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Causes of Common Machining Errors and Improvement Measures

September 30, 2022

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 part deformation in the process of part processing. Operators need to consider various factors and take corresponding measures to prevent deformation during processing, so that finished parts can be used normally. In order to achieve this goal, it is necessary to analyze the causes of deformation in part processing and find out reliable measures for part deformation, so as to lay a solid foundation for the realization of the strategic objectives of modern enterprises.

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1. Analyze the causes of deformation during machining of mechanical parts
1.1 The machining accuracy of parts is changed due to internal force
In the process of lathe machining, it is usually to use the centripetal force to clamp the parts with the three jaw or four jaw chuck of the lathe, and then process the mechanical parts. At the same time, in order to ensure that the parts are not loose when subjected to force and reduce the role of internal force, it is necessary to make the clamping force greater than the cutting force of the machine. The clamping force increases with the increase of cutting force, and decreases with the decrease. Such operation can make the mechanical parts stable in the process of processing. However, after the three jaw chuck or four jaw chuck is loosened, the machined mechanical parts will be far different from the original ones, some of which are polygonal, and some are elliptical, with large deviations.

1.2 Deformation is easy to occur after heat treatment
For mechanical parts of the thin type, due to their large length diameter, straw hats are prone to bend after heat treatment. On the one hand, there will be bulge in the middle, and the plane deviation will increase. On the other hand, due to various external factors, parts will be bent. These deformation problems are not only caused by changes in the internal stress of the parts after heat treatment, but also due to the lack of solid professional knowledge of the operators, who do not know much about the structural stability of the parts, thus increasing the probability of part deformation.

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1.3 Elastic deformation caused by external force
There are several main reasons for elastic deformation of parts in machining. First, if the internal structure of some parts contains flakes, there will be higher requirements for the operation method. Otherwise, when the operators locate and clamp the parts, they cannot correspond with the design of the drawings, which may easily lead to elastic deformation. Second, the unevenness of the lathe and fixture makes the force on both sides of the part uneven when fixing, resulting in the translation and deformation of the part on the side with less force during cutting. Third, the positioning of the parts in the processing process is unreasonable, which reduces the rigidity and strength of the parts. Fourthly, the existence of cutting force is also one of the causes of elastic deformation of parts. The elastic deformation caused by these different reasons shows the influence of external force on the machining quality of mechanical parts.

2 Improvement measures for machining deformation of mechanical parts
In the actual part processing, there are many factors that cause part deformation. In order to fundamentally solve these deformation problems, operators need to seriously explore these factors in actual work and formulate improvement measures in combination with the essence of work.

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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, select different special tooling, which can prevent the parts from displacement during processing. In addition, before processing, the staff also need to make corresponding preparations, comprehensively check the fixed parts, and check whether the position of the mechanical parts is correct according to the drawings, so as to reduce the clamping deformation.

2.2 Finishing
Parts are easy to deform after heat treatment, which requires measures to ensure the safety of parts. After the mechanical parts are processed and naturally deformed, professional tools shall be used for trimming. When finishing the processed parts, it is required to follow the industry standard requirements to ensure the quality of the parts and extend their service life. This method is most effective after part deformation. If the part is deformed after heat treatment, it can be tempered after quenching. Because there will be residual austenite in the part after quenching, these substances will be converted into martensite at room temperature, and then the object will expand. When processing parts, we should take every detail seriously, so that we can reduce the probability of part deformation, grasp the design concept on the drawings, make the products meet the standards according to the production requirements, improve economic efficiency and work efficiency, and ensure the quality of mechanical parts processing.

2.3 Improve blank quality
In the specific operation process of various equipment, improving the quality of the rough embryo is the guarantee to prevent part deformation, so that the processed parts can meet the specific standard requirements of the parts and provide guarantee for the use of the parts in the later stage. Therefore, the operator needs to check the quality of different blanks and replace the defective blanks in time to avoid unnecessary problems. At the same time, the operator needs to select reliable blanks according to the specific requirements of the equipment to ensure that the quality and safety of the processed parts meet the standard requirements, thus extending the service life of the parts.

2.4 Increase part stiffness to prevent excessive deformation
In the processing of mechanical parts, the safety performance of parts is affected by many objective factors. Especially after the heat treatment of the parts, due to the stress shrinkage phenomenon, the parts will be deformed. Therefore, in order to prevent the occurrence of deformation, technicians need to select appropriate heat limiting treatment methods to change the part stiffness. This requires the use of appropriate heat limiting treatment measures in combination with the performance of parts to ensure safety and reliability. Even after heat treatment, no obvious deformation will occur.

2.5 Measures to reduce clamping force
When machining parts with poor rigidity, some measures should be taken to increase the rigidity of the parts, such as adding auxiliary supports. Attention should also be paid to the contact area between the clamping point and the parts. Different clamping methods should be selected according to the different parts. For example, when machining thin-walled sleeve parts, elastic shaft devices can be selected for clamping. Attention should be paid to the clamping position should be the position with strong rigidity. For mechanical parts of long shaft type, both ends can be positioned. For parts with very large length and diameter, both ends shall be clamped together, instead of "one end clamped and one end suspended". In addition, when machining cast iron parts, the design of the fixture should 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 the quality problems caused by clamping deformation during the processing of parts.

2.6 Reducing cutting force
In the process of cutting, attention should be paid to the cutting angle in close combination with the processing requirements in order to reduce the cutting force. The rake angle and main deflection angle of the tool can be increased as much as possible to make the blade sharp, and a reasonable tool is also crucial to the turning force in turning. For example, in turning thin-walled parts, if the rake angle is too large, the wedge angle of the tool will become larger, the wear speed will be accelerated, and the deformation and friction will also be reduced. The rake angle can be selected according to different tools. If the high speed cutter is selected, the best rake angle is 6 °~30 °; If cemented carbide tools are used, it is better to have a front angle of 5 °~20 °.

3 Conclusion
There are many factors that cause the deformation of mechanical parts, and different measures should be taken to solve different causes. In actual operation, we should pay attention to every detail of mechanical processing, constantly improve the production process, and strive to minimize economic losses, so as to ensure the stable work of mechanical equipment, achieve the goal of high quality and efficiency of mechanical processing, and thus promote the mechanical processing industry to have a better development prospect and a broader market.