The principle of dynamic balance of a rotating tool is similar to that of a normally rotating part.First, the design of tool structure should be as symmetrical as possible;Secondly, when the tool needs to be balanced, the measured unbalance can be achieved by means of the tool handle to be weighed or the counterweight to be adjusted.Due to the variety of tools, the specific balance method is not the same.The special balance tool (handle) is equipped with a balance weight mechanism, and set the balance scale, according to the rotation of the balance ring, adjust its relative position, can compensate the unbalance caused by the asymmetric structure of the tool or tool adjustment;High-speed face milling cutter is the choice of screw adjustment unbalance.
For the general tool or tool system, tool manufacturers or customers with dynamic balancing machine balance.However, how to scientifically and quantitatively define and evaluate the quality of dynamic balance of cutting tools and the allowable unbalance of cutting tools under different production and processing standards is the main concern of cutting tool manufacturers and customers.Therefore, it is necessary to introduce the general concept of dynamic balance of mechanical rotor.
According to the standard of IS01940 dynamic balance quality requirements for rigid rotors, the unbalance (or residual dynamic unbalance) of one rotor is expressed by U (unit is GMM), and U value can be measured on the dynamic balancing machine.The allowable dynamic unbalance (or residual dynamic unbalance) of a rotor is expressed by Uper.Considering the actual balancing effect, the larger the mass m (kg) of the rotor is, the larger the residual unbalance is.In order to make a relative comparison of the flat mass of the rotor, residual unbalance per unit mass can be expressed as e, that is, e = U/m (GMM/kg), and eper = Uper/m accordingly.U and e are the static (or quasi-dynamic) characteristics of the rotor itself for a given rotary shaft, and can quantitatively represent the degree of imbalance of the rotor.From the quasi-dynamic point of view, a rotor whose static characteristics are represented by U, e and m values is completely equivalent to an unbalanced rotor whose mass is m (kg) and eccentricity is e (m) between its center of gravity and the center of rotation, and U value is the product of the rotor mass m (kg) and eccentricity e (m).Therefore, e can also be called residual eccentricity, which is a very useful physical meaning of e.
In fact, the quality of a rotor balance is a dynamic concept, which is related to the speed of use.Such as ISO1940 criteria given balance quality grade graph G is a set of discrete marked on the value of 45 ° oblique line to express the balance of different quality grade, its value for eper (GMM/kg) and angular velocity omega (rad/s) of product (in mm/s), is used to express a rotor balance quality.For example, if the equilibrium mass level G = 6.3 of a rotor, the product of the value e of the rotor and the value in application should be less than or equal to 6.3.When applied, according to the standard balance mass grade G and the maximum possible rotation speed of the rotor, the allowable eper value of the rotor can be found on the graph, and then multiplied by the rotor mass, the allowable unbalance of the rotor can be obtained.
The next problem is how to determine the reasonable balance quality grade G of the high-speed rotary cutter, so as to obtain the required Uper value at the highest operating speed.