Manufacturability

During geometry extraction, aPriori identifies features that cannot be fully cast (because the feature is too small or its walls are too thin) and classifies them as either partially or fully 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.

In addition to affecting machining operation assignment, the classification (as fully cast, fully machined, or partially cast and partially machined) also affects the determination of the part's Max Thickness, Min Thickness, and Avg Thickness, which characterize the walls of the cast part (before any machining). These values can affect machine selection, material costs, tooling costs, and design guidance.

This section has the following subsections:

• The Manufacturability Property

• Manufacturability Thresholds

• Machining Operation Assignment

• Modifying Machining Operation Assignment

The Manufacturability Property

Features that might be partially cast include SimpleHoles and Rings. Geometry extraction classifies SimpleHoles and Rings by setting the geometric property Manufacturability to one of the following values:

• CAST: indicates the feature's diameter (or ring width) and wall thickness are large enough for the feature to be fully cast.

• CAST_AND_MACHINED: indicates the feature's wall thickness is too small for the feature to be fully cast, but the feature's diameter (or ring width) is large enough for it to be partially cast.

  Note: The minimum diameter for a partially cast hole is larger than the minimum diameter for a fully cast hole, since the diameter of a partially cast hole is effectively reduced by the thickening of the hole walls. The reduced diameter must meet the requirement for a fully cast hole. See Manufacturability Thresholds.

• MACHINED: indicates that at least one of the following holds:

  • Feature's diameter (or ring width) is too small for the feature to be fully cast.

  • Feature's wall thickness is too small for the feature to be fully cast, and the feature's diameter (or ring width) is too small for the feature to be partially cast (see Note, above).

You can override aPriori's manufacturability classification for a given GCD by editing the GCD's Manufacturability property value in the Geometric Cost Drivers pane. See Modifying Machining Operation Assignment.

Manufacturability Thresholds

During geometry extraction, minimum castable wall thickness, hole diameter, and ring width are looked up by the part's material type in the following lookup tables:

• tblWallThickness

• tblMinHoleDiameter

If the material type is not found in the lookup tables, geometry extraction uses the thresholds specified by the following site variables:

• minCastableHoleDiameter (2.40mm in starting point Digital Factories)

• minCastableRingWidth (2.40mm in starting point Digital Factories)

• minCastableHoleWallThickness (0.50mm in starting point Digital Factories)

The minimum hole diameter or ring width for a partially cast feature is specified by the following site variables:

• minCastMachinedHoleDiameter (2.40mm in starting point Digital Factories)

• minCastMachinedRingWidth (2.40mm in starting point Digital Factories)

The Component GCD properties Min Castable Wall Thickness, Min Castable Hole Diameter, and Min Castable Ring Width indicate the thresholds used during geometry extraction.

You can disable the use of material-specific thresholds by setting the site variable enableMaterialTypeGCDExtraction to false, in which case the thresholds are specified by the site variables listed above.

Machining Operation Assignment

Features that are classified as MACHINED or CAST_AND_MACHINED are automatically routed to appropriate roughing operations in the Machining process group.

For a SimpleHole or Ring GCD, the property Min Wall Thickness characterizes the walls of the feature as modeled, that is, the walls of the finished feature (after any machining). So, for a partially cast feature, the thickness of material removed by machining is assumed to be the difference between the Min Wall Thickness value for the feature and the minimum castable thickness (which is Min Wall Thickness for the Component).

A blind hole that is uncastable because of its length-to-diameter ratio may be routed to machining even if the value of its Manufacturability property is CAST. The threshold is specified in the lookup table DTCLimits.

In some cases GCDs are assumed to be fully machined despite being classified as CAST_AND_MACHINED (according to the Manufacturability property):

• If the current routing is a 3-Axis Lathe or Mill Turn routing, CAST_AND_MACHINED SimpleHoles are assumed to be fully machined when the hole axis is not a turning axis.

• If the current routing is a Drill Press Routing, CAST_AND_MACHINED SimpleHoles are always assumed to be fully machined.

• CAST_AND_MACHINED Rings that are assigned to Plunging or Multiplunging are always assumed to be fully machined.

Modifying Machining Operation Assignment

You can modify a GCD's operation sequence by overriding aPriori's manufacturability classification for the GCD. Edit the GCD's Manufacturability property value in the Geometric Cost Drivers pane. Re-costing the part then triggers recalculation of the GCD's operation sequence (as well as recalculation of thickness values and slide bundling).

Note that if you edit a GCD's operation sequence with the Operation Sequence Selection dialog, the new sequence must be compatible with the GCD's Manufacturability value. If it is not, the GCD will fail to cost. So to remove roughing from the operation sequence for a given GCD, set the GCD's Manufacturability to CAST (rather than using the Operation Sequence Selection dialog). Similarly, to include roughing in the operation sequence for a GCD when roughing was not previously included, set the GCD's Manufacturability to MACHINED or CAST_AND_MACHINED.