There are several popular procedures for machining mechanical components
1.Material removal manufacturing method ((10)m 0)
The material removal manufacturing process involves removing extra material from a workpiece in a specific manner to get pieces of the specified form and size. Such techniques need enough material on the workpiece’s surface. During material removal, the workpiece steadily approaches the shape and size of the ideal component. The bigger the disparity between the form and size of the raw material or blank and the zero h, the more material is removed, the greater the material loss, and the more energy is required in the processing process. Sometimes the volume of material lost surpasses the volume of the portion itself.
Although the material removal process has a poor material utilization rate, it is still the primary way of improving component quality and has good processing flexibility. It is the most often utilized processing technique in the machine manufacturing industry. The material removal process, when paired with the material forming process, may significantly minimize raw material usage. The utilization rate of materials may be enhanced further with the development of less and less cutting processing technologies (precise casting, precision forging, etc.). When the production quantity is modest, it is also affordable and appropriate to just employ the material removal process to reduce the investment in the material forming process.
Traditional machining and specialized machining are two examples of material removal methods.
Machining is the process of removing superfluous metal from a workpiece (blank) using a machine tool so that the form, size, and surface quality of the workpiece fulfil the design criteria. The tool and the workpiece are put on the machine tool and pushed by the machine tool to accomplish a specific regular relative movement throughout the cutting operation. Excess metal is removed during the relative movement of the tool to the workpiece, producing the workpiece’s machined surface.
Turning, milling, planning, broaching, and grinding are all common metal cutting procedures. Force, heat, deformation, vibration, and wear are all phenomena that occur during the metal cutting process. There is an effect on the processing procedure and the processing quality. To increase processing quality and efficiency, it is critical to select the processing technique, processing machine tool, tool, fixture, and cutting settings. This will be the book’s main topic.
Special processing is a method of removing material from a workpiece that use electrical, light, or other forms of energy. EDM, electrolytic machining, laser machining, and other techniques are available. The goal of EDM is to erode the workpiece material by using the pulse discharge phenomena formed between the tool electrode and the electrode. Without direct contact, there is a discharge gap between the workpiece electrode and the tool electrode during milling.
Machining requires no force, and conductive materials of any mechanical characteristics may be machined. In terms of technology, its fundamental benefit is that it can process the inner contour surface of complicated forms and transform the difficulty of processing into the processing of the outward contour, giving it a unique function in mould manufacture. EDM is not commonly utilized for product shape processing due to its poor metal removal rate. Laser and ion beam processing are commonly employed for fine processing.
With the growth of science and technology, some products with particularly high machining accuracy and surface roughness in the aerospace and computer areas demand precision machining and ultra-finishing. Precision and ultra-precision machining can achieve sub-micron or even nano-scale dimensional accuracy. These types of processing include ultra-precision turning, ultra-precision grinding, and so on.
2. Material forming manufacturing process (⑽m = 0)
To transform raw materials into parts or blanks, the material forming manufacturing process mostly employs a model. The form, size, organization state, and even the combination state of raw materials will vary during the material crumb process. Because forming precision is often low, the material forming manufacturing process is frequently utilized to create blanks. It may also be utilized to make parts with complicated forms but lower accuracy demands. The material forming process has a high production efficiency. Casting, forging, powder metallurgy, and other forming methods are commonly utilized.
(1) Casting
Casting is a process in which liquid metal is poured into a mold cavity suitable for the shape and size of the part, and a blank or part is obtained after cooling and solidification. The basic process is modeling, smelting, pouring, cleaning and so on. Due to the influence of mold filling ability, shrinkage and other factors during alloy casting, castings may have uneven structure, shrinkage cavities, thermal stress, and deformation, resulting in poor accuracy, surface quality, and mechanical properties of castings. Nevertheless, casting processing is still widely used due to its strong adaptability and low production costs. Casting is often used for blanks with complex shapes, especially parts with complex inner cavities.
