Originally Posted by miljnor Of course its either time or money.  |
Yes, this is usually true. But one measure of a good design is its ability to minimize both.
I've definitely been through the multiple setup milling thing. Yuk.
I've done some thinking about this situation, and come up with the following:
Since the tooling plate is much flatter than the extrusions, use it for the surfaces that need to be flat. But tooling plate in reasonable thicknesses will not be stiff enough for this duty by itself. So the moment of inertia needs to be increased somehow. This is done by attaching extrusion(s) to the tooling plate with epoxy (jb weld?) and moderate pressure (i.e. not enough to deform the tooling plate). Then, after the epoxy dries, bolts are inserted to reinforce the joint. This should keep the slightly bent/warped extrusions from pulling the tooling plate out of line and require no machining. This does mean that anywhere there is a rail mounted, it needs to have a tooling plate/extrusion under it (the rails can not be mounted directly to the extrusion). But you could use two or more extrusions attached to a plate vs one large one (cheaper?). The use of epoxy has the added advantage of increasing joint stiffness.
I'm interested in what anyone else has to say about this idea.
Mitchell