At present, many domestic operators who are just engaged in CNC machine tools, some operators are very familiar with machining, but the programming of CNC machine tools is relatively unfamiliar; some are just graduated students, they have knowledge of machining, CNC machining and programming. The theory is familiar, but lacks the actual machining experience; there are also many operators who have never been exposed to machining and programming. Then they have to learn CNC machine operation, the difficulty is very huge.
For those of the beginner CNC machine tools, it is very important to master certain CNC machine tool operation skills. On the one hand, they can avoid machine collision accidents, resulting in machine damage; second, they can quickly improve the operator's CNC machine tool operation skills in a short period of time, competent for their jobs. In particular, this paper introduces the theoretical knowledge of the operation skills of some CNC machine tools for these operators who are just in contact with CNC machine tools. It is hoped that there will be some reference significance for the operators of CNC machine tools just engaged.
First of all, the operator needs to have a comprehensive understanding of the operating CNC machine tools.
Understand the mechanical structure of the machine tool: to understand the mechanical structure of the machine tool; to master the shafting distribution of the machine tool; to grasp the positive and negative direction of each CNC axis of the machine tool; to master the functions and use of the various parts of the machine tool, such as simple Pneumatic system principle and function, simple hydraulic system working principle and function; in addition, it is necessary to master the working principle and function of each auxiliary unit of the machine tool, such as the work of the tool magazine, cooling unit, voltage regulator, electric cabinet cooler and so on. Principle, function and method of use, as well as the working principle, function and usage of each safety door lock of the machine tool.
Firmly grasp the function of each operation button of the machine: know how to execute the program; how to check the workpiece processing status after suspending the program, resume the execution after restarting the pause state, how to stop the program; how to change the program before executing the program, and so on.
Understand what kind of operating system your machine tool is operating; simply understand the control principle and working method of the CNC system; what working language the system uses, the software used for machine tool processing and the language used. If the operator does not understand the language or does not understand the professional vocabulary of the language, then professional training is required. When training, you need to take notes carefully. Every word in the machine software software means what Chinese meaning is. If you master the back, you can use the machine correctly for your future work.
In addition, the operator also needs to learn the general operation alarm statement during training, know what Chinese means, how to solve the problem, how to eliminate the error alarm. In addition, for the operator, if there is energy and ability to allow, you can learn the language, then it will be very helpful to improve the operation skills of the machine.
Secondly, it is necessary to master the manual or automatic operation of controlling the CNC machine tool, and master the movement of each CNC axis that controls the machine tool.
The operator must reach the realm of perfection, so that it can be retracted under any circumstances; in the event of a collision or failure, the operator can handle the problem correctly and in a timely manner, and the operator will form a conditioned reflex. Decisively take the means of braking.
In addition, the operator should be very familiar with the machining program of the CNC machine tool; what kind of process and operation, what kind of action the machine tool should have, must be very familiar. When the machine executes the program, you can know at the first time whether the machine action is correct and whether braking action is required. In addition, each beginner operator has more or less fear during the initial operation of the machine tool, fearing that the machine will hit the knife and collide. Then only the operator can master the operation of the CNC machine tool, can overcome the similar fear, in order to learn to master the higher CNC machine tool operation skills.
Third, it is necessary to be proficient in program editing, parameter compensation for each process, and compensation for the diameter and length of the tool or grinding wheel.
First, you will be trained to master the programming language, programming method and compensation method of each CNC machine tool. Most advanced CNC machines are now equipped with PC workstations for programming or simulation. Then beginners can perform software editing and machine cutting simulation learning on the workstation.
In the process of learning and programming, do not only pay attention to the simulation results, but more importantly, it is necessary to learn the process of simulation machining. It is necessary to understand what kind of tool or grinding wheel is needed for the machining of the workpiece, and the machining axis of the machine tool has completed the cutting process; When performing a specific process, the position and direction of the movement of the relevant components in the machine tool; pay attention to the direction of movement and the direction of the cutting of each axis during the machining, including how to enter the knife, how to retract the knife, pay attention to the work in the machine tool processing The fast forward speed and displacement of the step, the speed and displacement of the work in each step. In the processing through the simulation software, note that all parameters must be correctly input during the simulation process. Do not arbitrarily input the sloppy things because of the simulation, so that the result of the simulation processing may be incorrect; or the collision accident caused by actual processing in the future, or Parts are scrapped. If the simulation software has the function of anti-collision test, then use this function to check the correctness of the programming.
