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darryl
11-05-2014, 12:45 AM
I got well over 100 pages into that thread before getting drawn away to other things. Today I looked through the last few pages- 404 I think was the last page. The last post was only a month ago- the thread is years long now. People are still testing their composites, making test blocks-

I'm wondering what some of the diehards may have produced, and if there are pics, maybe write-ups on any finished machines.

ckelloug
11-05-2014, 06:37 PM
I was one of the chief instigators on that thread. I did a lot of research and ended up starting a materials company based on what I learned although unfortunately, epoxy-granite for the DIY crowd doesn't look like it could be a profitable product for me. I made this sample of a Silicon Carbide based Epoxy Granite and provide the formula for a slightly better version of it.http://i161.photobucket.com/albums/t202/ckelloug/Egsamples.jpg

I just posted this at CNCZONE in response to darryl's question but I'll cross-post here too.

In general, an optimal recipe is based on characterizing exactly what you have and using as wide a range of sizes as your machine design will allow. In most cases, optimal isn't necessary. For filling bases etc. almost anything will work. For other things, a mix that goes from pea sized gravel #6 sieve to fine dust would probably be best.

My final recipe from the simulator was:
n6SiC.ag n16SiC.ag n36SiC.ag n70SiC.ag n180SiC.ag n320SiC.ag n600SiC.ag g200zeospheres-high.ag
0.242780, 0.168667, 0.112555, 0.100630, 0.110247, 0.087316, 0.022684, 0.155121,
Predicted packing density was 0.876454

Where the above are callouts for silicon carbide abrasive and 3m Zeeosphers and below are the volume percentages which are measured
by computing specific weight using the density and adding the appropriate weights of the components.

The Epoxy Used was a low viscosity epoxy: Hexion 813 and the hardener used was isophorone diamine.

For a 38gm batch of epoxy
30.3g Hexion 813
6.9g IPDA
1.0g BYK A525

Add 25.6g G200 to vessel and mix for 4 min.
Add 37.9g #600 SiC to vessel and mix 2 min
Add 44.9 #320 SiC to vessel and mix 2 min
Add 60g #70 SiC to vessel and mix 2 min
Add 62.5g #36 SiC to vessel and mix for 2min
Add 94.1g #16 SiC to vessel and mix for 2min
Add 143.6g #6 SiC to vessel and mix for 2min

Turn out into mold and vibrate.

This will be very stiff and may be easier to deal with given a little bit more epoxy.

Hope this helps.

Regards,

Cameron

darryl
11-05-2014, 07:43 PM
Thanks, Cameron. I'll take that as the final recipe for a pretty much optimum product that can be done in the home shop.

Still wondering if anybody has a completed machine to show-

ckelloug
11-05-2014, 10:31 PM
I realized that I couldn't afford to make the precision molds to make a machine the way I wanted to do it. Some ingenuity and some linear rails however would allow a less precisely
molded machine to be adjusted until everything was in very good alignment. I saw a thread somewhere about somebody making a cast epoxy-granite piece possibly for a Quorn tool
and cutter grinder and it looked impressive. I think the thread was at practical machinist but not sure.

Paul Alciatore
11-06-2014, 03:21 AM
I guess I missed something. Exactly where is that discussion?

darryl
11-06-2014, 03:25 AM
cnczone epoxy granite machine bases.

rowbare
11-06-2014, 08:39 AM
I realized that I couldn't afford to make the precision molds to make a machine the way I wanted to do it. Some ingenuity and some linear rails however would allow a less precisely
molded machine to be adjusted until everything was in very good alignment. I saw a thread somewhere about somebody making a cast epoxy-granite piece possibly for a Quorn tool
and cutter grinder and it looked impressive. I think the thread was at practical machinist but not sure.

I think that was John McNamara's Worden http://www.model-engineer.co.uk/forums/postings.asp?th=51617&p=5

He had posted the link in the CNCZone thread: http://www.cnczone.com/forums/epoxy-granite/30155-epoxy-granite-machine-bases-polymer-concrete-frame-post955930.html#post955930

bob