Visualizing the Air Space of a Complex PSU

By Ceferino Sanchez of ASTEC Power, a Division of Emerson Network Power

Both thermal engineers and the mechanical design team can benefit being able to visualize how densely populated the power supply unit (PSU) is. Creating a free area ratio (FAR) plot along the length of the PSU is one way to address this need. The basic idea is to create the air part by cutting out a merged solid representation of the PSU and plotting its cross-sectional area along the length of the unit by performing a user-defined analysis (UDA).

 This technique requires the Advanced Assembly Extension (AAX) and the Behavioral Modeling Extension (BMX). Also necessary is a workstation with sufficient RAM. It may be necessary to have the /3GB switch on Windows XP Professional. If not, use the 64-bit version of Pro/ENGINEER. 

Creating a Merged Solid Shrinkwrap of the PSU

The first functionality to be used is available in AAX. The following steps were adapted from  <PROE_LOADPOINT>html\usascii\proe\aax\
     to_create_a_merged_solid_exported_shrinkwrap_model.htm.

1.     Retrieve the PSU assembly as the source model.

2.     Click File, Save a Copy. The Save a Copy dialog box opens.

3.     In the Type dropdown list box, click Shrinkwrap (Fig. 1).

4.     In the Creation Method area of the dialog box, select Merged Solid.

5.     In the Quality area of the dialog box, specify the quality level for the system to use when identifying components that will contribute to the shrinkwrap model. Enter an integer in the range of 1 to 10 (default = 1). Since the accuracy of the FAR plot is important, I advise using the highest quality possible (10).

6.     In the Special Handling area of the dialog box, select or clear the following options:

• Auto Hole Filling (selected by default). Unselect this since the FAR plot accuracy will be affected with filled holes done by the system.
• Ignore Skeletons (selected by default). The system does not include skeleton model geometry when creating the shrinkwrap model.
• Ignore Quilts (selected by default). The system does not include external quilts in the shrinkwrap model.
• Assign Mass Properties. The system assigns the mass properties of the original model to the shrinkwrap model. 

7.     In the Output File Name area of the dialog box, specify the export output. The system assigns the shrinkwrap model a default file name based on that of the source model. Accept the default file name in the format model_name_sw0001 or enter a new name for the shrinkwrap model.

8.     Click Preview to obtain graphical and textual feedback about the subset of information that will be captured in the shrinkwrap model (Fig. 2). The message window provides information about how many components are included and excluded from the representation, in the format "X of Y components have been selected." You can zoom in and select unselected components to include, or you can undo selections using the Select Components button.

9.     Click Create. The system copies a subset of information from the source model to create a shrinkwrap model, saves the new part to disk, and displays it in its own window (Fig. 3). The subset consists of solid geometry consisting of all collected components from the source model.

10.  Click Close. The Create Shrinkwrap dialog box closes.

Figure 1. Shrinkwrap Dialog Box

Figure 2. PSU Assembly

Figure 3. Merged Solid Shrinkwrap Part of PSU Assembly

Note: It’s advisable to enable the configuration option enable_absolute_accuracy and set it to yes.  You can set the part accuracy to 0.001 mm absolute to avoid problems in the cutout later on. 

Making the Cutout

At this point you need to create an assembly, which you can arbitrarily name PSU_model_FAR.asm. These are the intermediate steps prior to using the cutout functionality.

1.     Assemble the merged solid shrinkwrap part.

2.     Create and assemble the air.prt, which consists of a protrusion feature flush to the width, height and length of the PSU.

3.     With the air.prt activated, click on Insert, Shared Data, Cutout and then pick the merged solid shrinkwrap part of the PSU.

If there are problems with the cutout, other than enabling absolute accuracy, you can match the accuracy of the air.prt with the merged solid shrinkwrap of the PSU.

