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Basic knowledge of machine tools

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Date: 2017-03-18

 

一  Definition of machine tools

 

The machine is a machine for machining blanks or workpieces of metal or other materials to obtain the desired geometry, dimensional accuracy and surface quality.

Mechanical parts are usually machined from machine tools. Machine is the machine to create the machine, but also to create the machine itself machine, which is different from other machine machine main features, so the machine is also known as the machine tool or machine tool.

 

二  Classification of machine tools

 

Metal cutting machine tools, mainly for the metal cutting;

Woodworking machine for cutting wood

Special processing machine tools, with physical, chemical and other methods of special processing of the workpiece;

Forging machinery. Narrow the machine tool only refers to the use of the most extensive, the largest number of metal cutting machine.

 

1. Metal cutting machine can be divided according to different classification methods for a variety of types.

1.1 Machining method or processing object can be divided into lathe, drilling machine, boring machine, grinding machine, gear machining machine, threading machine, spline processing machine, milling machine, planer, cutting bed, broaching machine, special processing machine, The Each class is divided into several groups according to its structure or processing object, each group is divided into several types.

 

1.2 According to the size of the workpiece and machine weight can be divided into instrumentation machine tools, small and medium-sized machine tools, large machine tools, heavy machine tools and super heavy machine;

 

1.3 According to the processing accuracy can be divided into ordinary precision machine tools, precision machine tools and high-precision machine tools;

 

1.4 according to the degree of automation can be divided into manual operation machine tools, semi-automatic machine tools and automatic machine tools;

 

1.5 According to the machine automatic control mode, can be divided into profiling machine tools, program control machine tools, digital control machine tools, adaptive control machine tools, machining centers and flexible manufacturing systems;

 

1.6 According to the scope of application of the machine, can be divided into general, specialized and special machine tools.

 

1.7 There is an automatic or semi-automatic machine tool consisting of a standard universal component, with a small number of special parts designed according to the specific shape or process of the workpiece, called a combination machine.

 

1.8 One or several parts of the processing, according to the process has arranged a series of machine tools, and with automatic loading and unloading device and machine tools and machine tool between the automatic transmission device, such a group of machine tools called cutting automatic production line.

 

1.9 flexible manufacturing system is a group of digital control machine tools and other automated technology and equipment, with electronic computer control, can be automatically processed with different processes of the workpiece, can adapt to multi-species production.

Machine tool is the basic production equipment of the machinery industry, its variety, quality and processing efficiency directly affect the other machinery products, production technology and economic benefits. Therefore, the modernization level and scale of the machine tool industry, as well as the number and quality of the machine tools owned is one of the important signs of national industrial development.

 

三  Development of machine tools a brief history

 

More than two thousand years BC tree lathe machine is the earliest prototype of the machine. Work, the bottom of the foot rope ring, the use of the flexibility of the branches so that the workpiece driven by the rope rotation, hand shells or stone as a tool, along the slat moving tool cutting the workpiece. The use of the medieval elastic rod bar is still the principle.

 

The fifteenth century due to the need to manufacture watches and weapons, there have been used in the watchmaker's thread lathe and gear machining machine, and the water-driven barrel boring machine. In 1500 or so, the Italian Leonardo da Vinci had drawn a sketch of the design of lathes, boring machines, threading machines and internal grinding machines, including cranks, flywheels, necklips and bearings and other new institutions. China's Ming Dynasty published "Heavenly Creations" also contains the structure of the grinder, with the pedal method to make the iron plate rotation, plus sand and water cut jade.

 

The industrial revolution of the eighteenth century contributed to the development of machine tools. In 1774, the British Wilkinson invented a more sophisticated barrel boring machine. The following year, he used this barrel boring machine boring out of the cylinder, to meet the requirements of the Watt steam engine. In order to boring larger cylinders, he created a water turbine-driven cylinder boring machine in 1776 to promote the development of the steam engine. Since then, the machine has been driven by a steam engine through a day shaft.

 

In 1797, the British Mozi Li made the lathe by the screw drive tool holder, to achieve motor feed and turning thread, which is a major change in the machine structure. Mozzley is also known as the "father of the British machine tool industry."

