Molding a long, flat object?
I want to cast a long, thin part in hard urethane (80D) for prototyping. The part will be about 33" long, about 5" wide and about 1/2" thick and is a long radius arc of a circle, as though you have cut a sector from a disc.
It is intended that the upper and lower surfaces of the part will be rolling surfaces. The lower surface is supported atop some transfer ball casters and a second piece can be rolled along the upper surface. Therefore, I want the upper and lower surfaces to pretty flat and straight.
1) Is molding an appropriate method for what I want or should I be looking at a different process?
2) Would a silicone mold, with a support structure to maintain rigidity, be sufficient as a mold? How do you suggest maintaining straightness and flatness?
3) How do I fill the mold?
Do I create a two part mold, tilt it a bit and fill by injecting from the lowest point? Is there a way to fill the open mold and lay the second portion in place without making a giant mess? How would you actually make this part?
I do have vacuum equipment suitable for de-airing. Any tips relating to mold release, etc. would be appreciated
Thanks
It's a 7' diameter circle, so a 42" radius on the arc. Should it matter, the radius is to the inside edge of the 5" width of the piece to be cast.
John - Thanks for the link. Their plastics may be just what's needed for making the mold form.
The problem with machining is that I need to make multiple copies. I guess I didn't make the replication aspect clear. Aluminum deforms too easily. Steel is too heavy. And the machining costs would kill me. So that's mainly why I'm looking at casting