[lgalla]

Episs
Companys fabricating machine bases of epoxy granite are not in the business of selling the raw material.I did a lot of research on the subject and there is little to be found.Sand is basicly granite and probably a good filler.
Idon't remember exactly the figures,but epoxy granite has 10 times the damping factor of cast iron and 50 times the damping factor of steel.
THE COST??? 1gal. epoxy $80 Maybee 10 sq ft/gal/1/4 thick.Figure it out,its
gunna cost mega bucks even with sand fill at 50%.
This is just off the top of my head.If anyone wants more accurate figures I will look them up again.
Any how I figured out a slab of real granite is 1/2 the price of epoxy granite,maybe less.A 4X8'X4"epoxy granite table top could cost 5or6 grand or more.A black granite surface plate 4X8'X8"with stand is $2600 from an E-Bay store.If anyone is still interested I will try to answer any questions or re-research my findings.
Larry

[walter]

Yes please continue- that's a very good info..

I'm interested in all kinds of solutions.

[snookered1ca]

I just came across an EG machine base on the CNC Cookbook site ( http://www.cnccookbook.com/ Blog 10/12/08) that referenced it to the German CNCZone site. The machine was described as a German Epoxy Granite Milling Machine and is made with R L & G epoxy resin. This looks like the finest example of a DIY EG casting. Is R L & G epoxy available here in North America ? We are looking to try this for the first time and we need to learn as much as possible about this process.

Bruce

[romihs]

Hello Bruce,

Yes, the Germans do some impressive work.

I also experimented a little with the EG mixture closer to the beginning of this thread, and I used the Epoxy the Germans use: L1100 from R&G Epoxies.

Now, I don't know if the R L & G epoxy that you have mentioned is the same as the one I have posted, but I think it is.

I also don't know if this range of epoxies is supplied in North America...

Regards

Sandi

[snookered1ca]

Hi Sandi

Thanks for the response
I haven't found a NA supplier for the same epoxy but there are many others, I'll need to determine what differences there are between them. How did your results turn out. What problems did you encounter ?
We are looking to cast some lathe tailstocks.

Bruce

[ckelloug]

snookered1ca,

Welcome. I can't speak for sandi but I can say that a lot of the epoxies out there that are easy to come by are formulated for toughness and stickiness rather than setting up hard.

My own work with the shopman inc slow hardener and think epoxy (Reichhold 37-127/37-606) is that it doesn't get as hard or stiff as we would like. I've gotten some much better results with Hexion 813 resin and Degussa Isophorone Diamine hardener but this isn't a solution I would recommend for home use due to toxicity and the tricky curing temperature profile required. I'm not sure I've got the curing profile just right but curing the whole thing at 85C makes the hardest most heavily crosslinked material.

Since you're in canada, you might talk to crosslink technologies and ask them what they recommend.

I haven't gotten any work done lately due to having melted my UHMW sample mold in my curing oven. I'm on a crash course right now to build a vacuum and pressure tight mirror finished steel sample mold but I won't be done for a few days.

Crr is expected to report his results with DER 331 and Huntsman amines in the next few weeks. In general, resin isn't the problem so much as finding a hardener that makes the stuff set up like rock as opposed to rubber. Somebody with more expertise in formulation like crosslink might have a good recommendation.

Regards all,

Cameron

[romihs]

Hi Bruce,

My results were a little disappointing. But that is due to the simple, limited, method I used to make the samples.
The samples were small, hence difficult to measure out the correct quantities accurately and I did not manage to compact the samples as well as they could have been.
Also, I did not perform the post cure on the samples.

The samples I had (I've thrown them out since) were "quite solid" though despite not having been compacted.

When I have the space, I will restart my work on this, as I would like to build a CNC lathe with material. I will construct a good vibration table; devise a thorough mixing system and purchase an accurate scale.
Anyway, enough about my dreams...

Attached is a PDF that you may find handy.

Regards

Sandi

[snookered1ca]

Thanks Cameron

I have been in contact with Crosslink and they have a product that they used to produce some epoxy granite Curling stones with a short while ago, which so far looks to be an ideal product that shouldn't be at all rubber like . There is also another resin maker PTM&W that makes a wide range of castings resins and hardeners, they recommended their PT4450 product.

Bruce

[walter]

...Any how I figured out a slab of real granite is 1/2 the price of epoxy granite,maybe less...

Hmm...
How about using some of those kitchen 5"x2" granite slabs?
Should be relatively easy to put few of those "together" and encapsulate it with E/G...?

