I am very "with" resop on this.
I use excel everyday, and I use the problem solving skills I learned in school. All those math questions that were stories that you have to change into a formula?
Use it, everyday.
If a Ford plant in Canada needs 1080 luggage racks every day and the transit time is 10 hours, and they have 766 on hand, when do you need to ship more luggage racks? How many do you need to ship to cover the next trucks arrival? You have trucks every 6 hours. The last one left 2 hours ago.
1. They use roughly 45 racks per hour.
2. They are covered for 17 hours. With the intransit racks they are covered for 21 hours.
3. In 4 hours from now you need to ship 180 racks. (How do I know that - by inferring that they run 24 hours a day, with 6 truck windows, you have to be able to fit 180 pieces on a truck.)
Now, if the capacity of your line is 30 pieces per hour - you're fine, but if the tool breaks, or the cycle time drops to less than 30 pieces per hour, you're in trouble, Since you have to run 30 pieces per hour, (again by inference of 180 pieces per truck), for every 2 hours of downtime on your line you will drop the inventory at the customer by 1 1/2 hours.
Excel ain't gonna do that for you - it may do the math, but you still have to figure out how to make it work.