Analysis on the Key Points of CNC Machining Technology and CNC Machine Tool Maintenance
Abstract: This paper deeply explores the concept and characteristics of CNC machining, as well as the similarities and differences between it and the processing technology regulations of traditional machine tools. It mainly elaborates on the precautions after the completion of CNC machine tool processing, including aspects such as the cleaning and maintenance of machine tools, the inspection and replacement of oil wiper plates on guide rails, the management of lubricating oil and coolant, and the power-off sequence. Meanwhile, it also introduces in detail the principles of starting up and operating CNC machine tools, operation specifications, and key points of safety protection, aiming to provide comprehensive and systematic technical guidance for technicians and operators engaged in the field of CNC machining, so as to ensure the efficient operation and long service life of CNC machine tools.
I. Introduction
CNC machining occupies an extremely important position in the field of modern mechanical manufacturing. With the continuous development of the manufacturing industry, higher and higher requirements have been put forward for the precision, efficiency, and flexibility of parts processing. Thanks to its advantages such as digital control, high degree of automation, and high machining precision, CNC machining has become a key technology for solving the processing problems of complex parts. However, to fully exert the efficiency of CNC machine tools and extend their service life, it is necessary not only to deeply understand the CNC machining technology but also to strictly follow the specification requirements of CNC machine tools in aspects such as operation, maintenance, and upkeep.
II. Overview of CNC Machining
CNC machining is an advanced mechanical machining method that precisely controls the displacement of parts and cutting tools by using digital information on CNC machine tools. Compared with traditional machine tool machining, it has significant advantages. When facing machining tasks with variable part varieties, small batches, complex shapes, and high precision requirements, CNC machining demonstrates strong adaptability and processing capabilities. Traditional machine tool machining often requires frequent replacement of fixtures and adjustment of processing parameters, while CNC machining can continuously and automatically complete all turning processes under the control of programs through one-time clamping, greatly reducing auxiliary time and improving the stability of machining efficiency and machining precision.
Although the processing technology regulations of CNC machine tools and traditional machine tools are generally consistent in the overall framework, for example, steps such as part drawing analysis, process plan formulation, and tool selection are all required, the automation and precision characteristics of CNC machining in the specific implementation process make it have many unique features in process details and operation processes.
Although the processing technology regulations of CNC machine tools and traditional machine tools are generally consistent in the overall framework, for example, steps such as part drawing analysis, process plan formulation, and tool selection are all required, the automation and precision characteristics of CNC machining in the specific implementation process make it have many unique features in process details and operation processes.
III. Precautions after the Completion of CNC Machine Tool Processing
(I) Cleaning and Maintenance of Machine Tools
Chip Removal and Machine Tool Wiping
After machining is completed, a large number of chips will remain in the working area of the machine tool. If these chips are not cleaned up in time, they may enter the moving parts such as the guide rails and lead screws of the machine tool, exacerbating the wear of the parts and affecting the precision and motion performance of the machine tool. Therefore, operators should use special tools, such as brushes and iron hooks, to carefully remove the chips on the workbench, fixtures, cutting tools, and surrounding areas of the machine tool. During the process of chip removal, attention should be paid to avoiding chips scratching the protective coating on the surface of the machine tool.
After the chip removal is completed, it is necessary to wipe all parts of the machine tool, including the shell, control panel, and guide rails, with clean soft cloth to ensure that there is no oil stain, water stain, or chip residue on the surface of the machine tool, so that the machine tool and the surrounding environment remain clean. This not only helps to maintain the neat appearance of the machine tool but also prevents dust and impurities from accumulating on the surface of the machine tool and then entering the electrical system and mechanical transmission parts inside the machine tool, reducing the probability of failure occurrence.
After machining is completed, a large number of chips will remain in the working area of the machine tool. If these chips are not cleaned up in time, they may enter the moving parts such as the guide rails and lead screws of the machine tool, exacerbating the wear of the parts and affecting the precision and motion performance of the machine tool. Therefore, operators should use special tools, such as brushes and iron hooks, to carefully remove the chips on the workbench, fixtures, cutting tools, and surrounding areas of the machine tool. During the process of chip removal, attention should be paid to avoiding chips scratching the protective coating on the surface of the machine tool.
