xiehe model

In recent years, the appearance trend of mobile phones has shifted to metallization. Major manufacturers have launched all-metal mobile phones. CNC has become an essential equipment for mobile phone case manufacturers with its high efficiency, high precision and stable processing quality. Many structural engineers may not know the specific machining and details, only know that the product is CNC machined. But without a good process, there will be no good results. Understanding the process will help the project run smoothly. This article introduces the processing technology of the entire metal frame of the mobile phone.

Overview:

At present, the all-metal shell manufacturing process of 3C products can be roughly divided into three types, one is full die casting, the other is die casting, or a combination of CNC and die casting.

CNC machining process:

As the name suggests, full CNC machining starts from an aluminum alloy sheet (metal or other sheet). Use the precision CNC machining machine to directly process the shape of the back cover of the mobile phone, including various steps, grooves and screw holes of the inner frame.

Die casting process:

The process of full die casting is very similar to the production process of plastic products. They are all processed with precision molds, but the material is changed from plastic to molten metal;

CNC combined with die casting process:

The combination of CNC and die casting is first die casting, and then CNC finishing.

Process advantages and disadvantages:

CNC machining costs are relatively high, and material waste is also high. Of course, the quality of the middle frame or chassis under this process is also better. The principle of die casting is no waste, saving time and cost, but it is not conducive to the subsequent anodizing process, and may leave small problems such as sand hole flow marks that affect the quality and appearance. Of course, manufacturers all have the concept of yield, and reliable manufacturers will not let these defective products flow into the later production process. After understanding the similarities and differences of the two processes, I began to talk about the processing technology of the metal casing of the mobile phone.

Before CNC machining can begin, modeling and programming are first required. The difficulty of 3D modeling is determined by the product structure. The modeling of complex products is difficult, and the process of programming is becoming more and more complex. Programming includes machining process setting, tool selection, speed setting, feed distance for each tool, etc. In addition, the clamping methods of different products are different. The fixtures should be designed before processing. Some complex structures require special fixtures. At the same time, the size of the blank and the number of CNCs need to be evaluated. The quality of the initial evaluation directly affects the processing time and processing cost.

The aluminum in the cylindrical shape is cut and extruded according to the previously evaluated billet dimensions. This process, known as aluminum extrusion, allows aluminum to be extruded into regular aluminum sheets for easier processing, while becoming denser and harder. Because the original aluminum is not strong enough in terms of hardness and strength. The body of the mobile phone is generally made of aluminum alloy. Depending on the formulation, the material also has different properties. For example, the 6000 series aluminum alloy used in the iPhone 6 is not strong enough, and there is a lot of bending. The 7000 series used by the iPhone 6s was much stronger, but it became brittle. Compression deformation is more difficult. Once overloaded, it does not bend, but breaks. Aluminum alloy formulations vary from manufacturer to manufacturer.

CNC machining process:

1. Aluminum extrusion, DDG, rough milling inner cavity

Then the aluminum alloy plate is milled into the size required for the mobile phone body, which is convenient for CNC precision machining. The second is rough milling of the inner cavity, and processing of the inner cavity and the column where the fixture is located, which plays a fixed role in precision machining.

2. Milling antenna slot, T machining, nano injection molding

The biggest disadvantage of the metal body is the signal problem, so the metal body must be slotted first so that the signal can enter and exit. Then the antenna slotting machine is T-shaped, and the metal body is placed in the special chemical agent of the T liquid, so that nano-scale holes are formed on the surface of the aluminum alloy, which is convenient for nano-injection. The next step is to realize nano-injection molding. At high temperature and pressure, special plastic materials are extruded into the T-treated grooves. Then, nano-injection molding is realized. Under high temperature and pressure, a special plastic material is extruded into T-shaped grooves.

Injection molding materials generally include PPS and PBT.

3. Fine milling surface, fine milling side

After the nano-injection is completed, the metal material needs to be surface treated, that is, the 3D molding of the mobile phone body. After this process, the basic shape of the phone body is completed.

4. Polishing, sandblasting

Using top-level high-speed precision CNC machine tools will make the metal body reach A1-A2 cleanliness, which is far from enough. The fuselage needs to be processed to A0-level finish through the polishing process. After this step, the mirror effect can be achieved. The metal surface is then ground. Sandblasting is to obtain a film-decorated surface or a finely reflective surface to meet special design requirements such as glossy softness.

5. One anode, high light treatment (diamond cutting), inner cavity fine milling

In order to prevent the metal body from being polluted by external factors such as sweat and improve its stability, anodizing treatment must be carried out. This is also the process of coloring the body of the phone. The anodizing treatment of aluminum is to form an oxide film on the metal surface by the action of electric current. It is rich in color, beautiful in color, good in electrical insulation, hard and wear-resistant, and extremely corrosion-resistant.

After the first anode, the volume keys, speakers and other parts need to be punched. Using the highest level of ultra-high-speed CNC machine to cut edges and corners after opening is a very mysterious diamond cutting process. Diamond cutting is not because the frame that is cut is as crystal clear as a diamond, but the tool that completes the cut is a diamond. Cutting the edges of the case will give a nice highlight. The thickness of the knife pattern uses the principle of refraction, which can greatly enhance the decorative effect.

It should be emphasized that in order to ensure that the width and angle of the cutting are strictly consistent, a laser tool setter is required to control the thickness of the blade and the width of the trimming. Simply put, the laser alignment tool first takes a circle at the place to be cut, and then feeds the measurement data to the CNC machine according to the shape of the object to be measured, and then the cutting can be started.

6. Secondary anode, milled electric potential

Then, the outer surface of the metal fuselage is subjected to secondary anodization to form a dense and hard oxide film on the outer surface of the shell to ensure the wear resistance and anti-fouling properties of the fuselage. The anodized aluminum alloy housing will have poor conductivity, so it is necessary to remove the local anodized film to expose the metal for a good grounding effect. At this time, the CNC machining of the conductive positions requires milling again.

7. Hot melt nut

The processing is basically completed here.

Finally, the robotic arm is used to insert the assembly nut into the injection-molded plastic, which is used to hold the motherboard or other components in place.