High variety, low volume, and short lead times have become the new standard in discrete manufacturing. With a large number of product variants, small batch sizes, complex routing, and frequent rush orders, scheduling easily becomes chaotic. Plans change constantly, execution struggles to follow, and production often feels like nonstop firefighting.
To solve this, we must break production planning into clear layers and connect them through three stable workflow links.
1. Why Is Scheduling So Difficult?
High-mix, low-volume production makes traditional experience-based scheduling ineffective:
- Orders change quickly
- Many constraints: machines, materials, and workers
- Plans often do not match real shop-floor execution
The root cause is not “poor scheduling skills,” but an unclear planning system.
2. Four Types of Plans: From Strategy to Execution
A complete scheduling system in discrete manufacturing consists of four layers, each solving a different problem.
1. Strategic Planning
This defines long-term goals, annual capacity layout, and product strategies.
It answers: “What will the company produce in the future?”
It guides:
- Long-term capacity decisions
- Product mix strategy
- Investment direction
2. Master Production Schedule (MPS)
MPS transforms orders and forecasts into overall production quantities and timing.
It answers: “How much do we produce in the upcoming period?”
Its key roles:
- Convert demand into capacity needs
- Set the production rhythm
- Drive procurement and material preparation
3. Material Requirements Planning (MRP)
MRP expands MPS into detailed material requirements:
- What materials are needed?
- How many?
- When must they arrive?
MRP ensures material readiness so production won’t stop due to shortages.
4. Detailed Scheduling
This is the most execution-oriented plan:
- Which machine works on which order?
- In what sequence?
- At what time?
It coordinates production at the shop-floor level and changes most frequently.
3. Three Links: Making Plans Truly Executable
Plans must flow through three interconnected links to work effectively.
1. Order → Production Link
This ensures:
- Real customer demand drives production
- MPS and scheduling follow clear priorities
- Plans match actual delivery requirements
Order changes must flow quickly into planning.
2. Material → Capacity Link
MRP connects material readiness with available production capacity:
- Are materials ready?
- Are machines available?
- Is manpower sufficient?
It identifies bottlenecks early to avoid unrealistic scheduling.
3. Plan → Execution → Feedback Link
Shop-floor variability is constant:
- Machine breakdowns
- Worker shortages
- Longer-than-expected process times
- Rush orders changing priority
Execution data must continuously feed back to MPS and scheduling, ensuring the plan stays alive and adaptable.
4. Key Practices for Successful Implementation
To make scheduling effective in a high-mix environment:
- Use layered planning: Strategy → MPS → MRP → Scheduling
- Enable real-time feedback
- Ensure material readiness
- Make priority rules transparent
- Use digital tools to handle complex constraints
Scheduling is not just “calculating orders”—it is organizing the entire workflow.
5. Conclusion
High-mix, low-volume production is not the reason for chaos.
A poor planning system is.
By establishing four levels of planning and connecting them with three workflow links, factories can move from constant firefighting to stable, predictable production.