Full CNC process? die-casting? CNC+die-casting?
Before restoring the manufacturing process of the mobile phone shell, let's first make clear several concepts: full CNC process and die-casting process, as well as CNC+die-casting. The full CNC mobile phone middle frame is a piece of aluminum plate (or other metal materials) milled into a specific shape through the CNC machining center. The die-casting is to use the mold cavity to apply high pressure to the molten metal, and to die-casting and stamping the liquid metal into a solid metal shell or middle frame, Of course, there is also the practice of combining the two processes.
Using the appendix, we can see that the full CNC process costs more and wastes more materials. Of course, the quality of the middle frame or shell under this process is better. The principle of die casting is not to waste, save time and cost, but it is not conducive to the later anodic oxidation process, and may also leave small problems affecting quality and appearance, such as sand hole flow marks. Of course, manufacturers have a concept of yield, and reliable manufacturers will not let these inferior products flow into the later production links.
After understanding the similarities and differences between the two processes, I started to talk about the metal shell processing technology that is also emerging on the 1000 yuan machine. After the bombardment of various large mobile phone conferences, we believe that everyone can break their fingers. Today, here, we are not just a dog's tail. Today, we mainly talk about the whole process of die casting+CNC process of metal mobile phone shell:
one
1、 Die casting stage
Before die-casting, we saw the original aluminum. Because the strength and hardness of pure aluminum are not enough, in fact, the mobile phone uses aluminum alloy, and has different characteristics according to different formulas. For example, the 6000 series aluminum alloy used for iPhone 6 is not strong enough, but it is easy to be bent due to its better ductility. The 7000 series used in the iPhone 6s has much higher strength, but is more brittle. It is more difficult to be compressed and deformed. However, once it exceeds the stress load, it will not bend, but break.
Well, the formula of aluminum alloy varies according to the demands of manufacturers. For example, rare earth, titanium, cobalt and other precious metals are added to the aluminum below. Of course, the proportion of these precious metals is very low, and they are not so expensive compared with real precious metals such as gold and platinum.
Since it is die-casting, it is not possible to directly cut the aluminum, but to melt the aluminum into a fluid, which is convenient for subsequent stamping in the mold. So the picture below is with temperature.
When these metals become liquid, it is time to inject them into the die-casting machine. This is the hardest time in aluminum's life. The aluminum water slowly flows down from the spider shaped groove, accepts the unimaginable stamping, and finally becomes the prototype of a shell. Although it looks simple, even in such a link, sand holes should be kept away from during shell processing. Once there are sand holes, there will be small pits in the subsequent processing and cutting. Therefore, there is still a need to improve the process and mold structure. This process of trial and error improvement will waste a lot of raw materials.
When strands of aluminum water are pressed one after another, the manipulator will peel off the rough shell and send it to the assembly line for the next round of test.
When strands of aluminum water are pressed one after another, the manipulator will peel off the rough shell and send it to the assembly line for the next round of test.
2、 Painting stage
After the previous die casting stage, these rudimentary shells should accept the next choice. Should they be anodized like the iPhone to achieve a cold metal texture, or should they be painted to wear a warm coat? This seems to be a difficult choice. However, the reality has nothing to do with aesthetics: die-casting shell is not conducive to anodizing, and there are also some product differentiation considerations.
After the machine tool processing, the excess part is washed off, and the burrs are removed, it can be seen that the shell has been basically formed. As for the upper opening, it is reserved for injection molding. The holes on the back cover are processed by CNC for injection molding and reinforcement of the body. This logic is the same as the white ribbon on the back of the iPhone 6. In order to make the antenna signal smooth, the back cover cannot use a whole piece of metal. So in the antenna part, we always see traces of plastic, which can not be overcome at present, and the plastic in this part is not a spray point.
After the injection molding is completed, after polishing again, the next step is the painting process. The manufacturers will certainly not take the plain shell directly. The painting process is also a technical activity. The plastic and metal parts on the back of the mobile phone have a clear boundary. If the painting process is not good enough, the boundary will still be visible. Therefore, whether the metal and plastic parts can be seen is an important indicator to judge whether the painting process is good or not. The lower mobile phone case will move slowly on the assembly line. Eight groups of 16 nozzles will spray the case in all directions to ensure uniformity.
After painting, the paint is baked. The process of painting is like a mushroom forest. In addition, spray painting and baking paint are generally not only good once, but also repeated. In addition, there will be another polishing between paint baking and painting. This group of mobile phone cases will eventually undergo five painting, five painting and two polishing. Generally, the first coat is primer, and pearl powder or aluminum powder will be added to the last coat of paint to ensure the texture and appearance.
3、 CNC stage
At this stage, mobile phone manufacturers like to release the most, because this part has a very pleasant part, called diamond cutting.
However, before the diamond is cut, manufacturers need to make holes for cameras, volume keys, speakers and other parts. Below is the picture of camera holes for the shell.
After each hole is opened, it is a popular diamond cutting link. To speak of diamond cutting, it is not because the cut frame looks like a diamond, but the cutting tool is a diamond.
The yellow part in front of the cutting props can be seen below, that is, the diamond. As for why it looks dull and ordinary compared with the diamond on the diamond ring, I guess it should be an artificial diamond, with the hardness of natural diamonds, but without the luster of diamonds after cutting. It can also be seen below that the cut shell edge has a good highlight. It is not similar to the previous painting and baking varnish. The diamond cutting here can not be completed once. At least two times and three times are the conscience of the industry. After all, one more step is more expensive.
It should be pointed out that in order to ensure that the cutting width and angle are strictly consistent, a laser tool setting instrument is also used here to control the thickness and width of the cutting edge. After all, the straightest thing in the world is not Wang Leehom, but the light. In simple terms, the laser tool setting first walks around the place to be cut, and the measured data according to the shape of the object is fed back to the CNC machine tool, and then the cutting can start.
OK, here is a close-up of the MVP diamond cutter on this mobile phone case manufacturing trip.
The manufacturers showed us a brilliant process, but in the field, we found that the process from a lump of aluminum pimple to a delicate shell has gone through a lot, and some processes can even be described as cumbersome, but just like girls are willing to use a knife on their face to look good, they should also use a knife on the shell.