Position Parts
The concept of position parts is used within Complex Assembly MRO (CAMRO). This functionality enables you to handle the maintenance, repair and overhaul (MRO) of objects that consist of complex structures, e.g. aircraft or locomotive engines.
The actual components of an overhaul objects disassembly, disposition and assembly structures cannot be determined in advance. Therefore, based on the concept that maintenance is a function of a part's position in the structure, disassembly, disposition and assembly structures are initially created using position parts that serve as placeholders for the actual parts, when found. The concept of position parts is described in detail below.
Positional maintenance
If the same part appears more than once in the structure of an overhaul object, it is possible that the part requires different maintenance depending on its position in the structure. For instance, the wear and tear of automotive tires which are mounted on wheels connected to a drive shaft occurs at a different rate to the wearing away of automotive tires that do not have such a connection. Similarly the inboard engine on an aircraft wears at a different rate and requires service less often than the outboard engine. You can separate engineering parts using its position in a serial structure. This allows you to assign different maintenance or modifications to the same part based on its structure position.
Uncertainty of disassembly, disposition and assembly structures and routings
When defining the template structure for an overhaul object, you can specify a set of valid engineering parts, i.e., the prime part and any positional alternates, for a part in a position in the template. For instance, assume that a certain engine model always contains a fuel injection system; there are several different makes and models of fuel injection systems that can be used interchangeably. Observe the following example:
Engine A (overhaul object) contains the prime part XX (fuel system 000) in position 123. Part XX has the Parts YY (fuel system 001) and ZZ (fuel system 002) as its positional alternates which are also placed in position 123.
The exact make and model of the fuel system, as described in the above example, will not be known for certain until the engine is disassembled to a given maintenance level and the fuel injection system examined during maintenance. Even if records of the as-built and/or as-maintained serial structure for engine A exists, the actual serial structure may be different as a result of undocumented maintenance, field repairs etc. Therefore, it is only at disassembly that the actual serial structure is determined. Similarly, it will not be possible to accurately forecast which components are to be used when assembling the overhaul object once its maintenance is completed. Even if the as-built and/or as-maintained serial structures are accurate, it will not be possible to identify which parts to re-use, which to replace and what the replacements will be prior to disassembly and repair of the overhaul object.
To address these uncertainties, position parts are used. Here, the position part operates as a placeholder for the set of parts (i.e., the prime part and any positional alternates) that are valid for a particular position in the structure.
Defining template structures which are to be transferred to manufacturing
To transfer a template structure to a product structure in manufacturing and thereby create unique position parts;
- each template structure entry must have a unique Catalog Number
- the template structure must be in the Active status
- If the catalog number of a prime part and alternate part is the same, the structure position of these two parts must also be the same to be able to locate the alternate in the serial structure. Observe the following example:
Bx is an alternate part for B which is located in part A's template structure. In B's structure, the structure position for part D is 2 and the catalog number is CN 20. In Bx's structure, part E has the same catalog number as part D, CN 20. Therefore, part E must also have the structure position 2.
Real parts and position parts in part catalog, inventory part, manufacturing structures and routings
Through the two-step transfer of the template structure to manufacturing, part catalog, inventory part and manufacturing structure records are created. Depending on where it is created, the records can be purely position parts, real parts or both position and real parts.
The term real part is only relevant within the concept of position parts; real parts are simply non-positional parts or physical parts. They are the customary part catalog or inventory part records with which you are familiar. Real parts are tangible; they do not operate as placeholders nor stand for a set of parts. In contrast, position parts are conceptual; they operate as placeholders for a set of real parts that are valid for a given structure position. A position part has one or more real parts that it indicates.
Part catalog records for position parts are created through the template structure transfer process. (The part catalog records for real parts, i.e., the engineering parts in the template structure, are entered at the creation of engineering parts.) The part catalog record for a position part serves as the link through which the position part in manufacturing is mapped to an engineering real part - that does not belong to any site - in a template structure.
The template structure transfer process also creates new inventory part records or new revisions of existing records for both position parts and real parts. In addition, this transfer process creates monolithic disassembly and assembly manufacturing structures and routings for the inventory part position parts. These monolithic structures and routings are used by the disassembly, disposition and assembly shop orders created when the work scope interim order is released.
When the work scope for the MRO work order associated with your overhaul object is defined, a set of interim orders is created. Upon release of these interim orders, the disassembly, disposition and assembly shop orders are created for the position parts. Since disassembly has not yet occurred at the time of work scoping, the actual serial structure for the overhaul object is not known and therefore the disassembly, disposition and assembly shop orders are created for the position parts.
During disassembly, the actual structure of the overhaul object is determined. The parts that are received from a disassembly order are identified with their actual part number and tracking information when the parts are to be further disassembled, but parts received from a disassembly order that will be sent to a disposition order may be received as either real parts or position parts. This allows for the uncertainty about actual part numbers on parts that are to be inspected; the dispositioner can be responsible for identifying real part number and tracking data on parts being dispositioned. Note that, in such an order, you can either receive all the units of a part as position parts or all as real parts. For any given part, you cannot receive a combination of both types on a single order.
The parts received from disposition and assembly shop orders will all be real parts rather than position parts. Repair shop orders and external service orders that are generated will be for real parts. The assembly shop orders will continue to contain position parts as the ordered parts because it is not clear beforehand which parts will be used in assembling the overhaul part, but the allocations on these assembly orders will be changed from position parts to real parts as the real parts are identified and confirmed in the disposition process.
If position parts are identified as real parts during disassembly shop order receipt, the allocations for these position parts in the subsequent disassembly or disposition shop orders are replaced with allocations for the identified real parts. When position parts are identified or when their identities are confirmed during disposition inspection, the allocations for these position parts in the assembly shop orders are replaced with allocations for the real parts called out in the disposition.
Some of the MRO manufacturing operational data elements, which are designed to facilitate reuse, interact with only position parts, others only with real parts. For example, maintenance levels are attached only to position parts. However, discrepancy codes, repair codes and disposition codes are all associated only with real parts.