[roach]

sorr i missed chopped strands

[ckelloug]

roach,

We've been working on a formula using aggregate from #4 down to micron sizes obtained with 3M zeeospheres. The resin most of us have used in our experiments is reichhold 37-127 and hardener 37-606. This is a low viscosity resin with reactive dilutants with a 1 hour slow hardener. I've got some in stock for tests but I haven't started my testing plan.

Jack likes chopped strands but I think they increase vibration transmission.

--Cameron

[jhudler]

no can u clalify settleying?

I would describe settling, as an increase in aggregate density near the bottom due to vibration compaction. This leaves more epoxy at the top of the mold.

Segregation (or stratification) is where aggregate of same size form a layer. Each layer usually has a larger size as you progress toward the bottom. Though I seriously doubt you'd see this.

do u compact at 1mm or 2mm?

I don't know what you're asking here.

Thanks

[roach]

ah understand ya now
you should always get resin on the fill side but should be no seperation
imagine the resin is a lube for the granite so it compacts down easy
yes your right chopped strands do keep the resin in the matrix cause there hollow
we dont use them but u want dampening which the resin would help being plastic
but it horses for coarses with granite
some want stiffness or dmpening or both so you adat the process to meet

[roach]

our potlife is 3hours depending on the temp

[jhudler]

Jack likes chopped strands but I think they increase vibration transmission.

oy! I haven't even poured that yet. But seriously I would only use it where I need additional tensile strength. Such as a single vertical column mill... though I doubt I would ever build such a thing. I like slant bed designs too much!

[ckelloug]

I think silica powder as meant in what roach said is actually very fine grain silicon dioxide aka quartz powder. Silicon is often a misnomer unless it's spoken by a chemist. Silicon, silicone and silica are all often called silicon even though they are very different things.

See http://www.tradeget.com/free_list/p3...nd_powder.html for an example.


I can't find any references to using elemental silicon in epoxy and it doesn't make sense. It would have similar chemistry to adding carbon so I surmise that if it is in small enough particles, it will behave a lot like carbon black and be much more expensive.

Regards all,

Cameron

[roach]

remember all your doing is binding stone in a resin it bends if enough pressure applied
each partivle pushes the next so any weakness gives some companys use calcium carbonate
whats the reslts then mathman
im generally drunk and playing cod4

[roach]

mix carbon black in resin and silica see which breaks easiest

[jhudler]

Good point. If I recall, carbon blacks tensile numbers 10 times less than silica fume. But I can't find the reference for silica fume properties.

[sigma relief]

do you need the resin ratio aswel?

<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>
<o></o>
OK, I'll bite, what is your target resin ratio?<o></o>
<o></o>
While I'm at it, I may as well list some of my other questions. These have been on my mind for months, you may have some insight. Some of them may be irrelevant or just plain dumb, but if you have any ideas or opinions, I'd love to know.<o></o>
<o></o>
How accurate is the aggregate mix ratio controlled? the aggregate to resin ratio?<o></o>
<o></o>
For your 6mm, 10mm, and 14mm percentage values, I am assuming 14mm size is actually 10-14mm, the 10mm is 6-10mm, etc.<o></o>
<o></o>
What is the aspect ratio of the aggregate? Are the large pieces mostly "roundish" or are they elongated chips? How rough are they?<o></o>
<o></o>
Do you use different formulations for large or small molds? What about to optimize for strength, stiffness, or vibration reduction?<o></o>
<o></o>
What is the smallest feature size and wall thickness in mass production parts? What about delicate specialty parts?<o></o>
<o></o>
How well is the aggregate cleaned? is there dust on the large or small aggregate?<o></o>
<o></o>
How do you finish the top of the pour once cured? Is it flat and level enough to leave as is or do you grind and round the edges?<o></o>
<o></o>
What kind of granite is used for the large particle sizes? Is it large or small grain? Is it just locally available scrap pieces ground to size or purpose mined with specific attributes in mind?<o></o>
<o></o>
You speak of compacting at 1mm or 2mm. Does this refer to pressure in a vacuum bag or equivalent force from a compaction ram?<o></o>
<o></o>
For chopped fiber, are you referring to "short" 1/2 inch (12mm) chopped e-glass (or s-glass) common in the plastics industry, a longer 1-3 inch chopped glass often used in spray on applications, or something much much longer? How is the resin ratio and aggregate mix adjusted to ensure proper wetting? Is the glass for strength, stiffness, vibration damping?

[sigma relief]

hmm, not sure where all the >> came from. I guess every forum interprets quotes and pastes from word differently.

[roach]

im a shy person till im drunk then ill spam you to death
ok sigma
ill start
ideally 7%
yes too wet seperates too dry wont compact down
sieve size it passes thru
should be roundsish too much elongated wont compact
yes and yes not reduce but up
ive done 19mm tile wall depends on the application
washed dust no
depends on appgranite or basalt anything with a high crush value some companys use gravel which is round but that aint granite to me epoxy concrete
thats compacts from the vib moters and the frequency and resonance needed
as for vacuum sucking air out not many apps need it our moters con do 2 - 3 ton each just add them as need
all three too much drys it out depends on the job
anymore?
i know what the density is but what u work it out to
are you lot looking for a supplier to buy from cause my boss will sell it lol in the raw state

[roach]

oi where r u all

[ckelloug]

Hey Roach,

Cool post. I'll run your numbers through the density model and get a feel for what I predict the density as. Can't make a really good prediction without samples of the component materials to measure their Beta parameters.

