dispatching rules

**Dispatching rules** is the **decision logic that determines which waiting lot a tool processes next under competing priorities and constraints** - rule quality directly affects throughput, cycle time, and due-date performance. **What Is Dispatching rules?** - **Definition**: Scheduling heuristics or algorithms applied at each resource release event. - **Rule Families**: FIFO, shortest processing time, critical ratio, due-date based, and weighted score approaches. - **Decision Inputs**: Lot priority, queue age, processing time, setup state, and downstream constraints. - **Execution Scope**: Applied in MES and dispatch engines across tool groups and route segments. **Why Dispatching rules Matters** - **Throughput Performance**: Dispatch choice determines bottleneck utilization and queue accumulation. - **Cycle-Time Control**: Good rules reduce average and tail waiting times. - **Delivery Reliability**: Priority-sensitive rules improve due-date adherence. - **Quality Protection**: Rules can enforce queue-time and hold-risk constraints. - **Operational Stability**: Consistent dispatch logic lowers ad hoc manual intervention. **How It Is Used in Practice** - **Rule Selection**: Match rule behavior to business objective and process constraint profile. - **Simulation Testing**: Validate candidate rules against historical and projected fab scenarios. - **Continuous Tuning**: Adjust rule parameters as demand mix, bottlenecks, and risk patterns change. Dispatching rules is **a central lever in fab operations optimization** - disciplined next-lot decision logic is essential for balancing speed, utilization, and quality risk in high-complexity manufacturing.