Starting with a flat pattern and adding bends is generally a bad idea and can lead to downstream problems.
For example, if you modeled an L-shaped part by making the flat plus1 bend. Here are some of the downsides:
<LI>Adjusting length of legs not trivial (controlled by flat dimension)
<LI>Changing thickness of part will change length of legs
<LI>Changing your bend table (or sending to supplier who might apply their own) will change the lengths of the legs
<LI>Changing the bend radius will alter the leg lengths</LI>
This is great info - I have several coworkers that employ this method and this will be great information to *hopefully* influence their practices. Normally I don't care how others model for the most part, but in this group ownership of designs change a lot and I don't want to be stuck with poor models.
Keep the cons (and pros, if there are any) coming.
In ProE, even more than in other CAD, it is best to start as close to the final design as possible. Youneed of course to keep this reasonable, trying to do too much in one go can create more problems than it solves. But, as mentioned above, it is preferable to design an angle with the final dimensions it should have and flatten it afterwards, than the other way around. That's commonly known as "capturing design intent".
To design a sheet metal box it is far easier to start in part with a block, cut and "thin shell" it, and convert it to sheetmetal than to start with a plate and try to add mitered flanges around it.
Inserting bends is a good idea when only part of the contour has to be bent and the rest has to keep straight. If you want the length of leg to be controlled then design it larger before bending and cut off to desired length after bending. The flat pattern will show the amount of material needed to create the appropriate bend, no need to calculate it beforehand.
I do have a case where starting from a flat pattern is appropriate. We were transfered some products that were designed (poorly) in AutoCAD as part of an acquisition. All the design data is strictly 2D and all the parts are already tooled and in production. There weree no assembly drawings. So I have modeled all the parts in Pro/E including many terminal blades. These get insert molded into bobbins and then several bends are created at different stages of assembly. So in this case, I modeled the blades as flat patterns and then added bends to see where they end up in the final assembly. Obviously, this is backwards and not how I would design a new part from scratch.