How to learn CNC programming well

When processing parts on ordinary machine tools, the craftsman should first analyze the process of the parts, and formulate the process regulations for parts processing, including process parameters such as machine tools, cutting tools, positioning and clamping methods, and cutting parameters. Similarly, when processing parts on CNC machine tools, it is also necessary to analyze the process of the parts and formulate process regulations. The information is input to the CNC device of the CNC machine tool, and the CNC device controls the machine tool to complete the entire processing of the parts. We call the entire process from part drawing to making and checking the control medium of CNC machine tools the programming of CNC machining, or CNC programming for short. NC programming is an important step in NC machining. The ideal processing program should not only ensure the processing of qualified parts that meet the requirements of the drawing, but also enable the functions of the CNC machine tool to be reasonably utilized and fully exerted, so that the CNC machine tool can work safely, reliably and efficiently.
Generally speaking, the main content of the NC programming process includes: analysis of part drawings, process processing, numerical calculation, preparation of processing program sheets, production of control media, program verification and first piece trial processing.
1. The specific steps and requirements of NC programming are as follows:
1. Analyzing the part drawing
First, analyze the material, shape, size, precision, batch size, blank shape and heat treatment requirements of the part, so as to determine whether the part is suitable for processing on a CNC machine tool, or which CNC machine tool is suitable for processing. At the same time, the content and requirements of processing must be clarified.
2. Process processing
On the basis of analyzing the part diagram, conduct process analysis to determine the processing method of the part (such as the tool and fixture used, the clamping and positioning method, etc.), the processing route (such as the tool setting point, tool changing point, feed Route) and cutting parameters (such as spindle speed, feed speed and back cutting amount, etc.) and other process parameters. The analysis and processing of NC machining process is the premise and basis of NC programming, and NC programming is to program the content of NC machining process. When formulating the CNC machining process, it is necessary to reasonably select the processing plan, determine the processing sequence, processing route, clamping method, tool and cutting parameters, etc.; at the same time, the command function of the CNC machine tool used should also be considered to give full play to the effectiveness of the machine tool; shorten the processing time as much as possible. Route, correctly select the tool setting point and tool change point, reduce the number of tool changes, and make the numerical calculation convenient; reasonably select the starting point, entry point and entry method to ensure the smooth entry process; avoid the interference between the tool and the non-processing surface, Ensure the safety and reliability of the processing process, etc. Regarding the content of CNC machining technology, we will introduce it in detail in Section 2.3 and Section 2.4 of Chapter 2.
3. Numerical Calculation
According to the geometric size of the part drawing, the determined process route and the set coordinate system, calculate the trajectory of the rough and finish machining movement of the part, and obtain the tool position data. For the contour processing of parts with relatively simple shapes (such as parts composed of straight lines and arcs), it is necessary to calculate the coordinate values ​​of the starting point, end point, center of the arc, intersection point or tangent point of two geometric elements,If the numerical control device has no tool compensation function, it is necessary to calculate the coordinate value of the movement path of the tool center. For parts with relatively complex shapes (such as parts composed of non-circular curves and curved surfaces), it is necessary to approach them with straight line segments or arc segments, and calculate the node coordinates according to the requirements of machining accuracy. This numerical calculation generally needs to be done by a computer. . The content of numerical calculation will be introduced in detail in Chapter 3.
4. Write processing program list
According to the processing route, cutting amount, tool number, tool compensation amount, machine tool auxiliary action and tool movement track, write the part processing program list according to the format of the command code and program segment used by the CNC system, and correct it Check the content of the above two steps and correct the errors.
5. Make control medium
Record the contents of the compiled program list on the control medium as the input information of the numerical control device. It is sent to the CNC system through manual input or communication transmission of the program.
6. Program verification and first piece trial cutting
The programmed program sheet and prepared control medium must be verified and trial cut before they can be officially used. The method of verification is to directly input the content on the control medium into the numerical control system, and let the machine tool run dry to check whether the movement track of the machine tool is correct. On the CNC machine tool with CRT graphic display, it is more convenient to use the method of simulating the cutting process of the cutting tool and the workpiece to check, but these methods can only check whether the movement is correct, and cannot check the machining accuracy of the processed parts. Therefore, the first piece trial cutting of the part is carried out. When a machining error is found, analyze the cause of the error, find out the problem, and correct it until it meets the requirements of the part drawing.
Second, the method of NC programming
NC programming is generally divided into manual programming and automatic programming.
1. Manual programming
Manual programming is to analyze the part pattern, determine the processing process, numerical calculation, write the part processing program list, make the control medium and check the program. It requires programmers not only to be familiar with NC instructions and programming rules, but also to have knowledge of NC machining technology and numerical calculation capabilities. For parts with simple machining shapes, small amount of calculation, and few program segments, it is easier, more economical and timely to use manual programming. Therefore, manual programming is still widely used in point-to-point machining or contour machining composed of straight lines and arcs. For parts with complex shapes, especially those composed of non-circular curves, list curves and curved surfaces, it is difficult to program manually, the probability of error increases, and sometimes it is even impossible to program, and the program must be programmed by automatic programming. .
2. Automatic programming
Automatic programming is the use of computer-specific software to compile NC machining programs. The programmer only needs to use the numerical control language according to the requirements of the part drawing, and the computer automatically performs numerical calculation and post-processing to write the part processing program sheet, and the processing program is sent to the CNC machine tool through direct communication to direct the machine tool to work. Automatic programming makes some programs that are cumbersome to calculate, difficult or impossible to program by handsequence can be successfully completed.
This chapter mainly describes the generation and development of CNC equipment, the processing principle of CNC machine tools, the characteristics and application of CNC machining, and the basic knowledge of CNC programming. Readers are required to understand the production and development process of CNC equipment, the composition of CNC machine tools, the basic functions of each part, and the processing characteristics of CNC machine tools. Master the main content and steps of NC programming, and be able to choose the appropriate processing method according to the shape of the part and the production cycle.
You must first learn the basic courses of NC programming. This is the foundation. These courses are some courses commonly used in the mechanical industry, such as phase drawing, tolerance measurement, mechanical design, necessary electrical and electronic technology, plc, etc. Of course, you can also go directly to practice without studying theory. If you have the conditions, you can find a master. However, if you do this in the current era, there will not be much room for development in the future. These are all things to learn, so it is very simple to learn programming rules based on these, but there is a problem that many people are very proficient in programming, but they can’t use it in practice. Processing technology should be learned before programming, otherwise it is useless to just learn programming. This is why some people in the company can get the salary of 7,000 or 8,000, but others cannot get it. Craftsmanship is a very extensive knowledge. Practice, ask more questions, think more, programming can only be carried out after arranging a reasonable process, so I remind you to study the process, so that NC programming is basically done by you, and let me tell you, there are NC Simulation software can help you learn to a large extent. Use the one called Yulong, other software is not cracked. The advantage of simulation is that you can learn from different systems or machine tools from different machine tool manufacturers. The most used system, focus on learning this, the other is Siemens in Germany, there are still a small number of domestic systems in Guangzhou or Beijing, but it is not easy to use, mainly because of instability, and there are automatic programming in NC programming, Tell you that it is very easy to transfer money. Of course, this is not easy. If you want to learn CNC, it is best to go to the mold industry. Some things cannot be written by hand and you can only use a computer. Of course, you have to learn the knowledge of molds here. This is very difficult. Then learn For automatic programming, the most advanced software is UG and Por/E, and the more professional one is MasterCAM. There are many, so I won’t list them here.

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