The 19th century, due to the promotion of textile, power, transportation machinery and arms production, various types of machine tools have emerged. In 1817, the British Roberts created gantry planer; 1818 American Whitney made horizontal milling machine; in 1876, the United States made universal cylindrical grinder; 1835 and 1897 and has invented hobbing machine and gear machine.

 

With the invention of the motor, the machine started to use the motor drive, and then widely used a separate motor drive. At the beginning of the twentieth century, in order to process the higher precision of the workpiece, fixture and thread processing tools, have created a coordinate boring machine and thread grinder. At the same time in order to meet the automobile and bearing industries and other large-scale production needs, but also developed a variety of automatic machine tools, copy machine tools, combined machine tools and automatic production lines.

 

With the development of electronic technology, the United States in 1952 developed into the first digital control machine; 1958 developed into automatic replacement tools for multi-process processing of the processing center. Since then, with the development of electronic technology and computer technology and application of the machine in the drive mode, control systems and structural functions, etc. have undergone significant changes.

 


四   Working of the machine

 

Machine tool cutting is the relative movement between the tool and the workpiece to achieve, and its movement can be divided into two types of surface movement and auxiliary movement.

 

The surface forming movement is such that the workpiece obtains the desired surface shape and size of the movement, which includes the main movement, the feed movement and the cutting movement. The main movement is the main movement when the excess material is peeled off from the workpiece blank. It can be the rotation of the workpiece (such as turning), linear motion (such as planing on the planer), or it can be the rotation of the tool Milling and drilling) or linear motion (such as cutting and broaching); feed movement is the tool and the workpiece to be processed part of the relative movement, so that the cutting can continue to exercise, such as turning the outer ring when the knife slide along the machine guide Such as the movement of the cutting tool is to cut the surface of the workpiece a certain depth of movement, its role is in each cutting stroke from the workpiece surface to cut a certain thickness of the material, such as turning the outer ring when the small knife cut into the horizontal movement.

 

The auxiliary movement mainly includes the rapid approaching and exiting of the tool or the workpiece, the adjustment of the position of the machine parts, the indexing of the workpiece, the position of the tool holder, the feeding material, the starting, the shifting, the commutation, the stop and the automatic tool change.

 

Various types of machine tools are usually composed of the following basic parts: support components for the installation and support of other components and workpieces, to withstand its weight and cutting force, such as beds and columns; variable speed mechanism for changing the speed of the main movement; Mechanism, used to change the feed; spindle box for the installation of machine tool spindle; tool holder, knife library; control and control systems; lubrication system; cooling system.

Machine accessory equipment, including machine tool loading and unloading devices, robots, industrial robots and other machine tools, as well as chuck, sucker spring chuck, vise, rotary table and sub-head machine accessories.

 

Evaluation of machine tool performance indicators can ultimately be attributed to the processing accuracy and production efficiency. The machining accuracy includes dimensional accuracy of the workpiece, shape accuracy, position accuracy, surface quality and machine tool precision retention. The production efficiency involves cutting time and auxiliary time, as well as the degree of automation of the machine and the reliability of the work. These indicators depend, in turn, on the static characteristics of the machine, such as static geometric accuracy and stiffness, and on the other hand with the dynamic characteristics of the machine, such as motion accuracy, dynamic stiffness, thermal deformation and noise.

 


五 Furture development trend of machine tools

 

Further application of electronic computer technology, new servo drive components, grating and optical fiber and other new technologies to simplify the mechanical structure, improve and expand the function of automation work, so that the machine adapt to the work into the flexible manufacturing system;

 

Improve the power of the main movement and feed the speed of movement, the corresponding increase in the structure of the dynamic and static stiffness to adapt to the needs of the use of new tools to improve the cutting efficiency;

 

Improve the processing accuracy and the development of ultra-precision machining machine tools to meet the needs of new industries such as electronic machinery, aerospace; the development of special processing machine tools to meet the difficult processing of metal materials and other new industrial materials processing

 

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