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The beginning and end of CNC machining aluminum

China’s CNC industry is developing rapidly. The average annual growth rates of domestic CNC machine tool production and consumption from 1998 to 2004 are 39.3% and 34.9% respectively. Nevertheless, the development momentum of imported machine tools is still strong. Since 2002, China has become the largest consumer of machine tools and the largest importer of machine tools in the world for three consecutive years. In 2004, the consumption of machine tools in China reached as high as US $9.46 billion. The gap between domestic CNC machine tool manufacturers and foreign countries in the research and development of high-end and large CNC machine tools is more obvious, with more than 70% of this Class a equipment and the vast majority of functional components are dependent on imports.

It can be seen that the domestic CNC machine tools, especially the high-end CNC machine tools, are still lack of market competitiveness. The main reasons are that the research and development depth of domestic CNC machine tools is not enough, the manufacturing level is still backward, the service consciousness and ability are lack, the CNC system production and application are not promoted effectively, and the CNC talents are lack. We should see clearly the situation, fully understand the shortcomings of domestic CNC machine tools, strive to develop advanced technology, increase technical innovation and training services, so as to shorten the gap with developed countries.

Recently, with China’s economic development, it has also attracted the attention of some major machine tool manufacturers in the world. In 2000, Mazak, the largest machine tool manufacturer, set up a joint venture factory for CNC machine tools in Yinchuan, China. It is said that the manufacturing level is quite high. It is known as an intelligent and network chemical factory, which is synchronized with the world.

At present, the state has formulated some policies to encourage people to use domestic CNC machine tools, and manufacturers are also trying to catch up. CNC aluminum processing is the most popular machine tool in China. In a purchase plan, 80% of the machine tools are imported, so domestic machine tools can not meet the needs. This trend will not change in the next five years. However, as far as the current domestic needs are concerned, China’s CNC machine tools can meet the orders of medium and low-grade products. We should see clearly the situation, fully understand the shortcomings of domestic CNC machine tools, strive to develop advanced technology, increase technical innovation and training services, so as to shorten the gap with developed countries.

According to the relevant report of the United Nations, a new round of economic recession in Europe and North America has dragged down the recovery of the global manufacturing industry. In the third quarter of 2012, the global manufacturing industry grew by 2.2% year on year, and its growth rate was the lowest since 2009. In particular, CNC aluminum processing and the economic growth of developing countries are slowing down. Developed countries as a whole have experienced the first decline in industrial output since 2009. Among them, Germany’s industrial output dropped by 1.7%, Italy’s by 6.2%, France’s by 1.9%, Britain’s by 0.9% and Japan’s by 4.6%.

While the growth of manufacturing industry in the world’s major economic systems has slowed down or declined one after another, the development of related industries has maintained a high growth rate. According to relevant data, the scale of the international machine tool market has more than doubled in the past 20 years, reaching about US $86 billion in 2011. Since the turn of the century, the consumption of machine tools has increased by nearly 10% annually (in US dollars).

High precision machining of CNC parts

For high-precision parts, the processing is very strict. The processing procedures include feed and output. There are specific requirements for the size and accuracy, such as 1 mm plus or minus micrometers. If the size is too wrong, it will become a scrap. At this time, it is equivalent to reprocessing, which is time-consuming and laborious. Sometimes, the whole processing material will be scrapped, resulting in an increase in cost. At the same time, the parts are definitely unusable.
For the processing of high-precision parts, the main requirements are the size, such as the diameter of the cylinder, there are strict requirements, positive and negative errors within the specified range are qualified parts, otherwise they are unqualified parts; There are also specific and strict requirements for length, width and height, as well as positive and negative errors. For example, if the diameter of an embedded cylinder (take the simplest basic parts as an example) is too large and exceeds the allowable error range, it will cause the situation that it cannot be inserted. If the actual diameter is too small and exceeds the lower limit of the allowable negative error, it will cause the problem that it is too loose and not firm. These are all unqualified products, or the length of the cylinder is too long or too short, which is beyond the allowable range of error. They are all unqualified products, and they have to be scrapped or reprocessed, which will inevitably lead to the increase of cost.
The requirement of high-precision parts processing is actually the most important dimension problem. It must be processed in strict accordance with the additional drawing. The actual size will not be exactly the same as the theoretical size of the drawing, but as long as the processing size is within the allowable error range, it is all qualified parts. Therefore, the requirement of precision parts processing is to process in strict accordance with the theoretical size Work.
The second is the advanced precision parts processing equipment and testing equipment. The advanced processing equipment makes the processing of precision parts simpler, higher precision and better effect. The detection device can detect the parts that do not meet the requirements, so that all the products sent to customers can really meet the requirements.

