What are circular references in a top down design?

I just wanted to share some information on the circular references, hoep this will be useful for your day to day design job








As the name indicates a top down design always starts from the top and flows down to bottom. I give a simple example below.














The advantage of Top down design is, here on placing the component B over A, we can take the references from A to add features in B. But never go and take references from B to add a feature in A. In that case there forms a circular reference.

Refer the image below for better understanding









We can see a dependency from A to B and B to A which is not desirable. For an assembly structure as shown below

For adding features in Component 2, we can refer Component-1 or for adding features in Component- 4, we can refer Component -3/2/1 but not Component-5.

For the below assembly

My first component in the assembly is REAR_PLATE.PRT. Next I am going to assembly the second component FRONT_PLATE.prt.








Now I am going to create the Flange Holes in REAR_PLATE by referring the FRONT_PLATE

Now exit the feature tool and regenerate the assembly.

We can see the Flange Holes in the REAR_PLATE model. Now go to the working directory, you can see a file named your assembly name.crc. CRC file with the name of your assembly. Go and open the .crc file using a notepad or wordpad. You can see something like this

Add the column Feat# to the model tree in ProE.

Now read the crc file. The file says Feature number 6 in the above assembly refers to Feature Number (Feat#) 27 in the model REAR_PLATE. Expand the REAR_PLATE.prt and edit the feature number 27.

Go to the sketch and you can see all the references from the model FRONT_PLATE.PRT. Remove all the references to FRONT_PLATE.PRT and give references from the parent model.

No references to FRONT_PLATE.

Go to the working directory and delete the crc file. Go to the ProE assembly and regenerate. Check the working directory you can no more find a crc file in there.