What Metal Processing Techniques are There?

The material forming method is a key factor in the material processing process, involving design, performance, cost, quality, effect, yield, production cycle, etc. What are the process characteristics of metal materials?

Several common metal processing methods:

• Casting :

Due to the characteristics of metal melting, pouring liquid metal into a mold to condense and solidify casting has always been one of the main processing methods. Common execution methods are sand turning, dewaxing, gravity, centrifugal or pressure casting.

The advantage of casting that is difficult to replace is that it is almost unlimited in terms of shape, raw material type and size, especially for objects with complex inner cavity shapes; investment in equipment is relatively low, and waste recycling is easy. Castings can have high hardness, but generally the surface fineness and mechanical properties are poor, and the scrap rate is high.

Casting is widely used in many objects, such as metal knives and forks, pots and pans, iron plates, etc., which are all cast by various techniques, and then matched with back-end processing and decoration. The use of sanding or dewaxing can also perform small batch production or proofing, especially suitable for objects with complex inner shapes and closed shapes or tricky shapes.​

• Forging :

Using the ductility of the metal, the raw material ingot or sheet is directly beaten or rolled until it is formed. Almost all forming methods other than casting and machining are extensions of forging technology.

Forgings generally have good mechanical properties. The heavy-duty machine-based process also has the advantages of saving raw materials and rapid production; manual-based free forging has extremely high flexibility and is suitable for development or small production of high-unit price art. Relatively speaking, if it is not a small item produced by manpower, the production of forged parts will require processing equipment with huge capital, and considering the utilization rate, the shape is not as free as casting.

The forging process densifies the crystal structure of the metal, making the object thin and strong. In manual hammer forging, this feature can improve the soft properties of some chemically stable or high-value metals, such as gold, silver, copper or tin.

Manual forging is suitable for precious metals with good ductility, and can be customized according to the design shape. In addition to large forging machines and dies, industrial forging generally combines many chain quenching techniques. It is mostly used for mechanical parts with high strength requirements, such as train wheels or ship engine drive shafts.

• Spinning:

Spinning is a process in which a cutter wheel and a tool are driven manually or by a machine, and the metal sheet is gradually pushed into the rotating mold to form, which can greatly improve the efficiency of manufacturing axisymmetric circular objects. Although it has been largely replaced by mature stamping technology, it still has its own unique advantages.

The spinning-formed object will have stronger mechanical properties, and the billet will be stretched to a greater extent, so it is not easy to tear. The cost of the mold is low, and generally only one core mold is needed to make it; the requirements for materials and machines are also low, and a lathe is often used instead of a spinning machine.

Spinning requires less process equipment than stamping, but it is mostly made manually, which is less efficient. Suitable for many items but small batch production. In industrial mass production, automatic machines are often used for crimping or necking processing of stamped objects. But when forming thin products, skilled labor can get a better surface appearance than machines. Large pieces of hand-spinning are currently common in copper and aluminum products, such as copper pots, brass instruments, cymbals or large aluminum lamp shades.

• Stamping :

The mass production of modern metal products is based on the application of stamping technology, and the process can be mainly divided into punching, bending and drawing.

Stamping generally has two upper and lower dies. After the plate is placed in the middle and pressed, the deformation, cutting or joining can be completed, and then the object is completed. It is most commonly used for bending, punching, shape cutting or extruding ridges to increase structural strength of sheet metal components, and can even directly punch out decorative patterns; however, these are almost all bending and forming of flat materials, which will not significantly affecting the thickness of the material can be imagined as a more complicated origami.

Extension forming (or deep drawing, deep extension) is a special project. It can extend a flat plate into a three-dimensional hollow body, and the extension process will change the wall thickness. It is an important process that greatly replaces traditional spinning in mass production.

Good stamping parts are light in weight but high in rigidity, fast in mass production, and very uniform in quality. There are strict requirements for molds in the manufacturing process, especially composite molds or continuous molds that combine multiple processes, and the cost is even higher, which is suitable for large-scale and single-type production. From home appliances, car casings, thermos bottles, trays and other small things, as long as you see objects shaped like metal sheets on the market, almost all of them are mass-produced by stamping.

• Die Casting:

Die casting is a method of injecting molten metal into an alloy steel mold using pressure. The method is somewhat similar to plastic injection molding. It can produce finely shaped objects at one time, so it is widely used in metal manufacturing. The mold of the alloy steel mold is made by machining, and the materials used are mainly zinc, copper, aluminum, magnesium, lead, tin and their alloys, mainly those with compression resistance, corrosion resistance and high plasticity. It is easy to die cast into parts, and because the melting point of iron is too high, the material is usually free of iron. According to the different melting points of the die-casting metal, it is divided into two types of die-casting machines, cold and hot chambers, to die-cast objects. Common die-cast items such as auto parts, medical equipment, lighting parts, motor parts, etc., are complex and finely shaped items.

• Metal 3D Printing:

The cost of molds and tools for metal processing is very high, and there are many limitations in the existing process. Metal printing is a project with high potential in 3D forming, which greatly reduces the cost of development and correction, and does not have the problem of weak casting strength when making complex and organic shapes.

In addition to accelerating development and challenging more diverse shapes, metal 3D printing is particularly effective in medical or aerospace technology, such as re-bonding or joint repair, where the most suitable ones can be freely printed according to the patient's condition or wound contour. The shape, combined with the honeycomb structure to reduce the weight, is not easy to achieve by traditional processing methods.