[lgalla]

Jonixllc,
I thought from the thread beginnings that Epoxy Granite had the advantage of better vibration damping than real granite.I wonder from Walter's and others early tests about the majical 8% goal.Upon breaking,you can see that the aggregates broke.I would assume from this that the epoxy was stronger than the granite aggregates.The goal has been to have a castable granite with good vibrations,good good vibrations damping.If the goal is to duplicate natural granite,it would be cheaper to use a granite slab in the first place.
Larry

[jonixllc]

Jonixllc,
I thought from the thread beginnings that Epoxy Granite had the advantage of better vibration damping than real granite.I wonder from Walter's and others early tests about the majical 8% goal.Upon breaking,you can see that the aggregates broke.I would assume from this that the epoxy was stronger than the granite aggregates.The goal has been to have a castable granite with good vibrations,good good vibrations damping.If the goal is to duplicate natural granite,it would be cheaper to use a granite slab in the first place.
Larry

Here are my thoughts on damping.
Because all "granites" and all "epoxy granites" are not made of the same "stuff", damping ratios (zeta) can vary considerably
A popular "granite" to use for ultra precision machine bases and metrology platforms is "black impala". If you care to look at geology, igneous rock branches out into Gabbro and Granite. Black Impala "granite" is actually a Gabbro, specifically a Diabase which has very unique characteristics in that it is more dense than granite, less porous than granite and the big one, it has no grain. It's damping ratio can be comparable to impala black "granite".
My only point is that you have to be careful to sift though the claims of the epoxy granite manufacturers
As for the aggregate breaking before the epoxy. Where ever quartz is found, mica is found as well as they are both silicates only differing in the amount of oxygen. Mica has a grain that is always made perpendicular to a granite surface plates working surface. This reduces the granites overfall stiffness (If the grain was made parallel to the working surface, flecks of mica would continually migrate out of the surface). So, damping ratio would suffer as a result. Now, black impala "granite" has NO mica, therefore NO GRAIN. Black Impala "granite" is more dense than granite and has a more favorable damping ratio. So, if you were to epoxy an insert into granite, and do a pull-test to failure, the granite would break along the grain of the mica, not the epoxy bond.
One word on setting inserts into granite. The epoxy bond layer must be thin, the insert must have features on the OD to retain the insert and the hole in the granite must be rough.

[ckelloug]

Jonixllc,

Thank you kindly for your inputs, especially the 8% by volume number. I derived the 8% from first principles about a year ago using a semi-empirical particle packing model from Francois de Larrard's book. From the model, 8% is basically the limiting case where it becomes almost impossible by vibration and mechanical compaction to get the density any higher.

Based on stuff I remember seeing in the literature, an 8% mixture will not maximize damping however it will be good. What the 8% by volume epoxy mixture does is maximize is stiffness of the part. A 25% epoxy by volume mixture is predicted by the model in Kinloch's book to have a stiffness similar to that of pine which isn't exactly a wonder-material for machine tools.

I would be delighted to see the supplier of U.S. made inserts if you can post the company name.

As a note to the regulars here:

It has come to my attention from a friend on the Home Shop Machinist board that the early 20% of each Agsco component recipe was used for an article in this month's <u>Model Engineer's Workshop</u> to fill a mini-mill base. The epoxy used was too much for structural E/G and the basic formula was taken from Bob Warfield's site which copied the formula from our thread without attribution. At any rate, for a simple base filling project, the results were reported as very good.

Current Status:
On a general note, I am a few months out on having my lab ready to make some decent test specimens. My work on E/G has generated a lot of unrelated side projects. Before getting on with the testing program, I expect to revisit the packing model to verify that it is producing the best results it can. I then need to finish building my shake table out of the surplus vibrator I found at HGR industrial surplus and some steel plate and some vibration isolation springs. I also need to complete the installation of a fume hood for handling some solvents related to some work I have been doing. I would have liked to have been more active in this discussion lately but I've been on travel and then for the last week, my computer has been broken.

