[tootalew]

My face might be new to the thread, but I have been reading from the start. For us hobbyist, I think the idea of EG is just to good to be true. I have two projects in the making, a gang lathe being build up on a surface plate, and a bridge router using composite quartz counter top as the base. I may also want to attach the composite quartz to the bridge, to attach the linear rails. I have not yet tried to drill the quartz material, but found that drilling the granite surface plate to be rather easy. Many counter top fabricators destroy fall offs with a grinder, others just stock pile it, or have annual sales to guys like us.

I know I am thinking outside the box of this thread, by using prefabbed quartz, and using epoxy to sink threaded inserts, but my way of thinking is this....someone else already got the process down why reinvent the wheel. I know many of you want to cast parts with this material and I salute you and hope one day you find (and share) a recipe that is easy and cheap for us in the hobby to use.

[ckelloug]

Yep, tootalew,

It turned out a touch more difficult to get E/G right than we expected. A lot of development went into the commercial materials and we're seeing the effort level here. It think we pretty much understand the parameters at this point, it's just about tuning the models, gathering the data and getting enough vibration to make test pieces now.

It sounds like you have taken a fairly levelheaded approach in using prefabricated granite and quartz parts.

I finally got the critical bugs out of my packing simulator last weekend and have started playing with a really bad graphical interface to it. I'm working on optimizing the mixture of the 6 components from agsco that we keep discussing. I hope to have some more useful simulator results in the next couple weeks.

Brenck,

Walter did not finish. He said he wasn't happy with the results he got despite how good they looked. He privately sent some rather strange goodbye messages to a few of us and then disappeared.

I'll run his last mixture on the newly debugged simulator and try to get an approximate epoxy percentage.

In general, one can make an E/G that has similar physical properties to wood without any difficulty: 2e6 psi flexural modulus, 2e3 psi flexural strength. Duplicating the stiffness and strength of a commercial mixture is more difficult than just casting any old part out of any old stuff from the shop floor.

For wood router guys, a simple mixture like Walter's will probably be fine. My own interest and that of several others is to make high end metalworking equipment and other precision machinery. Precision machinery tends to need stiffer materials with lower expansion coefficients.

I won't belabor the rest of the points; I'm still working on this problem, I just haven't been able to work on it at the level I was when I started here.

Regards all,

Cameron

[Brenck]

Cameron,

As soon as you run the simulator please post the results here.

You mean that is not possible to make homemade EG for a metalworking machine?

Is gravel, that black gravel used in concrete actually black granite? Or its basalt?

Other thing have you guys check this out

http://www.enviro-abrasion.com/castbasalt.htm

I wonder if they make machine bases out of this it says basalt after heat threating makes it up to 8-9 mohs hard... Pretty amazing

[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.

[lgalla]

WHITIS,sorry you had to read all those posts.I feel singled out as you used me as a quote.If you have really read all the posts you would see that I only see hobyist E/G as a damping material to enhanse existing structures vibration damping.Filling hollow steel tubes or use as a machine base is good applacitions.As you say a total machine of E/G is just not strong enough.BTW one of the major E/G manfactures was sued by a customer who purchased 20 or more machines that cracked.The customer won.
Larry

[ckelloug]

Hi Brenck,

The mixture walter said he was using was 1/6 each by solids volume of the following. Walter disappeared before he ever confirmed exactly what he was doing. I'm predicting here the optimum amount of epoxy but I don't actually know what he used.

Agsco #6 Al2O3
Agsco #4 quartz
Agsco #2 quartz
Agsco #2/0 quartz
3M G800 Zeeospheres
3M G200 Zeeospheres

Given my modeling assumptions, I calculate that the packing density possible with this mixture is 87.6% plus or minus 3 percent. Using the result from Kinloch's book, I predict the flexural modulus at about 3.5e6 psi.

In comparison, the modulus of pine (and the samples I've tested so far from members here) is 2.0e6 psi.

<B>New Result</B>

I have just completed some preliminary optimization studies with my newly debugged simulator and optimizer. The best mixture I can find using the Agsco Raw Materials in question is below. Note the Absence of #2 Quartz.

17% Agsco #6 Al2O3
38% Agsco #4 quartz
26% Agsco #2/0 quartz
07% 3M G800 Zeeospheres
12% 3M G200 Zeeospheres

Given the modeling assumptions that I made, I predice the packing density possible with this mixture as 90.7% plus or minus 3%. I predict the flexural modulus at 5e6 psi.

Assuming the accuracy of data used in the packing model and the data used by the modulus model in Kinloch, the optimized mixture is 42% stiffer than Walter's mixture. As has been said many times, the last few percent aggregate fill make all the difference in the ultimate stiffness.

