[jsage]

Zumba,

Very nice.

I think with the higher end process of post cure or the process of calorific absorption will suck in the excess. I boat building you get fiberglass pattern showing through when you use dark colors bringing the temp over 140 which draws in the epoxy (calorific absorption). Problem with deep colors like black. Obviously just discussing a concept. Heard it first hand from a chemical engineer involved in boat building. Not a common concept.

I also vaguely remember that it might be better to have temps increasing to constant rather than the opposite, decreasing.

mike

[martinw]

I was thinking that the tetris thing should be done on the aggregate BEFORE the epoxy is added to the mix. Once the epoxy is added, expecially at a 1:10 weight ratio (or 1:14 in the case of the Silestone/Zodiac), the high viscosity would probably prevent any significant shifting of the aggregate. At that point, all you can do is get rid of the air bubbles.

Besides... lets say you had an E/G mixture with the perfect viscosity at the time of pouring. Then somehow, using vibration, all the aggregate fit together perfectly and sank to the bottom. Wouldn't you end up with a pool of empty epoxy at the top?

Dear Zumba,

I've been puzzling over the rates at which different sized particles of the same density will settle in a fluid. For example, if you put a fine sand/pebble/water mix in a bucket and stirred it up, as soon as you stop stirring, the pebbles go to the bottom almost instantly, while the sand stays in suspension for a lot longer. Eventally,however, you will have pure water at the top. I think that this is because a sand particle has a larger surface area to volume ratio than the pebbles, and therefore there is greater friction which slows its sinking. I guess that with an epoxy mix, the thing to aim for is an epoxy viscosity that is sufficiently great to slow this sinking effect, so that it sets before appreciable sedimentation occurs.

I may be entirely wrong and I may be stating the obvious. If so apologies.

By the way, I am not in a position to comment on the beauty of your samples for the reason stated previously.

Best wishes


Martin

[walter]

The beauty is definitely there, Martin! Oh, just look at the blue one..

EDIT:
Zumba, here's a puzzling picture (ITW Polymer Castings/Zanite):



They seem to be pouring it into a mold. Very dry mix.. I think epoxy is in there already?
...

[martinw]

The beauty is definitely there, Martin! Oh, just look at the blue one..

Dear Walter,

Alas, there is no Smilie for "contemptuous snort"....

Best wishes

Martin

[walter]

From ITW:

About Zanite®
What is Zanite® polymer composite?

"Zanite® polymer composite is a formulated composite material designed for casting machine bases and other structural components. It is a combination of epoxy, quartz aggregate and selected additives..."
...

[jsage]

Zumba,

Again great work, took a closer look. Walter thanks for pounding the pavement or Epoxy Composite. I like that DIY VAC unit.

[djshop]

I am just jumping into this discussion. I skimmed many of the posts but there are 50+ pages! I have a CMS lathe built by upgrade technologies that has a cast polymer structure. I am working on a new purpose-built CNC lathe and was contemplating a composite base either molded or filled structural weldment. If I was to go the mold and casting route, is the composite structure machinable/grindable? What is the thought process for attaching linear rails and headstock? do you cast in inserts and then machine pads for the rails? Or do you use grout to level them?
I am on about a 6-9 month timeframe for this project. I plan to work out the basic controls on a converted Hardinge lathe and then transfer components to the new base.
This is a great site.
Dave

[Zumba]

Testing day!

I had four test blocks... one of them still had a paper cup bottom stuck to it. Guess which one was tested to destruction?? :boxing: :boxing:

I went out on the lawn, got a piece a 4" steel channel, placed the composite block on the channel, and started hammering at it with a mallet. Didn't really do anything but chip off the sharp corners. Then I whipped out the sledge hammer. It took a pretty heavy blow to get this thing to crack in half.

You can see the large amount of air pockets inside.

[walter]

If I was to go the mold and casting route, is the composite structure machinable/grindable? What is the thought process for attaching linear rails and headstock? do you cast in inserts and then machine pads for the rails?

Dave, good to have you on board.

I don't think the Epoxy/Granite is machinable. Have a look at this German design, there are ways to solve this.

EDIT: Also check out:

Article in post #541 (page 46)
E/G Tips&Tricks in post #364 (page 31)
Useful links in post #241 (page 21)
...

[merl]

Hey guys, I can wiegh in here with some practicle experience with the end product of this process.
I have a small gang tool, cnc, turning center made by Compact Machine Systems at my shop and I will vouch for the speed snd accuracy of the machine. It will hold sub tenth (fifth decimel place) tols. all day on any kind of material I need to run through it. We have a bar feeder for it but, seldom use it because it makes too much noise.
The base of the machine is entirely made from an epoxy concreation with some mechanical eliments cast in and some added after cure.
The whole machine fits in a cube of approx. 4'x4'x4.5' and weighs 3500 lbs.
I'd rather replace the Mitsubichi controle with a bucket of rusty nails but that's just me grumbling. Give me an Anilam 4000 any day...

