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With the rapid development of mechanical processing methods, machining CNC machining has become the main processing methods, the level of national representatives of NC machining level of development, and even has become a national industrial development to measure the level of standards. NC machinery manufacturing industry as a way epresentative of advanced processing, which contribute to its processing technology progress and economic growth. And NC programming for NC machining of a more important part in achieving the process automation, higher precision and machining quality, shorten product development and production cycle has played a very important role. NC Program for improving the quality and efficiency, for improving the competitiveness of manufacturing enterprises is very important significance. Affect the accuracy of CNC machine there are many factors. Including machine tools, tools, fixtures and other manufacturing error, installation error, the use of wear and tear and so directly affect the machining accuracy of work piece. In other words, the technology of processing the system will produce a variety of errors, thereby changing the cutting tool and work piece movement in the mutual position in relation to affect a variety of precision parts. Therefore, production of machine tools in the design process of a combination of factors must be considered on the machining accuracy, but also consider the production efficiency. The analysis and study of the content on the CNC machine tool design, manufacturing has a certain significance.CNC machining process is widely used, however, optimization and simulation of CNC machining capacity is also weak. Enterprises and schools usually use commercial NC programming, CAD / CAM software system automatically generates NC system, but the process requires manual developed, the program needs its own establishment, because of the lack of uniform standards and optimize the database (such as cutting parameters database engineering database, etc.) support, CNC machining process so that there are still some problems, different people the same the same CNC machine tool parts, the result would be different, resulting in a numerical control programming a craft-like, similar to the part number of samples line of development unreasonable number of technology, human factors and relatively large, so the lower the efficiency of NC program, which greatly restricted the development of NC technology. In response, the process of CNC machining accuracy and efficiency of production is necessary. This can effectively use existing equipment, but also can eliminate the error caused by human factors. Thus, improve the utilization of CNC machine tools and materials to improve the machining accuracy and productivity. CNC training on the school’s students and have great production value.In this study, the NC lathe, machining accuracy and efficiency of optimization problems.Test Equipment Selection Central Century Star 21T CNC lathe. Although the central CNC lathe machining processes can be many, we select only the processing processing cylindrical cylinder test, simple to understand, convenient and reliable. In the course of processing, processing, there are many paths, choose the G71 format for processing test. In the programming format, respectively, to change the size of one parameter, other parameters are fixed, the processed parts using multiple measurement tools to accurately measure, more precision the size of the level of production efficiency. Main evaluation parameters are: cutting the three elements, namely, cutting speed, feed rate, volume, fed knife; shorten production time-piece; reduce overhead time.Workpiece material selection ?30 45 # round steel. Select 93°left side tool carbide machine folder External Turning Tool, select the dimensional accuracy of vernier caliper, measure the surface roughness measuring instrument choice quality. Obtain large amounts of data, according to the data plotted curve graph, then the best graphics of curve parameters.In the other parameters unchanged, namely to change the rough turning spindle speed, feed rate of crude and refined car into a vehicle speed, precision turning spindle speed, cutting margin crude car, and then measuring workpiece size, surface roughness and machining time to determine the precision and efficiency.CNC Lathe with tool material YT15 unchanged, workpiece material made of aluminum, cylindrical size, length, and 45 steel the same, other things being equal circumstances, to re-do the above tests, to verify the machining accuracy and productivity.A pilot program: The Rough feed rate, spindle speed fine cars, fine cars feed rate, cutting depth of a certain situation, Rough spindle speed on the machining accuracy have a significant effect, productivity and gross vehicle spindle speed has nothing to do. Tested contrast, the best value for Rough spindle speed 600r/min.Test program 2: In the rough turning spindle speed, spindle speed fine cars, fine cars cutting margin, gross margin does not change the car cutting the case, Rough feed rate to 160mm/min in 80mm/min vary, from curve obtained: Rough feed speed on the machining accuracy have a significant effect, no significant effect on productivity. Tested contrast, the crude feed rate car best value 150mm/min. Fine feed rate car best value 100mm/min.Test program 3: When crude vehicle spindle speed, feed rate of crude cars, fine cars feed rate, cutting deep rough cars, fine cars must cut depth, the fine car at 800r/min to 1600r/min spindle speed was varied between , concluded from the curve: precision turning spindle speed on the machining accuracy have a significant effect, precision turning spindle speed has no effect on productivity. Tested contrast, refined the best value car spindle speed 1200r/min.Four pilot programs: When the provisions of rough turning spindle speed, feed rate of crude cars, fine cars spindle speed, feed rate of fine cars, fine cars cutting margin, the gross margin in the car cutting varied between 1mm to 3.2mm, processing a large number of mechanical parts, for tracking and concluded: Rough cut margin on the machining accuracy and productivity are significant. For comparison, the best value for Rough Cutting margin 2mm-2.5mm.CNC Lathe with tool material YT15 unchanged, workpiece material made of aluminum, cylindrical size, length, and 45 steel the same, other things being equal circumstances, to re-do the above tests, to verify the machining accuracy and productivity. Because after a lot of tests, but also do a lot of aluminum parts which prove to be reliable conclusions.
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