[harryn]

sigma John,

Sorry not to key on the DOE (not Dept. of Energy) trial thing. I've been busy trying to solve a riduculously annoying but simple software problem in the paying portion of my life for the last week or so.

In general, I would consider the aggregate problem to be solved. Given any mixture of aggregate, I can say within less than 3% what the packing density Phi will be after taking a Beta measurement on each component. (I'm using estimated beta values right now and thus my results are only relative to one another right now). The French Researcher, de Larrard, whose models I have implemented spent about 10 years validating them with data and has published many papers and the book I am working from. I have shown that I can duplicate the numbers published in his book.

Given that the aggregate packing density Phi can be calculated to within 3% for the model, My engineering judgment tells me the DOE experiment design doesn't need to account for individual aggregate types but should instead specify Phi values. Phi goes from 0 percent (all epoxy) by volume to about 92% (8% epoxy) by volume.

It is known from the rule of mixtures model that modulus follows a uniformly increasing nonlinear curve with percentage of aggregate. It is also known that eventually there is a point where the modulus becomes zero with increasing aggregate content due to insufficient epoxy to bind the material.
The minimum amount required to fill all of the empty space in the solid is 1-Phi. Any less than that and the mixture doesn't contain enough epoxy to hold itself together. More epoxy than 1-Phi that causes the particles to be fully encapsulated by epoxy in model terms.

So, I would say the first unknown is what the optimal amount of epoxy for maximum modulus is. Of course this assumes that all mixtures with the same Phi value are equally good for modulus. This assumption is true according to the rule of mixtures but there could be effects related to the quality and type of aggregate that cause fractures which affect the result.


Here is the summary of factors,likely effects on modulus, and range is as below:

Packing Density of Particles: positive linear: 0----92% by volume aggregate
Epoxy volume percentage in composite: negative linear: (100% - Phi)----50% by volume aggregate
Titanate Concentration: concave down parabolic: 0----1% by weight aggregate
Silane Concentration: concave down parabolic: 0----5% by weight aggregate
Cobalt Acetyl Acetonate Concentration: positive linear: 0----1% by weight epoxy
Epoxy to Hardener Mix Ratio: concave Down Parabolic: 2.1-----2.5 w/w for 37-127/37-606
Well Dispersed Nanomaterial Concentration: positive linear: 0----10% by weight epoxy

Once the gross problems like bad choice of hardener etc have been worked out, a DOE trial of the above factors would be a good way of getting the optimal material.

Regards all,

Cameron

Hi Cameron - I think your variable set, range, and potential result is getting closer. I will suggest a slightly different way to view it which might be entirely wrong, but here it is anyway.

a) The first testing set
- Modeling is great, but obviously, we are getting to the point where the theoretical models need some baseline testing - if for no other reason, than to see if they are not just figments of our imagination.
- At this stage, we have so little experimental information on the "real" effects, that we should concentrate on getting a baseline on likely first order effects in the general mix range that is plausible.
- It should also be assumed that the first DOE experiment will be botched. That is not a criticism, it is just simple reality - science is messy, especially wet lab science. Keep it simple.

b) Phi - essentially void space as a variable in the DOE.
- My perception is that this is not a good item to select as a variable, even though it is a calculable variable and subject to some reasonable experimental control.
- Even if you have an extremely well controlled bulk value for Phi, locally, this will have wide variation no matter how well we are able to mechanically mix.
- The smaller the agr. size, the more difficult it will be to mix, making Phi even less reliable as an indicator.
- Once the minimum size agr takes on an (unknown) layer thickness of epoxy, the Phi value becomes almost lost in the noise.

b) Minimum agr size as a variable
- My suggestion is to use the presence or absence ( 0 - 100 %) of your smallest agr. as a variable and see if the needle moves enough to keep it in as a first order effect compared to other factors.

c) Epoxy concentration
- This one is more obvious 10 - 20 % range
- If the real need becomes 25 %, then the first DOE will tell us to go that direction anyway.

d) Hardener
- Type - I would guess there is an effect, but this is not a variable that can easily take on a 3 "level" effect for the DOE, especially the first round.
- Qty of hardener - this is more easily fit into a DOE.

e) Cure Temperature
- Likely first order effect

f) Cure Time
- Likely first order effect

Keep everything else steady.

That is more than enough variables for a a first trial. JMHO.

[corrie]

Very interesting thread,crazy as this may sound but what about various size marbles as a filler. They are smooth, solid and made of glass.Also what may work is those various size stones that some people put in dishes with candles in them for decoration,they are also smooth and solid. Just my two cents,cheers.

