3. Inventory Management – This Is What It’s All About!

This article follows on from two earlier articles on the Broken Stocks Saga, and Schedule Enablers. I would recommend reading those two articles to better understand this one.

Now to the crux of the matter, mine scheduling is primarily an inventory management process. While every mine is different and they all have their idiosyncrasies or complexities, the reality is the scheduling process and the aim of the schedule is no different between mine sites. In fact, is mine scheduling any different to scheduling a manufacturing process or anything else? Scheduling is about the quantities to be scheduled, what resources you have to schedule and their production rates, what interdependencies you have and what your schedule targets are.

So what should you focus on in your mine scheduling so as to be most effective? I believe the key objective of any activity, is to provide adequate inventory for the following activity. Don’t misunderstand me, you still need to schedule the equipment, such as drills, excavators, draglines and processing plants. You need to do this to ensure that the schedule is practical and achievable and that production targets are being met. In addition to that, a key reason you need to schedule equipment is to allow accurate inventory quantity calculations. Scheduling equipment generates the inventory for the activity that follows this equipment and also depletes inventory from the activity being scheduled.

In making decisions when scheduling, the basis for those decisions should be around what will provide the right inventory for the following process. For example, while scheduling the pre-strip in an open cut coal mine, monitor the dragline inventory and schedule the pre-strip so as to maintain dragline inventories within the target bands. But you will need to schedule the dragline, as it will deplete the dragline inventory and add to the coal uncovered inventory. Carry out that process for all scheduled mining activities on site.

Eliyahu Goldratt takes the subject of inventories a step further in his book on the Theory of Constraints. This book is called The Goal and I would highly recommend reading it.

Now of course if you’re scheduling to meet target inventory bands (and there will be both upper and lower limits), then a key question becomes what should those bands be? Stay tuned for the next article!