How to quantify poor balance Because the imbalance is caused by the deviation of the inertial axis line from the rotating axis line, that is, the rotating parts have the problem of uneven mass on the rotating axis line, the imbalance can be quantified by the following unit values: Unit of 1. weight: g. 2. torque unit: g-mm. 3. eccentricity (e): mm (or mm). 4. balance grade (G): mm/sec. ISO-1940 Level of Balance - G ISO-1940 level of balance - G defined as G=ωe=(2πf) e Of which ω is angular velocity, e is eccentric, f is rotational speed The above definition shows that the unit of equilibrium grade G is mm/sec, although at first glance G value looks like a velocity value, many people in industry even consider it vibration velocity value and use e value as vibration displacement value, because it is usually not clear that the definition of equilibrium grade is that vibration is associated with equilibrium. Where is the standard of balance The most widely used balance standard is the reference table ISO-1940, the following is the balance grade - G. From the following table, we can see that the higher the precision of the equipment, the smaller the G value (the higher the balance requirement), the higher the speed of the equipment at the same balance grade, the smaller the allowable residual eccentricity. How to Balance Calibration In general, all rotating parts should be regularly balanced correction, if the factory has the tools to detect vibration problems, only when the balance condition is detected is not good. The methods of balancing correction include: 1. Static Equilibrium Method - Equilibrium Correction by Gravity Balance Method of 2. Balancer - Balance Correction by Balancer 3. on-line dynamic balancing method - correction by balance or vibrometer. Static Balance Method This method is only suitable for rotating parts with static imbalance problem. Without considering the friction force at the supporting point of the rotating part, the point of gravity causing the imbalance will always remain directly below the rotating part when the rotating part is rotated, and no matter how the rotating part rotates, there will be no further imbalance. Disadvantages of the static balance method 1. when considering the friction of the supporting point (bearing), it is possible that because the friction force is greater than the unbalanced amount, the unbalanced amount can not be determined, which leads to the failure to reach the true balance when the rotating part is running. 2. static imbalance improvement method is only suitable for rotating parts with very narrow axial width. if we have a very wide rotating part, it may be difficult for us to determine the position of the matching weight, because we do not know the axial position of the unbalanced weight. when we place a counterweight equal to the resulting unbalanced weight at one end, it may lead to imbalance at the other end and form even imbalance. Balance Machine As the name implies, the balancing law system uses the balancing machine to carry on the balance correction of the rotating parts, this method and the static balance method are more generally known, usually the rotating parts after the manufacture or maintenance is completed, will first carry on the balance correction with the balancing machine to ensure the factory quality. Since it is necessary to remove the whole rotating parts and send them out together to correct the balancing machine, it is more time-consuming and costly to correct. Disadvantages of balancing machine 1. must first confirm the imbalance problem with the unbalanced unit or component. 2. the entire rotation must be removed. 3. the cost of working hours, reduce equipment farming rate. 4. usually can not use the actual working speed for correction. 5. handling and installation process can easily make the balance worse. On-line dynamic balancing method The principle used in the general online dynamic equilibrium method is vector equilibrium method, which can be divided into two categories: 1. simple dynamic balance: Use vibrometer, with appropriate test weight and compasses, ruler, estimate the imbalance angle and the size of the imbalance. There are two kinds of two-point balance correction method and three-point balance correction method. 2. precision dynamic balance: Using special dynamic balance instrument with vibration sensor and phase meter can grasp accurately The angle of imbalance and the magnitude of imbalance. Principle of online dynamic balance technology Using the polar coordinate diagram to represent the vibration value and phase angle caused by the imbalance, we can calculate the balance weight and counterweight angle clearly and simply. Compare the relationship between the test weight and the original imbalance to know where to match the weight. Precision on-line dynamic balancing technology is online dynamic balance work easy to do? Online dynamic balance The work is so simple! The Basic Concept of Precision Dynamic Balance 1. poor balance produces centrifugal force. 2. purpose of dynamic balance correction is to balance the force. Application of Balancer - Vibration Sensor and Phase Meter: Vibration Size ® Vibration Sensor ® magnitude of imbalances ® Balance Weight Determination ® vibration phase ® imbalance angle ® Balance Weight Position Determination General Steps for Precision Online Dynamic Balance 1. measure the vibration and phase of the machine due to imbalance in the original condition (without any test weight). 2. add a try on the turning part. The vibration value and phase of the new imbalance formed after measuring and adding test weight. 3. balance instrument automatically calculates the relative relationship between vibration value and phase change before and after the test weight, and calculates the balance weight. 4. the balance weight calculated by the balancer is on the turning piece. 5. measured the vibration and phase after equilibrium improvement. 6. use the analyzer to analyze and calculate the small balance weight so that the machine can achieve better balance. Key points for implementing online dynamic balancing 1. performing the on-line dynamic balance process, the rotational speed must be maintained to a certain extent. 2. performing on-line dynamic balancing, the vibration sensor and the phase meter must be fixed in the same position and not movable. 3. the phasor as far as possible to install in a non-sloshing plane. 4. the vibration sensor as close as possible to the bearing and place in a horizontal or vertical position. 5. when the initial balance condition of the equipment is very poor, it is suggested that the static balance method should be used to improve the balance condition balance correction.