The material removal manufacturing process involves cutting off excess material from a workpiece in a certain way to obtain the desired shape and size of the part. This type of process requires sufficient excess material on the surface of the workpiece. During the material removal process, the workpiece gradually approaches the shape and size of the ideal part. The greater the difference in shape and size between raw materials or blanks and zero h, the more materials are removed, the greater the material loss, and the more energy is consumed during the processing. Sometimes the volume of material lost even exceeds the volume of the part itself.

Although the material removal process has a low material utilization rate, it is still the main means to improve the quality of parts and has strong processing adaptability, making it the most widely used processing method in machine manufacturing. The combination of material removal process and material forming process can greatly reduce the consumption of raw materials. With the development of cutting technology (precision casting, precision forging, etc.), the utilization rate of materials can be further improved. When the production quantity is small, in order to reduce the investment in material forming technology, it is also economically reasonable to simply use material removal technology.

There are many processing forms for material removal, including traditional cutting and special machining.

Cutting machining is a process method that uses metal cutting tools to remove excess metal from workpieces (blanks) on a machine tool, in order to make the shape, size, and surface quality of the workpiece meet the design requirements. During the cutting process, the cutting tool and workpiece are installed on the machine tool and driven by the machine tool to achieve a certain pattern of relative motion. During the relative motion between the tool and the workpiece, excess metal is cut off, forming the machined surface of the workpiece. Common metal cutting methods include turning, milling, planing, broaching, grinding, etc. During metal cutting, there are phenomena such as force, heat, deformation, vibration, and wear. There is a certain influence on the machining process and quality. The key content of this book is to accurately select machining methods, machining machines, tools, fixtures, and cutting parameters, improve machining quality, and enhance machining efficiency.

Special processing refers to the processing method of using electrical energy, light energy, etc. to remove materials from workpieces. There are electrical discharge machining, electrochemical machining, laser processing, etc. Electrical discharge machining (EDM) is the process of using the pulse discharge phenomenon generated between the tool electrode and the electrode to erode the workpiece material and achieve the machining goal. During processing, there is a certain discharge gap between the workpiece electrode and the tool electrode without direct contact, and there is no force during processing. It can process conductive materials with any mechanical properties. Its main advantage in terms of technology is that it can process the inner contour surface of complex shapes, converting its processing difficulty into the processing of the outer contour (work piece), so it plays a special role in mold manufacturing. Due to the low metal removal rate of electrical discharge machining, it is generally not used for shape machining of products. Laser processing and ion beam processing are often used for fine machining.

With the advancement of science and technology, in the fields of aerospace and computer, some parts with particularly high machining accuracy and surface roughness requirements require precision machining and ultra precision machining. The dimensional accuracy achieved by precision and ultra precision machining can reach sub micron or even nanometer level. These processing methods include ultra precision turning, ultra precision grinding, etc.

2、 Material forming and manufacturing process (10m=0)

The material forming manufacturing process often utilizes models to form raw materials into parts or blanks. In the process of material fragmentation, the shape, size, microstructure, and even bonding state of the raw materials will change. Due to the generally low forming accuracy, material forming manufacturing processes are commonly used to manufacture blanks. It can also be used to manufacture parts with complex shapes but low precision requirements. The production efficiency of material forming technology is relatively high. The commonly used forming processes include casting, forging, powder metallurgy, etc.

（1） Casting

Casting is the process of pouring liquid metal into a mold cavity that is suitable for the shape and size of the part, cooling and solidifying to obtain a blank or part. The basic process includes shaping, melting, pouring, cleaning, etc. Due to the influence of filling capacity, shrinkage, and other factors during alloy casting, castings may have uneven microstructure, shrinkage, thermal stress, and deformation, resulting in low precision, surface quality, and mechanical properties of the castings. However, due to its strong adaptability and low production cost, casting and processing are still widely used. The rough parts with complex shapes, especially those with complex inner cavities, are often cast.

The commonly used casting methods in production currently include ordinary sand casting, investment casting, metal casting, pressure casting, eccentric casting, etc. Among them, ordinary sand casting is the most widely used.

