Mechanical processing

Machining is a process in which the dimensions or properties of the workpiece are changed by machining machinery. According to the processing of the workpiece in the temperature state, divided into cold processing and hot processing. Generally processed at room temperature, and does not cause the chemical or phase changes of the workpiece, called cold processing. Generally in higher or lower than normal temperature processing, will cause the chemical or phase changes of the workpiece, called thermal processing. Cold processing can be divided into cutting and pressure processing according to the difference of processing methods. Heat treatment, calcination, casting and welding are common in hot processing.

In addition, hot and cold treatment is often used during assembly. For example, when bearings are assembled, the inner ring is often cooled in liquid nitrogen to shrink the size, and the outer ring is appropriately heated to enlarge the size, and then assembled together. The outer ring of the train wheel was also heated to the substrate and cooled to ensure that it held together (this method is still used in the transfer of some parts).

Mechanical processing includes: filament power winding, laser cutting, heavy processing, metal bonding, metal drawing, plasma cutting, precision welding, roll forming, sheet metal bending forming, die forging, water jet cutting, precision welding, etc.

Mechanical processing: the broad meaning of mechanical processing refers to the process of manufacturing products by mechanical means; The use of lathes, milling machines, drilling presses, grinders, punchers,

Development status of micro machining technology abroad

In 1959, Richard P Feynman(winner of the 1965 Nobel Prize for Physics) proposed the idea of a micro-machine. In 1962, the first silicon micro pressure sensor came out, and then developed the size of 50 ~ 500μm gear, gear pump, pneumatic turbine and coupling parts and other micro machinery. In 1965, Stanford University developed a silicon brain electrode probe, later in the scanning tunneling microscope, the success of micro sensors. In 1987, the University of California, Berkeley, USA, developed a silicon micro-static motor with a rotor diameter of 60 ~ 12μm, which showed the potential of using silicon micro-machining technology to manufacture small movable structures and compatible with integrated circuits to manufacture micro-systems.

Miniature machinery has been attached great importance to by government departments, enterprises, colleges and universities and research institutions abroad. In the late 1980s, 15 scientists from MIT, Berkeley, Stanford\AT&T in the United States proposed "Small Machines, Big Opportunities: Report on emerging field - micro dynamics of "national proposal, claiming that" due to the urgency of the micro kinetics (micro system) in the United States, shall be in such a new important technology ahead of competition with other countries ", suggested that the central government in advance cost $50 million for five years, get leadership attaches great importance to the United States, to invest heavily in a row, Aerospace, information and MEMS as the three key points of science and technology development. NASA's $100 million investment to develop "discovery", the national science foundation, the MEMS as a new research field developed financing of micro electronic mechanical system research plan, starting in 1998, funded MIT, university of California, 8 universities and bell LABS in the research and development of this field, Annual funding increased from $1 million and $2 million to $5 million in 1993. The US Department of Defense Technology Plan report released in 1994 listed MEMS as a key technology project. DARPA actively leads and supports MEMS research and military applications, and has established a MEMS standard process line to facilitate research and development of new components/devices. The U.S. industry is focused on sensor-related research in sensors, displacement sensors, strain gauges, and accelerometers. Many institutions are involved in the research of micro-mechanical systems, such as Cornell University, Stanford University, the University of California, Berkeley, the University of Michigan, the University of Wisconsin, and the Old Lunzdemore National Research Institute. The University of California Berkeley Sensor and Acutor Center (BSAC) has built a 1,115m2 ultra-clean laboratory to research and develop MEMS after receiving 15 million yuan from the Ministry of Defense and more than a dozen companies.

In 1991, Japan's MITI began a 10-year, Y25bn micro-research programme to develop two prototypes, one for medical, intrapersonal diagnostic and micro-surgery, and the other for industrial repair of tiny cracks in aircraft engines and atomic equipment. Dozens of institutions, including the University of Tsukuba, Tokyo Institute of Technology, Tohoku University, Waseda University and Fujitsu Research Institute, are participating in the project.

European industrial developed countries successively to the micro system focuses on the research and development investment, Germany since 1988 micro processing ten-year plan projects, the Ministry of Science and Technology in 1990 ~ 1993 40000 mark support "micro systems program" research, and micro system as the focus of the development of science and technology at the turn of the century, the German pioneering journalist on technology, It provides a new technical means for the development of MEMS, and has become the preferred process for 3D structure fabrication. France's 70 million franc "Microsystems and technology" project, launched in 1993. The EC forms the "multifunctional Microsystems research network NEXUS", which co-ordinate research in 46 institutes. Switzerland has also invested in MEMS development on the basis of its traditional watchmaking industry and small precision machinery industry, with an investment of $10 million in 1992. The British government has also set up a nanoscience programme. List 8 research and development projects in the fields of mechanics, optics, electronics, etc. In order to strengthen European efforts to develop MEMS, a number of European companies have formed MEMS development groups.