[BrendaEM]

Marbles are smooth; you want something rough that that you can get a physical bond onto.

[ckelloug]

Hi,

I got a note from hexion apps engineering today that hexion europe is not even considering making hexion mineral casting epoxy available in the united states. They are going to send me samples of their epoxy system that is used by others in a machine grout application however.

So for the european contingent here, the hexion system we've posted about before is a good target: http://www.cnczone.com/forums/attach...9&d=1204501651

For us Americans, the challenge is now to design something better.

corrie,

The marbles aren't a bad idea. They are glass which is fairly strong. I'm not planning on making parts that need fillers that large but they are spherical and would be great for a huge casting.

BrendaEM,

There is a debate that rages about these whether you want spherical or crushed aggregates. The hexion data sheet cited above shows that spherical is easier to process but that crushed is a bit stronger. Spherical particles also pack better.

Harryn,

Thanks for the critique. We could work on this without posting here but I wouldn't get the benefits of everyone else's opinions.

I'm not so sure that Phi is bad to work with simply because it is a statistical property of the overall aggregate distribution. It can even be measured on the actual aggregate in use although I haven't made the measuring instrument yet. (Just a tube with a weight, a vibrator, and an easy way to put a caliper in to measure the height of the weight). With a measured Phi value as opposed to a calculated value, I do believe 1-Phi is definitely the lower bound on epoxy because any less won't even fill the spaces between the aggregate.

No criticism to be taken about the "first DOE test will be a botch". I've already botched two batches of epoxy trying to get a single set of D790 samples for the raw 37-127 epoxy.

lgalla,

The Reichhold guys actually suggested adding 37-057 diglycidyl ether to the resin side rather than nonyl phenol to the hardener side. The hardener already has so much nonyl phenol that they may be using it in the mode of a cure retarder. It's probably one of the reasons the stuff isn't setting up as hard as we would like.

Finally,

I've been research non-traditional curing agents and accelerators seeing if we can get anything that works well and is low viscosity and less toxic than some of the stuff normally used.

Regards all,
Cameron

[roach]

they use silane to make silicon rods
make mc beds that grind cubes of it to be cut into wafers
the fumes from the amounts your gonna use wont do you any harm
open a window will do it
they use the same data sheets fot a millilitre of it or aswimming pool of it
id be more worried about skin contact it burns like hell and dont heal well
we always say treat it like sxxt which you would'nt leave on yourself either
"cough"cycloaliphatic polyamine :}

[BrendaEM]

Regardless of the general shape of the aggregate, whether sphere, oval, flat, rods, it would probably best that the surface of said aggregate have a texture that would help create a physical bond, as epoxy is not going to adhere well to a slick surface.

If a aggregate such as marbles were chosen, it would work better if they were rock-tumbled with some grit, not only to create a surface capable of interlocking with the expoxy, but also to create more surface area to be adhered too.

Using marbles does have one advantage, glass has relatively low expansion. Pyrex spheres would be better yet.

[ckelloug]

Roach,
Point taken. I still will try several things but IPDA is definitely on the short list.

I just got confirmation of enough samples from Hexion of resins, hardeners and catalysts to get some research done. I'll bug degussa tomorrow about IPDA.

Brenda,
Point well taken too. Totally smooth things don't get the lock and key affect where epoxy hardens in the rough surface and "locks" things together.

Regards all,
Cameron

[harryn]

Hi BrendaEM. I need to pull out the information on siloxane based adhesion promoters again, but the chemical bonding involved is quite strong. I probably have missed some pictures, but so far, I have not seen any evidence that agr is de-bonding from the epoxy, while breaking through the agr is observed.

Similar to the forces which actually exist in a pile of oranges at a grocery store, it is sometimes interesting to find that agr in the mix can actually be under considerable tension even when its location in a beam would first indicate it should be under compression.

If we suspect at all that our agr could be failing from tension vs compressive loading, then normally the greatest strength will come from a very smooth surface.

A "few" pages back , I think I linked to some articles I found on line about tenile failures of agr in road projects - it initiall surprised me - and I am guessing some civil engineers as well.

[ckelloug]

I was looking for something else today and I stumbled across this hardener: reichhold 37-601. This is an isophorone diamine adduct hardener which has low viscosity. The only drawback is that the rated pot life is a bit under an hour.

It is only an NFPA 2 health risk where as pure IPDA is a 4. i.e. it's pretty much what we want and less toxic than pure isophorone diamine. It also shows better flexural strength than 37-606 according to the data sheet.

