Hi,
Sub-equipment represents a hierarchical equipment structure
if you want to represent your equipment as complex structure, the whole equipment is represented as Superior Equipment under which each individual equipments are treated as sub equipments
For example if you take an example of Crane
Whole CRANE is considered as superior equipment and under which each individual equipment such as
TRUCK, TRAILER, CRANE SYSTEM, HYDRAULIC SYSTEMS are considered as sub equipments
SUB EQUIPMENTS are always equipments which were created as master data
assign the sub-equipment in the Equipment master IE02
In case of EQUIPMENT BOM, it is material which is linked to Main equipment and the material should be created as Material master data
You can create Equipment BOM in IB01
Hope it is clear
regards,
santosh