Analyze the causes of deformation in mechanical parts processing:
The effect of internal forces causes changes in the machining accuracy of parts
When machining on a lathe, the centripetal force is usually used to clamp the parts tightly with the three 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 under force and reduce the effect of radial force on the inner diameter, it is necessary to make the clamping force greater than the mechanical cutting force. The clamping force increases and decreases with the increase of cutting force. This operation is necessary to ensure that mechanical parts are subjected to stable forces during the machining process. However, after the three or four jaw chuck is released, the machined mechanical parts will differ significantly from the original ones, some appearing polygonal and some elliptical, resulting in significant deviations.
Deformation problems are prone to occur after heat treatment processing
For thin mechanical parts, due to their large length and diameter, they are prone to bending of the straw cap after heat treatment. On the one hand, there will be a phenomenon of bulging in the middle, increasing the plane deviation. On the other hand, due to various external factors, the parts will bend. The occurrence of these deformation problems is not only due to the change in internal stress of the parts after heat treatment, but also due to the lack of solid professional knowledge of the operators, who are not very familiar with the structural stability of the parts, thereby increasing the probability of part deformation.
Elastic deformation caused by external forces
There are several main reasons for elastic deformation of parts in mechanical processing. One reason is that if the internal structure of some parts contains thin sheets, there will be higher requirements for the operation method. Otherwise, when the operator positions and clamps the parts, they cannot correspond with the design on the drawing, which can easily lead to elastic deformation. The second is the unevenness of the lathe and fixture, which leads to uneven force distribution on both sides of the parts during fixation, resulting in the deformation of the parts due to the translation of the less stressed side during cutting under the action of force. The third issue is the unreasonable positioning of the parts during the machining process, which reduces the rigidity and strength of the parts. 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 indicates the influence of external forces on the machining quality of mechanical parts.
Improvement measures for machining deformation of mechanical parts
In actual part processing, there are many factors that can cause part deformation. In order to fundamentally solve these deformation problems, operators need to carefully explore these factors in practical work and develop improvement measures based on the essence of the work.
1. Use specialized fixtures to reduce clamping deformation
In the process of machining mechanical parts, the requirements for precision are very strict. Choosing different specialized fixtures for different parts can prevent displacement during the machining process. In addition, before processing, the staff also needs to make corresponding preparations, comprehensively inspect the fixed parts, compare the drawings, and check whether the position of the mechanical parts is correct to reduce clamping deformation.
2. Trimming and processing
Parts are prone to deformation after heat treatment, which requires measures to ensure the safety performance of the parts. After the mechanical parts are processed and naturally deformed, professional tools should be used for repair. When repairing and processing processed parts, it is necessary to follow industry standards to ensure the quality of the parts and extend their service life. This method is most effective after part deformation. If the part deforms after heat treatment, it can be tempered after quenching. Because residual austenite will exist in the parts after quenching, these substances will be transformed into martensite at room temperature, and then the object will expand. When processing parts, every detail should be taken seriously, which can reduce the probability of part deformation, grasp the design concept on the drawing, and according to production requirements, make the produced products meet standards, improve economic benefits and work efficiency, thereby ensuring the quality of mechanical part processing.
3. Improve the quality of raw materials
In the specific operation process of various equipment, improving the quality of the rough embryo is a guarantee to prevent part deformation, so that the processed parts meet the specific standard requirements of the parts and provide assurance for the later use of the parts. Therefore, operators need to check the quality of different blanks and replace problematic blanks in a timely manner to avoid unnecessary problems. At the same time, operators need to select reliable blanks based on 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.
4. Increase part stiffness to prevent excessive deformation
In the processing of mechanical parts, the safety performance of the parts is influenced by many objective factors. Especially after heat treatment of parts, stress shrinkage can cause deformation of the parts. Therefore, in order to prevent deformation, technicians need to choose appropriate heat limiting treatment methods to change the stiffness of the parts. This requires combining the performance of the parts and applying appropriate heat limiting treatment measures to ensure safety and reliability. Even after heat treatment, there will be no significant deformation.
5 Measures to reduce clamping force
When processing parts with poor rigidity, some measures need to be taken to increase the rigidity of the parts, such as adding auxiliary support. Attention should also be paid to the contact area between the tightening point and the parts, and different clamping methods should be selected according to the different parts. For example, when processing thin-walled sleeve parts, elastic shaft devices can be used for clamping, and the tightening position should be selected as a part with strong rigidity. For long axis mechanical parts, the two end positioning method can be used. For parts with a very large diameter, it is necessary to use the method of clamping both ends together, and the method of "clamping one end and hanging one end" cannot be used. In addition, when processing cast iron parts, the design of fixtures needs to be based on 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 during the machining process of the parts.
6. Reduce cutting force
In cutting, it is important to closely consider the machining requirements and pay attention to the cutting angle in order to reduce cutting force. It is possible to increase the leading angle and main deviation angle of the tool as much as possible to make the blade sharp, and a reasonable tool is also crucial for the magnitude of turning force in turning. For example, in turning thin-walled parts, if the rake angle is too large, it will increase the wedge angle of the tool, accelerate wear speed, and reduce deformation and friction. The size of the rake angle can be selected according to different tools. If high-speed cutting tools are used, the optimal front angle is 6 ° to 30 °; If using hard alloy cutting tools, it is best to have a front angle of 5 ° to 20 °
