Advanced Planning and Scheduling (APS)

Advanced planning and scheduling (APS) is a sub-component of supply chain planning, contextually describing manufacturing planning and scheduling.[1]

Advanced Planning and Scheduling (APS), that is using computer algorithms tied together with an easy to use Graphical User Interface, is being more and more recognized as the premier method of finding and improving the manufacturing production process.[2]

Advanced planning and scheduling (APS) software uses advanced math to analyze and calculate optimal production schedules, taking into account a range of constraints based on the company’s business rules and allowing the planner to generate and evaluate multiple scenarios. The purpose of scheduling software is to minimize production time and costs while maximizing efficiency by determining the optimum sequence of operations in order to reduce set-up times and changeovers.[3]

Unlike previous systems, APS simultaneously plans and schedules production based on available materials, labor and plant capacity. APS has commonly been applied where one or more of the following conditions are present:

  • make to order (as distinct from make to stock) manufacturing
  • capital-intensive production processes, where plant capacity is constrained
  • products 'competing' for plant capacity: where many different products are produced in each facility
  • products that require a large number of components or manufacturing tasks
  • production necessitates frequent schedule changes which cannot be predicted before the event

Advanced planning & scheduling software enables manufacturing scheduling and advanced scheduling optimization within these environments.[4]

Currently, the activities of the planning and control of companies are becoming increasingly complex and the managers of this area are constantly pressured to reduce operating costs, maintain inventories at adequate levels, to fully meet the demand of customers, and to respond effectively to changes that occur. The planning and scheduling task is important for most companies, so according to some authors, there is a need for further analysis of the practical use of production planning and control systems. Within the context of production planning and control systems development, in the 1990s were launched the APS systems, which represent an innovation when compared to their predecessors.[5]

Core APS Modules (See figure 1.)[6]
With the variety of software tools on the market that are considered supply chain applications, it is useful to start by defining what Advanced Planning and Scheduling means and the different software modules that can be called “core” APS applications. Considering that APS can be defined differently depending on the software vendor, consultant, or manufacturer being asked, this categorization is not a rigid one, but as an introduction to the software it is useful to understand the software as it is typically deployed. In most full-suite APS scenarios, the primary modules involve are: • Demand Planning • Network Optimization • Supply Planning • Factory Scheduling • Order Promising These modules are typically independent pieces of software that satisfy different business needs, but are designed to work in concert to optimize supply chain performance.

Advanced Planning and Scheduling
Figure 1. source: Spinnaker

APS Systems Structure (See figure 2.)[7]
According to Neumann, Schwindt and Trautmann (2002), APS systems offer support at all planning levels along the supply chain while observing resources limitation. The APS system input data include size of order, order due date, available capacity, product type, process routine, process time, cycle time, setup time, yield, tact time, preventive maintenance, mean time to repair, mean time between failure, and Work In Process (WIP); whereas outputs include equipment loading, fab utilization, line utilization, order release time, and order start/finish time (CHEN et al., 2013). The main constituent modules of the APS systems in the three levels of supply chains are shown in Figure 2 (MEYR; WAGNER; ROHDE, 2005).

Advanced Planning and Scheduling 1
Figure 2. source: Dialnet

The strategic planning of the supply network determines the structure of the supply chain in the planning horizon, including locations of factories and distribution centers and considers a long term planning horizon of ten years (GIACON; MESQUITA, 2011). The demand management balances customer requirements with the capabilities of the supply chain (CROXTON et al., 2002). Production and sales planning aims at efficient use of company capabilities and the realization of the foreseen demands in the medium-term planning horizon, by planning simultaneously the functions of production, purchasing and distribution (STADLER, 2005). Master Production Scheduling (MPS) defines the end items quantity to be completed in each week of the short-term planning horizon, periodically updating the plans after collecting and recognizing the most recent information (OMAR; BENNELL, 2009). The MRP carries out the material requirements explosion through information from MPS, generating orders of assembly, manufacturing and purchasing, in order to meet the final products demand (OMAR; BENNELL, 2009). Detailed production scheduling is generated taking into account the availability of capacity and materials, according to the guidelines of MPS (GIACON; MESQUITA, 2011). Distribution planning represents one of the most important activities in supply chain management and considers the availability of stocks and transports for generating the scheduling of deliveries (SAFAEI et al., 2010). Transport scheduling considers short-term factors, such as routing or vehicles availability (GIACON; MESQUITA, 2011). Available-To-Promise (ATP) aims to provide the customer specific requests in promised delivery date considering the demanded products availability (JUNG, 2012).

Value of an APS System[8]
Many definitions of an APS system are possible. Practically speaking an old-fashioned planning and scheduling system involves using planning boards, whiteboards, or pencil & paper. An "Advanced” Planning and Scheduling system is usually defined to be one that is computer based. Using this definition there is a wide variation in sophistication and cost of APS systems. Hard data on the financial value of planning and scheduling is difficult to collect because people rarely conduct a controlled before-and-after experiment for an APS system installation. Also very few academic studies have been completed. As a result most success stories and customer testimonials are anecdotal in nature. Considering these caveats, the available data suggests that the estimated improvement attributable to effective planning and scheduling is 5% to 15% as measured by a decrease in process costs (e.g. waste, changeover, inventory reduction) and/or increase in process throughput. In order to achieve this performance an APS system must be used in an effective business process whereby the data used is reasonably accurate and schedules and plans must be executed with reasonable precision. To achieve consistent results the planning and scheduling process must be repeated when business conditions change appreciably. Finally since the cost of an APS system is usually small with respect to the capital and operating costs of a process, any improvement usually accrues directly to profit. As such an APS system that works can be a good investment.

How to Benefit from Advanced Planning and Scheduling Systems (See Figure 3.)[9]
APS incorporate some form of computerised optimisation, using one or more mathematical algorithms. They can operate on individual transactions e.g. customer orders without the batching characteristic of MRP. In manufacturing, APS provides a method of concurrent synchronisation of material and capacity with customer orders. APS systems are not transactional systems. They prepare plans and schedules but then need to be linked to a transactional system like ERP to manage the execution of the plan or schedule.

Advanced Planning and Scheduling 2
Figure 3. source: Ortec

APS systems can be stand- alone systems or part of suites of systems (“enterprise solutions”), especially in larger organisations. Data interfaces are required to automatically receive input data and send results to other systems. Many APS tools and techniques focus on a part of the supply chain, and some can cover all aspects. This includes areas such as:

  • Supply chain planning
  • Demand management and sales forecasting
  • Factory planning and scheduling
  • Inventory planning
  • Transportation planning
  • Product lifecycle management
  • Electronic procurement
  • Inter-enterprise and intra-enterprise collaboration
  • Strategic planning

Professional Advanced Planning and Scheduling systems provide visibility of and compute plans and schedules for multiple simultaneous variables and constraints (e.g. materials, resources, demands), permitting them to generate plans that are optimised for multiple criteria (e.g. profitability, service, inventory level).

Measuring APS Success[10]
While there are some common measures, your concept of success will depend on your unique business — on factors such as what makes you more competitive, how your costs are distributed, and what kind of customer demand you have to meet. It's critical at the outset of an APS implementation to identify your critical areas and determine where APS can help. For example, if on-time shipments are a challenge, then you'll probably want to track due-date performance. If running out of materials in production is a frequent occurrence, then you'll need to track the frequency of these interruptions on the shop floor. If excessive WIP or long lead-times are problems, then you'll need to set up metrics for make-spans and queue times. Another common goal is to reduce the time planners spend updating schedules; in this case, tracking time spent before and after the implementation clearly will be helpful.

See Also


Further Reading