Summary of 12 experiences of the most popular NC m

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This dictionary is a summary of some experiences summarized by engineers in the long-term actual production process, such as NC machining process, process, selection of common tool parameters, monitoring in the machining process, etc., for your reference

I. question: how to divide the processing procedures

answer: the division of NC machining processes can generally be carried out according to the following methods:

(1) tool centralized sequencing method is to divide processes according to the tools used, and use the same tool to process all the parts that can be completed. Use the second knife and the third knife to complete other parts they can complete. This can reduce the number of tool changes, compress the idle time, and reduce unnecessary positioning errors

(2) for parts with a lot of processing content, the processing part can be divided into several parts according to its structural characteristics, such as inner shape, shape, curved surface or plane. Generally, the plane and positioning surface are processed first, and then the hole is processed; Machining simple geometric shapes first, and then complex geometric shapes; First process the parts with low accuracy, and then process the parts with high accuracy requirements

(3) for parts prone to machining deformation by rough and finish machining sequence method, shape correction is required due to the possible deformation after rough machining, so generally speaking, the processes of rough and finish machining should be separated

to sum up, when dividing the process, we must flexibly grasp it according to the structure and manufacturability of the parts, the function of the machine tool, the number of NC machining contents of the parts, the installation times and the production organization of the unit. In addition, it is suggested to adopt the principle of centralized process or decentralized process, which should be determined according to the actual situation, but we must strive to be reasonable

II. Question: what principles should be followed in the arrangement of processing sequence

answer: the processing sequence should be arranged according to the parts. 7. Pay attention to the movement of the machine, handle it with care, and pay attention to packaging and shock resistance during transportation Considering the structure and blank condition, as well as the need of positioning and clamping, the key is that the rigidity of the workpiece is not destroyed. Generally, the sequence should be carried out according to the following principles:

(1) the processing of the previous process should not affect the positioning and clamping of the next process, and the general machine tool processing process interspersed in the middle should also be comprehensively considered

(2) first carry out the inner cavity processing procedure, and then carry out the contour processing procedure

(3) the process of processing with the same positioning, clamping method or the same knife is best connected to reduce the number of repeated positioning, tool changing and moving the pressing plate

(4) for multiple processes in the same installation, the process with little damage to the rigidity of the workpiece should be arranged first

III. Q: what aspects should be paid attention to in determining the clamping mode of the workpiece

answer: pay attention to the following three points when determining the positioning datum and clamping scheme:

(1) strive to unify the datum of design, process and programming calculation

(2) try to reduce the clamping times, and try to process all the surfaces to be processed after one positioning

(3) avoid using manual adjustment scheme

(4) the fixture should be open, and its positioning and clamping mechanism should not affect the tool walking in processing (such as collision). In such cases, it can be clamped with a vise or with a bottom plate to extract screws

IV. question: how to determine the tool setting point is more reasonable? What is the relationship between workpiece coordinate system and programming coordinate system

1. the tool setting point can be set on the machined part, but pay attention to that the tool setting point must be the reference position or the part that has been precision machined. Sometimes the tool setting point is damaged after the first process, which will make it impossible to find the tool setting point in the second process and after. Therefore, when setting the tool in the first process, pay attention to setting a relative tool setting position where there is a relatively fixed size relationship with the positioning reference, In this way, the original tool setting point can be retrieved according to the relative position relationship between them. This relative tool alignment position is usually set on the machine tool workbench or fixture. The selection principles are as follows:

1) easy alignment

2) convenient programming

3) small tool setting error

4) convenient inspection during processing

2. The origin position of the workpiece coordinate system is set by the operator himself. It is determined by tool setting after the workpiece is clamped. It reflects the distance position relationship between the workpiece and the zero point of the machine 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 machining, the workpiece coordinate system and the programming coordinate system are consistent

v. ask: how to choose the cutting route

tool path refers to the motion path and direction of the tool relative to the workpiece during NC machining. The reasonable selection of machining route is very important, because it is closely related to the machining accuracy and surface quality of parts. When determining the cutting route, the following points are mainly considered:

1) ensure the machining accuracy requirements of parts

2) facilitate numerical calculation and reduce programming workload

3) seek the shortest processing route and reduce the empty tool time to improve the processing efficiency

4) try to reduce the number of program segments

5) ensure the requirements of the roughness of the workpiece contour surface after machining, and the final contour should be processed continuously with the last tool

6) the forward and backward (cut in and cut out) route of the tool should also be carefully considered, so as to minimize the knife marks caused by stopping at the contour (elastic deformation caused by sudden change of cutting force) and avoid scratching the workpiece by cutting vertically on the contour surface

