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Research on improving the processing precision of thin-walled parts(1)

Release time:Apr 24, 2019 Visits:

I. Introduction

In modern industrial manufacturing, there are more and more thin-walled structures, especially in the high-precision fields such as aerospace and radar communications. Most of the thin-walled parts in these fields are integral frames, beams, siding, etc. The strength of the wall structure should be as low as possible to reduce the weight of the parts, while meeting the requirements of the complexity of the part structure and the complex shape. However, the relative rigidity and strength of the thin-walled members are poor and the structure is irregular, which makes the clamping in the manufacturing process difficult, the parts are easily deformed, and the process is easy to vibrate and destabilize during the processing, so that the processing quality is greatly reduced. Manufacturing brings great difficulties. Therefore, from the perspectives of equipment selection, workpiece clamping, tool selection, part processing technology analysis, program preparation, etc., the factors affecting the processing quality of thin-walled parts are fully analyzed, and the corresponding solutions are found. The basic approach to the machining accuracy of wall parts.

Second, the reason for the deformation of thin-walled parts

External force clamping

During the machining process, the workpiece is subjected to cutting force, centrifugal force, inertial force, etc., in order to ensure that under these external forces, the workpiece can still maintain the machining position determined by the positioning element in the fixture without vibration or displacement. A clamping device should be provided in the fixture structure to securely clamp the workpiece. However, in the clamping process, since the structure of the part is a thin-walled structure, the strength of the part is low, and it is easily deformed under the action of the clamping force. For example, a thin-walled sleeve-like part, if clamped by a conventional three-jaw chuck, causes deformation of the part, and the circular deformation is triangular, and the quality of the processing cannot be guaranteed.

2. Cutting force

In the machining process, the cutting process is completed by the relative movement between the tool and the workpiece according to a certain trajectory, so the interaction force between the tool and the part is formed during the cutting process [3]. In turning, the cutting force can be decomposed into axial force and radial force, wherein the radial force is perpendicular to the part axis, causing the part to bend, making the part deform more, forming a drum-shaped surface on the surface of the part after cutting, causing serious shape error. . During the milling process, if the force-receiving surface of the part does not have sufficient support, the part will also be deformed, causing the machined surface to bulge, forming a so-called undercut condition. Therefore, the cutting force is a key factor affecting the machining accuracy of thin-walled parts.

3. Thermal deformation

In the metal cutting process, a strong cutting heat is formed due to strong contact and friction between the tool and the workpiece. The heat of cutting can cause severe deformation of the workpiece, especially for thin-walled parts. At the same time, the accumulation and increase of heat will cause the wear of the tool to increase, and eventually the machining accuracy of the part will be reduced.

In addition, the high-speed rotation of the spindle will also generate heat, which will make the spindle extend. The machining position of the part will be changed in the lathe. The position of the tool will be changed during milling, but the final change will be the relative position of the workpiece and the part, resulting in machining error. , affecting the machining accuracy of the parts.

4. Vibration

There are many reasons for the vibration generated by machining, including forced vibration generated by the machine's own structure, such as high-speed rotation of the motor, unbalanced mechanical structure, and unstable oil pump operation, which will cause forced vibration of the machine tool, which will affect the thin wall. The accuracy of the assembly of the parts and the machining of the workpiece [4]. At the same time, the alternating force generated by the machine tool during the machining process causes vibrations that are not attenuated, which may affect the accuracy of the parts due to deformation of the machining process. For example, during the grinding process, the friction generated by the grinding wheel on the workpiece causes a large undamped vibration, which affects the quality of the ground surface.

5. The processing technology is unreasonable

In mechanical processing, the processing technology and processing method directly affect the accuracy of the parts. Unreasonable processing steps and processing sequences will cause large deformation of the parts. Therefore, a reasonable processing process is the key link to ensure small deformation of parts and improve processing quality.

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