Constraints and cost weights¶
Also in the app
Press ? in Fab Dispatch to read this in the help center, or / to ask the assistant.
Hard constraints¶
A plan never breaks these. Every strategy is tested against them, on every fab:
- Certification: the engineer is certified for the job's tool family,
- Level: at or above the level the job needs (1–3),
- Max jobs: no engineer takes more jobs than their limit,
- Start window: work starts inside the job's window (a tool-down's response time),
- Shift end: all work finishes before the engineer's shift ends.
A job no engineer can do within these rules is unassigned, with the reason (for example 4 not certified, 1 at max jobs).
Soft constraints: the cost weights¶
Everything else is a cost, in points. The Cost weights sliders set how much each one matters, and every strategy re-solves as you drag.
| Weight | Default | Charged |
|---|---|---|
| Priority reward | 60 | A reward per priority point served (unserved work costs this much) |
| Walking | 4 | Per 100 m walked on the floor |
| Idle wait | 0.2 | Per minute an engineer waits for a job's window to open |
| Over-qualification | 8 | Per certification level above what the job needs |
| Workload balance | 5 | Per job the engineer already holds, so work spreads out |
In live dispatch, a sixth weight, stability (25), charges for moving a job to a different engineer when re-planning, so people aren't reshuffled for tiny gains.
Reset to defaults restores every slider.
Tuning tips¶
- Raise Walking when a metre of walking really costs more, for example on a floor where aisles
force long detours. Heavier cleanroom garb makes people slower, which is the fab profile's
walking speed (
walk_m_per_min), not the cost per metre. - Over-qualification charges for sending a level-3 engineer to a level-1 job, so a higher weight steers routine work to junior engineers when a cheaper qualified option exists. It does not hold anyone back: a plan still uses a senior engineer when they are the only one free. Keeping capacity in reserve for a fault that hasn't happened yet is not something the planner does.
- Raise Priority reward when unserved work is unacceptable, even at higher cost.