When using Pro/ENGINEER Wildfire 3.0 for design purposes — as opposed to modeling — it is important to specify all parameters (dimensions) of the design, and then verify whether the design specifications (any function of one or more measurements — such as mass, length, location or curvature — have been met. If they are not, then an unpredictable number of iterations are required with no guidance on the effect of changing specific parameters or in which direction to change them.

Three criteria must be defined in order to optimize a model:

• Goal: A desired result of an optimization design study. This is a solution which cannot be quantified. There can be only one goal.
• Design Constraints: Limits are measured, which are evaluated throughout a design study to ensure that their conditions are not violated. The measure may be a saved analysis or analysis feature. More than one limit may be specified for a study.
• Variable Dimensions: Variable dimensions are model dimensions — at any level of the model structure — that can be changed in order to reach a goal or identify model behavior. More than one dimension may be specified to vary for an optimization study.

In the following example, Pro/ENGINEER finds the optimal thickness of the mug by minimizing the mass of the cup and satisfying the constraint; the inside volume of the mug.

• Goal: Minimize the total mass of the mug (to minimize the force to lift the mug).
• Design Constraint: Inside volume of the mug (the space to be filled with liquid) should be less than 320000 cubic mm.
• Variable Dimension: Wall thickness of the mug is between 4.5 and 5.5 mm.

Three User-Defined Analysis Features (UDAF) will be defined in this example (Figure 1). For details on defining UDAF, refer to Suggested Technique for Using a User-Defined Analysis Feature (login required).

The first UDAF calculates the volume of the mug using the type "Model Analysis" before the inside empty volume has been created (i.e. before cut id 392 in the model tree) and creates a parameter VOLUME_BEFORE as in Figure 2.

The second UDAF calculates the volume and the mass of the mug using the type "Model Analysis" after the inside empty volume has been created (i.e. after cut id 392 in the model tree) and creates the parameters VOLUME_AFTER and MASS as in Figure 3.

The third UDAF calculates the inside empty volume by subtracting VOLUME_AFTER from VOLUME_BEFORE using the type "Relation" as in Figure 4. The relation is as follows:

VOLUME_INSIDE=VOLUME_BEFORE:FID_389-VOLUME_AFTER:FID_390

Where 389 and 390 are the feature id's, respectively. Whenever the model is changed, VOLUME_INSIDE is updated automatically.

1. Click Analysis > Feasibility/Optimization to define an optimization study and the Optimization dialog box appears.
2. Select Optimization and set the Goal to "Minimize" and select MASS:VOL_AFTER_CUT in the Goal Input Panel as in Figure 5.
3. Click Add in Design Constraints.
4. Select VOLUME_INSIDE:VOL_INSIDE for the parameter, "<" for the operation and enter "320000" for the value in the Design Constraint Input Panel as in Figure 6.
5. Click Add Dimension in Design Variables.
6. Select THICKNESS dimension by selecting the appropriate feature and enter "4.5" for the minimum value and "5.5" for the maximum value.
7. After all items are defined, click Compute as in Figure 7.

The optimization is completed with a message "The part was successfully optimized" in the message window, and three result graphs (Figures 8, 9, and 10) appear. (Graph goal, graph constraints, and graph variables are checked in the Preferences of the Options tab in the Optimization/Feasibility window).

Figure 8 shows that the mass of the mug has reached the minimum value while maintaining the design constraint. Figure 9 shows that the design constraint has been maintained, and Figure 10 shows the wall thickness of the mug has reached 5.26 mm.

8. Close the Optimization dialog box by clicking Close and the Confirmation dialog box appears as in Figure 11.
9. Click Confirm and the model is updated with the new wall thickness value.