Four Steps for Die Casting Process
High-pressure die casting is a very common and important way to produce parts. So it also called traditional die casting. There are four steps for die casting process: mould preparation, filling, ejection and shakeout. First, spray the mould cavity by lubricant to prepare the mould. The lubricant can help you to control the temperature of the mould better and remove the part easily.
Then close the mould and injectmolten metal into the mould under high pressure, from 10 to 175 megapascals (1,500 and 25,400 psi). After the mould cavity is filled by material, maintain the pressure until the part solidifies. Next, open the mould and eject the shot by ejector pins (shots are different from parts because the mould can have several cavities and produce several parts). The last step is shakeout, separate the scrap from the shot which includes the gate, runners, sprues and flash. in this part, die caster usually use power press or hydraulic press to trim die. Other methods of shaking out include sawing and grinding.
High-pressure injection is for quick fill of the mould. It is required the whole cavity fills before anywhere of the parts solidifies. It can avoid discontinuity, even if the part requires thin sections. But in this way, problem of air entrapment will happen, because the material fills the mould too quickly to let the air to escape. This problem is minimized by vents along the parting lines. However, even in a highly refined process there will still be some porosity in the center of the parts. Most parts need secondary operations to produce features that cannot made by die casting such as tapping a hole, polishing, plating or painting.