{"id":3009,"date":"2025-07-16T14:38:26","date_gmt":"2025-07-16T12:38:26","guid":{"rendered":"https:\/\/hofmann-global.com\/?page_id=3009"},"modified":"2025-11-27T15:29:20","modified_gmt":"2025-11-27T14:29:20","slug":"glossary","status":"publish","type":"page","link":"https:\/\/hofmann-global.com\/en\/service\/glossar\/","title":{"rendered":"Glossary"},"content":{"rendered":"
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At a glance<\/p>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Glossary<\/h1>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Our glossary provides you with a quick overview of important balancing technology terms.<\/p>

This makes it easy for you to keep track of all technical terms and understand the context immediately.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Glossary of balancing technology<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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All<\/a> | A<\/a> \u00c4<\/a> B<\/a> D<\/a> E<\/a> F<\/a> G<\/a> H<\/a> I<\/a> J<\/a> K<\/a> L<\/a> M<\/a> N<\/a> P<\/a> Q<\/a> R<\/a> S<\/a> T<\/a> U<\/a> V<\/a> W<\/a> Z<\/a>
<\/form><\/div>
There are currently 121 names in this directory<\/div>
<\/a>Voting ratio<\/strong>
Ratio of the rotor speed to one of the critical speeds.<\/div><\/div>
<\/a>Equivalent unbalance for the nth eigenmode<\/strong>
The smallest single unbalance that has the same effect on the nth mode as the actual unbalance distribution in the elastic rotor.<\/div><\/div>
<\/a>Susceptibility to imbalances<\/strong>
Probability of a machine showing a significant change in unbalance within a certain operating time.<\/div><\/div>
<\/a>Display of an apparent imbalance<\/strong>
Display of imbalances that are not caused by imbalances.<\/div><\/div>
<\/a>ARP<\/strong>
Aerospace Recommended Practice.<\/div><\/div>
<\/a>Equalization<\/strong>
Changing the mass distribution of a rotor in such a way that the unbalance or the vibrations caused by it are reduced to permissible values. This is usually achieved by adding, removing or shifting material on the rotor.<\/div><\/div>
<\/a>Equalization level<\/strong>
Plane perpendicular to the shaft axis in which the unbalance is corrected.<\/div><\/div>
<\/a>Equalization level in\ufb02uence<\/strong>
Change in the unbalance display of one correction plane when the unbalance in the other correction plane changes; usually expressed as a percentage value. The better the plane separation, the lower the influence of the correction plane.<\/div><\/div>
<\/a>Leveling compound<\/strong>
Mass changed in a compensation plane to reduce the imbalance.<\/div><\/div>
<\/a>Outboard rotor<\/strong>
Rotor whose center of gravity is outside the bearings.<\/div><\/div>
<\/a>Balancing speed<\/strong>
Speed at which the rotor is balanced.<\/div><\/div>
<\/a>Balancing<\/strong>
Process during which the mass distribution of a rotor is checked and typically corrected so that the residual imbalances, the vibrations of the bearing journals, the bearing forces and\/or bearing pedestal vibrations at operating speed or in the operating speed range are within specified limits.<\/div><\/div>
<\/a>Balancing on reversal<\/strong>
Compensation of the unbalance of auxiliary parts and the unbalance effect due to fit clearance, radial and axial run-out between auxiliary parts and the rotor to be balanced in order to identify the actual rotor unbalance. The rotor is rotated in relation to the auxiliary part in successive measurements.<\/div><\/div>
<\/a>Balancing quality<\/strong>
Possibility of dividing rigid rotors into classes; product of mass eccentricity and angular velocity at operating speed or path velocity of the center of mass, each in mm\/s (see also ISO 21940-11).<\/div><\/div>
<\/a>Balancing putty<\/strong>
Typically used to attach a test mass to a rotor.<\/div><\/div>
<\/a>Balancing bearing<\/strong>
For example, rolling bearings with reduced clearance to accommodate an engine rotor in a low-speed balancing machine.<\/div><\/div>
<\/a>Balancing run<\/strong>
cycle, consisting of a measuring run and associated unbalance correction.<\/div><\/div>
<\/a>Balancing machine<\/strong>