Finally, I want to make a big thanks to Michael Donaty from Sonics and Materials, the number one U.S. manufacturer of ultrasonic materials processing equipment . After showing him the work of myself and others here on this thread, he created a special package deal for me on a VCX 750 vibra-cell and the associated probes for dispersing nanomaterials. His generosity will allow me to perform and share some of the E/G related nanomaterials work I suggested over a year ago on this thread but could not implement.

As one of this thread's longer term members, I would like to thank everyone that has contributed and invite anyone who is interested or has suggestions or questions to keep posting. It's a slow process but an open formula for structural E/G matching the quality of the professional stuff will eventually result for everyone's contributions!

Regards all,

Cameron

[alex_ku]

meybe some one know links to seller/manufacturer (in EU) of insert nuts applicable for epoxygranite ?

I found it! Maybe this help to someone: http://www.rampa.de

[jonixllc]

Jonixllc,

Thank you kindly for your inputs, especially the 8% by volume number. I derived the 8% from first principles about a year ago using a semi-empirical particle packing model from Francois de Larrard's book. From the model, 8% is basically the limiting case where it becomes almost impossible by vibration and mechanical compaction to get the density any higher.

Based on stuff I remember seeing in the literature, an 8% mixture will not maximize damping however it will be good. What the 8% by volume epoxy mixture does is maximize is stiffness of the part. A 25% epoxy by volume mixture is predicted by the model in Kinloch's book to have a stiffness similar to that of pine which isn't exactly a wonder-material for machine tools.

I would be delighted to see the supplier of U.S. made inserts if you can post the company name.

As a note to the regulars here:

It has come to my attention from a friend on the Home Shop Machinist board that the early 20% of each Agsco component recipe was used for an article in this month's <u>Model Engineer's Workshop</u> to fill a mini-mill base. The epoxy used was too much for structural E/G and the basic formula was taken from Bob Warfield's site which copied the formula from our thread without attribution. At any rate, for a simple base filling project, the results were reported as very good.

Current Status:
On a general note, I am a few months out on having my lab ready to make some decent test specimens. My work on E/G has generated a lot of unrelated side projects. Before getting on with the testing program, I expect to revisit the packing model to verify that it is producing the best results it can. I then need to finish building my shake table out of the surplus vibrator I found at HGR industrial surplus and some steel plate and some vibration isolation springs. I also need to complete the installation of a fume hood for handling some solvents related to some work I have been doing. I would have liked to have been more active in this discussion lately but I've been on travel and then for the last week, my computer has been broken.

Finally, I want to make a big thanks to Michael Donaty from Sonics and Materials, the number one U.S. manufacturer of ultrasonic materials processing equipment . After showing him the work of myself and others here on this thread, he created a special package deal for me on a VCX 750 vibra-cell and the associated probes for dispersing nanomaterials. His generosity will allow me to perform and share some of the E/G related nanomaterials work I suggested over a year ago on this thread but could not implement.

As one of this thread's longer term members, I would like to thank everyone that has contributed and invite anyone who is interested or has suggestions or questions to keep posting. It's a slow process but an open formula for structural E/G matching the quality of the professional stuff will eventually result for everyone's contributions!

Regards all,

Cameron

Rock of Ages in Graniteville, Vermont - Speak to Mike Caputo
This is where the proprietary nature of insert placement comes into play
RofA has developed a procedure that they are reluctant to share - although I think they would sell you inserts
They have determined the best bond thickness, type of bonding agent, etc
Mike is very knowledgable

[ckelloug]

Alex,

The RAMPA stuff looks more appropriate to wood to me. Any second opinions?

Jonixllc,

Thanks for the reference to rock of ages. I've got a big surplus solid granite plate made by them but I didn't realize they also did E/G.

Regards all,

Cameron

[jonixllc]

Alex,

The RAMPA stuff looks more appropriate to wood to me. Any second opinions?

