A simple way to understand sequencing is to think of two cars going down a single lane highway. One can go at 120 mph and the other can go at 30 mph. If we assume that they can’t overtake each other how long does it take them to drive 30 miles? Of course the answer is easy, the fast car can drive 30 miles in 15 minutes, or can it? If it is behind the slow car then it will take the same time as the slow car, which is 1 hour.
When it comes to sequencing
1 + 2 + 3 ≠ 3 + 2 + 1
This is one of the reasons that scheduling in buckets doesn’t work.
The ability to manipulate the way that operations are sequenced at a machine not only impacts setup times, it impacts on-time deliveries and work in progress (WIP).
The ability to manipulate the sequencing of orders and operations can have a significant impact on the way a plant performs. APS systems should have a number of advanced sequencing rules and the ability to create new rules to address unique requirements.
Our approach is different because putting all the variables into the mix and calculating the perfect schedule is usually unrealistic. I like to use the 80/20 Process, which says that a schedule should be automated to do all the donkey work (the 80%) but allow the scheduler to use his or her experience to fine tune the schedule (the 20%).
Schedulers, as a rule, are not stupid. In fact, because of the responsibility they have to keep things running, they are usually quite bright. Once they realize that their ERP system is not going to help them create and maintain a valid schedule, they look for an alternate solution that will prevent their life from becoming unbearable..
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