New Addicts here for treatment

[NebuK]

Mangozac edit: I split this thread from its original location as the discussion is more appropriate in the Dr Polymer subforum.

Heyyas,

thanks for your replies first. I find the organization of this forum a little confusing, so sorry for getting the wrong one...

Anyways, back to topic...

I've just made a few photos of some example parts (i don't have too good examples lying around atm...). They're not the most complicated ones (and yet to mod, thats why i have them lying around raw...), but are a good example of what i'm talking about. I reckon they could be tricky, which is why i chose those two for demonstration purpose...
http://tmp.kanojo.de/figure_to_cast/

I do know that casting and casting equipment can get quite costly. There are two usecases for me where i can't pass on casting myself:
- Some kits i want to mod, add parts and the likes - and i'd like that preserved and reproduceable...
- There are some kits which aren't produced anymore and are very rare. It'd be a waste not to preserve them ...

While the second is debatable i'd like to concentrate on the first one ;P.

To pressure casting: I've only understood that pressure casting != vacuum casting after you wrote it and i read around again. I do have a large compressor, quite some air-pressure equipment - although sadly none of those "pressure pots". When i've checked around here in germany the price did floor me. The cheapest i've found was about 3 times as expensive as the cheapest i've found linked for .uk and .us people here in the forum... does anyone have a hint for me? I'd even not refrain from modding a pressure cooker (i think the common german models are working @ 1.8bar, the emergency relieve valve is @2.2bar or something - not too far from the magic 50psi (=3.44 bar?) threshhold that is said to be the limit after which nothing changes anymore? I reckon this is very very dangerous and i'd put the pot only under pressure when its in a tight room somewhere far away from any living thing ;P.

But on to the neater things without any dangerous pressure ;P. If i have access to a small hand vacuum pump (i do), will that give me any advantages as in "quickly vacuum your resin in a pot before pouring it and magic will happen!!11" (same with the silicone?), or is it just no use? And about the techniques without pressure at all ... i've seen some tutorials where people constructed molds with complicated air relieve systems (well, complicated ... a air relieve champer between every part, a seperate pouring channel and a large "exhaust" channel through which is not poured...) - when just dumbly applying all of those little techniques, how bad will my failure rate get?

Also, now that i've realized that there can be real tricky mold constructions i've also realized that i haven't found good information on that topic yet. Depending on how my part looks, how bad the undercuts (right term? uhh, its new terminology for me even in german, so my english must really be hard to read right now Oo) are i think there must be tons of ways on where to place the intake channels, air vents, where to "cut" the mold in half (or, if pouring silicone two times, where to put the clay in the first step...). Could someone point me to some information on those topics?

Huuuu, now i've written a too long post again. Sorry ＿|￣|○
However, i'm really greatful for the nice help here already ;P. Thanks, and Regards
- NebuK

PS: If there's someone from germany here, do you have some tips on where to get the silicone and the resin? I've found quite some places, the prices differ vastly ... but all seem to be quite a tad more expensive than what i've found in .us and .uk ... once again -.-

[mangozac]

You certainly haven't chosen simple parts to reproduce! To get any acceptable results you will need a pressure pot at the very least. Actually, looking at the shapes if they are oriented in the mould the correct way then pressure casting should work quite well.

DO NOT use a cooking pressure pot for casting! They simply aren't designed for this kind of abuse and it's just asking for trouble. I've seen quite a few pictures and horror stories around the internet from people doing this! But since you already have a compressor it must be worth tracking down a pressure pot at the right price from somewhere? Perhaps look around for a secondhand one? I don't understand why a place like Germany wouldn't have something like this at a realistic price?

A hand vacuum pump will neither be fast enough or provide enough vacuum, so it would be a waste of time. Using two part split moulds, repeatedly squeezing the mould as you pour the resin in and then curing under 60PSI should give good results. It shouldn't require any particularly complex "exhaust" vents or inlets under the part. Like MD says, the parts should already have some seams and a gate attached to give you an idea of how it was cast in the first place.

There isn't a real lot of information on placing vents. Paulson does discuss is a bit in his tutorial . You've basically just got to "think like air"

[NebuK]

Heyyas,

thought you would say that about the pressure pot ;P. Only reasonable though.

