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Some Operating Skills and Experience of CNC Lathe Processing

Oct. 30, 2020

CNC Lathe machine manufacturer summarizes the operating skills into the following points.

One, programming skills

Because the precision requirements of processed products are high, the items that need to be considered when programming are:

1. Processing sequence of parts:

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

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

2. Choose reasonable speed, feed and depth of cut according to material hardness:

1) Select carbon steel material with 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 cutting depth are selected for hard alloy. 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.

CNC Lathe

CNC Lathe

Two. Knife setting skills

Tool setting is divided into tool setting instrument setting and direct tool setting. Most of the lathes in our factory do not have tool setting instruments, which are direct tool setting. The following tool setting techniques are 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 the trial cutting tool setting. The outer circle of the part is reduced 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, then the x axis is also aligned; this tool calibration method, even if the machine is powered off, the calibration will not be changed after power on. The tool value is suitable for mass production of the same part for a long time, during which the lathe is closed without re-setting the tool.

Three, debugging skills

After editing the program, the part needs to be tested and debugged after the tool is adjusted. 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 calibration in the coordinate system of the machine tool. The tool moves to the right by 2-3 times of 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 part. After the first part is processed, self-check first to confirm that it is qualified , Look for a full-time inspection and inspection, after the full-time inspection is confirmed to be qualified, this means that the commissioning is over.

Fourth, complete the processing of parts

After the first piece of trial cutting is completed, the parts will be mass-produced, but the first piece's qualification does not mean that the entire batch of parts will be qualified, because in the processing process, the tool will wear out due to the different 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 principles of machining: rough machining first, remove the excess material of the workpiece, and then finish machining; avoid vibration during machining; avoid thermal denaturation of the workpiece during machining. There are many reasons for vibration caused by excessive load. Large; it may be the resonance of 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. We can reduce the vibration by the following methods; reduce the transverse feed and the processing depth, and check Whether the workpiece is clamped firmly, increase the rotation speed of the tool and reduce the rotation speed to reduce resonance. In addition, check whether it is necessary to replace a new tool.

Five, to prevent the collision of CNC lathe experience

Machine tool collision is a great damage to the accuracy of machine tools, 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: one is the input error of the diameter and length of the tool; the other is the input error of the workpiece size and other related geometric dimensions and the initial position of the workpiece; the third is the setting error 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. At this time, collisions are 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 the tool. At this time, once the program is edited incorrectly, the diameter and length of the tool are entered incorrectly, then 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 functions 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 burning smells. The program should be stopped immediately when the abnormal situation is found, and the machine tool can continue to work after the problem of the standby bed is solved.

In short, mastering the operation skills of CNC Lathe machine 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 practical ability, and is an innovative work.

supmc@vip.sina.com 704276900