4.2.5 CHECKLISTING

4.2.5.1 The "Boss_Eval" Hypothesis

Currently, there are five rules that have the Boss_Eval hypothesis. The rule of Figure 35 represents the typical Check rule for a boss. It states that if the root diameter of a boss is greater than two-thirds the thickness of the adjacent wall, then there is potential for a sink.

The <> brackets indicate the creation of a list. Initially, all Boss features are members of the list. Eventually, the list gets narrowed down to just those features which allow the conditions of the LHS to remain true. (This is best represented by larger rules with several LHS conditions.)

Figure 35 Rule "Boss_Eval_Sink_Potential"

(@RULE= Boss_Eval_Sink_Potential

@COMMENTS="top diam > 2/3 wall thck";

@WHY="diam too thick for wall";

(@LHS= (> (<|BOSS|>.boss_top_diameter /(0.67*<|BOSS|>.feature_wall_thickness)) (1)) )

(@HYPO= Boss_Eval)

(@RHS= (Let (<|BOSS|>.x_sink) (TRUE)) ) )

Finally, if at least one or more Bosses allow all the conditions on the LHS to be true, Boss_Eval for the rule is true and the RHS actions may be taken.

Note that in the above rule, no diagnostic output is yet put out. Rather, the RHS dictates that a feature property, known as a checklist property, is marked as true.

For every feature or part evaluation rule, there is a corresponding checklist property. By convention, these properties are prepended with "x_". Table 9 contains a list of the five Boss_Eval rules along with the corresponding checklist property for each.

Table 9 Boss Evaluation Rules and Checklist Properties

Rule Hypothesis Property

Boss_Eval_Unejectable |Boss|.x_drft

Boss_Eval_Sink_Potential |Boss|.x_sink

Boss_Eval_Core_Unejectable |Boss|.x_core

Boss_Eval_Bottom_Plane_Not_Perpendicular |Boss|.x_bot_k

Boss_Eval_Boss_Core_Pin_Too_Long |Boss|.x_core_long