Six advantages of computer gong processing parts

In addition to the characteristics of ordinary milling machine, computer gong processing also has the following six functional advantages:

Parts with strong adaptability and good flexibility, especially complex contour shape or difficult to control size, such as mold parts, shell parts, etc;
It can process parts that can not be processed by ordinary machine tools or are difficult to process, such as complex curve parts described by mathematical models and three-dimensional curved surface parts;
It can process the parts that need to be processed by multiple processes after one clamping and positioning;
High production efficiency, CNC milling machine generally does not need to use special fixture and other special process equipment, when replacing the workpiece, it only needs to call the processing program, clamping tools and adjust tool data stored in the CNC device, thus greatly shortening the production cycle. Secondly, the CNC milling machine has the functions of milling machine, boring machine and drilling machine, which makes the process highly concentrated and greatly improves the production efficiency. In addition, the spindle speed and feed speed of CNC milling machine are continuously variable, so it is beneficial to select the best cutting parameters;
The pulse equivalent of the numerical control device is generally 0.001mm, and the high-precision numerical control system can reach 0.1 μ M. in addition, the numerical control machining also avoids the operation error of the operator;
High degree of production automation, can reduce the labor intensity of the operator. It is beneficial to the automation of production management.

CNC computer gong processing tool requirements

There are specific requirements for the size and accuracy, such as 1 mm plus or minus how many microns, etc. if the size is wrong too much, it will become a scrap. At this time, it is equivalent to reprocessing, which is time-consuming and laborious. Sometimes even the whole processing material will be scrapped, which leads to the increase of cost. At the same time, the parts are definitely unusable.
For the processing of high-precision parts, the main requirements are the size, such as the diameter of the cylinder, there are strict requirements, positive and negative errors within the specified range are qualified parts, otherwise they are unqualified parts; There are also specific and strict requirements for length, width and height, as well as positive and negative errors. For example, if the diameter of an embedded cylinder (take the simplest basic parts as an example) is too large and exceeds the allowable error range, it will cause the situation that it cannot be inserted. If the actual diameter is too small and exceeds the lower limit of the allowable negative error, it will cause the problem that it is too loose and not firm. These are all unqualified products, or the length of the cylinder is too long or too short, which is beyond the allowable range of error. They are all unqualified products, and they have to be scrapped or reprocessed, which will inevitably lead to the increase of cost.
The requirement of high-precision parts processing is actually the most important dimension problem. It must be processed in strict accordance with the additional drawings. The actual size of the processed parts will not be exactly the same as the theoretical size of the drawings, but as long as the processing size is within the allowable error range, they are all qualified parts. Therefore, the requirement of precision parts processing is to process in strict accordance with the theoretical size Line processing.
The second is the advanced precision parts processing equipment and testing equipment. The advanced processing equipment makes the processing of precision parts simpler, higher precision and better effect. The detection device can detect the parts that do not meet the requirements, so that all the products sent to customers can really meet the requirements.

Introduction of computer gong machine tool

1) Casting, which is the most important part of the computer gong, directly affects the accuracy, stability, wear resistance of the computer gong and the service life of the machine tool. After the casting is finished, it is not immediately used in the production. The good casting is that it is after wind and rain, sun exposure, natural weathering, and some of them are soaked in sea water. After the casting does not change, it is taken to the processing. The machine tool made in this way is not easy to change, and can maintain the stability and accuracy of the machine tool for a long time.

