Possible causes of five-axis AC axis vibration
1. Reasons related to mechanical components
Problems with the driveshaft itself
Bending deformation and eccentricity: If the transmission shaft of a five-axis machine tool is used for a long time, especially if there is strong vibration in the working environment or it is bumped during transportation, just like a car’s driveshaft when driving. uneven roads, front and rear components. Relative movement can cause bending and distortion of the driveshaft, loss of balance and vibration. In this case, due to the change in shape of the transmission shaft during rotation, the mass distribution is no longer uniform and shaking will occur.
Loss of balance: in addition to bending deformation, the assembly error of the drive shaft exceeds the limit, the parts are inaccurate in size, and wear and deformation during use will cause distribution unequal mass along the length of the drive shaft. For example, there are dimensional deviations during processing of the transmission shaft, or some parts are worn after long-term use, resulting in unbalanced force transmission and additional bending moments during operation. but also improves the bending vibration of the transmission shaft, making the AC axis vibrate.
Balancing part problem: If the balancing part on the transmission shaft falls off or the installation position of both ends is changed (it should be in the same plane and angles between the input shaft , the output shaft and the transmission shaft are equal), this will destroy the equilibrium state of the transmission shaft. This will also destroy the condition of isokinetic force transmission. This will cause impact to the drive components and cause unstable operation of the drive shaft, thereby increasing abnormal vibration and noise. Just as in some high-precision transmission equipment, the condition of the balance wheel is crucial for the stable operation of the transmission shaft.
Universal joint problem
Wear: Wear of the universal joint (cross journal and needle bearing) will gradually increase the mounting gap and cause imbalance, causing vibration. In the reciprocating axis transmission of five-axis machine tools, the universal joint continuously changes the transmission angle. If its components are worn, it will directly affect the smoothness of the transmission and cause instability.
Problem with connecting parts
Spline wear: The spline teeth of the second shaft of the transmission cover and the splines of the yoke of the transmission shaft are seriously worn, or the bearing of the second shaft is seriously worn. When axial movement and power transmission continue to occur during use, wear will occur. gradually increases, resulting in loose connection or unstable transmission, causing the AC shaft to vibrate. This situation is similar to that of a car’s transmission system. When similar components wear out, it will affect the stability of power transmission and cause instability.
Loose Bolts: The bolts connecting the rear axle flange to the driveshaft are loose, which will cause the rear end of the driveshaft to move, causing the driveshaft to vibrate. In five-axis equipment, if the connection bolts related to the AC axis are loose, it will destroy the stability of the entire transmission structure and cause vibration.
2. Reasons related to the electrical system
Motor problem (if the AC axis is driven by a motor)
When the motor is rotating, if the motor is eccentric, different positions of the motor bearings will bear different loads, resulting in an unbalanced motion state, which will cause the motor shaft to beat, and finally cause the AC shaft to vibrate. . For example, inaccurate positioning during motor installation or movement of the motor base during use may result in motor eccentricity.
When the motor is running, due to poor bearing lubrication or insufficient heat dissipation, the motor will overheat, which may cause the motor shaft to beat. Excessive heat will cause the bearings to deform and harden, leading to an increase in the coefficient of friction of the motor bearings, which in turn will cause the motor shaft to beat. This beat will be transmitted to the AC shaft, causing the AC shaft to vibrate. Just like when a motor operates at high load for a long time and does not have effective heat dissipation measures, shaft kickback problems caused by overheating are likely to occur.
When the motor is running, if the bearing is subjected to impact or excessive load, the bearing is easily damaged, causing the gap between the bearings to increase or swing. As a result, problems such as skipping and vibration will occur when the motor is running, which will affect the stability of the AC axis and cause jitter. For example, in working conditions with frequent starts and stops or sudden load changes, motor bearings are prone to this problem.
Damage to motor bearings
Engine overheating
Motor eccentricity
3. Other possible reasons
Uneven load: If the load distribution of the five-axis AC axis is uneven during work, for example, the cutting force is uneven when processing the workpiece and the force on one side is too large, a Unequal torque will be generated on the AC. axis, causing the AC axis to vibrate.
Insufficient lubrication: If the various moving parts of the AC axis are not sufficiently lubricated, the friction coefficient will increase, the resistance to movement will increase, and blockages and vibrations will easily occur. For example, after long-term operation, this situation will occur if the lubricating oil is consumed or deteriorates and is not replenished or replaced in time.
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