Due to the high cost of NC machining, in order to save the cost, a NC machining simulation system is developed. NC machining simulation system can reduce or even completely eliminate the process of trial cutting and manual verification. Before the actual processing of new NC machining program, the programmer can use NC machining simulation system to carry out virtual machining environment and machining process on the computer, and detect the possible problems in the program design.
In the process of NC machining, it is easy to over cut, under cut and other phenomena. At the same time, the damage of the tool, or the processing of waste products, the interference and collision between parts and tools, tools and fixtures, tools and worktable, will cause a certain waste of cost to the production. The NC machining simulation system can simulate the relevant programs well and reduce the loss to the greatest extent.
Before the actual processing, the programmer can confirm whether the finished cutting product is consistent with the original design drawing through the simulation system, and can make better detail analysis.
In the actual processing, five axis NC machining has more advantages than three-axis NC machining, can achieve a wider range, has faster material and efficiency, can reduce processing time and improve surface accuracy. However, because of the high degree of freedom of the two additional rotating shafts, it is easy to collide and damage the machine tool.
Therefore, before the actual processing, we need to use the NC machining simulation system to detect the collision. The main detection algorithms are as follows
The machine tool includes many parts, but the collision detection algorithm between different parts is similar. The simulation system takes the tool, workpiece and fixture as the main research object to detect the possible global collision.
CNC machining center has good processing consistency and economic benefits. Compared with other CNC machine tools, it has the following characteristics
CNC machining mainly refers to the use of digital information recorded on the media to control the machine tool, so that it can automatically perform the specified processing tasks. Numerical control machining can ensure the products to achieve high machining accuracy and stable machining quality; the operation process is easy to achieve automation; high productivity, short production cycle; can reduce a large number of process equipment to meet the needs of rapid product upgrading; it is usually closely linked with CAD to achieve the transformation of design ideas to the final product.
In the whole CNC process, we should focus on the relationship between the processes and the significance of each step. Broadly speaking, the whole process consists of product analysis graphic design process planning path generation path simulation path output processing inspection.
With the rapid development of CNC machining center, the replaceable headstock machining center has appeared. It is equipped with a number of automatically replaceable multi axis headstock with cutting tools, which can process the workpiece at the same time. After decades of development, the current CNC lathe has achieved computer control and has been widely used in industry, especially in the mold manufacturing industry. Horizontal machining center generally has indexing turntable or numerical control turntable, which can process all sides of the workpiece; it can also make joint movement of multiple coordinates to process complex space surface. The vertical machining center generally does not have a turntable, only for the top surface processing. In addition, there are compound machining centers with vertical and horizontal spindles, and vertical and horizontal adjustable machining centers whose spindles can be adjusted into horizontal or vertical shafts. They can process five surfaces of the workpiece.
The automatic tool changing device of CNC machining center of milling machine is composed of tool magazine and tool changing mechanism. There are many kinds of tool magazine, including disc type and chain type. The storage capacity of chain magazine is large.
The tool change mechanism exchanges tools between the machine tool spindle and the tool magazine, commonly known as the manipulator; there are also no manipulator and the spindle directly exchanges tools with the tool magazine, known as the armless tool change device.
High precision and stable quality. It is processed according to the instruction given by the digital pattern. Under normal circumstances, there is no need for manual interference in the labor process, which eliminates the deviation caused by the dominator. When planning to manufacture CNC machine tools, many methods are adopted to make the parts of CNC machine tools reach higher accuracy and stiffness. The movement equivalent of CNC machine tool worktable is widely up to 0.01 ~ 0.0001mm, and the reverse clearance of feed transmission chain and screw pitch deviation can be compensated by CNC device. The high-grade CNC machine tool adopts the closed-loop control of grating ruler for worktable movement. The machining accuracy of CNC machine tool has improved from ± 0.01 mm to ± 0.005 mm or even higher. The positioning accuracy has reached ± 0.002mm to ± 0.005mm in the middle of 1990s. In addition, the transmission system and layout of CNC machine tools have high stiffness and thermal stability. By using the compensation technology, CNC machine tool can get higher machining accuracy than its own. In particular, the progress of a unified batch of parts production uniformity, product qualification rate is high, processing quality is stable. The selection of milling cutter diameter depends on different products and production batches, and the selection of cutter diameter mainly depends on the specifications of the equipment and the processing size of the workpiece.