After the chip removal is completed, it is necessary to wipe all parts of the machine tool, including the shell, control panel, and guide rails, with clean soft cloth to ensure that there is no oil stain, water stain, or chip residue on the surface of the machine tool, so that the machine tool and the surrounding environment remain clean. This not only helps to maintain the neat appearance of the machine tool but also prevents dust and impurities from accumulating on the surface of the machine tool and then entering the electrical system and mechanical transmission parts inside the machine tool, reducing the probability of failure occurrence.
(II) Inspection and Replacement of Oil Wiper Plates on Guide Rails
Importance of Oil Wiper Plates and Key Points for Inspection and Replacement
The oil wiper plates on the guide rails of CNC machine tools play an important role in providing lubrication and cleaning for the guide rails. During the machining process, the oil wiper plates will continuously rub against the guide rails and are prone to wear over time. Once the oil wiper plates are severely worn, they will not be able to effectively and evenly apply lubricating oil to the guide rails, resulting in poor lubrication of the guide rails, increased friction, and further accelerating the wear of the guide rails, affecting the positioning precision and motion smoothness of the machine tool.
Therefore, operators should pay attention to checking the wear condition of the oil wiper plates on the guide rails after each machining is completed. When checking, it is possible to observe whether there are obvious signs of damage such as scratches, cracks, or deformations on the surface of the oil wiper plates, and at the same time, check whether the contact between the oil wiper plates and the guide rails is tight and uniform. If slight wear of the oil wiper plates is found, appropriate adjustments or repairs can be made; if the wear is severe, new oil wiper plates must be replaced in time to ensure that the guide rails are always in a good lubricated and working state.
The oil wiper plates on the guide rails of CNC machine tools play an important role in providing lubrication and cleaning for the guide rails. During the machining process, the oil wiper plates will continuously rub against the guide rails and are prone to wear over time. Once the oil wiper plates are severely worn, they will not be able to effectively and evenly apply lubricating oil to the guide rails, resulting in poor lubrication of the guide rails, increased friction, and further accelerating the wear of the guide rails, affecting the positioning precision and motion smoothness of the machine tool.
Therefore, operators should pay attention to checking the wear condition of the oil wiper plates on the guide rails after each machining is completed. When checking, it is possible to observe whether there are obvious signs of damage such as scratches, cracks, or deformations on the surface of the oil wiper plates, and at the same time, check whether the contact between the oil wiper plates and the guide rails is tight and uniform. If slight wear of the oil wiper plates is found, appropriate adjustments or repairs can be made; if the wear is severe, new oil wiper plates must be replaced in time to ensure that the guide rails are always in a good lubricated and working state.
(III) Management of Lubricating Oil and Coolant
Monitoring and Treatment of the States of Lubricating Oil and Coolant
Lubricating oil and coolant are indispensable media for the normal operation of CNC machine tools. Lubricating oil is mainly used for lubricating the moving parts such as the guide rails, lead screws, and spindles of the machine tool to reduce friction and wear and ensure the flexible movement and high-precision operation of the parts. Coolant is used for cooling and chip removal during the machining process to prevent the cutting tools and workpieces from being damaged due to high temperature, and at the same time, it can wash away the chips generated during machining and keep the machining area clean.
After machining is completed, operators need to check the states of the lubricating oil and coolant. For lubricating oil, it is necessary to check whether the oil level is within the normal range. If the oil level is too low, the corresponding specification of lubricating oil should be added in time. Meanwhile, check whether the color, transparency, and viscosity of the lubricating oil are normal. If it is found that the color of the lubricating oil turns black, becomes turbid, or the viscosity changes significantly, it may mean that the lubricating oil has deteriorated and needs to be replaced in time to ensure the lubrication effect.
For coolant, it is necessary to check its liquid level, concentration, and cleanliness. When the liquid level is insufficient, the coolant should be replenished; if the concentration is inappropriate, it will affect the cooling effect and anti-rust performance, and adjustments should be made according to the actual situation; if there are too many chip impurities in the coolant, its cooling and lubricating performance will be reduced, and even the cooling pipes may be blocked. At this time, the coolant needs to be filtered or replaced to ensure that the coolant can circulate normally and provide a good cooling environment for the machining of the machine tool.
