Wax injection process of dewaxing casting
What are the steps of wax injection process in dewaxing casting? Die casting dewaxing casting is one of the glass manufacturing processes. The main process is to heat the glass to a high temperature and flow into the preform mold. Because the mold shell is obtained by taking out the wax mold after heating, it is called dewaxing casting.
After the mold is opened, wax injection can be carried out. Factors such as wax temperature, pressure and mold compression should be paid attention to in wax filling operation.
After the wax model is taken out, it should be carefully checked. If there are serious problems such as missing edges and broken feet, this wax model is a waste product. Wax pattern repair shall be carried out for some minor defects.
The wax used for making wax models with blue wax is generally around 60 ℃, and the wax injection temperature is around 65 ℃. There are also some paraffin wax of other colors with slightly different properties. Wax temperature and wax injection pressure are determined by wax injection machine. Wax injection machines are generally divided into pneumatic and vacuum types.
The pressure in the wax cylinder of the wax injection machine is usually provided by an external air pump, which should be kept between 0.5 and 0.7at (or kgf / cm2), that is, 0.051 and 0.071bar. It can also be adjusted according to the volume and complexity of the wax model.
Before waxing, open the plastic mold and check whether the plastic mold is complete and clean. If plastic molds have been used, dewaxing agent (or a small amount of talc powder) should be sprayed on the plastic molds, especially on thin and complex parts, so as to facilitate dewaxing molds; Secondly, preheat the wax injection machine, turn on the air pump, adjust the pressure and temperature, and conduct precision casting.
During wax injection, the plywood (which can be plexiglass, wood, aluminum, etc.) shall be clamped by hand. Pay attention to the distribution of fingers to make the rubber mold press evenly; Don't move your hand behind your mouth, gently step on the wax injection switch with your foot and release it immediately. After holding your hands for 1-2 seconds, put the plastic mold in, then open the plastic mold (if the plastic mold has a bottom, pull out the bottom of the mold first), and take out the wax mold.
The wax injection principle of the two types of wax injection machines is basically the same, that is, the melted wax is injected into the plastic mold by using air pressure. The difference is that the vacuum wax injection machine can first vacuum the plastic mold and then inject wax into the plastic mold, while the pneumatic wax injection machine can only directly inject wax into the plastic mold. Therefore, in general, the operation of vacuum wax injection machine is relatively easy to master, while the pneumatic wax injection machine needs some experience in precision casting.
The heater and temperature sensing device used on the waxing machine can reach and maintain a certain temperature. In general, the wax temperature of the wax injection machine should be kept at 70 ~ 75 ℃, so as to ensure the fluidity of the wax liquid. The temperature is too low, and the wax liquid is not easy to be injected into the wax mold, resulting in incomplete wax mold; On the contrary, if the temperature of the wax liquid is too high, it will cause the wax liquid to overflow from the gap of the plastic mold or the wax injection port, and it is easy to form a flash. Or burn your fingers.