In addition, the operator needs special attention: the simulation processing is only a theoretical result, does not mean that the machine will not collide during the actual cutting process, nor does it mean that a qualified product can be processed. The purpose of simulation is to save programming time, improve the actual utilization of the machine tool, and reduce the debugging time when machining the workpiece. It does not represent the actual part processing. Completing the perfect workpiece machining is inseparable from the wisdom and sweat of CNC machine operators.
Point 4: The processing skills in the actual machining process, carefully prepare the work, first read the drawings, confirm the position of the workpiece to be machined, confirm the precision tolerance of the workpiece part, and then edit the machining program. To prepare the workpieces and tools or grinding wheels needed for machining, prepare the testing instruments required during the machining process, and prepare the auxiliary tools and fixtures required during the machining process.
When machining the first workpiece, the machine tool should be tested in a single step. When the machine program calls a new tool or grinding wheel, it should first perform the tool setting to check whether the program action is correct.
When the workpiece is processed, try to take the clamping once to complete the workpiece processing; if it is necessary to perform measurement or other reasons, the secondary clamping of the workpiece is required, then the positioning of the second clamping and the first clamping and the processing reference must be unified. . If the automatic positioning device of the machine tool is adopted, it is necessary to maintain the measurement speed consistency of the automatic measuring system. When detecting the machining accuracy of the workpiece, it is best to do it on the machine tool, which can reduce the positioning error of the secondary clamping. In addition, when the precision of the dimensional tolerance of the machine tool is high in some parts of the workpiece, the operator needs to perform the precision inspection after each machining is completed, and then the next position of the workpiece is processed after the inspection is passed; The shape of a certain part is processed by two or more directions, then the machining of each direction will affect the position or shape tolerance of the shape of the part, so the machining should first process the one that has less influence on the accuracy of the workpiece. Direction, and then the direction of the workpiece tolerance is higher, and finally the machining is repeated, and finally the required accuracy is approached. If the workpiece cannot be measured on the machine using a standard measuring instrument, and the workpiece cannot be removed from the machine for measurement, otherwise the machining accuracy of the workpiece is affected, then special calipers, plug gauges, gauges, etc. can be used. Testing, if the machine's own software has a measurement function, the machine itself can be used to measure the workpiece. After the entire workpiece has been machined, the workpiece is fully tested.
For the processing of batches of workpieces. When the initial program debugging is completed, then the machining program needs to be optimized. The basic principles of optimization are as follows: guarantee the premise of processing quality, optimize cutting parameters, such as work speed, tool or grinding wheel speed, lateral feed, machining depth, etc.; optimize machining steps, optimize machining benchmarks, improve machining efficiency, use high Life tool or grinding wheel, reduce the number of tool changes or the number of grinding wheel corrections; establish a mathematical model of a reasonable machining program, edit effective and reliable procedures, reasonably set the margin and number of rough machining and use appropriate forming tools or grinding wheels for efficiency To ensure that the processing quality has a more significant effect.
In order to ensure the processing quality of the workpiece to be processed, the following aspects should be paid attention to: the machine should be heated for a period of time during the machining, the heat balance of the machine axes of the machine during the working period should be maintained, and the temperature of the workpiece to be processed during the machining process should be kept as stable as possible and kept as much as possible. Cooling and heat balance of the working head, machine tool spindle, lead Screw guide, grating scale, tool chuck or grinding wheel post. If the machine uses cooling oil and coolant, keep its temperature constant. The temperature of the coolant is one of the important factors affecting the accuracy of the workpiece processing. The cooling system of the machine tool ensures the constant temperature of the coolant.
