Brief analysis of common metal working technology
Casting | Casting
Casting is a kind of metal hot processing technology which was mastered earlier by human beings. It is one of the basic processes of modern machinery manufacturing industry. Because the casting blank is nearly formed, it achieves the purpose of free machining or a small amount of machining, which reduces the cost and reduces the time to a certain extent.
Metal casting is to pour molten metal liquid into a hollow casting mold made of high-temperature resistant materials, and then get the desired shape after condensation. The resulting product is the casting.
Classification of casting
A |, Gravity Casting Gravity Casting
Is refers to the metal liquid in the earth under the action of gravity into the casting process, also known as casting. The metal liquid is generally poured into the gate manually, and the product is obtained by filling the mold cavity, exhaust, cooling and mold opening with the weight of the metal liquid.
Gravity casting has the advantages of simple process, low mold cost, less internal pores, heat treatment and so on, but at the same time, it has poor compactness, slightly poor strength, unsuitable for the production of thin-walled parts, low surface finish, low production efficiency and high cost.
Second, the pressure Casting (Die Casting) | Die Casting
A method of making liquid or semi-liquid metal fill the cavity of a die casting mold at a higher rate under high pressure and forming and solidifying under pressure to obtain a casting.
High pressure casting can quickly fill the mold, high production efficiency, good product density, high hardness, good surface finish, can produce thin wall parts; At the same time as a result of high pressure air for filling, internal involved in the gas is more, easily formed in product internal porosity, therefore can't heat treatment (heat treatment of internal gas will expand, prompted a bulge or crack defects such as product) and late/excessive machining (avoid through dense surface layer, exposing subcutaneous blowhole, cause the workpiece scrap).
However, it is difficult to make smooth aluminum oxide film in ordinary aluminum die casting process. The reason is that silicon is added to the material in order to increase the flow of the material through all areas of the mold. As a result, if you want to color aluminum die castings, they may lose their upscale appearance after coating because they look like plastic.
Die casting process is applied to mobile phones, but because the surface can not be anodized, most enterprises use spray treatment;
Forging | Forging
Forging is one of the methods of metal pressure working. Refers to the use of pressure to change the shape of metal raw materials, to obtain a certain mechanical properties, shape and size of the forgings of a processing technology.
Classification of forging
1, hammering, or while the iron is hot | Hammer or Smith Forging
In the same way as hammer forging or blacksmithing, the work is heated to forging temperature and forged between the flat hammer and the drill plate. Small pieces can be called blacksmithing by hand; Steam Hammers are used for larger items.
Among them, the work is placed between the drill plate and the plane hammer, as for the structure of the steam hammer, it depends on the forging capacity, the light for the single frame type, the heavy for the double frame type.
2, Drop Forging | Drop Hammer Forging
The difference between drop forging and plane forging is that the hammer of drop forging has a die hole, and the working parts bear two aspects of pressure or impact force in the die hole, and then make plastic deformation according to the shape of the die hole. As shown in the figure below, in order to make the metal flow can be true and sufficient, forging is often divided into several levels, the change of each level is progressive, in order to control the direction of flow, as for the number of series, the end of the forging shape and size, metal malleability and workpiece size precision requirements.
3, pressure Forging (Forging) | Press Forging
Pressure forging is a forging method that makes the metal extruded in the mold at a slow speed. Because the metal forces for a long time, the extrusion effect is not only applied to the forging surface, but also to the center part of the workpiece. Therefore, it can achieve the effect of uniform inside and outside, and the quality of its products is better than that of hammer forging.
Forging for mobile phone shell manufacturing process can effectively reduce the CNC time, thus the relative cost is low; And can choose more than 95% aluminum alloy, can be anodized. Process: first through forging to get a thick mobile phone structural parts rough shape; CNC milling out the unnecessary part; NMT obtained metal + plastic integrated structure; Anodic oxidation surface treatment; Finally, glue the antenna cap.
4, Forging or side press Forging | Upset Forging
Roughing or end forging is usually done when one end of a long, uniform bar is to be roughed or shaped, as shown below. The long rod is clamped in the mold, one end is heated to a high temperature, and along its axial direction, and then the end is pressurized to make it rough or shaped.
5, Roll Forging | Roll Forging
The principle of rolling forging is as follows.
With two non-100% round rollers (with a diameter reduction rate of 25~75%, the rest can be cut into groove shape according to need), the rod material is fed into it and clamped, and then continue to rotate, so that the rod material is rolled, the diameter is reduced and pushed forward; When the roll is returned to the open position, the bar material can be pumped back to its original position for a second cycle of rolling, or sent to another groove for another construction.
Metal stamping molding is a kind of metal cold processing method, also known as cold stamping or sheet metal stamping, with the power of stamping equipment, so that the sheet metal in the mold directly force forming, stamping parts are widely used in the manufacturing of automobile parts and household appliances.
Material: Suitable for most metal sheets, especially carbon steel, stainless steel, aluminum, magnesium, copper and zinc
1. Fix the metal sheet on the mold surface
2. The upper punch drops vertically, so that the metal sheet is formed by force inside the mold
3. The punch rises and the parts are taken out to wait for the next trimming and grinding process. The whole process takes about 1s-1min
One of the direct benefits of stamping is to save costs, without nano-injection molding, directly anodic oxidation after grinding, mass production climb quickly; The drawback is that the upper and lower ends of the fuselage have to be plastic. Can not do complex internal structure, can only be used to do the back cover.
CNC | CNC machine tools
CNC commonly known as "CNC machine tools", namely by the program control of automatic machine tools. The control system can logically process the program with the control code or other symbolic instructions. Through the computer decoding, the machine tool can perform the specified action, and a piece of original metal sheet can be made into the desired shape through a long time of precision machining.
CNC metal integral molding, that is, UNIBODY integral molding body process. It was first used in Apple's iPod, iPad, and MacBook, and eventually in the iPhone5 generation, which began to lead the all-metal mobile phone craze. It is also the most commonly used metal working method; The body and frame are made of a whole piece of aluminum alloy CNC. However, considering the RF signal of the mobile phone, the body will be divided into several sections. Generally, the upper and lower ends of the body will be cut off by injection molding. In order to consider the beauty, the previous straight leucorrhea has also become a U-shaped;In order to obtain a higher quality of appearance, will also be positive oxidation, sandblasting, polishing and other surface treatment, resulting in rich color and smooth touch.