What is Advanced Planning and Scheduling (APS)?
Advanced Planning and Scheduling (APS) is a software-supported approach to detailed production scheduling. It takes machine capacities, material availability, shift models, and technical constraints into account in real time, enabling realistic completion dates.
Definition of Advanced Planning and Scheduling
Advanced Planning and Scheduling (APS) is a software-supported approach to production planning and detailed scheduling. The system takes into account machine and workstation capacities, material availability, qualifications, as well as technical constraints and sequencing requirements. It calculates a realistic and optimized production sequence based on the standard processing times for each product across an organization's work centers and their available capacities. In doing so, it provides transparency into dependencies, schedules, and production bottlenecks.
Introduction: Why Production and Detailed Planning are Becoming Increasingly Complex
Modern production environments are characterized by a high degree of product variation and increasingly short delivery times. Customer requirements change rapidly, while the level of automation continues to grow. At the same time, production planning must account for thousands of dependencies, resources, and constraints simultaneously. This is where Advanced Planning and Scheduling (APS) comes into play. However, to successfully implement such a solution, companies need expertise, consistent execution, and perseverance.
In many companies, it has become clear that traditional planning methods are reaching their limits, a finding also confirmed by the Fraunhofer IPA in its analysis of Advanced Planning and Scheduling. This becomes particularly evident when production processes are dynamic, prone to disruptions, and highly interdependent. APS enables data-driven, capacity-based detailed scheduling that reflects the actual state of production.
Limitations of Classical Production Planning
Traditional planning tools operate on the basis of static assumptions. Excel spreadsheets, manually maintained lists, or basic ERP capacity planning modules are typical examples. They have several structural limitations:
- They cannot accurately represent complex interdependencies and dynamic changes.
- Bottlenecks, setup times, shift models, and employee qualifications are not taken into account.
- They cannot respond effectively to short-term disruptions, as they do not process real-time data.
- Planning is carried out against unlimited capacity, and planning data must be entered manually.
This often leads to inaccurate planning and unreliable schedules in practice. In highly complex manufacturing environments, the resulting coordination effort can become enormous, with direct impacts on costs and schedule transparency.
Meaning of Advanced Planning and Scheduling
Advanced Planning and Scheduling (APS) refers to an integrated approach to production planning and detailed scheduling. The methods used enable realistic scheduling by taking actual capacities and existing constraints into account. Disruptions in the production process can be addressed quickly, and every rescheduling action is fully transparent. As a result, Advanced Planning and Scheduling is a key component of modern production control.
Goal of an APS System
An APS system automates and optimizes complex planning decisions. It takes capacities, resources, constraints, and dependencies into account in the best possible way. The result is efficient, transparent, and flexible production control.
The key goals at a glance:
- Scheduling and capacity planning: Machines, work centers, and resources are utilized optimally. Overloads are avoided, and realistic completion dates are ensured.
- Prioritising orders: Important or urgent orders are given priority. Changes and schedule adjustments can be implemented flexibly.
- Simulation of planning scenarios: The planner can test alternative scenarios and evaluate their impact. Risks are identified at an early stage, allowing the best solution to be selected.
- Minimising bottlenecks and setup times: The APS system identifies problem areas early and ensures a smooth production process.
- Data-driven decisions: All production data will be processed. Planning will be faster, more accurate, and more transparent.
Distinction from ERP Systems and Rough Planning
An ERP system (Enterprise Resource Planning) manages all business processes within a company, including procurement, production, inventory management, sales, and finance. It maintains master data for materials, suppliers, and locations and forms the basis for initial rough planning.
Rough planning in an ERP system often assumes unlimited capacity. It checks whether customer demand can be met through existing inventory or production. However, actual capacity constraints of machines and personnel are generally not taken into account. The result is unrealistic production plans, missed deadlines, and overloaded resources.
An APS system builds on ERP data and provides a much more detailed and realistic production plan. It always schedules using the standard processing times of products against finite capacities and takes all real-world constraints into account, including technical limitations, material availability, and workforce qualifications. The result is reliable completion dates rather than theoretical target dates.
How does Advanced Planning and Scheduling work?
Planning Based on Deadlines, Restrictions, and Capacities
An APS system creates a detailed production plan while taking all relevant constraints into account. To do this, the system analyzes the current situation by downloading master data, determining the status of available resources, and then analyzing and optimizing the order backlog within the system. This process typically consists of the following steps:
- Machine capacities: The system checks which machines are available at what times and how much capacity they provide.
- Standard times: The estimated standard processing time required to manufacture the product is derived from the master data and scheduled as machine or work center occupancy time.
- Tools and fixtures: Specialized production fixtures are treated as resources, allowing bottlenecks to be identified at an early stage.
- Shift models: Different working hours and shift patterns are incorporated into the planning process.
- Material availability: The current availability of raw materials and components is checked to prevent production stoppages.
- Setup and changeover times: Time required for machine setup or tool changes is taken into account.