I think that some of our participants in the UK would be happy to know that your boss would like to sell materials. Not everybody wants to move heaven and earth to get the materials though I don't mind. . . Rocks are a bit heavy to ship to this side of the pond though.

I don't know about the rest of the crew but I've been busy with work and contractors repairing a leak in my roof so I haven't gotten a lot done lately on E/G.

Regards all,

Cameron

[amen23]

I started reading this thread and halfway through started asking myself..........Why is everyone striving for such precision ? If you were in production of vital components for say a space shuttle i could understand it. What are all of us really using it for and is the added expence feasible for engraving your wifes name out on a $4 piece of MDF?

[greybeard]

I started reading this thread and halfway through started asking myself..........Why is everyone striving for such precision ? If you were in production of vital components for say a space shuttle i could understand it. What are all of us really using it for and is the added expense feasible for engraving your wifes name out on a $4 piece of MDF?

It's probably a good idea that we should have a brief recap every so often on this thread, just to remind ourselves where it's going, as well as for the benefit of newcomers.

Walter started by asking if anyone had cast a machine base in E/G as more and more professionals were using it in various ways. It became obvious that while it was a straightforward matter(I wont say simple) for people to take concrete as an analogy, and just mix stones/sand with epoxy, and you get a synthetic version with good vibration damping properties.
However, like all plastics, epoxy suffers in two ways - flexibility and creep under load - so could the recipe be improved to bring those to a minimum.

Bringing in some recent work(1998ish) described the way concrete research was vastly improving its properties, so it seemed very reasonable to assume the same could be done for E/G.

Yes, any materials can be used to build your machine. You just choose them on the basis of how much precision/repeatability you need, and build accordingly.
So any mix of E/G will get you into casting a machine base, but some mixes will be better than others.
The basic recipe has been posted several times, but the thread has evolved to discover just how good can it become.

In the much quoted French work, De Larrand pointed out that the professional industry would always be constrained by time/labour economics, and that the direction his research was pointing with multiple components would be ruled out for most uses. For us in the diy field, that doesn't apply in the same way.

While having my own ideas, I hope to keep following the maths/engineers in case I can spot something that applies to what I'm doing, and taking any oportuinty I get to throw spanners in the works, or cats among the pigeons

Regards
John

[ad_bfl]

In my case, I will not be milling sheet goods, unless you call chunks of 6061 aluminum that are measured in feet a "sheet good"

Hence my interest in optimizing this stuff.

One use that has came to my mind lately is using EG as a interface material for vibration control of the spindle if the Gantry is made of steel or Aluminum.

Picture the mounting block holding the router to the z axis (Porter cable 3hp, .002 runout, lots of vibration) mounted by a EG block, meaning no, metal to metal contact to conduct vibration waves.

This would isolate the router from the gantry frame, and hence isolate the frequencies generated by the router.

It would be interesting to see how this would affect surface finish, especially while climb cutting.

Or imagine using EG in a simliar manner where the motion axes connect.

Could do the same for the ballnut, etc...

Al

I started reading this thread and halfway through started asking myself..........Why is everyone striving for such precision ? If you were in production of vital components for say a space shuttle i could understand it. What are all of us really using it for and is the added expence feasible for engraving your wifes name out on a $4 piece of MDF?

[Zumba]

Hey folks,

Been away from this thread for awhile. Was thrilled to see Roach join the discussion, posting info on Granitan. Is this the same Granitan used in Studer cylindrical grinding machines? Roach, do you have any numbers for the final product, e.g. density, yield strength, modulus of elasticity, etc?

For those who aren't familiar with Studer, these are high end German grinding machines with the "economical" S-33 model priced at $320k well equipped...

http://www.adgrind.com/Studer/Granitan/Granitan.htm

[Zumba]

While on the topic of big names and composites, here are Hardinge's "Harcrete" claims:

Patented HARCRETE&#174; Polymer Composite Base

CONQUEST lathes incorporate a HARCRETE polymer composite base. Pound for pound (kg for kg), the strength-to-weight ratio is far superior to that of cast iron:

* 10&#37; stiffer and more rigid for improved dynamic stability and reliability
* 1/3 less vibration at the spindle
* 30% or more increase in tool life
* 37% improved surface finishes
* Longer machine life
* Heavier/deeper cuts
* Faster machining speeds

HARCRETE base found on most Hardinge CONQUEST turning machines
30% increase in tool life adds up!
Save thousands of dollars annually in perishable tooling alone!

HARCRETE&#174;-Reinforced base offers dynamic stiffness far superior to base made solely of cast iron-reinforced bases found on the QUEST™ and CONQUEST&#174; TwinTurn&#174; 65 lathes.

This is interesting, since they're basically pouring E/G into an iron casting. Apparently it works quite well.

Does anyone know the actual linear coefficient of thermal expansion for E/G? Epoxy by itself has a coefficient 3 times greater than that of steel/iron, whereas that of quartz by itself is only 1/10. Typical building concrete has a nearly identical coefficient.