[RotarySMP]

My local library has a german book on this construction. The jems of knowledge I took away was that you don't want just sand as a aggregate, you want a mix of aggregate sizes up to about 1/5 the thickness of the thinest feature, and that the epoxy content is quite low, far less than 50% (I think something like 15-20% from memory). At 50% you are using epoxy as the load bearing structure, which means you basically have a plastic machine frame.

The aim is that the aggreate is the load bearing structure, and the epoxy just locks the aggregate into a fixed alignment.

You do not need to pour the whole structure in one go, so for hobby work, I could imagine that a hybrid structure built up of polymer concrete features poured onto a cheap chinese granite surface plate or two would have a lot of potential.

[Episs]

How about other materials for example I just found in my local distributos homepage sutch SicaDur 42 (Rapid High Strength Pourable Epoxy Grout) www.sika.com
in datasheet USES section was:
Grouting of bearing plates, machine bases,
mechanical bridge joints, bridge bearings and rail
base plates (I like this one becose I have THK reils which need base ).

Flexural strength: 30 N/mm2 @ 20°C
Tensile strength: 20 N/mm2 @ 20°C
Modulus of 18 KN/mm2 @ 20°C
Elasticity: (static)
Density: 2.0 kg/litre

There was nothing mentioned about wibration damping characteristics .

This is wery intresting material SikaRail® KC330/340 Polyurethane Flexible Resin Based Grout

USES
SikaRail KC330/340 provides a flowing, vibration absorbing load bearing resilient grout for:
* Bedding and bonding rail base plates to:
steel bridge decks, concrete bridge and tunnel slab
tracks, concrete sleepers

ADVANTAGES
* Out performs cementitious, epoxy and polyester
grouts under dynamic loading.
* Excellent noise and vibration damping.

maby this is the right material to tray out ?
and in datasheet is also sayed that Additional detailed information such as load/deflection graphs, spring coefficients, resonance frequency, damping factor etc are available on request.

I start to think Do i realy need this 10x vibration damping (over cast Iron)?
I think that the main benefit of these special compozit concretes are that i can make any solid shape myself for mutch lower price

[victorf]

Consider a slab of granite. Find a custom countertop builder and check out their inventory. I live in a small town in upstate New York and there are at least two locations that have ample supplies of granite in various thicknesses and color. A bit pricy, but they will cut it to any size on their CNC machine. I have seen slabs up to 10' x 6' and 2" in thickness. This stuff comes in a uniformly polished condition. Check it out!

Just my two cents!

Vic

[walter]

Consider a slab of granite. Find a custom countertop builder and check out their inventory. I live in a small town in upstate New York and there are at least two locations that have ample supplies of granite in various thicknesses and color.

Thanks. This sounds great, but we are looking for cheaper and easily workable materials.

At $0.80 per lb, Epoxy/Quartz is hard to beat. Castable to any shape.

We are far away from granite-like performance, and it'll take a while but that's where we're headed.

In a year or two we should be able to build this frame:



We are going to cheat and use massive steel reinforcements, but this is the look and performance we're after.


Larry,
I don't recall the percentages on the latest samples, but they were mighty tasty.
Now wait till I get my shaker going...

[HBFixedGear]

Beware air of air pockets. This site deals in normal precast concrete but one would assume the machanics would be very similar.

http://www.precast.org/publications/...nVibration.htm


There are a raft of companies making concrete vibrators for air removal DeWalt and makita even make hand held versions.

B

[garfieldsimons]

Just bought a used 6" x3 x 4 foot granite surface plate ($50) and could of had 3 more. The second hand market for surface plates is apparently not so good. (Who wants to move 1500 lbs of stone.) I would use these instead of going to the expense of epoxy for any thing big. (Of course I am also a cheap SOB)
Richard

[VoxLimbo]

Just bought a used 6" x3 x 4 foot granite surface plate ($50) and could of had 3 more. The second hand market for surface plates is apparently not so good. (Who wants to move 1500 lbs of stone.) I would use these instead of going to the expense of epoxy for any thing big. (Of course I am also a cheap SOB)
Richard

This raises the question of: How can we dispose of an obsolete polymer concrete system? What is required to break it into small enough pieces to remove from your basement?

Albion.

[uhrgerat]

Hi,
I've looked at concrete as a building material a couple of times. A couple of things that might be of interest are the lecture notes from Alexander Slocum at MIT and one of his students Eberhard Bamberg, now at Utah (?).

One of the things that Slocum found was that standard concrete, i.e., portland cement and sand, works quite as well as epoxy-aggregrate concretes. And, is definitely much cheaper. There's also an article on the web--I'm trying to relocate the reference--regarding "alternate materials for machine tool beds". Basically the authors found the same thing, portland cement and sand works better in many ways than epoxy.

Another of Slocum's contributions was the ShearTube. In order to build a gantry type grinder frame for one company, he designed the tube which consists of a inner and outer tubes of steel. Cast between the tubes is standard cement with the inclusion of a vibration dampening material--appears to be very much like closed-cell foam that's used for mats. The foam is inserted so that it radiates outward from the center. He used 4 pieces of the foam. The design is now patented--you can find particulars by going to the USPTO site and, under advanced search, searching for Slocum as the name of the inventor.

