Standard Grade and Quality Targets

Define grade and quality targets

Standard Targets

To access this dialog:

The Standard Targets panel is used to add, edit and delete grade/quality scheduling targets relevant to a specific destination. One example of this would be to limit the flow of material to a plant destination to avoid exceeding the maximum known capacity for a time period.

This panel is used to both define the target variables and bounds, filter expression and period target bounds and associate the resulting constraint with a predefined destination

Targets are applied to the total material sent to a destination in a period and are the primary controls for the blending algorithm; they are defined using this and subsequent dialogs. A good example of a target might be the target head grade to the Plant.

Standard targets are formed using the grid. Once a target has been added, you can define its parameters, including whether to activate it or not. The constraint will have an associated Expression, based on entries in the table below.

A Minimum and Maximum target can be set for each time period defined for your schedule.

One or more targets can be set for the same destination, and targets can be set for any destination in your project.

Standard vs. Advanced Targets

Similar to standard grade/quality targets for destinations, advanced targets can create targets across multiple destinations including ratios, for example, total pit excavation vs. reclaim amounts. Within advanced targets grade values are considered as metal tonnages so to achieve the same target as a standard destination grade target within global it must be a ratio where the grade is divided by the weighted field. For example:

  • Standard Target AU,
  • Advanced Target AU/Tonnes  

    ...will both give the same result.

Targets are output to the Targets control bar for both global and destinations where the values in the schedule are calculated for the period(s).


Targets and Target Expressions

All block attributes are defined as mass. To consider element grade for a destination target, you can set a product target variable only and set the denominator to express the total ore mass. To consider element percentage grade, set the element coefficient in the numerator to 100.

Each Target is given a name and is defined by the target variables that apply to it. These variables come from the fields included in the Block Reserves (Results) file. The Target is expressed as a rate or ratio per period as follows:

  • Rate: V = Ax + By + Cz + ...
    Rate target types are constructed using a target variable Numerator value (without setting a Denominator, leaving it at 0).

  • Ratio:V = (Ax + By + Cz + ...)/(Dx + Ey + Fz + ...)
    Ratio target types are constructed using a target variable Numerator value and a Denominator value greater than 1.

where A, B, C, D, E, F are user-defined coefficients and x, y, z denote block attributes (fields, data columns) like grade/quality values, tonnage's, and elements mass.


Target Bounds

For each target variable you must define lower and upper bounds (minimum and maximum). The scheduler will search for schedules that keep all target variables within the specified bounds.

You can vary the bounds over time. For example, to set the two values to 2 and 6 for the first 2 time units, to 0 and 4 for the next 10 time units, and to 0 and 5 thereafter. These values are entered in separate records in the Target bounds by  grid as follows:

Row

End Period (Time)

Minimum

Maximum

1

2

2

6

2

10

0

4

3

200

0

5

 

note.gif (1017 bytes)

For the last time period, you can define End Period as any number greater than the lifetime of the mine.



Multiple Targets

The following notes apply when defining multiple targets:

  • Specify which material type can go to which destination, and the source from which the material is taken (e.g. reclaiming from a particular stockpile). Some material categories can potentially go to more than one of the defined destinations, for example ore may go to a plant or a leach pad.
  • Specify, for each destination, the required material amounts and qualities for the period. Target amounts are given as three values: minimum, maximum and specific target.
  • Use ratios or rates to define targets.
  • Blending to achieve multiple product types from several mining blocks is handled by specifying each product type as a destination.
  • If an objective function is defined this can be a choice of maximizing or minimizing any block value, such as tonnes, grade or value, to a specific destination.
  • A revenue field may have been imported, or may be virtually constructed using other imported fields. This revenue field will be one of the optional fields on which to optimize.
  • A choice of linear programming (LP) or quadratic programming (QP) is available for blending. QP always gives the nearest possible solution even when an exact solution is not possible.

Editing and Deleting Targets

Existing targets can also be edited or deleted by selecting the target from the list and selecting the relevant button.

 

Adding a New Scheduling Target

  1. In the Grade/Quality tab, click Add,

  2. In the Grade/Quality Target dialog, define the Target's name.

  3. Activate the Source cell and use the drop-down arrow to display the Material Movements Source popup. Use this popup to define one or more source locations from which material will be derived.

  4. Define each target variables Numerator (and for ratio targets, a Denominator) to update the Expression used for the constraint.

    For example if you wanted to set a target representing AU/CU, you could set the Numerator for AU to 1, and the Denominator for CU to 1 as well.

  5. Define the target's Target Bounds by Period settings. This will update the Target's period settings in the read-only table above.

  6. Click Apply to save the new target. More...


Field Details:

Standard Grade/Quality Targets grid: select a grade/quality target for viewing its details and bounds in the associated Target Details and Target Bounds panes. 

Use: if ticked, the listed grade/quality target is used when scheduling (default 'ticked').

Target: the grade/quality target's name.

Source: select the source of the material to be moved (the default is [All] meaning all material sources will be considered). Displays the Material Movements Sources dialog. Multiple sources are

Destinations: the target's destination. Select the drop-down list to pick one or more destinations to constrains a materials terminal location. Once chosen, the Categories options will be restricted to show only categories valid for the chosen destination/destinations.

Categories: select one or more reserves categories using the drop-down dialog. If one or more destinations have been selected already, the list of available categories will be restricted only to appropriate reserves categories for those Destinations.

Whilst the Categories list is filtered based on previously-selected Destinations, the reverse isn't applied. As such, if Categories are defined, be careful when subsequently editing Destinations as this could lead to an invalid constraint (e.g. where material movement is restricted to low grade material from a high grade destination).

 

Expression: the expression defining the target, either a rate or ratio, based on the Target Variables settings below.

Type: the target type, which will be either the Max or Min for a given time period.

Time Periods (one or more columns): any target limits per time period are shown here. This data is updated as the Target Bounds by Period table is used (see below).


Target Variables: this table is used to define how the variables used to define each target expression. 

Target variable: material attribute column names, automatically sourced from the Results table.

Numerator: enter a value..

Denominator: enter a value; if a value is entered, a Ratio target type is constructed, otherwise,if left at 0 (zero) a Rate target type will be defined.



Target Bounds: targets can be defined for each time period in your schedule.

End Period: select a period from the dropdown, in which, or up until which, the target applies.

Minimum: enter a minimum value for the target.

Maximum: enter a maximum value for the target.

  openbook.gif (910 bytes)   Related Topics

 

 The Scheduling Data Setup DialogAbout ConstraintsAdvanced Mass TargetsTarget Filter ExpressionsTarget Dependencies