Lubricating oil and coolant are indispensable media for the normal operation of CNC machine tools. Lubricating oil is mainly used for lubricating the moving parts such as the guide rails, lead screws, and spindles of the machine tool to reduce friction and wear and ensure the flexible movement and high-precision operation of the parts. Coolant is used for cooling and chip removal during the machining process to prevent the cutting tools and workpieces from being damaged due to high temperature, and at the same time, it can wash away the chips generated during machining and keep the machining area clean.
After machining is completed, operators need to check the states of the lubricating oil and coolant. For lubricating oil, it is necessary to check whether the oil level is within the normal range. If the oil level is too low, the corresponding specification of lubricating oil should be added in time. Meanwhile, check whether the color, transparency, and viscosity of the lubricating oil are normal. If it is found that the color of the lubricating oil turns black, becomes turbid, or the viscosity changes significantly, it may mean that the lubricating oil has deteriorated and needs to be replaced in time to ensure the lubrication effect.
For coolant, it is necessary to check its liquid level, concentration, and cleanliness. When the liquid level is insufficient, the coolant should be replenished; if the concentration is inappropriate, it will affect the cooling effect and anti-rust performance, and adjustments should be made according to the actual situation; if there are too many chip impurities in the coolant, its cooling and lubricating performance will be reduced, and even the cooling pipes may be blocked. At this time, the coolant needs to be filtered or replaced to ensure that the coolant can circulate normally and provide a good cooling environment for the machining of the machine tool.
(IV) Power-off Sequence
Correct Power-off Process and Its Significance
The power-off sequence of CNC machine tools is of great significance for protecting the electrical system and data storage of the machine tools. After machining is completed, the power on the machine tool operation panel and the main power should be turned off in sequence. Turning off the power on the operation panel first allows the control system of the machine tool to systematically complete operations such as the storage of current data and system self-check, avoiding data loss or system failures caused by sudden power failure. For example, some CNC machine tools will update and store processing parameters, tool compensation data, etc. in real time during the machining process. If the main power is directly turned off, these unsaved data may be lost, affecting the subsequent machining precision and efficiency.
After turning off the power on the operation panel, turn off the main power to ensure the safe power-off of the entire electrical system of the machine tool and prevent electromagnetic shocks or other electrical failures caused by the sudden power-off of electrical components. The correct power-off sequence is one of the basic requirements for the maintenance of CNC machine tools and helps to extend the service life of the electrical system of the machine tool and ensure the stable operation of the machine tool.
The power-off sequence of CNC machine tools is of great significance for protecting the electrical system and data storage of the machine tools. After machining is completed, the power on the machine tool operation panel and the main power should be turned off in sequence. Turning off the power on the operation panel first allows the control system of the machine tool to systematically complete operations such as the storage of current data and system self-check, avoiding data loss or system failures caused by sudden power failure. For example, some CNC machine tools will update and store processing parameters, tool compensation data, etc. in real time during the machining process. If the main power is directly turned off, these unsaved data may be lost, affecting the subsequent machining precision and efficiency.
After turning off the power on the operation panel, turn off the main power to ensure the safe power-off of the entire electrical system of the machine tool and prevent electromagnetic shocks or other electrical failures caused by the sudden power-off of electrical components. The correct power-off sequence is one of the basic requirements for the maintenance of CNC machine tools and helps to extend the service life of the electrical system of the machine tool and ensure the stable operation of the machine tool.
IV. Principles of Starting Up and Operating CNC Machine Tools
(I) Starting-up Principle
Starting-up Sequence of Returning to Zero, Manual Operation, Inching Operation, and Automatic Operation and Its Principle
When starting up a CNC machine tool, the principle of returning to zero (except for special requirements), manual operation, inching operation, and automatic operation should be followed. The operation of returning to zero is to make the coordinate axes of the machine tool return to the origin position of the machine tool coordinate system, which is the basis for establishing the machine tool coordinate system. Through the operation of returning to zero, the machine tool can determine the starting positions of each coordinate axis, providing a benchmark for subsequent precise motion control. If the operation of returning to zero is not carried out, the machine tool may have motion deviations due to not knowing the current position, affecting the machining precision and even leading to collision accidents.
