Low pressure casting concept Low-pressure casting means that the casting mold is generally placed above a sealed holding furnace containing alloy liquid. Compressed air is introduced into the holding furnace to cause a low pressure (conventional 500-2500 mbar) on the surface of the molten metal, so that the liquid metal is connected by the furnace A riser tube inside the metal and mold cavity rises to fill the mold and controls the method of solidification casting. This casting method is well packed, the castings are densely organized, and it is easy to cast large and thin-walled complex castings. Generally, no riser is required, and the metal recovery rate is high (generally more than 70%). Easy to automate. Compared with high pressure casting, the equipment cost is lower, but the production efficiency is lower. Compared with gravity casting, it is generally used to cast nonferrous alloys. Low-pressure casting features Low-pressure casting can use sand, metal, graphite, gypsum, etc. 1) Filling with pure metal liquid improves the purity of castings. Because the slag generally floats on the surface of the molten metal, and low-pressure casting is realized by the molten metal in the lower part of the holding furnace through the riser tube, effectively avoiding the possibility of the slag entering the mold cavity. However, the dross caused by repeated scouring inside the riser tube requires precautions, and a filter screen is generally placed during the casting process. 2) The pressurized pressure curve is adjustable. If the setting is reasonable, the filling of the liquid metal is stable, which reduces or avoids the phenomenon of tumbling, impact, and splashing of the liquid metal during filling, thereby reducing the formation of oxidized slag. 3) The moldability of the casting is good, and the filling of the molten metal under pressure can improve the fluidity of the molten metal, which is beneficial to the formation of castings with clear outline and smooth surface, and is more beneficial to the molding of large thin-walled castings. 4) The casting is crystallized and solidified under the action of pressure, which can be fully compensated and the casting structure is dense. 5) The recovery rate of the molten metal is improved. In general, no riser is needed, and the uncondensed metal in the riser can be returned to the crucible for repeated use, which greatly improves the recovery rate of the molten metal. Generally up to more than 70%. 6) The production operation is convenient, the labor conditions are good, the production efficiency is high, and it is easy to realize mechanization and automation. With the improvement of intelligence and automation technology, an automated casting line with one person, multiple machines or unmanned operation can be realized. Low-pressure casting plus common alloys Aluminum alloy, magnesium alloy, copper alloy, etc. Low-pressure casting conventional casting types Wheels of vehicles such as automobiles, motorcycle...

Die casting, also known as high-pressure casting, is a near-net-shaping technology that has been widely used in the automotive, aerospace, and electronics industries in recent years. During the die-casting process, molten metal (generally light alloy) fills the cavity with high pressure and high speed under the action of the punch, and quickly cools to form the final casting. Die-casting is generally divided into cold-chamber die-casting and hot-chamber die-casting. Cold-chamber die-casting is mainly used for the production of large parts, such as automotive parts and communication base station cooling parts. Hot-chamber die-casting is widely used in the production of small electronic or 3C products. Process, such as USB connector, notebook shell, etc. 1. Die casting has a good automation foundation Compared with the ordinary casting process, die casting is characterized by high speed and high pressure. The products produced are generally light alloy thin-walled parts, but die casting technology is also used in the production of pure copper rotors. Unlike aluminum and magnesium alloys, pure copper The melting point is very high, so short die life during pure copper die casting is a big problem. Among all casting technologies, die casting has the highest degree of automation. Modern die-casting companies use automated die-casting island technology, which highly integrates die-casting machines (generally dozens or even hundreds) to form a fully automated production process. At the same time, using intelligent factory technology, the production process of the die casting machine is monitored, the performance and status of each die casting machine are grasped in real time, and the production process of the die casting machine is adjusted in time through big data measurement and real-time feedback to ensure Final product quality. The real-time control of die casting mold temperature is a simple example: Taking cold chamber die-casting as an example, in the production process, due to the continuous filling of the mold cavity with high-temperature liquid metal, the mold temperature continues to increase. At this time, in order to ensure that the temperature of the mold is not overheated, cooling water is generally used to cool the mold. If the design of the cooling water piping is reasonable, in general, we can ensure that the temperature of the mold reaches the so-called thermal balance by controlling the temperature and flow rate of the cooling water. From this point of view, we can design the cooling water feedback system. After we know the actual value of the mold temperature, we can control the temperature and flow rate of the cooling water through calculation and immediate feedback system, and finally we can control the temperature of the mold. This is a typical application of a smart factory for die casting at this stage. In fact, the above case of intelligent control is just a very small application scenario in the "smart factory". To achieve a ...

