[atenman1]

Hi Larry
Thank you for answer me!!!
If you look at http://www.microplan-group.com/pagin.../celith_gb.htm
or one picture i extracted from they website

-It seem liked they used MDF for they one off moulding. My question to you is how do they apply vibration? Because any vibration at all would shake loose that thing?

-If we use MDF for mouding, then could we use this
http://www.harborfreight.com/cpi/cta...emnumber=42947
instead of vibrating table?

as always thanks. BTW keep this thread alive:cheers: (nuts)
calvin.

[lgalla]

Is this off topic?Real black granite surface plate.
12'X18"X3" $19.50 US
24"X36"X4" $100.00 US
48"X96"X8" $2370.00 US
From E-bay store Discount machine shop.Hum,the epoxy guy thinking about real granite?Naw the 48X96 wouldn't fit on my drillpress.
With prices like this on the smaller stuff this is looking good if you can drill it accurately.Steve gave a link to diamond drills.Lets see,no worries of aggregate size,only one large aggregate,no epoxy,no air entrapment,no vibration,no mold etc.Hum,wonder if they have a 6'X12'X12".
Good links Calvin.I will answer to nite.Late for work.
Larry

[greybeard]

Larry - is this thought train taking you round to my idea of using plain bricks and epoxying them together ?
The key idea behind my suggestion is that the brick(why not choose an "engineering" brick - high temp fired) having aged, it is now stable, cheap, and comes in a suitable modular size to create a variety of shapes.
It also crucially cuts down the amount of epoxy required, avoids cavities, no need for vibrating tables.
You can pre-drill holes for inserts that can be potted in place afterwards, and by jigging in whatever accuracy you need.
You could also drill through to add reinforcing rods under tension if that was appropriate.
Larger table areas could be built by laminating paving slabs, again with epoxy.
You could even build a torsion box on the same principle !

Regards
John

[lgalla]

Calvin good research.I like the concretre vibrator.The picture is a melomine mold,which I had previously said may be used for one offs.You must be spending much time researching.Thanks.
I wish I was building a mill or smaller machine as the granite surface plates are an exciting possibilty.On larger machines I like walters filled channels.
I like 80/20
I like stealing padio stones or Greybeards ideas of large solid fillers encapsulated in E/G.
Although I have vacuum de gassing equipment I would not use it as my pours would be so large,de gassing would be impratical.
Conclusions.
If you can use a surface plate,go 4 it.
Use E/G as a filler of tubes or weldments.
Fabricate a structure which is selfsupporting and add E/G as a damper.
In a medium to large sized machine calculate the weight factor.How are you going to move it if necessary?
I have no problem with 8000lbs as I have a forklift.
Walters design would give benefits of E/G and surface plate with lighter weight and lower cost on medium to large machines.
Larry

[lgalla]

I did it again.:withstupi
I was finnishing a post to Bruno,went back to review and lost everything I posted.This happens all the time.I hope you guys have patience with me as it is hard for an old dog to learn new tricks.I ask why is a computer dummy building a machine?I hope you guys can help me later with programing and CAD CAm etc.Presently I am working under HAD,Holstien aided design.:cheers: :cheers:
Bruno I will try to answer from memory rather than risking going back.
Sandblast sand seems a starting point as it is high SiO2 and dry.1/4"to3/8" aggregates seems to be a good choice for the larger rocks.A low% of 1/32 milled glassfiber would create a micro re inforcement between thr aggregates.
Good point on microspheres.Microspheres act as micro ballbearings allowing less resistance to flow and aiding in air release.There is a microsphere from 3M called zeospheres, a ceramic microsphere.It is hollow but has a compressive strength of 50,000psi.I beleive I have used grade 850 which is the least expencive,about a buck a pound.
Larry

[JerryFlyGuy]

Hey Larry, totally off topic but if you wish to go back and look at old posts will writing a new one, just scroll down the page. The last 15 posts are listed down below where your typing in your post [this is, if you don't use the 'quick post' function]. If the post is farther back than just 15, at the VERY bottom of the page is a note that says

This thread has more than 15 replies. Click here to review the whole thread.
if you right click the 'here' you can open the whole thread in a new window and then cycle through it all, this should elliminate the hassel of losing all you've written!