Plane milling cutter
When selecting the diameter of the plane milling cutter, the power required by the cutter should be within the power range of the machine tool, and the diameter of the machine tool spindle can also be used as the basis for selection. The diameter of plane milling cutter can be selected according to d = 1.5D (D is the diameter of spindle). In batch production, the tool diameter can also be selected according to 1.6 times of the cutting width of the workpiece.
The selection of end mill diameter should mainly consider the requirements of workpiece processing size, and ensure that the power required by the tool is within the rated power range of the machine tool. If it is a small diameter end mill, we should mainly consider whether the maximum revolution of the machine tool can reach the minimum cutting speed of the tool (60m / min).
The diameter and width of the groove milling cutter should be selected according to the size of the workpiece to be machined, and the cutting power should be ensured within the allowable power range of the machine tool. Before using the CNC machine tool, you should read the manual of the machine tool and other relevant information carefully, so as to operate the machine tool correctly, and pay attention to the following points:
(1) The PLC program of the machine tool is designed by the machine tool manufacturer according to the needs of the machine tool, and does not need to be modified. Incorrect modification, operation of the machine tool may cause damage to the machine tool, or even injury to the operator;
(2) It is suggested that the machine can run continuously for up to 24 hours. If the continuous running time is too long, the service life of the electrical system and some mechanical components will be affected, which will affect the accuracy of the machine
(3) The operators and maintainers of machine tools must be professionals who have mastered the corresponding professional knowledge of machine tools or have received technical training, and must operate the machine tools according to the safety operation regulations and safety operation regulations
The continuous fine blanking die for complex parts is the frontier basic technology of fine blanking technology, and it is expected to promote the whole fine blanking technology in China. Taking the synchronizer gear ring, clutch plate, longitudinal compound continuous fine blanking process and continuous fine blanking die for complex parts as the breakthrough point, the key technology of fine blanking die design and manufacturing is studied, so as to realize the rapid improvement of fine blanking die technology in China and shorten the gap with advanced countries as soon as possible.
Die life is a comprehensive reflection of die material, small craft and supporting product level,
It can not only solve the problem that the life of fine blanking die is too low, but also promote the technical development of die materials, fine blanking process, supporting tooling and other auxiliary products.
Precision blanking and precision forging are two advanced manufacturing technologies developed in parallel. If the precision blanking parts are too thick and need precision forging, the precision forging must be too thin. They are closely related. The basic idea of developing precision forging and fine blanking compound process is to find the combination point of the two processes (such as gear parts with wheel hub and cam parts with short shaft). The precision forging in China has a long history and has a high level, so it is a good way to improve the overall level of precision blanking technology in China.
NC machine tool programming technology is not a very short period of time to learn, need to learn step by step, and slowly accumulate experience. Mastering this technology is not only the theoretical level of engineers, but also the practical experience and practical ability of senior technicians.
3, skilled CNC machine tools. It takes 2-3 years to study. In this process, we need to learn how to operate the system, fixture installation, part benchmark alignment, tool presetting, set zero offset, set tool length compensation, radius compensation, tool and handling handle, cutting tool grinding, part measurement (skilled use of vernier caliper, micrometer card, micrometer, micrometer, diameter bar meter), etc.
4, must have good fixture foundation and measurement technology.
