yves
New Member
Posts: 1
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Post by yves on Oct 4, 2018 7:51:26 GMT -5
I am new to casting and have made a few small molds so far. My business is as an engraver, firearms, plate printing etc, and want to cast my engravings both for sale and for my own history collection. I have looked at your videos, but I cannot find anything regarding the type, part no, mfg, etc for a vacuum chamber and how it is used. The mold material I use the HS 1,2,3 and the Mold Putty. For casting I use Alumilite White (Amazing Casting Resin). All are flat molds. I wish to remove as much of the bubbles as I can from the silicone HS material as possible. The most I mix at one time would be 3-5 OZ of silicone, so I do not need a large machine. I have seen these on Amazon, but I am asking for some recommendations on units and how they work.
Also, the white cures very quickly so can it be vacuumed or should I use another material.
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Post by notoes on Oct 6, 2018 7:48:12 GMT -5
I don't have a vacuum chamber and I don't normally have a lot of trouble with bubbles. That being said, I also work with small molds and small castings so anything that needs to be large would benefit from the longer open time resins. To prevent bubbles, I mix as slow as I can to prevent introducing air into the resin, pour from a high level, and try to pour slow. Then I add some sort of "vibration" by either tapping the mold box or vibrating the work top- I have a thin board type that I use to cover the countertop and pour on so I can "bounce" it a bit and that moves any bubbles that crop up. Any electronic tool that causes a vibration (hair clipper, small hand saw/cutter, etc) will work to add vibration. Also "painting" the surface of the item than you are making a mold of helps with the bubbles next to the item's surface. So for the most part, I don't use a vacuum chamber and don't have a lot of trouble with bubbles.
But the reason you can't find a specific type/model for a vacuum chamber is that most any one will work, I've seen where some people make their own and it works fine - just as long as you follow the safety guidelines when you build it. As long as you use the pressure guidelines in the data sheets on each product, you can use any kind of vacuum chamber you want.
As to the Alumilite White, if I'm not mistaken it might not have a long enough open time to be vacuumed. You could pour in "layers" and just manually tilt and rotate it until it hardens if it has a big open area to pour into. All resin will stick to resin without any problems so doing layers is easy. I constantly do this myself as I am known to have too much or too little of the resin mixed up at one time and have to do layers anyway.
Feel free to ask any question you might have, we've got people who have experience in all types of equipment and are willing to help. What I like the most about Alumilite products is you don't need a lot of expensive equipment (or a huge work area) to get started and to use them.
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Post by carol - Alumilite Corp on Oct 9, 2018 7:32:28 GMT -5
Good Morning,
Vacuum\ degassing too help obtain a bubble-free mold when using silicone rubbers and a slower setting resin a vacuum chamber is required. If it is a resin (like the white) that don't have a long enough open time to vacuum but can go into a pressure pot for eliminating air bubbles in finished resin pieces vacuuming the silicone is a must. Otherwise the air pockets/voids in the interior of the silicone can be pushed to the cavity putting pocks/pimples on the resin pieces. A small vacuum chamber can be purchased many places, Amazon is one as you stated... another place that customers have told us about is Best Value Vac in Chicago area, several sizes. I have not heard anything negative about their equipment or service, we do not sell de-airing equipment vacuum chambers or pressure pots.
The silicone and/or resin can expand 4–5 times under a vacuum, so make sure the mixing container is large enough to hold that volume so it doesn't spill over the top of the mixing vessel. Been there done that! There are good instructions with most equipment you purchase or call customer service of where you purchase if you are in doubt or the instructions seem vague to you.
After vacuum some care needs to be taken so no bubbles are introduced in your pour technique. Always pour high and thin stream starting from the corner of the mold box letting the silicone flow freely in to the box. Usually, this way will not introduce any new bubbles into the mold.
To all have a great day!
Warmest Regards,
Carol
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Post by MJessen on Oct 15, 2018 10:48:08 GMT -5
Carol,
I produce a trophy type object (very simple, no complex pockets and 1 inch deep at its thickest) using open pour. Each pour is 28 fl oz. I have been using RC-3 (black).
I have been struggling with bubbles in final product and am going switch to using a vacuum chamber. My plan is to utilize a 5 gallon vaccuum chamber with a 5 cfm pump to degass the resin prior to pour. I would expect the degassing to take 5 minutes (would this be correct?). Is this a sound solution, and should I switch to a different resin due to open time.
Thanks for your advice,
Mark
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Post by salmon on Oct 17, 2018 13:42:25 GMT -5
I degass my rubber before pouring and then I use a pressure pot for the mold making. I pressurize to 60 psi. When I pour resin, I pour it into the mold, put it in the pressure pot and again use 60 psi. The pressure pot will collapse bubble so that they are very tiny to non-existent to the eye. That being said, if you put in resin into a mold that has bubbles hidden in it, you may/will get bumps on the surface of your cast item from those hidden bubbles in the mold that are collapsed while the resin cures.
Peace,
Tom
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bill
New Member
Posts: 18 
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Post by bill on Dec 2, 2018 10:50:55 GMT -5
I have to agree with Salmon, degassing is a must before and after mixing (time permitting) and compression at no less than 60 psi. I also use two three inch squares of plastic bag between the cap and bottle of part B. I have found this great when trying to reopen the bottle (part B) and seems to help with moisture contamination.
On bumps in the projects, I have found that older products (part B) seems to crystallize from moisture contamination. And it is these crystallized chunks that cause the bumps. This happens most often with Flex rubber products.
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