CNC Machining and Die Casting Process Combined to Manufacture Mobile Phone Metal Shells
In recent years, the appearance trend of mobile phones has been changing to metallization. Major manufacturers have launched all-metal mobile phones. CNC has become a must-have device for mobile phone casing manufacturers due to its high efficiency, high precision and stable processing quality. Many structural engineers may not know the specific processing and details, but only know that the product is machined by CNC. However, if there is no good process, there will be no good results. Understanding the processing process will help the project to proceed smoothly. This article introduces the processing process of the metal middle frame of the whole mobile phone.
Overview:
At present, the whole metal casing manufacturing process of 3C products can be roughly divided into three types, one is full CNC machining, the other is die casting, or the combination of CNC and die casting.
CNC machining process:
As the name implies full CNC machining (Computernumerical control machine tools, CNC) is to start from an aluminum alloy sheet material (metal or other sheet materials). It is directly processed into the shape of the back cover of the mobile phone by using a precision CNC machining machine, including various steps, grooves and screw holes in 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 melted metal;
CNC combined with die casting process:
The combination of CNC and die casting is to first die-cast and then use CNC finishing.
Process advantages and disadvantages:
The cost of the CNC process is relatively high and the material waste is also high. Of course, the quality of the middle frame or casing under this process is also better. The principle of die casting is not to waste, save time and cost, but it is not conducive to the later anodizing process, and may leave sand hole flow marks and other minor problems affecting the quality and appearance. Of course, manufacturers all have a concept of good product rate, reliable manufacturers will not let these defective products flow into the later production links. After understanding the similarities and differences between the two processes, I began to talk about the processing technology of mobile phone metal casings.
Before CNC machining begins, 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 processes that need to be programmed are more and more complex. Programming includes machining process settings, tool selection, speed setting, distance per tool feed, and more. In addition, the clamping methods of different products are different, the fixtures should be designed before processing, and some complex structures require special fixtures. At the same time, it is necessary to evaluate the size of the blank and the number of CNCs. The quality of the preliminary evaluation directly affects the processing time and processing cost.
The cylindrical aluminum is cut and extruded according to the size of the blank evaluated previously. This process, known as aluminum extrusion, allows the aluminum to be extruded into a regular aluminum plate for easy processing while being denser and harder. Because the original aluminum is not strong enough in hardness and strength. The body of the mobile phone is generally made of aluminum alloy. According to different formulas, the material also has different characteristics. For example, the 6000 series aluminum alloy used in the iPhone 6 is not strong enough, and a large amount of bending occurs. The 7000 series used in the iPhone 6s is much stronger, but it becomes brittle. It is more difficult to be deformed by pressure. Once it exceeds the load, it is not bent, but broken. The formulation of aluminum alloys varies according to the manufacturer's different needs.
CNC machining process:
1, aluminum extrusion, DDG, rough milling lumen
Then the aluminum alloy plate is milled into the size required for the mobile phone body to facilitate CNC precision machining. Followed by the rough milling of the inner cavity, the inner cavity and the column where the fixture is positioned are processed, which plays a fixed role in precision machining.
2, milling antenna slot, T processing, nano injection molding
The biggest drawback 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 T-treatment of the antenna slot machine is carried out, and the metal fuselage is placed in the special chemical agent of T liquid, thus forming nano-scale holes on the surface of aluminium alloy, which is convenient for nano-injection . The next step is to achieve nano-injection molding. Under high temperature and high pressure, special plastic materials are extruded into the T-treated grooves. Then, nano-injection moulding is realized. Under high temperature and high pressure, special plastic materials are extruded into T-treated grooves.
Injection molding materials are generally PPS and PBT
3, fine milling curved surface, fine milling side
After the nano-injection is finished, it is necessary to process the surface of the metal material, 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
The use of top-level high-speed precision CNC machine tools will make the metal fuselage to A1-A2 level of cleanliness, which is far from enough. It is necessary to process the body to the A0 grade finish by a polishing process, and after this step, the mirror effect can be achieved. The metal surface is then treated to a grinding effect. Sand blasting is to obtain the surface of the film decoration or the fine reflective surface to meet the special design requirements such as gloss softness.
5, Primary Anode, High Gloss Processing (Diamond Cutting), Fine Milling of Inner Cavity
In order for the metal body to be not contaminated by external factors such as sweat and to improve its stability, it must be anodized. This is also the process of coloring the body of the phone. The anodizing treatment of aluminum is an oxide film formed by the action of electric current on the metal surface. It is rich in color, beautiful in color, good in electrical insulation, hard and wear resistant, and extremely resistant to corrosion.
After the first anode, the volume keys, loudspeakers and other parts need to be perforated. It is a very mysterious diamond cutting link to use the highest level of ultra-high-speed CNC machine tool to cut edges and corners after opening. It is said that diamond cutting is not because the cut-out frame is crystal-clear like a diamond, but the tool that completes the cutting is a diamond. The edge of the cut case will have a good high light perception. With the thick and fine knife pattern using the principle of refraction, the decorative effect can be greatly enhanced.
It should be emphasized that in order to ensure that the width and angle of the cutting are strictly consistent, it is necessary to use a kind of laser tool setting instrument to control the thickness of the knife edge and the width of the trimming edge. Simply speaking, the laser alignment tool first takes a circle in the place to be cut, and then feeds back the measured data to the CNC machine tool according to the shape of the object to be measured, and then the cutting can start.
6, secondary anode, milling conductive position
Secondly, the outer surface of the metal fuselage is anodized for a second time to form a dense and hard oxide film on the outer surface of the shell to ensure the wear resistance and stain resistance of the fuselage. The anodized aluminum alloy casing will have poor conductivity, so it is necessary to remove the local anodized film to expose the metal to obtain a good grounding effect. At this time, the CNC processing of the conductive position needs to be milled again.