In the process of high pressure casting of aluminum alloy, if the injection speed is too high in the low speed stage, on the one hand, a lot of air will enter the mold cavity through the pressure chamber, on the other hand, the aluminum liquid will billow in the pressure chamber, resulting in the increase of the air content of the aluminum liquid, thus affecting the quality of the die casting. If the injection speed is too low, the casting will be cold insulation and bad forming.The specific requirements of low speed are in the low speed interval (0.1-0.5 m/s), uniform or uniform acceleration to gently promote the metal molten liquid, to avoid the metal liquid to produce turbulence and dissolve into the gas, so as to reduce the gas content of the metal liquid, but also make the gas in the mold cavity easy to discharge smoothly. Generally, the injection velocity of this stage is relatively low, generally within 0.1-0.5 m/s. At present, the general calculation formula of low speed can not be directly analyzed from the filling forming effect, resulting in a large deviation of the calculated results. The production personnel only depend on the experience and the repeated debugging to determine the speed parameters in the low-speed stage, which on the one hand causes the process instability and a large number of trial production wastes, on the other hand prolongs the development cycle. Longhua die casting machine co., LTD. Has 38 years of experience in die casting machine production, and cooperated with hefei institute of Chinese academy of sciences to develop the latest and most scientific die casting machine production technology, which can completely solve the problems of die casting such as pores, sand holes and so on, and greatly improve the quality and precision of casting. Longhua die casting machine co., LTD., a professional die casting machine manufacturers, die casting technical experts.

  Today, Longhua Technology will share with you the basic structure and working principle of natural gas compressors. 1.Basic structure  Natural gas compressors are reciprocating piston compressors, which are mainly composed of three parts: moving mechanism (crankshaft, bearing, connecting rod, crosshead, pulley or coupling, etc.), working mechanism (cylinder, piston, valve, etc.) and Body. There are also three auxiliary systems, namely the lubrication system, the cooling system and Regulation system.   Movement mechanism: including crankshaft, connecting rod, crosshead, piston rod, etc. The motion mechanism is a crank-link mechanism that changes the rotational movement of the crankshaft into a reciprocating motion of the crosshead. Usually, the driving machine drives the crankshaft to rotate through a coupling or a flywheel (belt pulley). The crankshaft is connected to the large end of the connecting rod, and the small end of the connecting rod is connected to the crosshead. The crosshead is limited to the body slide and can only perform reciprocating motion.   Working mechanism: Including cylinder, piston, air valve, etc. The working mechanism is the main component to realize the working principle of the compressor. The cylinder is generally in the shape of a barrel, and there are several inlet and exhaust valves at both ends. The body is used to support and install the entire movement mechanism and working mechanism, and it is also used as a lubricating oil tank. The crankshaft is supported on the body by a bearing. The slide on the body supports the crosshead. The cylinders are fixed on the two arms of the body. . 2. Working principle   The reciprocating compressor uses a crank and linkage mechanism to change the rotary motion of the driver into the reciprocating motion of the piston. The cylinder and the piston together form a working chamber to achieve gas compression. The piston reciprocates in the cylinder to allow the gas to complete the air intake in the cylinder. , Compression, exhaust, etc. The intake and exhaust valves are used to control the gas entering and exiting the cylinder, and the pressure of the gas is increased during the compression process, thereby achieving the purpose of pressurizing the gas.

