"Jim Wilkins" wrote in message
...
On Jan 14, 11:36 am, "Ed Huntress" wrote:
Twenty-five years ago I got very interested in concrete and polymer-matrix
machine tools, ...
Is anyone interested? And for you guys who are more web-savvy than I am,
suggestions for a way to upload and display photos and drawings?
Ed Huntress

200 years ago lathe ways were made by mortaring iron strips into
granite blocks. The closest I've come was welding a framework from
steel channel and angle and shimming the pillow block bearings into
alignment. As a long-time prototype machine builder I prefer a design
and construction method that is easy to modify. Plastic castings don't
have much tensile strength, especially where material has to be added
and the reinforcing fibers don't cross the joint. Rapid prototyping
resins were the worst, I've needed to cut away a large bonding surface
and sculpt several batches of epoxy to build up a boss that would hold
a new bearing.

Right. The loads and their directions on standard machine tools, though, are
well-defined and they have been dealt with effectively in concrete and
polymer structures. Polymer is easier because it's ductile; reinforcing
fiber begins to take up the tensile loads as they're applied, without
destruction of the polymer.

Concrete is more difficult because it's brittle, as well as having almost no
tensile strength. For that we have prestressing, post-tensioning,
ferrocement, and modified concretes. They're still a challenge but there's a
ton of experience with and information about structures built that way, much
of which applies very nicely to basic machine tool structures. It's also
worked well with some boat structures -- although it has enough problems
that ferrocement boats have waned in popularity over the last few decades.

It's an intriguing idea. If others here who have more up-to-date exposure to
the developments in the field it would be good to hear from them.

--
Ed Huntress