Constraints in assemblies
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I have several problems with adding constraints to assemblies. The set of constraints possible is assymetric with the sketch constraints. For example, I would like to say "this surface must be parallel to the YZ plane" or "this surface must be parallel to that surface". Using "mate" is insufficient, because in the first case, I don't have the plane to mate to, and in the second case, the object is constrained to part A of the drawing, but one of its surfaces must be parallel to a surface in part B of the drawing. I do not know how far apart they will be when the constraints are met, in fact, the whole point of this is to determine what that distance is.
A more concrete example: the surface of part A is the top of a swivel caster. The surface of part B is constrained by its mounting to be a certain distance from the floor. So I want to "mate" the surface of the wheel to the floor, then force the top of the caster plate to be parallel with the surface of part B. I have some nice 3" casters I want to use, and am not even sure where to buy casters except online, and don't want to cycle through 4", 5" or 6" casters. Better still, I will just create a "shim block" of the size measured from the assembly, then put that in, mate it solidly to the platform that needs the wheels, and then mate the top of the caster to it.
I would post the drawings, but it is 4:15 am, I have to get up at 10am for a dental appointment, and putting the whole mess together will cut into my already-too-small sleep budget.
Another thing I would like to say: the centerline of part A mates with the centerline of part B, so part A is centered on part B. I hit this problem many times in my assemblies.
Another annoyance is that every once in a while, for reasons I cannot fathom, the part I join is rotated 90 degrees from where it pointed before the join was done. It should not change at all. There is no primitive in the assembly that allows me to say "please rotate this part N degrees along the {X,Y,Z} axis", where N is almost always a multiple of 90. I can do it when I place the part, but once the part is placed, a simple idea such as rotating in one axis by a specific amount is lost (or so it seems). "Free rotate" is not the answer; I only want a specific quantum of rotation along a single axis.
This project is the first one where I have created assemblies that become parts of larger assemblies, so I'm wandering around in the traditional minefield-without-a-map mode, where the docs just don't answer the question I need answered. Thank you all for your patience with a newbie.
joe
