CNC lathe programming processing
1. Determine the processing location and specific content of the workpiece Determine the content of the process to be completed on the machine and the connection with the front and the back. (1) The situation before the workpiece is processed in this process. For example, castings, forgings or bars, shapes, dimensions, machining allowances, etc. (2) The shape and size of the processed part in the previous process, or the reference surface and the reference hole which are processed in the previous process. (3) The part and specific content to be processed in this process. (4) In order to facilitate the preparation of the process and procedures, the rough drawing before the processing and the processing drawing of this process should be drawn. 2. Determine the clamping method and design fixture of the workpiece Select or design the fixture based on the determined workpiece machining location, positioning reference, and clamping requirements. CNC lathes use three-jaw self-centering chucks to hold the workpiece; shaft-type workpieces can also support the workpiece with the tailstock tip. Due to the extremely high speed of the CNC lathe spindle, hydraulic high-speed power chucks are often used to facilitate the clamping of the workpiece, because it has passed strict balance in the production plant, with high speed (limit speed up to 4000~6000r/min), high Clamping force (maximum push-pull force is 2000~8000N), high precision, convenient gripping, through hole and long service life. The soft gripper can also be used to hold the workpiece, and the soft jaw camber is randomly prepared by the operator to achieve the desired grip accuracy. By adjusting the cylinder pressure, the chuck clamping force can be changed to meet the special needs of clamping various thin-walled and easily deformable workpieces. In order to reduce the deformation of the slender shaft during machining, improve the machining accuracy, and when machining the inner hole of the hole-type workpiece, the hydraulic self-centering center frame can be used, and the centering accuracy can reach 0.03mm. 3. Determine the processing plan (1) Principles for determining the processing plan The processing plan is also called the process plan. The machining plan of the CNC machine tool includes the formulation of the process, the work step and the route of the cutter. In the machining process of CNC machine tools, due to the complex and diverse processing objects, especially the shape and position of the contour curve, and the influence of various factors such as different materials and batches, specific analysis should be carried out when formulating the processing plan for specific parts. And treat differently and handle it flexibly. Only in this way can the processing plan formulated be reasonable, so as to achieve the objectives of superior quality, high efficiency and low cost. The general principles for formulating a processing plan are: first coarse and then fine, first and then far, first inside and outside, the least program, the shortest route and special treatment. (1) first coarse and fine In order to improve the production efficiency and ensure the finishing quality of the parts, the roughing process should be arranged first during the cutting process. In a short time, a large amount of machining allowance before finishing (as shown in the dotted line in Figure 3-4) The part shown) is removed, while trying to meet the margin uniformity requirements of finishing. When the roughing process is completed, the semi-finishing and finishing after the tool change should be arranged. Among them, the purpose of arranging the semi-finishing is to arrange the semi-finishing as a transitional process when the uniformity of the remaining amount after the rough machining can not meet the finishing requirements, so that the finishing allowance is small and uniform. When arranging a finishing process that can be performed with one or more knives, the final contour of the part should be continuously machined from the last knive. At this time, the position of the advance and retraction of the machining tool should be considered properly. Try not to arrange the cutting and cutting or changing and stopping in the continuous contour to avoid the elastic deformation caused by the sudden change of the cutting force, resulting in the surface of the smooth connecting contour. Sickness, sudden shape change, or stagnant knife marks. (2) First and then far The far and near here is based on the distance of the processing part relative to the tool point. Under normal circumstances, especially in roughing, it is usually arranged to process the part close to the tool point and to process it away from the tool point to shorten the tool moving distance and reduce the idle travel time. For turning machining, it is advantageous to maintain the rigidity of the blank or semi-finished parts and improve the cutting conditions. (3) First inside and outside For parts that need to be machined inside (internal, cavity) and outer surface, when formulating the machining plan, it is usually necessary to arrange the inner and inner cavities and the outer surface. This is because it is difficult to control the size and shape of the inner surface, the rigidity of the tool is correspondingly poor, the durability of the cutting edge (blade) is easily reduced by the heat of cutting, and it is difficult to remove the chips during processing. (4) The shortest route The work focus of the pass route is determined, which is mainly used to determine the roughing and idle travel path, because the cutting path of the finishing cutting process is basically carried out along the order of its parts. The path of the tool generally refers to the path that the tool starts from the point of the tool point (or the fixed point of the machine tool) until it returns to the point and ends the machining process, including the path of the cutting process and the non-cutting idle path such as tool introduction and cutting. Under the premise of ensuring the processing quality, the machining program has the shortest path, which not only saves the execution time of the whole machining process, but also reduces unnecessary tool consumption and wear of the sliding parts of the machine feed mechanism. In addition to relying on a large amount of practical experience, the optimized process plan should be good at analysis and can be supplemented with some simple calculations if necessary. The above principles are not static, and for some special cases, flexible and flexible solutions are needed. If any workpiece is finished, it must be roughed and finished to ensure its processing accuracy and quality. These depend on the continuous accumulation and learning of the actual processing experience of the programmer. (2) Relationship between processing route and machining allowance Under the condition that the numerical control lathe has not yet reached universal use, it is generally necessary to arrange excessive margin on the blank, especially the margin containing the forged and cast hard skin layer on the ordinary lathe. If you must use CNC lathes, you should pay attention to the flexible arrangement of the program. Arrange some subroutines to perform