There are few articles about the use of cutting tools in CNC parts machining field. Today, I will introduce some basic functions that the cutting tools in machining center should have. The material used to make the cutting tool will directly affect the service life, processing efficiency, processing quality and processing cost of the cutting tool, which shows how important it is to select the cutting tool for the machining center. In the process of machining, the tool must receive high pressure, high temperature, conflict, impact and vibration. So the tool used in the machining center must have the following basic functions.
1. Before machining the workpiece in our machining center, we must know the hardness of the workpiece. Generally speaking, the hardness of the tool used must be higher than that of the workpiece processed. Otherwise, it is not the tool that is processing the workpiece, but the workpiece is processing the tool. The hardness of the tool is usually above 60HRC. Originally speaking, the higher the hardness of the tool, the better its wear resistance, the more permanent.
2. The tool used in the strength and toughness machining center must have the strength to receive cutting force, impact force and detonation force, otherwise it will cause tool fracture or collapse, so to meet these requirements, it is necessary to select high light and high toughness raw materials to manufacture the tool.
3. High temperature machining center will produce certain high temperature when processing the workpiece. In order not to affect the machining accuracy, the material with good heat resistance must be selected to make the cutter. The cutter must be able to receive the high temperature produced by the machining center when processing the workpiece, otherwise it will cause high temperature oxidation of the workpiece or cutter, so the cutter must have heat resistance, so that the cutter can have anti-oxidation strength. 4. Process function: the material of cutting tool must have forging function, heat treatment function, welding function and other process functions, so as to facilitate the running in and change of cutting tool.
The basic goal of using the equipment is to increase the production rate of the product parts, achieve better economic benefits, and ensure the safety and stability of the product parts and meet the technical requirements. Therefore, the design of equipment accessories is not only a technical problem, but also an economic problem. In the design of accessories, it is necessary to carry out necessary technical and economic analysis to make the designed accessories obtain better economic benefits.
Know the technical requirements of product parts
After taking over the design mission of the letter of acceptance, necessary raw materials shall be prepared to design the accessories, including the design drawings and drawings of film and technology requirements, process specification, processing equipment associated with the process and other information. After understanding the product parts, dimensional accuracy yamen, mode and other technical requirements, and looking for the key points of the parts and the basic structure of the important dimensions (the size must be guaranteed), the design of the parts is basically confirmed.
Some important parts design plans should be discussed and completely revised before affirmation. At the beginning and the end of this method, it is a better design and processing plan to ensure that the equipment design can meet the requirements of the production plan.
Position reference in positive attachment
With respect to each group of equipment, the size of key parts and important parts must be used as positioning pieces (design positions) in accessories, and the design (precision design) positioning of dreams must be confirmed to confirm the reference key positioning (first reference point). ）And auxiliary positioning reference point (second reference point).
In principle, the first reference point must be the same as the design. If it can not be guaranteed, it is advisable to convert the design basis to process basis through calculation, but the design basis requirements must be guaranteed.
There must be two conditions for selecting a location reference:
The process reference should be selected as the positioning reference to complete the reference matching and reduce the positioning deviation;
Therefore, the average positioning datum should be selected not only to ensure the quality of components and improve the processing efficiency, but also to simplify the structure of accessories (usually using reference holes and positioning shafts).
For example, when designing fixture, the designer must first look at the design of positioning reference drawing from the beginning to the end of positioning reference, and then see that the processing of positioning reference is confirmed (still confirm the process specification). If the positioning reference point is general. If they are not all, the basic design becomes the reference point of the whole calculation process, but the requirements of the design reference point must be guaranteed.
When the designed components are positioned, the basic technical requirements are: good precision, good wear resistance, sufficient strength and rigidity, good processing strength, simple disassembly and other characteristics. For example, the selection of the positioning part of the welding device used for assembling components must be in the positioning mode of the positioning pin according to the requirements; there must be a certain space between the positioning pin and the reference hole of the workpiece, and the size depends on the accuracy of the hole of the workpiece, and it cannot be artificial. The locating pin is fastened by yamen service pin, while the locating pin of 45 × steel and alloy steel Cr12 must have sufficient strength and rigidity through quenching, tempering and heat treatment cooling to improve wear resistance and prolong service life
Structure design of equipment and design of 2-3 parts
Once these parts are placed in the equipment, they are usually fastened so that the parts remain in the process of being processed without being damaged. In the process of machining, workpiece will occur, displacement deformation and vibration, which will affect the machining quality of workpiece.
