A Brief Description of the Lost-Wax Casting Process
- A metal model of the jewelry is placed between sheets of unvulcanized rubber to produce a rubber mold which contains the negative impression of the metal model. This requires rubber, a mold frame, mold plates, a rubber cutting knife and blades, a timer, a vulcanizer. Use of the Shor Lok-Blok mold frame will eliminate the need for mold plates, knife and blades.
- For every casting which you desire you must produce a wax copy of the piece of jewelry If you wish to produce 10 castings of a piece, you must produce 10 wax copies of that piece of jewelry. This is done by injecting hot wax into the rubber mold that you created in step # 1.to inject this wax requires injection wax, a wax injector, parting powder or silicon and a compressed air source such as a tank of air or an air compressor. Although not absolutely required, we also recommend the use of a desiccant filter.
- The wax patterns (of many different pieces of jewelry) are assembled into "trees" and mounted in rubber sprue bases. This requires sprue bases, wax tree rods and small, low power soldering irons.
- In the late afternoon, a plaster-like material, called "investment", is mixed with water in a mixing machine. The mixing bowl with the investment is placed under a bell jar on an investment vacuum machine and the air is vacuumed out of the investment mixture. Stainless-steel flasks are placed over the waxes which are on the sprue bases, one flask per sprue base. The investment mixture which had been vacuumed is poured into the flasks, covering the waxes. The flasks are then placed in the bell jar on the vacuum pump for another vacuuming. This procedure requires flasks, investment, a mixing machine, a vacuum machine and a bell jar.
- The flasks are placed on a table for one hour to dry the investment. The flasks are put into a burnout furnace to cook overnight. A program temperature controller brings the burnout oven with the flasks through various programmed temperatures for various lengths of time, so that when you come into your factory in the morning, the flasks are ready for casting metal into them. The flasks now have cavities in the shapes of the various waxes which had previously been in the flasks. This step requires a burnout furnace and a temperature controller with thermocouple.
- Metal is melted and then cast into the flasks. The melting can be accomplished by any one of several methods. You can melt in a gas melting furnace, an electric melting furnace or a medium frequency melting furnace and then pour the metal into a casting machine. Alternatively, you can use a casting machine which melts the metal inside the machine. The melting and casting requires a melting and a casting machine (or a melting/casting machine), crucibles, flux stirring rods and tongs.
There are also two different choices in the kind of casting method that you use; vacuum or centrifugal.
- The investment is broken away from the metal by plunging the flask in water and then blasting the casting with water from a high pressure water gun (castblaster). This requires a sink, bucket or tank and it requires a castblaster.
- Finally, the pieces are cut away from the casting using a sprue cutter.