I will not be able to verify this result in the lab for some time but if anybody is bent on experimenting, I'd recommend this mixture over any of the others I've suggested on the thread. It's quite interesting that the #2 quartz gives us too much of that size material when combined with the #2/0 quartz.

<B>Comments</B>

I don't know about anyone else here but I have found almost all of the comments here helpful over the last couple years. While I don't happen to agree with lgalla that all home made E/G can only be used as a fill in something else, I have learned a lot from his posts about the shop behavior of epoxy, especially when I showed up on this thread. He's right that badly made E/G won't be good for much. On the other hand I think we're pretty close to being able to meet or exceed commercial specifications material wise.

What I think will kill E/G for home users is the fact that the vibration level required to properly compact a part big enough for even a Sherline lathe will exceed what most people are willing to pay for.

Hi whitis,

It sounds like you have a fair amount of experience with sand and material properties. Are you another one of the folks with commercial experience? I am well aware that 50% aggregate fill is too low as I hope most posters are. Commercial quality will require at least 88%. Ideally, 92% is desirable although this will likely require aggregate sieved especially for the purpose.

Regards All,
Cameron

[dflora]

Re poor surface finish. I read an article about a technique to get faithful (bronze I think) reproductions of sculptures by making a plaster of paris molds, whereby the original is first painted/splashed with a more dilute plaster to create a thin layer which captures the detail. Then the more structural, thicker plaster is layered on. Maybe this idea can be adapted to what you are doing. This is an artisan technique from a couple of hundred years ago. .. still used.

[brunog]

Dflora,
I believe this technique was used by Thomasz, on the German thread, when casting his machine parts. This technique also has an advantage when steel inserts are used specially they are set close to an edge.

Best regards,

Bruno

[Brenck]

I dunno if someone asked this, too many pages that I can't remember not even 20&#37; of all.

What would happen if we get a mix that its lets say only 5% epoxy? Consider some serious vibration to test this... Is it possible to get a mix that dry?

[Eric R.]

Although theory is great, it has no value without applying it in the real world.... therefore I have decided to build my own vibration table and start experimenting, hopefully proving that home made E/G can provide great machine bases.

One of the things that I have learned about vibration tables for mineral casting, is that the frequency should preferably be >4500 rpm to get good results, while most vibration motors for concrete applications are limited to 1500 or 3000 rpm. If the frequency is too low, you can add as much power/force as you like but that may not always contribute to compacting the aggregate; instead the effect may be be like shaking up a pillow.

As a starting point, I have just bought two vibration motors (each 1000W, 10kN, 6000 rpm, 250V/200Hz) with which I will build my own vibration table within the next month or so. The air springs will arrive today and the motors will be delivered next week. Together with a rugged frame, table top and frequency inverters for the motors, this should get me started. If the vibratory compacting effect is not sufficient, I will add another pair of motors. (Just for those who are not too familiar with vibration tables: the motors always have to come in pairs, with opposite rotating directions to create vertical motion only, which gives the compacting effect.)

Any suggestions are more than welcome!

Eric

[ncmeinc]

If you take a look Hardinge machines there bases are made of epoxy concrete and they have always had great finishes on the parts made on them. You can buy there concrete to make a machine with or use philadelphia resins. I talked with them about doing a big wood router and they said it would work way better than a metal machine.

Harko

Cameron,

As soon as you run the simulator please post the results here.

You mean that is not possible to make homemade EG for a metalworking machine?

Is gravel, that black gravel used in concrete actually black granite? Or its basalt?

Other thing have you guys check this out

http://www.enviro-abrasion.com/castbasalt.htm

I wonder if they make machine bases out of this it says basalt after heat threating makes it up to 8-9 mohs hard... Pretty amazing

[Brenck]

Eric R,

Does it have to be air springs?

I'm considering on building one for me since the one I got acess to in college its too weak, and got only one motor,doesnt use air springs either...

Can you post pictures when building yours?

[Eric R.]

Hi Brenck,

You can use whatever vibration absorbers you want, as long as they provide sufficient isolation to ensure only the work piece will vibrate and not the entire building . Air springs are known to be perfect for that job. The table I am building will measure 2 x 1 m (= approx. 6.6 x 3.3 ft) and I will be using 6 air springs (type: ContiTech FS 70-7), placing them 1m (3.3 ft) apart from each other. This will be sufficient to carry up till 3500 kg / 7700 lbs while providing >99&#37; isolation. The springs that I have selected cost approx. USD 95.- a piece, but depending on the load, you may select smaller springs and safe some bucks.
The air springs that I selected are made by ContiTech (European, as I am based in the Netherlands) and they have an online catalog which provides a nice tool (5th tab) to help you calculate and select appropriate air springs: http://213.164.133.30/catalog/Start.do?language=2
If you are based in the US, you may want to have a look at the Airmount Isolators from Firestone: http://www.firestoneindustrial.com/n...solators.shtml

Again, there are other ways to provide vibration isolation, but I feel air springs are the best. But be aware: air spring need to be pressurized after they have been mounted and preferably the pressure needs to be adjusted after the load has been placed on the table. This implies that you need a compressor, like you would check and correct the pressure of your car tires. As most air springs come without valves, you may need to purchase these separately. My table setup will have fixed pressure lines, which will connect to a central block with one pressure inlet for the compressor and six valves / pressure outlets for the air springs, so I can adjust the pressure for each air spring independent from the others.

