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CNC processing, also known as numerical control processing, refers to the processing of CNC processing tools. Because CNC machining is programmed by computer control processing, therefore, CNC machining has the advantages of stable processing quality, high machining accuracy, high repetition accuracy, complex surface processing, high processing efficiency. In the actual processing process, human factors and operating experience, to a great extent, will affect the final processing quality. Below, let us take a look, an old driver with ten years of CNC processing experience, summed up the twelve valuable experience....
1. How to divide CNC processing procedures?
The division of CNC machining procedures can be generally carried out according to the following methods:
1, the tool concentration sequence method is according to the tool division process, with the same tool CNC machining parts on all the parts can be completed. Use the second knife and the third knife to do whatever else they can do. This can reduce the number of tool changes, compress the headway time, and reduce unnecessary positioning errors.
2, in order to process parts of CNC processing content of a lot of parts, according to its structural characteristics will be processed into several parts, such as shape, shape, surface or plane, etc. Generally first processing plane, positioning surface, after processing holes; First, simple geometry is processed, and then complex geometry is processed. The parts with lower precision are processed first, and then the parts with higher precision requirements are processed.
3, to rough, fine CNC machining sequence method for easy CNC machining deformation of parts, due to the possible deformation after rough machining and need to be calibrated, so generally speaking, where to rough, fine machining to separate the process. To sum up, in the division of the process, we must depend on the structure of the parts and technology, the function of the machine tool, parts CNC processing content, the number of installation and the production organization of the unit flexible grasp. The principle that the proposal uses working procedure to concentrate additionally still uses working procedure to disperse principle, want to determine according to actual situation, but do one's best to be reasonable certainly.
II. What principles should be followed in the arrangement of CNC processing sequence?
The arrangement of the processing sequence should be based on the structure of the parts and the condition of the blank, as well as the need to consider the positioning and clamping, the focus is not to destroy the rigidity of the workpiece. In general, the sequence should be carried out according to the following principles:
1, the CNC processing of the last process can not affect the positioning and clamping of the next process, and the general machine tool processing process interspersed in the middle should also be considered comprehensively.
2, advanced line of inner shape and inner cavity processing sequence, after the shape of the processing process.
3, with the same positioning, clamping way or the same knife CNC processing process is best connected, in order to reduce the number of repeated positioning, tool change and move the number of pressure plate.
4, in the same installation of a number of processes, should first arrange for the workpiece rigid destruction of small processes.
Three, the workpiece clamping method should pay attention to what aspects?
The following three points should be paid attention to when determining the positioning datum and clamping scheme:
1, strive to design, process, and programming calculation of the benchmark unity.
2, minimize the number of clamping, as far as possible to be able to CNC machining all the surface to be processed after a positioning.
3, avoid the use of machine occupation manual adjustment scheme.
4, jig to open, its positioning, clamping mechanism can not affect CNC processing in the knife (such as collision), encounter such a case, can be used with vise or add bottom plate screw clamping.
Four, how to determine the knife point is reasonable? What is the relationship between the workpiece coordinate system and the programming coordinate system?
1, the tool point can be located on the processed parts, but pay attention to the tool point must be the reference position or has been finished parts, sometimes in the first process after the tool point is damaged by CNC processing, will lead to the second process and later on the tool point can not be found, Therefore, in the first process of knife alignment, we should pay attention to setting up a relative alignment position where there is a relatively fixed size relationship with the positioning benchmark, so that we can find the original alignment point according to the relative position relationship between them. This relative tool position is usually located on the machine table or fixture. The selection principle is as follows:
1) Finding right is easy.
2) Easy programming.
3) the knife error is small.
4) Convenient and accessible for inspection during processing.
2. The origin position of the workpiece coordinate system is set by the operator himself. After the workpiece is clamped, it is determined by the tool. Once the workpiece coordinate system is fixed, it is generally not changed. The workpiece coordinate system and the programming coordinate system must be unified, that is, during processing, the workpiece coordinate system and the programming coordinate system are consistent.
Five, how to choose the Dao route?
The path of the cutter is the path and direction of the cutter relative to the workpiece in the process of exponentially controlled machining. The reasonable choice of machining route is very important, because it is closely related to the CNC machining accuracy and surface quality of the parts. In determining the knife route is mainly to consider the following points:
1, to ensure the machining accuracy of parts.
2, convenient numerical calculation, reduce programming workload.
3. Seek the shortest CNC machining route, reduce the empty tool time to improve the CNC machining efficiency.
4. Minimize the number of program segments.
5. To ensure the roughness of the workpiece contour surface after CNC processing, the final contour should be processed continuously by the last cutting tool.
6, the advance and exit of the tool (cutting and cutting) route should also be seriously considered, in order to minimize the stop at the contour (cutting force sudden change caused by elastic deformation) and leave a mark, but also to avoid the vertical knife on the contour surface and scratch the workpiece.
VI. How to monitor and adjust in the process of CNC processing?
After the alignment of the workpiece and the completion of the program debugging, it can enter the automatic processing stage. In the process of automatic machining, the operator should monitor the cutting process to prevent abnormal cutting resulting in workpiece quality problems and other accidents.
