Epoxy-Granite machine bases (was Polymer concrete frame?)

[DaBit]

Not yet.. I will leave the entire thing in the mold for a week or so at room temperature. By then, most of the curing process is complete, but the epoxy has not yet reached it's maximum strength (and stiffness, I presume). It needs a post-cure for that.
Before post-curing I will remove the MDF mold; getting the core of such a massive block up to 70C will be hard enough already without 30mm MDF blocking heat ingress.

Anyway: I flipped the mold today so I could fill a few 2-3mm wide slits which I could not fill from the top side. Everything is looking good so far; no bubbles or pin pricks in the surface layer. There were a few wrinkles from the PE foil underneath it which I also filled with an epoxy+hollow glass bubbles mix. When cured I can sand that to a smooth finish. Apply a layer of 2K polyurethane paint, and it should even look decent.
The back side is plain ugly. I already expected that since I made a stupid mistake while applying the last layer during the filling of the mold. I think I will add a layer of epoxy/glassbubbles on that side too.

[Steven.ji]

during the casting the epoxy heats as it cures. this makes the steel expand, but the granite (quartz) does not expand very much. the

ive been wanting to try an EG structure but this exact problem has me thinking that i shouldn't try to embed steel parts into it. schneeberger uses a separately cast aluminium oxide mix for linear rail beds which is what i think i will try.

How Schneeberger use a separetely cast aluminium oxide?

Can you advice me the detail?

[Steven.ji]

Another thing we have used in reducing(not stopping) shrinkage in epoxy. PUR, and polyester castings is temperature control of casting materials and the reinforcing. The term "exotherming" is generally applied to this heat creation caused by chemical reaction. This is necessary to attain structural strength and integrity of your finished component. If you need further advice regarding reduction of shrinkage, I could suggest you contact the technical departments of either Sika Group | Sika AG , Dow Chemical Corporate Website - The Dow Chemical Company , or any other top line epoxy manufacturer. The are generally very helpful. I have been involved with mold making in epoxy, polurethane and polyester and other materials for over 25 years and have always referred any queries to the relevant chemists in involed and have saved a lot of money and time by not trying to hack it on my own.

When I have spare cash and time I love experimenting!

you are correct.

For epoxy granite, in general, we select low heat, low low viscosity, low expansion resin and hardener.

Many plants can do it via your inquiry.

[ihavenofish]

How Schneeberger use a separetely cast aluminium oxide?

Can you advice me the detail?

its on their website somewhere. basically it seems that they "paint" certain parts of the mould with aluminium oxide mix to get a hard surface, then fill the rest with quartz mix.

[DaBit]

If I reduce shrinkage, I still have shrinkage. That assembly with the steel strips went ca. 0,3mm out of planar. Not that much for a 770mm long part, but too much.
With low shrinkage that would maybe be 0,1mm, still too much.

The next time I will just cast in anchors and a void where the precision part should be. Then mount precision parts and fill the small space (2-3mm is sufficient) between the main structure and precision parts later. Absolute shrinkage would not matter that much as long as it is not too excessive.

I think I will pull the mold this weekend, do some fixups if required, and put in through post cure.
I have been patient long enough. But a very busy week at work helped with that a lot

[DaBit]

I have the flu so I didn't do much. Pulled from the mold, a little sanding on the very sharp edges only:



I have some cleaning-up to do; the 'gelcoat' was too thin in some spots and decided to stick to the mold. Bummer.

It is in postcure now.

[the4thseal]

This is fantastic. You can always reapply jell coat if needed.

[Low-Alloy]

I've tried to search just this thread, but can't figure out how. I am looking for mention of Huntsman epoxy. I know I've seen it mentioned somewhere in this thread. I think ckelloug mentioned it as it pertains to the epoxy that uscomposites.com sales. I do a a keyword search and it returns this thread; all 399 pages, not the specific post.

Any help out there?

Thanks

[rocketflier]

I've tried to search just this thread, but can't figure out how. I am looking for mention of Huntsman epoxy. I know I've seen it mentioned somewhere in this thread. I think ckelloug mentioned it as it pertains to the epoxy that uscomposites.com sales. I do a a keyword search and it returns this thread; all 399 pages, not the specific post.

Any help out there?

Thanks

At the top of the messages, NOT the top of the page, are these menu pull downs

LinkBack Thread Tools Search Thread Rate This Thread Display

Click 'Search Thread' then enter huntsman.

This was the first returned
http://www.cnczone.com/forums/epoxy_...tml#post512187

[edit]wasn't having much luck last night, but here's the rest...
<ctrl> f for find then searching on ckelloug takes you right to a pretty long post.

Now you might have noticed 'Advanced Search' when you selected Search Thread. Clicking that brings up more options and you could enter the username ckelloug and it would only return posts by that user. That's fine an dandy if you got the name right. And the right name. I find I do better by adding more search terms of what I remember so something like 'huntsman uscomposites'.

Odd I don't recall 'huntsman' epoxy having been mentioned. I've gone through the thread enough times.

