CATIA V5 Tip: Using the Comparison Command in a Drawing Environment

Rand 3D

By Trisha West


Investigating the differences between old and new revisions of items in CATIA can be difficult especially when the changes are very minute. The comparison command is an excellent tool to help visualize these changes. For comparisons on parts and products, check out the first part of this blog by my colleague, Amy Rath: 

Now let’s focus on applying this concept to a drawing environment. Below is an older revision CATIA part file and it’s associative drawing.


The Compare Drawings tool compares two cgm format documents to detect differences between them. This requires the original drawing to be saved as a .cgm format. This is easily done with a File --> Save As or Save Management.


The new revision of this handle has some changes in the reverse/forward switch area.


Once a design change is made to the CATIA part file, the drawing will need to be updated. The drawing will register that it is currently displaying the older revision of the part file, as indicated by the icons located on the drawing views in the specification tree. To refresh the drawing, simply select the “update” icon and save the drawing again as a cgm file (make sure to make a change in the file name).


Open the original cgm file and ensure that you are in the DMU 2D Workbench.


Select on the “Compare Documents” icon in the DMU 2D Tools toolbar and select the second cgm file you saved. 


The drawing compares will immediately show up. In the case of a drawing where the scales and drawing views are in the same location, then the comparison will not need any adjustment. The color differentials by default are red, green, and blue (area of the drawing where there in no change).



Now let’s look at a more complicated scenario.  If the second drawing you want to compare is not simply an updated version of the first drawing, you may find that the drawing view you wish to compare is at different scale or are at different location on the sheet. Below is such an example. The same general area is created within the drawing as a detailed view for both an older and newer part. These detailed views are at different scales and are located at slightly different locations on the drawing sheet.


When you do the comparison as previously discussed, the resulting picture doesn’t align the geometry correctly, so the compare tool isn’t of benefit.


To fix this, let us first deal with the scaling issue. Clicking on “Calibrate” and adjust the zoom using the resizing option.


After resizing, we can fix the location misalignment with another calibration using superimposing.


To superimpose, you want to select on items that you know should match up. In this case, I know that both parts have the same “F” embossment so I selected on those edges.



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