Objectives
An objective is what the plan tries to improve. Each problem chooses one or more.
Several objectives at once
Section titled “Several objectives at once”With several objectives, the engine looks for trade-off solutions: plans that cannot be improved on one objective without worsening another (the Pareto front). Objectives can also be ranked by priority, so that an objective only breaks ties when the previous ones are equal, within a tolerance.
Each objective has a weight and, in some cases, its own parameters.
Makespan
Section titled “Makespan”Finishes everything as early as possible. Minimises the moment the last task finishes.
When to use it: when what matters is freeing up capacity early and there are no committed dates.
On-time delivery
Section titled “On-time delivery”Each order finishes as close as possible to its due date.
| Parameter | What it is |
|---|---|
| Lateness weight | How much each time unit late is penalised |
| Earliness weight | How much each time unit before the date is penalised |
| Duration weight | How much it is penalised for the order to stay open for a long time |
| Weights per order | Each order or customer can have its own |
Requires orders with a due date. When to use it: make-to-order production.
Order compactness
Section titled “Order compactness”Minimises the time between the first and the last task of each order: less work in progress.
Levelled availability
Section titled “Levelled availability”Spreads maintenance stoppages so that not too many assets are down at the same time. Penalises the daily variation in the number of assets under maintenance and, above all, the peaks.
When to use it: fleet maintenance.
Optimal service point
Section titled “Optimal service point”Each service has an allowed interval since the previous one of the same type (a minimum and a maximum). This objective places each service near the centre of that interval: not so early that interval is wasted, nor so late that it becomes a risk.
Plan stability
Section titled “Plan stability”Changes as little as possible relative to a reference plan, usually the current one. Changes close to the start weigh more than distant ones: moving something from tomorrow is more disruptive than moving something from next month.
When to use it: when replanning.
Sequence costs
Section titled “Sequence costs”Some resources have a set-up cost that depends on which task follows which (a change of colour, format or tooling). This objective minimises the sum of those costs. It is described with a table: for each resource, the cost of doing task B straight after task A.