Author Archive chengcg


CNC ultra precision processing technology

In the field of machining, the machining of parts with high precision is called ultra precision machining. Ultra precision parts processing mainly includes ultra precision turning, mirror grinding and grinding equipment. In ultra precision lathe, micro turning is carried out with single crystal diamond turning tool after fine grinding. The cutting thickness is only about 1 micron. It is often used to process high precision and smooth surface parts of non-ferrous metal materials, such as spherical, aspheric and flat mirrors. For example, the aspheric mirror with a diameter of 800mm is processed for medical equipment accessories, with the highest accuracy of 0.1 μ m and surface roughness of rz0.05 μ M.

In the process of machining ultra precision parts, when the machining precision is usually nanometer or even atomic unit (atomic lattice distance is 0.1-0.2 nanometer), the machining method of ultra precision parts can not adapt to it. It is necessary to use the machining method of special precision parts, that is, chemical energy, electrochemical energy, thermal energy or electric energy, to make these energies exceed the binding energy between atoms, So as to remove the attachment, bonding or lattice deformation of some atoms on the surface of the workpiece, so as to achieve the purpose of ultra precision machining. This kind of processing includes mechanical chemical polishing, ion sputtering and ion implantation, electron beam exposure, laser beam processing, metal evaporation and molecular beam epitaxy.

The main feature of ultra precision parts machining is that the amount of material removed or added to the surface layer can be controlled very finely. However, to obtain the machining accuracy of ultra precision parts, it still depends on precision machining equipment and precise control system, and uses ultra precision mask as intermediary. For example, the plate making of integrated circuits in the electronic industry is to use the electron beam to expose the photoresist (see lithography) on the mask to make the atoms of the photoresist polymerize (or decompose) directly under the electron impact, and then use the developer to dissolve the polymerized or unpolymerized part to make the mask. Electron beam exposure plate making requires the positioning accuracy of worktable up to 100% ± 0.01 micron ultra precision machining equipment.

The so-called high quality comes from exquisite technology. High quality is inseparable from high quality technology, precision processing equipment and reasonable processing technology.



The requirements of high speed CNC for tool

In the field of machining industry, CNC machining center belongs to precision machining equipment, mainly because of the high precision of the machine tool itself, computer programming command CNC operation. CNC machining center machine tool spindle high precision, look at the requirements of high-speed machining tool understanding

In the process of machining mechanical parts, high-speed CNC machining is very important for the selection of cutting tools. The selection of cutting tools is mainly considered from two aspects,

The first is: the dynamic balance state of the cutting tool under the high-speed rotation state;

The second is: how to ensure the life of the tool. In order to ensure the tool can rotate stably around the axis at high speed;

At present, there are two approaches:

One is: the tool with dynamic balance device is used, which is equipped with mechanical slider or fluid dynamic balance design in the tool sleeve;

Second, the integral tool is adopted, and the tool sleeve and the tool body are integrated to ensure the minimum clearance between the tool body and the tool sleeve in the installation process. From the overall performance point of view, the overall tool in this aspect is the most ideal. However, as the tool sleeve and the tool body are integrated, once the tool body is scrapped, the tool sleeve will be scrapped together, so the cost is higher. In the process of parts processing, different materials have different requirements for tool selection. For example: aluminum processing is the first aluminum knife, there is a hardness of steel need to choose different hardness alloy coating knife. Under the operation of high-speed CNC machining, the overall requirements of CNC tools are balance, advanced materials, high manufacturing accuracy, safety, easy chip removal and multi-purpose.

The above is the understanding of the requirements of high-speed CNC machining tools,



How to improve the production efficiency of CNC

In the field of machining industry, production efficiency is directly related to the order cycle and processing profit, which can not be easily ignored. So how to improve the efficiency of machining production? Let’s take a look at the following

  1. Select reasonable processing technology, optimize processing route, improve processing efficiency and ensure quality.
  2. CNC machine tool processing operation, must ensure that the table can bear the most weight, ensure the smooth progress of machining process. Nowadays, the purpose of CNC machine tools is to improve the production efficiency. If the machine table can not meet the requirements of use, it will be affected in production.
  3. In the process of machining, because of the increasing speed of high-speed cutting of CNC machine tools, in order to adapt to the processing method, the radius of the tool should be reduced to improve the moving speed of the main bearing of the machine tool. Meet the use requirements in the process of processing, improve the processing quality.
  4. For some precision mechanical parts processing, CNC machine tools need to achieve high precision, high stability and high speed processing requirements. Only in this way can we improve the machining ability and achieve reasonable production efficiency in the cutting process!