Comments?

Regards all,
Cameron

[roach]

du u want be to blend some hardener and post t or yiu wny ti work out ygury selfs

[brunog]

Roach,
Slow down, you type too fast!!

o fofmy imfrtdysmf s eptf ! (go 1 char left)

Setb gerard

Unorb

[ticica]

du u want be to blend some hardener and post t or yiu wny ti work out ygury selfs

I believe there are two types of people following this thread closely. The first one is the experimenters, the ones who contribute 80+% of all posts. They will keep trying to improve the mix even if you give them your best recipe.
The second type are builders, who just want to get something decent going as soon as possible. We would love to get something reasonably good, and get going with our own casts.
So, roach, you won't spoil anyone's fun and will help a whole bunch of folk if you reveal some more of your well appreciated EG wisdom.

[ckelloug]

I believe there are two types of people following this thread closely. The first one is the experimenters, the ones who contribute 80+% of all posts. They will keep trying to improve the mix even if you give them your best recipe.
The second type are builders, who just want to get something decent going as soon as possible. We would love to get something reasonably good, and get going with our own casts.
So, roach, you won't spoil anyone's fun and will help a whole bunch of folk if you reveal some more of your well appreciated EG wisdom.

I'd have to agree with ticica, that it can't hurt if you tell us a bit more or suggest a hardener formula. My only concern would be if you tell us things that you shouldn't due to being a trade secret or something.

That being said, the reason for all the experimentation and theory here is that we started out with no quantitative information whatsoever. The formulas used by the major companies are proprietary trade secrets and thus weren't and aren't available to us. Thus we had to work from first principles. Some of the folks interested including myself would like to build high precision metalworking equipment and as a result, need characterized material which is stiff enough to keep deflections in the .0001 inch range. For those who want to build a wood router where beam deflections of .01 inches are acceptable, the current formula with the 37-127 and 37-606 and the 1/6 of each aggregate recipe is just fine.

After a year of work on aggregate, we have what appears to be a simulation capable of producing the optimal aggregate distribution from any set of starting materials. This work has generated enough interest that others with practical knowledge have contributed.

The only concern I have about getting a formula with "too much practical knowledge" is that it brings a lawsuit from somewhere like Studer if we try to commercialize a formula that looks too much like their trade secret.

Hexion europe sells heavily engineered mineral casting epoxy but they seem to think it is a competitive advantage that they plan on keeping in europe. The european contingent here could save a lot of trouble by just buying some of this hexion system and moving on.

Us Americans on the other hand will have to create our own formula as there isn't an off the shelf formula available here.

Due to the audience here on CNCZONE , I would prefer to come up with a formula that uses adducts and other techniques to keep the toxicity down. Diethylene Triamine and Isophorone Diamine are toxic and corrosive as well as a bit difficult to get for the average reader. I know roach has said that IPDA is not the end of the world but to commercially supply pure IPDA with that toxicity for home use in large quantities seems like a recipe for disaster even if it is fine for industrial use with good industrial hygiene procedures.

My own goal is to make certain machines and items with the E/G technology we have all worked on. The basic E/G formula we come up with here is in the public domain and free to all. If I am able to commercialize any of the machines I wish to make however, I'd be happy to sell the material I would use for my own devices to those who are interested and in my desire to share lies my desire to use things that are both relatively safe and effective.

In conclusion, while many of us find the pursuit of the formula entertaining, the reason for the continuing experimentation and research is that we don't have a formula yet that is sufficient for making precision metalworking machinery. Our current best formula is a bit more than a factor of 2 less stiff than commercially available materials. We are close however and will get there. We will get there faster with help as long as the help doesn't lead us to a formula that we can't use because it is somebody else's trade secret.

Regards all,
Cameron

[dfro]

Hi everyone,

I have been away from this thread for a long time, while I scamper around trying to make rent. The batch of EG materials I ordered months ago has been sitting in a corner. But, it is time for me to start making some casting experiments, get some skill, and move on to building a machine. I am exited at how things are progressing on this thread.

I would like to try the homebrewed Epoxy Babbit (EB) formula that has developed. It would be great if all of the bearings in the machine could be homebrewed. That would take the goal of a cheap precision cnc machine to a new level.