Release agent has been widely used in die casting production. It is an important part of mold cooling. It has important applications in the fields of metal die casting and vacuum foamed sheet, which can effectively extend the service life of the mold. Next, Longhua Die Casting Machine will introduce the concept, application characteristics and use of release agent. Overview of release agents 1. Definition and role of release agent 1. Definition: Release agent is an interface coating used on the surfaces of two objects that are easy to adhere to each other. 2, role: to form a layer of inert coating between the mold and the mold, so that the mold can be easily removed from the mold, improve the wear resistance and scratch resistance of the final product, it can make the surface of the object easily detached, Smooth and clean. Second, the principle of release agent       Since the lubricant substance (release agent) is easy to adhere to the metal surface (mold surface), a static lubricant film layer is formed due to adsorption, thereby reducing the friction between the polymer (mold) and the processing equipment (mold) , Produces a significant film release effect and improve the surface finish of plastic parts. Classification of release agents 1. Classified by adding method / usage: internal release agent and external release agent. The former is directly added to the molding plastic; the latter is coated on the surface of the cavity of the mold. 2. Classified by chemical composition: inorganic, organic and polymer. (1) Inorganic release agent (2) Organic release agent (3) Polymer release agent 3. Classified by function / application: Metal demolding: die-cast aluminum (magnesium, zinc), casting, forging, etc .; and rubber, fiberglass, plastic, polyurethane, concrete. 4, classified by shape: powder, liquid and emulsion (can be atomized). 5. Classified by service life: conventional release agent, semi-permanent release agent. 6. Classification by form: solvent-based release agent, water-based release agent, solvent-free release agent, powder release agent, paste release agent Application of release agent     Mold release agents are used in various molding operations such as concrete precast parts, products, glass fiber reinforced plastics, metal die casting, polyurethane foam and elastomers, injection molded thermoplastics, vacuum foamed sheets and extruded profiles. Advantages of release agent: 1. Demoldability (lubricity). When forming a uniform thin film and a complex shape, the dimensions are accurate. 2. Good mold release continuity. 3. The appearance of the formed object is smooth and beautiful, and does not cause dust adhesion due to the application of sticky release agent. 4. Superior secondary workability. When the release agent is transferred to the molded product, it has no adverse effect on processed products such as electroplating, hot stamping, printing, coating, and adhesion. 5. Easy coating. 6, heat resistance...

Today, Longhua Die Casting Machine introduces some operation requirements of aluminum alloy die casting machine, let's take a look together! 1. Strictly monitor the die casting process The temperature of the molten aluminum in the holding furnace should be controlled at ± 3 ° C in order to stabilize the stirring temperature. The temperature after stirring must be adjusted according to the chemical composition of each furnace to ensure that the solid phase rate is stable at ± 2%. The temperature of the mold must be checked and controlled so that the alloy can be smoothly filled and orderly solidified. It is necessary to rationally formulate and timely adjust the process parameters of the die casting machine, and make regular inspections on the die casting to ensure the quality of the die casting. 2.Precautions for release agent spraying operation Pay attention to how much paint is applied to the release agent to avoid too much paint, too little or missing paint. More paint can be sprayed on the parts that are difficult to be demolded, and less paint can be sprayed on the parts that are easy to demold. When spraying paint, use a spray gun to move from top to bottom in layers to let the water accumulated in the cavity flow from top to bottom and blow excess water out of the cavity. The cavity is easily adhered to the mold, first spraying at a short distance to cool down, and then spraying at a longer distance to form a coating film. Do not spray too close to prevent paint water from flowing in the cavity. After spraying, use air to blow away the excess and accumulated paint in the cavity, especially pay attention to the paint in deep cavities or dead corners to prevent the water from vaporizing into a large amount of gas after the heat, making the casting appear pores. , Under casting, cold insulation, blistering, this has a very important role in eliminating the occurrence of pores in the casting. 3.Precautions for hot film of die casting machine After using the mold temperature machine hot mold, when starting the die casting hot mold, you can use the liquid alloy low speed die casting hot mold 5-10 mold, and then use the normal semi-solid alloy and semi-solid die casting parameters for die casting production, which can protect the mold, It can also prevent flashing and flying materials.

