I think you will find Lots is the simplest way to model this. You can create a parent lot for the material as it comes in, then child lots linked to that (by convention) for the cuts and allocations made. So a Job to cut bar stock would produce two separate lots. A Simple customization could automate the cut operation handling as a kind of Kanban type operation driven off the demands needed on the job materials. The Lots then give you the ability to track inventory to this level - purchase suggestions needs to take into account usable lots so you may have some rules as to when you change the part number based on usable size / planning needed. Hope that helps
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