Machine that generates a measured value for the unbalance of a rotor mounted in it, which can be used to correct the mass distribution.<\/div><\/div>
<\/a>Automatic balancing device<\/strong>
System that automatically compensates for changes in unbalance during operation.<\/div><\/div>
<\/a>Belt drive<\/strong>
Mechanical drive of a balancing machine consisting of motor, pulleys, drive belt and belt tensioner. The diameters of the motor pulley and the drive diameter of the rotor should not be too similar in order to avoid the occurrence of apparent imbalances.<\/div><\/div>
<\/a>Limited original imbalance<\/strong>
Limiting the initial imbalance by balancing the individual parts, well-considered design and targeted production and assembly.<\/div><\/div>
<\/a>Operational balancing<\/strong>
Balancing of a rotor not in a balancing machine, but in the operating bearing.<\/div><\/div>
<\/a>Operating balancer<\/strong>
Measuring system for balancing outside a balancing machine in operating condition.<\/div><\/div>
<\/a>Operating speed<\/strong>
Speed at which a rotor rotates during operation.<\/div><\/div>
<\/a>Related unbalance<\/strong>
Amount of static unbalance in relation to the mass of the rotor in gmm\/kg or \u00b5m.<\/div><\/div>
<\/a>Reference plane<\/strong>
Radial rotor plane to which an unbalance is referred.<\/div><\/div>
<\/a>Bending mold<\/strong>
Characteristic bending line with which a rotor deforms at a critical speed.<\/div><\/div>
<\/a>Bending-critical speed<\/strong>
Speed at which maximum deflection of the rotor occurs and this is significantly greater than the movement of the bearing journals.<\/div><\/div>
<\/a>Bode diagram<\/strong>
When balancing, the course of the magnitude and angle of an oscillation at rotor speed or twice the rotor speed over the speed.<\/div><\/div>
<\/a>Rotary axis<\/strong>
The straight line around which a rotor is currently rotating.<\/div><\/div>
<\/a>Dynamic imbalance<\/strong>
Condition for which the central main axis of inertia is neither parallel to the shaft axis nor intersects it.<\/div><\/div>
<\/a>Level separation<\/strong>
Ability of a balancing machine to distribute the unbalance precisely to the correction planes and to minimize the correction plane influence ratio.<\/div><\/div>
<\/a>Level shift<\/strong>
Conversion of the unbalance to other levels.<\/div><\/div>
<\/a>Eigenfunction, modal function<\/strong>
Describes the course of an eigenmode as a function of the rotor axial coordinate; function is normalized to a maximum value of one.<\/div><\/div>
<\/a>Single-plane balancing<\/strong>
Correction of the mass distribution of a rigid rotor in order to reduce the static residual unbalance to certain limit values.<\/div><\/div>
<\/a>Single-plane balancing machine<\/strong>
Balancing machine that uses gravity or centrifugal force to balance a rotor in one plane.<\/div><\/div>
<\/a>Screwing in<\/strong>
Rotate the rotor to position it at a specific angle.<\/div><\/div>
<\/a>Setting up the machine mechanics<\/strong>
Work to adjust the mechanics of a balancing machine to the balancing of a rotor.<\/div><\/div>
<\/a>Setting the measuring device<\/strong>
Work to enter rotor and balancing-specific data into the measuring device of a balancing machine.<\/div><\/div>
<\/a>Electrical concentricity deviation<\/strong>
Systematic error of eddy current sensors during concentricity or shaft vibration measurement caused by residual magnetism or electrical irregularities of the measured part.<\/div><\/div>
<\/a>Sensitivity to imbalances<\/strong>
Measure of the change in the vibration of an (elastic) rotor due to a change in unbalance, expressed by the ratio between the change in the vibration vector and the change in the unbalance vector.<\/div><\/div>
<\/a>Emp\ufb01tability of a balancing machine<\/strong>
Resolution of the unbalance display of a balancing machine.<\/div><\/div>
<\/a>Replacement mass<\/strong>
Mass attached to the crank pins of crankshafts to simulate part of the rotating and oscillating masses of the piston\/connecting rod assembly during balancing.<\/div><\/div>
<\/a>Spare rotor (dummy)<\/strong>