2) Spindle, the spindle is used to directly face the workpiece, it is driven by the motor to work, high-speed rotation, the spindle is equipped with a tool handle, it can chip the workpiece, meet various production needs, the quality of the spindle will directly affect the processing accuracy, if the internal bearing is worn, it is easy to cause the swing of the spindle, the accuracy of the processed things naturally has a few deviations . At present, the rotation speed of the main shaft is generally about 8000 rpm, and the high-speed machine can achieve more than 20000 rpm, and each machine has only one main shaft.

3) The screw rod is also a part of the fuselage. It is driven by a servo motor and drives the displacement of the worktable through the copper sleeve of the screw rod to meet the processing needs. If there is a gap in the screw rod, it is also directly reflected in the processing accuracy and finish.

4) There are two kinds of motors: servo motor and frequency conversion motor. The servo motor has good stability, high power of spindle drive motor and low coordination rate of three-axis drive motor.

5) The coupling is installed between the screw rod and the motor, which is just a linkage function.

6) The lubrication cooling system consists of an automatic oil pump, a spindle oil cooler and a chip liquid circulation system. When the machine tool is working, the oil can be pumped once every few minutes, and the oil pipe is connected to every corner, such as screw rod, guide rail, etc. if the oil circuit is blocked, the guide rail will be easily worn and the accuracy will be affected. Spindle oil cooling is a circulating cooling system added to cool the spindle. It is necessary or not for the spindle with 8000 revolutions, and it must be equipped for the spindle with more than 8000 revolutions. In the chip liquid circulation system, the oil in the oil tank is pumped up by the oil pumping motor and flushed to the workpiece being processed.

7) Sheet metal, sheet metal requirements are not too high, as long as there is no oil leakage on the line, but also involves the appearance of beautiful, image problems.

High precision parts manufacturing concept

The concept, significance and characteristics of high precision parts manufacturing high precision parts manufacturing takes high precision mechanical parts as processing objects. Based on the systematic and integrated theory and technology, according to the structure and requirements of the workpiece, the organic combination and optimization of feeding, processing, detection and handling are realized, and the production of parts is completed under the precise processing conditions.
Application field of high precision parts and components high precision parts and components are used in all walks of life testing equipment – scientific instruments. In China, they are mainly used in the instrument and instrument industry of scientific instruments.
High precision machining has the advantages of high precision, low energy consumption, flexible production and high efficiency. Reducing the size of the whole manufacturing system and precision parts can not only save energy, but also save manufacturing space and resources, which is in line with the production mode of energy saving and environmental protection. It is one of the development directions of green manufacturing.
Compared with ordinary machinery manufacturing, precision machinery manufacturing has high technology content (design and production), excellent processing equipment, high added value, and small batch sales.
Analysis of foreign development situation high precision machinery manufacturing technology is known as one of the key technologies in the 20th century. It is the key development direction in the 21st century and has been highly valued by all countries in the world. Japan, the European Union, South Korea, the United States and other developed countries have invested a lot of human, material and financial resources to develop their own high-precision mechanical parts research and development and technology.