Just for those who don't know air springs, here is a picture:



I will post pictures when I start building my table.

Regards,

Eric

[Brenck]

Why all the vibration motors are double shafted?

Is one side weight oposite to the other? like 180º?

Man I'm looking here this firestone air springs are so expansive... I might use something diferent...

I might need to find an alternative to that, I wonder if using wheels on the table with wagon cart tires would be the same, I would have to make it an outerframe or else the table would start moving when vibrated, I'm sure it would be fun to watch

[Eric R.]

Why all the vibration motors are double shafted?

Just imagine yourself walking around carrying 100 lbs of sand. Would you prefer to carry that sand in one bucket in one hand or would you prefer to balance the load over two buckets, one in each hand. I think you would find the second option more balanced and much healthier for your back. Double shafted motors take a similar approach, increasing stability and durability.

Is one side weight oposite to the other? like 180º?

Nope. They need to be on the same side in order to create most impact with each 'swing'.

Man I'm looking here this firestone air springs are so expansive... I might use something diferent...

I might need to find an alternative to that, I wonder if using wheels on the table with wagon cart tires would be the same, I would have to make it an outerframe or else the table would start moving when vibrated, I'm sure it would be fun to watch

I guess you mean expensive instead of expansive (although you are technically correct: they are expansive as well; add more pressure and they will expand )
It sure would be fun to watch the table being on the run!

[Low-Alloy]

I am wondering which would produce superior compaction--A horizontal or vertical vibratory direction?

My thinking is if the aggregate is constrained on all sides, but with downward pressure placed on the top, a horizontal shake would push the smaller particles to filter down past the larger sizes as the mold's size is force ably reduced.

Valid or miss the mark?

(Just for those who are not too familiar with vibration tables: the motors always have to come in pairs, with opposite rotating directions to create vertical motion only, which gives the compacting effect.)

Any suggestions are more than welcome!

Eric

[Brenck]

I dunno but for logical thinking on polymer resings models I think that if you vibrocompact more then you suppose to do you might make the epoxy float in the mixture.... But I dunno if the mixtures where epoxy rich or just to much vibrocompacted. Gotta find out, my friend is working on a P/C factory that makes '' clothes washing tanks'' ( I dunno if u can translate that from portuguese to english ) And its pretty amazing that the mix that they get from a 20&#37; p polyester resin mixture cab hold 400 lbs... I will get a sample of those soon and will post pictures here.

[Eric R.]

I am wondering which would produce superior compaction--A horizontal or vertical vibratory direction?

My thinking is if the aggregate is constrained on all sides, but with downward pressure placed on the top, a horizontal shake would push the smaller particles to filter down past the larger sizes as the mold's size is force ably reduced.

Valid or miss the mark?

As a rule of thumb, for compaction purposes vertical vibration has proven to be the best. Besides that, in order to create vibration in a horizontal plane, the pairs of motors would have to be mounted in a vertical plane, which is not very practical.
Here is a link which shows some vibration tables for mineral casting, produced by a German manufacturer. These also vibrate in a vertical direction: http://www.knauer.de/index.php?id=vi...k_making49&L=2

[romihs]

Eric,

It's been a while since I've posted here..

I am quite interested in your work. I am curious to see how much this table will cost you and also what the results will be like.

I have had it on my mind to build something similar to what you are doing, just don't have the space for it....

I feel that all that is needed for this material to be useful is good vibration.

Could you share the info of the motors (vibrators) you have ordered?

Thanks

Sandi

[Eric R.]

Hi Sandi,

The motors are BRECON, part number 18-220-130. You can find them on page II-3 of this document: http://www.brecon-vibration.com/file...l_Vibrator.pdf

The costs for this table:

• 2 Vibration motors: I was very lucky to buy these from an obsolete inventory and paid only EUR 200 a piece >>> EUR 400
• 6 Air Springs: 6x EUR 75 >>> EUR 450
• Steel construction: EUR 300 (I will do all the welding myself)
• Pneumatics (for the air springs): EUR 150 (not including compressor)
• >>> Total: approx. EUR 1300

Regards,

Eric