Mold Making Guide - Part 1
Last Updated (Thursday, 11 March 2010 12:50)
I've decided to put together a basic "how-to" guide that covers silicone rubber mold making and plastic resin molding and casting . I learned quite a bit over the last 5 years while building my B9 Robot and more than more while building my Twilight Zone Mystic Seer. Hopefully you will pick up a few tips here that will help you avoid some of the pitfalls.
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If you're going to get semi serious in molding, you'll want a vacuum pump. I picked one up on eBay for about $100. It's an industrial pump and is very rugged. You may want to buy one of the smaller hobby vacuum pumps available, but I went for the commercial one as it should last me longer, and it actually cost less. You want one that can pull 29 "inches of mercury" for a complete vacuum. |
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First, a few things you'll need. Get yourself a good 100 piece basic set of LEGOS. Yes, I said LEGOS! If you're lucky you have a son that went through the LEGOS phase. If you're like me, you may still have yours from when you were young. Either way, they are a must if you want to quickly make molds of various sizes. You want a set with just the basic pieces and none of the fancy special pieces. |
Mold Making Guide - Part 2
Last Updated (Thursday, 11 March 2010 12:51)
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Prepare you original - If you are reproducing a part or existing object you have, clean it well. The item can not be porous or it will get stuck in the mold. You may have to use a sealer on the surface.
Choose your parting line carefully. You need to decide where your parting line will be. That is where the two halves of the mold will separate. Look for undercuts in your part that will prevent you mold from coming apart. Knowing that you may have a seam visible on your finished part will also help you decide where it should be. Try to line it up with a straight or flat side of you part if you have one. Also make note of the original part's seam, if there is one. Try to match your seam to the original one, if you can. |
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Build your molding box - I use my son's LEGOS to make the molding box. It's quick and cheap. You can adjust the size to fit you project. Now if you are molding something of size, say bigger than a softball, you may want to build a wood or metal mold box. For smaller hobbyist type of molding, the LEGOS are sufficient. |
Mold Making Guide - Part 3
Last Updated (Thursday, 11 March 2010 12:52)
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Measuring your Silicone Rubber - The silicone rubber I use has a ratio of 10:1, rubber to catalyst. Use the postal scale to get an accurate measurement. I put the empty container (plastic cup) on the scale first and zero it out. Then add the silicone rubber. |
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Once the scale has settled , add catalyst equal to 10% of the weight of the rubber. I then mix it thoroughly using a popsicle stick and transfer it to a larger container before the degassing step. |
