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Casting - Sand

Geometry or Cost Engine Changes that Could Impact Configured Digital Factories

The following changes might impact costing, even for Digital Factories that use earlier cost model versions.

  • Partially Cast Features and Part Maximum Thickness (affects machining operation assignment, casting costs, and design guidance): This release improves assumptions about which features are cast and which features are machined, and improves the calculation of part maximum thickness.

    In previous releases, geometry extraction recognized the following two possibilities for part features:

    • Made by casting
    • Made by machining

    If a hole, for example, was recognized as uncastable because its walls were too thin, the hole was assumed to be made entirely by machining. In this case, the feature's Is Castable property was set to false.

    In this release, geometry extraction recognizes three possibilities:

    • Cast
    • Machined
    • Cast and Machined (that is, partially cast and then partially machined)

    If a large hole, for example, is recognized as uncastable because its walls are too thin, it is assumed to be partially cast, where the cast feature has thickened walls compared to the final feature. Subsequent rough milling is assumed to remove the extra wall thickness.

    These changes apply to SimpleHoles, Rings, RingedHoles, and ComboVoids.

    Users can override a feature's default manufacturability determination (Cast, Machined, or Cast and Machined) by editing the feature's Manufacturability property in the Geometric Cost Drivers pane. The property Is Castable has been removed.

    As a result of these changes, thickness values and machining operation assignments might change. Some parts are now determined to require additional machining, increasing cycle time and expendable tooling cost. As a result of all the changes in this process group, Fully Burdened Cost increased on average by 12.0% with automated routings and 23.5% with manual routings, for a set of test parts

    Note:

    Scenarios created with previous releases of aPriori are not compatible with the latest cost model. Users of the latest cost model must re-extract GCDs using the latest release of aPriori.

    Note:

    If you are using a cost model version from a previous release, your cost model logic is not compatible with the new extraction behavior. Set the site variable isCastMachinedExtractionEnabled to false. This restores extraction behavior that is compatible with the old cost model logic. See also Wall Thickness, Hole Diameter, and Ring Width Thresholds, below.

See also Partially Cast Features in Cost Model Changes that Do Not Affect Configured Digital Factories.

  • Wall Thickness, Hole Diameter, and Ring Width Thresholds (affects machining operation assignment, tooling cost, material cost and yield, cycle time, and design guidance): This release improves the accuracy of the thresholds that determine a feature's Manufacturability classification (Cast, Machined, or Cast and Machined). The thresholds used for a given part now depend on the part's material type, as specified in certain lookup tables. If the part's material is not found in the appropriate lookup table, the threshold is specified by one of a number of site variables. This release improves the default values for some of these site variables, and introduces some new ones:

    • minCastableHoleDiameter (changed from 6.40 to 4.80)
    • minCastableHoleWallThickness (changed from 5.00 to 3.00)
    • minCastableRingWidth (changed from 6.40 to 4.80)
    • minCastMachinedHoleDiameter (new)
    • minCastMachinedRingWidth (new)

    Users can disable the use of material-specific thresholds, in which case the thresholds are specified by these site variables. To disable material-specific thresholds, set the site variable enableMaterialTypeGCDExtraction to false.

    Note:

    To restore the behavior of the previous release, set both the site variables isCastMachinedExtractionEnabled and enableMaterialTypeGCDExtraction to false, and set the site variables minCastableHoleDiameter, minCastableHoleWallThickness, and minCastableRingWidth back to their original values--see above.

    Thickness Algorithm (Impacts Machine Selection, Machining Operation Assignment, Tooling Costs, Material Costs, and Design Guidance): This release improves the algorithm used to determine part thickness by using smaller voxels and more inclusive voxel samples.

    Note:

    To restore use of the previous thickness algorithm, set the site variable castThicknessAlgorithm to Legacy Voxel-Based.

Bug Fixes or Small Improvements to Prior Cost Model Versions

The following changes might impact costing for Digital Factories that use earlier cost model versions.

  • NO IMPACT

Cost Model Changes that Do Not Affect Configured Digital Factories

The following changes do not affect costings with Digital Factories that use earlier cost model versions. The changes are available only in the latest cost model version.

  • Machining Routing: In the previous release, users manually included machining for uncastable features. In this release, aPriori automatically includes secondary Machining for GCDs whose Manufacturability is Machined or Cast and Machined (provided This part may be machined is selected in the Production Scenario tab of the Cost Guide). See also Geometry or Cost Engine Changes that Could Impact Configured Digital Factories).
  • Partially Cast Features (impacts operation assignment): This release supports partially-cast features (see Geometry or Cost Engine Changes that Could Impact Configured Digital Factories). In the previous release, the cost model assumed that each part feature was either made entirely by casting or entirely by machining. In this release, some features previously assumed to be entirely machined or entirely cast may now be assumed to be partially cast and then partially machined. This change can affect both casting and machining costs.
  • Cool Time for Manual Moldmaking (impacts cycle time): This release corrects a problem with the cool time calculation for manual moldmaking processes. As a result, times and costs can sometimes increase. Fully burdened cost was observed to increase by up to around 20% for some parts.