Accessories that replace a rotor assembly during balancing. The replacement rotor must have the same main dimensions, mass and rigidity properties as the original part.<\/div><\/div>
<\/a>Flying<\/strong>
An axial position outside the bearings.<\/div><\/div>
<\/a>Centrifugal balancing machine<\/strong>
Machine that generates measured values for the unbalance due to the centrifugal forces of a rotating rotor mounted in it.<\/div><\/div>
<\/a>Foundation<\/strong>
Structure that supports the balancing machine.<\/div><\/div>
<\/a>Cardan shaft drive<\/strong>
Mechanical drive of a balancing machine consisting of a motor, optional gearbox and cardan shaft. The cardan shaft is connected to one end of the rotor to be balanced.<\/div><\/div>
<\/a>Total concentricity deviation<\/strong>
Difference between the maximum and minimum value of the radii of a rotor cross-section when measured with respect to a fixed axis of rotation.<\/div><\/div>
<\/a>Half feather key<\/strong>
Special key for balancing, which represents the unbalance effect of the part of the correct key in relation to the shaft or hub (see also ISO 21940-32).<\/div><\/div>
<\/a>Main axis of inertia<\/strong>
Depending on the unbalance condition of a rigid rotor, the main axis of inertia is offset and inclined in relation to the design axis.<\/div><\/div>
<\/a>Auxiliary wave<\/strong>
Precisely manufactured shaft that accommodates a rotor without its own journal for balancing.<\/div><\/div>
<\/a>High-speed balancing<\/strong>
Balancing of elastic rotors at speeds at which a rotor to be balanced can no longer be considered rigid.<\/div><\/div>
<\/a>Horizontal balancing machine<\/strong>
Balancing machine that measures the unbalance for horizontal alignment of the rotor axis.<\/div><\/div>
<\/a>Inboard rotor<\/strong>
Rotor whose center of gravity is between the bearings.<\/div><\/div>
<\/a>Isotropic storage<\/strong>
Bearing with the same dynamic properties in every radial direction.<\/div><\/div>
<\/a>Adjustment<\/strong>
In balancing, the process of adjusting a machine or device so that the measurement information is converted into unbalance units for the bearing points and\/or the balancing planes of a rotor.<\/div><\/div>
<\/a>Calibration mass<\/strong>
Defined mass to adjust a balancing machine with a specific rotor or to adjust a balancing machine for a specific rotor.<\/div><\/div>
<\/a>Calibration rotor (master rotor)<\/strong>
Adjustment rotor derived from a real rotor with defined positions for the application of calibration masses; used for the regular inspection of a balancing machine.<\/div><\/div>
<\/a>Smallest achievable residual imbalance (KER)<\/strong>
The smallest value of residual unbalance that can be achieved with a balancing machine.<\/div><\/div>
<\/a>Compensate<\/strong>
Suppression of an error or an undesired effect.<\/div><\/div>
<\/a>Component equalization<\/strong>
Correction of the unbalance at at least two angular positions if the angular positions are specified in a correction plane.<\/div><\/div>
<\/a>Force-measuring balancing machine<\/strong>
Machine on which rotors are balanced below the critical speed of the rotor-balancing machine bearing system.<\/div><\/div>
<\/a>Critical speed<\/strong>
A characteristic speed at which resonance occurs in the rotor-bearing system.<\/div><\/div>
<\/a>Storage rack<\/strong>
Component of a balancing machine with the rotor bearing, which transmits the forces of the rotor to the machine bed.<\/div><\/div>
<\/a>Bearing journal<\/strong>
Part of the rotor that rotates in a bearing and is guided by it.<\/div><\/div>
<\/a>Bearing journal center point<\/strong>
Axial rotor plane in which a bearing force acts.<\/div><\/div>
<\/a>Contract balancing (balancing service)<\/strong>
Service provided by a company to balance rotors on behalf of a customer or to examine their unbalance condition.<\/div><\/div>
<\/a>Local mass eccentricity<\/strong>
Distance of the center of mass of (imaginary) thin rotor disks from the shaft axis.<\/div><\/div>
<\/a>Mass eccentricity<\/strong>
For a rigid rotor, the distance of the center of mass from the shaft axis.<\/div><\/div>
<\/a>Center of mass or center of gravity<\/strong>
The point in an axially and radially extended (rigid) rotor at which its inertia effect against linear displacements can be replaced by a point mass.<\/div><\/div>
