Co Parts not driving requirements correctly

We have a purchased part (123) that will be cut into 8 pieces that should be turned into qty (4) of Part (456) and qty (4) of Part (789). We have tried unsuccessfully to engineer correctly using co-parts. We are driving requirements to purchase too many of part 123 or not enough. Any suggestions on the best method to set up part 456 & 789?

So just so I understand

You have a purchased part123 that will be bought to stock
, then you have a manufacturing job that will take this raw material and make a 4 off and a 4 off?

Correct…part number 123 is purchased. Qty (1) of PN 123 gets cut into qty (4) pcs of 456 and qty (4) 789.


so 789 is a co part of 456 and ignore MRP suggestions is ticked for the co-part?