Requirements of steel processing by computer gong

Smelting quality for high-quality die steel, the processes of out of furnace refining, vacuum treatment, vacuum smelting, powder injection treatment and electroslag remelting are widely used at home and abroad to reduce the contents of harmful elements, oxygen, hydrogen and inclusions in the steel and fine tune the chemical composition and pouring temperature. By ESR, the macrostructure and density of the steel can be effectively improved, and the isotropy of the die steel can be improved. The tests in some domestic factories show that the transverse impact toughness of 4Cr5MoSiV1 steel produced by electric arc furnace is only 31% of the longitudinal impact toughness. After ESR, the transverse impact toughness of 4Cr5MoSiV1 steel is 70% of the longitudinal impact toughness, which is more than doubled. For the die steel with special requirements, the P / m high speed steel and P / m high alloy die steel can better improve the microstructure and properties of the steel.
On the basis of a certain forging ratio, upsetting drawing forging and cross rolling should be adopted as far as possible to improve the isotropy of die material. In order to reduce machining allowance and improve material utilization, precision forging machine, fast forging hydraulic press and high-precision continuous rolling mill are widely used to provide high-precision steel to meet the needs of mold manufacturing.
For heat treatment and finishing of forged and rolled products, controlled atmosphere or vacuum heat treatment should be adopted to avoid oxidation and decarburization. Some plastic die steel and hot work die steel should be pre hardened by Metallurgical Department. For some hot working die materials with high requirements, the Metallurgical Department should refine the structure in advance to eliminate the coarse carbides and chain carbides in the steel, and obtain fine and uniform carbides, so as to further improve the various properties of the steel, especially the isotropy. According to some foreign reports, some hot work die steels are produced with high quality and high directivity by electroslag remelting, multi-directional forging (rolling) and microstructural refinement. The transverse impact toughness can be equal to more than 90% of the longitudinal impact toughness. Many steel plants have named the steel produced by this process, such as isodisc of Bole steel plant in Austria, isotropy of Hitachi metal company in Japan, and microfine of gaozhoubo steel company in Japan. Many metallurgical production departments in China are also committed to this work. In addition, considering the metallurgical quality of various parts of steel, attention should be paid to make the main working face of the mold (such as cavity or edge) close to the surface of steel; because in general, the surface of steel is the clean part of steel, while the center of steel is the area where the macrodefects are concentrated; especially in the large section ledeburite steel, the center part is the center part The inhomogeneity of eutectic carbide in steel is 2-3 grades higher than that on the surface. In addition, the main load bearing direction of the die should be consistent with the deformation direction of the steel, so as to reduce the adverse effect of the anisotropy of the steel on the die.
Thermal conductivity thermal conductivity is also one of the main performance indicators of die steel, especially some hot work die steel and plastic die steel. Mold steel with good thermal conductivity can quickly transfer the heat generated in the processing and the heat from the workpiece, avoid overheating on the working surface of the mold, and improve the working conditions of the mold. For some thermoplastics forming dies and some die-casting dies, in order to speed up the pace of production, it is hoped that the pressed workpieces can be cooled and demoulded quickly to improve productivity. In order to solve this problem, sometimes some die materials with better thermal conductivity than steel are selected, such as high-strength copper alloy, high-strength aluminum alloy, etc.

Basis of high precision CNC machining

CNC machining can change the shape and size of products, which plays a very important role. Many friends don’t know the process benchmark of high speed CNC machining.

The broad meaning of benchmark is “basis”. The datum in mechanical manufacturing refers to the points, lines and surfaces used to determine the geometric relationship between the geometric elements on the production object. According to different functions and applications, datum can be divided into design datum and process datum, and process datum can be divided into process datum, positioning datum, measurement datum and assembly datum.

The technology of high-speed CNC machining is the premise to ensure the production of high-quality parts.

On lathe, the shape and size of the blank can be changed by the rotary motion of the workpiece and the linear or curvilinear motion of the cutter, and it can be processed to meet the requirements of the drawing.

Ordinary machine tools are more and more difficult to meet the needs of processing precision parts. At the same time, due to the improvement of production level, the price of CNC machine tools is falling from time to time. CNC precision parts processing mainly includes ultra precision turning, mirror grinding and grinding.

The primary premise of CNC precision parts processing is the accuracy of process datum. Datum on mechanical drawings are represented by capital letters a, B, C, D, etc. with a specific reference symbol with circle. When the reference symbol is aligned with the surface and its extension line or the dimension limit of the surface, the surface is taken as the datum. When the datum mark is aligned with the dimension line, it means that the solid center line of the dimension is taken as the datum. It is a more general statement that the process is accurate.

