Hey, does anyone know why none of the parts on the first base website constrain in inventor. Once you put one constraint on each part it gives you errors for every subsequent one. This makes it very difficult to lock parts in place. If anyone has any idea why this is happening please let me know ASAP. Thank you.
Which parts are you talking about? We haven’t had problems with any metal parts but some of the electronics parts are molded so that their sides are not orthogonal. You can’t use multiple flush constraints - you can usually only use the bottom. Make holes and constrain them that way. While it may seem like a bit more work now, at least you won’t forget to put in all the parts later. 
We use a lot of 8020 and there is only a tiny flat that is suitable for flush constraints. Also, Inventor 2009 seems to take much longer than 2008 did to calculate constraints. It helps to pick the least complicated part first to minimize the calculation time.
we constrain to the holes, and have no problems
If the part is molded it probably has a small amount of “draft” to assist in removal from the mold. Draft is a small taper angle so the part is thicker towards the leading end when you remove the part from the mold. Draft can be hard to detect visually on a CAD tube. You have to measure the part to find it, especiaslly if you are using a perspective rather than a parallel view. If you are having draft issues either constrain to holes or use edges rather than surfaces.
ChrisH
I happen to be having the same problem and have tried to constrain to edges and holes but nothing has worked for me. Any other help would be much appreciated.