So ... i've got another general horrible noob question about pressure/vac casting. After a bit more looking around i've found reasonably priced vacuum pots in the lab supply sector (exsikkatoren its in german). While they won't act as a pressure pot, i could afford such a pot and a small / cheap oil based vacuum pump. However, as far as i've understood the information here on the forum i'd really need both. Vacuum for molding with rtv silicone, and pressure for casting with resin - is that right? Or could both be done under vacuum? If so, what about those horror stories of the gasses released while the resin is curing turning to bubbles and actually foaming (i've seen pictures that looked like that "air-y" foam chocolate...) the resin under vacuum? Or is that B*llsh*t?

Thanks once again ;P.

Regards
- NebuK

PS: I'm also thinking of just building a vibration table, getting the smallest amounts of silicone and resin available and just toying around with it on some complicated but small parts ... any objections to that? I thought that if i built my mold with enough vents and a seperate pouring channel as described, let it vibrate nicely and ... whatever? Maybe it works good enough already?

[blind pig]

Why don't you get yourself a couple of kilos of some catalyst RTV silicone, some sulphur-free plasticine and a long curing polyurethane and just give it a go?

Have a look at the object you want to cast, see if it still has any mould lines still on it and clay up to that mark. if it doesn't have any mould lines, then look for the line of best fit for the mould to be separated and make a two part mould, so you will be filling resin from underneath the thickest part, with all the wispy bits of hair at the bottom of the mould, needing a fair bit of squeezing/ vibration to get the air bubbles out.

Start simple.

[mangozac]

If you're only going to do one or the other than you should go pressure only.

But Blind Pig does have a point: if you can afford to do some experimenting you might as well pick up some samples of whatever products are available to you locally and give them a try. I know some guys in the UK have had moderate success casting without pressure with a certain specific resin product that doesn't seem to bubble up as much. It won't be 100% bubble free but it might be passable for your own use.

[NebuK]

Hey,

soon ordering a small portion of both from trollfactory.de (anyone ever used thir "store brand" materials? any good?) ;P. Lets see what happens...

@mangozac: Problem is that pressure is the expensive setup here (still haven't found those pressure pots under ~600eur ~~ 790usd), so i was wondering whether vacuum only (for both, molding and casting) makes any sense ... so, does it?

Thanks again, Regards
- NebuK

[mangozac]

[NebuK]

First step: Taken!

The silicone and resin are ordered, earlier i built:
http://blog.kanojo.de/2012/03/28/quickh ... n-casting/

... lets see how it will work out ;P.

[mangozac]

Good work! Will certainly be interested to see the results! What silicone and resin products did you go for?

[blind pig]

Yeah, I hate people like you.

I used a bit of dense foam, a 1/3 sheet sander and a bread knife to make my first vibration table.

Oh,and Magnetic Duckling?

R = Room
T = Temperature
V = Vulcanisation

[Magnetic Duckling]

[Lane]

[blind pig]

[NebuK]

Heyyas,

today i've finally gathered all the ingredients i need - the clay, some hexnuts, wooden balls (for pouring "basins") and the seperation spray.

I've already started to lay out the parts and put some things i've had for channels in it. Sadly all that i had that was the right size was "drinking straws"... Not quite sure if this will work ... will it?

I've also taken some photos of the setup - i thought i'd just share it with you and wait a little bit. Maybe someone comes around the corner shouting things along the line of "NOO! NOOOOO! DON'T! WILL NOT WORK LIKE THIS! STOOOP!!" ... which would save me some problems and money ;P. Also its a nice motivation to make a nicer documentation... so, here's the pics:

http://pics.kanojo.de/resin_casting/

So ... Can it work like this? I have not full understood why smearing the clay in some kind of elevation "against" the master piece is necessary... i haven't done it properly i think, but without understanding why i doubt i *could* do it properly, so, could someone enlighten me?

Thanks for everything up till now ;P Regards
- NebuK

[NebuK]

Yes, its a panty ... The japanese sculptors seem to go quite into detail when modelling whats under the skirts of those figures, for some reason. I've never bothered with it all that much, but you need those parts to hold the figure together ;P.

The wooden pearl is a kind of basin to accomodate the resin. I've read somewhere that a small basin is good as bubble release - the small stream of resin will hit there and any air bubbles introduced by the flowing resin hitting the "solid" silicone won't be flushed into the actual parts but stay in this basin ... dunno if it works, but its not much work to try, right?

Also, thanks already for making a picture, i'm waiting eagerly ;P

Regards
- NebuK