Blanket Purchase Orders - Multiple Parts with Changing Mix

Hi All,

I was wondering how others handle this type of situation. We purchase a lot of sheet steel in different sizes. We regularly write a purchase order for a set number of pounds that are to be delivered in many releases over say 3 months. We do not know the sizes we will ask for until a week or two before each specific release as they will cut the length of the sheet to our desired size(s). We have a different part for every sheet size, e.g., 7GA x 72"W x 120"L is a part, 144"L is a part, etc.

We could use our best guess on the distribution of sizes and then adjust the qty towards the end of the PO, but this gets really messy real quick and leaves me feeling a little uneasy.

This has to be relatively common I would think. How do others handle something like this?