time is multiplied by the order quantity. The pull, move (M), queue (Q), and stock times are taken from the work center file or other appropriate files in the system.
If the pull, move, queue,setup, run and stock times are the number of days indicated under each element, then we can backward schedule and arrive at the operation start and complete dates.
The calculations above are based onsimple logic, but the logic makes some assumptions that likely will not be true. The assumptions that frequently aren’t true are that the queue is fixed, the setup time is consistent, the move timeis consistent, the pull time is consistent, and the stock time is consistent.
Lead Time Assumptions:
Making this faulty assumption can be avoided by simulating the actual jobs schedule through thework center and actually calculating the amount of queue that will be in front of the work center when a specific job is scheduling software has this simulation capability.
Another large piece of leadtime is moved. It is often assumed the moved time would be the same for all work centers. Putting in the actual time it takes to moved between different work centers better simulates what is actuallygoing to happen and will result in more accurate schedules.
A third frequent assumption is that the set-up time will always be the same. This simply is not true. To more accurately predict setup...