[djshop]

We have a bar feeder for it but, seldom use it because it makes too much noise.

I also have a CMS. Mine has a Fagor 8055 controller which is pretty good but then it is the only one I have used. It also has an autobar 300 bar feeder that uses some UHMW bearing donuts as a mid-bar support. Sometimes they work well. Other times they sound like squeeling pigs on a PA system. I end up using 2 foot bars so it loads them into the spindle liner only.

The polymer base is quite nice though.
Dave

[djshop]

Have a look at this German design, there are ways to solve this.

Thanks for the great summaries. From what I can gather from the German design they are using a mold with machined pads prior to pouring the polymer. The sides have anchors which are embedded into the polymer base. In the picture prior to pouring I am not sure I understand what all I am looking at. What are all of the parallel white lines in the base? Is this some type of sub-base? It looks like the rails are set into it. It appears that there must be a set of spacers attached to these rails. (maybe it is just the perspective of the picture) Is the copper pipe there for coolant draining?

Dave

[Geof]

... On the other hand high frequencies could sink larger aggregates or prevent them from penetrating as the smaller particle fill more effectively....

I think it is possible you have it sort of backwards here. I would expect that low frequencies could excite bulk movement of the constituents of the mix and maybe encourage separation and settling; high frequencies could be expected to cause vibration within the particles promoting release of the air bubbles adhering to the surfaces. Whether the particle tended to move as one unit, the bulk movement, or just vibrate, would depend on the wavelength of the vibration in the mix and this depends on the speed of sound in the mix.

[jsage]

Geof,

Thanks. I was just wondering b/c From concrete work I recollect that larger aggregates will move to the bottom if hit with mallets for too long of period. At the same time, there is a subthread where the large aggregates came to the top when a vibrating sander was used.

Liquefaction from earthquakes. People caught in avalanches. Ultra long landslide runouts ; ) Just trying to relate to this application. Obviously, I am taking a non physics approach and asking the question ; )

Thanks again.

Mike.

[Geof]

Geof,

Thanks. I was just wondering b/c From concrete work I recollect that larger aggregates will move to the bottom if hit with mallets for too long of period. At the same time, there is a subthread where the large aggregates came to the top when a vibrating sander was used.

Liquefaction from earthquakes. People caught in avalanches. Ultra long landslide runouts ; ) Just trying to relate to this application. Obviously, I am taking a non physics approach and asking the question ; )

Thanks again.

Mike.

All low frequency, some ultra-low frequency...except for the ultra long landslide runout.

I have read a couple of proposals for explaining long runouts:
One is that air gets entrained in the rubble and both decreases the bulk density and acts an an air cushion because it can't get squeezed out quickly.

The other explanation, which I favor, is that the particles in the landslide are vibratin; ringing like bells you could say. This means that they do not reside in contact with each other for friction to take effect; they constantly bounce off each other and thus keep running down even a small slope or out onto flat just from their own momentum.

This is not directly applicable to the behaviour of aggregate/epoxy under vibration but is partly why I suspect there would be a frequency dependence because things vibrating internally can behave differently to things that are simply moving in one direction or oscillating as a single unit.

[lgalla]

Wow
I am away a day and there is a flood of new posts and members viewing.I hoped to stay away from this thread for a week while at a trade show in Frankfert but too much is happening here.Hope to answer questions without pasteing quotes.
Concrete vibrators are anywhere between3400to13000VPM and recommended 30 sec.or sinking of larger aggreates may occur or the reverse.Vibrated concrete is good at acheiving 7% air volume.Vacuum would be much lower.
Epoxy will pool on the top after compaction.Just sprinkle quartz sand to suck up the excess.
"I can't see E/Q self leveling" Correct.For a surface plate the epoxy should be neet or no coarse filler as the final pour.
Engineered stone or quartz counter tops are a different animal.They are polyester resins and quartz.Our epoxy/quartz will surpass their specs.
In general fast epoxy may yellow or burn and gass from excessive heat.Stick with slow cure.Also fast cure epoxyies[5min]tend to be brittle.Sorry for little time,will try to answer direct questions.
Larry

[jsage]

Geof,

Thanks, it occurs to me that is twice my lack of clarity and run- ons got me in trouble ; )

Igalla,

Welcome back. I think one part that is missing is what was brought up and dug into by Walter. The product previously mentioned appears to be using something equivalent to a prepreg or related a solid type epoxy (powder perhaps) that is catalyzed by high heat. Generally, it may be out of scope, requiring autoclave or other means, but does address some of the issues we have been discussing.

