Butiran Produk
The essence of high pressure die casting is a method of filling the die-casting mold (die-casting mold) cavity with liquid or semi-liquid metal at a high speed under the action of high pressure, and forming and solidifying under pressure to obtain castings.
At present, the general die-casting island will consider the following configuration: the die-casting machine is equipped with vacuum, the holding furnace is equipped with a quantitative casting system, and the spraying system is adapted to the product to shorten the spraying time. The pick-up robot completes the pick-up, removal of slag bags, and printing. The die-casting island can also be upgraded to automatic cleaning when the product volume is relatively large.
CAE analysis is increasingly used in the die casting industry, represented by PROCAST, MAGMA, FLOW-3D, etc. Simulation: Based on the calculation results of filling flow, velocity distribution, etc., we can accurately predict defects such as air entrainment, inclusions, and poor filling, which greatly improves the yield rate and saves a very objective cost. It is a very useful tool to quickly and scientifically design the entire casting system (gate, runner, overflow tank, etc.) of the die-casting mold. Optimize the process parameters of the casting process, reduce the number of product mold trials, reduce casting costs, and improve product quality. Use CAE software to generally analyze filling, solidification, pore distribution and velocity distribution reports.
With the continuous improvement of product quality requirements, the use of vacuuming to solve the problems of filling and air tightness of castings has been well developed. Vacuuming generally uses vacuum valves. The most commonly used vacuum valves have the following two structures. Figure 3 is the schematic diagram of the vacuum valve. Just like the ordinary die-casting process, after the molten aluminum enters the pressure chamber, vacuuming starts. Then when the die-casting machine starts at high speed, the kinetic energy of the molten aluminum is relied on to touch the spring leaf of the vacuum valve. When using a mechanical vacuum valve, it should generally be closed when preheating the mold. After preheating is completed, high speed and boost can be started before the vacuum valve can be used. Mechanical vacuum valves are simple to use, but the processing accuracy of vacuum valves is high, and the cost of vacuum valves is relatively high. Figure 4 is the schematic diagram of the hydraulic vacuum valve. The principle is the same as that of the mechanical vacuum valve. When the punch starts to start, vacuuming begins, but the principle of closing the vacuum valve is different. The hydraulic vacuum valve generally starts to operate at a high speed, and at the same time the model number is issued to the hydraulic system of the vacuum valve, and the vacuum valve closes. The cost of the hydraulic vacuum valve is relatively low, but the die-casting process parameters and mold design must match, otherwise aluminum water will be die-cast into the vacuum valve and cause blockage.
Application of new technologies in die-casting machines
High vacuum die-casting technology
At present, imported die-casting machines are represented by Bühler and Fulai, and the two die-casting machine suppliers have their specialties in high vacuum applications; Bühler's high vacuum technology is mainly designed to evacuate the pressure chamber and the mold back plate. The interface facilitates the extraction of air from the pressure chamber, and the vacuum on the back plate of the mold is conducive to more thorough vacuuming of the cavity. Fulai's high vacuum technology directly seals the entire pressure chamber. A pipe is designed at the bottom of the pressure chamber to be directly inserted into the holding furnace to complete the sealing of the mold. The cavity is evacuated to create negative pressure to remove the aluminum in the holding furnace. The liquid is sucked into the pressure chamber and then die-casted. The biggest advantage of this technology is that it avoids oxidation and slag inclusions during the contact process between aluminum water and air, and can perform T6 heat treatment. It has already mass-produced structural parts for automobiles in Europe.
Improving production efficiency and reducing manufacturing costs is the goal of every manufacturing company. The international definition of OEE is: OEE is the abbreviation of overall Equipment Effectiveness. It consists of three key elements: availability, performance and quality index, namely: OEE=availability X performance X quality index. For die casting, mold exchange is one of the six major losses. Rapid mold change has become the goal pursued by lean production. Mold exchange can generally be defined as the time from the last qualified product to the next mold to the die-casting machine to produce the first qualified product; in Japan, for 800-ton cold chamber die-casting For machines, the general mold exchange time is 10-20 minutes; in China, the mold exchange time is relatively long, and it is common to exceed 10 hours. In addition to mold exchange being related to schedule management, work standardization, and tool management, the evaluation of whether the conditions for mold exchange are met are roughly as follows:
- (d) Whether the core-pulling cylinder can be quickly linked
At present, aluminum alloy die-casting products are mainly divided into three categories according to quantity. The first category is engine transmission housings, cylinder blocks, etc. represented by automobiles, motorcycles, and general engine engines. The second category is network communications. Representative base station shells, filter shells, and the third category are car body structural parts with higher mechanical performance requirements. As shown in the figure, it is a typical aluminum alloy die-casting product:
Aluminum alloy has excellent electrical conductivity due to its high specific strength and good corrosion resistance. In the social environment of energy conservation, emission reduction, and green environmental protection, aluminum alloy die-casting is developing rapidly in China. It is believed that in the near future, aluminum alloy products will be more abundant and diversified.
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