Jonixllc,

Thanks for the reference to rock of ages. I've got a big surplus solid granite plate made by them but I didn't realize they also did E/G.

Regards all,

Cameron

Rock of Ages DO NOT do E/G - they do have inserts

These inserts are not for granite or epoxy granite
An insert for granite or epoxy granite is essentially a solid round of steel or stainless steel with essentially a circumferential set of milled grooves and a vertical set of milled grooves. The insert is sized like the following: An M10 threaded insert would have an OD of 19mm - so multiply the OD od the thread X2 to get the OD of the insert
The hole that the insert goes into should have no more than 0.13mm radial clearance - this keeps the epoxy bond layer thin and strong

[alex_ku]

well, seems like you rigth guys.
so, i'll use something like this.
it cheap and strong enought.

[Herbertkabi]

Look at pressed polymer Granite panels like OKITE (Italy) made for:
shower and tub surrounds, bathroom vanity tops, writing desks, table tops, partition wall,
shower walls, wall cladding, windowsill, fireplace mantles and surroundings, food service areas, wainscots and wall bases, elevator cab walls, Antibacterial properties
OKITE&#174; Quartz Surfacing has been certified by NSF as an antibacterial product. Differently than other surfacing products, OKITE&#174; does not need any sort of chemical agent, during the manufacturing process or during its lifetime, to keep its antibacterial properties. Thickness 13mm, 20mm and 30mm,

OKITE&#174; is a specially developed quartz based surfacing material (about 93&#37; quartz and 7% polyester resin) made in Italy by Seieffe Srl.

Weight of OKITE&#174;:
&#189;” (13 mm) slab : 301 lbs. (136.5 kg) equal to 6.57 Lb/SF (31.85 kg/Square Meter)
&#190;” (20 mm) slab : 463 lbs. (210 kg.) equal to 10.10 Lb/SF (49 kg/Square Meter)
1” &#188; (30 mm) slab : 695 lbs. (315 kg.) equal to 15.15 Lb/SF (73.5 kg/Square Meter)

Density kg/mc 2283.0
Bending Strength Mpa 48
Flexural Strength N 3371
Compression Strength N/mmq 159
Deep Abrasive Strength mm 26.6
Surface Hardness MOHS 6
Linear Thermal Expansion Coefficiency 10-6 &#176;C-1 27.4
Dimensional Stability mm 0
Impact Strength Joule 1.9

There are different types - marble, granite etc ...
I bought 1000mm x 1000mm x 30mm dark gray Granite to examine this material and try to cut - it looks and feels like real Granite,
Diamont tools make it easy to cut edges, holes, slots ... grinding ...
It may be complecated at home but I will do it in one StoneMaster worksop - they will cut all needed parts, they are able to make it precise. Its easy to glue, to make thick and reinforced sandwich panels with aluminium (I will) ...
Of course Im not 100% sure - my first try was just I cut 1000mm x 100mm x 30mm strip and to broke it - its really strong :idea: and then drilled few perfect holes through.

Cheers,
Herbert

[brunog]

Alex,

The RAMPA stuff looks more appropriate to wood to me. Any second opinions?

Cameron,
Actually the dowel nuts with the large heads could be of some interest however I personally prefer using threaded rod couppling nuts available just about anywhere and combining them to a flat washer and short hex bolt at one end. (as per Alex Ku's earlier post)

BTW Cameron, nice work! I still check the thread about once or twice a week, I am busy doing renovations these days including a 15' x 25' workshop in the basement for future projects(includung EG)

Best regards

Bruno

[ranchak]

Hi Guys, I have been interested in using E/G to fill my column on my RF-45(I saw somebody did that here already) also I am building a frankenstein mini mill out of a Grizzly X2 that I will use E/G on. I have been through the first 108 pages of this post, but there are a few things that I don't agree with. Now don't start shooting, First I think using rounded particles is a mistake. When you build a roadbed you don't use marbles, you use material of varying sizes (already being used in the E/G tests done here), but more importantly the materials have jagged edges. Now, the sizes of particles that are being used here will lock together better than rounded edged particles. If you were working with rock sized pieces I would agree that you would have large voids, but these particles are very very small pieces. These will lock together better, be stronger and since there will be no piece the same there will less chance of harmonics building up. Matter of fact sandblasting sand and filter sand are not round but have jagged edges. Starblast is a crescent shaped material, manufactured from lava.

