resin cast help

[Sith_Lord_Hritz]

Ok I know that there are many threads already with tips and Q&A about casting resin parts. I have read most of them and watched a lot of you tube videos about casting. I know that I will use silicon for the mold but my question is not what is the best its what do you casters like to use. What brand of silicon/resin ? most of the sites I have seen point to smooth-on or alumilite. I will like to mold and cast custom made parts for future saber and blaster projects. I don’t have any equipment as of now but I was thinking that I would buy a vac chamber first. Do I really even need one? Do most of you here use any equipment or just rough it.
Thanks

 

[sskunky]

Ok I know that there are many threads already with tips and Q&A about casting resin parts. I have read most of them and watched a lot of you tube videos about casting. I know that I will use silicon for the mold but my question is not what is the best its what do you casters like to use. What brand of silicon/resin ? most of the sites I have seen point to smooth-on or alumilite. I will like to mold and cast custom made parts for future saber and blaster projects. I don’t have any equipment as of now but I was thinking that I would buy a vac chamber first. Do I really even need one? Do most of you here use any equipment or just rough it.
Thanks

HI,

A vac chamber is a must in my book, if you want to eliminate bubbles in your molds.
Not sure what resin or silicone as I am in the UK and I'm sure it's different here.
Mark

 

[Reactor drone]

Vacuum chambers are great,especially for larger moulds and moulds of complex shapes that will entrap rising air bubbles near the surface.

Cost is also a factor in deciding what silicone to use, a fast set,low viscosity silicone like pinkysil might give you better results if you don't have degassing gear but will be more expensive than ultrasil for example.You'll also find different hardnesses are available,a harder silicone will give a more self supporting mould but it's not good if you have deep undercuts.

I've been very happy with ultrasil for most projects,mid priced with a good work time to allow degassing and large pours.

 

[robstyle]

You can easily get by without an evac for silicone. Just mix it up and brush it in then lift it up high from the mold and pour it thin. That helps eliminate bubbles. The way you make your mold has alot to do with it as well. Most people dont make box molds but I find them incredibly easy to work with. The past couple days ive been working with molds that had a clay wall to pour silicone into. Im forced to hold the molds while the material sets due to the odd shape of the molds. If they were a box mold, I could clamp them and walk away.

 

[runnriottt]

I have used a couple of silicone brands, one here in Japan from a local company and rebound 25. I too like box molds, but some shapes do not allow it. Rebound is awesome stuff.

As far as resin, I have used a product called Hei-Cast and I like it the best so far. The other was a resin from Descar plastics, good stuff but has to be mixed really well. The Hei-cast mixed better, but smelled bad.

Depending on what your casting up, a 1 to 1 mix ratio is the key. Large volume stuff you could get away with different ratios, but its a pain.

 

[Sith_Lord_Hritz]

Yes, I did see that the different kinds of resin have different mix ratios. I would like to stay with the 1:1 by volume type because I think it would be the easiest for me to mix without buying a expensive scale. Also I did see a video where a guy pours is molds by poking a small hole in a cup and letting the mix slowly pour from about 3 ft into the mold box, he said that it will help eliminate most bubbles without a vac. Thanks for answering my questions so far im thinking that I may not need a vac camber, can I use the vac to get the bubbles out of the resin or is that even a problem? Do the bubbles in a finished cast only come from the mold pour or a combination or the two?

 

[Jaded Monk]

If you have the spare funds or are planning to go into production, on something that will pay for the gear, Vacuum is a must.

However, if you are one the rest of us, go with a low viscosity, long pot life resin and silicone, and as stated before, pour from a significant height and you will be just fine. Longer work times mean you have a better chance of tapping out bubbles. Lower viscosity mean the bubbles rise to the surface more readily. Watch out for ambient humidity. It is often quite humid in San Antonio, TX and I my resin often foams up as it kicks. PITA.

Cheers,

JM

 

[Sith_Lord_Hritz]

Thanks for all the help guys
Well I don’t plan to go into production making resin parts I think I would still like to have a vac chamber for the parts that I do make just so they look the best and you never know down the road if I make and cast some parts for people here I want them to look perfect. My question is can anyone point me in the right direction for buy this set up? I have searched Google and ebay and only found a few options and don’t want to be over charged for junk. Any help would be great.
Thanks

 

[exoray]

If you want a vacuum chamber the most economical way is to purchase a pressure paint tank (Harbor Freight has them cheap) and convert it with a vacuum pump...

