Retrieving Related Parts Information for a Specific CAD Document
This example shows you how to retrieve related parts information for a specific CAD document. Use the following GET request.
URI
GET /Windchill/servlet/odata/v1/CADDocumentMgmt/CADDocuments('OR%3Awt.epm.EPMDocument%3A167183')?$expand=PartDocAssociations($expand=RelatedParts) HTTP/1.1
* 
The related parts information is not returned with this navigation in the following cases:
When a CAD document contains model items that are related to a Part
When a CAD document has a custom association to a Part
When a CAD document drawing has a calculated association to a Part.