Lost-wax casting is one of the glass processing and forming methods. The main process is to heat the glass to a high temperature to make it fluid and flow into a pre-made mold shell to form. Since the mold shell is made by removing the wax mold after heating, it is called lost wax casting. Because lead oxide-containing glass (commonly known as artificial crystal) has a diamond-like high refractive index and high fluidity at high temperatures, artificial crystal is often used for casting glass. In the Chinese market, the above-mentioned lost-wax cast lead crystal glass products are generally called glaze. The lost-wax casting method can produce complex and exquisite handicrafts.  

Lost wax casting method: The lost wax casting process is developed from the ancient casting process. In the late Neolithic Age more than 5,000 years ago, ancient Chinese craftsmen widely used the lost wax casting process in the manufacture of bronze ware. According to the characteristics of beeswax's plasticity and thermal volatility, the craftsmen at that time first carved the beeswax into a wax mold of the desired shape, then wrapped clay and reserved a small hole outside the wax mold, and baked it after drying to make the wax mold vaporize and volatilize. At the same time, the clay becomes a ceramic shell, and the inner wall of the shell leaves a negative mold of the wax mold. At this time, the molten metal is injected into the shell along the small hole, and the shell is broken after cooling to obtain the required metal billet. The basic principles of modern lost-wax casting techniques are the same, but more sophisticated. This is mainly reflected in the stricter requirements for the precise shape and position of the wax model. The acquisition of wax mold in modern technology is not only the direct engraving of wax, but also the negative mold can be obtained by molding the metal original mold (plate) with silicone, and then the wax mold can be obtained by injecting wax from the silicone negative mold. The casting material is no longer clay, but cast plaster instead. Such products are much finer than ancient castings.

Process

The process flow of dewaxing casting is: mold design - mold opening - wax injection (mold) - trimming wax mold (welding wax mold) - wax tree planting (- weighing) - making shell mold ——Shell mold roasting——casting——vibration shell——cleaning sand treatment

Each process is described below.

Making product molds

Generally, the molds are aluminum molds and steel molds. However, it is inconvenient to use. The factory gets the drawings and the engineering department designs the corresponding molds and gates according to the drawings. Then, the aluminum material is processed by a series of CNC machine tools to manufacture the mold.

After the mold is opened, the wax injection operation can be performed. The wax injection operation should pay attention to factors such as wax temperature, pressure and compression of the plastic mold.

The wax used to make the wax model is generally blue model paraffin, its melting temperature is about 60℃, and the wax injection temperature is about 65℃. There are also some other colors of paraffin with slightly different properties. The wax temperature and injection pressure are determined by the wax injection machine. There are usually two types of wax injection machines: air pressure type and vacuum type. The wax injection principle of these two types of wax injection machines is basically similar, that is, the molten wax is injected into the plastic mold by air pressure. The difference between the two is that the vacuum wax injection machine can first vacuum the plastic mold and inject wax into the plastic mold; while the air pressure wax injection machine can only directly inject wax into the plastic mold. Therefore, it is usually easier to master the vacuum type wax injection machine, while the air pressure type wax injection machine requires certain experience.