(This could work for smaller machines, up to 3'x5')

[garfieldsimons]

Episs
Companys fabricating machine bases of epoxy granite are not in the business of selling the raw material.I did a lot of research on the subject and there is little to be found.Sand is basicly granite and probably a good filler.
Idon't remember exactly the figures,but epoxy granite has 10 times the damping factor of cast iron and 50 times the damping factor of steel.
THE COST??? 1gal. epoxy $80 Maybee 10 sq ft/gal/1/4 thick.Figure it out,its
gunna cost mega bucks even with sand fill at 50%.
This is just off the top of my head.If anyone wants more accurate figures I will look them up again.
Any how I figured out a slab of real granite is 1/2 the price of epoxy granite,maybe less.A 4X8'X4"epoxy granite table top could cost 5or6 grand or more.A black granite surface plate 4X8'X8"with stand is $2600 from an E-Bay store.If anyone is still interested I will try to answer any questions or re-research my findings.
Larry

I got a a 2 x 4 block of granit for $100 at an auction. Nobody wants them and they are a pain to move. But they can be had reasonably cheap. Side note my block of granite came with a cmm. And threaded mounting holes.
Richard

[ckelloug]

Hi there veteq Roy,

The mass percentage of epoxy is useful only for measurement purposes. The volume percentage of epoxy is what determines the physical properties of the mixture.

According to the compressible packing model from Francois de Larrard's <u>Concrete Mixture Proportioning: A Scientific Approach</u>, the maximum achievable aggregate percentage is 92% plus or minus 3%. Thus no mixture with more than 11% epoxy by volume could be optimal and no mixture with less than 5% epoxy by volume is possible. The model assumes vibratory compaction. Slightly better compaction is available with huge hydraulic presses but that isn't what we're about here.

This model results from de Larrard are entirely consistent with Mr. Jolincks and the Ph.D. thesis of German Castillio (in French) from the Usinages group, and disagrees with the German group.

There is no question that the German group has done some good machine engineering but I have always felt that their material design was suboptimal. According to their last post in this thread, the Germans are using the Fuller distribution which is demonstrably suboptimal providing at least 6% lower density than the optimal distribution and 5% worse than virtually every other common aggregate distribution. AS for your question about 17% by volume, see the <A href=http://www.cnczone.com/forums/showpost.php?p=444339&postcount=3119>nomograph</A> on pg 260 generated from a formula in A.J. Kinloch's <u>Advances in Resins and Structural Primers</u> and follow the cyan line to 83% aggregate=17% epoxy. You'll find that pine wood with a young's modulus of 2e6psi has a similar stiffness to that proposed E/G mixture. I have tested a few similar materials myself to failure in ASTM D790 flexural tests and gotten modulus numbers that match the nomograph results.

The German group have shown that there is no problem working with a high-tech plastic-wood like formula but if you need stiffness for a large part, there's no substitute for using the optimal aggregate mixture. As long as you can do engineering analysis either on paper or FEM to ensure that you meet deflection and strength criteria you could build a machine out of a suboptimal E/G like the one you propose. The amount of epoxy needed is that amount which fills the voids in the aggregate and perhaps a tiny bit more to aid in processing. The perfect epoxy is a lot less important than an aggregate distribution that achieves a density of at least 92% when compacted.

The vibration numbers I have seen cited in both Castillo and de Larrard suggest that the entire mold must be vibrated at between 2g and 4g at 50 or 60 hz. This is a somewhat difficult proposition for the average contributor here. In general, the longer the mixture is vibrated, the more it compacts. What you can get away with depends on the pot life of the mixture. Most of the epoxy formulations I have considered reasonable have pot lives in the 4-8 hour region and it's almost certain that vibrating this long cannot be good. I have only made small samples with minimal vibration so far so I can't shed any light on the right way to do it. My only certainty is that to make a single production quality E/G machine requires more capital that getting a whole bunch of cast iron and scraping it.

If you are using a suboptimal aggregate mixture, it will segregate and as a result, there is a balance between vibration time and compaction. The de Larrard Minimum-S mixture is ideal as it can be vibrated with limited segregation but I don't have my compressible packing model code implementing it correctly right now so I can't solve the general case for arbitrary aggregate.

There are huge 220V 3 phase vibration motors available but they are expensive. I have a 3 horsepower unit over at my lab that I found surplus for maybe 1/5 the cost of a new one. I think it's 15 Hz by default but with a nice VFD, I should be able to get it up to 30Hz or a bit more. A standard concrete vibrator is too small by all accounts I have read. The 3HP unit I have weighs 400 lbs and the rotors are so heavy I can barely spin them with my foot. The problem is that you need a sturdy table to which you can attach the vibrator and isolators so that you move only the table, vibrator and contents without trying to move the building the vibrator is in. A large steel plate for the table and the vibrator itself will add substantial weight to the weight of the part in your calculation. The deflection will also be based on the weight of the table and the stiffness of the springs on which the table rests. Stiffer springs will provide less deflection and less isolation from the building.



Material Design Conclusion:

If you would be confident in holding the desired deflections on your machine if it were made of softwood like pine, your proposed material design is sufficient. This is a very good approximation as the moduli are almost exactly equal between pine and epoxy-rich E/G. Approximately 2.5 times better stiffness would be available with an optimal material.

