Machining performance is not only related to the interests of enterprises, but also related to safety. While bringing economic benefits to enterprises, it can also effectively reduce the probability of safety accidents. Therefore, it is particularly important to avoid the deformation when machining parts. Operators need to consider various factors and take corresponding measures to prevent deformation during processing, so that the finished parts can be used normally. In order to achieve this goal, it is necessary to analyze the causes of deformation in parts processing, and find reliable measures for the deformation of parts, in order to lay a solid foundation for the realization of the strategic goals of modern enterprises.
1 Analysis of the causes of deformation in the machining of mechanical parts
1.1 The internal force causes the machining accuracy of the parts to change
During lathe processing, the centripetal force is usually used to clamp the parts with the three-jaw or four-jaw chuck of the lathe, and then the mechanical parts are processed. At the same time, in order to ensure that the parts do not loosen when under force and reduce the effect of the internal radial force, the clamping force must be greater than the mechanical cutting force. The clamping force increases as the cutting force increases and decreases with it. Such an operation can make the mechanical parts stable during the machining process. However, after the three-jaw or four-jaw chuck is released, the machined parts will be very different from the original ones, some are polygonal, some are oval, and there is a big deviation.
1.2 Deformation is easy to occur after heat treatment
For sheet-like mechanical parts, due to their large long diameter, the straw hat is prone to bending after heat treatment. On the one hand, there will be a phenomenon of bulging in the middle, and the plane deviation will increase. On the other hand, due to the influence of various external factors, the parts will be bent. The occurrence of these deformation problems is not only due to the change in the internal stress of the parts after heat treatment, but also because the operator’s professional knowledge is not solid and the structural stability of the parts is not well understood, thus increasing the probability of deformation of the machining parts.
1.3 Elastic deformation caused by external force
There are several reasons for the elastic deformation of parts in machining. First, if the internal structure of some parts contains flakes, there will be higher requirements on the operation method. Otherwise, when the operator locates and clamps the parts, they cannot correspond with the design of the drawings, which will easily lead to elastic deformation. produce. The second is the unevenness of the lathe and the fixture, so that the force on both sides of the part is uneven when the part is fixed, resulting in the side with less force during cutting, which will translate and deform the part under the action of the force. The third is the unreasonable positioning of the parts during the processing, which reduces the rigidity of the parts. Fourth, the existence of cutting force is also one of the reasons for the elastic deformation of parts. The elastic deformation caused by these different reasons all illustrate the influence of external force on the machining quality of mechanical parts.
2 Improvement measures for machining deformation of mechanical parts
In actual parts processing, there are many factors that cause parts to deform. In order to fundamentally solve these deformation problems, operators need to carefully explore these factors in actual work, and combine the essence of the work to formulate improvement measures.
2.1 Use special clamps to reduce clamping deformation
In the process of machining mechanical parts, the requirements for refinement are very strict. For different parts, different special tooling is selected, which can make the parts less prone to displacement during the processing. In addition, before processing, the staff also needs to carry out corresponding preparations, comprehensively check the fixed parts, and check whether the position of the mechanical parts is correct against the drawings to reduce the deformation of the clamping.
2.2 Dressing
Parts are prone to deformation after heat treatment, which requires measures to ensure the safety performance of parts. After the mechanical parts are processed and deformed naturally, professional tools should be used for trimming. When trimming the processed parts, it is necessary to follow the industry standard requirements to ensure the quality of the parts and prolong their service life. This method is most effective when the part is deformed. If the part is deformed after heat treatment, it can be tempered after quenching. Because residual austenite is present in the part after quenching, these substances are transformed into martensite at room temperature, and then the object expands. When machining parts, we must take every detail seriously, so as to reduce the probability of deformation of the parts, grasp the design concept on the drawings, and make the produced products meet the standards according to the production requirements, improve economic benefits and work efficiency, so as to ensure the mechanical The quality of the part machining.
2.3 Improve blank quality
In the specific operation process of various equipment, improving the quality of the blank is the guarantee to prevent the deformation of the parts, so that the processed parts meet the specific standard requirements of the parts, and provide guarantee for the use of the later parts. Therefore, operators need to check the quality of different blanks, and replace the blanks with problems in time to avoid unnecessary problems. At the same time, the operator needs to select a reliable blank according to the specific requirements of the equipment to ensure that the quality and safety of the processed parts meet the standard requirements, thereby extending the service life of the parts.
2.4 Increase the rigidity of parts to prevent excessive deformation
In the machining of mechanical parts, the safety performance of the parts is affected by many objective factors. Especially after the parts are heat treated, the parts will be deformed due to the phenomenon of stress shrinkage. Therefore, in order to prevent the occurrence of deformation, technicians need to select an appropriate heat-limiting treatment method to change the stiffness of the parts. This requires the use of appropriate heat-limiting treatment measures in combination with the performance of the parts to ensure safe reliability. Even after heat treatment, no significant deformation occurs.
2.5 Measures to reduce the clamping force
When machining parts with poor rigidity, some measures need to be taken to increase the rigidity of the parts, such as adding auxiliary supports. Also pay attention to the contact area between the tightening point and the parts. According to the different parts, choose different clamping methods. For example, when processing thin-walled sleeve parts, you can use an elastic shaft device for clamping. Note that the tightening position should be Choose a more rigid part. For the mechanical parts of the long axis, the positioning method at both ends can be used. For parts with very large length and diameter, it is necessary to clamp both ends together, and the method of “clamping at one end and hanging at the other end” cannot be used. In addition, when machining cast iron parts, the design of the fixture needs to be based on the principle of increasing the rigidity of the cantilever part. A new type of hydraulic clamping tool can also be used to effectively prevent quality problems caused by clamping deformation of parts during processing.
2.6 Reduce cutting force
In the cutting process, it is necessary to closely combine the processing requirements and pay attention to the cutting angle in order to reduce the cutting force. The rake angle and main declination angle of the tool can be increased as much as possible to make the blade sharp, and a reasonable tool is also critical to the amount of turning force in turning. For example, in the turning of thin-walled parts, if the rake angle is too large, the wedge angle of the tool will become larger, the wear rate will be accelerated, and the deformation and friction will be reduced. The size of the rake angle can be selected according to different tools. If a high-speed tool is used, the best rake angle is 6° to 30°; if a carbide tool is used, the best rake angle is 5° to 20°.
keywords: CNC machining stainless steel parts, aluminum parts, brass parts, titanium parts, cnc machining metal turning