VI. ask: how to monitor and adjust in the processing process

after the workpiece is aligned and the program is debugged, it can enter the automatic processing stage. In the process of automatic machining, the operator should monitor the cutting process to prevent abnormal cutting from causing workpiece quality problems and other accidents

the following aspects are mainly considered in monitoring the cutting process:

1. the main consideration of rough machining is the rapid removal of excess allowance on the workpiece surface. In the automatic machining process of the machine tool, the tool automatically cuts according to the predetermined cutting path according to the set cutting parameters. At this time, the operator

should pay attention to observing the change of cutting load in the automatic machining process through the cutting load table, and adjust the cutting parameters according to the bearing capacity of the tool to give full play to the maximum efficiency of the machine tool

2. monitoring of cutting sound in the process of cutting in the process of automatic cutting, generally, when cutting begins, the sound of the tool cutting the workpiece is stable, continuous and light, and at this time, the movement of the machine tool is stable. With the progress of the cutting process, when there are hard spots on the workpiece, tool wear or tool clamping, the cutting process is unstable. The unstable performance is that the cutting sound changes, the tool and workpiece will collide with each other, and the machine tool will vibrate. At this time, the cutting parameters and cutting conditions should be adjusted in time. When the adjustment effect is not obvious, the machine tool should be suspended and the condition of tools and workpieces should be checked

3. Finish machining process monitoring finish machining is mainly to ensure the machining size and surface quality of the workpiece. The cutting speed is high and the feed rate is large. At this time, attention should be paid to the influence of chip buildup on the machining surface. For cavity machining, attention should also be paid to the over cutting and tool yield at the corner. To solve the above problems, first, we should pay attention to adjusting the spray position of cutting fluid to keep the machining surface in the best] cooling condition at all times; Second, pay attention to the quality of the machined surface of the workpiece, and try to avoid quality changes by adjusting the cutting parameters. If the adjustment still has no obvious effect, stop the machine to check whether the original program is reasonable

pay special attention to the position of the tool when pausing the inspection or stopping the inspection. If the tool stops in the cutting process, the sudden spindle stops rotating, which will cause tool marks on the surface of the workpiece. Generally, shutdown should be considered when the tool leaves the cutting state

4. Tool monitoring the quality of the tool largely determines the processing quality of the workpiece. In the process of automatic machining and cutting, it is necessary to judge the normal wear condition and abnormal damage condition of the tool through sound monitoring, cutting time control, pause inspection during the cutting process, workpiece surface analysis and other methods. According to the processing requirements, the cutting tools should be handled in time to prevent the processing quality problems caused by the cutting tools not being handled in time

VII. Ask: how to reasonably select processing tools? How many factors are there in cutting parameters? How many kinds of cutting tools are there? How to determine the tool speed, cutting speed, cutting width

1. Non regrinding cemented carbide end mills or end mills should be used in plane milling. In general, when milling, try to use the secondary cutting. For the first cutting, it is best to use the end milling cutter for rough milling, and continue cutting along the workpiece surface. The recommended width of each feeding is 60% - 75% of the tool diameter

2. End mills and end mills with carbide inserts are mainly used to process bosses, grooves and box mouth surfaces

3. ball knives and round knives (also known as round nose knives) are often used to process curved surfaces and variable angle contour shapes. Ball knives are mostly used for semi finishing and finishing. The round knives with carbide cutters are mostly used for roughening

VIII. Q: what is the function of the processing program sheet? What should be included in the processing procedure sheet

answer: (1) the processing program list is one of the contents of the NC processing process design, and it is also a procedure that needs to be observed and implemented by the operator. It is a specific description of the processing program. The purpose is to let the operator clarify the content of the program, the clamping and positioning methods, and the problems that should be paid attention to when selecting the cutting tools for each processing program

(II) in the processing program list, it should include: drawing and programming file name, workpiece name, clamping sketch, program name, tool used by each program, maximum depth of cutting, processing nature (such as rough machining or finish machining), theoretical processing time, etc

IX. Q: what preparations should be made before NC programming

answer: after determining the processing technology, you should understand before programming: 1. Workpiece clamping method; 2. Size of workpiece rough embryo ---- in order to determine the scope of processing or whether multiple clamping is required; 3. Material of workpiece ---- in order to select which tool to use for processing; 4. What are the tools in stock? Avoid modifying the program because there is no such tool during processing. If you must use this tool, you can prepare in advance

X. Q: what are the principles for setting the safety height in programming

answer: the setting principle of safety height: generally higher than the highest surface of the island. Or set the programming zero point on the highest side, so as to avoid the danger of knife collision to the greatest extent

Xi. Q: why should post-processing be carried out after the tool path is compiled

answer: because different machine tools can recognize different address codes and NC program formats, it is necessary to select the correct post-processing format for the machine tool used to ensure that the compiled program can run

twelve Q: what is DNC communication

answer: the mode of program transmission can be divided

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