If you want a turnkey tank, both Alumilite and Smooth On have tanks for sale but they don't come cheap...

You also need a vacuum pump, electric ones are generally costly, but in the US there are a bunch of older automotive and home AC service vacuum pumps that can be had pretty reasonable... I have picked up a few at garage sales for under $20...

The absolute cheapest vacuum pump is a Venturi pump from again Harbor Freight, gut the device from the housing and hook in into your tank... You need an air compressor to run it but it does quite a good job...

Personally for starters I wouldn't invest in a tank right off the start, with a slow 24 hour silicone and some attention to stir and pour techniques you will find for many applications you can get by just fine without vacuum...

As for brands, as someone said you really need to just test some out... They are all differnent and you need to find one you prefer... I have tried all sorts of brands and have found that as long as you don't go bottom basement bargain that they are for the most part decent...

Smooth On is real popular and I guess for beginners they are a good choice, their Moldmax line of silicone and thier 300 series resins are a good starting point and they offer great customer support...

 

[stormtrooperguy]

i always suggest using what you can get easily.

reynolds advanced materials has a retail outlet near my house, so i can get all the smoothon products at no additional markup right there, right now, no shipping or waiting needed.

thus smoothon is the no brainer answer for me

 

[adamata]

I use Easyflo-60 from polytek.com

http://www.polytek.com/products/poly_plastics.html

data sheet:
http://www.polytek.com/products/EZFlo2005.pdf


This stuff if very forgiving, easy to work with (1:1 by volume), mixes by hand and hardens in minutes. No odor or fumes as well.

I am not sure if they still do this, but if you call them tell them you want to try out a small sample of a product and they will give you some free, you just pay for shipping. It's usually the smallest containers they sell, which is still enough to do a lot of castings.

 

[ArtisanProps]

I've never heard of anyone doing this, but I won't call it my own technique
because I'm sure someone out there has thought of this lol

I bought a paint pressure pot at harbor freight for around $80.00 US and since
I use a lot of silicone, bubbles are a problem. So one day for the hell of it I
took my Air compressor (cheap one) and hooked it up to the pressure pot
and got it ready for casting, I sat for a momment and thought " I wonder
if applying pressure to the silicone would remove the bubbles like a vacuum
chamber would" So I tried it. I got my piece ready, mixed up the silicone, and
popped it into the pressure pot and set the pressure to about 50 PSI and left
it for the time needed for the Silicone to cure.... After the nessesary time had
passed I removed the part from the silicone and cut it down the middle with
an exacto knife to see what the results were.... I was very pleasantly surprised
to see that not only did the silicone capture the detail perfect, but there
wasn't one bubble in the mold. Ever since that day this has been the
technique I use since it's been full proof, plus it's a hell of a lot cheaper then
buying a vacuum tank

Just a little warning though.... Usually Silicone needs many hours to cure and
leaving pressure in a tank can be very dangerous if the welds, fittings,
or any other part of the pot is faulty.. I always check everything when using
my pressure pot and when I do pressure mold silicone, I place the pot far
away from anything in the rare case that it my go boom!

I'm not trying to scare anyone lol because you face the same risks
when you pressure cast. I just wanted to add the little warning to keep you
guys safe

 

[Sith_Lord_Hritz]

Ok I was thinking of getting this vac camber http://www.alumilite.com/ProdDetail.cfm?Category=Equipment&Name=Vacuum Chamber
Anyone ever use it or hear good/bad things about it. If I get this one I was thinking I would get a harbor freight vac pump to use with it. Anyone have any comments?

 

[exoray]

Ok I was thinking of getting this vac camber http://www.alumilite.com/ProdDetail.cfm?Category=Equipment&Name=Vacuum Chamber
Anyone ever use it or hear good/bad things about it. If I get this one I was thinking I would get a harbor freight vac pump to use with it. Anyone have any comments?

Get a pressure paint pot and convert it you will save money... Harbor Freight regularly puts them on sale for about $35, or you can pick them up used on ebay for cheap...

 

[Sith_Lord_Hritz]

thanks for the help so far guys. i have another question im making my own vac chamber from 12" PVC i just need to know what to use as a gasket for the lid to seal properly, any advice?

 

[Sith_Lord_Hritz]

anyone?

do you think thin rubber will work, like the kind used for roofing?

 

[exoray]

Try it vacuum is pretty easy to hold with a gasket as it actually helps the gasket stay put...