Our start part here have a real number parameter for specific_gravity and the density is driven by relation based on that parameter. There are a couple of nice things about that:
* The specific gravity is unitless, so you enter the same thing regardless of your units. * Pro|E does the math to convert to density, no fat finger errors on the calculator. * We deal in plastics a lot and the specific gravity is commonly available on the spec sheets.
The down side is that the conversion factor in the relation is different depending on the units, so if a part is built in english units and converted to metric, the density will be off if you don't update the relation. If the density is entered directly, it updates when the units are changed.
I'd like to update our start parts so that we can continue to use the specific gravity but have the density still update if the units are changed. I was thinking that by using parameters with units assigned, the relations would work. I haven't had any luck, however. Assigning a unit to parameters doesn't seem to have effect.