Larry,

You and others want to build massive machines with huge tables. My thinking is that the best way to go is to cast the table onto the concrete floor, like you and others have mentioned before and like precisionepoxy.com is doing with the epoxy surface plates. Embed all of the metal attachment plugs or rails into the plate casting. If you ever have to change locations of the machine, just cast another plate. The surface plate that you leave behind is a selling feature or you have added value to the landlord's property.

There is the problem of bending over all the time to handle parts on the machine. So, what about building a rammed earth base for the table/plate? It would be dirt cheap to do - pun intended. Builders are making walls that hold up several floors out of rammed earth. My initial reading on rammed earth seems to indicate that it could have some good damping characteristics, too.

Here is my initial thinking on how I would do a rammed earth table. First, I would lay down a sheet of plastic, so that the structure is not bonded to the concrete floor. I would build a mold the size of the table I wanted and place it over the plastic. I would also place hollow plywood or mdf boxes in the mold to create hollow spaces and reduce the amount of rammed earth needed. Then I would make the damp mixture and ram away. I would also embed some rebar in the structure as I went. Then remove the mold the next day.

After weeks of cure time for the rammed earth, I would cast an inch of EG to hold the steel plugs and rails, and then I would do the epoxy surface plate on top. I might even skip the EG layer and just do the steel insert and epoxy surface plate directly on the rammed earth. Or I might cast an inch of concrete on the rammed earth and then cast the epoxy surface plate.

I think this might be a really cheap alternative, which gets you a table that is massive, solid, and damping.

If you ever had to move the machine, just destroy the table and remove it. Then, cast another rammed earth table in the new location using local earth. All of the gantry, rails, motors, etc can be set up on the new table.

Any thoughts?

dfro

[roach]

let me get drunk ill blend you some

[roach]

[lgalla]

dfro,
could not have said it better; scamper to pay the rent.The floor is the cheapest way to go,no base or stand.You could park your car on the surface plate.Ramed earth is good.Ramed E/G better.A base or stand of concrete with a steel/E/G top
may be another route to go.Concrete under controlled conditions such as a shop,
not undergoing large temperature changes should be fairly stable and not crack.
The simple task of the base is to raise the tabletop so you don't have to bendover.
Larry

[dfro]

Larry,
Your response is encouraging.

I figure the base of any machine is the earth that the building is standing on, anyway. (I have heard of whole buildings being isolated on air cushions or springs, though.) So, why not make the machine base earth and take a few ringing, resonating, and very expensive pieces of steel out of the picture? Also, a rammed earth table/base would look really cool with the different color layers.

After building a small table top EG machine, I think I will try this approach on a larger machine. The epoxy surface plate idea you shared on the first page of this thread has completely changed my thinking on how to build these machines. It is so brilliantly simple - elegant.

It allows a builder to worry about precision at the right time. You make a decently square, flat mold - ram in the earth or EG - demold - and then pour an epoxy surface that is as as flat at the curvature of the earth anywhere you need it. There is no need for expensive extruded 80/20 aluminum, or ground steel parts all over the machine where it is not needed. You can be a little sloppy at certain stages in the build and then it is all trued up with a TT epoxy pour. Very elegant indeed!

I am going to try making a long straight edge reference using the TT epoxy technique, also.

Cameron,
I have done a little reading on patenting and trade secrets. I may be splitting hairs on your last post, but none of us have to worry about discovering someone's trade secret. Because a person has kept a formula secret, they have no claim to it. They can only hope that no one else replicates it for a long time while they enjoy an advantage in the marketplace. It is a gamble: do I patent my formula, publish it for all to see, and hold on to ownership of the idea for a limited period of time; or, do I keep the formula secret and hope it stays unreplicated longer than the time limit on a patent.

The only person who has to worry about revealing a trade secret is someone who has been privy to a formula or secret and has signed a nondisclosure agreement to a real or fictitious entity (how do you like that for some impressive legal wordsmithing?)

I very much appreciate you restating the open-source philosophy of this thread. It encourages me to share anything I may discover on this topic.

Dave

[Zumba]

We will get there faster with help as long as the help doesn't lead us to a formula that we can't use because it is somebody else's trade secret.

Regards all,
Cameron

I thought the only way for a company to keep a trade secret was to maintain confidentiality within the company? I don't think they'd have any legal recourse against a group of guys on an internet with no relation to the company. If they wanted legal protection, they would need to patent the formula, which would mean full disclosure of their secret to the public.

[Zumba]

Interesting link from Roach. He posted it as an image by accident but there's a URL in there.

http://www.zeeko.co.uk

Check out the machine specs under "brochures". The second largest machine specifically uses the term "epoxy-granite" which I found amusing.