Influence of surface roughness on quality of CNC parts

In the machining industry, the surface roughness of mechanical parts is also a part of the quality. How to control the surface roughness in machining, what effect does the surface roughness have on the quality of parts, let’s take a look at it next

In the mechanical parts processing drawings, will indicate the surface roughness processing requirements. If the machining process fails to meet the requirements, the surface roughness of parts has a great impact on the mechanical assembly performance and service life

  1. If the surface roughness of the parts can not meet the requirements, the contact area will be reduced, the pressure per unit area will be increased, the contact deformation will be increased, the friction resistance will be increased, and the wear of the parts will be accelerated;
  2. The surface roughness affects the fit properties. For clearance fit, the surface roughness is easy to wear, resulting in the rapid increase of clearance. For interference fit, during assembly, it can flatten the small convex peaks, reduce the effective interference, and reduce the strength of fit parts;
  3. The surface of the parts is rough and low, and corrosive substances are easy to accumulate at the bottom of the surface, which is difficult to remove, causing surface corrosion;
  4. When the part bears the load, the stress concentration is easy to occur at the concave bottom, resulting in cracks and fracture of the part.

In the machining process of mechanical parts, the machining allowance should be reserved for the parts with high surface roughness.



Advantages and disadvantages of CNC process

In the field of mechanical processing industry, with the continuous development of science and technology, ordinary processing equipment has been unable to meet the market demand. Most mechanical processing manufacturers have added or replaced precision CNC processing equipment (CNC machine tools). Precision CNC processing has replaced ordinary machine tools, which improves the production and processing efficiency and stabilizes the production and processing quality. This is the main advantage of CNC precision machining equipment, but there are also disadvantages, let’s see

Advantages: high precision CNC machining, high efficiency; Pearl River Delta region, Dongguan processing industry, precision CNC processing also known as computer gong processing, also belongs to CNC machine tool processing equipment. In the process of processing, the automatic operation is completely controlled by the code command, which reduces the labor operation. Because it belongs to numerical control processing equipment, the production efficiency is many times that of ordinary machine tools, and the processing quality is relatively stable. When multiple or batch parts are processed, the production efficiency is more obvious.

Disadvantages: CNC processing failure, maintenance costs are high; In case of failure in precision CNC processing, after-sales service can replace the parts, or the parts have passed the shelf life, the cost of maintenance is quite expensive, because in CNC processing precision, sometimes there may be small problems, and the equipment can not operate normally, so it needs professional technicians to maintain. But the general professional technician salary is high, causes the maintenance cost to increase.



Establishment of CNC processing route

In the field of mechanical processing industry, the reasonable processing technology should be selected for the machining process of mechanical parts in order to produce and process more efficiently and accurately. Before the machining of mechanical parts, how to better reflect the efficient and accurate machining quality? Let’s take a look at the formulation of the machining process route of mechanical parts

Now we have a simple understanding of the formulation of the processing route of mechanical parts, which is mainly divided into three steps:

  1. Draw up the processing route: analyze and study the contents and technical requirements of parts production drawings, draw up the processing method, processing scheme and process route of parts processing.
  2. Arrange the processing procedure

(1) Select blank( 2) Arrange machining procedure 1, select machining scheme 2 and determine datum plane reasonably( 3) Arrange the heat treatment process 1. The heat treatment process to improve the cutting performance of metal materials, such as annealing and normalizing, is generally arranged before rough machining. 2. The heat treatment process to eliminate internal stress, such as intermediate annealing, tempering and aging, is generally arranged before rough machining and rough machining. 3. The heat treatment process to improve the performance of mechanical parts, such as quenching, tempering and aging Quenching and tempering, carburizing and other surface treatment are generally arranged before the final processing. All the heat treatment processes are carried out before the final processing of the parts, because the parts must change after the heat treatment process, and the errors caused by deformation can be corrected during the final processing( 4) Arrange the inspection process well. During the production and processing of small batch parts, self inspection, mutual inspection and special inspection shall be carried out. The products can only be delivered after passing the inspection.

  1. Draw up the processing technology process: the purpose of making the processing technology route is to ensure the product quality and improve the economic benefits. At the same time, it is to determine the number of production personnel and select the processing equipment. The principle of processing sequence arrangement: base surface first, rough and fine separation, rough and fine first, surface first and hole second.

Mechanical parts processing technology requirements are different, according to the requirements to choose a reasonable processing route. For precision parts with special requirements, select the precise processing route.



Analysis of CNC machining dimensional error

In the field of machining, dimensional error has a direct impact on the working performance and service life of products, and the error is closely related to the processing quality of parts and the assembly accuracy of products. Precision machinery parts, automation equipment and other industries spare parts processing technology is generally finished by finishing and rough processing, the selection of processing technology is unreasonable or processing technology problems, will cause dimensional error of parts.

Dimensional error refers to the requirement that the actual geometric parameters (drawing process size, geometric shape and mutual position) of parts after processing are consistent with the geometric parameters of processing technology. The deviation between them is machining error, and the size of machining error reflects the machining precision. The accuracy of parts processing is expressed by the size of processing error, that is, by the relevant national tolerance standards. The actual parameters obtained by any processing method will not be absolutely accurate. In machining practice, under the premise of ensuring the working performance of the machine tool, the machining error does not exceed the deviation required by the customer’s drawing process is qualified.

In order to ensure and improve the machining accuracy of mechanical parts, it is the main responsibility to master the basic law of the change of machining dimension error. As the saying goes, to produce good equipment, we must first ensure the processing quality of mechanical parts.



