Advanced Planning and Scheduling
Advanced Planning and Scheduling systems (APS ) systems are used in the production economy to support planning functions in accordance with MRP- II method, so for example, the currently available ERP systems and many PPC systems used. A generally accepted and precise definition, for example, by the American Production and Inventory Control Society APICS or REFA Association currently does not exist.
Finite Capacity Scheduling
Finite Capacity Scheduling ( FCS) APS modules are modules for simultaneous planning of resources (materials, equipment, personnel and tools) and for the calculation of production start dates.
In contrast to FCS is MRP II, which calculated in a backward scheduling the start time for production orders from primary and secondary requirements. This calculation is a fixed cycle time based, i.e., the time for the production of a component is always assumed to be equal, regardless of
- How large the order quantity
- Such as high capacity utilization
- Which the means of production in which order ( work plan ) must be used
This results in a highly distorted picture of the expected completion dates that can not be corrected by changing the schedule parameters.
FCS systems ( modules) set a at this point. Calculate the expected production time from planned times for the equipping and production, to investigate whether production capacity is available and create a plan for the start times of individual jobs.
Are being introduced heuristic optimization methods ( constraint programming, evolutionary algorithms) to establish improved plans. The calculation is usually done iteratively, ie it is scheduled a job, then the next ... until the " Planning Board " fills slowly. The calculations when adding an order are comparatively fast. A recalculation of the entire planning board, etc. can require considerable time depending of the priority rules, constraints, schedule rules.
High demands on a FCS system arise with more varied individual and small series production. In particular, the engineering has often confronted with high variety of parts and medium and small lot sizes with missing parts situation in the assembly and an unsatisfactory punctuality. Here suitable FCS systems must have high-performance synchronization and coordination properties, which in turn requires a high demand on the optimization algorithms used. However, few FCS systems then make a simultaneous comparison of the availability of materials.
Other APS systems
Other software modules are available for other areas of the ERP planning. So there are rule-based systems for forecasting ( forecasting ), available-to -promise (ATP ~ availability predictions ), Distribution Planning ( cargo space planning, transportation time, etc.), demand management, warehouse management ( storage, sampling, etc. with optimized stroke / time characteristic) and pretty much every other area of the supply chain.
Criticism
APS systems are an attempt of mathematical models with more refined data to achieve a more accurate prediction of the future. The calculated results are based on assumptions, such as an "average production time per part ", which are variable in modified raw material, depending on the machine status, production temperature, etc.. Often the amounts are far from being reached, at which a statistical compensation would result. Often APS systems reduce the distance plan to target, but does not completely close the gap.
Alternative methods, such as JIT, reduce the plan required by systematic control of the production environment, achieve long-term but only a partial solution to production problems.
Compared with the classical MRP- II calculation FCS systems offer benefits that are paid to the maintenance and procurement costs for the data etc.. So far, however, also shows that people in the planning are as indispensable as before the introduction of APS.