Therefore, the fastening of parts is also a very important problem to ensure the machining accuracy. In order to achieve good machining efficiency, it is necessary to control the displacement and vibration of parts in machining time within the boundary of machining accuracy. As a result, the handling of the fastening problem of accessories is sometimes more troublesome than the positioning design, and the problem should not be ignored.
Design and affirmation of clamping organization
After the selected connection point is confirmed, the clamping force is designed, the clamping organization is determined and the force exerted by the specific organization is maintained. In general, the clamp system is composed of, power supply and transmission mechanism.
The clamping structure refers to a perfect structure that can implement the clamping of the parts selected at the maintenance point to confirm the performance of the clamping force, and the key point includes that the force applied is a plate, pressure and structure related to the component.
The use mechanism of clamping force can select floating structure and self-locking link,,, with the following four modes:
The fastening structure of bolt and nut: simple structure, simple manufacturing, clamping line width, good self-locking performance, has been used in ordinary;
Application organization of skew force: applicable to large clamping force and small stroke, mainly based on pneumatic and hydraulic power;
Eccentric force application organization: simple structure, fast behavior, but small pressure, mainly used for small parts of accessories;
Push button organization: simple structure, large force ratio, used in pneumatic fixture, reduce the strength of cylinder or air chamber, and get ordinary use.
Careful economy and joint cooperation of parts
The key goal of using accessories is to ensure the quality of works. In detail, when using accessories, ensure the accuracy of dimension (form) and position accuracy of components. Machining deviation of parts completely reflects the deviation of process system, and accessory deviation is the key deviation component of machining deviation. Equipment error is divided into two parts: static error and dynamic error, in which static error represents an important proportion.
Today’s precision parts processing for you to understand the fine mechanical parts free grinding tools finishing technology, together with it.
In the process of precision parts processing, it is necessary to deburr every part. In the process of deburring, file, sandpaper, etc. are used to remove the burr of sophisticated mechanical parts. With the continuous development of modern science and technology, it is still difficult to use human deburring methods to meet the needs of society. Therefore, the new finishing technology is born.
This technology is still used by some large-scale enterprises for surface finishing of carefully machined parts, which is also incorporated into the process by the technical staff, and a standard process is still gradually built. For all kinds of machining techniques, such as turning, milling, forging, stamping, etc., there is no one that will bring certain trace on the surface of carefully machined spare parts, with the emphasis on: rough surface, burr, crack, etc., which will have a positive impact on the normal use of parts, making the quality and quality of parts The index of appearance index is reduced. This processing technique is introduced below.
Free grinding tool finishing technology. With regard to the rolling and polishing process, the processed and meticulous mechanical parts are placed in the roller of the medium, that is, the grinding block and grinding agent are included. Following the complicated relative activities, the free grinding block and grinding agent are gradually colliding, rolling and micro grinding the surface of the parts under the certain pressure, so that the rough surface is continuously refined, so as to enter the detailed mechanical parts After finishing, improve the surface physics and mechanical function, and improve the quality and use function of the machined surface of the meticulous mechanical parts. After selecting a piece of equipment, confirm the abrasives used according to the raw materials and use requirements of the finished parts, as well as the parameters of the appropriate abrasives and grinding blocks, including the variety, loading number and inclusion ratio.
The so-called inclusion ratio refers to the proportion of inclusion grinding block, grinding agent, water and workpiece, processing time, etc. The form, size, size, surface particle size, material ratio, sintering hardness of the grinding block, etc. only in this way can the effect of finishing become more and more dream. In the process of finishing, the off plan is often used. Generally speaking, in the process of finishing, ensure that the grinding block parts, i.e. each polished mechanical parts processing is included nearby, and the raw materials of the polished parts, i.e. steel, copper, aluminum, stainless steel, etc., are classified according to the requirements. The grinding agents of different varieties are required for the different parts raw materials.
It can finish the process actively, and it is flexible actively, and then the power can be 3-7 times higher than the traditional machine tools. Because the computer has the ability to recall and store, it can record and store the input programs, and then actively implement them in the order of program rules, and then complete the product polarization. CNC machine tools only need to change one program to finish the enthusiasm of another workpiece processing, and then to make single piece and small batch production active, so it is called “flexible enthusiasm”
The precision of machining parts is high and the standard distribution is small, which makes the installation simple and no longer requires “repair”. It can complete the concentration of multiple processes and reduce the frequent transfer of cutting parts between machine tools. It has a variety of self-discipline effects, such as active alarm, active monitoring, and active compensation, so it can complete the long-term unattended processing.
