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Influence of machining process on machining accuracy of parts

Release time:Apr 30, 2019 Visits:

Key words: machining process; parts; machining accuracy; influence

In real life, the machinery used in all walks of life is composed of different parts. Whether the accuracy of these parts meets the requirements will directly affect the performance of the mechanical equipment. Therefore, with the improvement of the performance requirements of mechanical equipment, people have put forward higher requirements on the machining accuracy of parts. The machining process has a close relationship with the machining accuracy of the parts. Therefore, it is necessary to analyze the influence of the machining process on the machining accuracy of the parts, so as to better promote the development of the machining manufacturing industry.


A machining process and precision parts


1.1 Mechanical Processing Overview


The so-called machining process is actually a method of making blanks into mechanical parts and workpieces by using relevant process technology. It is a machining process that matches the blanks with the parts. In the process of processing, it is necessary to make the blank grinding and the processing of the parts to meet certain precision requirements. In general, it is necessary to finish the roughing of the part before finishing the part. Among them, roughing is the general grinding of blanks and parts, and it is necessary to make the processed blanks and parts close to the processing requirements. Finishing requires precise calculations to achieve maximum fit between the blank and the part.


1.2 Relationship between processing and processing precision machine parts


After the machining is completed, the corresponding inspection work needs to be carried out in order to eliminate the parts that do not meet the specified error range. Whether the machining process is rigorous will directly affect whether the machining accuracy of the parts can meet the processing requirements. Therefore, the machining process is actually a procedure for transforming the blank into a qualified part, and has strict requirements on the machining accuracy of the part. In the whole process of processing, the strict implementation of the machining process needs to be carried out in accordance with the relevant normative standards, so as to avoid the inaccuracy of the machining accuracy of the parts caused by external factors. At present, the machining process is more diverse, but the precision of part processing is also increasing. The improvement of the machining accuracy of the parts can also reflect the precision of the machining process [1]. Therefore, it is also necessary to understand the influence of the machining process on the machining accuracy of the parts, and thus seek ways to carry out the refinement and improvement of the machining process, and then the machining accuracy of the parts is effectively improved.


2 Influence of machining process on machining accuracy of parts


2.1 The effect of CNC programming on the machining accuracy of parts

In the process of machining parts using a machining process, it is necessary to control the machine tool through numerical control programming. CNC technology always regards high precision as the goal pursued, so the numerical control process will have an important impact on the machining accuracy of parts. First, the choice of programming origin is required at the beginning of NC programming. The ability to properly select the origin will directly affect the machining accuracy of the part. Because the selection of the programming origin is properly performed, machining errors due to dimensional tolerance conversion can be avoided. Secondly, the data needs to be processed during programming, and whether the data can be processed reasonably will affect the processing accuracy of the contour trace of the part. In this step, you also need to do an unknown programming node for calculation. Moreover, CNC programming also needs to choose a reasonable processing route. The selection of the machining route of the parts will directly affect the machining efficiency and accuracy of the parts. In addition, in the process of machining parts, if the selected interpolation method is improper, it will affect the machining accuracy of the parts. At the same time, no matter which interpolation method is used, the error will be accumulated [2]. After the error has accumulated to a certain extent, the machine tool will have positioning errors and movements, which will affect the machining accuracy of the parts. Therefore, it is necessary to perform interpolation operations in the NC programming process in order to better control the machining accuracy of the parts.


2.2 The influence of geometric accuracy on the machining accuracy of parts

In the process of part processing, the processes of cutting and grinding need to be done manually, so it is basically difficult to achieve the same. In this case, geometrical parameter errors will occur in the machining of the part, which will affect the machining accuracy of the part. On the one hand, the use of tools is required during the machining process, so the accuracy of the tools will have an important impact on the machining accuracy of the parts. When cutting with a tool, the tool will be subject to wear due to the frictional action of the blade, the blade and the workpiece. After a certain degree of wear, the friction value of the surface of the workpiece increases, causing the tool to vibrate during the cutting process and eventually causing a change in the shape of the cutting. In order to solve this problem, the installation accuracy and wear resistance of the tool are also improved. At the same time, it is necessary to strengthen the tool maintenance in daily work and use the compensation device for wear compensation. On the other hand, the continuous operation of machined machine tools will cause the spindle to have a rotation error. In the case where the main shaft deviates from the standard central axis, there will be some error in the machining of the parts [3]. Because the machine tool spindle rotation force can control the relative position of the parts processing, the spindle deviation will directly affect the surface smoothness of the part. In order to solve this problem, it is necessary to strictly carry out the assembly of the machine tool spindle and strengthen the maintenance in daily work.


2.3 Influence of force deformation on machining accuracy of parts

In the process of machining, it involves the movement of the four components of the machine tool, workpiece, tool and fixture, so the system will withstand various forces such as clamp clamping force, workpiece gravity and tool cutting force. Under the combined effect of force, fatigue deformation will occur inside the system, thus forming a certain processing error. For the time being, these forces can be divided into two types, namely, processing external forces and residual stresses.

Under the action of different external forces, the machining accuracy of the parts will also be affected differently. For example, in the case where the rigidity of the arbor is smaller than the rigidity of the outer turning tool, the difference in rigidity between the shank causes deformation of the arbor, thereby affecting the accuracy of the hole of the part. When the tool and machine tool stiffness is much larger than the workpiece, the part will be deformed. Due to the pressure of the machine itself, it also has a rigid change, and the machining accuracy of the parts is affected [4]. In order to prevent the machining error of parts caused by external forces, it is also necessary to reduce the degree of stress on the system load and to solve the weak points of the system. Specifically, it is the choice of processing materials and machine tools to improve the stability and service life of the system.

During the machining of the part, it will generate some residual stress. For example, when the parts are cast and forged after cooling, the previously generated blank stress will cause different cooling shrinkage speeds in the parts where the thickness is uneven or the structure is complicated. In the case of internal stress generation, the machining accuracy of the part is affected. In order to solve this problem, it is also necessary to use natural aging and artificial aging to eliminate residual stress. Specifically, the formed blank is placed for a period of time after the part is cast and forged. During this time, as the temperature decreases, the stress inside the part will gradually disappear. For artificial aging, the machined parts need to be reheated and then cooled with the furnace at a certain temperature. In addition to using the thermal cooling method, the vibration device can also be used to resonate the parts to eliminate the internal stress of the part.


2.4 Influence of thermal deformation on machining accuracy of parts

A large amount of heat is generated during the processing of the part, which causes the system to heat and deform and affect the machining accuracy of the part. First, the workpiece will deform under thermal erosion, which will affect the accuracy of the workpiece. In response to this problem, it is also necessary to use a coolant to prevent thermal deformation of the workpiece. Secondly, the tool generates a lot of heat during the cutting process, which causes the tool to be thermally deformed. To avoid this problem, coolant and lubricant are also needed to speed up tool cooling. In addition, the machine tool will also undergo thermal deformation when the heat source is unevenly walked and the structure is complicated, and corresponding measures must be taken for control.


3 Conclusion

All in all, in the process of parts processing, the influence of the machining process on the machining accuracy of the parts should be recognized, and a reasonable way to improve the machining process is sought, and then the machining accuracy of the parts is improved.

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