<\/a>Mass centering (balance centering)<\/strong>
Determination of the main axis of inertia of a rotor; information is used in the subsequent machining of the bearing journals, centering or reference surfaces so that the subsequent axis of rotation is as close as possible to the main axis of inertia.<\/div><\/div>
<\/a>Multi-plane balancing<\/strong>
Processes that use more than two planes for balancing flexible rotors.<\/div><\/div>
<\/a>Exhibition level<\/strong>
Radial rotor plane for which the unbalance vector is determined.<\/div><\/div>
<\/a>Modal balancing<\/strong>
Method that uses the information about the bending eigenmodes in the vicinity of the respective critical speeds to balance elastic rotors.<\/div><\/div>
<\/a>Moment imbalance<\/strong>
Unbalance condition in which the central main axis of inertia intersects the shaft axis at the shear point; typically caused by two equally large unbalances that are 180 degrees opposite each other.<\/div><\/div>
<\/a>Compliant rotor<\/strong>
Rotor which, due to an unbalance distribution and depending on the speed, exhibits deformations that can no longer be neglected.<\/div><\/div>
<\/a>Rebalancing<\/strong>
Compensation of small residual imbalances - mostly for the operating condition.<\/div><\/div>
<\/a>Low-speed balancing<\/strong>
Balancing for the rigid state of an elastic rotor.<\/div><\/div>
<\/a>Zeroing<\/strong>
Method of compensating for the current unbalance values and thus - using software - generating a fully balanced rotor, e.g. to check the plane separation.<\/div><\/div>
<\/a>Usable diameter<\/strong>
The largest rotor diameter for which a balancing machine can be used.<\/div><\/div>
<\/a>Permanent calibration<\/strong>
One-off calibration valid for all rotors within the weight and speed range of a force-measuring balancing machine.<\/div><\/div>
<\/a>Piezoelectric material<\/strong>
Hard ceramic material that produces an electrical charge when subjected to mechanical pressure. Used in force sensors to measure the effect of rotor imbalance in a balancing machine.<\/div><\/div>
<\/a>Polar diagram<\/strong>
Representation of the amount and angle of vibration and unbalance values measured at variable speed with the corresponding X and Y values in a circular diagram.<\/div><\/div>
<\/a>Polar compensation<\/strong>
Correction of the unbalance amount in a correction plane at a single angular position.<\/div><\/div>
<\/a>Practical equalization unit<\/strong>
Display of the unbalance amount for a specified compensation radius directly e.g. in mm drilling depth, number of washers etc..<\/div><\/div>
<\/a>Tasting mass<\/strong>
Usefully selected mass to determine the response of the rotor to an unbalance in a plane.<\/div><\/div>
<\/a>Test rotor (test rotor)<\/strong>
Rigid balanced rotor with suitable mass for adjusting and testing balancing machines; allows the exact, reproducible application of test or calibration masses.<\/div><\/div>
<\/a>Quasi-static imbalance<\/strong>
Unbalance condition in which the central main axis of inertia intersects the shaft axis at a point where the center of gravity is not located; e.g. caused by a single unbalance outside the center of gravity or in a form of dynamic unbalance where the static unbalance component coincides with one of the two moment components.<\/div><\/div>
<\/a>Residual imbalance<\/strong>
The unbalance of any kind that remains after balancing.<\/div><\/div>
<\/a>Rotor<\/strong>
A body that can rotate and usually has pins that are guided in bearings<\/div><\/div>
<\/a>Concentricity deviation at low speed<\/strong>
The concentricity deviation of a rotor surface measured at a low speed at which no significant vibration caused by unbalance occurs; value is usually compensated for measurements at variable speed.<\/div><\/div>
<\/a>Shaft or rotor axis<\/strong>
Straight through the centers of the bearing journal cross-sections.<\/div><\/div>
<\/a>Step-by-step balancing during assembly<\/strong>
Method for balancing a rotor that consists of several removable components. The unbalance is corrected on the last mounted component until the rotor is complete.<\/div><\/div>
