Product optimisation is applied to all transactions where the Destination Logic rule type is set to "Crusher Feed".

For product-optimised transactions, ATS does not schedule a destination until the end of the period. Once it knows all the ore that has been mined in the period, it decides what to do with it based on the costs and revenues applied to the movement and processing of the material.

The rules in the Product Specifications step define the positive and negative cash flows derived from each activity.

Positive Cash Flows: the dollar per tonne in revenue for dumping a material at a location, ie. Oz to crusher.
Negative Cash Flows: the dollar per tonne in cost for dumping a material at a location, ie. rehandle cost per tonne onto stockpile; process cost per tonne into crusher.
Grade Penalties: the dollar per tonne per point deviation from grade targets.
Grade Limits: minimum and maximum weighted average product grade at the end of the period.
Blend Limits: minimum and maximum average material ratios at the end of the period.

Generally a Tactical Scheduler project should have at least one of the following:

Positive Cash Flow for ore to crusher.
Negative Cash Flow for material to a rehandle stockpile.
Neutral Cash Flow for material to a long term stockpile.
Grade limits for feed.

If the crusher isn't being fed, it is almost always due to missing positive cash flows or due to conflicting grade limits.

Gold Mine Example

Take the following gold mine setup:

Destination Logic

Destination Logic describes the final resting place at the end of the period. The Crusher is not a final destination (it feeds the Cone), instead it is listed in the Steps Logic as a waypoint.

Ex-Pit:
- Waste to dump
- HG* to ROM, Cone, Mill
- LG to LTS, ROM, Cone, Mill
Rehandle:
- ROM to Cone, Mill
- LTS to Cone, Mill

Where HG* represents materials HG1, HG2, HG3.

Steps Logic

Steps Logic describes the in-period waypoints between original source and final destination, and what fleet (or conveyor) is used on each leg.

Ex-Pit
- Ore => ROM => Crusher => Cone => Mill
- Ore => ROM => Crusher => Cone
- Ore => ROM
- LG => LTS
Rehandle
- LTS => ROM => Crusher => Cone => Mill
- LTS => ROM => Crusher => Cone
- ROM => Crusher => Cone => Mill
- ROM => Crusher => Cone
- Cone => Mill

Constraints

When material is routed through the Crusher via the Steps Logic, it does not count as crusher throughput. Therefore we must add constraints to limit the Crusher feed.

Standard Constraint "Crusher Limit" applies to:
- (Pit, LTS, ROM) => (Cone, Mill)

Product Specifications

Suppose we want to apply the following rules to the optimisation:

Higher grade material should be fed preferentially.
Higher grade material should be stockpiled preferentially.
Mill feed should not exceed 10% Oxide (>90% Fresh)

We can achieve this with the right cash flows and blend targets.

Rule Type	Double Handling Threshold	Value
StockpileCashFlow	ROM => Cone	Cash flow = +$1000/bcm (ATS implicity penalises stockpile-to-stockpile movement at -$1000/bcm)
StockpileCashFlow	LTS => Cone	Cash flow = +$1000/bcm (ATS implicity penalises stockpile-to-stockpile movement at -$1000/bcm)
Rule Type	LTS Build	Value
StockpileCashFlow	LTS build LG1	Cash flow = zero (no penalty for long term stockpile)
Rule Type	ROM Build	Value
StockpileCashFlow	ROM build HG1	Cash flow = crush & convey cost per oz = -$2/oz
StockpileCashFlow	ROM build HG2	Cash flow = crush & convey cost per oz = -$4/oz
StockpileCashFlow	ROM build HG3	Cash flow = crush & convey cost per oz = -$6/oz
StockpileCashFlow	ROM build LG	Cash flow = crush & convey cost per oz = -$8/oz
Rule Type	Cone Build	Value
StockpileCashFlow	Cone build HG1	Cash flow = conveyor cost per oz = -$1/oz
StockpileCashFlow	Cone build HG2	Cash flow = conveyor cost per oz = -$2/oz
StockpileCashFlow	Cone build HG3	Cash flow = conveyor cost per oz = -$3/oz
StockpileCashFlow	Cone build LG	Cash flow = conveyor cost per oz = -$4/oz
Rule Type	Mill Feed	Value
CrusherCashFlow	Mill feed HG1	Cash flow = revenue per ounce - milling cost per tonne = +$1000/oz
CrusherCashFlow	Mill feed HG2	Cash flow = revenue per ounce - milling cost per tonne = +$500/oz
CrusherCashFlow	Mill feed HG3	Cash flow = revenue per ounce - milling cost per tonne = +$250/oz
CrusherCashFlow	Mill feed LG	Cash flow = revenue per ounce - milling cost per tonne = +$100/oz
Rule Type	Blending	Value
StockpileBlendTarget	Oxide Ratio into Cone	Maximum = 10%
CrusherBlendTarget	Oxide Ratio into Mill	Maximum = 10%

For this example, StockpileCashFlow values should be set equal to the transport cost between the dump point and the final revenue point (in this case, the Mill). This makes destinations closer to the Mill more attractive.

Worked Example

During the period, the Agent mines blocks. If the Destination Logic rule is marked as "Crusher Feed", then the material is held in a virtual stockpile until the end of the period. At the end of the period, the Agent assesses the product specifications and assigns the material to its final destination.

Mined quantity in Period 1:		Destination capacities:
HG1: 600 kt / 40,000 oz HG2: 800 kt / 30,000 oz HG3: 1000 kt / 20,000 oz LG: 1500 kt / 15,000 oz		Crusher: 1,000,000 tonnes Cone: 1,000,000 tonnes ROM: Infinity LTS: Infinity
HG1 destination cash flows:	HG2 destination cash flows:	HG3 destination cash flows:	LG destination cash flows:
HG1 => Mill @ $1000/oz HG1 => Cone @ -$1/oz HG1 => ROM @ -$2/oz	HG2 => Mill @ $500/oz HG2 => Cone @ -$2/oz HG2 => ROM @ -$4/oz	HG3 => Mill @ $500/oz HG3 => Cone @ -$3/oz HG3 => ROM @ -$6/oz	LG => Mill @ $500/oz LG => LTS @ (zero) LG => Cone @ -$4/oz LG => ROM @ -$8/oz

Destination optimisation (not considering oxide ratios):

Material	Destination	Quantity	Cash flow
HG1	Mill	600 kt / 40,000 oz	+$40,000,000
HG2	Mill	400 kt / 15,000 oz	+$7,500,000
HG2	Cone	400 kt / 15,000 oz	-$30,000
HG3	Cone	600kt / 12,000 oz	-$36,000
HG3	ROM	400 kt / 8,000 oz	-$48,000
LG	LTS	1,500 kt / 15,000 oz	$ (zero)

The oxide ratio rules act as an additional cap on feeding the Mill or the Cone. Assuming capacity remains in the Mill, the optimiser will continue to maximise revenue (progressively feeding HG1, HG2, HG3, LG oxides), until it hits the 10% cap. At this point the next least costly option is the Cone, which is filled in the same order until the 10% cap is reached. If both Mill and Cone hit the 10% oxide limit, then the material defaults to the ROM.

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