© Siemens AG 2015 FLENDER Standard Couplings Technical Information Balancing Because of primary shaping processes and machining, the cou- pling components are manufactured with a mass distribution about the axis of rotation of the motor, gear unit or driven ma- chine which is not always ideal. Full parallel key standard The parallel key is inserted in the shaft keyway, then balancing is carried out. The coupling hub must be balanced without par- allel key after keyseating. Marking of shaft and hub with "F" (for "full"). Balancing means improving the mass distribution of a rotating body so that it rotates on its bearings with a sufficiently limited effect of free centrifugal forces.
Half parallel key standard The balancing standard normally applied today. Before balanc- ing, a half parallel key is inserted in the shaft and another in the coupling hub. Alternatively, balancing can be carried out before cutting the keyway. The balanced parts must be marked with an "H". This marking can be dispensed with if it is absolutely clear which parallel key standard has been applied. 2 : ) U D 6 8 No parallel key standard Balancing of shaft and coupling hub after keyseating, but with- out parallel key. Not used in practice. Marking of shaft and hub with "N" (for "no"). H The length of the parallel key is determined by the shaft keyway.
Coupling hubs may be designed considerably shorter than the shaft. To prevent imbalance forces caused by projecting parallel key factors when balancing in accordance with the half parallel key standard in the case of applications with high balancing quality requirements, grooved spacer rings can be fitted or stepped parallel keys used. *B0'B;;B The imbalance force increases linearly with the distance be- tween the center of gravity of the body and the axis of rotation, the weight of the body and the rotor speed squared.
F = imbalance force S = center of gravity of the body e = distance of center of gravity of body from the pivot axis Siemens Balancing Standard The balancing quality level, together with the operating speed, results in the maximum permissible eccentricity of the center of gravity of the coupling or the coupling subassembly. In the Siemens article number the balancing quality can be preset with the help of the order code. Additionally, also the balance quality level to DIN ISO 1940 can be preset together with the operating speed belonging to it, which then be taken as priority.
In the case of rotating unbalanced coupling parts rotary, imbal- ance forces develop which impose loads on the bearings of the machine shafts and excite vibration. High vibration values on drives are frequently detected as early as initial start-up if the balance of the machine shafts or the mounted coupling parts is insufficient or the balancing specifications are incompatible. The balance condition of the coupling can be measured on balanc- ing machines. By adding or drilling away material, a balance condition which meets the requirements can be achieved. The procedure to determine the Siemens balancing quality is as follows:
Operating speed and required balancing quality level are known from the application. Using these values, the required eccentric- ity of the center of gravity can be calculated using the specified formula context or the following graph. The eccentricity of the center of gravity of the coupling must be less than the required eccentricity of the center of gravity to achieve the required bal- ancing quality.
The associated article number must be stated in the order; only if standard balancing has been selected is the ar- ticle number to be dispensed with Balance quality levels The so-called quality level G to DIN ISO 1940 indicates a range of permitted residual imbalance from zero up to an upper limit. Applications can be grouped on the basis of similarity analysis. For many applications a coupling balance quality of G 16 is suf- ficient. On drives susceptible to vibration the balance quality should be G 6.3. Only in special cases is a better balance qual- ity required. e perm 9600 G Single- and two-level balancing e coupl ≤ e perm.
n ---- ⋅ = For discoid bodies (such as brake disks, coupling hubs) so- called single-level balancing is carried out. The mass compen- sation for the imbalance is undertaken at a single level only. For historical reasons single-level balancing is also known as static balancing. On long bodies such as adapters mass compensa- tion must be implemented at two levels to reduce the couple im- balance. Two-level balancing is carried out while the rotor body is rotating. Historically, this is known as dynamic balancing. permitted: Eccentricity of center of gravity e perm.
in μ m Eccentricity of center of gravity of the coupling e coupl in μ m Balancing quality level G in mm/s Coupling speed n in rpm Balancing standard in accordance with DIN ISO 21940-32 Besides the required balance quality, it is necessary to set stan- dards which define how the mass of the parallel key is to be taken into consideration when balancing. In the past, motor ro- tors have frequently been balanced in accordance with the full parallel key standard. The "appropriate" balance condition of the coupling hub was described as "balancing with open keyway" or "balancing after keyseating".
Today it is usual for the motor rotor, as well as the gear unit and driven machine shaft, to be bal- anced in accordance with the half parallel key standard. Order code to determine the balance quality level to DIN ISO 1940 and the operating speed: Y95 {G = __; n = __rpm}. 2/3 Siemens MD 10.1 · 2015 Eccentricity of center of gravity of coupling ecoupl Siemens balancing quality Order code maximum 100 μm standard balancing without specification maximum 40 μm fine balancing W02 maximum 16 μm micro-balancing W03 better than 16 μm special balancing on request