12 CNC machining experience summary, what is CNC machining? Programmers must see!

CNC machining, refers to machining with CNC machining tools. Because CNC machining is controlled by computer after programming, CNC machining has the advantages of stable processing quality, high machining precision, high repeatability, complex machining surface and high machining efficiency. In the actual processing process, human factors and operational experience will largely affect the final processing quality. Let’s take a look at an old driver who has 10 years of CNC machining experience and summed up the twelve valuable experiences… 1 How to divide the cnc processing process? The division of the CNC cnc machining process can generally be carried out as follows: The tool concentration sorting method is to divide all the parts that can be completed on the part by the same tool cnc according to the tool division process. Use the second knife and the third handle to complete other parts that they can complete. This reduces the number of tool changes, compresses the dead time, and reduces unnecessary positioning errors. According to the processing part sorting method, for the parts with a lot of cnc processing content, the processing part can be divided into several parts according to its structural features, such as inner shape, shape, curved surface or plane. Generally, the plane, the positioning surface, and the rear processing hole are first processed; the simple geometric shape is processed first, and the complex geometric shape is processed; the lower precision part is processed first, and the processing precision requirement is higher. The coarse and fine cnc processing and sorting method is necessary for the deformation of the parts that are prone to cnc machining deformation due to possible deformation after rough machining. Therefore, in general, the rough and fine machining are required to separate the processes. In summary, when dividing the process, it must be based on the structure and process of the part, the function of the machine tool, the amount of CNC cnc machining content, the number of installations and the unit’s production organization status. It is also recommended to adopt the principle of process concentration or the principle of process dispersion, which should be determined according to the actual situation, but it must be reasonable. What principles should be followed for the arrangement of 2cnc processing order? The order of the processing sequence should be considered according to the structure of the part and the condition of the blank, as well as the need for positioning and clamping. The key point is that the rigidity of the workpiece is not destroyed. The order should generally be based on the following principles: The cnc processing of the previous process can not affect the positioning and clamping of the next process, and the intermediate machining process must be considered in the middle. First, the inner cavity is added to the inner cavity, and then the outer shape processing step is performed. It is preferable to connect the processes of the same positioning, clamping or the same tool cnc to reduce the number of repeated positioning, the number of tool changes and the number of moving plates. In the multiple processes carried out in the same installation, the process of miniaturizing the rigidity of the workpiece should be arranged first. 3 The determination of the workpiece clamping method should pay attention to those aspects? The following three points should be noted when determining the positioning reference and clamping scheme: Strive to unify the benchmarks of design, process, and programming calculations. Minimize the number of clamping operations, and as far as possible, can process all the surfaces to be processed after one positioning. Avoid using the manual adjustment program. The fixture should be opened smoothly, and its positioning and clamping mechanism can not affect the cutter in the cnc machining (such as collision). When such a situation is encountered, the clamp can be clamped by means of a vise or a bottom plate. 4. How to determine the correct point of the knife? What is the relationship between the workpiece coordinate system and the programmed coordinate system? 1. The tool point can be set on the machined part, but note that the tool point must be the reference position or the finished part. Sometimes the tool point is destroyed by cnc after the first process, which will lead to the second. There is no way to find the tooling point and the subsequent tool setting point. Therefore, when pairing the tool in the first process, pay attention to set a relative tool setting position in a relatively fixed size relationship with the positioning reference, so that the relative positional relationship between them can be based on Find the original knife point. This relative pair of tool positions is usually located on the machine table or fixture. The selection principles are as follows: It is easy to find. Easy to program. The tool setting error is small. It is convenient and easy to check during processing. 2. The origin position of the workpiece coordinate system is set by the operator. After the workpiece is clamped, it is determined by the tool setting. It reflects the positional relationship between the workpiece and the zero point of the machine tool. Once the workpiece coordinate system is fixed, it is generally not changed. Both the workpiece coordinate system and the programmed coordinate system must be uniform, that is, the workpiece coordinate system and the programmed coordinate system are identical during machining. 5 How to choose the route? The path of the tool is the trajectory and direction of the tool relative to the workpiece during the index control process. A reasonable choice of processing route is very important because it is related to the cnc machining accuracy and surface quality of the part. The following points are mainly considered in determining the route: Guarantee the machining accuracy requirements of the parts. Convenient numerical calculations reduce programming effort. Seek the shortest cnc processing route and reduce the emptying time to improve cnc processing efficiency. Minimize the number of blocks. To ensure the roughness of the workpiece surface after the machining of the cnc, the final contour should be arranged for the last pass to be continuously processed. The path of the tool’s advance and retreat (cut in and cut out) should also be carefully considered to minimize the need to stop the knife at the contour (the sudden change of the cutting force causes elastic deformation) and leave the tool mark, and also avoid the vertical knife on the contour surface. Scratch the workpiece. 