Pressure Pot/Compressor Combo for Resin Casting

[Frogbot]

I'm going to bite the bullet and get a pressure pot. Seems like there's a lot of options out there and possible dangers. Just seeing if anyone can give me some advice.

I can get pots ranging from $120 to $350+.

Wondering if I could rig this up to work to do it cheap:
http://www.supercheapauto.com.au/online-store/products/Blackridge-Air-Spray-Gun-Siphon-Feed-10-Litre.aspx?pid=156470

I got a quote for a more professional pot for $350...

They booth have a of max 80psi, I think I only need 40psi?

In regards to compressors someone quoted me $1100 for one with 12cfm. Is this overkill? I can use a cheap one for $88

http://www.supercheapauto.com.au/online-store/products/Blackridge-Air-Compressor-Direct-Drive-1-0HP-40LPM.aspx?pid=296171#Recommendations

Would this kind be sufficient? I'm guessing it has to maintain the pressure for the time it take the resin to set?

Thank for any tips in advance!

[nubbinator]

I have a Binks rated at 130PSI or so (I forgot the exact rating).  I work between 40-70PSI.  I would never trust anything that isn't rated for more than I use.

That one you linked looks a lot like one of the ones you'd get from Harbor Freight.  It looks shady.  I'd stick with something known to be good.  There are many sites out there with recommendations on good cheaper pots

As for compressors, a good cheap one is plenty.  The main one I use is a tiny ass cheap one.  You don't need much in the way of a compressor, just reliability.

[FoC_Tow]

I'm not an expert on casting Frogbot, but wouldn't a vacuum chamber and compressor be the common choice for getting bubbles out of the casts?

I just did a quick search on ebay, and there are quite a few vacuum chamber sets around 200$+.
They are usually described as silicon casting (or shatter purifying...xD) designs, so I'm not sure if they are appropriate/powerful enough for resin casting?!

Heres a few links for reference: 
01
02
03

It would definitely be awesome to see what you can make with one since your casts already look amazing! 

Edit: Typos & Nubbs was faster

[Frogbot]

I have a Binks rated at 130PSI or so (I forgot the exact rating).  I work between 40-70PSI.  I would never trust anything that isn't rated for more than I use.

That one you linked looks a lot like one of the ones you'd get from Harbor Freight.  It looks shady.  I'd stick with something known to be good.  There are many sites out there with recommendations on good cheaper pots

As for compressors, a good cheap one is plenty.  The main one I use is a tiny ass cheap one.  You don't need much in the way of a compressor, just reliability.

I think you're right, it's probably better to err on the safe side. Thanks for the compressor tip Nubbinator, that's gonna save me a lot of cash!

I'm not an expert on casting Frogbot, but wouldn't a vacuum chamber and compressor be the common choice for getting bubbles out of the casts?

I just did a quick search on ebay, and there are quite a few vacuum chamber sets around 200$+.
They are usually described as silicon casting (or shatter purifying...xD) designs, so I'm not sure if they are appropriate/powerful enough for resin casting?!

Heres a few links for reference: 
01
02
03

It would definitely be awesome to see what you can make with one since your casts already look amazing! 

Edit: Typos & Nubbs was faster

Thanks for tip FoC_Tow! I've got a Ghetto Vac Chamber that I thinks working pretty good, no micro bubbles but I'm still getting bigger ones. I've tried some casts using a vac the whole way but It's creating caps that are just skin(resin just lines the walls)!

[FoC_Tow]

Thanks for tip FoC_Tow! I've got a Ghetto Vac Chamber that I thinks working pretty good, no micro bubbles but I'm still getting bigger ones. I've tried some casts using a vac the whole way but It's creating caps that are just skin(resin just lines the walls)!

Show Image

Sure, your welcome Frog! :)
Thx for sharing pics of your DIY vac chamber, love the ghetto rig setup man pretty creative!

It's interesting that casts curing in the vac will create caps that are 'skin only'...
Does that pretty much mean the keycap walls become very thin?

I'm wondering if the vac would cause a two part mold (top & bottom) to thin out the walls by sucking out the resin and therefore create thin walls.
But then again the pressure around the mold should be the same so idk if that might happen...

Could you eventually use a vac after mixing the resins, to remove most bubbles created from mixing already before casting the molds? =)

[domoaligato]

I have a pressure pot that came from the one and only mkawa https://geekhack.org/index.php?action=profile;u=5606
it is pricey but safe. well worth the money.

edit: I also bought my air compressor from him...

[mkawa]

Please please use only ASME rated pressure vessels and vacuum rated vac vessels. Yes, I do build casting systems for folks, but my priority is keeping people safe, and I'm happy to give personalized advice if you ping me.

Vac and pressure vessels contain a very very large amount of potential energy, and your life is not worth the risk of a containment failure!!

[Frogbot]

Thanks heaps for the feedback. It's given weight to just how dangerous these processes can be.

I did a bit more research and found this article.
http://www.resinaddict.com/blog/2013/10/safety-announcement-do-not-use-harbor-freight-pressure-pots/

It mentions they still recommend the one I can get here in Australia for around $100.
Due to this, the price and ease of obtaining I've gone with this pot for the moment. At $100 it's almost disposable...  and if I maintain my interest in casting I'll get a safer one for more $$$ in the future.

To be as safe as possible with questionable equipment I've set the pot up in my spare room and am pressurise and depressurise the it from outside the room via the pipe from the compressor. My compressor has a regulator so I can limit it to 40psi (the pot has a recommended max of 90psi). I'm comfortable this mitigates some of the risk... until I can afford something safer.

I'm also doing the same with the vac chamber as well as I can release the vac from outside the room via the pump. Again, thank for the info.

I'm wondering if the vac would cause a two part mold (top & bottom) to thin out the walls by sucking out the resin and therefore create thin walls.
But then again the pressure around the mold should be the same so idk if that might happen...

Could you eventually use a vac after mixing the resins, to remove most bubbles created from mixing already before casting the molds? =)

I think this is could be cool to try, it was super fragile to get out of the cast, I'll dig it up to post some images of what I mean.

[FoC_Tow]

Very welcome Frog! And I'm super glad if I could add anything that ends up being helpful! =)

I have some experience with making one piece silicone molds for fine, detailed concrete casts and I never used something as advanced as a vac chamber, but always wished I had access to one...
So I can only estimate very roughly what it might be like, but I think getting rid of bubbles as much a spossible before casting can't be a bad thing if the cure time allows enough time to do it! 

Also on a side note, I've read a few times that people suggested to dab or pour silicone in small detailed area first when mold making,
but from my experience and the tutorials I've seen its usually recommended to just pour from one corner (so only on one spot don't move) and let the silicone work its way on its own,
as moving around (and 'overlapping' pours) might lead to more bubbles getting trapped.

So depending on which way you prefer this might be something to try as well as I never had issues with bubbles trapped in silicone molds! 
Not sure if this can be applied to the resin casting step somehow tho since you pour thru a channel inside a at least two part mold.