1. What is shot-to-shot specific pressure and how to adjust it?     Answer: The shot pressure is the pressure per unit area of the metal liquid in the pressure chamber. On the premise of ensuring product quality, use a lower specific pressure as much as possible. The specific pressure of lighting die casting is generally less than 50MPA. The larger the product wall thickness, the higher the specific pressure requirement. The more complex the product structure, the higher the specific pressure requirements. 2. What is shot speed and how to adjust shot speed?     Answer: The injection speed refers to the speed of the injection head during die casting. It is divided into slow injection speed and fast injection speed. Generally speaking, the injection speed refers to the fast injection speed. The size of the slow shot speed is that when the shot head passes through the sprue, it is better not to splash the metal liquid, generally 0.1 ~ 0.5M / S, and the fast shot speed aluminum alloy is generally 0.1 ~ 1.1M / S. The thinner the wall thickness of the casting, the faster the injection speed, the more complex the shape of the casting, the faster the injection speed, the larger the projection surface of the casting, the faster the injection speed, and the longer the casting ball path, the faster the injection speed. 3． What is the pouring temperature and how do I choose a pouring temperature?     Answer: The pouring temperature generally refers to the average temperature of the molten metal poured into the injection chamber and filling the cavity. Generally, the lowest possible temperature is used while ensuring the molding and the required surface quality. The casting temperature of aluminum alloy is 650 ℃ ～ 720 ℃, the casting alloy has good fluidity, and the casting temperature can be lower; the casting temperature of thin-walled and complicated castings can be higher; the mold is large, the heat dissipation is fast, and the casting temperature can be high some. 4． What is the mold temperature, and what is the mold temperature during normal production of aluminum alloy die-casting molds?     Answer: The mold temperature is the temperature of the mold during the production process. The temperature of the aluminum alloy die-casting mold during normal production is: 200 ° C to 280 ° C. Generally, the thinner the casting, the more complicated the structure, and the higher the mold temperature requirements. 5． What is the filling time? How to choose the filling time?     Answer: The time required for the metal liquid to start to fill the cavity is called the filling time. Filling time of aluminum alloy die-casting: 0.01S ~ 0.1S. The principle of selecting the filling time is: (1) the alloy pouring temperature is high, the filling time should be longer; (2) the mold temperature is high, the filling time is longer; (3) if the thick wall part is far away from the inner gate, the filling is The time should be lo...

   In the last part, we talked about the equipment management of the die casting workshop. Today, Longhua Die Casting Machine will share with you another piece of dry goods knowledge: the installation and acceptance of the die casting machine equipment. (1) Installation of die-casting machine According to the drawing requirements of die-casting machine manufacturers, the traditional equipment installation method is to first build the equipment foundation and reserve embedded holes for the feet (see Figure 2). Then, put the anchor bolts into the grout, and then fine-adjust the equipment after the concrete has solidified. After the fine adjustment is completed, it will take some time for the equipment to be used normally after the surrounding oil and water tanks are completed. It basically takes nearly one month. In the actual installation process, considering that the above installation method takes too long, we can completely use the embedded steel structure to install the equipment. (2) Acceptance after installation The acceptance of the die-casting machine must first be based on the contract and the equipment test and acceptance record sheet, which is carried out one by one according to the acceptance items. When the manufacturer debugs the equipment, be sure to send someone to track the test and acceptance and record the test data.    Among them, the accuracy of the coaxiality of the pressure chamber is extremely critical, which directly affects the service life of the punch and the pressure chamber in the later stage. It is a mandatory inspection item for the newly purchased die casting machine. For PLC-controlled die-casting machines, the inspection of the scale-up board is easily overlooked. The function of the proportional amplification board is to control the output current in proportion to the magnitude of the input voltage, thereby changing the pressure and flow of the proportional valve to control the hydraulic system (if it is a single proportional valve, only the pressure is controlled). Specifically, if the total pressure of the digital adjustment system in the control cabinet is 0 to 14 MPa and the total flow rate is 0 to 100%, the pointers of the two ammeters should generally make     corresponding linear changes from 0 to 0.8 A. The linear error is allowed. About 2%. If the linearity error is too large, the linearity of the proportional plate will be insufficient, which will have a great impact on the adjustment of the die casting process parameters.    The supercharging and building pressure time cannot be measured specifically at the production site, and can only be estimated indirectly through the reaction of the pressure gauge pointer of the injection cylinder. The general approach is to adjust the boost delay, flow rate, and airbag pressure at a medium fast injection speed (such as about 3 m / s), watch the pointer of the injection cylinder pressure gauge change, and then close and clo...