One of the common defects in the processing of the turning point is vibrations. When the Tour vibrates, the normal cutting process of the process system is disturbed and damaged, which not only seriously deteriorates the quality of treatment surface, but also shorten the life of the machine and the tool. Therefore, it is necessary to take certain measures to reduce or eliminate the vibrations of the tool-machine.
0
1
The main characteristics of low -frequency vibrations
After eliminating the vibrations of the components and transmissions of ignition of the machine tool, the main type of turn vibration is the self-exciting vibrations which do not change with the speed of turn. Today, we will mainly introduce the causes and measurements to eliminate low-frequency vibrations caused by the deformation of the part system and the deformation of the tool holder system during treatment.
The main characteristics of low -frequency vibrations are: ① The frequency of vibrations is low (50 ~ 300 Hz), and the noise emitted during the vibration is low; is relatively violent, which often causes components of machine tools (like tail seats).
0
2
Causes of low -frequency vibrations
When the low -frequency vibration is carried out during the turn, the part system and the tool support system generally vibrate (but in most cases, the part system vibrates considerably and plays a dominant position). Size directions. During the vibration process, when the part and the tool move in a phase separation, the F cut force F is the same as the direction of movement of the part, and the work done is positive, as shown in the figure 1 (a). When the part is approaching the tool, the work carried out by the F Fil force F is negative, as shown in Figure 1 (B).
During the rotation process: ① The friction between the chips and the front of the tool, ② The degree of hardening of the metal encountered by the tool when cutting and leaving the part is different, ③ The Real geometric angle of the tool changes periodically during the process vibration, ④ When it is vibrant, the tool associates the relative movement trajectory of the part is elliptical, which causes periodic changes in the cutting section, and Traces left by the vibration of the part during the previous rotation, causing periodic changes in the cutting section. All these five situations can cause periodic changes in the cutting force and make a phase approach f> f. In this way, in each vibration period, the positive work carried out by the cutting force on the part (or the tool) is always higher than the negative work carried out by it on the part (or the tool), so that The part (or the tool) can obtain energy replenishment and generate self-exciting vibrations.
0
3
Measures to eliminate low -frequency vibrations
(1) When the vibration is low frequency, the vibration in the direction causes changes in the cutting force, causing an approach to phase F> F and vibrations.
The following four measures are mainly taken.
① The more the main deviation angle (angle μr) of the tool is greater, the smaller the force FY, and the less it is likely to produce vibrations. Therefore, the main deviation angle of the tool is correctly increased to eliminate or reduce vibrations.
② The appropriate increase in the front angle of the tool can reduce Fy force and thus reduce vibrations.
③ If the rear area of the tool is too large or the blade is too clear, the tool is easy to chew in the room and to vibrate easily. When the tool is properly passed, its surface of the rear blade has the effect of preventing the tool from “walking in” the room, which can reduce or eliminate vibrations.
④ When you turn, the position of the tip of the tool is too low (under the center of the room) or when it is boring on the Tour, the position of the tip of the tool is too high, which will reduce the real front of the tip of the tool and increase the rear angle, which is subject to vibrations.
⑤ If the tool support system has negative rigidity, it is easy to “chew” the part and cause vibrations. Consequently, the vibrations caused by the negative rigidity of the tool support system during the turn are avoided as much as possible.
(2) When wide and thin fleas are generated during the film process, the vibrations in the direction cause changes in the cutting force. Sectional area and cutting force. Therefore, vibrations are very likely to occur in this case. For example: during the transformation of the longitudinal tool, the larger the cutting depth, the greater the supply volume, and the larger the main cutting angle, the greater the cutting section, And the more likely it is to produce vibrations. Therefore, when selecting a turn speed, you must avoid the average speed zone where the cutting force decreases with speed (when cutting the carbon steel, the speed range is 30 To 50 m / min) and at the same time, reduce the turning back the feeding force and appropriately increase the supply and the reduction in the cutting depth also help to remove the vibrations.
(3) The inadequate rigidity of the room system and the tool holder is the main reason for low-frequency vibrations.
① When tightening the room with three or four claws, the coaxial error between the room rotation center and the spindle rotation center must be minimized, so as to avoid vibrations caused by periodic changes of The cutting force caused by the inclination of the part and the intermittent cut or the cutting plant.
② When processing fine and long parts that are easy to deform, fold and vibrate, use elastic tips and an auxiliary support to cool the part while adding cooling fluid to reduce thermal dilation and deformation.
③Lorors of tightening the room, do not make the room for too long. For parts with insufficient stiffness, a reasonable central frame, a heel frame and a high -level auxiliary support are used to increase the rigidity of the part.
④ When you use the upper tip, the upper tip and the upper cone hole must be matched well to prevent the pinch force with too punching, which makes the work room fold or too small pinching force to play A support role and swing the part. The seat sleeve should not be too extensive.
⑤ The tuning of the machine-tool tank directly affects the rotation accuracy and the rigidity of the spindle. Rigidity of the part system and eliminate vibrations.
⑥ Regularly check the ignition between the belt guidance rails between the central drag plate and the large drag plate, the small chrossee and the average drag plate, and adjust the inclined inserts to keep the appropriate gaps To avoid crawling when the chopping carrier moves, causing vibrations of the knife support system.
⑦ Whenever the square knife support is turned to turn the tool in the desired position, the square knife support must be pressed and fixed to avoid the release of the square knife support to reduce the rigidity of the knife support system and cause vibrations.
Daguang focuses on providing solutions such as precision CNC machining services (3-axis, 4-axis, 5-axis machining), CNC milling, 3D printing and rapid prototyping services.
