Epoxy grainite build yer own machine frame

Thanks, that's very interesting. My problem with it is that custom machines have a limited life and need to be recyclable into something else. I'm making grinding wheel spindle adapters out of a locating pin from an old Segway fender mold.

I wonder if sand + wax would have useful damping properties.

Jim Wilkins

Jim Wilkins fired this volley in news:c8cc7d07-f9a7- snipped-for-privacy@k29g2000prf.googlegroups.com:

In the old days of audiophiles' trying for the ULTIMATE speaker system, we used double-wall speaker cabinets filled with marble dust, sometimes with just a tiny bit of heavy mineral oil to make it pack more easily.

LLoyd

Phwew. That's quite a list and a lot of posts.

FWIW, I looked into epoxy/granite a long while ago and it's true that a lot of successful, often custom machine tools have been built with it. You may have seen some if you've visited IMTS in recent years.

For my hobby interest, I gave it up -- not because it isn't good, but for two other reasons: First, it's expensive as hell; not just for the epoxy, but also for mold releases, degassing hardware, and so on.

Second, it involves technology that is not freely available. The threads you pointed to may solve that. I'll try to look through them when I have time. Most of the commercial applications involve a lot of proprietary techniques. Epoxy is a great material for laminating but it behaves very differently when you use it for the cement in an aggregate concrete mixture. Settling is a problem, for example, and there are some others. Epoxy's big advantage is that you can get useful (though still very low) levels of tensile strength from the concrete.

Since I posted my thoughts on the Portland cement concrete recently I've started to update myself on ferrocement, and I'll eventually have something to contribute about that. It looks good overall but there are a few things I have to absorb yet. And I have to start from scratch on polymer-modified and random-reinforced cements. They've changed the picture. Another thing that's changed is that a concrete laminating process that formerly was patented has seen the patent run out, and there is some outside development of it and more information is becoming available. I also have some new information on other reinforcements, including fiberglass.

Anyway, that's some great information, Karl.

-- Ed Huntress

There is a very good description of epoxy concrete filled machine frames and their design in "Precision Machine Design", Alexander H. Slocum, Society of Manufacturing Engineers 1992. Slocum is a MIT professor.

Joe Gwinn

Yes, that's a book I'd like to get my hands on. We had a review copy at a magazine I worked for but I never got to spend much time with it. At roughly $100, it will likely have to come from a library for me.

Slocum has some facts and figures in there on polymer concrete (epoxy/granite, and the patented Granitan) that look pretty attractive. He dismisses cast Portland cement concrete for high-precision machine tools, but the little bit I've seen suggests that he's only looking at conventional cements and aggregates and not at composite-reinforced types, like the steel-mesh ferrocement or fiberglass reinforcement. Also, as the title indicates, he's focused on real high precision machining, with advanced controls and sensors, etc., not the conventional levels of precision we typically work with in a home shop.

Maybe some day. First I have to make sure I have all the properties of ferrocement and advanced Portland cements nailed down. I have a copy of _Ferrocement & Laminated Cementitious Composites_, which contains all of the practical engineering data for the composites, but not enough about the advanced cements.

-- Ed Huntress

BIIGGG SNIP

Hey Ed,

I'm not going to get into any of this, but just in passing I see the term "ferro-cement" mentioned. Back a bunch of years ago, they were building boats, in particular, sail-boats, of ferro-cement. I've only seen two that were identified to me, both built in the Great Lakes, used in salt-water for years, and then returned to fresh water. They looked pretty good, and no different that I could see to an FRP construction in many ways. Worth doing a search in the marine world literature as to how they did it?

Brian Lawson, Bothwell, Ontario.

Ah, you raise a big subject, Brian. Yes, most of today's developments in ferrocement were spurred by development of the material for boats, starting in the 1970s. I've been acquiring books on the subject since then and I watched one being built here in NJ, around 1978. There are at least 100 of them, and probably several hundred, in use in the US. You can't tell they're ferrocement by looking at them.

The first ferrocement product was a rowboat built in 1848. It's sitting now in a marine museum in France. Ferrocement preceded what we'd now call "conventional" reinforced concrete, and it got a big shot in the arm in the

Thousands of boats are built in ferrocement around the world, particularly in China and Southeast Asia. The Australians and New Zealanders, and the Brits, have kept it up in the advanced industrial world. It had a short span of popularity in the US but it faded in the '80s, partly because a lot of amateur efforts turned out badly and gave it a bad reputation, and partly because labor costs are high in the building of ferrocement boats, so it offered little or no cost advantage here.

Where labor is cheap, it's popular. And it's advanced a great deal over the past 30 years. I've been interested in making machines out of it for decades now, and there is now enough accessible engineering data that I think it's worth pursuing.

-- Ed Huntress