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Castng arms

Questions and discussion of tools, materials and techniques.

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Castng arms

Postby amphoterik » Wed Mar 02, 2011 1:56 am

Hello again everyone, been a while since I have posted. Anyway, things have been going smoothly with my molding and casting, until recently. I have hit a snag with arms. I am molded some custom arms (think arms with swords) and I am having a heck of a time molding it. I tried a split mold, but I can never seem to get my cut right since the arm has bends and angles in it. Have you ever cast arms and if so, how did you do it most successfully?
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Re: Castng arms

Postby mangozac » Wed Mar 02, 2011 6:45 am

This kind of thing is a bit hard to describe without pictures, but I realise that the kind of project lends itself to not being able to post pictures here.

I wouldn't think it much more different than usual - which plane are you doing the cut through? Cutting parallel to where the shoulder would mount to the body or perpendicular?
Oh yeah I can make that....
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Re: Castng arms

Postby Duckster » Wed Mar 02, 2011 7:34 am

Ahoy ~

I have only just recently found the awesome that is the split mold ~ I am by no means an expert by at it by any stretch of the imagination, but i will try to offer some insight that I have learned by my last few molds.

the "Duckster connect the dots method"

When i do a split mold, I make sure I put in my vents and gate before I even pour rubber - I use the smallest amount of super glue and put the vent right onto the master and then angle it in my hands to check and see how I should position it on the bottom of the mold box.

I try to line up my vents so that I can "almost" cut a straight line between vents and come up hitting the middle points of the master underneath.

so - Lets say I have an arm that has 1 gate, 1 vent - at the shoulder and the tip of the sword respectively - If I had an odd-angled elbow in there that I was having real issue with - I would put another vent rod coming out of the elbow - Even if you do not need it for venting.

What this does is, It gives you a "Connect-the-Dots" effect on the top part of the mould - Remove the clay that you used to enlarge the gate and tips of the vents and you have little 1/16th plasticard rods sticking out.

By using the connect the dots, I start at the outside wall of the mold - And cut all the way in to the "Gate" - Normally I use 1/8th to 1/4 inch Square rod to denote my gates and 1/16th or 1/8th to denote vents.

Once I hit the gate, I remove it completely - as well as pulling out the vents, that way they do not get in the way of the knife - You dont want to slip around a gate or vent, but rather cut straight through the cavity that they leave behind when you remove them.

using another person is best, but with practice and a sharp blade you spread the rubber as far as it will go and just connect the dots slowly - I am still working on this part of it, It helps a lot to have something to compare it to - Take a picture of the master with the gates on it upside down so that you know where you are going next with the knife.


Hope my info is helpful at all, describing these sorts of things is hard, I never take pictures of anything pretty much ~ who wants to wait to try out that new mold ? Not me, im so excited to try a new mold that im pouring resin in sometimes before i pull the master out !
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