The general factory needs to be shut down at night, and the machine needs to be turned on the next day, so the hot machine is required before the machine is working every day. In order to improve the utilization of the machine tool, there are two existing methods for machine tool processing. First, the original program is slightly modified after starting up, and a compensation amount away from the workpiece is made in all the processing steps. Then, during the machining process, the machine tool changes the correction value according to the measurement result during the machining of the machine tool. When the machine tool is in thermal equilibrium state, the correction is made. The value does not need to be changed. Another method is to process the part with a large tolerance of the workpiece first after the start-up, and then wait for the machine to reach the thermal equilibrium after a period of time, and then process the workpiece with certain tolerance requirements; or use the machine first. Roughing is performed, and after the machine tool reaches thermal equilibrium, the workpiece is finished.
For a workpiece with multiple references, there are multiple sizes with higher precision requirements. Then, there should be a reference on the workpiece to define only one or two dimensions, but the position accuracy requires a higher position, and for parts with multiple dimensions of the same reference, the part with the highest precision should be processed first, and then the machining accuracy is higher. Low position. Because the workpiece is prone to waste when the machine tool is machining high-precision parts, the rest of the workpiece can be processed, which saves processing costs.
In short, the basic principle of processing: first roughing, removing the excess material of the workpiece, and then finishing; avoiding the occurrence of vibration during processing; avoiding thermal denaturation during workpiece processing. There are many reasons for the vibration. It may be that the load is too large, it may be the resonance of the machine tool and the workpiece, or it may be due to insufficient rigidity of the machine tool, or it may be caused by the passivation of the tool or the grinding wheel. We can reduce the vibration by reducing the infeed and the machining depth, checking whether the workpiece is clamped securely, increasing the speed of the tool or lowering the speed to reduce the resonance, and checking if it is necessary to replace the new tool.
For beginners who operate CNC machine tools, collisions often occur. I often hear people say that if you don't touch the machine tool, you will not learn the machine tool. This is a very wrong and harmful understanding. Machine tool collisions are very damaging to the accuracy of the machine tool and have different effects on different types of machine tools. Generally speaking, it has a great influence on a machine tool with a weak rigidity. For a machine tool with a rigid gantry structure, the impact is less under the same impact force. If the machine tool is a cantilever type structure, and the machine tool spindle is a machine tool structure mounted on a rotary axis, once the machine tool collides, the accuracy of the machine tool is fatal. Therefore, for high-precision CNC machine tools, collisions must be eliminated. Collision is completely preventable and avoidable as long as the operator is careful and has a certain anti-collision method. The following points may be helpful for the prevention of collisions by CNC machine tool beginners.
The main reasons for the collision occur: one is the wrong input of the diameter and length of the tool or the grinding wheel; 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 workpiece coordinate system of the machine tool. The setting is incorrect, or the machine zero is reset during machining and changes occur. Most machine tool collisions occur during the rapid movement of the machine tool. At this time, the collision is also the most harmful and should be avoided. Therefore, the operator should pay special attention to the machine tool in the initial stage of the execution of the program and when the machine is changing the tool or the grinding wheel. Once the program is edited incorrectly, the diameter and length of the tool or the grinding wheel are input incorrectly, then the collision is easy. At the end of the program, if the retracting action of each CNC axis is in the wrong order, collision may occur. In order to avoid the above collision, when using the tool and the grinding wheel for the first time, the tool must be carefully performed, and the problem cannot be underestimated. In order to avoid collision, the operator should fully function the five functions when operating the machine tool, observe whether the machine tool has abnormal movements, whether there is spark, whether there is noise or abnormal noise, whether there is vibration or not. If the abnormal condition is found, the program should be stopped immediately, and the machine can continue to work after the standby bed problem is solved. At the same time, before the operation, the operator should accept the safety training of the machine tool operation. Each type of machine tool should have safety operation rules. The operator should be trained in the operation and safety of the system. Only after the training certificate is issued can the machine work. Before working, you should know the location of the fire extinguisher, and the operator should master the method of the fire extinguisher, the position of the air pressure switch of the machine tool, the position of the switch of the input power of the machine tool, and the position of the hydraulic workstation. The grinding machine for cooling oil should place the fire extinguisher within three meters of the machine.
In short, mastering the operation skills of CNC machine tools is a gradual process that cannot be achieved overnight. It is based on mastering the basic operations of machine tools, basic machining knowledge and basic programming knowledge. CNC machine tool operation skills are not static. It is an organic combination that requires the operator's ingredients to exert imagination and hands-on ability, and is an innovative labor.
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