Secondly how long is the E/G mix being mixed? The epoxies that we are looking at using have a pot life of 30 minutes to 400 minutes. Are we allowing sufficient time to allow the epoxy to mix through the aggregate? Using a mechanical mixer and mixing the aggregate first, then adding colorant and finally the epoxy.

A great place to buy epoxy and colorant is www.jgreer.com .

Also I would think by adding fiberglass fibers to the mix. This is the type of fibers used in concrete, can be purchased at any concrete plant. If the fibers are added first and then the fine aggregate second you will start to break up the fibers into smaller pieces. Continue to add more aggregate untill all of the aggregate is mixed, the fibers should be really small and shredded by now. Add the epoxy and mix some more.

The shear tests that Walter (I think it was Walter) did on his samples I think do not represent what will happen under operating conditions. He used a sharp point to break his samples, placing all of the stress in a very small area. Even high strength concrete will break under those conditions. I think by using the sharp edged aggregate and fibers will make a difference. In real life the stress will be over a larger area, take for instance a bearing truck, the stress is located over the base of the truck. How big the base is I don't know but some of the THK and HiWin trucks I have are about 3.5 to 4" long. That puts that stress in a whole different area.

Also if a E/G base, gantry or whatever is going to built it will have to be thicker than if it were to be constructed from steel, aluminum or cast iron.

I think that there is a great future for E/G, I also think that there are some guys that have done a tremendous amount of research here and have laid a great foundation for others to follow. I plan on starting with the column on my mini frankenmill and then try to cast some pieces using decomposed granite, sandblast sand and glass fibers. I will probably not de-gas my epoxy, but I will use a vacuum to pull excess epoxy and air out of the mix.

Also, we do not have to pour in one pour, as long as the first "layer" hasn't fully cured another layer will adhere to it. There would be a few bonuses to this. First would be time to mix and compact the E/G. Second would be allowing the air to escape through the thinner layer of E/G. Finally the next or following layers can be compacted better than if done in one pour.

Like I said earlier, I have only read the first 108 pages so some of these points may have been already addressed. If I have offended anyone I appologize, that was not my intentions.

[jonixllc]

Hi Guys, I have been interested in using E/G to fill my column on my RF-45(I saw somebody did that here already) also I am building a frankenstein mini mill out of a Grizzly X2 that I will use E/G on. I have been through the first 108 pages of this post, but there are a few things that I don't agree with. Now don't start shooting, First I think using rounded particles is a mistake. When you build a roadbed you don't use marbles, you use material of varying sizes (already being used in the E/G tests done here), but more importantly the materials have jagged edges. Now, the sizes of particles that are being used here will lock together better than rounded edged particles. If you were working with rock sized pieces I would agree that you would have large voids, but these particles are very very small pieces. These will lock together better, be stronger and since there will be no piece the same there will less chance of harmonics building up. Matter of fact sandblasting sand and filter sand are not round but have jagged edges. Starblast is a crescent shaped material, manufactured from lava.

Secondly how long is the E/G mix being mixed? The epoxies that we are looking at using have a pot life of 30 minutes to 400 minutes. Are we allowing sufficient time to allow the epoxy to mix through the aggregate? Using a mechanical mixer and mixing the aggregate first, then adding colorant and finally the epoxy.

A great place to buy epoxy and colorant is www.jgreer.com .

