I know how and where to add a new unit of measure (pounds, etc...) but based on what/how we do things, knowing a products weight is critical.  Even items that we order as ''Each'' like Motors have weights.  So we need to capture from the users an items (parts) weight when they enter a Bought Component and calculate a weight  from a ...

Note: I write comments and  explanations in brackets. First of all I have to say I would draw ''Data Model for a Part'' another way (comparing to drawn on ProductEngineering/plm_parts.htm).I'd draw an arrow from Vendor to Manufactured Part instead of arrow from Manufactured Part to Vendor. The same thing with a model on ...