The following aspects are considered for monitoring the cutting process:
1, the processing process monitoring rough machining is mainly considered to be the workpiece surface of the excess excess of the rapid removal. In the automatic machining process of the machine tool, according to the set cutting amount, the tool according to the predetermined cutting path automatically cutting. At this time, the operator should pay attention to observe the cutting load change in the process of automatic machining through the cutting load table, according to the bearing force of the tool, adjust the cutting amount, play to the maximum efficiency of the machine tool.
2, cutting in the process of cutting sound monitoring in the automatic cutting process, generally start cutting, the sound of the tool cutting workpiece is stable, continuous, light, at this time the movement of the machine tool is stable. With the cutting process, when there is a hard point on the workpiece or tool wear or tool clamping and other reasons, the cutting process is unstable, the performance of instability is the cutting sound changes, there will be collision between the tool and the workpiece, the machine tool will vibrate. At this time, the cutting amount and cutting conditions should be adjusted in time. When the adjustment effect is not obvious, the machine tool should be suspended to check the condition of the tool and the workpiece.
3, finishing process monitoring finishing, mainly to ensure that the workpiece processing size and processing surface quality, high cutting speed, large feed. At this time, attention should be paid to the impact of the accumulation of debris on the surface of the processing, for the cavity processing, but also attention should be paid to the corner of the machining over cutting and let the knife. To solve the above problems, one is to pay attention to adjust the spraying position of cutting fluid, so that the processing surface is always in the cooling condition; The second is to pay attention to observe the workpiece has been processed surface quality, by adjusting the cutting amount, as far as possible to avoid the change in quality. If the adjustment still has no obvious effect, it should stop to check whether the original program is reasonable. Special attention is paid to the position of the cutter during the suspension inspection or shutdown inspection. If the tool stops in the cutting process, the sudden spindle stops, the workpiece surface will produce tool marks. Generally, stop should be considered when the tool leaves the cutting state.
4, tool monitoring tool quality largely determines the processing quality of the workpiece. In the process of automatic machining, the normal wear condition and abnormal damage condition of the tool should be judged by means of sound monitoring, cutting time control, pause check in the cutting process, workpiece surface analysis and so on. According to the processing requirements, timely processing of the tool, to prevent the occurrence of processing quality problems caused by the tool is not timely processing.
Seven, how to choose a reasonable processing tool? What are the main elements of cutting amount? How many materials are there for cutting tools? How to determine the tool speed, cutting speed, cutting width?
1. Planar milling should be used without regrinding carbide end milling cutter or end milling cutter. General milling, as far as possible to use the second knife processing, the first time to go with the best end milling cutter rough milling, along the workpiece surface continuous cutter. The recommended width of each cutting tool is 60%-75% of the diameter of the tool.
2. End milling cutter and end milling cutter inlaid with carbide blade are mainly used for machining convex table, grooves and box mouth surface.
3, ball knife, round knife (also known as round nose knife) is often used for processing curved surface and variable bevel contour. The ball cutter is used for semi-finishing and finishing. The round knife with carbide cutter is used for opening rough.
What is the function of the processing procedure sheet? What should be included in the process list?
1, the processing program sheet is one of the contents of CNC machining process design, but also need to comply with the operator, the implementation of the procedures, is the specific description of the processing procedures, the purpose is to let the operator clear the content of the program, clamping and positioning, each processing procedures selected by the tool should pay attention to the problem.
2, in the machining program list, should include: drawing and programming file name, the name of the workpiece, the clamping sketch, the program name, the tool used in each program, the maximum depth of cutting, the processing nature (such as rough machining or fine machining), the theoretical processing time, etc.
Nine, numerical control programming to do before the preparation?
After determining the processing technology, we should understand the following before programming:
1, the workpiece clamping mode;
2, the size of the workpiece hair embryo ---- in order to determine the range of processing or whether the need for multiple clamping;
3, the workpiece material ---- in order to choose what kind of tool used for processing;
4, the inventory of the knife has what ---- to avoid in the processing due to no tool to modify the program, if you must use the tool, you can prepare in advance.
10. What are the principles for setting the safe height in programming?
The principle of safe height setting: generally higher than the highest side of the island. Or the programming zero point is set in the highest surface, which can also avoid the risk of collision knife to the greatest extent.
Eleven, after the tool path is programmed, why do we need to carry out post-processing?
Because different machine tools can recognize the address code and the format of NC program is different, so it is necessary to choose the correct post-processing format for the machine tools used to ensure that the program can be programmed.
What is DNC communication?
Program transportation can be divided into CNC and DNC two kinds, CNC refers to the program through the media (such as floppy disk, tape reader, communication line, etc.) to the machine tool memory storage, processing from the memory out of the program for processing. Because the memory capacity is limited by the size, when the program is large, the DNC method can be used for processing. Because the DNC machine can directly read the program from the control computer during processing (that is, it is done while feeding), so it is not limited by the memory capacity.
1. There are three main factors of cutting amount: cutting depth, spindle speed and feed speed. The general principle of cutting dosage selection is: less cutting, fast feed (that is, small cutting depth, fast feed speed)
2, according to the material classification, the tool is generally divided into ordinary hard white steel knife (material for high speed steel), coating tools (such as titanium plating), alloy tools (such as tungsten steel, boron nitride tools, etc.).
If you want to do programming personnel from CNC processing operators, these are the above must know Oh, in addition to the above, what do you think there is also a need to know? Improve efficiency is not also very important, avoid collision knife, empty knife is also to pay attention to it.