5 How to monitor and adjust during cnc processing? After the workpiece is aligned and the program is debugged, it can enter the automatic machining stage. During the automatic machining process, the operator monitors the cutting process to prevent workpiece quality problems and other accidents caused by abnormal cutting. The following aspects are mainly considered for monitoring the cutting process: Machining Process Monitoring Roughing is primarily concerned with the rapid removal of excess allowance on the surface of the workpiece. During the automatic machining of the machine tool, the tool automatically cuts according to the predetermined cutting path according to the set cutting amount. At this time, the operator should pay attention to observe the change of the cutting load during the automatic machining process through the cutting load table, adjust the cutting amount according to the bearing capacity of the tool, and maximize the efficiency of the machine tool. Monitoring of cutting sound during cutting During the automatic cutting process, the cutting of the workpiece is generally stable, continuous and brittle when the cutting starts. At this time, the movement of the machine is stable. As the cutting process progresses, the cutting process becomes unstable when there are hard spots on the workpiece or tool wear or tool feeding. The unstable performance is that the cutting sound changes, and the tool and the workpiece will collide with each other. Sound, the machine will vibrate. At this time, the cutting amount and cutting condition should be adjusted in time. When the adjustment effect is not obvious, the machine tool should be suspended, and the tool and workpiece condition should be checked. The finishing process is supervised, mainly to ensure the machining size and surface quality of the workpiece, and the cutting speed is high. The feed rate is large. At this point, we should pay attention to the impact of the built-up edge on the machined surface. For cavity machining, we should also pay attention to the machining of the cut and the knife at the corner. For the solution of the above problems, one should pay attention to adjust the spray position of the cutting fluid, so that the machining surface is always in the cooling condition; the second is to observe the quality of the machined surface of the workpiece, and to avoid the change of quality as much as possible by adjusting the cutting amount. If the adjustment still has no obvious effect, it should be reasonable to stop the inspection of the original program. It is important to note that when suspending or stopping the inspection, pay attention to the position of the tool. If the tool stops during the cutting process, a sudden spindle stop will cause a tool mark on the surface of the workpiece. Generally, stop the machine when the tool leaves the cutting state. The quality of the tool monitoring tool determines the quality of the workpiece. In the automatic machining and cutting process, it is necessary to judge the normal wear condition and abnormal damage of the tool through sound monitoring, cutting time control, pause check during cutting, and surface analysis of the workpiece. According to the processing requirements, the tools should be processed in time to prevent the processing quality problems caused by the tools not being processed in time. 7 How to choose a reasonable processing tool? What are the major factors in the amount of cutting? Are there tools for several materials? How to determine the tool speed, cutting speed, cutting width? Non-reground carbide end mills or end mills should be used for face milling. Generally, when milling, try to use secondary cutting. The first pass is preferably rough milling with end mill and continuous cutting along the surface of the workpiece. The width of each pass is recommended to be 60{ec7b4eaba9b93c1d1818e56d037a7bd5060acd8bbffe9e00d56fc6169c59d028} – 75{ec7b4eaba9b93c1d1818e56d037a7bd5060acd8bbffe9e00d56fc6169c59d028} of the tool diameter. End mills and end mills with carbide inserts are mainly used for machining bosses, grooves and box faces. Ball knives and round knives (also known as round nose knives) are often used to machine curved surfaces and beveled contours. Ball knives are mostly used for semi-finishing and finishing. Round knives with carbide cutters are often used for roughing. 8 What is the function of the processing program list? What should be included in the processing program list? The machining program list is one of the contents of the NC machining process design. It is also a procedure that requires the operator to follow and execute. It is a specific description of the machining program. The purpose is to let the operator clarify the contents of the program, the clamping and positioning methods, and the various machining programs. The selected tool should be concerned with the problem and so on. In the machining program list, it should include: drawing and programming file name, workpiece name, clamping sketch, program name, tool used in each program, maximum depth of cutting, processing properties (such as roughing or finishing), theory Processing time, etc. 9 What should I do before CNC programming? After determining the processing technology, you should know before programming: Workpiece clamping method; the size of the workpiece blank —- to determine the scope of processing or whether multiple clamping is required; the material of the workpiece —- to choose which tool to use for processing; — Avoid modifying the program during machining because there is no such tool. If you must use this tool, you can prepare it in advance. 10 What are the principles for setting the safe height in programming? The principle of setting the safety height: generally higher than the highest point of the island. Or set the programming zero point to the highest side, so as to avoid the danger of collision. After the tool path is programmed, why do you need post-processing? Because different machine tools can recognize the address code and NC program format, it is necessary to select the correct post-processing format for the machine to ensure that the programmed program can run. 12 What is DNC communication? The mode of program transmission can be divided into two types: CNC and DNC. The CNC refers to the program being transported to the memory of the machine tool through media medium (such as floppy disk, tape reader, communication line, etc.), and the program is transferred from the memory during processing. machining. Since the capacity of the memory is limited by the size, when the program is large, the DNC method can be used for processing. Since the machine tool directly reads the program from the control computer during the DNC processing (that is, it is done while sending), it is not subject to the memory capacity. Subject to size. There are three major factors in the amount of cutting: depth of cut, spindle speed and feed rate. The general principle of the choice of cutting amount is: less cutting, fast feed (ie, small cutting depth, fast feed rate), according to the material classification, the tool is generally divided into ordinary Hard white steel knives (materials are high speed steel), coated tools (such as titanium plating, etc.), alloy tools (such as tungsten steel, boron nitride tools, etc.). If you want to switch from cnc machine operators to programmers, you must know the above. Besides, do you think there is anything you need to know? Is it important to improve efficiency? Is it also important to avoid collisions and empty knives?