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After engaging in CNC machine tool processing for ten years, I have accumulated some machining skills and experience of CNC machine tools, mainly for CNC programming and parts processing.

CNC Programming:

Because most of our cnc machining parts have high requirements for the accuracy dimensions, the details that need to be considered when programming are:

The processing sequence of the parts:

Drill first and then flat end (this is to prevent shrinkage when drilling);

 

Rough turning first, then fine turning (this is to ensure the accuracy of the parts);

 

The first processing tolerance is large and the final processing tolerance is small (this is to ensure that the surface of the small tolerance size is not scratched and to prevent the deformation of the parts).

Choose a reasonable speed, feed and depth of cut according to the hardness of the material:

1. The carbon steel material chooses high speed, high feed rate and large cutting depth. Such as: 1Gr11, select S1600, F0.2, and cut depth 2mm;

 

2. Low speed, low feed rate and small depth of cut are selected for cemented carbide. Such as: GH4033, select S800, F0.08, and cut depth 0.5mm;

3. Choose low speed, high feed rate and small cutting depth for titanium alloy. Such as: Ti6, select S400, F0.2, and cut depth 0.3mm. Take the processing of a certain part as an example: the material is K414, which is an extra-hard material. After many tests, the final selection is S360, F0.1, and the depth of cut 0.2 before processing qualified parts.

Tools setting:

Tool setting is mainly direct tool setting. The following tool setting techniques refer to direct tool setting.

 

First select the center of the right end face of the part as the tool setting point and set it as the zero point. After the machine returns to the origin, each tool that needs to be used will be set with the center of the right end face of the part as the zero point; when the tool touches the right end face, enter Z0 and click to measure. The measured value will be automatically recorded in the tool compensation value of the tool, which means that the Z-axis tool setting is done, and the X tool setting is a trial cutting tool setting. The outer circle of the part is turned with the tool, and the outer circle value of the machine is measured ( If x is 20mm) input x20, click Measure, the tool compensation value will automatically record the measured value, and then the x-axis is also correct;

 

This tool setting method, even if the machine is powered off, will not change the tool setting value after the power is turned on. It is suitable for mass production of the same part for a long time, during which the lathe is turned off and there is no need to re-calibrate the tool.

Debugging:

After the parts are programmed, the tool needs to be trial cut and debugged. In order to prevent errors in the program and error in the tool setting from causing machine collision accidents, we should first perform idle stroke simulation processing, and perform the calibration in the coordinate system of the machine tool. The tool moves to the right by 2 to 3 times the total length of the part;

 

Then start the simulation processing. After the simulation processing is completed, confirm that the program and tool setting are correct, and then start processing the parts. After the first part is processed, first self-inspect to confirm that it is qualified, and then look for a full-time inspection and check. The full-time inspection confirms that it is qualified. Indicates the end of debugging.

Complete the processing of the parts:

After the first piece of trial cutting is completed, the parts will be mass-produced, but the first piece of qualification does not mean that the entire batch of parts will be qualified, because in the process of processing, the tool will wear out due to the difference in processing materials. If it is soft, the tool wear will be small, the processing material will be hard, and the tool will wear quickly. Therefore, during the machining process, it is necessary to check frequently to increase and decrease the tool compensation value in time to ensure that the parts are qualified.

 

Take a part as an example, the processing material is K414, and the total processing length is 180mm. Because the material is extremely hard, the tool wears very quickly during processing. From the starting point to the end point, the tool wear will produce a slight degree of 10-20mm. Therefore, we must A slight degree of 10-20mm is artificially added in the program, so as to ensure that the parts are qualified.

 

In short, the basic principle of machining: rough machining first, remove the excess material of the workpiece, and then finish machining; avoid vibration during machining; avoid thermal denaturation during workpiece machining. There are many reasons for vibration caused by excessive load. Large; it may be the resonance between the machine tool and the workpiece, or the rigidity of the machine tool may be insufficient, or it may be caused by the tool passivation.Vibration can be reduced by the following methods; reduce the lateral feed and processing depth, check whether the workpiece is clamped firmly, increase the speed of the tool, and reduce the speed to reduce the resonance. In addition, check whether it is necessary to replace a new tool .

The experience of preventing the collision of machine tools:

Machine tool collision is a great damage to the accuracy of the machine tool, and has different effects on different types of machine tools. Generally speaking, it has a greater impact on machine tools with low rigidity. Therefore, for high-precision CNC lathes, collisions must be absolutely eliminated. As long as the operator is careful and masters certain anti-collision methods, collisions can be prevented and avoided.

 

The main reasons for the collision are: one is the input error of the diameter and length of the tool; the other is the input error of the size of the workpiece and other related geometric dimensions and the initial position of the workpiece is incorrect; the third is the setting of the workpiece coordinate system of the machine tool. , Or the zero point of the machine tool is reset during the machining process and changes occur. Machine tool collisions mostly occur during the rapid movement of the machine tool. The collisions that occur at this time are also the most harmful and should be absolutely avoided.

 

Therefore, the operator should pay special attention to the machine tool in the initial stage of executing the program and when the machine tool is changing tools. At this time, once the program is edited incorrectly, and the diameter and length of the tool are entered incorrectly, collisions are likely to occur. At the end of the program, if the NC axis retracts the tool in a wrong sequence, then a collision may also occur.

 

In order to avoid the above collisions, the operator should give full play to the features of the five senses when operating the machine tool, and observe whether the machine tool has abnormal movements, sparks, noises and abnormal noises, vibrations, and burnt odors. If abnormal conditions are found, the program should be stopped immediately, and the machine tool can only continue to work after the standby bed problem is solved.

In short, mastering the operating skills of CNC machine tools is a gradual process and cannot be accomplished overnight. It is based on mastering the basic operation of machine tools, basic machining knowledge and basic programming knowledge.

The operating skills of CNC machine tools are not static, it is an organic combination that requires the operator to give full play to their imagination and hands-on ability, and is an innovative work.

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