Day 35 Mold Injection

 Wax Injection Header

Eventually, if you make jewelry long enough, you will find that you make some of the same things over and over, either multiple parts on the same design or the design multiple times. You say to yourself….”Self, it would be so nice if I could make it once and have a way to reproduce it”. Whether you do your own casting or have someone do your casting for you, it is beneficial to have a mold made so all you have to do is inject the wax and cast the piece, sometimes multiple times.

I will cover making a mold at a later date, but today let’s look at the wax injection process. Here is a piece I needed multiples of, so I made a model, added a sprue and a sprue button, and made a mold.

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Here is the mold I will be using, notice when I cut the mold, I cut it with “locks” in it so the 2 halves won’t shift and the mold line will be less visible and less cleanup in the wax. I cut the mold with a #12 Surgical Blade in a Scalpel Handle. I used Castaldo Gold Ready Cut Rubber in this instance.

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I also cut airlines in the mold so the air can evacuate and helps the waxes fill more easily. I lightly coat the airlines with talc (Baby Powder) to help in this process. I fill a towel with baby powder and tap the inside of the mold while spreading the mold open. I also use a Makeup Brush to brush out any excess powder. An air hose blown into the mold will do the same thing.

Wax Injection (5) Wax Injection (6)

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After the airlines are powdered, spray a little Mold Release to the inside of the mold to help the wax come out of the mold easier. To inject the wax, I have made 2 Aluminum Plates that I use to hold the mold at a constant pressure so the mold doesn’t bulge or have inconsistent thicknesses. The aluminum plates are about 1.5mm thick.

Wax Injection (10)

Wax Injection (9) Wax Injection (11)

Now set the air pressure on your Wax Injection Machine, I like to start around 10psi. Hold the mold to the injection nozzle, press in and count to about 10 (one thousand one, one thousand two, etc.) Wait for a couple of minutes for the wax to cool, and open the mold. If the wax doesn’t fill, add more pressure, and if it overfills, (flashing), decrease the air pressure. Remove and repeat. Re-powder the mold about every 20-30 injections and spray the mold release about every 5 or so injections.

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I hope you had a great 4th of July!

Now go enjoy your jewelry making.

Doug

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2 Responses to Day 35 Mold Injection

  1. Jason September 18, 2014 at 6:42 pm #

    Could you please go into more detail in regards to your use of “airlines” — good places to put them? angles? relative size?
    Thanks for sharing your knowledge!
    Jason

    • JewelryMonk September 19, 2014 at 9:23 am #

      Jason, thanks for the question. I like to use as few airlines as possible for the piece, but some pieces need a lot. A good thing to do is put yourself mentally it the mold….. weird? OK follow me. As the wax is injected into the mold, it is fighting against the air that is in the mold. The wax is pressing on this air and making back pressure, fighting against the wax. you can bump up the pressure on the wax pot, but that will usually cause flashing, or wax in the area where the mold is cut. So I like to start with about 4-6 airlines in each half of the mold, one on each side at about the 90 degree area, one on each side at 45 degrees, and one straight on top, opposite the gate or sprue. I cut these about 2-3mm deep, from the edge of the piece of jewelry, and about an inch long, or almost to the edge of the mold. On larger pieces, I will cut deeper and all the way to the edge, since there is more air to release. I also try and put the cuts in a place where there is easy access to clean up the wax, because anytime you make an airline, you are making a defect in the wax, ever so small. You will also want to add small airlines to the ends of prongs. I add a little unscented baby powder to the inside of the airlines (just a small amount) and spray the mold halves with mold release. Inject the waxes and inspect them. If there are areas that aren’t filling, ad an airline there.
      Hope this helps, good luck.
      Doug