Casting - Investment

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 Thickness (can impact machine selection, tooling costs, material costs, cool time, machining times and costs, and design guidance): This release improves assumptions about which features are cast and which features are machined, and improves the calculation of part thickness values (Min Thickness, Max Thickness, and Avg Thickness).

  In previous releases, geometry extraction recognized the following two possibilities for manufacturing 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 SimpleHole and RingGCDs.

  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 these changes, Fully Burdened Cost may increase slightly in some cases. Increases of less than 3% were observed in 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.

  Note:

  If you are using the latest cost model version, your cost model logic is not compatible with the previous extraction behavior; you must not disable the new extraction behavior. Ensure that the site variable isCastMachinedExtractionEnabled is set to true (the default).

• Wall Thickness, Hole Diameter, and Ring Width Thresholds (can impact tooling costs, material costs, machining times and costs, 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 2.00 to 2.40)
  • minCastableHoleWallThickness (changed from 0.76 to 0.50)
  • minCastableRingWidth (changed from 2.00 to 2.40)
  • 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.

• Turning Axis Extraction (can impact routing and operation assignment): In the previous release, in rare cases, aPriori extracted turning axes for a part and routed it to a turning process even though only a small portion of the part's features could be turned. In this release, by default, aPriori extracts a turning axis only if at least 5% of the part's surface area is turnable. Administrators can customize this threshold with the new site variable minTurnAxisAreaRatio (0.05 by default).

  As a result, routings and costs may change (for example, a part that was erroneously routed to a turning process in the previous release might be routed to milling in this release).

  Note:

  To restore the behavior of the previous release, set the minTurnAxisAreaRatio to 0.00.

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.

• 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.