Regards
Jim

[Joe Crumley]

A year ago I was doing the searches as previously mentionedand with frustration. It was a slogggg. Fortunately I've settled that down and will be glad to share my findings and experience. We are now in production and glad to share info..

We've been in the sign business for twenty years. Our product has been 3D wood signs from cedar and redwood. It became necessary to branch out with the lack of redwood available. With the addition of a CNC I saw the possability of topcoating our signs with acrylic stucco, sometimes called polymere concrete. This is a concrete look and will last a long time. I'll try to post a photo of one of our projects.

There are many different concrete formula's available. I've found Fossil Creeks "Vertabond" what we needed. The base for all of these is concrete. This is laced with nylor fibers, for added stregnth, along with a host of other compounds. The essential one being a an acrylic polymere which makes it stick to just about anything. I believe this stuff will even stick to glass.

Many contemporary structures, such as TacoBell's are stucco laid over a lath then the concrete is applied. The first coat is called the Brown Coat" Once dry the final coat is either trowelled or sprayed on. The product name for them is Drivit. Forget it, they only sell to approved installers.

Our process, simular ot Drivit, is to apply the liquid polymere, with a roller, to the structrue. This stuff looks like milk. Let it set up, we either trowell or spray the vertical concrete. This is a very forgiving process. It's not very hard on hands or equipment either. Also the surface can be sanded for several hours after application to correct flaws or give as smoother affect. You can build this up to any thickness desired. It takes several days to reach a good hardness.

We hoppergun on about 1/2" and let it set. When allmost dry we sand to a nice texture. Then coat with latex paint. Yes you can mix in color, but I've found it expensive and not very precise. Besides, if we chip a piece during installation, paint is the easiest to repair.

So in conclusion: You need the Polymere and concrete mix. The 40lb bags cost about 25 bucks but the polymere, from my supply, in five gallons, is about $155. That's diluted 4 to 1. Goes a long way.

My supply is www.thestampstore.com Look under vertical concrete mix.
Also there is www.demandproducts.com I think they are cheaper.


Joe
www.normansignco.com

[icando48]

Hey guys.. didnt think I had any thing to add but maybe..

as a sculptor I use resin and .... marble dust... to make sculptures, and also the back up for molds. I have never tried to make a self leveling bed for something but if you use the marble dust $6.-$7. a bag........at your local place that makes counter tops.. and the resin is a bit expensive.. $99. a gal I use the polytec resin #2 or #3 .. (harden in 3-5 min)

when pouring I eyeball it and use the marble dust as filler.......they say 10%.. but I use a lot more than that I also use microbloons a very fine filler .. so it doesnt get too heavy. I use the uneven ones..they are a lot cheeper.. bout a bunch years ago and havent even dented the bag. . any way you can add enough filler to the resin so you can mold it by hand. like play dough.

Must use precautions as always masks and gloves when handeling.

If any one is interested in more information and specifics they can get back to me.

thanks for all of the information you all are willing to share.. I just sit back and read and enjoy.. hope this helps some one.

I.Can.Do makes resin copys for artists and has a spin casting foundry that makes jewelry from pewter. and other things.

[ckelloug]

RotarySMP,

Your observations are good but I think they are lacking in scale. One of the reasons that a lot of optimization is going on on this thread is that the materials produced thus far (I'm not as familiar with Zumba's tests as Walter's) are not strong enough to hold even their own weight in many cases if used in a serious machine part. The problem is that to get deflections in the ten thousandths of an inch, with the low moduli involved, pieces reach the point where their weights grow faster than their strengths. These pieces could be augmented a great deal if they were supported with metal but metal has a higher Q value than Epoxy Granite and some here would like to see it possible to make a machine without having to cut any large pieces of metal. The strongest E/G possible will probably have a lower material cost than weaker stuff with too much epoxy and be only marginally harder to process so why not engineer a good mixture?

The second problem being dealt with is the fact that intuitive mixing and construction techniques handle the drier mixes rather ineffectively resulting in materials that don't perform nearly as well as something like the rule of mixtures would portend.

Finally, we have the result from Gupta that a 30-36 um shell of epoxy around each piece of aggregate according to Gamski's model is optimal in terms of maximum strength. Generally speaking, the mixtures should both have more tensile and compressive strength until the the epoxy amount reaches the 30 um level where strength begins to fall off.

I think all of your observations are good points qualitatively however it seems to me that quantitatively, production problems with the E/G material rather than mis-guided optimization are leading to a lot of experimentation for a mixture that overcomes the problems.

Thanks for posting your thoughts on this. I remember that you have made many good contributions to this thread over time.

