How aPriori Assigns Holes and Voids to Slides and LiftersaPriori analyzes a part’s unthreaded holes and voids in order to determine which, if any, must be handled by a slide or lifter. For those GCDs that do require a slide or lifter, aPriori determines which can be grouped together onto a common action. In this way, aPriori can determine the number and size of the slides and lifters required for the part’s mold.
Each resulting slide or lifter is represented by a GCD with a name such as SlideBundle:1 or SlideBundle:2, and so forth. These GCDs appear in the Geometric Cost Drivers pane under the Slide Bundles or Lifter Bundles, which appear under the Volume node.
By default, an unthreaded hole or void is assumed to require a slide or lifter if and only if it is obscured, that is, if and only if it is not accessible from the draw direction. For SimpleHoles, MultiStepHoles, Voids, and ComboVoids, you can override this default, and specify that an obscured feature does not require a slide or lifter (for example, because it is shallow and has a smooth opening, and so can be safely pulled).
Follow these steps to specify that a feature does not require a slide or lifter:
1 Click the GCD either in the Component Viewer or the Geometric Cost Drivers pane.
2 Double click the Property Result field for the property Excluded From Bundling, and select true.
3 Re-cost the scenario.
This section contains the following subsections:
Slide Bundling Criteria
A group of GCDs can form a bundle and be handled by a single slide only if there is a direction, D, (represented by a SetupAxis) such that all the following hold:
• All the GCDs are accessible from D.
• D is sufficiently close to orthogonal to the draw direction.
The cost model variable drawDirectionOrthogonalEpsilonForSlides specifies the threshold for being sufficiently close; this value is 30 degrees in aPriori starting point VPEs.
• For each GCD, if access to the GCD from D is obstructed, the obstruction is sufficiently far from the GCD.
The cost model variable minimumSlideClearance specifies the threshold for being sufficiently far; this value is 196.75mm in aPriori starting point VPEs.
The distance between the GCD and the obstruction is the Distance to Obstruction property of the Is Accessible From relation whose value for First is the GCD and whose value for Second is the SetupAxis that represents D.
• Any two adjacent GCDs are sufficiently close (in the direction orthogonal to both D and the draw direction).
The cost model variable maxGcdPitch specifies the threshold for being sufficiently close; this value is 50.8mm in aPriori starting point VPEs.
• For any two adjacent GCDs that do not share the same volume, the distance between them along direction D is sufficiently small.
The cost model variable maxSlideDepthPitch specifies the threshold for being sufficiently small; this value is 25.4mm in aPriori starting point VPEs.
The distance measured is between the GCD fronts (that is, the side of the GCDs on which the slide enters).
• Each GCD is sufficiently close to the part edge. That is, for each GCD, the distance from the GCD along D to the part edge is sufficiently small.
The cost model variable maxGcdDistanceFromPartEdge specifies the threshold for being sufficiently small; this value is 25.4mm in aPriori starting point VPEs.
There is an exception when the slide is behind another slide (that is, there is a line in direction D that intersects both the slide under consideration and some other slide closer to the part edge). In such a case, distance to part edge is ignored.
Distance to part edge is the value of the Distance to Shadow Border property of the Is Accessible From relation whose value for First is the GCD and whose value for Second is the SetupAxis that represents D.
• GCDs have sufficient clearance to accommodate the slide’s stroke length and avoid die lock. That is, the depth (along D) of the deepest GCD (plus some extra depth for the action base) is less than the smallest distance between a GCD and the obstruction that is closest to its associated GCD.
• All GCDs can be manufactured by a slide that does not obstruct any volume beneath the slide. The faces under a slide must not form any kind of hook; otherwise the slide would not be pullable.
• The slide is not too long (in the direction orthogonal to both D and the draw direction).
The cost model variable maxActionLength specifies the threshold for being too long; this value is 500mm in aPriori starting point VPEs.
Slide length is the total GCD span in the direction orthogonal to both D and the draw direction.
Lifter Bundling Criteria
aPriori’s cost model assumes that an unthreaded, obscured hole or void requires a lifter only if it cannot be accommodated by a slide.
A group of GCDs can form a bundle and be handled by a single lifter only if there is a direction, D, (represented by a SetupAxis) such that all the following hold:
• All the GCDs are accessible from D.
• D is sufficiently close to orthogonal to the draw direction.
The cost model variable drawDirectionOrthogonalEpsilonForLifters specifies the threshold for being sufficiently close; this value is 10 degrees in aPriori starting point VPEs.
• For each GCD, if access to the GCD from D is obstructed, the obstruction is sufficiently far from the GCD.
The cost model variable minimumLifterClearance specifies the threshold for being sufficiently far; this value is 64.77mm in aPriori starting point VPEs.
The distance between the GCD and the obstruction is the Distance to Obstruction property of the Is Accessible From relation whose value for First is the GCD and whose value for Second is the SetupAxis that represents D.
• Any two adjacent GCDs are sufficiently close (in the direction orthogonal to both D and the draw direction).
The cost model variable maxGcdPitch specifies the threshold for being sufficiently close; this value is 50.8mm in aPriori starting point VPEs.
• For any two adjacent GCDs that do not share the same volume, the distance between them along direction D is sufficiently small.
The cost model variable maxLifterDepthPitch specifies the threshold for being sufficiently small; this value is 12.7mm in aPriori starting point VPEs.
The distance measured is between the GCD fronts (that is, the side of the GCDs on which the lifter enters).
• GCDs have sufficient clearance to accommodate the lifter’s stroke length and avoid die lock. That is, the depth (along D) of the deepest GCD (plus some extra depth for the action base) is less than the smallest distance between a GCD and its associated obstruction (if any).
• The lifter is not too long (in the direction orthogonal to both D and the draw direction).
The cost model variable maxActionLength specifies the threshold for being too long; this value is 500mm in aPriori starting point VPEs.
Lifter length is the total GCD span in the direction orthogonal to both D and the draw direction.
The model costs as if a dedicated lifter handles each hole or void that is entirely inaccessible (because it contains an interior undercut).
Further Bundling Criteria—Breaking Ties
If multiple directions of access are apprioriate for a bundle, aPriori prefers the direction that provides the smaller tool length.
If multiple directions of access providing the same tool length are apprioriate for a bundle, aPriori prefers the direction that provides the smaller distance to the part edge.
If some GCD can be handled by multiple different actions of the same type, it is bundled so as to minimize the maximal width/depth gap between GCDs in each action.
Determining Action Size
Once aPriori forms the bundles, each bundle is categorized as small, medium, or large (based on the number and volume of the GCDs it contains). This helps determine the material and labor cost to produce the bundle’s associated action. Labor costs take into account the cost of design, machining, assembly, and tool trade certification for each action.
Bundle size (small, medium, or large) is determined as follows:
slides | lifters | inserts (inch^3) | grill inserts | ||||
standard size (inch^3) | gcd based size (mm^3) | standard size (inch^3) | gcd based size (mm^3) | standard size (inch^3) | gcd based size (inch^3) | ||
small | 75 | * | 75 | * | 1 x 1 x core plate height | 32 | gcd area x 2 inches |
medium | 1100 | * | 500 | * | 3 x 3 x core plate height | 128 | gcd area x 2 inches |
large | 2000 | * | 1500 | * | 6 x 6 x core plate height | 288 | gcd area x 2 inches |
* | Bundle volume with approximately 1 inch added to length | ||||||