Seeking mould-making advice

[Stephen Duncan]

Hi!

Some of you saw my introduction post yesterday where I said I'm completely new to sculpting, well I'm seeking advice on the best method of containing the silicone fluid when creating the mould. I've been following this series of videos on Youtube where the guy uses Lego - it looks like a really good, practical way of working:



Problem is, and to my surprise, Lego is actually really expensive but at least it's re-usable unlike any of the other methods I've come across.

Would anyone like to share their own approach to this?

Thanks!

 

[Fantasy Realms]

Foam card and a hot glue gun mate, that's the way to go. well that's what I use anyway lol

http://www.hobbycraft.co.uk/west-design-a2-white-foam-board/574236-1001

 

[ellie]

Plastic card will do the job very well. much easier to put together and I think a much better result.

Ian

www.elliesminiatures.com

 

[Stephen Duncan]

Ah cool, that's really cheap stuff as well. I'll have to check out the glue guns and go from there. Cheers!

 

[valiant]

Old vinyl floor covering and parcel/gaffer tape!

 

[Stephen Duncan]

Thanks for the advice fellows.

Another question though - vacuum chambers. Are they worthwhile?

 

[Fantasy Realms]

How often do you see yourself using it?

 

[Stephen Duncan]

Good question, at the moment it's difficult to say because it depends on how successful my project is. I guess at the moment I'm just planning in advance for all possibilities. I don't think I'll be rushing out to get one any time soon...

 

[Fantasy Realms]

they're a useful bit of kit but only worthwhile if it doesn't end up gathering dust lol

 

[Stephen Duncan]

Yeah, that sounds a little too familiar to so many of my previous purchases lol

 

[Tommi]

Corrugated cardboard held together with sticky tape and sealed round the bottom with hot glue, cheap and throw away. Here are a few I made last week and the result once removed from the card.

I use 2x large vacuum chambers and pumps and a pressure chamber. Mine are used every day.

Cheers
Tommi

 

[Uruk-Hai]

Thanks for the pictures, Tommi! Its inspiring and gives at least me some new ideas and takes.

I assume that you cut the moulds at least in one end to get the original and casting out. How do you plan where the cut is to be made? And for how many cast does one mold usually be used? For larger production runs I assume you have several molds for the same part?

Lego is not that expensive when bought at E-bay. Especially if you dont worry about difference in colour.

Cheers
Janne Nilsson

 

[ellie]

Hi Tommi

You just summed things up with the photos mate. Their are a few companies that do the equipment it can be expensive if you are not going to use it that often. but well worth it if you want a first class reproduction. Or you could contact people like Tommi if you don't want to cast yourself and just test things out with your product. it could be the cheaper way of doing it in the short term then if things work out then take the plunge into buying the equipment.

Just my thoughts cheers

Ian

www.elliesminiatures.com

 

[Stephen Duncan]

Whoa Tommy, your studio is like a scene from Breaking Bad, especially with the blue silicone! Thanks for the photos, they really do convey the message that simple cardboard is sufficient.

I've ordered a glue gun, it's on it's way in the post now, and I also bought a few foam boards. Even though the foam boards are cheap I think I'll just stick with cardboard in future though. Tommi very much sold that idea with his photos!

I assume that you cut the moulds at least in one end to get the original and casting out. How do you plan where the cut is to be made? And for how many cast does one mold usually be used? For larger production runs I assume you have several molds for the same part?

-Janne Nilsson

This video might cover part of your question:

 

[Tommi]

I gave up with lego a long time ago as it leaves the outside of the walls quite messy where the silicone runs between the gaps, also quite time cosuming. I found using cardboard quite easy to use, measure it score it with a sharp knife to make nice clean corners when folded then fix joint with sticky tape. I find using card with a gloss surface makes it easier to remove once the rubber has reached its optimal hardness although you will still need a good spray release agent to spray the inside of the mold and master before pouring the rubber.

When producing a large order I normally run two or three moulds depending on scale and quantity etc. It helps move things along quite well especially doing all those small delicate parts.

It is advisable to draw a cut line down one side of the figure or part before putting it through the moulding process, this will be your guide line for cutting once the mould has cured, special care and attention will need to be given to this as if you get it wrong you could end up with a nasty seam line or seam line in an awkward place.

I cut my moulds with a set of special knife blades which cut a snap lock fitting which gives excellent registration of the cut line and eliminates offset casts and major seam lines. Mould life is dependant on many factors, scale of figure and ease of removal from mould, undercuts and quality of the rubber used as it reacts with the heat of the rubber and over time goes brittle and breaks down, I like to try and cast everything asap in one run if I can to get the best out of the moulds.

There is quite and art and science to this procedure and lots of lessons to be learnt as you go along but if you get it right you can produce some very pleasing results.


Cheers
Tommi

 

[Tommi]

More moulds to be made after the weekend and can do an SBS if there is any interest.

Tommi

 

[Colin_Fraser]

I am very interested Tommi. I have used alumelite once or twice and found it gery finicky.

Colin

 

[Uruk-Hai]

Love to see your process and tricks. And thanks for whats already have been shown.
Do you use release agent for the cast as well?
Are the figures broken up already when you get them or do you have to that as well? Perhaps some hard to cast parts?

Cheers
Janne Nilsson

 

[Tommi]

Yes Janne I always spray the moulds with release agent for every cast otherwise it starts to stick once the resin get warm and starts to pull bits out of the mould. All figures so far come in kit form and careful thought is given to spuing up the smaller parts ready for casting so that the resin flows into all those awkward places.

Tommi

 

[garyhiggins]

Hi Stephen, my moulding process is different than that used by most of the guys on here in that I generally cast in metal. The moulding rubber for hot casting has to take a temperature of 300 degrees celsius and so sets with a far greater stiffness than a rubber designed for resin casting. Unfortunately, it also has a much weaker tear strength so you can get away with almost nothing regarding undercuts. To get round this problem, I design my figures to cast in a lot more parts than would be usual with resin casts, and where necessary I make my moulds in multiple parts. A good rule of thumb is anywhere that is likely to tear away, (shoulder/ head sockets, body joints etc.) make a separate insert. This means that I have to plan my moulds at the sculpting-engineering stage. When making my moulds I have to (inserts notwithstanding) embed my master halfway in soft wax, pour half the mould, then turn over the mould box, CAREFULLY remove the embedding wax, then pour the second half of the mould.
There are a few things to take note of with moulds for metal casting. Your pouring chamber (sprew) needs to be at least as deep as the depth of the cast to really get that metal in there fast. When cutting your air escape channels, don't forget that you can drill air channels to the back of the mould as well as the edge. for a release agent you can use a mix of vasseline and three in one oil.
For mould boxes i use balsa wood and to make sure the rubber doesn't stick I paint the inside with release agent. Since I need to make my moulds much longer than the master, I tend to make my moulds trapezius shaped rather than rectangular as I see no reason to waste the extra rubber doing nothing.
When your moulds are made, leave them for a few days to fully "post cure" before using them.
if you are in the UK, send to either Alec Tiranti Ltd. or Sylmasta for a catalogue.
Hope some of this helps, best wishes, Gary.