The main reason for the failure of plastic mold is due to improper heat treatment process, such as heating temperature, holding time, cooling speed and so on. Plastic mold in the process of processing, cracks or deformation, surface oxidation and decarburization phenomenon, is mainly because the mold failure.
First of all, on the impact of oxidation and decarburization, mainly because the mold quenching is stopped at high temperature, but can not be strictly controlled. In addition, after decarburization on the surface of the die, quenching cracks are caused due to the difference of microstructure between the inner and outer layers and the larger structure stress during cooling.
The second is about the rate of heating. Because the die steel contains more carbon and alloy elements and poor thermal conductivity, the heating speed should not be too fast and should be stopped slowly to avoid deformation and cracking of the die. In order to avoid oxidation and decarburization during heating and quenching in air furnace, the heating speed should not be too fast and the diathermy should be slow.
The above will not produce large thermal stress, relatively safe. If the heating speed of the mold is fast and the diathermy is fast, the thermal stress inside and outside the mold will be very large. If the control is not good, such as deformation or crack, it is very easy to occur, in the prevention, it is necessary to use preheating or slow down the heating rate.
Due to the large size of the worktable and die, it must be able to meet the requirements of large-scale worktable and die, In addition, small diameter end mills with large elongation are often used to process the mold cavity, so chatter is easy to occur in the processing process.
In order to ensure the machining accuracy and surface quality of parts, the high-speed universal milling machine manufactured by mould must have high dynamic and static stiffness to improve the positioning accuracy, tracking accuracy and anti vibration ability of the machine tool.
High speed and high-power high-speed machining is the development direction, high-speed milling has shown great advantages in mold processing. In order to adapt to the processing of the mold cavity surface, the radius of the tool should be less than the minimum radius of the cavity surface, so as to avoid “interference” between the tool and the workpiece. Because of the small diameter of the tool, the spindle speed is required to be very high. The main shaft speed of foreign high-speed machine tools has reached 40000-100000 R / min, and the rapid feed speed can reach 30000-60000 min. The rough and finish machining of the cavity and other parts of the mold parts is often completed in one-time clamping of the workpiece, so the spindle power should be high. The spindle power of the medium-sized mold milling machine and machining center is usually 10-40kw, some even higher.
The die cavity is composed of complex six curved surfaces and grooves, and many dies have deep cavity. In order to achieve high precision, high speed and high stability machining of 3D surface, the machine tool needs multi axis linkage, and has good comprehensive cutting ability of deep hole cavity. Five axis linkage machining center can be used, in addition to the linear motion of three coordinates, there are also two rotation coordinates of feed motion. The milling head or worktable can realize continuous rotary feed by multi axis linkage, so it is suitable for machining mold parts with complex cavity surface. It can be said that compound machining is one of the development directions of mold processing.
Processing center is written language, English Name: CNC machining center; computer gong is a common saying, more in Hong Kong, Taiwan and Guangdong. In this area, milling machines are called gongs when they are in the machining center, so milling machines are also called gongs, and computer gongs are also derived from this. Computer gongs, as the name implies, are gongs controlled by computers, so they are also called CNC milling machines. In fact, they are upgraded from CNC milling machines. The original principle is the same. The difference is that the machining centers use good materials with high precision, high speed and load The traditional CNC milling machine is half cover type, and most of the machining center has been changed to full cover type, which is more safe for processing and can effectively prevent the overflow of iron chips and the splashing of chips. Computer gong is an automatic machine tool equipped with program control system. The control system can process and decode the program with control code or other symbol instructions logically, so that the machine tool can move and process parts. Also known as CNC machining mold or CNC machine tools.
The computer gong can be divided into two parts, the body part and the system part.
Fuselage part:
1) Casting, which is the most important part of computer gongs, directly affects the accuracy, stability, wear resistance and the life of machine tools. After the casting is finished, it is not immediately used in production. A good casting is that it is subjected to wind and rain, sunlight exposure, natural weathering, and some of them are soaked in sea water. After the casting does not change, the machine tool is not easy to change and can maintain the stability and accuracy of the machine tool for a long time.
2) Spindle, the spindle is used to directly face the workpiece. It is driven by the motor to rotate at a high speed. If the tool holder is installed on the spindle, the workpiece can be cut to meet various production needs. The quality of the spindle will also directly affect the machining accuracy. If the internal bearing is worn, it will easily cause the spindle to swing, and the accuracy of the processed things will naturally have a deviation of several wires 。 At present, the speed of the spindle is generally around 8000 rpm, and the high-speed machine can achieve more than 20000 revolutions. Each machine has only one spindle.
3) Screw rod is also a machine
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