<\/a>Gravity balancing machine (center of gravity balance)<\/strong>
Machine that generates a measured value for the unbalance due to the gravitational effect of a non-rotating rotor mounted in it.<\/div><\/div>
<\/a>Side spindle balancing machine<\/strong>
Design of a balancing machine in which the rotor is mounted horizontally overhanging on a balancing spindle<\/div><\/div>
<\/a>Rigid rotor<\/strong>
With a rigid rotor, the deformations due to unbalance distribution remain negligible up to the maximum operating speed.<\/div><\/div>
<\/a>Static imbalance<\/strong>
Unbalance condition for which the central main axis of inertia is displaced parallel to the shaft axis.<\/div><\/div>
<\/a>Thermally induced imbalance<\/strong>
Temperature-related change in the unbalance condition of a rotor.<\/div><\/div>
<\/a>Dead mass<\/strong>
Parts with mass of a balancing machine that are moved by the unbalance forces of the rotor to be balanced.<\/div><\/div>
<\/a>Unbalance<\/strong>
The condition of a rotor when imbalances in the bearings cause forces and\/or vibrations to circulate with the rotor. Unbalance is specified in gmm (or similar units).<\/div><\/div>
<\/a>Unbalance in the nth eigenmode, nth modal unbalance<\/strong>
Unbalance distribution that only influences the nth mode of deflection of an elastic rotor.<\/div><\/div>
<\/a>Unbalance amount<\/strong>
Product of the unbalance mass and the radial distance of its center of gravity from the shaft axis without reference to the angular position.<\/div><\/div>
<\/a>Unbalance force<\/strong>
Force in the balancing plane of a rotor that is created by the unbalance in this plane at a certain speed.<\/div><\/div>
<\/a>Unbalance mass<\/strong>
Mass whose center of gravity is located at a distance from the shaft axis.<\/div><\/div>
<\/a>Unbalance reduction ratio (URV)<\/strong>
Ratio between the decrease in unbalance due to a correction and the previous unbalance.<\/div><\/div>
<\/a>Unbalance tolerance of an intrinsic mold<\/strong>
Limit value for the equivalent unbalance of a natural form of an elastic rotor.<\/div><\/div>
<\/a>Unbalance tolerance, permissible residual unbalance<\/strong>
Permissible value of the unbalance amount in a radial plane for a rigid rotor.<\/div><\/div>
<\/a>Unbalance vector<\/strong>
Vector given by unbalance amount and unbalance angle.<\/div><\/div>
<\/a>Unbalance angle<\/strong>
Angle at which the unbalance mass is located in a coordinate system connected to the rotor.<\/div><\/div>
<\/a>Primordial imbalance<\/strong>
Angle at which the unbalance mass is located in a coordinate system connected to the rotor.<\/div><\/div>
<\/a>Comparative precision<\/strong>
For a balancing machine, a measure of the quality of the unbalance measurement for repeat measurements under changed conditions; evaluation using statistical methods.<\/div><\/div>
<\/a>Vertical balancing machine<\/strong>
Balancing machine that measures the unbalance for vertical alignment of the rotor axis.<\/div><\/div>
<\/a>Fully balanced rotor<\/strong>
Ideal rotor without imbalance.<\/div><\/div>
<\/a>Displacement measuring balancing machine<\/strong>
Machine on which rotors are balanced above the critical speed of the rotor-balancing machine bearing system.<\/div><\/div>
<\/a>Repeatability<\/strong>
For a balancing machine, a measure of the quality of the unbalance measurement in repeated measurements under the same conditions; evaluation using statistical methods.<\/div><\/div>
<\/a>Angle reference mark<\/strong>
Marking on the rotor to create a rotor-fixed angle reference system.<\/div><\/div>
<\/a>Angle position sensor<\/strong>
Component of a balancing machine that generates a reference for measuring the angular position of the rotor.<\/div><\/div>
<\/a>Centering<\/strong>
Design of the joint between rotor components to ensure a certain concentricity.<\/div><\/div>
<\/a>Two-plane balancing<\/strong>
Correction of the mass distribution of a rigid rotor in order to limit the dynamic residual imbalance.<\/div><\/div>
<\/a>Two-plane balancing machine<\/strong>
Balancing machine that uses centrifugal force to balance a rotor in two planes.<\/div><\/div><\/div><\/div>