After the operation of returning to zero is completed, manual operation is carried out. Manual operation allows operators to individually control each coordinate axis of the machine tool to check whether the motion of the machine tool is normal, such as whether the moving direction of the coordinate axis is correct and whether the moving speed is stable. This step helps to discover possible mechanical or electrical problems of the machine tool before formal machining and make timely adjustments and repairs.
The inching operation is to move the coordinate axes at a lower speed and for a short distance on the basis of manual operation, further checking the motion precision and sensitivity of the machine tool. Through the inching operation, it is possible to observe in more detail the response situation of the machine tool during low-speed motion, such as whether the transmission of the lead screw is smooth and whether the friction of the guide rail is uniform.
Finally, automatic operation is carried out, that is, the machining program is input into the control system of the machine tool, and the machine tool automatically completes the machining of parts according to the program. Only after confirming that all the performance of the machine tool is normal through the previous operations of returning to zero, manual operation, and inching operation can automatic machining be carried out to ensure the safety and precision of the machining process.
When starting up a CNC machine tool, the principle of returning to zero (except for special requirements), manual operation, inching operation, and automatic operation should be followed. The operation of returning to zero is to make the coordinate axes of the machine tool return to the origin position of the machine tool coordinate system, which is the basis for establishing the machine tool coordinate system. Through the operation of returning to zero, the machine tool can determine the starting positions of each coordinate axis, providing a benchmark for subsequent precise motion control. If the operation of returning to zero is not carried out, the machine tool may have motion deviations due to not knowing the current position, affecting the machining precision and even leading to collision accidents.
After the operation of returning to zero is completed, manual operation is carried out. Manual operation allows operators to individually control each coordinate axis of the machine tool to check whether the motion of the machine tool is normal, such as whether the moving direction of the coordinate axis is correct and whether the moving speed is stable. This step helps to discover possible mechanical or electrical problems of the machine tool before formal machining and make timely adjustments and repairs.
The inching operation is to move the coordinate axes at a lower speed and for a short distance on the basis of manual operation, further checking the motion precision and sensitivity of the machine tool. Through the inching operation, it is possible to observe in more detail the response situation of the machine tool during low-speed motion, such as whether the transmission of the lead screw is smooth and whether the friction of the guide rail is uniform.
Finally, automatic operation is carried out, that is, the machining program is input into the control system of the machine tool, and the machine tool automatically completes the machining of parts according to the program. Only after confirming that all the performance of the machine tool is normal through the previous operations of returning to zero, manual operation, and inching operation can automatic machining be carried out to ensure the safety and precision of the machining process.
(II) Operating Principle
Operating Sequence of Low Speed, Medium Speed, and High Speed and Its Necessity
The operation of the machine tool should follow the principle of low speed, medium speed, and then high speed, and the running time at low speed and medium speed shall not be less than 2 – 3 minutes. After starting up, each part of the machine tool needs a preheating process, especially the key moving parts such as the spindle, lead screw, and guide rail. Low-speed operation can make these parts gradually heat up, so that the lubricating oil is evenly distributed to each friction surface, reducing friction and wear during cold start. Meanwhile, low-speed operation also helps to check the operation stability of the machine tool in the low-speed state, such as whether there are abnormal vibrations and noises.
After a period of low-speed operation, it is switched to medium-speed operation. Medium-speed operation can further increase the temperature of the parts to make them reach a more suitable working state, and at the same time, it can also test the performance of the machine tool at medium speed, such as the rotational speed stability of the spindle and the response speed of the feed system. During the low-speed and medium-speed operation processes, if any abnormal situation of the machine tool is found, it can be stopped in time for inspection and repair to avoid serious failures during high-speed operation.
When it is determined that there is no abnormal situation during the low-speed and medium-speed operation of the machine tool, the speed can be gradually increased to high speed. High-speed operation is the key for CNC machine tools to exert their high-efficiency machining capabilities, but it can only be carried out after the machine tool has been fully preheated and its performance has been tested, so as to ensure the precision, stability, and reliability of the machine tool during high-speed operation, extend the service life of the machine tool, and at the same time ensure the quality of the machined parts and the machining efficiency.