On Vibrators and Vibration:

With regards to your second post about building a vibration system, it is my opinion that your 3rd design has the potential to fail catastrophically. The reason that commercial vibrators are expensive is that they have huge bearings and are very heavily built. The forces at the bearings of an off balance rotating item are astronomical. I have reservations about the third drawing because you have the rotating mass rather far from the bearing. This will tend to cause cantilever deflection in the shaft and I would worry about catastrophic failure of either the shaft itself or the bearings. The bearings of a precision motor are not built to handle the abuse of running as a vibrator for long but the setup is probably sufficient for a one-off. If you are okay with the potential of catastrophic failure and loss of the motor, make sure to build a sturdy containment housing to catch the airborne parts.

With regards to the calculations, I see nothing wrong with what you have done but I think your weight estimate of the entire setup might be too low. Pay special attention to the section on isolation in the Deca vibrator page you cited. This static system deflection that they cite is the amount that the vibrator, table etc deflect the springs that it rests on due to their weight. The numbers that they give here are a surrogate for solving the second order differential equation of motion for the vibration table. See <A href=http://www.thevmcgroup.com/springmounts.html> The VMC Group</A> web page and get a copy of the Korfund Dynamics Catalog under downloadable PDF's to get a better feel for what you might need.

Also note that commercial vibrators have adjustable rotors that allow the amount of off-balance to be adjusted by controlling the angular separation of two parts of the rotor. The page you are designing from seems to assume you will use this adjustment to correct the operation of the system into the nominal parameters.

With the type of motor you are proposing, I think I personally would want to belt drive the off balance rotor and house it separately in a housing with very substantial bearings. This would at least preserve the motor should something fail.

At any rate, I wish you the best of luck in your endeavor and think I can speak for everyone when I say we look forward to hearing about your progress.

Regards,
Cameron

[whitis]

.Sand is basicly granite and probably a good filler.
...

Guess again. Sand can be derived from many rocks, including granite, but if you buy a bag of "sand", you probably get primarily quartz sand (silicon dioxide); at least in the continental US. I have personally experienced black lava (basalt) sand, green olivine sand, and white coral sand in their native environments (Big Island, Hawaii); these aren't what people mean when they talk about sand and thus have prefixes as qualifiers. Real epoxy quartz is another contender but not the same as epoxy granite and has different properties. Sand, of any sort, is not that good a filler by itself, you want a variety of sizes of material and shape matters, too. If you use sand, you are likely to end up with a result that more resembles the properties of epoxy than that of rock. Oh, and 50% aggregate fill is ridiculously low and would have lousy properties, though if all you used was sand you would have a hard time getting a reasonable fill ratio. Epoxy sand would be useless structurally but would provide some damping as a filler material but would cost more than epoxy granite due to the poor fill ratio and high epoxy content. Done right, the aggregate is not a "filler" - it is the primary constituent and epoxy is the filler - it fills in the gaps between particles, holds them together, and contributes viscoelastic damping.

Granite is not the same as epoxy granite. The mixture of a rock material and a viscoelastic polymer material has some damping advantages. Granite doesn't mold, it is hard to machine to shape and cut holes in, etc. and surface plates typically hold their flatness specs with smaller loads than would be encountered in a machine tool and aren't designed to handle the weight. Surface plates come in more or less flat slabs that have lousy strength to weight ratios. You want a honecomb/waffle/ribbed design or you end up with a machine that is too flimsy or too difficult to move, or both.

You haven't suggested anything that hasn't already been discussed.
There are over 50 pages in this thread alone and there were prior threads. Overwhelming, yes. But it is even more overwhelming for the next guy who has to read 50+ pages plus yet another rehashing of worn out ideas and errors that have already been dispensed with. Read and learn.

[garfieldsimons]

Episs
Companys fabricating machine bases of epoxy granite are not in the business of selling the raw material.I did a lot of research on the subject and there is little to be found.Sand is basicly granite and probably a good filler.
Idon't remember exactly the figures,but epoxy granite has 10 times the damping factor of cast iron and 50 times the damping factor of steel.
THE COST??? 1gal. epoxy $80 Maybee 10 sq ft/gal/1/4 thick.Figure it out,its
gunna cost mega bucks even with sand fill at 50%.
This is just off the top of my head.If anyone wants more accurate figures I will look them up again.
Any how I figured out a slab of real granite is 1/2 the price of epoxy granite,maybe less.A 4X8'X4"epoxy granite table top could cost 5or6 grand or more.A black granite surface plate 4X8'X8"with stand is $2600 from an E-Bay store.If anyone is still interested I will try to answer any questions or re-research my findings.
Larry

If you follow the auctions you will find used surface plates quite cheap. (I got a 3 x 5 for $50. Moving it was real fun though) Epoxy based is crazy expensive. Better to play with concrete.