1. How to “Black Box” a Model A large model usually consists of sub-assemblies that are built before being attached to the main assembly. In 3DCS, the model also has to build these sub-assemblies, slowing the analysis down. Therefore, 3DCS has a process to turn these sub-assemblies into “black boxes.” The term black box refers to an assembly that is treated as a single part with all variation applied at the assembly level. Because the simulation no longer needs to move the sub- assembly parts together or apply part level tolerances, it usually runs significantly faster.

2. Sub-Asm Level Tolerances In some cases, the sub-assembly tolerances will already be defined. If they are, they can simply be applied at the sub-assembly level with no other part-level tolerances or moves needed.

3. Sub-Asm Level Tolerances If the tolerances are not defined, the sub-assemblies must be built as complete 3DCS models. The features used at the full assembly level will be measured in the separate models and this measure data will be input (with a dev file) as tolerances in the full assembly model. SubAsm A Model Sub A.dev file Pt1 x,y,z Pt2 x,y,z SubAsm B Model Sub B.dev file Pt3 x,y,z Pt4 x,y,z Full Asm Model

4. Limitations The CMMDEV routine can only input point deviations. Therefore, no relationship between a hole or pin size and a point location can be established. For example, 3DCS cannot give the sub-assembly features MMC (bonus) tolerances. The Sensitivity Analysis cannot analysis the User- DLL tolerances, including the CMMDEV routines. A sub-assembly change requires two model runs to generate new full assembly results. The “black box” features must be represented by points.

5. Steps 1.Determine and create the sub-assembly models that will be used as “black boxes” in the Full Asm model. 2.Pick and record an instance name for each “black box.” 3.Read the CMM Data section of the 3DCS Help Manual.

6. Steps 4.Open one of the sub-assembly models. 5.Identify relevant points. These are the features needed at the Full Asm level. The points names must be unique. 6.Select the Export to MS Excel button. 7.In the Points tab, delete all non-relevant points. 8.For every point, rename the PART to the instance name that will be used in the Full Asm model. 9.Correct the #Pts and Index columns. 10.Save the Excel file. 11.Repeat with the other sub-assembly models.

7. Steps 12.Open one of the sub-assembly models. 13.Turn output of all measures off. 14.For each relevant point, use Measure Generator to create X, Y, and Z measures in the top-level assembly. 15.Nominal Build and run the model. 16.In the Histogram window, use File, Save as *.Dev to create the deviation file. 17.Create a CGR file of the sub-assembly. 18.Repeat with the other sub-assembly models.

8. Steps 19.Start a new 3DCS model. This will be the Full Asm model. 20.Insert a CGR file for each “black box.” 21.Rename the new components with the instance names previously chosen. 22.Update model. 23.Save this model.

9. Steps 24. In the Full Asm model. 25.In the Excel tab in Preferences, ensure the Merge option is checked. 26.Select the Export to MS Excel button. 27.Open one of the previously saved Excel files. 28.Copy the data in the Points tab in the saved file and Paste it into the new file. 29.Select the Import from MS Excel button. 30.Verify the points have been imported correctly. 31.Repeat with the next saved Excel file.

10. Steps 32.After all the points have been imported in the Full Asm model: 33.Re-establish dynamic points 34.Add size tolerances. 35.Add moves and measures between the “black boxes.” 36.Add CMMDEV tolerances to the points in each black box. Use the DEV files created earlier. 37.Validate and Save the model.