The operation of the machine tool should follow the principle of low speed, medium speed, and then high speed, and the running time at low speed and medium speed shall not be less than 2 – 3 minutes. After starting up, each part of the machine tool needs a preheating process, especially the key moving parts such as the spindle, lead screw, and guide rail. Low-speed operation can make these parts gradually heat up, so that the lubricating oil is evenly distributed to each friction surface, reducing friction and wear during cold start. Meanwhile, low-speed operation also helps to check the operation stability of the machine tool in the low-speed state, such as whether there are abnormal vibrations and noises.
After a period of low-speed operation, it is switched to medium-speed operation. Medium-speed operation can further increase the temperature of the parts to make them reach a more suitable working state, and at the same time, it can also test the performance of the machine tool at medium speed, such as the rotational speed stability of the spindle and the response speed of the feed system. During the low-speed and medium-speed operation processes, if any abnormal situation of the machine tool is found, it can be stopped in time for inspection and repair to avoid serious failures during high-speed operation.
When it is determined that there is no abnormal situation during the low-speed and medium-speed operation of the machine tool, the speed can be gradually increased to high speed. High-speed operation is the key for CNC machine tools to exert their high-efficiency machining capabilities, but it can only be carried out after the machine tool has been fully preheated and its performance has been tested, so as to ensure the precision, stability, and reliability of the machine tool during high-speed operation, extend the service life of the machine tool, and at the same time ensure the quality of the machined parts and the machining efficiency.
V. Operation Specifications and Safety Protection of CNC Machine Tools
(I) Operation Specifications
Operation Specifications for Workpieces and Cutting Tools
It is strictly prohibited to knock, correct, or modify workpieces on chucks or between centers. Performing such operations on chucks and centers is likely to damage the positioning precision of the machine tool, damage the surfaces of chucks and centers, and affect their clamping precision and reliability. When clamping workpieces, it is necessary to confirm that the workpieces and cutting tools are clamped tightly before proceeding to the next step. Unclamped workpieces or cutting tools may become loose, displaced, or even fly out during the machining process, which will not only lead to the scrapping of machined parts but also pose a serious threat to the personal safety of operators.
Operators must stop the machine when replacing cutting tools, workpieces, adjusting workpieces, or leaving the machine tool during work. Performing these operations during the operation of the machine tool may cause accidents due to accidental contact with the moving parts of the machine tool, and may also lead to damage to cutting tools or workpieces. The operation of stopping the machine can ensure that operators can replace and adjust cutting tools and workpieces in a safe state and ensure the stability of the machine tool and the machining process.
It is strictly prohibited to knock, correct, or modify workpieces on chucks or between centers. Performing such operations on chucks and centers is likely to damage the positioning precision of the machine tool, damage the surfaces of chucks and centers, and affect their clamping precision and reliability. When clamping workpieces, it is necessary to confirm that the workpieces and cutting tools are clamped tightly before proceeding to the next step. Unclamped workpieces or cutting tools may become loose, displaced, or even fly out during the machining process, which will not only lead to the scrapping of machined parts but also pose a serious threat to the personal safety of operators.
Operators must stop the machine when replacing cutting tools, workpieces, adjusting workpieces, or leaving the machine tool during work. Performing these operations during the operation of the machine tool may cause accidents due to accidental contact with the moving parts of the machine tool, and may also lead to damage to cutting tools or workpieces. The operation of stopping the machine can ensure that operators can replace and adjust cutting tools and workpieces in a safe state and ensure the stability of the machine tool and the machining process.
(II) Safety Protection
Maintenance of Insurance and Safety Protection Devices
The insurance and safety protection devices on CNC machine tools are important facilities for ensuring the safe operation of the machine tools and the personal safety of operators, and operators are not allowed to disassemble or move them at will. These devices include overload protection devices, travel limit switches, protective doors, etc. The overload protection device can automatically cut off the power when the machine tool is overloaded to prevent the machine tool from being damaged due to overload; the travel limit switch can limit the motion range of the coordinate axes of the machine tool to avoid collision accidents caused by overtravel; the protective door can effectively prevent chips from splashing and coolant from leaking during the machining process and causing harm to operators.
