Decision skills frozen in silicone...

[obscurecreation]

As a miniaturist wanting to specialize in electrics and lighting, I am at the point in reproducing that I have made masters and some silicone molds. Since I want to cast high quality clear resin, I know I need to move to a vacuum or degassing solution before bothering to start to pour. The molds I've made so far were mostly tests on the masters not so much for production scale...

My question/plea is "why am I so seemingly frozen with respect to my decision making skills when it comes to vacuum or pressure parts?"

I have read like crazy, have seen people use pickle jars etc etc and have come to the conclusion that I want to buy a solid solution but don't want to waste money nor over buy equipment that I already have or have and could 'tweak'.

I have a smart jet compressor that would likely not quite be enough - or maybe I'm wrong.

I have a shop compressor - small but likely more than sufficient for the size of my projects.

I do not have any pots (although lots of gallon pickle jars) nor any vacuum equipment and only the gauges on the smartjet.

Most of my molds are 6" X 3" X 2" or smaller and some do have very tiny stems that might be injection molded in other applications but not in this case.

Maybe it's because there are TOO many options and variables on the market that has me feeling hamstrung. I did come across one website that had a step by step for most components but maybe I need part #'s...

I'd like to be under $250 all in if possible but would go to $350 if I had to.
Does anyone have links to kits or lists for set up that I can work part by part from? I am willing to consider both vacuum or pressure kits and am not sure why one method would be better for my situation than the other. I would like to use the method for both my mold making and castings. ATM I'm using OOMOO30 and various cast materials such as Crystal clear, casting craft etc. 80% of my casting will be clear with the remaining 20 as white, colored, metal-simulations and unrelated, plaster.

I do run a blog which might better demonstrate what I'm trying to do:
obscurecreationsbytyla.blogspot.ca
if helpful...

If anyone has any input to shift my butt from 'knowing I need to move forward" to 'putting money on the barrel and ordering some equipment" the effort would be greatly appreciated. Actual links might receive undying gratitude.

Thanks,
Ty

 

[robn1]

Lots of info on the subject http://www.therpf.com/search.php?searchid=6045215
this thread was especially useful http://www.therpf.com/f9/vacuum-degassing-silicone-query-70274/

 

[obscurecreation]

Thanks for the reply. The other vacuum/pressure messages on here I'd already read which is why I thought that my question might get some additional answers that I can use to start shopping with...

For example none of the references you list tell me why is one person using a pot 'of some sort', a home use pot or even 'only an approved vessel'? I see some pictures that have one sized gauges and another, well another but no reason as to why or which is preferred. Why should I choose vacuum over pressure - I saw a few loose opinions but maybe that one I have to research at more of a scientific than a user level?

Some of the links say that you need to pull 28" but right in the text they say that they are only able to pull 27???

These are some of the reasons I chose to post a msg with some specifics rather than just re-read the other forum posts again and guess.
I like to be safe but also frugal and balance that all in a DIY atmosphere...

Anyways, thanks for the links though

 

[cavx]

I have been reading all the links and I have some theories and questions that I don't think I found answers to.

I owned a Vacuum Chamber in 2006 where I probably would have been better off with a pressure chamber for what I was doing at the time. Because of all the fails when using the chamber, I actually learned how to mix and pour clear casting resin bubble free (sometimes). I think now that a pressure pot would have given me a better end result and would have crushed the few small bubbles I would get from time to time.

I am no expert, but liquids under pressure/vacuum behave quite differently than they do at 1 atmosphere or normal pressure. Take water for example. At 1 atmosphere (at sea level) and it boils at 100 degrees C. Place it in a vacuum, and it boils at closer to just 20 degrees C. Place it under pressure, and I sure the boiling temp goes up. Does anyone know what that might be?

What does not seem to be discussed is how the pressure shift alters the temp and ultimately must affect the curing times of the product.

I recently bought some cold cast clear elastomer. The idea was to pour thin clear rubber sheets and the issue I was having was that there was not enough depth to the poiurs and as a result, there was no real heat generated during the exothermic reaction and the product took days to cure. I got very mixed results and it was allot of money spent with not allot of the product being able to be used.

So I do wonder if vacuuming the stuff not only removes the bubbles, but also raises the temp significantly to help it cure better?

So if a vacuum raises the temp, does a pressure pot not lower it? Would this not lengthen the curing time of a casting resin or cooling affect counter the heating resulting in the same curing times? One batch of the stuff I used basically boiled and set in the chamber and it was complete throw out.

When I was researching this stuff, it was suggested that liquid nitrogen be pumped into the chamber to "freeze" the air to lower the temp and stop or at least slow the exothermic reaction.

Any thoughts on this?

 

[Locry]

I'm pretty sure pressurizing increases temps, not the other way around. Vacuuming I think would not raise or lower the temps... not really sure. But increasing pressure will increase temps... by how much I'm not sure, maybe negligible at 32 psi