At present, the commonly used casting methods in production include ordinary sand casting, investment casting, metal casting, die casting, centrifugal casting, etc. Among them, ordinary sand casting is the most widely used.
(2) Forging
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 to plastically deform to form a part blank with certain shape, size and microstructure. The internal structure of the forged blank is dense and uniform. The distribution of metal streamlines is reasonable, which improves the strength of the parts. Therefore, forging is often used to manufacture blanks for parts with high comprehensive mechanical properties.
Forging can be divided into free forging, model forging and die forging.
Free forging is to place the metal between the upper and lower irons for plastic deformation of the metal. The use of free-flowing aluminum alloy has low vortex rate and low precision. It is generally used to produce forgings with small batches and simple shapes.
Model forging is to deform the metal in the die cavity of the forging die. The plastic flow of the metal is restricted by the die cavity. The forming efficiency is high, the precision is high, and the metal streamline distribution is more reasonable. However, due to the high cost of mold manufacturing, it is usually used for mass production. The forging force required for forging with the free-slightly Yujiu-Ci model is large, and it cannot be used for the forging of large-scale forgings.
Die forging is to forge metal using die forging on free forging equipment. The tire mold is simple to manufacture, low cost and convenient to form, but the forming accuracy is not high, and it is often used to produce small forgings with low precision requirements.
The die is used on the sheet metal stamping machine to stamp the sheet into various shapes and sizes. Stamping processing is particularly productive and accurate, including processing forms such as blanking, bending, deep drawing, and shaping. The process of punching sheet metal into numerous flat sections is known as blanking. Bending and deep drawing are two forming methods that punch the sheet into distinct three-dimensional components. Sheet metal stamping has a long way to go in the electrical, light industrial, and car industries.
(3) Powder metallurgy
Powder metallurgy employs metal powder or a blend of metal and nonmetal powder as raw materials to create specific metal products or metal materials via mould pressing, sintering, and other procedures. It is capable of producing both specific metal materials and metal pieces with little machining. Because the utilization rate of a powder smelting wheel may reach 95%, it can significantly reduce cutting input and production costs, and it is extensively employed in equipment manufacture.
Due to the high price of powder raw materials used in powder metallurgy, the fluidity 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 number of tiny 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, compounding, pressing, sintering, shaping, etc. The preparation and compounding process of the powder is usually completed by the manufacturer that provides the powder.
3. Material accumulation manufacturing process (⑽m>0)
Material accumulation manufacturing involves gradually accumulating and growing pieces in the form of micro-element superposition. The three-dimensional solid model data of the component is processed by the computer throughout the production process to regulate the accumulation process of the material to make the desired part. The benefit of this sort of process is that it may manufacture portions of any complicated shape without the requirement for production preparatory operations such as tools and fixtures.
Manufactured prototypes are available for design evaluation, bids, or prototype presentations. Therefore, this process is also called rapid prototyping technology. Rapid prototyping technology is used in the manufacture of product samples, mold manufacturing and a small number of parts. It has become an effective technology to accelerate the development of new products and realize concurrent engineering, so that the products of enterprises can quickly respond to the market and improve the competitiveness of enterprises.
The development of rapid prototyping technology is very rapid, and now several methods have entered the application stage, mainly including photocuring method, lamination manufacturing method, laser selective sintering method, and melting stacking modeling method. technology.
The photo-curing method employs photosensitive resin as the raw material, and the computer-controlled ultraviolet laser scans the liquid resin point by point in accordance with the predetermined layered section of the part, causing the thin resin layer in the scanned area to undergo a photopolymerization reaction, resulting in the formation of a thin section of the part. The tray is lowered by a tiny layer height after one layer is cured. For the next scan to cure, apply a new layer of liquid resin on the surface of the previously cured resin. The newly cured layer is securely linked to the preceding layer, and this process is repeated until the entire prototype portion is completed.
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