When machining parts on ordinary machine tools, the process personnel should first analyze the parts and make the process specifications of the parts processing, including the machine tools, tools, positioning and clamping methods and cutting amount. Similarly, when machining parts on CNC machine tools, it is necessary to process the parts and formulate the process specifications. At the same time, process parameters, geometric data, etc. should be recorded on the control medium according to the specified information format. The information is input to the numerical control device of the numerical control machine tool, and the numerical control device controls the machine tool to complete the complete processing of the parts. The whole process from the part drawing to the control medium for making CNC machine tools and checking is called the programming of CNC machining, which is called NC programming. CNC programming is an important step in CNC machining. The ideal machining program should not only ensure the production of qualified parts that meet the requirements of the drawings, but also enable the rational use and full play of the functions of the CNC machine tools, so that the CNC machine tools can work safely, reliably and efficiently.
Generally speaking, the main contents of the NC programming process include: analysis of part drawings, process processing, numerical calculation, writing of machining program sheets, production of control media, program verification and first piece trial processing.
First, the specific steps and requirements of NC programming are as follows:
1. Analyze the part drawing First, analyze the material, shape, size, precision, batch, blank shape and heat treatment requirements of the part to determine whether the part is suitable for machining on a CNC machine or suitable for machining on a CNC machine. At the same time, the content and requirements of the processing should be clarified.
2. The process is based on the analysis of the part drawing, the process analysis, the processing method of the part (such as the fixture used, the positioning method of clamping, etc.), the processing route (such as the tool point, the tool change point, the feed route) and Process parameters such as the amount of cutting (such as spindle speed, feed rate, and amount of back-feeding). The analysis and processing of CNC machining process is the premise and basis of NC programming, while NC programming is to program the content of CNC machining process. When formulating the CNC machining process, it is necessary to select the machining plan reasonably, determine the machining sequence, machining route, clamping method, tool and cutting parameters, etc. At the same time, also consider the command function of the CNC machine tool used, give full play to the machine tool's efficiency; The route, correctly select the tool point, the tool change point, reduce the number of tool changes, and make the numerical calculation convenient; reasonably select the starting point, the cutting point and the cutting mode to ensure the smooth cutting process; avoid the interference between the tool and the non-machined surface, Ensure that the processing process is safe and reliable. The contents of the CNC machining process will be described in detail in Chapters 2.3 and 2.4.
3. The numerical calculation calculates the trajectory of the rough and finishing motion of the part according to the geometrical dimensions of the part drawing, the determined routing, and the set coordinate system, and obtains the tool position data. For the contour machining of parts with simple shapes (such as parts composed of straight lines and arcs), calculate the starting point, end point of the geometric element, the center of the arc, the intersection of the two geometric elements or the coordinate value of the tangent point, if CNC The device has no tool compensation function, and also calculates the coordinate value of the motion track of the tool center. For parts with complex shapes (such as parts consisting of non-circular curves and curved surfaces), it is necessary to approximate the line coordinates or arc segments, and calculate the coordinate values ​​of the nodes according to the requirements of machining accuracy. This numerical calculation is generally done by computer. . The contents of the numerical calculations will be described in detail in Chapter 3.
4. Write the machining program list according to the machining route, cutting amount, tool number, tool compensation amount, machine tool auxiliary action and tool movement track, and write the program list of the part processing according to the instruction code and program segment format used by the numerical control system, and check the above two The contents of the steps to correct the errors.
5. The production control medium records the content on the prepared program list on the control medium as input information of the numerical control device. It is sent to the CNC system by manual input or communication transmission of the program.
6. The program verification and the prepared test program and the prepared control medium must be verified and tested before they can be used officially. The method of verification is to directly input the contents of the control medium into the numerical control system, and let the machine run empty to check whether the movement track of the machine tool is correct. On CNC machine tools with CRT graphic display, it is more convenient to use the method of simulating tool and workpiece cutting process, but these methods can only check whether the motion is correct and can not check the machining accuracy of the machined parts. Therefore, the first piece of the part is to be cut. When a machining error is found, analyze the cause of the error, find out the problem, and correct it until the part drawing requirements are met.
Second, the numerical control programming method Numerical control programming is generally divided into manual programming and automatic programming.
1. Manual programming manual programming is done manually from analyzing part drawings, determining machining process, numerical calculation, writing part processing program list, making control medium to program verification. It requires programmers not only to be familiar with CNC instructions and programming rules, but also to have knowledge of CNC machining processes and numerical calculation capabilities. For parts with simple machining shape, small calculation amount and few program segments, manual programming is easy, economical and timely. Therefore, manual programming is still widely used in point machining or contour machining composed of straight lines and arcs. For parts with complex shapes, especially those with non-circular curves, list curves and curved surfaces, manual programming has certain difficulties, the probability of error increases, and sometimes the program cannot be programmed. The program must be programmed automatically. .
2. Automatic programming Automatic programming is the use of computer-specific software to program CNC machining programs. The programmer only needs to use the numerical control language according to the requirements of the part pattern, and the computer automatically performs numerical calculation and post-processing, and writes a part processing program list. The machining program is sent to the CNC machine tool through direct communication to direct the machine tool work. Automated programming makes some programs that are cumbersome to calculate, difficult to program manually, or impossible to program.
summary:
This chapter mainly describes the generation and development of numerical control equipment, the machining principle of CNC machine tools, the characteristics and application of CNC machining and the basic knowledge of CNC programming. The reader is required to understand the process of the generation and development of CNC equipment, the composition of CNC machine tools and the basic functions of each part, and the processing characteristics of CNC machine tools. Master the main content and steps of NC programming, and choose the appropriate processing method according to the shape and production cycle of the part.
The basic course of NC programming must be learned first. This is the foundation. These courses are some of the courses that are popular in the mechanical industry, such as drawing, tolerance measurement, mechanical design, necessary electrical and electronic technology, plc, etc. Of course, you can also go directly to practice without learning theory. If you have the conditions to find a master, it is ok. However, if the current era does not have much room for development, it will be very important to learn from the university. These are all to learn, then the rules of programming on these basics are very simple, but there is a problem that many people are very skilled in programming, but they can't be used in practice. This is because the processing technology has problems, learning The processing technology should be learned before programming, otherwise it is useless to learn programming. This is why some people in the company can get the salary of 7,8 thousand, and the people can't take it. The craft is a very extensive study. Practice and practice, ask more questions, think more, programming can only be carried out after arranging a reasonable process, so remind you that you must study the process, so that NC programming is basically done by you, and tell you, there is CNC The simulation software can help you learn a lot. With the one called Yulong, other software is not cracked. The simulation benefit is that it can be different. Machine tools from different machine manufacturers can be learned, and now Japan's Farak is the most used system, the focus is to learn this, and the other is Siemens, Germany, there are a small number of domestic systems in Guangzhou or Beijing, but not Easy to use, mainly unstable, and there is automatic programming in NC programming, telling you that it is very money-changing. Of course, this is not very simple. If you learn CNC, it is best to go to the mold industry. Some things can only be written by hand. Computer, of course, here to learn the knowledge of the mold, this can be difficult, and then learn automatic programming, now the most advanced software is UG and Por / E, professional is MasterCAM, there are many, I will not raise, In short, as long as you work hard, you can do it.
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