Based on these factors, the software calculates an optimal sequence of production steps and feeds the resulting start and finish dates back into the ERP system via an upload. The result is a realistic production plan that provides scheduled dates for every manufacturing step.
Optimisation Algorithms in APS
Specialized algorithms are used to calculate an optimal plan. Typical methods include heuristics, mathematical optimization models, and rule-based approaches. They are executed step by step within a configurable planning run and generate an efficient as well as realistic production plan.
Typical heuristics in a planning run include:
- First-In-First-Out (FIFO): Orders are processed in the order they are received.
- Shortest Processing Time (SPT): Orders with the shortest processing time will be prioritised in scheduling.
- Earliest Due Date (EDD): Orders with the earliest delivery date will be scheduled first.
- Priority Rule: Orders with a higher priority are given preferential treatment, for example in the case of urgent customer orders.
- Least Slack Time: Orders with the smallest time buffer between completion and delivery date are scheduled first.
The goal in all cases is to make optimal use of available capacities and reliably meet delivery deadlines.
Frozen Horizon: Please Do Not Touch!
A “Frozen Horizon” in APS systems refers to a future time period during which no changes may be made to the production schedule. Within this defined horizon, orders and resources are firmly scheduled, and adjustments such as rescheduling, date changes, or the addition of new orders are not permitted until the Frozen Horizon has expired. The purpose of this concept is to ensure planning reliability and production stability. It allows manufacturing processes to run predictably by preventing last-minute changes and enabling employees to rely on established schedules and workflows.
Role of Real-Time and Planning Data
The performance of an APS system depends directly on the quality of the master data used. The following information is critical:
- Standard processing time: The standard time is the amount of time that an APS system schedules as occupancy time for a work center. If this time is incorrect or differs from the actual time required, an APS system will not produce a realistic schedule. Shit in, shit out!
- Manufacturing progress: Timely feedback from production is the foundation of any reliable planning process. If the APS system does not know how far an order has already progressed, it cannot plan accurately either.
- Fault reports: Information about downtime enables rapid schedule adjustments for machines and work centers.
- Online feedback: Quantities, quality data, and actual processing times improve planning accuracy, as they ensure that the APS system is continuously supplied with the correct information in real time.
- Resource availability: Only with real-time availability data, such as inventory levels and shortage lists, can bottlenecks be identified at an early stage.
By capturing production data in real time, manual errors can be avoided and up-to-date planning information can be provided. Three key principles apply:
- Master data must be continuously maintained.
- Standard times or planned times must be regularly compared with actual processing times.
- Automated data collection via an online MES system prevents errors and keeps planning data up-to-date.
Only if these requirements are met can an APS system control production in the best possible way.
Detailed Planning in Production
What exactly does detailed scheduling mean?
Detailed scheduling defines the exact timing of production activities. It takes all available resources into account, including machines and employees. Specifically, it covers:
- Sequence planning of production steps based on standard processing times.
- Assignment of shifts and machines.
- Inclusion of alternative backup resources.
- Co-ordination of successive manufacturing processes.
The goal is to create a realistic and feasible production plan that ensures smooth production operations.
Short-Term Adjustments and Re-Planning
Unplanned changes occur regularly in production. Machine breakdowns, delayed materials, staff shortages, or shifting priorities are typical examples. An APS system enables production schedules to be adjusted quickly and easily. The impact of every rescheduling action becomes immediately visible.
How Advanced Planning and Scheduling Manages Disruptions and Bottlenecks
Advanced Planning and Scheduling enables disruptions and bottlenecks to be identified transparently. Alternative resources are taken into account, and the impact of problems is evaluated in real time. An integrated MES system provides the required real-time data directly from production for this purpose.
Overview of the Benefits of Advanced Planning and Scheduling
Improved On-Time Delivery Performance
Planning based on actual capacities enables reliable delivery dates. Production processes become more stable, and schedule changes are significantly reduced. Advanced Planning and Scheduling therefore increases planning reliability and minimizes unexpected disruptions.
Better Resource Utilisation
An APS system uses machines and personnel more efficiently. Bottlenecks are identified at an early stage, optimal production sequences are calculated, and unnecessary setup times are minimized. As a result, output increases without requiring additional resources.
Reduced Lead Times
Materials and resources are coordinated and made available as needed. Waiting times and intermediate storage are minimized. As a result, production processes run faster and more smoothly
Conclusion: Advanced Planning and Scheduling as the Key to Efficient Production Planning
Companies must design their production processes to be flexible, transparent, and efficient. Advanced Planning and Scheduling (APS) provides a suitable approach for achieving realistic detailed scheduling and reliable delivery dates. The quality of the master data is crucial, as it forms the foundation of every successful planning process.
An APS system increases on-time delivery performance, flexibility, and resource efficiency. A prerequisite is that feedback from production must be reliable and up to date, for example through an MES system. Without real-time data, no realistic plan is possible. The operational level and the planning function must be synchronized.
IGH Infotec AG supports companies with MES and mobile data collection solutions to ensure a seamless connection between planning and production, thereby increasing transparency and competitiveness.
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