What are the differences between stamping, die-casting and CNC machining?

Today, even thousands of mobile phones are made of metal, and the cold touch can even stimulate users’ desire to consume. However, although metal phones look the same, their physical structure can vary greatly. Only by mastering the secrets behind them can we have the opportunity to “see it.” Cost and attitude There is no doubt that the texture of metallic materials is far superior to plastic (polycarbonate), and it is also the only magic weapon to enhance the color value of mobile phones. However, there are many processes that give metal elements to mobile phones, the most common being stamping, die casting and integrated CNC. Stamping: Press the metal plate from the phone case with a punch. Solid to solid is a material deformation. Die Casting: The molten liquid metal is filled into the mold cavity by pressure, cooling and shaping. Liquid to solid is a material that is formed. CNC: Cutting, drilling and polishing the entire piece of metal with a CNC machine, resulting in an integrated metal casing. In terms of cost, processing difficulty, process time consumption, physical strength and quality, stamping &… die casting < CNC machining. Therefore, the technical solutions adopted by metal mobile phones depend on the manufacturer's demand for cost and attitude towards consumers. Metal sequelae Although metal materials have good hand and high strength, they have a fatal flaw: signal shielding. Therefore, 100{c1f006c951f401087799489f262635b7ee79ba7fc083ceb14cce64024f2e2bc5} (excluding the part of the screen glass) does not exist in the case of a mobile phone made of metal. In order to achieve signal overflow, the phone must "ventilate" the metal parts and solve the problem of shielding signals by filling other materials. Currently, the methods for "ventilating" metal phones are mainly three-stage, window and nmt nanoinjection. However, stamping, die-casting, integrated CNC and three-phase, window and nmt nano-injection molding combine to form the "full live phase" of current metal mobile phones. Three stages: the choice of entry The so-called three-stage type refers to a design in which the middle is made of metal, the upper end and the lower end are made of plastic, and then spliced ​​together. The third level is the "cheap commodity" in metal mobile phones, and the stamping process is the best partner for the three-stage solution. Take the red rice notepad as an example. Its metal casing is actually just a "iron piece". It covers the plastic material made of the middle frame and the skeleton. The metal and plastic parts are painted in a color through the painting process. m makes it look more harmonious and unified, giving the illusion that the entire back cover is metal. In addition, Meilan Notepad also chose the stamping process, which was called "punching + structural parts combination" by Meizu. Window opening: advanced selection The so-called window type refers to "digging" a hollow metal "window" at the top and bottom (or one end) of the integrated metal casing, and then filling its material, such as plastic or glass, can transmit signals. It should be noted that the window scheme can be matched with the die casting process or the numerical control integrated process. Meilan metal is representative of the die casting process + window scheme. The phone opens the signal sunroof on the upper and lower ends of the integrated metal back cover and is then filled by an injection molding process. High-gloss chamfers, camera outer ring and home button edges are polished by cnc (to improve visual quality). Finally, the metal is covered by a color paint and spray process, and finally the metal is made into a plastic hand (which is also sprayed by many players). The meizu mxne pro series, oppo r7/r9, Huawei mate s8 and other mobile phones are representative of the integrated cnc technology + window solution. Most of them are cut by CNC machine tools and form a whole piece of metal. The window is directly drilled for overflow signal, and then filled and beautified by injection molding, sand blasting, coloring and other processes. Nano Injection Molding: An Extreme Choice Although the windowing scheme does not destroy the integrated metal structure, the area of ​​the hollowed out portion for injection molding is large, thereby reducing the value of the metal ratio. At this time, a numerical control integrated process + + nmt nano-injection molding scheme was proposed. Iphone 6 should be the best spokesperson for the program. Its metal back cover has been cut into several thin strips by CNC machine tools and is filled with nmt nano-injection molding process. The filled strips are dubbed by the user as "leucorrhea". A similar "leucorrhea" also appears on mobile phones, such as leucorrhea and living x6. The good news is that in order to prevent these white stripes from affecting the overall appearance of the phone, how to reduce the number of stripes and the width of the stripes is the direction of competition. In short, there are still 369 mobile phones selling metal materials. Due to differences in technology and structure, there are big differences in cost, firmness and feel. The phone claims to have a metal body, but the technology behind it may not really match the selling price.