certain cutting operations on the parts with excessive margin. (1) Processing route for step cutting of large margin blank (2) End position of the tool during layer cutting When machining a thread on a CNC lathe, due to the change of its transmission chain, in principle, as long as the rotation speed of the spindle can be ensured, the tool can be displaced by one pitch along the main feed axis (mostly the Z-axis), and should not be restricted. However, when machining a thread on a CNC lathe, it will be affected by the following aspects: (1) The pitch (lead) value of the command in the thread machining block is equivalent to the feedrate F expressed by the feed amount (mm/r). If the spindle speed of the machine tool is selected too high, the converted The speed (mm/min) must be significantly higher than the normal value; (2) The tool will be constrained by the servo drive system up/down frequency and the numerical control device interpolation operation speed at the beginning/end of its displacement. Since the rising/lowering frequency characteristics cannot meet the processing requirements, etc., it may be due to the main progress. The "advance" and "lag" generated by the movement cause the pitch of some of the screws to meet the requirements; (3) The turning thread must be realized by the synchronous running function of the spindle, that is, the turning thread requires a spindle pulse generator (encoder). When the spindle speed is selected too high, the positioning pulse sent by the encoder (ie a reference pulse signal sent every revolution of the spindle) may be due to "overshoot" (especially when the quality of the encoder is unstable). This causes the workpiece threads to be smashed. Therefore, when the thread is threaded, the spindle speed should be determined according to the following principles: (1) In the case of ensuring production efficiency and normal cutting, it is advisable to select a lower spindle speed; (2) When the lead-in length δ1 and the cut-out length δ2 (as shown in the figure) in the threading program block are considered to be sufficient, that is, if the thread feed distance exceeds the length of the specified thread on the pattern, the height may be selected to be higher. Spindle speed (3) When the allowable working speed specified by the encoder exceeds the maximum speed of the spindle specified by the machine tool, the spindle speed can be selected as high as possible; (4) Under normal circumstances, the spindle speed (n screw) at the time of threading should be determined according to the calculation formula specified in the machine tool or numerical control system manual. The calculation formula is: n screw ≤ n allow / L (r / min) where n allows - the maximum operating speed (r / min) allowed by the encoder; L—pitch (or lead, mm) of the workpiece thread. 4. Determine the amount of cutting and feed When programming, the programmer must determine the amount of cutting for each process. When selecting the cutting amount, we must fully consider the various factors affecting the cutting, correctly select the cutting conditions, and reasonably determine the cutting amount, which can effectively improve the machining quality and output. The factors affecting the cutting conditions are: rigidity of machine tools, tools, tools and workpieces; cutting speed, depth of cut, cutting feed rate; workpiece accuracy and surface roughness; tool life expectancy and maximum productivity; type of cutting fluid, cooling method; The hardness and heat treatment of the workpiece material; the number of workpieces; the life of the machine tool. Among the above factors, the cutting speed, the cutting depth, and the cutting feed rate are the main factors. The cutting speed directly affects the cutting efficiency. If the cutting speed is too small, the cutting time will be lengthened, and the tool will not be able to perform its function. If the cutting speed is too fast, the cutting time can be shortened, but the tool is prone to high heat and affects the life of the tool. There are many factors that determine the cutting speed, which are summarized as follows: (1) Tool material. The maximum cutting speed allowed is different for different tool materials. The high-speed steel cutting tool has a high-temperature cutting speed of less than 50m/min, the high-temperature cutting speed of the carbide tool can reach more than 100m/min, and the high-temperature cutting speed of the ceramic tool can be as high as 1000m/min. (2) Workpiece materials. The hardness of the workpiece material will affect the cutting speed of the tool. When the same tool is used to process hard materials, the cutting speed should be reduced. When the soft material is processed, the cutting speed can be improved. (3) Tool life. If the tool life (life) is long, a lower cutting speed should be used. Conversely, a higher cutting speed can be used. (4) Cutting depth and feed amount. The cutting depth and the amount of cutting are large, the cutting resistance is also large, and the cutting heat is increased, so the cutting speed should be reduced. (5) The shape of the tool. The shape of the tool, the size of the angle, and the sharpness of the cutting edge all affect the selection of the cutting speed. (6) Coolant use. The machine tool has good rigidity and high precision to increase the cutting speed; otherwise, it needs to reduce the cutting speed. Among the above factors affecting the cutting speed, the influence of the tool material is the most important. The depth of cut is mainly limited by the rigidity of the machine tool. The cutting depth should be as large as possible if the machine tool stiffness is allowed. If the machining accuracy is not limited, the cutting depth can be equal to the machining allowance of the part. This will reduce the number of passes. The spindle speed is determined by the cutting speed allowed by the machine and the tool. It can be selected by calculation or table lookup. The feed rate f (mm/r) or the feed rate F (mm/min) is selected according to the machining accuracy of the part, the surface roughness, the tool and the workpiece material. The maximum feed rate is limited by the machine stiffness and feed drive and CNC system. When selecting the cutting amount, the programmer must select the cutting amount that suits the machine's characteristics and the optimum durability of the tool according to the requirements of the machine manual and the tool durability. Of course, it is also possible to use an analogy method to determine the amount of cutting by experience. Regardless of the method used to select the amount of cutting, the durability of the tool must be ensured to complete the machining of a part, or to ensure that the tool durability is not less than one work shift, and the minimum can not be less than half a shift. The in vitro culture of cells and tissues has become an indispensable part of life research and practice. A wide variety of cell types are cultured, from viruses to bacteria and fungi, from human cells to animal and plant cells. Some cells and tissues can be grown in suspension, but a considerable number of mammalian cells require surface attachment. 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(3) Spindle speed when the thread is threaded