--Cameron

[ckelloug]

Eson,

That is an excellent idea. It slightly complicates modeling the structure but it does give you much higher tensile strength on the bottom which is a key problem with E/G. If our epoxy bonds better to the glass or carbon than it does to the granite, this would work quite well. I'd want to check and see if it increases costs too. I am luck on this in the respect that Toray Carbon Fiber's factory is about 30 minutes from my house. I was thinking of using 1 inch randomly oriented carbon fiber strands for the bottom of my castings.

icando48,

Are you talking about acrylic resins or epoxy resins?


Thanks for Posting,

--Cameron

[chineguy]

Hello:
I don't want to give away any of Hardinge's secrets. BUT, They list a multiple component mixture of various size and weight filler stones in their machine parts manuals. The descriptions are probably useless to any one outside their shop. Harcrete is the name they use. I visited the plant and they do use metal structures as well as mounting pads molded into the Harcrete. I have thought that this would be a very good way to dampen and reinforce otherwise cheap machine tool castings. A rule of thumb that I remember was that thickness had to be nearly doubled to get the same stiffness when using a polymer concrete base structure. The damping was a huge benefit though. Many of the light weight benchtop style machines have hollow empty castings. It seems that this would be a way to improve them. Particularly if mounted to a very solid filled base, in addition to reinforcement of the castings. You guys have done some excelent work! Very Impressive.

[robpiaz]

I know a company that puts a dunham headstock on a surface plate. Then mounts linear bearings on it to make a gang tool machine. It designed to make small precision parts. This could be another alternative. All you would have to do is find someone or a way to drill and tap your mount holes. I know this works quite well they've built a few of these machines.

[Peldor]

How about other materials for example I just found in my local distributos homepage sutch SicaDur 42 (Rapid High Strength Pourable Epoxy Grout) www.sika.com
in datasheet USES section was:
Grouting of bearing plates, machine bases,
mechanical bridge joints, bridge bearings and rail
base plates (I like this one becose I have THK reils which need base ).

Flexural strength: 30 N/mm2 @ 20°C
Tensile strength: 20 N/mm2 @ 20°C
Modulus of 18 KN/mm2 @ 20°C
Elasticity: (static)
Density: 2.0 kg/litre

There was nothing mentioned about wibration damping characteristics .

This is wery intresting material SikaRail® KC330/340 Polyurethane Flexible Resin Based Grout

USES
SikaRail KC330/340 provides a flowing, vibration absorbing load bearing resilient grout for:
* Bedding and bonding rail base plates to:
steel bridge decks, concrete bridge and tunnel slab
tracks, concrete sleepers

ADVANTAGES
* Out performs cementitious, epoxy and polyester
grouts under dynamic loading.
* Excellent noise and vibration damping.

maby this is the right material to tray out ?
and in datasheet is also sayed that Additional detailed information such as load/deflection graphs, spring coefficients, resonance frequency, damping factor etc are available on request.

I start to think Do i realy need this 10x vibration damping (over cast Iron)?
I think that the main benefit of these special compozit concretes are that i can make any solid shape myself for mutch lower price

I also found a self leveling epoxy that might work for this. We use it as engine bedding one crew boats and tugs...

http://www.philadelphiaresins.com/
look under "shipbuilding and repair coumpounds" its under the Chockfast Grey link.
By the way, Philadelphia resins also had a "Castable for High Precision Applications" the stuff is called "Zanite polymer compound". It looks like some really tough stuff. http://www.itwpolymercastings.com/index.html

Here is a promo video they have on YouTube: [ame="http://www.youtube.com/watch?v=_XXATSCAaCg"]YouTube - ITW Polymer Tech - Casting Division - Capabilities Video[/ame]

[morphious69]

there are just to many posts here to read them all *yet* so here goes

Has anyone concedered using a vibrational dampening system similiar to the sound dampening that is used at airports? I am guessing it would require some sort of micro sensor array to capture the direction of vibrations and then an amp system that would create pulses to give "push" in the opposite direction. any ideas?

ps. if this has already been discussed then forget it and sorry about the double post of ideas

[Calthorp]

Hey you guys got me thinking!

How about using epoxy with aluminium or other metal powder as a cold castable that can be machined as a metal.
Wonder does it have some of the properties of the metal powder or would it be completly different

[probinson]

Sure, You can use any filler you like to create your own composite, it just won't behave like EG. One of the most important properties of EG is dimensional stability. If you substitute fillers that are resilient or have large thermal expansion characteristics you will lose that property but gain others.

Pete

[ckelloug]

Calthorp,

What you are suggesting has been done and is commercially available. PTM&W makes these here in the states. See http://www.ptm-w.com/index.asp?pgid=21

The machinability of these compounds is an advantage over E/G. One based on cast iron would probably be nice. One based on aluminum probably wouldn't be dimensionally stable enough to be that great for high precision tools. I haven't researched these metal epoxy compounds but I know that they are used in low-to medium production run die stamping where they are apparently a big cost savings.

Regards,

Cameron

[Calthorp]

Thanks guys,

They probably got it here in NZ but I am off to the hardware store to get some epoxy & have a play with different powders The local quary has plenty of crusher dust so can give graywacke-epoxy a go too (no granite close by) have a sculptor friend that uses granite but her dust would be probably 10% grinding wheel & too fine.

Cal