[harryn]

If the issue is flow to the bottom of the mold then why not start the pour there. What if you place multiple small tubes vertically into the form before adding the aggregate? Then inject the fluid into the bottom first and begin retracting the tubes as you fill. If this was done on a vibratory bench you might not even need to retract the tubes. When the fluid reaches the top of the mold then you know it is full. Even though you would need quite a bit of pressure to force the fluid into the mold, the mold its self would see very little.

I think you might be on to something here. While I believe that the EG / stone mix needs to be made up prior to the pour, you are right that if the problem is getting the pour to go into the "corners / bottom", then a good solution is to embed a "fill tube" which takes the mix right down to those areas.

Sometimes local "sprul vents" are used to help in this area as well.

I had not really thought about it, but one of T Edison's projects was to pour concrete into complex molds to make a "house in one pour of concrete". His group developed a number of useful mold / mix related improvements to make it all work. I think one of them was the addition of diatomaceous earth to keep the mix from settling out while it was flowing horizontally long distances. There must have been some vents in there as well.

[greybeard]

Sometime ago, in a posting a long way back, it was accepted that the mix might contain aggregate particles up to a maximum of 20% of the mold width.
If your fairly dry mix contains gravel 1/4" in diameter, and you want to push this down a tube within a 1.25" wide mold space, what might the dimensions of the tube be, if you need it to withstand any degree of pressure ?
I would suggest that the bore of the tube would add a fairly high degree of resistance to the flow of such a mix, and shoveling it in and vibrating it might be a lot simpler.

If you were considering a much more fluid mix, with a lower particle/mold size ratio, and needed to get into blind corners, then it might offer advantages.

John

[ckelloug]

Ladies and Gentlemen,

My Admet eXpert 501 flexural test machine has arrived.I now have full test capabilities though the machine isn't fully calibrated yet. (It's so new, I haven't read the directions yet). If anyone has any materials they wish to test, 5 samples 3/8 wide, 1/2 deep, 7.5 inches long are required. I once thought I might charge for testing but heck, I don't have anything to sell yet so until I do, I'll open my testing machine as a resource to our community. A can of Guiness in the box with the samples wouldn't hurt though

PM me for further info!!!!

--Cameron

[Peldor]

I think you might be on to something here. While I believe that the EG / stone mix needs to be made up prior to the pour, you are right that if the problem is getting the pour to go into the "corners / bottom", then a good solution is to embed a "fill tube" which takes the mix right down to those areas.

You could also do this and just cut out the middle man so to speak, make your mold, set your fill tubes (one in each corner and a few in the middle) and then put in your mixed aggregate. seal it all up and draw a vacuum on the whole thing. It wouldn't need to be a lot, just enough to draw the ER into the mold, that way you get even saturation from top to bottom with little to no bubbling. I think this would only work with the thinnest of ER's. Coming from a background in vacuum impregnation it seems like it would be easier to pour the thing in one go if you could get the ER into all the tight corners first and work out to the body after.

For complex parts we would do just what you are saying, put several injection points into the mold and open and close them as it filled so as to not get pooling. After the smaller complex sections were saturated we would close off the hose and open the body hoses (which were larger) and fill the rest of the mold.
A word of caution:
you must put the main body ER hose very near the sections that will be saturated first, if not you end up with dry spots. It took 3 runs to get this process right but we wasted no ER or carbon fiber! We used glass matting and mineral oil and worked with clear molds. You could do the same thing hear and just use regular glue (watered down as needed) and sand until you get the process down!

[walter]

Thanks Cameron! Much appreciated!

[greybeard]

Cameron -Thanks for the testing offer .
Re your pm, and the shape.
If I were to spin test samples in the attached set up, would they be close enough to your dimension requirements ? I've only drawn 4, it's easier !
If the small "troughs" were 1/2" wide and 3/8" deep, and the pipe they were in was 4" in diameter, the face nearest the rotational axis will be nearly flat, but not quite.
Would that matter to any great degree ?
I suppose a small insert, floating on the surface of the resin, might give me a flat surface ?

Regards
John

[307startup]

I remember a while back someone was talking about using an industrial/bakery dough mixer for the Epoxy-Granite materials...so I thought I'd show y'all this...
http://cgi.ebay.com/Berkel-BA-20-20-...QQcmdZViewItem


http://cgi.ebay.com/1HP-S-S-BARREL-M...QQcmdZViewItem

[lgalla]

Vacuum infusion or pressure injection is not going to work with aggregates.With glass or carbon fiber it is a different story.The ratio of glass to resin is 50% by weight.The target in E/G is 10%.Injecting in RTM sometimes produces "wash" which pushes the fibers from the injecting pressure.I assume wash would be a big problem with aggregates.The injected resin would push the aggregates to gether Requiring more injection pressure,possibilly also pushing the aggregates apart causing high ratios.Any injecting or infusion must be done in a closed mold
Larry

[jhudler]

Ok I've ordered the 37-127/37-606 from uscomposites and 2000/2060 from fiberglast to experiment with. And some 37-058 to play with diluent ratios in the 37-127.

