I have been operating a heavy duty cnc lathe machine for ten years in a blink of an eye. I have accumulated some CNC lathe machining skills and experience. Today, I will discuss with you colleagues.
Due to frequent replacement of processed parts and limited factory conditions, we have been programming ourselves, setting tools ourselves, debugging and completing parts processing by ourselves for ten years. In summary, the operating skills are divided into the following points:
Programming skills
Because we have high requirements for the accuracy of processed products, things that need to be considered when programming are:
First, consider the processing order of the parts:
1. Drill first and then flat end (this is to prevent shrinkage when drilling);
2. Rough turning first, then fine turning (this is to ensure the accuracy of parts);
3. 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).
Drilling process
According to the hardness of the material, choose a reasonable speed, feed and depth of cut:
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 cutting depth 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.
Knife setting skills
Tool setting is divided into tool setting instrument setting and direct tool setting. In my original work, some lathes do not have tool setting instruments, which are direct tool setting. The following tool setting techniques are direct tool setting.
Common tool setting instruments
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, which means that the Z-axis tool is set
X tool setting is a trial cutting tool setting. Use the tool to turn the outer circle of the part to be less. Measure the value of the outer circle of the car (such as x is 20mm) and enter x20, click Measure, the tool compensation value will automatically record the measured value, at this time x The shaft is also right;
Even if the machine is powered off, this tool setting method 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 recalibrate the tool.
Debugging skills
After the parts are programmed, the tool needs to be trial cut and debugged, in order to prevent errors in the program and errors in the tool setting, which may cause machine collision accidents.
We should first perform idle-travel simulation processing, in the coordinate system of the machine tool, move the tool to the right by 2-3 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 the calibration. The parts are processed. After the first part is processed, the first part is self-inspected to confirm that it is qualified, and then a full-time inspection is found. After the full-time inspection is confirmed to be qualified, the commissioning is completed.
Finish processing of 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 processing process, the tool will wear out due to the different processing materials. If the tool is soft, the tool wear is small, and the processing material is hard, and the tool wears quickly. Therefore, in the process of processing, it is necessary to check frequently to increase and decrease the tool compensation value in time to ensure that the parts are qualified.
Tool wear process and blunt standard
Take the parts we have processed before 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 artificially add 10 in the program. ——A slight degree of 20mm, so as to ensure the qualification of the parts.
In short, after talking so much with everyone, I think 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 and vibration during workpiece machining There are many reasons for the occurrence, which may be excessive load; 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 passivation of the tool. We can reduce the vibration by the following methods; 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.
Experience in preventing machine tool collisions
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.
I think the main reason for the collision:
☑ The diameter and length of the tool are entered incorrectly;
☑ The size of the workpiece and other related geometric dimensions are entered incorrectly, and the initial position of the workpiece is incorrectly positioned;
☑ The workpiece coordinate system of the machine tool is set incorrectly, or the zero point of the machine tool is reset during the machining process, resulting in a change. 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 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-mentioned collisions, the operator must give full play to the functions of the facial features when operating the machine tool. Observe whether there is abnormal movement of the machine tool, whether there is spark, noise, and abnormal noise, whether there is vibration, whether there is a burning smell. 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.