7, hot melt nut
Processing is basically completed here.
Finally, the manipulator is used to insert the assembly nut into the injection molded plastic for fixing the motherboard or other components.
Overview:
At present, the whole metal casing manufacturing process of 3C products can be roughly divided into three types, one is full CNC machining, the other is die casting, or the combination of CNC and die casting.
CNC machining process:
As the name implies full CNC machining (Computernumerical control machine tools, CNC) is to start from an aluminum alloy sheet material (metal or other sheet materials). It is directly processed into the shape of the back cover of the mobile phone by using a precision CNC machining machine, including various steps, grooves and screw holes in 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 melted metal;
CNC combined with die casting process:
The combination of CNC and die casting is to first die-cast and then use CNC finishing.
Process advantages and disadvantages:
The cost of the CNC process is relatively high and the material waste is also high. Of course, the quality of the middle frame or casing under this process is also better. The principle of die casting is not to waste, save time and cost, but it is not conducive to the later anodizing process, and may leave sand hole flow marks and other minor problems affecting the quality and appearance. Of course, manufacturers all have a concept of good product rate, reliable manufacturers will not let these defective products flow into the later production links. After understanding the similarities and differences between the two processes, I began to talk about the processing technology of mobile phone metal casings.
Before CNC machining begins, 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 processes that need to be programmed are more and more complex. Programming includes machining process settings, tool selection, speed setting, distance per tool feed, and more. In addition, the clamping methods of different products are different, the fixtures should be designed before processing, and some complex structures require special fixtures. At the same time, it is necessary to evaluate the size of the blank and the number of CNCs. The quality of the preliminary evaluation directly affects the processing time and processing cost.
The cylindrical aluminum is cut and extruded according to the size of the blank evaluated previously. This process, known as aluminum extrusion, allows the aluminum to be extruded into a regular aluminum plate for easy processing while being denser and harder. Because the original aluminum is not strong enough in hardness and strength. The body of the mobile phone is generally made of aluminum alloy. According to different formulas, the material also has different characteristics. For example, the 6000 series aluminum alloy used in the iPhone 6 is not strong enough, and a large amount of bending occurs. The 7000 series used in the iPhone 6s is much stronger, but it becomes brittle. It is more difficult to be deformed by pressure. Once it exceeds the load, it is not bent, but broken. The formulation of aluminum alloys varies according to the manufacturer's different needs.
CNC machining process:
1, aluminum extrusion, DDG, rough milling lumen
Then the aluminum alloy plate is milled into the size required for the mobile phone body to facilitate CNC precision machining. Followed by the rough milling of the inner cavity, the inner cavity and the column where the fixture is positioned are processed, which plays a fixed role in precision machining.
2, milling antenna slot, T processing, nano injection molding
The biggest drawback 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 T-treatment of the antenna slot machine is carried out, and the metal fuselage is placed in the special chemical agent of T liquid, thus forming nano-scale holes on the surface of aluminium alloy, which is convenient for nano-injection . The next step is to achieve nano-injection molding. Under high temperature and high pressure, special plastic materials are extruded into the T-treated grooves. Then, nano-injection moulding is realized. Under high temperature and high pressure, special plastic materials are extruded into T-treated grooves.
Injection molding materials are generally PPS and PBT
3, fine milling curved surface, fine milling side
After the nano-injection is finished, it is necessary to process the surface of the metal material, 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
The use of top-level high-speed precision CNC machine tools will make the metal fuselage to A1-A2 level of cleanliness, which is far from enough. It is necessary to process the body to the A0 grade finish by a polishing process, and after this step, the mirror effect can be achieved. The metal surface is then treated to a grinding effect. Sand blasting is to obtain the surface of the film decoration or the fine reflective surface to meet the special design requirements such as gloss softness.
5, Primary Anode, High Gloss Processing (Diamond Cutting), Fine Milling of Inner Cavity
In order for the metal body to be not contaminated by external factors such as sweat and to improve its stability, it must be anodized. This is also the process of coloring the body of the phone. The anodizing treatment of aluminum is an oxide film formed by the action of electric current on the metal surface. It is rich in color, beautiful in color, good in electrical insulation, hard and wear resistant, and extremely resistant to corrosion.
After the first anode, the volume keys, loudspeakers and other parts need to be perforated. It is a very mysterious diamond cutting link to use the highest level of ultra-high-speed CNC machine tool to cut edges and corners after opening. It is said that diamond cutting is not because the cut-out frame is crystal-clear like a diamond, but the tool that completes the cutting is a diamond. The edge of the cut case will have a good high light perception. With the thick and fine knife pattern using the principle of refraction, the decorative effect can be greatly enhanced.
It should be emphasized that in order to ensure that the width and angle of the cutting are strictly consistent, it is necessary to use a kind of laser tool setting instrument to control the thickness of the knife edge and the width of the trimming edge. Simply speaking, the laser alignment tool first takes a circle in the place to be cut, and then feeds back the measured data to the CNC machine tool according to the shape of the object to be measured, and then the cutting can start.
6, secondary anode, milling conductive position
Secondly, the outer surface of the metal fuselage is anodized for a second time to form a dense and hard oxide film on the outer surface of the shell to ensure the wear resistance and stain resistance of the fuselage. The anodized aluminum alloy casing will have poor conductivity, so it is necessary to remove the local anodized film to expose the metal to obtain a good grounding effect. At this time, the CNC processing of the conductive position needs to be milled again.
7, hot melt nut
Processing is basically completed here.
Finally, the manipulator is used to insert the assembly nut into the injection molded plastic for fixing the motherboard or other components.
