Metal fuselage processing technology: casting, forging, punching, CNC
In the past two years, metal mobile phones have become a hot spot in the industry and have been widely used in consumer electronics. This paper introduces several metal processing technologies and applications of related products in detail.
1. CNC + anode: iPhone 5/6, HTC M7
2. Forging + CNC: Huawei P8,HTC M8
3. One die casting: Samsung A7
4. Stamping and hydraulic forming: HTC ONE MAX
5. Stamping + CNC: Huawei MATE 7
The following figure describes the comparison of several mobile phone shell metal processing technologies in processing cost, CNC dosage, processing cycle, yield, designability and appearance texture.
From the overall analysis, the larger the area of a process radar map, the better its comprehensive performance is generally indicated; From the analysis of a single dimension, each dimension is divided into 10 levels, A higher score indicates that a process is better in this dimension.
Casting is a metal hot processing technology mastered by human beings earlier and one of the basic technologies of modern machinery manufacturing industry. The casting blank achieves the purpose of free mechanical processing or a small amount of processing due to its near molding, which reduces the cost and time to some extent.
Metal casting is to inject molten metal into the hollow mold made of high temperature resistant material, and obtain the expected shape of the product after condensation; The obtained product is the casting.
Figure: liquid metal-filling-solidification shrinkage-casting
I. Gravity Casting
It refers to the process of injecting metal liquid into mold under the action of Earth gravity, also known as casting. The metal liquid is generally poured into the pouring mouth by hand, and the product is obtained by filling the cavity, exhausting, cooling and opening the mold with the self-weight of the metal liquid.
Gravity casting has the advantages of simple process, low mold cost, few internal air holes, heat treatment and so on, but at the same time, it has poor compactness and strength, which is not suitable for producing thin-walled parts and low surface finish, defects such as low production efficiency and high cost.
II. Die Casting
Under the action of high pressure, liquid or semi-liquid metal fills the die casting cavity at a higher speed, and forms and solidifies under pressure to obtain castings.
Squeeze casting can be quickly filled, the production efficiency is extremely high, the product has good compactness, high hardness, good surface finish, and can produce parts with relatively thin wall thickness; At the same time, due to the use of high pressure air for filling, there are a lot of gas involved inside, which is easy to form pores inside the product. Therefore, heat treatment cannot be carried out (the internal gas will expand during heat treatment, resulting in defects such as bulging or cracking of the product) and post-machining with too large processing capacity (avoid penetrating the dense layer on the surface and exposing subskin blowhole, causing the workpiece to be scrapped).
However, ordinary aluminum die casting process is difficult to deal with smooth aluminum oxide film. The reason is that silicon is added to the raw material in order to improve the fluidity and make it flow through all areas of the mold. Therefore, if you want to color the aluminum die casting, you may lose the high-grade feeling because it looks like plastic after coating.
The die casting process is applied to mobile phones, but because the surface cannot be anodized, most enterprises adopt spraying treatment, such as Meizu’s latest Meilan Metal, as shown in the following figure.
Meizu’s latest Meilan Metal
Recently, Japan OTAX company (OTAX) announced that it has developed a low-cost die-casting process to achieve smooth aluminum oxide film treatment and enhance the high-grade sense of products. It has been applied to mobile phone shell and earphone parts, the following figure shows the earphone parts produced by Danish Bang & Olufsen company by aluminum die casting process.
Forging is one of mechanical metal working methods. It refers to a processing technology that uses pressure to change the shape of metal raw materials to obtain forgings with certain mechanical properties, certain shapes and sizes.
Classification of forging
1. Hammer or Smith Forging
The same way is used for hammer forging or iron striking. It is to heat the working object to the forging temperature, and forge between the flat hammer and drill plate; Small pieces can be called iron striking manually; steam Hammer is required for large parts, as shown in the following figure. Among them, the work is placed between drill plate and flatter. As for the structure of steam hammer, it depends on the forging capacity. The light one is single rack, and the heavy one is double rack.
