Understanding the Complex Assembly Process

An end item is the final product, that is, the result of the complex assembly process. The end item is the root node of a BOM hierarchy. Customers order end items and spare parts for them.

• Key Components: End items are typically represented by multiple BOMs, comprising major assemblies that organize the assembly process. Known well in advance, these assemblies—like fuselage or wings for aircraft—enable manageable construction. This segmentation supports high-level planning, resource allocation, and early procurement, especially for parts with long lead times, like jet engines.
• Characteristics: End items differ from spare parts through their material type and typically include a consistent set of major assemblies. However, they are often customized or specially engineered to meet specific requirements. This customization is defined at the end item level using either parameter effectivity or variant configuration.

Major assemblies are the components of an end item and represent a large section of the product (for example, the major assemblies of an aircraft are the wings, center fuselage section, and so on). They often have thousands of parts. Product or design engineers design major assemblies and create engineering BOMs (EBOMs) that contain a flat list of the many components for each of them.

• Key Components: Installation kits break down major assemblies into manageable pieces. Despite their complexity, major assemblies don't typically have associated routings or production orders and aren't MRP relevant unless part of an installation kit.
• Characteristics: They are specifically engineered or configured to meet particular requirements. In aircraft production, customization is defined by model and unit, ensuring every EBOM is valid for specified models and unit ranges. Engineers maintain the completeness and consistency of components, managing dependencies like joint connections and symmetry constraints. For example, replacing a component on the left wing necessitates corresponding changes to the right wing.

installation kits simplify the construction of major assemblies, containing specific components that allow for manageable assembly tasks. A major assembly can include hundreds of installation kits, each focusing on a particular segment like the wing skeleton or fuel system in aircraft. Kits are designed for assembly by qualified operators in a designated area.

• Key Components: Production engineers shift components from an engineering BOM (EBOM) to a manufacturing BOM (MBOM) for major assemblies. Within the MBOM, components are grouped into installation kits, organizing subsets of parts for cohesive assembly processes. Each kit has a dedicated routing that outlines how components are assembled into the major assembly, creating an installation order to guide production operators.
• Characteristics: Installation kits, treated as artificial materials, provide an organizational framework in SAP S/4HANA PEO. They facilitate the division of large BOMs into manageable sections, are MRP relevant, and enable the creation of MBOMs, routings, and production orders. Unlike engineering materials, installation kits are not intended for storage.

Installation kits can contain raw materials and inventory-managed subassemblies, which are either procured to stock, made to stock, or made to project. They are issued from inventory by the installation kit’s production orders.

Raw materials are procured using the regular SAP S/4HANA purchasing processes. The inventory-managed subassemblies can be manufactured using either the regular SAP S/4HANA manufacturing processes or SAP S/4HANA PEO.

The following example illustrates how a major assembly can be sliced down into manageable pieces (installation kits).

Assembly of the right wing (or any other major assembly) must be divided into manageable tasks such as assembling the frame (white parts), the hinges for the flaps (orange parts), the electronics (blue, green, and red parts) and the hydraulic system (brown parts). These colored parts are the components of the different installation kits.

The installation kits shown above (hydraulic system and electronics) have to be assembled into an existing frame. They are not a typical subassembly that can be manufactured, put into a warehouse, and issued when needed.

Installation kits can be defined in the Visual Enterprise Manufacturing Planner during EBOM to MBOM handover.