Assembly benchmark refers to the precision used to determine the position of parts in components or products during assembly. Measurement datum refers to the specification for the size and position of the machined surface to be measured during the inspection of parts. Positioning datum refers to the datum used for positioning the workpiece in the machine tool or fixture during machining.

Safety precautions – computer gong processing

When processing parts, the protective door must be closed. It is not allowed to stretch the head and hand into the protective door. It is not allowed to open the protective door during processing;
In the process of computer gong processing,

The operator shall not leave the machine tool without permission, and shall keep a high degree of concentration and observe the running state of the machine tool. In case of abnormal phenomenon or accident, the program operation shall be terminated immediately, the power supply shall be cut off and the instructor shall be informed in time, and other operations shall not be carried out;

It is strictly forbidden to tap the control panel and touch screen. It is strictly forbidden to knock the worktable, dividing head, fixture and guide rail;
It is strictly forbidden to open the control cabinet of the numerical control system to watch and touch without permission;
The operator shall not change the internal parameters of the machine tool at will. Interns are not allowed to call or modify other programs that are not compiled by themselves;
On the control microcomputer of machine tool, no other operation is allowed except program operation, transmission and program copy;
CNC milling machine belongs to large precision equipment,

It is strictly forbidden to stack any tools, clamps, cutting edges, measuring tools, workpieces and other sundries on the machine tool except for the tooling and workpieces on the workbench;

It is forbidden to touch the blade tip and scrap iron with hands. Scrap iron must be cleaned with iron hook or brush;
It is forbidden to touch the rotating spindle, workpiece or other moving parts by hand or in any other way;
It is forbidden to measure the workpiece and change the speed manually in the process of processing. It is also forbidden to wipe the workpiece with cotton yarn and clean the machine tool;
Trial operation is forbidden;
When using the hand wheel or fast moving mode to move the position of each axis,

Make sure to see the “and -” signs in X, y and Z directions before moving. When moving, slowly turn the hand wheel to observe the correct direction of the machine before speeding up the movement.

Center positioning datum – computer gong processing

1、 Selection of positioning datum for computer gong machining center

(1) Try to choose the design datum on the part as the positioning datum.

(2) One time clamping can complete the machining of all key precision parts.

(3) When the machining center not only processes the datum but also completes the processing of each station, the selection of its positioning datum needs to consider the completion of as many processing contents as possible.

(4) When the positioning datum and design datum of a part are difficult to coincide, the assembly drawing should be carefully analyzed to determine the design function of the design datum of the part. Through the calculation of the dimension chain, the tolerance range between the positioning datum and design datum should be strictly specified to ensure the machining accuracy.

2、 Selection and use of fixture for CNC machining center

(1) According to the characteristics and processing needs of machining center, the commonly used fixture types include special fixture, modular fixture, adjustable fixture, group fixture and workpiece unified reference positioning clamping system.

(2) The high flexibility of machining center requires that its fixture structure is more compact and simple than ordinary machine tool, clamping action is more rapid and accurate, auxiliary time is reduced as far as possible, operation is more convenient, labor-saving and safe, and enough rigidity and flexibility should be ensured. Therefore, pneumatic and hydraulic clamping devices are often used.

(3) In order to keep all the surfaces to be machined fully exposed, the fixture should be open as far as possible, and the space position of the clamping element should be low as possible, so there must be space for the tool path.

(4) Considering the minimum distance between the machine tool spindle and the worktable and the clamping length of the tool, the installation position of the fixture on the machine tool worktable should ensure that the processing content of the workpiece can be completed within the stroke range of the spindle.

(5) Automatic tool change and worktable exchange can not interfere with the fixture or workpiece.

(6) Sometimes, the positioning block on the fixture is used when installing the workpiece. In the process, in order to meet the processing of the front, back, left and right stations and prevent interference, the workpiece can be removed after clamping. In this regard, we should consider the problem of maintaining the positioning accuracy of the workpiece after removing the positioning element.

(7) Try not to change the clamping point in the middle of machining.

3、 CNC machining to determine the best position of parts on the machine tool table

报错笔记