Jerry

[vger]

Reading the last few posts made all the wheels start turning again... uu oh..
greybeard mentioned torsion box, and I pictured cutting up slabs of granite into long strips and epoxying them together. Then pictured cutting those strips into smaller segments and making a honeycomb structure sandwitched between two thin (2 or 3 CM) slabs. Maybe I better stop here and do some more thinking...
Steve

[greybeard]

Foamed granite ? (chair) (chair) (chair)

[lgalla]

Steve Vger glad to see there is other people out there that are possibly mad.I have dealt with honeycomb structures in the past and they are generally considered light weight.I have considered a light weight core of MDF with E/G skins,which would be stiffer,lighter,cheaper than solid E/G.DON'T stop the wheels turning,stopping and thinking just hurts the brain.
Other people out there are mad also.Look at Greybeard he is foaming at the mouth as we are.(chair) (chair) (chair) I hope he means a foam core.
Most of my posts have been(flame2) (flame2) :cheers: :cheers: (chair) :drowning:
The opinions expressed here are not the opinions expressed by the Zone but entirelly my own.:cheers: :cheers: Larry

[the4thseal]

Does anyone think that post tensioning the EG structure will be of any use? I am making a mold right now and wondering if i should make changes to accomodate tensioning?

[Geof]

Does anyone think that post tensioning the EG structure will be of any use? I am making a mold right now and wondering if i should make changes to accomodate tensioning?

I think this might be a negative move. Part of the benefit of the EG is vibration dampening and if you tensioned the structure you might even make it ring more.

[atenman1]

:wave: Hi Matt

Time up! where are those tutorial ? just kidding!
just a reminder to make sure that you did not forget us...

BTW, do you have any pics of the moulding that you used for the mill that you shown to us? Can we see them?:cheers: :cheers:
Thanks
Calvin

[vger]

Some years back I witnessed the demold of a stressed concrete bridge beam at a plant where I was doing a balance job. When they released the tension on the rebar the whole multi-ton conctete beam arched it's back up by about 6" in the middle. It was rather amazing to see that the "solid" concrete would bend like that. They intentionally stressed it to do that so that when in place under the weight of the bridge deck it would be relatively flat. I would tend to think that stressing E/G would not be the thing to do.

[vger]

Steve Vger glad to see there is other people out there that are possibly mad.I have dealt with honeycomb structures in the past and they are generally considered light weight.I have considered a light weight core of MDF with E/G skins,which would be stiffer,lighter,cheaper than solid E/G.DON'T stop the wheels turning,stopping and thinking just hurts the brain.
Larry

Larry,
On the honeycomb idea.... suppose instead of building the honeycomb, you just mold it that way. There is a 2 part polyurethane foam product that one could use to make hexagonal posts. Set these posts into your mold with seperation between them and a couple of inches of clear area left at the top, then pour your E/G in and... A similar process to this is done with glass (molten) for really big telescope mirrors. Take a look...
http://baryon.as.arizona.edu/TECH.php?navi=gload
What do you think?
Steve

[lgalla]

Steve good ideas.I am guilty of this too,but we should try to go a simple route.Good link.Notice the sand comes from Florida for the glass.I guess the guys in Florida just have to go to the beach for their filler.
Larry

[Geof]

...When they released the tension on the rebar the whole multi-ton conctete beam arched it's back up by about 6" in the middle. It was rather amazing to see that the "solid" concrete would bend like that...

This shows one reason why cement concrete is not suitable for machine bases. "Solid" concrete is not solid it is full of very tiny gaps as a result of the curing process; these gaps are closed up under the tension in the rebar. The beam arches because the bar runs below the centerline so the gaps in the lower portion get closed up more than in the upper.

Polymer concrete, provided you have the correct aggregate mix and have mixed and vibrated things correctly does not have gaps.

[the4thseal]

Thanks, i had thought that tensioning might be trouble but i thought i would send the idea up for other opinions. Since i know what i think it is good to hear the ideas of others. I am almost done with the mold and getting the aggregate and other stuff. We shall see if i am just making a really solid door stop or smething that is o some use.

[Geof]

Foamed granite ? (chair) (chair) (chair)

He is not completely off his rocker . Granite is an igneous rock, therefore it is of volcanic origin, volcanic ash is more or less (if you stretch a point) foamed granite.

On the topic of vibration for the mold. If you have a compressor you could maybe get a cheap pneumatic chisel and adapt a rubber hammer head onto it. Hold the rubber against the mold and pull the trigger. Alternatively put a kind of paddle on it to directly vibrate the EG.

[greybeard]

Thanks Geof. I wasn't going to spell it out as it only ocurred to me after I'd posted it, but pumice is foamed igneous rock. Not sure of its stiffness though.

Can you imagine some 19th century lab tech suggesting to Young that they try bending a piece of lava..


Unfortunately I can only think of those mouse sized lumps they sell for rubbing off the hard skin under your feet.
But now I think of it, you could make quite a good packing ratio by inverting alternate ones......

Pumice mice, not feet.

John

[skippy]

To my way of thinking, trying to make a sandwich panel (or torsion box) of foam and granite or any stone for that matter, will not work because stone is fine for the side under compression (top) but not for the side under tension (bottom).