A set of products usually have several or more than ten parts. The main matching dimensions of these parts are guaranteed by computer gong processing. It is very important to choose a reasonable tolerance, especially some product design drawings do not consider the matching problem. Bottom, surface, shell fit, shape is no doubt 0 to 0 fit, positioning is guaranteed by the mouth, concave mouth and convex mouth tolerance is generally 0.1 mm, unilateral. The fit on the big body is like a transparent mirror. The shape of the general accessories is 0.1 ~ 0.2 smaller than the size on the big body. The shape of the movable accessories on the big body, such as buttons, is 0.1 ~ 0.5 smaller than the shape on the big body. The surface shape of the accessories on the big body is generally consistent with the surface shape on the big body, which can be removed from the big body.
1、 Exit angle (draft angle)
All plastic molds should have a mold angle, otherwise they will be scratched. If it is not indicated in the drawing, you can discuss with the mold maker. The mold angle is generally 0.5 ~ 3 degrees. If the mold is etched, the mold angle should be larger, 2 ~ 5 degrees, depending on the thickness of the etched pattern.
2、 Cutting problem
Most of the time, when the cutter is just milled, the amount of cutting is relatively large, which is easy to cause the cutter to break and bounce. At this time, you can first roughen the lower cutter position, or lift the cutter away, or lower the cutter outside the material in the daytime. In a word, this problem should be fully considered. Grab the knife, spring the knife, drop the knife, when the processing capacity is relatively large, the knife clip is too long, the knife is too small, this often happens. When the processing capacity is relatively large, especially when the concentration feed is large, it is easy to occur. For example, when the depth of the smooth side is 50 mm and the diameter is 3 / 4, we can process it in 25 mm twice, so it is not easy to occur. Tool clamping is too long, the length of the tool is very important for processing, should try to clamp short, beginners are easy to ignore this problem, the program paper must indicate the length of the tool clamping. It’s easy to grab the knife when turning the corner. The solution is to use a smaller knife to clear the corner layer by layer, and then change the larger knife to smooth the side.
3、 Sharpen a knife
The shapes of computer gongs are different, so we often need to grind all kinds of knives. When all kinds of molding knives are worn out, we also need to grind them. Only when we reach the following points can we grind a usable knife.
4、 Milling direction
The reason is that the rigidity of the computer gong is relatively good, it is not easy to let the cutter, the back clearance is small, and the milling shape or inner groove is left compensation. When machining left and right symmetrical shapes, the profile tool path cannot be mirrored, otherwise the processing effect of the mirrored side is not good. In order to communicate with the operator of the machine tool, the program paper should include:
High speed CNC machining can change the shape and size of products, which plays a very important role.
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.
The lubrication function of metal cutting fluid in the cutting process can reduce the friction between the rake face and the chip, and between the flank and the machined surface, forming a part of lubricating film, thus reducing the cutting force, friction and power consumption, reducing the surface temperature and tool wear of the friction part between the tool and the workpiece blank, and improving the cutting performance of deep hole machining workpiece materials . In the grinding process, after adding grinding fluid, the grinding fluid seeps into the grinding wheel grain workpiece and grain debris to form a lubricating film, which reduces the friction between the interfaces, prevents the abrasive cutting edge from wearing and adhering to the chips, thus reducing the grinding force and friction heat, and improving the durability of the grinding wheel and the surface quality of the workpiece.
The cooling effect of cutting fluid is to take the cutting heat away from the cutting tool and workpiece through the convection and vaporization between the cutting fluid and the heated cutting tool (or grinding wheel), chip and workpiece, so as to effectively reduce the cutting temperature, reduce the thermal deformation of the workpiece and cutter, maintain the hardness of the cutter, and improve the machining accuracy and the durability of the cutter. The cooling performance of cutting fluid is related to its thermal conductivity, specific heat, heat of vaporization and viscosity (or fluidity). The thermal conductivity and specific heat of water are higher than that of oil, so the cooling performance of water is better than that of oil.