Also I would think by adding fiberglass fibers to the mix. This is the type of fibers used in concrete, can be purchased at any concrete plant. If the fibers are added first and then the fine aggregate second you will start to break up the fibers into smaller pieces. Continue to add more aggregate untill all of the aggregate is mixed, the fibers should be really small and shredded by now. Add the epoxy and mix some more.

The shear tests that Walter (I think it was Walter) did on his samples I think do not represent what will happen under operating conditions. He used a sharp point to break his samples, placing all of the stress in a very small area. Even high strength concrete will break under those conditions. I think by using the sharp edged aggregate and fibers will make a difference. In real life the stress will be over a larger area, take for instance a bearing truck, the stress is located over the base of the truck. How big the base is I don't know but some of the THK and HiWin trucks I have are about 3.5 to 4" long. That puts that stress in a whole different area.

Also if a E/G base, gantry or whatever is going to built it will have to be thicker than if it were to be constructed from steel, aluminum or cast iron.

I think that there is a great future for E/G, I also think that there are some guys that have done a tremendous amount of research here and have laid a great foundation for others to follow. I plan on starting with the column on my mini frankenmill and then try to cast some pieces using decomposed granite, sandblast sand and glass fibers. I will probably not de-gas my epoxy, but I will use a vacuum to pull excess epoxy and air out of the mix.

Also, we do not have to pour in one pour, as long as the first "layer" hasn't fully cured another layer will adhere to it. There would be a few bonuses to this. First would be time to mix and compact the E/G. Second would be allowing the air to escape through the thinner layer of E/G. Finally the next or following layers can be compacted better than if done in one pour.

Like I said earlier, I have only read the first 108 pages so some of these points may have been already addressed. If I have offended anyone I appologize, that was not my intentions.

I have been designing and using epoxy-granite machine bases since 1989. All of the above has been tryed over and over again. The bottom line is to do the up-front engineering, letting the epoxy-granite manufacturer of your choice produce the base. There is no substitute for FEA, good engineering judgement and a knowledgable vendor.

[ckelloug]

Hi Guys, I have been interested in using E/G to fill my column on my RF-45(I saw somebody did that here already) also I am building a frankenstein mini mill out of a Grizzly X2 that I will use E/G on. I have been through the first 108 pages of this post, but there are a few things that I don't agree with. Now don't start shooting, First I think using rounded particles is a mistake.

When you build a roadbed you don't use marbles, you use material of varying sizes (already being used in the E/G tests done here), but more importantly the materials have jagged edges. Now, the sizes of particles that are being used here will lock together better than rounded edged particles. If you were working with rock sized pieces I would agree that you would have large voids, but these particles are very very small pieces. These will lock together better, be stronger and since there will be no piece the same there will less chance of harmonics building up. Matter of fact sandblasting sand and filter sand are not round but have jagged edges. Starblast is a crescent shaped material, manufactured from lava.

There is no shooting here. Constructive criticism is very welcome.

The rounded vs. angular particles argument is an interesting one with several aspects. The models from Advances in Structural Resins and Primers from A.J. Kinloch demonstrate without a doubt that the single most important parameter is the percentage of aggregate. The models from Francois de Larrard in Concrete Mixture Proportioning: A Scientific Approach show decisively that rounded particles maximize aggregate percentage. Therefore, it can be said to a high degree of certainty that the use of rounded particles will make the mixture with the highest modulus aka stiffness. It should also be noted that the relationship between aggregate percentage and stiffness is extremely nonlinear such that the last few percent of aggregate fill from the mid 80%'s to the low 90%'s means the difference between a material as stiff as pine and one half as stiff as steel.

Stiffness is not the whole story however. The papers I've pulled on aggregate interlock indicate that interlocking angular particles are somewhat better for the ultimate tensile strength of the material due to the fact that they tend to help hold a crack together. In general, if you are designing a part that is anywhere close to having a crack in it, you have made a big mistake so I personally discount the importance of interlock in epoxy granite.

