Time fences play a crucial role in master production scheduling (MPS) by establishing policy change points and dividing the planning horizon into distinct zones. These fences serve as control mechanisms to ensure stability and prevent excessive rescheduling, ultimately contributing to effective MPS management.
Key Facts
- Policy Change Points: Time fences serve as policy change points where restrictions or changes in operating procedures take place. These points help determine the level of difficulty and impact of schedule changes on related operations.
- Planning Horizon Division: Time fences divide the planning horizon into different zones or areas. These zones include Planning Zone 1 and Planning Zone 2.
- Planning Zone 1: This zone is the final assembly or fabrication period where the final configuration of the product is determined. Changes to the schedule in this zone should be made by the master production scheduler and require careful analysis and approval from top management.
- Planning Zone 2: In this zone, MPS items consist of firm planned orders that have been examined by the master production scheduler. Changes to the schedule in this zone should be minimized to maintain stability and prevent excessive rescheduling of lower-level items.
- Control and Stability: Time fences help maintain control and stability in the planning process by limiting changes within specific periods. This ensures that resources are committed to meeting firm orders and prevents unnecessary fluctuations in the schedule.
Policy Change Points
Time fences act as policy change points where restrictions or changes in operating procedures take place. They help determine the level of difficulty and impact of schedule changes on related operations. Within the cumulative lead time, changes to the MPS can be made with relative ease, having minimal effects on material and capacity plans. However, changes inside the cumulative lead time become increasingly challenging, emphasizing the importance of time fences in managing these changes.
Planning Horizon Division
Time fences divide the planning horizon into different zones or areas, each with its unique characteristics and control mechanisms. The two primary zones are Planning Zone 1 and Planning Zone 2.
Planning Zone 1
Planning Zone 1 encompasses the final assembly or fabrication period, where the final configuration of the product is determined. Changes to the schedule in this zone should be made by the master production scheduler and require careful analysis and approval from top management. This is because rescheduling items in this zone can have significant implications, including increased inventory value and potential delays in production.
Planning Zone 2
Planning Zone 2 consists of firm planned orders that have been examined by the master production scheduler. Changes to the schedule in this zone should be minimized to maintain stability and prevent excessive rescheduling of lower-level items. This zone is particularly sensitive to lead times, and changes can impact priorities and schedules for components, leading to potential delays and disruptions.
Control and Stability
Time fences contribute to the control and stability of the planning process by limiting changes within specific periods. This ensures that resources are committed to meeting firm orders and prevents unnecessary fluctuations in the schedule. By establishing these boundaries, time fences help maintain the integrity of the MPS and reduce the risk of disruptions caused by frequent rescheduling.
Conclusion
Time fences are essential tools in master production scheduling, serving as policy change points and dividing the planning horizon into manageable zones. They promote control and stability by limiting changes and ensuring that resources are allocated effectively. By understanding the purpose and application of time fences, organizations can optimize their MPS processes, minimize disruptions, and enhance overall production efficiency.
References
- Oracle Master Scheduling/MRP and Supply Chain Planning: Time Fence Control (https://docs.oracle.com/cd/A60725_05/html/comnls/us/mrp/tfctrl.htm)
- Example 3 (https://amgimanagement.com/example-3/)
FAQs
What are time fences in master production scheduling?
Time fences are policy change points that divide the planning horizon into distinct zones, each with its own set of rules and restrictions. They help manage changes to the master production schedule and ensure stability in the planning process.
Why are time fences used in MPS?
Time fences are used to control and stabilize the MPS by limiting changes within specific periods. This helps prevent excessive rescheduling, maintains the integrity of the schedule, and ensures that resources are allocated effectively.
What are the different types of time fences in MPS?
There are several types of time fences used in MPS, including the planning time fence, assembly lead-time fence, competitive lead-time fence, and customer backlog time fence. Each fence serves a specific purpose and is applied based on the product and manufacturing environment.
How do time fences help in managing schedule changes?
Time fences help manage schedule changes by defining the points at which changes can be made without significantly impacting related operations. They also establish different levels of control for different parts of the planning horizon, ensuring that critical changes are carefully evaluated and approved.
What are the benefits of using time fences in MPS?
The benefits of using time fences in MPS include improved control over schedule changes, reduced rescheduling of lower-level items, increased stability in the planning process, and better allocation of resources.
How are time fences typically implemented in MPS systems?
Time fences are typically implemented in MPS systems through the use of software algorithms and parameters. These algorithms and parameters define the location and characteristics of each time fence, as well as the rules for how changes are handled within each zone.
What are some common challenges in managing time fences in MPS?
Some common challenges in managing time fences in MPS include determining the appropriate location and settings for each fence, coordinating changes across different departments and systems, and managing exceptions and special cases.
How can organizations optimize the use of time fences in MPS?
Organizations can optimize the use of time fences in MPS by carefully considering the specific needs and characteristics of their products and manufacturing processes, conducting regular reviews and adjustments to the time fence settings, and ensuring effective communication and collaboration among all stakeholders involved in the planning process.