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In CNC Machining,Six Experiences

- Mar 22, 2018 -

In CNC Machining, You Do Not Know Six Experiences


Because of the complexity of CNC machining (such as different machine tools, different materials, different tools, different cutting methods, different parameter settings, etc.), it is determined that the number of CNC machining (whether it is processing or programming) must reach a certain level. The level must go through a relatively long period of time. The following is a summary of some of the experiences gathered by the engineers in the long-term actual production process, related to the selection of CNC machining processes, processes, common tool parameters, and monitoring during processing. For your reference.

First, how to divide the processing process?

The division of CNC machining processes can generally be carried out according to the following methods:

1. The tool-centralized division method is to divide the process according to the used tool and use the same tool to process all the parts that can be completed on the part. Use the second knife and the third to complete other parts that they can complete. This reduces the number of tool changes, compresses the idle time, and reduces unnecessary positioning errors.

2. The part-sequential method for processing parts For parts with many processing contents, the processing part can be divided into several parts according to its structural characteristics, such as inner shape, outer shape, curved surface or plane. The general processing plane, positioning surface, after processing hole; first processing a simple geometry, and then processing a complex geometry; the first processing of the lower accuracy of the site, and then processing a higher precision of the site.

3, the rough, fine processing of the order of the law for the parts that are prone to deformation, due to deformation may occur after roughing shape correction, so in general, where you want to rough, fine processing must be separated from the process. To sum up, in the process of division, it must be based on the structure and craftsmanship of the part, the function of the machine tool, the number of parts in the numerical control process, the number of installations, and the organizational structure of the unit. It is also recommended that the principle of concentration of processes or the principle of dispersion of processes be adopted. It should be determined based on actual conditions, but it must be reasonable.

2. What principles should be followed in the arrangement of processing sequences?

The arrangement of the processing sequence should be based on the structure of the part and the condition of the blank, as well as the need for positioning and clamping. The main point is that the rigidity of the workpiece is not destroyed.

The order should generally be based on the following principles:

1, the processing of the previous process can not affect the positioning and clamping of the next process, the middle of the general machine tool processing process should also be considered comprehensively.

2, first internal cavity plus process, after the shape processing process.

3, the same positioning, clamping or the same knife processing process is best connected to reduce the number of repeated positioning, the number of tool change and the number of moving platen.

4. In multiple processes performed in the same installation, the process of rigidly destroying the workpiece should be arranged first.

Third, the determination of the workpiece clamping method should pay attention to those aspects?

1. Strive for the unification of design, process, and programming calculations.

2. Minimize the number of fixtures as much as possible so that all surfaces to be machined can be machined after one positioning.

3, to avoid the use of manual adjustment program.

4, the fixture to open, its positioning, clamping mechanism can not affect the processing of the knife (such as the collision), in such cases, you can use the vise or add the bottom extraction screw clamping way.

Fourth, how to determine the knife point is more reasonable? What is the relationship between the workpiece coordinate system and the programming coordinate system?

1. The tool point can be set on the part to be machined, but note that the tool point must be the reference position or the part that has been finished. Sometimes the tool point is destroyed after the first operation, which will lead to the second There is no way to search for the cutting point in the process and afterwards. Therefore, when setting the knife in the first process, it is necessary to set up a relative cutting position in the place where there is a relative fixed size relationship with the positioning reference. This can be found based on the relative position relationship between them. Back to the original knife. This relative counter knife position is usually set on the machine table or fixture.

The selection principle is as follows:

1) It is easy to find.

2) Programming is convenient.

3) The tool setting error is small.

4) Inspection is convenient and can be checked 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, which reflects the distance and position relationship between the workpiece and the machine zero point. Once the workpiece coordinate system is fixed, it is generally not changed. Both the workpiece coordinate system and the programming coordinate system must be unified. That is, the workpiece coordinate system and the programming coordinate system are the same when machining.

Fifth, how to choose the route?

The cutting path is the trajectory and direction of the tool relative to the workpiece during the index control process. The rational choice of processing route is very important because it is closely related to the precision and surface quality of the parts.

The following points are mainly considered in determining the route of the knife:

1, to ensure the accuracy of parts processing requirements.

2, easy numerical calculation, reduce the programming workload.

3, seek the shortest processing route, reduce the empty knife time to improve processing efficiency.

4, to reduce the number of program segments.

5, to ensure the roughness of the workpiece contour surface after processing requirements, the final contour should be arranged for the last pass of continuous processing.

The tool's advance and retract knife (cut-in and cut-out) routes should also be carefully considered to minimize knife-cut at the contour (abrupt changes in cutting force resulting in elastic deformation) leaving the tool marks, and also to avoid vertical cutting under the profile surface And scratch the workpiece.

Sixth, how to monitor and adjust during processing?

After the workpiece is corrected and the program is debugged, it can enter the automatic processing stage. In the automatic processing, the operator must monitor the cutting process to prevent the occurrence of abnormal cutting quality problems and other accidents.

The monitoring of the cutting process mainly considers the following aspects:

1, the process of monitoring The main consideration of roughing is the rapid removal of excess surface of the workpiece surface. In the automatic machining process of the machine tool, according to the set cutting amount, the tool is automatically cut according to a predetermined cutting trajectory. At this time, the operator should pay attention to the change of the cutting load in the automatic machining process through the cutting load table, adjust the cutting amount according to the condition of the bearing capacity of the tool, and exert the maximum efficiency of the machine tool.

2. Monitoring of cutting sound in the cutting process In the automatic cutting process, when the cutting process is generally started, the sound of the tool cutting workpiece is stable, continuous, and brisk, and the movement of the machine tool is stable at this time. With the progress of the cutting process, when the workpiece has a hard point or tool wear or tool clips and other reasons, the cutting process appears unstable, unstable performance is the change of the cutting sound, the tool and the workpiece will appear between the impact Sound, the machine 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 paused to check the status of the cutting tools and workpieces.

3, finishing process monitoring and finishing, mainly to ensure that the workpiece size and machining surface quality, high cutting speed, a large amount of feed. At this time, attention should be paid to the effect of the built-up edge on the machining surface. For the cavity processing, attention should also be paid to the cutting and turning of the corner. To solve the above problems, one should pay attention to adjust the spray position of cutting fluid, so that the surface is always in the cooling condition; Second, we must pay attention to observe the workpiece surface quality, by adjusting the cutting amount, as far as possible to avoid changes in quality. If the adjustment still has no significant effect, the original procedures for the shutdown inspection should be compiled to make it reasonable. Special attention should be paid to the position of the tool when pausing or stopping the inspection. If the tool stops during the cutting process, a sudden spindle stop will cause a tool mark on the workpiece surface. Should generally consider stopping when the tool leaves the cutting state.

4. Tool monitoring The quality of the tool largely determines the quality of the workpiece. In the automatic machining and cutting process, the normal wear condition and abnormal damage condition of the tool are judged through sound monitoring, cutting time control, pause inspection during cutting process, and workpiece surface analysis. According to the processing requirements, the tool should be processed in time to prevent the processing quality problem caused by the tool not being processed in time.

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