2. Drop Hammer Forging
The difference between drop hammer forging and plane forging lies in that the drop hammer forging has mold holes, and the working parts bear the pressure or impact force in the mold holes, and then make plastic deformation according to the shape of the mold hole. As shown in the following figure, in order to make the kinetic energy of metal sufficient, forging is often divided into several levels, and the change of each level is progressive to control the direction of movement. As for the number of series, see the shape and size of forgings, the forgeability of metals and the precision requirements of workpiece size.
3. Press Forging
Pressure forging is a forging method that uses slow pressure to make metal squeeze in the mold. Due to the long stress time of metal, the extrusion effect is only applied to the surface of the forging, it is also related to the central part of the workpiece. Therefore, it can achieve uniform effect inside and outside, and the quality of its products is better than that of hammer forging.
Forging used in the process of mobile phone shell can effectively reduce CNC time, thus relatively low cost; And aluminum alloy with aluminum content exceeding 95% can be used for anodic oxidation. Process: firstly, the thick structure of the mobile phone is obtained by forging; Then the unnecessary parts are milled off by CNC; NMT obtains the metal + plastic integrated structure; Anodic oxidation surface treatment; Finally, the antenna cover is glued.
For example, OPPO R7/R7 PLUS, as shown in the following figure
4. Upset Forging
Forging rough or end pressure forging is usually aimed at one end of a uniform long rod to be forged rough or shaped, as shown in the following figure. Clamp the long rod in the mold, one end of which is heated to high temperature, followed its axial direction, and then pressurize the end to make it rough or shape.
5. Roll Forging
The following figure shows the principle of rolling forging.
In the picture, two non-100% round rollers (with a diameter reduction rate of 25 to 75%, and the rest can be cut into slots as needed) are used to feed the rod into the roller and clamp it, and then continue to rotate, make the rod roll under rolling pressure, reduce the diameter and push forward; When the roller is turned to the opening position again, the rod roll can be pulled back to the original position for one cycle rolling, or send it to another trench for another construction.
Metal impact molding is a metal cold processing processing method, also known as cold stamping or sheet stamping. With the power of stamping equipment, the sheet metal is directly pressed and formed in the mold, stamping parts are widely used in the manufacture of automobile parts and household appliances.
Applicable materials: suitable for most metal plates, especially for: carbon steel plate, stainless steel plate, aluminum plate magnesium plates copper plate and zinc plate.
- 1. Fix the metal plate on the mold table.
- 2. The upper punch falls vertically to force the metal plate to form inside the mold.
- 3. The punch rises, and the parts are taken out waiting for the next trimming and polishing process. The whole process is about 1s-1min.
Recently, the newly listed Hongmi Note3 uses the metal back cover made by stamping process.
One of the direct benefits of stamping is cost saving, without nano injection molding, direct anodic oxidation after grinding, mass production climbing quickly; But the disadvantage of this technology is that the upper and lower ends of the fuselage must be plastic splicing. It is impossible to make a complex internal structure and can only be used to make a back cover.
What is CNC?
CNC is commonly known as “CNC Machine Tool”, that is, automatic machine tool controlled by program. The control system can logically process programs with control codes or other symbolic instructions. Through computer decoding, the machine tool can perform the specified actions, A piece of original metal plate is processed through long-time precision processing, and finally the desired shape is made.
CNC metal integrated molding, that is, Unibody integrated molding machine body technology. First, it was used in Apple iPod,iPad and MacBook, and finally it was realized in the iPhone5 generation, starting to lead the wave of all-metal mobile phones.
iPhone5 and 6 adopt aluminum alloy integrated molding, that is, the body and frame are all made of a whole piece of aluminum alloy CNC processing, but considering the RF signal problem of the mobile phone, the body will be divided into several segments, generally, partition such as injection molding is selected at the upper and lower ends.
In order to obtain a higher quality appearance, surface treatments such as positive oxidation, sandblasting and polishing will also be carried out to achieve unique color and smooth touch.
Source: China Flanges Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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