In light manufacturing systems, it is a common practice to “flatten” BOMs so that multiple levels can be represented within a single parent item. This creates “super jobs” where the entire component structure can be backflushed at job finish in a single transaction.
In general, avoid creating super jobs using phantom assemblies, which is counter-productive to the routing architecture that distinguishes DBA from light manufacturing systems. Routings enable each assembly in the product structure to be defined with its own processes and materials in its own BOM. Separate BOMs enable jobs to be released to production in the correct order of assembly and for job sequences to be listed in work centers in correct processing order.
Avoid substituting phantom assemblies for subassemblies. The use of phantom assemblies should be limited to representing product options with custom manufacturing. A phantom assembly does not have a routing and can never be made on its own job or be stocked, which eliminates any possibility of using forecast and supply days planning, and they cannot be released to production in the correct order of multi-level assembly.
The only instance where a super job achieved with phantom assemblies might make sense is when both of these conditions are met:
- The entire product structure is made in a single chain where subassemblies have no interdependent demand with other jobs.
- The entire product structure is essentially all made at once with no staggering of start dates among its subassemblies.
Very few products meet both of these conditions, so in most cases you will avoid super jobs and use subassemblies to take full advantage of the time-phased nature of MRP and shop control.