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Cheap Castings

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  • Member since
    April 2007
  • From: Amarillo, TX.
Cheap Castings
Posted by captfue on Tuesday, January 25, 2011 9:34 PM

Anyone who has spent anytime building models be it auto to armorer has needed to produce a part. The most common way to do this is with resin poured in to mold. The drawback is the expense of this process. The system shown here is very inexpensive and within the abilities of most modelers.

A quick note on safety

This method requires heating plastic to about 400F be sure to work with gloves and work in a well ventilated area.

The above picture is my master ( a 1/35th scale American WW2 Helmut with goggles) mounted on a base. The Helmut is a cast of an original I did and the goggles are from the spare parts box. This could be almost any part you'd like to copy.

This next picture shows the basic items needed to create a mold, they are a tube of 100% silicone rubber $5.00, a used paint brush, a paper cup, plastic spatula and a can of non stick spray cooking oil about $1.00.

The next step is to spray some of the non-stick cooking oil into the paper cup. Then with the old brush, completely coat the object and base, then squeeze a portion of silicone onto the base

With the spatula,coated in cooking oil, begin to press the silicone up and around the item. Ensure that the whole piece is covered by a 1/4in to 1/2 in layer of silicone. Something to remember is that the current top of the mold will become the bottom when being cast. I like to keep the top flat and make the mold rectangular. This helps me orient future cuts.

After the silicone has been left to cure for at least 24hrs, longer for larger molds, carefully separate the mold from the base. This was done with a #11 exacto blade.

Next I"m making two cuts so I can remove my original piece.

Here is the hollow mold, and the original Helmut.

After you have your mold begins the process of making duplicates. Pictured above are the items needed to do this they are: A toaster oven, as low as $10.00 even less at thrift stores. sprue cut with wire cutters into 1/4in lengths, a drill bit for press soften plastic into the mold. and a glove to protect from heat.

Heat the oven to about 400F, with the know upside down mold place a piece of sprue into the empty cavity.Place inside the oven and let heat for 15minutes.
As you can see my oven has taken a beating over the last three years. At 400F plastic will only become soft an ply able it will not catch on fire, even so never leave your work unattended.
I'm lucky my oven only cooks for 15minutes at a time. So I know when to remove the mold, at this point using the blunt end of the drill bit press the soften plastic into the mold, add another piece of sprue. Reheat again. The size of the object determines how many times to repeat the process.  At the left hand side of the oven tray is another mold it's a two piece mold of a basic 1/24th figure. During the time I cast these Helmut's I also cast three figure mannequins a couple of rifles two sets of arms, four heads and numerous other odds and ends.

This last shot is of three Helmut's I cast.
Just to be clear This is not a commercial quality cast and they need lots of work to become usable. For me the cheapness of the casts far out weight the time needed to clean the pieces up. Plastic is a very forgiving medium, in that if it comes out messed up it can be reused, also you are not limited to Sprue (although it's the best) I,ve used plastic forks, desirable razors, computer plastic ect.....

anyway hope you get something out of this.

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