Thread: Epoxy Granite. Has anyone used it on their machine?

Hello all,

I have from time to time read about epoxy granite and using it to fill machine voids to increase mass and rigidity. Most of the discussions have been on other forums, forums that I am not a member of and know little of the members. In these other forums, much has been discussed about the improved dampening properties and so fourth but I have also read other members saying that it is a furphy and nothing is really to be gained. Some of the discussions get quite technical and way above my basic knowledge of material science.

I have done the usual search on this fourm and little has been discussed. Has anyone attempted such a project and if so, what were the results? If so, what ratios and ingredients did you use? I'm really interested to know. I don't have any immdeiate intentions to take this on as a project but I'm still interested in what people here have to say.

Cheers,

Simon

is this something like chock fast?
aaron

Epoxy granite only has the same approx density as Aluminium so you need to add a lot of it to a machine to make any significant gains and given the cost seems like it would be an expensive way to go.

If you really wanted to increase mass you would be better off using something like regular epoxy to attach slabs of lead into machine voids.

Originally Posted by BobL

Epoxy granite only has the same approx density as Aluminium so you need to add a lot of it to a machine to make any significant gains and given the cost seems like it would be an expensive way to go.

If you really wanted to increase mass you would be better off using something like regular epoxy to attach slabs of lead into machine voids.

Hi Bob,

From my limited understanding it is done for the rigidity and reduction in vibration, increase in mass is a secondary advantage, although I could be wrong. I could be totally wrong though, that's why I'm asking!

Simon

Originally Posted by azzrock

is this something like chock fast?
aaron

What's chock fast? Sounds like something you would hear about at the madi gras!

Originally Posted by simonl

Hi Bob,

From my limited understanding it is done for the rigidity and reduction in vibration, increase in mass is a secondary advantage, although I could be wrong. I could be totally wrong though, that's why I'm asking!

In terms of vibe and rigidity, if you increase the mass of any vibrating system you will dampen vibration and increase rigidity so gluing lead into void will still have the same effect. Being soft (ie it does not ring when struck) and heavy, lead has excellent damping features. However it has poor thermal expansion properties (twice that of iron) so it would be worse from this aspect.

The Wikipedia entry for it has some interesting info about epoxy granite. Apart from significant gains in natural vibration damping over cast metal, the big benefits seem to be more in energy savings of production and in very low thermal expansion, but it seems to me that the latter would really only apply if the whole machine base or component is made from the stuff. Just gluing some into cast voids is unlikely to change the thermal expansion properties as the original casting will tend to dominate that aspect of the machine.

Talking about damping reminds me of an electronic amplifier that we had that we were using to detect femtoamp signals. Even though it was set up on an optical vibration isolation table the amplifier could easily detect people walking past in the corridor and a slamming door set it right off the scale. In the end we placed 4 lead bricks on the optical table and that was enough to dampen out the effect of people walking past (but not the slamming doors).

Bob, this stuff is poured in like concrete. I think there was a write up in MEW some time ago by a guy who filled is X1 column with the stuff.

However, to respond to the question asked, as Bob says it will dampen vibration. For large machines I would not bother as I suspect the benefit would not really be noticable. For a 'mini mill' there may be an advantage. If you filled a column with it it will make it slightly more rigid although you then have to contend with flex in the head and table, so it won't mean you can take heavier cuts but the finish on the cuts you do take may be a little better.

Think of it this way - vibration from a source has energy. Increasing the mass will mean less energy per unit mass, so the physical effect of the vibration (movement) should be less. (Should because if you hit a resonance the vibrations are amplified)

Michael

Originally Posted by simonl

What's chock fast? Sounds like something you would hear about at the madi gras!

well Simon you'd know.
but any way its a epoxy grout. that is very strong.
you poor it in and has High tensile strength, compressive strength,
flexural strength, creep resistance and superior vibration damping
so the advertising says any way.
basically a marine grout that goes between a non machined engine bed and the engine.
ITW Chockfast Marine | Epoxy Grouts, Adhesives, Repair Products, Coatings

Chockfast has a density of ~1.8 g/cc whereas granite epoxy has a density of 2.7 g/cc (about the same as aluminium so I doubt they are the same thing.

Originally Posted by azzrock

well Simon you'd know.
but any way its a epoxy grout. that is very strong.
you poor it in and has High tensile strength, compressive strength,
flexural strength, creep resistance and superior vibration damping
so the advertising says any way.
basically a marine grout that goes between a non machined engine bed and the engine.
ITW Chockfast Marine | Epoxy Grouts, Adhesives, Repair Products, Coatings

Hi azzrock. As far as i know epoxy granite is not an actual product. Its more a concept where you buy a commercially available resin and mix a ratio of granite, sand and other stuff.

Cheers

Simon

There is a lot of discussion on this at CNC zone.

Here is an article of a HM45 mill having it poured in the voids. The CNC cookbook blog is a good site for milling and lathe articles.

I am with Bob on this one and a heap of lead will dampen the majority of vibrations.

Originally Posted by Michael G

Bob, this stuff is poured in like concrete.

Yep I guessed this would be the case. I should have a chat with our in-house epoxy ceramicist who researchers this stuff as he might have something useful to say on the matter.

Originally Posted by BobL

Yep I guessed this would be the case. I should have a chat with our in-house epoxy ceramicist who researchers this stuff as he might have something useful to say on the matter.

Hi Bob,

That would be great if you could pick his/her brain!

Rod,

I have read that article. It's a pitty they didn't do a follow up article the their results and opinion after they finished.

Cheers,

Simon

Hi Simon,
I thought the same but I would like to hear the opinions of a few before I did it. I also wonder about the longivity of adhesion when stuck to a disimilar material.

Some woodworking equipment has had slabs of reinforced concrete bolted into the chassis for the same purpose. Others have had it poured in place, but it is a special mix, the details of which are unknown to me.

I like the idea of lead ingots bolted in, or depleted uranium if you can get it locally.