Influence of blackening treatment of 45 ° steel on accuracy

Contact machining for many years, equipment accessories 45 # steel surface treatment, whether there is an impact on the dimensional accuracy of parts? 45 ᦇ blackening of steel has no effect on the dimensional accuracy, because blackening is a common means of chemical surface treatment. The principle is to produce an oxide film on the metal surface to isolate the air and achieve the purpose of rust prevention. In the surface treatment, the dimension will not deform, so it will not affect the accuracy of parts.

In the process of machining, the parts with low appearance requirements need surface treatment, which can be blackened. In the machining industry, the surface blackening treatment of 45 ° steel parts is also called bluing. If the machining dimension of precision mechanical parts has accuracy requirements, different surface treatment processes can be selected according to the purpose of parts design. In the surface treatment process, 45 ° steel has blackening, chromium plating, nickel plating, zinc plating and other treatment. If the processing accuracy requirements on the production drawings are different, the reasonable surface treatment process should be selected.



CNC processing method of aluminum alloy

In the field of machining industry, we often contact with the processing of aluminum alloy parts. Here is a brief introduction of the difficulties in processing aluminum alloy parts

In the process of machining, due to the influence of machining deformation on the dimension, form and position tolerance of parts, the machining method of high speed, low feed and low cutting depth is used to complete the machining of all associated dimensions of parts through one clamping, so as to reduce the deformation caused by excessive cutting force in the machining process and avoid the error caused by the non coincidence of machining datum and design datum, Improve the dimensional accuracy and shape and position accuracy of parts.

Problem: parts in the machining process, often due to internal stress and deformation, especially non-ferrous light metals such as aluminum, magnesium alloy processing. The frequent occurrence of warping, side bending and distortion caused by internal stress will seriously affect the processing quality and efficiency of parts, especially for thin-walled and thin-walled parts. How to minimize or eliminate the deformation of parts, ensure product quality and production efficiency, has been our processing technology topic!

Cause analysis: in the process of production and processing, in order to improve the processing and use performance of aluminum alloy, it is necessary to improve the strength through heat treatment (quenching treatment + aging treatment) before processing. The internal stress of the material produced in the quenching process is very large, and the aging process can not completely release the internal stress produced in the quenching process. In the subsequent machining process, new cutting stress is generated. With the continuous removal of materials, the balance state of internal stress is broken, and the internal stress is redistributed until the new balance process is reached, resulting in deformation, which makes the parts lose their due machining accuracy. Moreover, when the stress on the surface of the part exceeds the strength limit of the material, cracks will occur.

Solution: in view of the above reasons, the “nesting” method is used for processing thin-walled and thin-walled aluminum alloy parts“ The “nesting” method is a processing method that the parts are taken out from the blank after all dimensions are processed in one clamping. The process of raw materials includes milling upper surface, rough milling inner cavity, rough milling shape, finish milling shape, finish milling inner cavity, finish milling bottom surface, point (drill) hole, cutting and so on. Because the whole process is completed in one clamping, before cutting off, because the part is connected with the bottom of the blank material, the internal stress will not cause large deformation of the part, and the size of the part is stable in the whole process. When cutting, it is necessary to make the blank material and the part material have 0.1 mm adhesion on the bottom surface, so as to ensure that the part has enough strength to resist the cutting stress generated in the whole “nesting” process.

After the mechanical parts are cut from the blank, although the parts are deformed due to the stress release, the relative dimensions of the parts will not change. It only needs to increase the correction process to level the bottom surface, and all the dimensions and shapes can be restored to be correct.

The above is the knowledge of aluminum alloy processing technology. In the future processing, it can not only improve the processing efficiency and product quality, but also avoid the error caused by the non coincidence of design benchmark and process benchmark, avoid the compression of tolerance due to the conversion of dimension chain, and simplify the process of making process specification and parts processing.



Characteristics of CNC machining center

In the domestic machining industry, CNC machining center is called CNC milling machine processing and computer gong processing. The main features of CNC machining are high precision, high efficiency and stable quality. CNC machining is very suitable for small batch and multi variety products. CNC machining in the production of different parts, only need to change the program, the use is very flexible. In addition to the above features, CNC processing also has the following main features

(1) High rigidity, in order to match the high precision of CNC system, CNC milling machine has high rigidity, CNC machining center can adapt to the high precision machining requirements.

(2) Light drag, turret (table) movement using ball screw pair, small friction, easy to move. The pressure angle of the special bearing for supporting both ends of the precision CNC machining lead screw is larger than that of the ordinary bearing, so it can be selected and matched before leaving the factory; The lubrication part of CNC milling machine adopts oil mist automatic lubrication, which makes CNC milling machine easy to move.

(3) General precision CNC milling machine processing three-axis linkage, according to different machine configuration, there are also four axis, five axis high precision CNC machining center. The main reason is high precision, small batch processing parts can multiple improve production efficiency. These are the main features of precision CNC machining.