Google search on "huntsman epoxy site:www.uscomposites.com" returned
Adhesives
and their mdsd (pdf warning)
http://www.uscomposites.com/pdf/adhe...astweldres.pdf

Google search on "huntsman epoxy site:www.cnczone.com"
Returned this post first and the following second
http://www.cnczone.com/forums/epoxy_...frame-106.html

[clmenz]

Fantastic instruction on how to subselectively search complicated long topics and threads. [particularly the 4k of posting on this thread]

Sent from my SAMSUNG-SM-N900A using Tapatalk

[rocketflier]

Fantastic instruction on how to subselectively search complicated long topics and threads. [particularly the 4k of posting on this thread]

Sent from my SAMSUNG-SM-N900A using Tapatalk

What is it you cannot find?

[Low-Alloy]

Thanks for the help with thread searching!

Low-Alloy

[Low-Alloy]

[QUOTE=Stonemason101;1411392]Hi D,
We use ribbon blenders for mixing. These are very high output machines,e.g. a mix of 350kgs will blend in between 60 and 90 seconds depending on type of mix. You might consider making a mini unit,i.e. 15-20 kgs, for small mixes. Believe me, it's well worth the effort. Here's a pic of my first build, a 400 kg unit in 304 stainless steel.Attachment 217464 (not me in pic, but my good man, Friday!)

Hello Stonemason101;

Can you show more pictures and a how-to discription of your Ribbon Blender? A "mini unit" (around 40- 50 kgs) sounds about for me.

Cheers!

Low-Alloy

[nateman_doo]

I have the flu so I didn't do much. Pulled from the mold, a little sanding on the very sharp edges only:



I have some cleaning-up to do; the 'gelcoat' was too thin in some spots and decided to stick to the mold. Bummer.


It is in postcure now.

wow... 400 pages?!

UPDATES on this build??

[DaBit]

A little:



I am spending at least 70% of my time with the dial indicator

[Steven.ji]

not only get a hard surface, but also high precsion surface.

[bhurts]

I am wondering about filling my large aluminum extrusion's. I am thinking about filling them more for damping and less so for structural rigidity. I don't want to spend a lot on epoxy for this. I'm thinking maybe I can use tightbond 3 wood glue as the binder and mix it with sand and gravel. Maybe even add some of the larger wood chips I get from the jointer as well. Is this a bad idea? Does anyone think it would work as a damping filler?

Thanks
Ben

Sent from my HTC6435LVW using Tapatalk

[DaBit]

I would use a 2-component resin as the binder. 1-component resins need something else to cure (moisture, evaporation of solvent, etc.), which probably isn't available inside an enclosed aluminium extrusion.

Regarding the cost of epoxy: if you can ram the mixture in, you don't need much epoxy. Most of the epoxy concrete of my gantry is 3% by weight.
I also don't see what benefits wood chips would provide. They would just suck up the resin, making them more expensive to use than sand and gravel.

Did you consider regular Portland-cement based concrete for your appplication? I expect that would work well too.

[wizard]

I am wondering about filling my large aluminum extrusion's. I am thinking about filling them more for damping and less so for structural rigidity.

It probably won't hurt but that depends somewhat on the machine. The thing to watch out for is making the gantry to heavy if this is a moving gantry system. Otherwise the filling does help damp the sYstem.

I don't want to spend a lot on epoxy for this.

That is understandable but it wouldn't be a lot of epoxy and it could be cheaper epoxy due to the fact that you aren't doing anything structural with it.

I'm thinking maybe I can use tightbond 3 wood glue as the binder and mix it with sand and gravel.

I'm glad I logged in because Dabit's post got me thinking a little harder here. I could see where there might be a issue getting Tightbond to setup. Essentially you are putting the glue into a bottle so I'm not sure what your results would be in the center of the tube. Frankly I've used a lot of Tightbond over the years but I'm not really sure what causes it to setup.

The urethane gluEs are interesting and here I know they need moisture to set up. However Urethane glues set up way to fast, you would never get the glue mixed with the aggregate before a big mess ensues.

About the only thing I can think of off the top of my head that might work well are the anaerobic glues like Loctite thread lockers and some of the other stuff they make. These setup in the absence of air and bond well to metals.

Maybe even add some of the larger wood chips I get from the jointer as well. Is this a bad idea?

I have to agree again that wood chips would not be ideal. Mainly for another reason and that is because they would reduce your fills density. The flip side is that the chips might actually help setup the glue.

Does anyone think it would work as a damping filler?

Epoxy granites are will proven in this scenario. Since I have no knowledge of anybody going this route I can't answer the question authoritatively. However if you found a way to get the glue to setup it might work OK. Personally I would go for a resin/glue/whatever that I had a high confidence that it would stick to steel and aluminum.

Thanks
Ben

Sent from my HTC6435LVW using Tapatalk

About the only thing I can suggest beyond the above is to get on the Loctite and other alternative glue manufactures sites and look for products that might fill this niche. Loctite literally has hundreds of formulations. However you may find that good ole a Epoxy isn't that expensive. By the way other glues include polyester and urethanes. An example of polyester would be body filler compounds. Unfortunately you may have to experiment a bit.

[ger21]

Titebond is far too thick. You'd never be able to mix it with sand. If you tried, it would start to get even thicker than when you started. Also, it doesn't stick to aluminum very well.

You can get 3 quarts of epoxy from US Composites for about $45. Mix it with a bag of sand, and your all set.