Zumba, I think the air pockets look acceptable. Unless you want to use a electron microscope so we can try to determine the smoking gun ; ) I'll be keeping an eye on you to make sure you don't turn your work into a multi million dollar industry ; ) Woodcraft dyes, cool, looked at them, now I know where to use them. You make sand and epoxy look good, eh Martin.

[walter]

Well, I dug up another document...

***
"...Relatively recently a technology for the manufacture of conglomerate slabs, referred to overall as "Bretonstone" technology, has been proposed and implemented on an industrial level. This technology consists essentially in the preparation of a mix comprising granules of one or more natural stone materials or equivalent artificial materials and a binder, chosen from among natural cement binders and synthetic resins.

This mix is deposited on either a temporary support or inside a tray-like mould and subjected to a vacuum compaction step, with the simultaneous application of a vibrating movement(...)

In the case(...) of a synthetic resin based binder, such as for example a polyester resin or an epoxy resin, the setting step may be performed in a very short time, by heating the rough slab, if necessary with the aid of a catalyst.

EXAMPLE
- A single polyester resin has been used in the two mixes indicated below. Composition (% by volume) of the visible thin layer: Polyester resin: 18% Fine quartz dust: 22% Quartz granular material, 0.1-2.5 mm 60% Composition (% by volume) of the light thick layer: Polyester resin: 18% Fine cristobalite powder: 18% Expanded glass in granules of 0.2-4.0 mm: 64%

- The mix of the first layer (visible side) was divided and coloured in three parts, one of which black and the other two using a coloured paste, so as to make full use of the transparency properties of quartz.

- The first mix (visible side) was deposited on a rubber sheet having a thickness of about 4 mm and reinforced with a glass meshwork, performing the deposition through a sieve of 8 mm thickness having meshes of 50.times.50 mm.

-A web of continuous glass filament having a weight of 300 g/m.sup.2 and impregnated with polyester resin in an amount of 300 g/m.sup.2 was deposited on the first mix layer.

- After screening the second mix (i.e. that containing the expanded glass granular material) a second rubber sheet was applied and a vacuum pressing performed at a pressure of a few bars, applying at the same time a vibratory movement with a frequency of between 2,000 and 4,000 Hertz. At last, the resultant rough-finished article was subjected to the catalytic setting step at a temperature of between 80 and 150.degree. C.

http://www.freepatentsonline.com/20060283136.html
...

[jsage]

Walter,

I just did a lengthy search myself. I came up with hybrids, patents etc. I found one epoxy based casting element that had the same characteristics mentioned.

Lot of very high tech ones. I think that is why they are so expensive. One challenge was something called zoning where if the temperature is not constant then the finished product doesn't realize full strength. There is also a fragile stage after the heat driven crosslinking is complete and the cast cools.


You can cure it in a couple hours at 180 c or 20 hours at a slightly more reasonable temperature.


I'll need to reread your post I'm bleary eyed.

[walter]

One challenge was something called zoning where if the temperature is not constant then the finished product doesn't realize full strength.

I just realized it's totally different process- Larry was right.
I guess we don't need the high frequency...


"...When quartz particles reach the plant they are loaded into a hopper where they are separated according to size and color, and stored in silos. At the time of manufacture the quartz crystals are combined with silica and resin (resin content ranges between 6 and 10 percent of the total mixture) in a vat that resembles a large bread mixer. The resulting mixture has the look and feel of moist sand. It is dumped into a metal form resting on a table lined with release paper, where it is molded into the shape of a thick slab. This is in preparation for entering the vibro-compactor.

*There’s A Whole Lotta Shakin’ Goin’ On*
Even though the vibro-compactor is physically the least imposing piece of equipment in the production line, it is the most important. It is here that the elements of vibration and pressure combine to turn a pile of damp sand into a compact slab. The compaction process begins as the loosely molded mixture is conveyed into the unit, which lowers itself onto the slab. When the machine is activated the floor shakes as the vibro-compactor noisily lives up to its very descriptive name. The commotion continues for slightly less than two minutes.

Emerging from the opposite end of the vibro-compactor is one lean and mean engineered stone slab, although it still lacks bonding strength. For that it must undergo 30 minutes in a heat press, which activates and subsequently cures the resin binder. After leaving the press, the slab is stacked vertically on a rack, where it finishes its cure cycle for a minimum of 24 hours before undergoing the sanding and finishing process."

http://www.surfacefabrication.com/Si...ant%20Tour.htm
____________________________________________

"...The resulting mixture has the look and feel of moist sand..."



ZANITE puzzle solved. Time to hit the dunes...