Advantages derived from the above. It reduces the work intensity of workers, saves the work force (one person can guard multiple machine tools), reduces the tooling, reduces the trial production cycle and production cycle of new products, and can respond to the market demand quickly. The above advantages and disadvantages are beyond the imagination of predecessors, which is a very important break.
In the rest, CNC machine tools are the basis for the implementation of FMC (flexible manufacturing unit), FMS (flexible manufacturing system) and CIMS (Computer Integrated Manufacturing System) and other enterprise information changes. The numerical control skill still becomes the core skill and the basic skill of the production polarization.
What are the requirements for precision parts? For example, when machining a cylinder, there are strict requirements for the diameter of the cylinder. The positive and negative deviations in the requirements of the articles of association are qualified parts, otherwise they are all parts with different grids; For example, if the diameter of the embedded cylinder is too large to exceed the allowable deviation boundary, the insertion condition will be caused. If the intrinsic diameter is too small to exceed the lower limit of the allowable negative deviation value, it will be caused. The insertion is too loose. There is an unsafe problem.
The length of the cylinder is very long or too short, which exceeds the allowable deviation line. These are all products of different grids. They should be scrapped or processed from scratch, which will definitely result in cost increase.
Secondly, advanced non-standard precision parts processing equipment and testing equipment, advanced processing equipment makes the processing of sophisticated parts simpler, more accurate and more efficient.
CNC machining is now a high-level machining of precision parts. Generally, the parts for this type of machining are used for relatively small purposes. Because the requirements for precision of parts are relatively high and the value is naturally going up, so the boundary line that can be used will be a little smaller. So which precision parts need CNC machining? In the process of making homework, the processing and manufacturing of different workpieces are required, which is largely due to the constant needs of customers. Some parts are used for some precision equipment, such as medical equipment, electronic equipment, etc. the processing complexity of this type of parts will be relatively high, which is also a problem that many manufacturers cannot produce in large quantities.
Generally speaking, the number of parts requiring CNC processing is less, but the processing form is complex. Although parts do not need quite complex tooling, they need a number of different forms, which is also a difficult place for all parts manufacturing. In the process of machining, CNC machining is required because the key needs are compared with the stable quality level and the precision requirements are high. In daily life, it is common to compare the precision shaft with optical fiber tailstock and other parts. Some of these parts need to be processed to a level that cannot be observed by the naked eye, so the processing technology requirements of the operators are relatively high.
Moreover, it is impossible to make a large number of parts. This kind of parts can not be operated in a large amount to ensure the quality is relatively stable, so they can only be made in a small batch. Of course, in the current manufacturing industry, the demand for such parts is also limited, so only some large-scale manufacturers will provide corresponding production services.
Numerical control skill of numerical control lathe, referred to as numerical control, refers to the skill of using the method of digital control to automatically control the completion of a certain course schedule. It usually controls the direction, viewpoint, speed and other mechanical quantities and the switch quantities related to the flow direction of mechanical energy. The origin of CNC lathe is the origin of machine coordinate system. For a specific machine tool, the origin of the machine tool is constant, which is a physical orientation of the machine tool manufacturer on the machine tool.
The key mission of NC lathe process planning is to determine the detailed processing content, cutting amount, process equipment, positioning device method and tool moving track of the process, so as to prepare for the programming.
The setting of the machining path of CNC lathe is a very important link. The machining path is the moving path of the cutter point related to the workpiece in the machining progress. It not only includes the content of the machining process, but also reflects the organization of the machining sequence. Therefore, the machining path is an important evidence for the preparation of the machining program.
The processing route shall ensure the accuracy and appearance roughness of the workpiece to be processed. Planning the processing route should reduce the time of empty travel and improve the processing power. Simplify the numerical calculation and reduce the program section, and reduce the programming workload. According to the form of workpiece, rigidity, machining allowance and rigidity of machine tool system, the number of cycle machining can be determined.
Correct selection of the down milling or reverse milling method in milling. Generally speaking, CNC lathe uses ball screw, so the leisure time is very small, so the advantages of forward milling are more than reverse milling. CNC lathe machining in CNC lathe has not yet reached the conditions of universal application, usually we should put too much allowance on the blank, the unique is that the allowance structure containing forging and casting hard skin layer is processed on the ordinary lathe. If must use numerical control lathe processing, must pay attention to the vivid organization of the program.
