Material Cost and Utilization for Die Casting
This section describes how material cost and utilization are calculated for the Casting utilization process, Melting.
Material Cost = Rough Mass * Material Unit Cost
Material cost is the product of the following:
• Rough Mass (see formula)
• Material unit cost (specified by the material property Cost)
Rough Mass = Finish Mass / Utilization
Rough mass is the mass per part that accounts for material cost per part. In the default utilization mode, it is the sum of the following:
• Mass of the finished part
• Mass of the metal chips removed from the part by secondary machining operations
• Mass of the un-remeltable material lost per part due to spillage and oxidation
• Mass of the material lost due to parts scrapped by non-foundry processes (amortized over all parts in the current production scenario)
This assumes the following can be remelted, and so does not contribute to material cost:
• Parts scrapped by processes performed at the foundry
• Contents of the feeder system (runners, risers, etc.)
In all utilization modes, rough mass depends on the following:
• Finish mass (product of part volume and material density)
• Utilization (specified by the formula below, or specified in the Material Utilization section of the Material Selection dialog)
Utilization = Part Volume /
((Part Volume + Metal Chip Volume + Volume Loss + Non-remeltable Volume) / Non-foundry Yield)
In the default utilization mode, utilization depends on the following:
• Part volume (determined by geometry extraction)
• Metal chip volume: derived by summing metal chip volume for each machining operation that is applied to the part. For fully-machined features, this calculation is based on feature volume. For machine-finished features, the calculation is based on the area of the finished surface. The calculation assumes that the depth of material removed during finishing is the value specified by the cost model variable finishAllowance.
• Volume loss (see formula)
• Non-remeltable volume (see formula)
• Non-foundry yield (see formula)
Volume Loss = Mass Loss / Material Density
Volume loss is the pouring volume of metal that is oxidized or spilled during melting and cannot be re-melted. It is a function of the following:
• Mass loss. Specified by the formula below or the process setup option Mass Loss—see
User Inputs for Die Casting.
• Material density (specified by a material property)
Mass Loss = Mass Poured Excluding Loss * (1 / (Machine Yield Loss * Material Yield Loss Factor) – 1)
Mass loss is the pouring mass of metal that is oxidized or spilled during melting and cannot be remelted. By default, it is specified by this formula. Users can override the default with the process setup option Mass Loss—see
User Inputs for Die Casting. Computed mass loss is a function of the following:
• Mass poured excluding loss. See formula below.
• Machine yield loss: fraction of material not lost through spillage (specified by a machine property)
• Material yield loss factor: fraction of material not lost through oxidation (specified as a material property)
Mass Poured Excluding Loss = Mass Before Machining + Mass Waste
This is the portion of the mass poured per part that includes remeltable material from runners and risers, as well as material from scrapped parts (amortized over all the parts in the current production scenario), but does not include mass lost due to spillage and oxidation. It is the sum of the following:
• Mass before machining (see formula)
• Mass waste. Specified by the user with the process setup option Mass Waste (see
User Inputs for Die Casting) or calculated with the formula below.
Mass Before Machining = (Part Volume + Metal Chip Volume of Machined Features) * Material Density
Mass before machining is the part mass plus the mass removed by machining. It depends on the following:
• Part volume (obtained from GCD extraction)
• Metal chip volume of machined features: derived by summing metal chip volume for each machining operation that is applied to the part. For fully-machined features, this calculation is based on feature volume. For machine-finished features, the calculation is based on the area of the finished surface. The calculation assumes that the depth of material removed during finishing is the value specified by the cost model variable finishAllowance.
• Material density (specified by a material property)
Mass Waste = Total Gating Mass / Number of Cavities
Mass waste is the mass per cavity of that portion of the pouring volume contained in the feeder system (runners, risers, etc.). By default, it is specified by this formula. Users can override the default with the process setup option Mass Waste—see
Melting Process Inputs. Computed mass waste is a function of the following:
• Total gating mass is the mass of that portion of the pouring volume contained in the entire feeder system. It is the product of material density and total gating volume--see Total Gating Volume in
Gating System Formulas for High Pressure Die Casting or
Gating System Formulas for Gravity Die Casting.
Non-remeltable Volume = Volume Waste * (1 – Remelt Allowance)
Non-remeltable volume depends on the following:
• Volume Waste: this is Mass Waste (see formula) divided by material density.
• Remelt Allowance: the default remelt allowance is specified by the cost model variable defaultRemeltAllowancePM (1 in starting point VPEs). Users can override the default with the setup option Material Remelt Allowance Percentage.
Non-foundry Yield = Final Output Volume / (Final Output Volume + Non-foundry Scrap Parts)
Non-foundry yield affects material cost per part. It is the fraction of parts created by this process in the current production scenario that will either survive as good parts once any secondary processes are completed or will be scrapped and remelted. That is, non-foundry yield is the fraction of parts created by this process that are not discarded as un-remeltable scrap parts by a downstream process.
Note that scrap parts from downstream, secondary (non-foundry) processes are assumed to be un-remeltable; parts scrapped by foundry processes are assumed to be remelted. The presence of the node attribute inFoundryProcess indicates a foundry process.
Non-foundry yield depends on the following:
• Final output volume (product of the annual volume and number of production years, specified in the Production Scenario screen of the Cost Guide)
• Non-foundry scrap parts: number of parts scrapped by downstream, non-foundry processes