longmc Posted March 14, 2008 Author Share Posted March 14, 2008 I'll try flipping the gasket over when I break it down this weekend. The Smooth-on 310 has a 20 minute working time and is clear so that I can work out almost all the bubbles by hand and then it's solid in about 2 hours. Quote Link to post Share on other sites
pbhawkin Posted November 5, 2008 Share Posted November 5, 2008 Hi all, I just found this topic and it is exactly what I am doint...well about too! I have the 10 litre (2.5 Gallon) paint pot and a 2Hp compressor and have also got a 15mm Polycarbonate lid with vacuum guage so I can observe what is going on inside. I have used a very thick RTV to seal the top of the paint container rim when the flat Poly lid is on and the vacuum unsures there is no leaks when it 'sucks' it down. Now I have two issues. Firstly using my compressor as a suction device I can only get down to 25" of Mercury which is enough to cause bubble formation but not for them to burst!! And so am looking at buying the Harbor Freight "AIR VACUUM PUMP WITH R134A AND R12 CONNECTORS US$12.99 96677-6VGA " to get a better vacuum. I am surprised that a venturi effect will give such a good vacuum as claimed (28.5" of Mercury) when using 90PSI airflow!? Has anyone used any of the standard refrigerator gegassing pumps available to degas? They are rated in terms of CFM and don't often mention how many inches of Mercury they pull (I understand the CFM rating is how quickly they will pull). Secondly, when you pressurise the resin in a mold do you need to have a 'extra' resevoir of resin to flow into the mold as the resin in the mold is compressed (bubbles get smaller) to take up any volume loss? Regards and thanks in advance Peter Quote Link to post Share on other sites
terryt Posted November 5, 2008 Share Posted November 5, 2008 I have the Harbor Freight venturi vacuum pump and use it with Rival Seal-a-Meal Stackable Round Vacuum Canisters. Click Here! Most of the molds I make will fit in one of the cannisters. I can only get about -27HG with the pump. It is sufficient to remove the air bubbles in the silicon. If you look at after market resin parts you will find a block of resin attached to the part, that is the casting lug (reservoir). Quote Link to post Share on other sites
pbhawkin Posted November 5, 2008 Share Posted November 5, 2008 (edited) Terryt, thanks for the reply. well 27" is better than the 25" I am getting now! Interestingly the 25" is when I connect up the air intake of my 2Hp compressor to the vacuum tank. (I would have thought it would drawn more?). That is why I was a bit surprised by the claim of 28.5" for a venturi vacuum pump. Edited November 5, 2008 by pbhawkin Quote Link to post Share on other sites
terryt Posted November 5, 2008 Share Posted November 5, 2008 I forgot to say that even at -25HG you should be able to de-air most any silicon, unless it is super fast setting and is real thick. I use different Smooth On silicon rubber and get great results. Quote Link to post Share on other sites
pbhawkin Posted November 5, 2008 Share Posted November 5, 2008 Nope. My RTV is quite thick and it doesnt have the dramatic rise let alone the collapse you get with adequate vacuuming (certainly not at 25"). Quote Link to post Share on other sites
etripke Posted December 7, 2008 Share Posted December 7, 2008 longmc:Your compressor is fine, I'm using a 1 1/2 HP compressor with a small tank. Recommend pressure is 40 PSI. Make sure you print the coupon for the pressure pot, take it with you to Harbor Freight, the regular price is $119.00 in store. Here is my setup: I didn't use the valves, I eliminated the pressure gage and went direct into the pot with a quick disconnect. I use the compressors gage for the pressure setting. The pressure relief valve has the round ring. The blue thing in the picture is a vacuum run by compressed air, I use it to remove air from my molds. I was also purchased at Harbor Freight. I have found this thread, and am very interested in giving it a shot myself. Where can I find a suitable Venturi Vacuum Pump for the set up. I notice the blue box you have, and cannot seem to find anything like it online. Thanks Quote Link to post Share on other sites
doctorpepper Posted December 7, 2008 Share Posted December 7, 2008 i just want to say that after 2 years of using the HF pot, it hasn't failed me, however, with age, the attachment points for the 4 wing nut handle-thingies is starting to protrude more out of the pot, like the pressure over the last 2 years has caused the metal to warp. i'm gonna be looking at purchasing a new one soon drPepper Quote Link to post Share on other sites
terryt Posted December 7, 2008 Share Posted December 7, 2008 I have found this thread, and am very interested in giving it a shot myself. Where can I find a suitable Venturi Vacuum Pump for the set up. I notice the blue box you have, and cannot seem to find anything like it online.Thanks Looks like Harbor Freight doesn't carry that vacuum pump any more, however, it's been replaced with this one: http://www.harborfreight.com/cpi/ctaf/disp...temnumber=96677 Quote Link to post Share on other sites
jcfay Posted December 7, 2008 Share Posted December 7, 2008 This is a great thread. It should be pinned... It's just got so much valuable casting info in one place, IMO. JON Quote Link to post Share on other sites
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