Performing the User Defined Analysis

By calculating the cross-sectional area of the air.prt, the FAR can be derived by dividing this by the total area of the PSU cross-section normal to the airflow direction. The following steps were adapted from <PROE_LOADPOINT>\html\usascii\proe\bemod\
example__analyzing_the_cross_section_of_a_pipe.htm and <PROE_LOADPOINT>\html\usascii\proe\bemod\
to_create_a_user_defined_analysis.htm

1.     Open the air.prt or activate it if in session.

2.     Create a field point on the trajectory curve by clicking Insert, Model Datum, Point, Field (Fig. 4).

Figure 4. Field Point

3.     Create a datum plane through the field point normal to the airflow direction (Fig. 5).

Figure 5. Datum Plane Through Field Point Normal to Airflow Direction

4.     To create an analysis feature to measure the cross-section of the pipe, click Insert, Model, Datum, Analysis.

5.     In the ANALYSIS dialog box, enter the name of the analysis, air_area, and select Model Analysis as the type of the analysis (Fig. 6).

Figure 6. First Page of Analysis Dialog Box

6. Click Next to go to the second page and select a parameter that you want to create (Fig. 7).

Figure 7. Second Page of Analysis Dialog Box

7. Select X-Section Mass Properties as the type of measure.

8. Place a checkmark in front of Use Plane, and choose the name of the datum plane to create the cross-section.

9. Click Compute to the mass.

10. Click Close.

11. Under Result params, choose the parameter XSEC_AREA and select Yes to create this parameter (Fig. 8).

Figure 8. Third Page of Analysis Dialog Box

12. Click OK.

13. Create a UDA construction group by grouping all required features and parameters. Click Edit, Feature Operations, Group, Local Group. Specify a name for the group (Fig. 9).

Figure 9. Local Group

14. From the model tree, select the field point, the datum plane through the field point, and the analysis feature (the last item).

15. Create a user-defined analysis using the construction group you have just defined. Click Analysis, User-Defined Analysis.

16. Under Type, select a Construction group.

17. Under References, accept the default references used by the feature.

18. Under Parameters, select the analysis feature parameter you want to compute (in this case, XSEC_AREA).

19. Specify where to perform calculations by accepting the default (Entire Field) from the domain list. The calculation will be performed on the entire domain where the field point is located (in this case, the entire trajectory curve that is the edge along the airflow direction).

20. Under Computation Settings (Fig. 10), define the resolution by clicking the appropriate icon.

Define the resolution by setting the distance (0.5mm is acceptable in the case of PSUs) between two adjacent points in the model units. Depending on the length of the PSU and your processor, this will take some time.

 21. Under Computation Settings, also set any of these options:

• Max/Min Refinement. Obtains more accurate results for the minimum and maximum values without increasing the density or accuracy. This option is available only for the Entire Field domain.
• Create Graph. Shows results in a graph window. If you have MS Excel, set the configuration option bm_graph_tool to excel_linked, which opens a standalone Excel window when the graph is created.
• Dynamic Update. Pro/ENGINEER updates the results automatically. You need not choose Compute to update. 

Figure 10. UDA Dialog Box

22. Under Results, click:

• Settings. Sets the scale and density of the display and specify calculation options (Fig. 11). For UDAs with the field point on an edge or curve, you can set the scale and density. If the field point references a surface or a quilt, you can set increment (linear, logarithmic, or two-color), spectrum (upper and lower limits, and sensitivity), and accuracy (low, medium, high, or very high).
• Compute. Generates the results of the analysis (Fig. 12). The results appear in the box under Results, and can be a porcupine display accompanied by a graph (if the field is a curve or an edge) or a shaded display (if the domain is a surface or a quilt).
• Clear. Erases the display of the results.
• Choose OK to close the dialog box.

Figure 11. UDA Settings

Figure 12. UDA Display

23. Click the Saved Analyses bar to expand the dialog box for the functions related to saving analyses.

24. To save this analysis in an analysis feature, click Add Feature and enter the name for the feature. A new analysis feature appears in the model tree.

25. Click Close.

In an Excel spreadsheet, you can add field names such as width, height and length of the PSU.  You can also easily compute derived fields such as area, X-distance on the PSU and FAR (Fig. 13).

Figure 13. FAR Plot on the Spreadsheet

Ceferino Sanchez is a lead engineer, thermal engineer and Pro/E administrator at ASTEC Power, a division of Emerson Network Power in Quezon City, Philippines. He can be reached by email at ceferinosanchez@astec-power.com.