Deep hole machining in the process of metal cutting, cutting fluid is required to have a good cleaning effect. Remove the generated chips, grinding chips, iron powder, oil and sand particles, prevent the contamination of machine tool, workpiece and cutter, keep the cutting edge of cutter or grinding wheel sharp, and do not affect the cutting effect. For oil-based cutting oil, the lower the viscosity, the stronger the cleaning ability. Especially for cutting oil containing kerosene, diesel and other light components, the better the permeability and cleaning performance. The water-based cutting fluid containing surfactant has better cleaning effect, because it can form an adsorption film on the surface, prevent particles and oil sludge from adhering to the workpiece, cutter and grinding wheel. At the same time, it can penetrate into the interface where particles and oil sludge adhere, separate it from the interface, take it away with the cutting fluid, and keep the cutting fluid clean.
In the process of metal cutting, the workpiece will be corroded by contacting with corrosive media such as environment media and oil sludge produced by decomposition or oxidation of cutting fluid components, and the surface of machine tool parts in contact with cutting fluid will also be corroded. In addition, when the workpiece is temporarily stored after processing or in the process of circulation between processes, the cutting fluid is also required to have a certain anti rust ability, so as to prevent corrosive substances such as environmental media and oil sludge in the residual cutting fluid from eroding the metal.
CNC machining skills: CNC machine tool installation and debugging of the work first depends on the new CNC machine tool is a small machine tool or a large machine tool. Generally, the installation of small CNC machine tools is relatively simple, while the transportation and packaging of large CNC machine tools must be considered. Therefore, the whole machine tool has to be divided into several parts. After arriving at the work site, it must be reassembled and carefully adjusted. The workload is large and complex. Comparatively speaking, small CNC machine tools can avoid the workload of reorganization after decomposition. However, the open box acceptance and start-up debugging of small CNC machine tools must also be treated seriously and carefully to avoid mistakes and losses. Usually, the debugging of CNC machine tools must go through the following steps.
(1) At the beginning, we did it on the spot. Before the arrival of the machine tool, the installation foundation of the machine tool shall be laid according to the foundation drawing provided by the machine tool factory, and the preset holes of the anchor bolts shall be reserved; the spare parts, accessories, data and accessories shall be counted according to the packing list; the attached documents shall be kept by a special person (especially the detailed list of the parameter setting of the numerical control machine tool, etc.); According to the instructions, all parts of the machine tool must be in place on the site, and all fasteners must be in place according to the number.
(2) Connection of machine tool. Before the assembly of all parts of the machine tool, remove the antirust coating on the installation connection surface, the guide rail and the surface of all moving parts, and do a good job in cleaning the appearance of all parts. Then assemble all parts of the machine into a whole machine, such as installing the column, numerical control cabinet and electrical cabinet on the bed, installing the manipulator of the tool magazine on the column, and installing the extension body on the bed. The original positioning pin, positioning block and positioning element should be used during assembly to restore the installation position to the state before disassembly of the machine tool, so as to facilitate the next step of precision debugging. After the components are assembled, the cables, oil pipes and gas pipes are connected. There are electrical wiring diagram and pneumatic and hydraulic pipeline diagram in the manual of the machine tool, so the relevant cables and pipelines should be connected one by one according to the marks. When connecting, pay special attention to cleaning, reliable contact and sealing, and check for looseness and damage. After the cable is inserted, the screw must be tightened to ensure reliable contact. In the connection of oil pipe and gas pipe, it is necessary to prevent foreign matters from entering the pipe from the interface, so as to avoid the failure of the whole hydraulic system. When connecting pipelines, each joint should be tightened. Otherwise, during the test run, especially on some large oil separators, if one pipe leaks oil, it is often necessary to remove a batch of pipes, resulting in heavy repair work. After the cable and oil pipe are connected, the pipelines shall be fixed in place, the protective cover shall be installed, and the neat appearance shall be ensured.
(3) The connection and adjustment of CNC system includes open box inspection, external cable connection, power connection, confirmation of setting, confirmation of input current, voltage, frequency and phase sequence, confirmation of machine parameters, etc.
(4) Power on test run.
(5) Machine tool precision and function debugging.
(7) Organize machine tool acceptance