I'm also making an aluminum/lexan mold to generate the 1/2 x 3/8 x ~15 (I know you want 7 1/2) test pieces. It will allow me to not only make the test pieces, but play around with pressure and infusion mixing. I know, I know I've been admonished on the infusion part... but I'm playing a hunch and besides it doesn't cost me anything to try.

If the pressure part works then perhaps theres a way to make a cheap mixer then can supply an almost continuous flow of E/G mix into the mold.

If I can get the viscosity down to where infusion works without inhibiting cross linking then perhaps this might be viable after all (crossing my fingers on this one).

Also have some various aggregates on order with more to get... still haven't see the TiB2 yet... think they stiffed me tha blighter's!

[ckelloug]

Jack,

Where did you find the 37-056 for sale? Does US Composites have it?
Reichhold has an excellent brochure on their epoxies and the mixing ratios http://www.reichhold.com/docs/litera...ochure2007.pdf

I just got done slinging half a bucket of drywall mud on the joints of my 70% completed shop.

I was going to make my sample molds out of teflon so I don't need mold release. The 3/8 by 1/2 by 7 1/2 dimension comes from ASTM D790-86. This is the biggest sample I can handle in my test machine without different fixtures and be compliant with the ASTM D-790. I suppose to be on the up and up, I need to have my load cell formally calibrated. It has a factory calibration right now which Admet spends lots of time saying not to rely on.

Good to hear from you here. I haven't gotten much done lately due to a mammoth debugging exercise in my day job but I haven't forgot that I'm supposed to be sending you the aggregate simulator code.

Regards to all here,

Cameron

[jhudler]

On the 37-058... It's another one of those... I'll see if I can find a sample to send you... should be no problem. Google +CAS +"68609-97-2" that's the diluent 37-058 Alkyl (C12, C14) glycidyl ether.

[harryn]

I was going to make my sample molds out of teflon so I don't need mold release.

Cameron

Another interesting option is UHMWPE (ultra high molecular weight poly ethylene)

Basically, it is like poly ethylene, but the very long molecular chains make its surface properties more like teflon (from a friction perspective) It surprised me to learn that it is the toughest known substance (not strongest), and has less (not none) creep than Teflon based materials.

It is also a lot cheaper, esp in sheet form.

I am studying it partially because I am considering it for slides in my router project. (yes, I know bearings are better, but budget is a big deal)

[ckelloug]

Harryn,

Interesting on the UHMW for machine parts and molds. I wasn't thinking about it. UHMW is what spectra fiber is made from. See http://www.honeywell.com/sites/sm/afc/spectra_fiber.htm Spectra is what a lot of rock climbing slings are made from.

I was thinking about molds for samples when I posted, not machine part molds. Teflon would be too expensive for me to consider for a whole machine. Yikes. I'll probably use aluminum for machine part molds. I will however have to cast several hundred samples in my formulation research and a sample mold that has nothing stuck to it and samples that are easy to remove has a definite advantage.

Jack,

Don't worry about getting me a sample of 37-058 yet. I was offered some by the regional Reichhold distributor but I declined because I'm not quite ready for it. Now when my shop has electricity in it in a few weeks, it will be another story. For the moment, I just completed a long day of drywall mudding and sanding. I'm almost done and it's only taken a bit more than a year to build a 24 by 14 shop. Sleepy time now.

Regards All,

Cameron.

P.S.
To the audience of lurkers: Remember, questions are as valuable here as answers.

[greybeard]

Current recipe I'm trying to accumulate -

3.2mm small gravel
0.8mm sand
200micron G800 zeeospheres
50micron ?
12micron G200 zeeospheres
3micron Cabosil ?(silica fume)

Any suggestions for the 50micron component would be most welcome.

Regards
John

[walter]

microcrystalline silica?

[jhudler]

I was just quoted $4 a pound for a single 50 pound bag of G-800 with price breaks to $.78 at 40 bags. This is with local pickup.

What has everyone else been quoted?


Thanks,
Jack

[romihs]

I was just quoted $4 a pound for a single 50 pound bag of G-800 with price breaks to $.78 at 40 bags. This is with local pickup.

What has everyone else been quoted?


Thanks,
Jack

Jack,

WOW!! I contacted 3M directly a few weeks back and they quoted me between 0.38 and 0.5 EUR's per pound (I requested a quote for three types of Zeospheres). These quotes were for single bags, I did not get a bulk discounted price.

Try contacting 3M directly....

Regards

Sandi

[walter]

I don't think I paid more than $25 per 50lb bag of G800/G850

G200 is probably twice that price, I can't find the receipts.

EDIT.
I should also mention the store.. It was The Cary Company.
_

[jhudler]

Walter,
Where did you buy this?
I'm going to try there Inside sales dept tomorrow and see if I can get a better price.

Jack

[lgalla]

Jack try http://www.thecarycompany.com/faq1.html
Larry