I also highly suspect as the epoxy percentage goes down, the importance of aggregate interlock goes down. This leaves me with the reasoned but by no means definitive opinion that finding an available material that has the correct grading to achieve maximum density with as low a cost as possible provides the ultimate determining factor as to round or angular particles.

If you want to test this experimentally for the benefit of the thread, I will gladly run the samples on my test column for flexural strength and flexural modulus.

Depending upon the shape of the aggregate and some easily obtained packing density numbers, one can tailor a mixture of any shape of particles to obtain maximum density via a numerical packing model such as the one presented by de Larrard. I've got an implementation of the model working but the optimizer is broken right now so the best formula I've posted in terms of density is the simple one. It is however prone to segregation under vibration.

Secondly how long is the E/G mix being mixed? The epoxies that we are looking at using have a pot life of 30 minutes to 400 minutes. Are we allowing sufficient time to allow the epoxy to mix through the aggregate? Using a mechanical mixer and mixing the aggregate first, then adding colorant and finally the epoxy.

A great place to buy epoxy and colorant is www.jgreer.com .

The epoxy combination most investigated here has been reichhold 37-127 with 37-606 which are available from www.uscomposites.com at a lower price than the green formula from Jgreer. The hardener is not ideal in terms of physical properties however as the stiffness is about 25% lower than what's obtainable with some fo the other stuff I've worked with. My current target epoxy formula is Hexion 813 with Degussa Isophorone Diamine as the hardener. Beyond lab sized samples however, I know of no place one can easily get either of these components.

I also think that ultimately, Either something like dow corning z6040 siloxane (now Xiameter OFS-6040) or some titnates from Kenrich petrochemicals will be valuable for coupling and microvoid prevention along with some BYK A525 for air release.

Finally, this quote from a post by rowbare is the most current aggregate formula I am particularly confident in. Like I said wlesewhere in this post, I am confident that my simulator is predicting correct densities but I am having some problems with the optimizer so I'm not so sure about the optimal nature of some of my more recent aggregate formulas. I've gotta fix that simulator when I get some free time.

http://www.cnczone.com/forums/showpo...postcount=3423


The A and B parts of the Epoxy have to be mixed thoroughly before adding aggregate. The french paper I summarized and attached several pages back provided an excellent discussion on mixing methods. In short, according to the literature, you need to mechanically mix the epoxy components, mechanically mix the aggregate and the epoxy, and then finally placed the mixed material in a mold and vibrate the entire mold at an acceleration of of between 2g and 4g.

Also I would think by adding fiberglass fibers to the mix. This is the type of fibers used in concrete, can be purchased at any concrete plant. If the fibers are added first and then the fine aggregate second you will start to break up the fibers into smaller pieces. Continue to add more aggregate untill all of the aggregate is mixed, the fibers should be really small and shredded by now. Add the epoxy and mix some more.

Short fiber reinforcement is a good thing but it will effect the mixture packing density. Done in the "hypothetical superlatively wrong way" that Murphy's law would lead one to, it could potentially lower the strength and modulus. Done in the right way, it's undoubtedly a help but I haven't investigated it beyond noticing that extra terms can be added to the particle packing models to account for fibers. I would assume that it is a generally good thing unless one found the "Murphy Certified" unlucky combination.

The shear tests that Walter (I think it was Walter) did on his samples I think do not represent what will happen under operating conditions. He used a sharp point to break his samples, placing all of the stress in a very small area. Even high strength concrete will break under those conditions. I think by using the sharp edged aggregate and fibers will make a difference. In real life the stress will be over a larger area, take for instance a bearing truck, the stress is located over the base of the truck. How big the base is I don't know but some of the THK and HiWin trucks I have are about 3.5 to 4" long. That puts that stress in a whole different area.

A three point bending test in accordance with the ASTM D790 flexural test standard is the cheapest and easiest way to get initial an initial characterization of materials. In an ASTM D790 test, 3 contact points with very specific tip radii are used to bend the sample until it breaks. This test is not used for concrete because it would be difficult to cut the samples as well as the fact that concrete is used mainly in a manner where it's compressive strength is of importance. Concrete would break easily in a 3 point bend test because unlike E/G, it has very very little tensile strength.

