Varying dig rates

In the material flow diagram, movements (such as arcs from a stockpile to a crusher) can be assigned quality objectives. These objectives define the desired material specifications—such as grade thresholds or contaminant limits—that must for the material moving over the specified movements.

When generating the Product Optimiser schedule, the software plans and optimises the flow of material from the pit loading points to the final destinations, aiming to meet these quality objectives for each movement. For example:

• The movement from a crusher to a final product could require a gold grade between 0.6 and 0.7.

• Movements to the final LGSx product might require a minimum gold grade of 0.45.

The optimiser controls material movements to meet these targets as closely as possible.

Reducing production

Traditionally, the Product Optimiser achieves product quality objectives by allocating material to destinations (e.g., crushers or wash plants) and sending any excess to stockpiles. However, at some mine sites this approach isn’t viable.

The Reduce Production to Achieve Blend feature allows the scheduling engine to dynamically adjust the production of mining equipment (e.g., shovels or diggers) across entire periods. This helps meet product quality objectives on movements.

This functionality is useful in operational contexts where:

• Stockpiling is limited or unavailable. For example, due to environmental constraints, space limitations, or operational policies that restrict material rehandling.

• Short-term scheduling accuracy is critical, such as in shift-based planning, where quality targets must be met within narrow timeframes rather than averaged over weeks or months.

In such cases, the schedule cannot rely on sending excess material to stockpiles to balance quality. Instead, it must control the flow of material at the source by adjusting how much each resource contributes.

Enable the feature

To enable this feature, it must be activated at both the site level and for the individual resources involved.

• Turn on Reduce Production to Achieve Blend in Site Configuration > General and Calendar Settings.

• Enable Variable Dig Rates in Config > Resources.

Automatically inserting delays

Once the feature is enabled, the Product Optimiser can dynamically adjust the production rates of constrained resources that contribute to movements with quality objectives. The optimiser controls material flow at sources by modifying how much each resource produces during a scheduling period.

To achieve this, the optimiser inserts delays into a resource’s periodic task list. These delays reduce the total time available for production, effectively lowering the resource’s output for that period. The length of each delay is calculated to help the resource reduce its contribution enough to meet the blend objectives.

While reducing production increases the likelihood of meeting quality targets, it doesn’t guarantee success. If the blend objectives still cannot be met, the schedule may be infeasible. In such cases, the objectives or material flow configuration may need to be adjusted to create a more realistic plan.

Production will never be reduced below the minimum production rate defined for the period (see Minimum production below).

These reductions are reflected in the Gantt chart.

• The actual production rate of the resource within a period reflects these dynamic changes.

• If a resource is delayed, a task labelled Optimiser Delay is inserted into the resource’s row.

A simplified view of the Gantt chart. To help achieve quality objectives, the software automatically slows down the 992-1 resource by inserting an Optimiser Delay.

Minimum production

Each resource includes a Minimum Production Rate field (refer to Client > Gantt Chart), defined as a factor between 0 and 1 (e.g., 0.5 means the resource can be slowed to 50% of its maximum rate across the period). This factor can vary by resource and period.

Example

If a resource has:

• A base production rate of 1,000 t/h across all periods

• A minimum production rate factor of 0.5

The optimiser can reduce its rate to 500 t/h during periods where slowing production helps meet blend targets.