In one project, we handled this problem by setting up Bills of Materials that listed groups of materials where the manufactured product needed one material selected from each group. Thus, alternate but acceptible materials were listed in the BOM but only one specific material from each such group was selected for a given manufacturing run.
an Example BOM might look like this:
AltFlag MaterialID MaterialDesc UsageQty EffDate1 EffDate2
C1234 BLk-3001 metal 15lbs/Case 9/1/09 9/7/09
x C2345 BLK-3000 metal 15lbs/Case 10/1/09 10/7/09
C4598 Trifoil Foam liner 1lbs/Case 1/1/07 12/31/50
The second item on the list would be a different but acceptable material to use in place of the first item. The effective date fields were then used to control which materials were used for a given run.
In your case, I'd give the new material it's own ID and use a similar method to use it as a "subsitute" material.
That's a good idea that we are considering, and I'm hoping for a better one...
The reason to keep looking is that it may only be this one lot of GlassA that meets the GlassA_milled spec. The past lots have not, and I have no certainty that the next one will.
If I change the BOM to allow the use of GlassA_milled, and the next lot doesn't meet the GlassA_milled spec, then I run the risk of making out of spec final product. We do have other products that can tolerate either one, and the BOM for those already cross-references as you suggest. That works well when either Glass can make in-spec finished goods.
Another stress-riser is that we have about 175 BOM's that use GlassA, and another 130 BOM's that use GlassA_milled. Its a lot of changing to do (that system is still on paper with 6 approvals required per changed BOM...I haven't gotten the go ahead to pull that one onto the computer yet.) That said, reason#1 is still my biggest pause...a batch error costs wayyyy too much to increase the risk.
Please continue with ideas as available...I'll be hashing this out with the stockroom controller for a while until we find a low risk, 'relatively' low labor way to work it through. In the mean time, it's Flagged on the electronic weight sheet to do a manual reallocation for this lot only from one weight sheet to the corresponding material's weight sheet as needed. This keeps the batching risk low, and still allows for the manual double and triple checks by the floor technicians, but the MatManagement function is reporting errant info. Any additional thoughts and ideas are very much appreciated.