Your point about unrealistic testing has some merit but the beautiful part of science is that when you measure something in known conditions and you know how that measurement applies to other circumstances in which you cannot take a measurement, you can understand what will happen in the unknown circumstance without performing an actual test. Walter's tests were admittedly crude but he was creative in doing them at low cost and did demonstrate that some sample configurations were slightly better than others.

I offer free ASTM D790 tests to anybody on this thread that wants to know what the flexural modulus and strength of their samples are. More specific tests such as compressive, tensile and shear tests require much more expensive equipment and I do not have those facilities available.

Also, Alexander Slocum in Precision Machine Design suggests that rolling element bearings should not be used in direct contact with E/G due to wear issues but I think that for home shop applications, it might be alright due to the much lower usage than in industrial machines.

Also if a E/G base, gantry or whatever is going to built it will have to be thicker than if it were to be constructed from steel, aluminum or cast iron.

This is a given. I have been doing some FEM analysis on the giant plates that user MBK asked about a dozen or so posts back as a training project for the finite element analysis software I recently acquired. I can assure everyone that copying a heavily loaded cast iron part in E/G and expecting it to carry the same loads would be disasterous both due to the difficulty of making good E/G parts with small cross section and due to the fact that certain stresses in the original part without optimization appear right near the failure point for my hypothetical E/G recipe.

I think that there is a great future for E/G, I also think that there are some guys that have done a tremendous amount of research here and have laid a great foundation for others to follow. I plan on starting with the column on my mini frankenmill and then try to cast some pieces using decomposed granite, sandblast sand and glass fibers. I will probably not de-gas my epoxy, but I will use a vacuum to pull excess epoxy and air out of the mix.

Also, we do not have to pour in one pour, as long as the first "layer" hasn't fully cured another layer will adhere to it. There would be a few bonuses to this. First would be time to mix and compact the E/G. Second would be allowing the air to escape through the thinner layer of E/G. Finally the next or following layers can be compacted better than if done in one pour.

Like I said earlier, I have only read the first 108 pages so some of these points may have been already addressed. If I have offended anyone I apologize, that was not my intentions.

No apologies necessary although the last 200 or so pages are much better than the first 108 in terms of an understanding formulating. Thanks for participating in this rather esoteric pursuit. I think I can speak for most of the regulars in saying we'd be glad to help if we can.

I would definitely recommend making a few test parts before trying to cast a large column in order to debug your procedures as I remember Walter learned a lot from his first few experiments. I've only made one actual E/G test part up to this point as my focus has been mainly on the material design as opposed to implementation. The real killer of E/G for the home shop is to make production quality parts requires a vibrator capable of moving the entire part and the mold at an acceleration of at least 2g.

At any rate, several of us here have probably made some of the mistakes, at least in test samples, that are in store for you so please don't hesitate to post and get 50 opinions about your procedures and formula if you think we can help


Regards all,

Cameron

[ranchak]

Hi Cameron, thanks for your insight. I wasn't able to find the epoxy on the US Composite site, their prices seem a bit lower the jgreer, but I would have to figure in the shipping. I'm located in CA and shipping is pretty cheap from jgreer. I plan on making some samples today or tomorrow with the epoxy that I got, I will keep you (and others) with my results.

I agree with the fact that you can place more of a round shape vs. a irregular shape in the same given area, but I still think that due to the small (extremely small) size of the particles that this is almost unmeasurable. I think also that the benefit of the irregular shaped particles interlocking outweigh the minute difference in the "count" of particles that will fit in the same given space.

I have more to write, but I'm working on about 3 hours sleep and I'm having difficulty thinking straight. I'll get back to you later, Ron

[ckelloug]

Hi Cameron, thanks for your insight. I wasn't able to find the epoxy on the US Composite site, their prices seem a bit lower the jgreer, but I would have to figure in the shipping. I'm located in CA and shipping is pretty cheap from jgreer. I plan on making some samples today or tomorrow with the epoxy that I got, I will keep you (and others) with my results.