（2） Forging and pressing

Forging and sheet metal stamping are collectively referred to as forging. Forging is the use of forging equipment to apply external force to the heated metal for plastic deformation, forming a blank of parts with a certain shape, size, and structural properties. The internal structure of the forged blank is dense and uniform. The reasonable distribution of metal flow lines improves the strength of the parts. Therefore, forging is commonly used to manufacture blanks of parts with high requirements for comprehensive mechanical properties.

Forging can be divided into free forging, model forging, and tire die forging.

Free forging is the process of plastic deformation of metal by placing it between the top and bottom of the supporting iron, utilizing the low vorticity and accuracy of the freely flowing material. Generally used for producing forgings with small batches and simple shapes.

Model forging is the process of deforming metal by placing it in the die chamber of a forging die. The plastic flow of metal is limited by the die chamber, resulting in high forming efficiency, high precision, and a more reasonable distribution of metal flow lines. But due to the high cost of mold manufacturing, it is usually used for large-scale production. The forging force required for forging the Free Slightly Yujiu caries model is large and cannot be used for forging large forgings.

Mold forging is the process of forging metal using a mold on a free forging equipment. Mold manufacturing is simple, cost-effective, and easy to form, but the forming accuracy is not high. It is commonly used to produce small forgings with low precision requirements.

Sheet metal stamping refers to the use of dies on a machine to press sheet metal into various shapes and sizes of parts. Stamping processing has extremely high productivity and precision, and its processing forms include punching, bending, deep drawing, forming, etc. Punching is the process of stamping sheet metal into various flat parts. Bending, deep drawing and other forming processes stamp the sheet metal into various three-dimensional parts. Sheet metal stamping has challenges in electrical products, light industrial products, and automotive manufacturing τ Humiliation

（3） Powder metallurgy

Powder metallurgy is a process that uses metal powder or a mixture of metal and non-metal powder as raw materials, and through processes such as mold pressing and sintering, to manufacture certain metal products or materials. It can produce both special metal materials and metal parts with minimal or no cutting processing. The utilization rate of powder metallurgy wheel can reach 95%, which can significantly reduce the investment in cutting and production costs, and therefore has been increasingly widely used in mechanical manufacturing. Due to the high price of powder materials used in powder metallurgy, the flowability of the powder during forming is poor, and the shape and size of the parts are limited to a certain extent. There are a certain amount of small pores inside powder metallurgy parts, and their strength is about 20% to 30% lower than that of castings or forgings, and their plasticity and toughness are also poor.

The process flow of powder metallurgy production includes powder preparation, mixing ingredients, pressing forming, sintering, shaping, etc. The preparation and mixing process of the powder is usually completed by the manufacturer who provides the powder.

3、 Material accumulation manufacturing process (10m>0)

The material accumulation manufacturing process is the gradual accumulation and growth of parts in a microelement stacking manner. In the manufacturing process, the three-dimensional solid model data of the parts is processed by computers to control the accumulation process of materials and form the required parts. The advantage of this type of process method is that it can form any complex shaped part without the need for production preparation activities such as cutting tools and fixtures.

The prototype produced can be used for design evaluation, bidding, or sample display. Therefore, this process is also known as rapid prototyping technology. Rapid prototyping technology is used for the manufacturing of product samples, molds, and a small number of parts, becoming an effective technology to accelerate new product development and achieve parallel engineering, enabling enterprises to quickly respond to the market and improve their competitiveness.

The development of rapid prototyping technology is very rapid, and now there are several methods that have entered the application stage, mainly including stereolithography (SL: Stereolithography), laminated object manufacturing (LO M: LaminatedObject Manufacturing), laser selective sintering (SLS: Selec-tive Laser Sintering), and melt deposition molding (FD M: Fused)

Deposition Modeling, in which UV curing is the earliest commercial application of rapid prototyping technology (as shown in the figure below).

As shown in the figure, the photopolymerization method uses photosensitive resin as the raw material, and scans the liquid resin point by point with a computer-controlled ultraviolet laser at a predetermined section of the part, causing the resin thin layer in the scanned area to undergo photopolymerization reaction, thereby forming a thin layer cross-section of the part. After one layer is cured, the tray descends by a thin layer height. Apply a new layer of liquid resin on the surface of the previously cured resin for the next scan curing. The newly cured layer is firmly bonded to the previous layer, repeating this process until the entire prototype of the part is manufactured.