At present, a large number of micro machines or micro systems have been studied, such as: The micro tweezers with a tip diameter of 5μm can pick up a red blood cell, the micro pump with a size of 7mm×7mm×2mm can drive a car with a flow rate of 250 μL /min, the robotic butterfly can fly in the magnetic field, and the micro inertial combination (MIMU) which combines a micro speedometer, a micro gyro and a signal processing system. Germany invented the Liga process, which makes cantilever beams and actuators, as well as micro-pumps, micro-nozzles, humidity and flow sensors, and a variety of optical devices. California Institute of Technology (Caltech) has glued a considerable number of 1mm micro beams onto aircraft wing surfaces to control their bending angles to affect the aerodynamic characteristics of the aircraft. The silicon accelerometer produced in mass production in the United States integrates the micro sensor (mechanical part) and the integrated circuit (electrical signal source, amplifier, signal processing and positive circuit, etc.) together in the range of 3mm×3mm on the silicon chip. A few centimeter square micro lathe developed by Japan can process a fine shaft with a precision of 1.5μm.

Production process and technological process

Production process refers to the whole process of making products from raw materials (or semi-finished products). In terms of machine production, it includes transportation and storage of raw materials, preparation for production, manufacture of blank, processing and heat treatment of parts, assembly and debugging of products, painting and packaging, etc. The content of production process is very extensive. Modern enterprises use the principles and methods of system engineering to organize production and guide production, and regard the production process as a production system with input and output. Can make the management of the enterprise scientific, make the enterprise more resilient and competitive power

In the production process, the direct change of raw materials (or blank) shape, size and performance, so that it into the finished product process, known as the process. It is an essential part of the production process. Such as blank casting, forging and welding; Heat treatment to change material properties [1]; Mechanical processing of parts, etc., belong to the process. The technological process is composed of one or several sequential operations. [1]

Working procedure is the basic component unit of technological process. So-called working procedure is to point to in a working place, to one or a group of work parts of the continuous completion of that part of the technological process. The main characteristic of a working procedure is not to change the processing object, equipment and operator, and the content of the working procedure is completed continuously.

Production Types Production types are generally divided into three categories

1. To produce a part singly, with little repetition.

2. Batch production Production in which batches of identical parts are made.

3. Bulk production When products are manufactured in large quantities, most workplaces often repeat a process for a part of the product.

When drawing up the process of parts, because the production type of parts is different, the method of adding, machine tools, measuring tools, blank and the technical requirements for workers are very different.

General principles for developing process routes

The formulation of machining process rules can be roughly divided into two steps. First of all, it is to formulate the process route of parts processing, and then determine the working procedure size of each working procedure, the equipment and process equipment and cutting specifications, man-hour quota, etc. These two steps are interrelated and should be analyzed comprehensively.

The formulation of the process route is to formulate the overall layout of the process, the main task is to choose the processing methods of each surface, determine the processing sequence of each surface, as well as the number of the number of work in the whole process.

General principles for developing process routes

1, the first processing datum

Parts in the process of processing, as a positioning datum surface should be processed first, in order to provide precision datum as soon as possible for the processing of the subsequent procedures. It's called "benchmark first."

2. Divide the processing stage

Processing quality requirements of the surface, are divided into processing stages, generally can be divided into rough machining, semi-finishing and finishing three stages. Mainly in order to ensure the quality of processing; Conducive to reasonable use of equipment; Easy to arrange the heat treatment process; As well as facilitate the discovery of blank defects.

3. First face and then hole

[1] For box body, support and connecting rod and other parts should be processed first plane and then machining holes. In this way, the plane can be positioned to process the hole, to ensure the accuracy of the plane and the hole position, but also to the plane of the hole processing to bring convenience.

4, finishing processing

Main surface finishing processing (such as grinding, honing, fine grinding, rolling processing, etc.), should be in the last stage of process route, after processing the surface finish in Ra0.8 um above, slight collision will damage the surface, in countries such as Japan, Germany, after finishing processing, with a flannelette, absolutely no direct contact with the workpiece or other objects with the hand, In order to avoid finishing the surface, due to the process between the transfer and installation of damage.

(2), reasonable selection of equipment. Rough machining is mainly to cut off most of the machining allowance, does not require a higher machining accuracy, so the rough machining should be carried out on the machine tool with greater power and less precision, and the finishing process requires a more high-precision machine tool processing. Rough and fine machining are processed on different machine tools, which can not only give full play to the capacity of equipment, but also extend the service life of precision machine tools.

(3), in the machining process route, often arrange a heat treatment process. The arrangement of the position of the heat treatment process is as follows: in order to improve the cutting performance of the metal, such as annealing, normalizing, tempering and so on, it is generally arranged before machining. In order to eliminate internal stress, such as aging treatment, tempering and tempering treatment, generally arranged after rough processing, before finishing processing. In order to improve the mechanical properties of parts, such as carburizing, quenching, tempering, etc., generally arranged after mechanical processing. If there is a large deformation after heat treatment, the final processing procedure must be arranged

Common processing equipment

In the process of precision machining will be useful for many equipment, the following list of some commonly used mechanical equipment: Such as wire cutting, edm machine, deep hole discharge machine, CNC grinding optical projection, tool grinding machine, universal grinding machine, NC grinding coreless grinder, surface grinder, internal diameter, precision surface grinding machine, precision forming grinder, 1 water, NC milling machine, grinding machine, machining center, PVD titanium plating machine, laser welding machine, coking water cleaning machines, cylindrical grinding machine, vacuum hot place Furnace and so on.