The epoxy on the us composites site is just called low viscosity with slow hardener. It is definitely not the best epoxy for E/G, only the one that we know the most about. I have run flexural tests on samples of this epoxy and IIRC, it has a flexural modulus of about 375,000psi.

The best stuff I've worked with by picking an optimal low viscosity epoxy and trying multiple hardeners is about 475,000psi and higher moduli are available although most of these epoxies harden too fast to be of interest.

I agree with the fact that you can place more of a round shape vs. a irregular shape in the same given area, but I still think that due to the small (extremely small) size of the particles that this is almost unmeasurable. I think also that the benefit of the irregular shaped particles interlocking outweigh the minute difference in the "count" of particles that will fit in the same given space.

This assumption while logical is not actually correct. Particle packing is a function of the shape of the particles rather than the size of the particles in an infinitely large container e.g. The average packing density of marbles will be the same as basketballs in an infinitely large container.

Packing density is a function of the shape of the particles and the ratios between the different sizes but not the absolute size of the particles in an infinitely large volume.

The reason this does not seem so intuitively is because edge effects at the wall of the container are dependent on the ratio of particle size to the distance between the edges. In general, more fine particles are needed in an optimal mixture to fill small containers than in infinitely large ones. The rule of thumb for this effect is that it starts to become negligible when the diameter of the container is 5 times the size of the largest particle according to de Larrard's book.

You might also have a look at post 3119 showing the model for modulus obtained from Kinloch's book. In general, the packing density matters a great deal. Since the models have been heavily tested with empirical data, I am fairly well convinced that anything that the model says lowers packing density by a few percent is a disaster. Also, note that when given a reasonable modulus epoxy and as high a particle packing density as is reasonably obtainable, the model gets Accures's published modulus!
See
http://www.cnczone.com/forums/showpo...postcount=3119

I have more to write, but I'm working on about 3 hours sleep and I'm having difficulty thinking straight. I'll get back to you later, Ron

Yup been there before.

--Cameron

[Eric R.]

hi all!

I need some help:
meybe some one know links to seller/manufacturer (in EU) of insert nuts applicable for epoxygranite ?
I had one but lost link and cant find it any more

Thanks!

There are two main methods to apply inserts:

Method 1) NOT RECOMMENDED! First cast the E/G and after curing drill holes and place the inserts. This has some major drawbacks: (a) drilling holes in a cured products may not be very accurate and (b) it may damage the E/G. Also, after you have drilled the holes, you need to apply the inserts by either pressing them into place (which is more appropriate for wood and plastics) or by glueing them.

Method 2) RECOMMENDED! Imo a much better option is to pre-mount them in your mold and then cast the E/G. For this you will need inserts that have been developed for casting purposes, as where most inserts (including those from rampa.de) are for wood or other soft materials and which are applied by drilling/screwing and/or pressing (method 1). Here is a manufacturer that has a nice collection of inserts for casting purposes: www.anchorinserts.co.uk.

The image below is an example of a blind (one side is closed) insert and its cross-section.



Regards,

Eric

[ncmeinc]

Try Philadelphia Resins I talked to them about doing a big frame router and they said it would be more rigid than the steel weldment. The biggest plus is vibration dampning.



ncmeinc

[Epikur]

I am planing to make a 18000rpm lathe for max ø152mm dia. and have found a seriouse german company who supplyes the right solutions for me.

check out : http://www.demmeler.com/pdf/DemTec.pdf

Good luck from norway

[greybeard]

.........18000rpm lathe for max ø152mm dia. .......

Good grief.......50,000G

(chair)

John

[jonixllc]

Good grief.......50,000G

(chair)

John

Actually, this isn't too bad, but of course it depends on what the part looks like.
Better be able to balance at speed