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Advanced Planning and Scheduling (APS) functionality has historically been available via standalone packages that require integration with a firm's ERP system, but many aspects have been incorporated (on a continuously evolving basis) into the major ERP software packages. The distinguishing features of APS functionality include a graphical user interface and finite scheduling rules that incorporate comprehensive models of resource requirements and availability.
- Graphical user interface for a schedule board. A schedule board typically employs a Gantt chart format to display the workload (such as work order operations) against the required resources (such as work centers). A good graphical interface makes the schedule board easier to understand and use, especially with flexible formatting to meet unique user requirements, drill downs about constraints and scheduling rules, and support for manual overrides. In contrast, the schedule board will have limited effectiveness with a cumbersome graphical interface, inflexible formatting, weak drill downs, and limited manual overrides.
- Finite scheduling rules based on comprehensive models of resource requirements and availability. Comprehensive models of available resource capacity, for example, may include shift patterns of available hours and head counts, efficiency factors, and skill sets by type of machine or labor. Some machines can process multiple items at once (such as ovens and slitters), which means they also have a capacity limit of weight, volume, width or other dimension. In addition, scheduling typically requires detailed routing information about resource requirements, such as the operation sequence, primary and secondary resources, machine-specific processing times, sequence-specific setup time, parallel operations, alternate operations, and material requirements tied to an operation.
The benefits of APS functionality (and the wow factor of a sales demo) must be tempered by the difficulties associated with actual implementations. The finite scheduling logic underlying an automatically-generated schedule can be very complex and difficult to understand, which often means that users will ignore the suggested schedule and proceed with their traditional manual scheduling approaches. The dynamic nature of resource availability -- such as hourly changes in head counts or machine down time – may require a tremendous amount of data maintenance.
Another implementation difficulty involves the integration between a stand-alone APS package and an ERP package (or a firm's legacy applications). Integration often requires extensive interfaces and synchronization of data. The APS package may not be able to handle certain constructs within the ERP package, such as component date effectivities in a bill of material, or capable-to-promise calculations across a multilevel bill. Conversely, the ERP package may not support various models of resource requirements and availability that represent critical information for finite scheduling.
The APS functionality within ERP software packages has been maturing so that they are becoming easier to implement and use, as well as less expensive. My recommendation concerning the use of an ERP package or a standalone APS package would depend on the situation.
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