The fixture is a process device used to fasten the workpiece quickly and maintain its precise relative position. That is to say, fixture is an indispensable part of machining. With the development of technology to the goal of high speed, high efficiency, thoughtfulness, integration, intelligence and environmental protection, fixture technology is developing towards the goal of high precision, high efficiency, module, combination, generality and economy.
Fixture is also called fixture. In a broad sense, any process in the process, which is used to install workpiece quickly, simply and safely, can be called fixture. For example, welding fixture, inspection fixture, equipped fixture, machine tool fixture, etc. Often referred to as fixture.
When processing the workpiece, in order to make the surface of the workpiece reach the technical requirements such as the size, geometric form and the mutual position accuracy with other surfaces in the drawing regulations, the workpiece must be installed (positioned) and clamped (clamped) before processing.
The use of jigs is conducive to ensuring the processing accuracy, safe and stable production of the workpiece; to increasing the production rate and reducing the cost; to improving the working conditions of the workers and ensuring the safe production; to enlarging the process boundary and completing the “one machine and multi use”.
The fixture is usually composed of positioning elements (to confirm the exact position of workpiece in the fixture), clamping device and indexing device, so that the workpiece can be processed in several positions in one installation, including two types of rotary indexing device and linear moving indexing device, connecting elements and clamp details (fixture base), etc.
In order to improve the production efficiency and product quality, in the middle and back section of the production, the fixture is often used for performance test or auxiliary equipment (can be equipped with constant appearance and height, etc.). The essence is widely used in the manufacturing plant, because the right and wrong mark is customized, so there is only something unexpected but not impossible
The accuracy of hardware parts almost determines the quality of products. The more sophisticated the hardware parts, the higher the accuracy requirements. Why does the processing accuracy of sophisticated hardware parts become worse? Here is the answer for everyone:
The first factor is the poor machining accuracy of the parts themselves. Generally speaking, if the dynamic deviation between the shafts is not adjusted well during the installation, it may also be that the change of the shaft transmission chain due to wear will affect the accuracy of the parts. Generally speaking, the accuracy caused by the deviation of this variety may be adjusted from the beginning. If the deviation is too large or even if there is an alarm, it is necessary to check the servo motor to see if its speed is too high.
The second factor is that the overshoot of the machine tool during operation will also affect the machining accuracy. It may be that the acceleration and deceleration time is too short, and the transformation time is appropriately prolonged. Of course, it may also be that the link between the lead screw and the servo motor is loose.
The third factor is that the roundness of the two shafts is out of tolerance, the axial deformation of the circle is caused by the mechanical failure to be adjusted properly, and the compensation for the clearance of the screw of the shaft is not correct, or the displacement of the shaft positioning may affect the accuracy of the fine parts.
The CNC lathe profession is a basic profession, and the elites in demand are also increasing year by year. With the acceleration of the upgrading pace of the Chinese system homework, the demand for CNC lathe is greatly increased. However, according to statistics, the market is now dominated by imports, and the development of domestic high-end CNC lathe is suffering. In such a case, the success of the CNC lathe industry should have a lot of outstanding lost.
At present, the added value of CNC lathe profession in China is relatively low, and the effect of self-developed high-end CNC lathe is not obvious. This is related to the low position of “made in China” in the world system and the low position of division of labor. Some experts have made an examination and analysis of why the market is dominated by imported CNC lathes, while the domestic CNC lathes are struggling, and obtained the following information: the State encourages the import of advanced skills and equipment, and expands the import of products of advanced CNC lathes
At present, the salary of CNC lathe elites in China is not very popular. For example, the research staff of a CNC lathe factory can get a salary of 3000 yuan in the third or second tier cities. Imagine that such a salary level can be obtained even if it is right or wrong for a high skilled type of work.
So the value of the creation of high skilled workers is more than 3000 yuan. Chinese machine tool enterprises are still unable to meet the urgent dream of engineers. During this period, a very important reason is that the domestic CNC lathe can not sell well. For products of the same model, the value of domestic products is much cheaper than that of overseas enterprises, so that the wife of the enterprise does not look at the product parameters, but only at the value can identify whether they are domestic products or foreign products. On the other hand, the management of Chinese enterprises seems not to be deeply aware of the importance of high-end skilled engineering staff.