If these insurance and safety protection devices are disassembled or moved at will, the safety performance of the machine tool will be greatly reduced, and various safety accidents are likely to occur. Therefore, operators should regularly check the integrity and effectiveness of these devices, such as checking the sealing performance of the protective door and the sensitivity of the travel limit switch, to ensure that they can play their normal roles during the operation of the machine tool.
The insurance and safety protection devices on CNC machine tools are important facilities for ensuring the safe operation of the machine tools and the personal safety of operators, and operators are not allowed to disassemble or move them at will. These devices include overload protection devices, travel limit switches, protective doors, etc. The overload protection device can automatically cut off the power when the machine tool is overloaded to prevent the machine tool from being damaged due to overload; the travel limit switch can limit the motion range of the coordinate axes of the machine tool to avoid collision accidents caused by overtravel; the protective door can effectively prevent chips from splashing and coolant from leaking during the machining process and causing harm to operators.
If these insurance and safety protection devices are disassembled or moved at will, the safety performance of the machine tool will be greatly reduced, and various safety accidents are likely to occur. Therefore, operators should regularly check the integrity and effectiveness of these devices, such as checking the sealing performance of the protective door and the sensitivity of the travel limit switch, to ensure that they can play their normal roles during the operation of the machine tool.
(III) Program Verification
Importance and Operation Methods of Program Verification
Before starting the machining of a CNC machine tool, it is necessary to use the program verification method to check whether the program used is similar to the part to be machined. After confirming that there is no error, the safety protection cover can be closed and the machine tool can be started to machine the part. Program verification is a key link to prevent machining accidents and part scrapping caused by program errors. After the program is input into the machine tool, through the program verification function, the machine tool can simulate the motion trajectory of the cutting tool without actual cutting, and check for grammatical errors in the program, whether the cutting tool path is reasonable, and whether the processing parameters are correct.
When performing program verification, operators should carefully observe the simulated motion trajectory of the cutting tool and compare it with the part drawing to ensure that the cutting tool path can accurately machine the required part shape and size. If problems are found in the program, they should be modified and debugged in time until the program verification is correct before formal machining can be carried out. Meanwhile, during the machining process, operators should also pay close attention to the operation state of the machine tool. Once an abnormal situation is found, the machine tool should be stopped immediately for inspection to prevent accidents.
Before starting the machining of a CNC machine tool, it is necessary to use the program verification method to check whether the program used is similar to the part to be machined. After confirming that there is no error, the safety protection cover can be closed and the machine tool can be started to machine the part. Program verification is a key link to prevent machining accidents and part scrapping caused by program errors. After the program is input into the machine tool, through the program verification function, the machine tool can simulate the motion trajectory of the cutting tool without actual cutting, and check for grammatical errors in the program, whether the cutting tool path is reasonable, and whether the processing parameters are correct.
When performing program verification, operators should carefully observe the simulated motion trajectory of the cutting tool and compare it with the part drawing to ensure that the cutting tool path can accurately machine the required part shape and size. If problems are found in the program, they should be modified and debugged in time until the program verification is correct before formal machining can be carried out. Meanwhile, during the machining process, operators should also pay close attention to the operation state of the machine tool. Once an abnormal situation is found, the machine tool should be stopped immediately for inspection to prevent accidents.
VI. Conclusion
As one of the core technologies in modern mechanical manufacturing, CNC machining directly relates to the development level of the manufacturing industry in terms of its machining precision, efficiency, and quality. The service life and performance stability of CNC machine tools not only depend on the quality of the machine tools themselves but also are closely related to the operation specifications, maintenance, and safety protection awareness of operators in the daily use process. By deeply understanding the characteristics of CNC machining technology and CNC machine tools and strictly following the precautions after machining, the starting-up and operating principles, operation specifications, and safety protection requirements, the failure occurrence rate of machine tools can be effectively reduced, the service life of machine tools can be extended, the machining efficiency and product quality can be improved, and greater economic benefits and market competitiveness can be created for enterprises. In the future development of the manufacturing industry, with the continuous innovation and progress of CNC technology, operators should constantly learn and master new knowledge and skills to adapt to the increasingly high requirements in the field of CNC machining and promote the development of CNC machining technology to a higher level.