The symbolic components of aluminum die castings are crankcase (4 or 3 cylinders with cast iron bushing), clutch housing, oil pan, steering column, etc. Automobile steering wheel frame, which was previously made of aluminum (in iron mold frame), is now mainly injected with integral magnesium to limit weight and moment of inertia. Die cast brass parts are gearbox forks with new market water body (copper cage rotor, antibacterial alloy parts in the medical industry). Compared with aluminum alloy, zinc alloy market is more diversified, used for automotive industry, electronic products (hood, card fixing), luxury goods (perfume bottle cap, etc.), sports or medicine. Finally, lead alloy is related to fishing, radiation protection and counterweight.
Different machines (cold chamber, hot chamber, etc.)
According to the transformed alloy, cold chamber machine technology or hot chamber machine technology is used. The two technologies are different in the level of holding furnace. Therefore, in the cold chamber molding, the liquid metal is taken out by the automatic ladle (or metering furnace), then poured into the metal container, and finally injected by the horizontal injection piston. In hot chamber technology, the injection system is immersed in liquid metal (400 ° C), the vertical injection piston injects the metal into the mold, and the metal enters the mold through gooseneck and injection nozzle. This technology is reserved for zinc and lead alloys (which are less corrosive than aluminum in terms of metal elements),
There is also the so-called "multi slider" hot chamber machine, which injects on the parting surface. These machines (dynacast, techmire) have very high productivity and are specially used for injecting very small parts (tens of grams) of zinc, lead or magnesium alloys. The machine has two or four sliding blocks, and different blocks constituting the mold are installed on the sliding block. The technology is specific, and the die is incompatible with the traditional hot chamber die casting machine.
Part quality control
Parts are first 100% visually inspected by the operator monitoring the machine to identify any external faults (recasting, faults, cracks). Then, the parts are taken out from each team regularly (the frequency depends on the criticality of the product), and the internal defects that do not meet the part specifications (mainly pores and shrinkage traces) are detected by radiographic inspection. In some cases, the air tightness / water tightness can be checked by sampling, or the air tightness / air tightness can be checked automatically after processing. The leaking part can be the object of the impregnation operation, in which the resin infiltrates the existing pores to fill them. Therefore, some parts can be recovered after the impregnation operation. In order to avoid having to check the parts separately, people are increasingly trying to check the manufacturing parameters as completely as possible. Therefore, in some sites, the machine monitors the main injection parameters in each cycle, so if one of the monitoring parameters exceeds the min max control interval, the machine can discard the parts in real time. Then the discarded parts are either rejected or 100% NDT inspected. The machine monitors the main injection parameters in each cycle, so if one of the monitoring parameters exceeds the minimum maximum control interval, the machine can discard the parts in real time. Then the discarded parts are either rejected or 100% NDT inspected. The machine monitors the main injection parameters in each cycle, so if one of the monitoring parameters exceeds the minimum maximum control interval, the machine can discard the parts in real time. The discarded parts are then either rejected or 100% NDT inspected
Short history of die casting
The major development of the printing press around 1850 required the mass production of lead tin fonts (previously made separately and manually) at low cost, and made a significant contribution to the development of the first manual injection machine dedicated to the marlet. Then die casting was applied for the first time in the bicycle and phonograph industry in the United States. It should be noted that Charles Babbage (UK) produced small precision parts (lead, antimony, tin and zinc) for his mechanical computer project in 1868. Then Hermann doehler founded doehler die casting company in Brooklyn (New York) in 1908 and made a lot of efforts for the development of Technology (molds, machines, etc.). Then, World War I put the foundry under pressure from military applications (grenades, rockets...). The composition of zinc alloy was not standardized at that time, because the alloy may vary greatly from workshop to workshop. The development of American cars after World War II and the very popular "zinc chromium" design at that time promoted the large-scale production of zinc foundries.
Aluminum cold chamber machines were developed much later and were not commercialized until the 1930s. One of the pioneers in Europe was Josef Polak of the Czech Republic, which was equipped with vertical piston cold chamber machines (some still in use). Operating in Eastern Europe). Then, with the mechanization and gradual automation of the construction site (ladle and automatic poeyeur,...) Until today's machines, the horizontal injection of aluminum, simpler, has become common. Compared with other industrial processes, die casting was the subject of early robotics because the first industrial robot was developed by union Inc.
Alloy processed by pressure casting
Recycled aluminum alloy (from recycling) is the most used in die casting so far. Alsi9cu3 (FE) (or 46000 according to European standard EN 1706) is therefore a leading alloy in the world and is famous for different names (A380 in North America, adc10 in Japan, etc.), and their chemical compositions are very similar Then alloy alsi12 (eutectic) and AlSi12Cu, alsi10mg or less used super silicon alsi17cu4. Finally, new low iron ductile alloys (silafont type) are entering the market to produce parts with high mechanical properties (with or without heat treatment).
Zinc alloy, better known as zinc alloy, is mainly composed of zinc alloy 3 and zinc alloy 5 with different copper content. In order to obtain higher heat resistance, zinc alloys (ZA8, ZA12 and ZA27) with higher aluminum content (8%, 12% and 27%, respectively) can be used. Copper alloys are also mainly injected with 60 / 40 brass grade (cuzn40) and pure copper (due to its high thermal conductivity) or new antibacterial grade. Magnesium was transformed into a pressure foundry (hot chamber for small parts and cold chamber for large parts). There is a difference between AZ91D (the most common) and AM50 and AM60 with higher elongation. Finally, lead alloys (soft lead, lead tin or lead antimony alloys) are injected.
Future development of die casting
Die casting has been highly automated and robotic to meet the growing productivity needs of the automotive industry. Many technologies developed from die casting (indirect squeeze casting, thixotropic casting, rheo casting, core based on molten salt, closed metal foam such as aluminum and zinc alloy) have been developed, but no significant progress has been made in technology maturity (TRL) or mother technology. The peripheral equipment around the injection molding machine has also doubled to achieve greater control of the process: quantitative oven, coating robot, mold cooling system (jet cooling), vacuum system, blower cooling parts, degassing rotor, etc. As we mentioned above, new alloys (ductile alloys, specific zinc alloys) have also been listed, giving the design office more choices.
Finally, for the production of high value-added auto parts (engine block), some die-casting factories have launched shot blasting machines and machining centers, which can reduce the number of operators controlling the production line and limit the flow of parts in the factory. In the future, it is conceivable to launch the quality control system (tomography type) and develop the digital twins of each machine to ensure the best management of manufacturing parameters (cycle time, coating, hot die, etc.) to limit non quality and better predict shutdown (main shaft replacement, etc.) and preventive maintenance. Such a system indicates the application of 4.0 factory in die casting in the future.