Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M1/00—Testing static or dynamic balance of machines or structures
  • G01M1/30—Compensating imbalance
  • G01M1/36—Compensating imbalance by adjusting position of masses built-in the body to be tested
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
  • B23Q11/00—Accessories fitted to machine tools for keeping tools or parts of the machine in good working condition or for cooling work; Safety devices specially combined with or arranged in, or specially adapted for use in connection with, machine tools
  • B23Q11/0032—Arrangements for preventing or isolating vibrations in parts of the machine
  • B23Q11/0035—Arrangements for preventing or isolating vibrations in parts of the machine by adding or adjusting a mass, e.g. counterweights
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
  • B23Q17/00—Arrangements for observing, indicating or measuring on machine tools
  • B23Q17/12—Arrangements for observing, indicating or measuring on machine tools for indicating or measuring vibration
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B41/00—Component parts such as frames, beds, carriages, headstocks
  • B24B41/04—Headstocks; Working-spindles; Features relating thereto
  • B24B41/042—Balancing mechanisms
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
  • F16F15/32—Correcting- or balancing-weights or equivalent means for balancing rotating bodies, e.g. vehicle wheels
  • F16F15/36—Correcting- or balancing-weights or equivalent means for balancing rotating bodies, e.g. vehicle wheels operating automatically, i.e. where, for a given amount of unbalance, there is movement of masses until balance is achieved

Definitions

• the present invention relates to a system for balancing a structure of a machine tool including a spindle, rotating about a longitudinal axis and carrying a grinding wheel coupled, in a removable way, substantially to a first end of the spindle, the system including a first vibration- detecting sensor at a first transversal section, near the first end of the spindle, a first, automatic, balancing device coupled to the spindle substantially near the grinding wheel, and a processing, display and control unit connected to the first vibration-detecting sensor and to the automatic balancing device for controlling in an automatic way the automatic balancing device on the basis of signals output from the first vibration-detecting sensor.
• the invention also relates to a method for balancing a structure of a machine tool including a spindle defining a longitudinal axis, rotating about it and carrying a grinding wheel coupled, in a removable way, substantially to a first end of the spindle, by means of a system including at least a first vibration detecting sensor and at least a first, automatic, balancing device, the method including the step of automatically controlling the first, automatic, balancing device on the basis of the signals provided by the first vibration-detecting sensor.
• Undesired vibrations are generally present in a grinding machine, and generated by out-of-balance conditions of the grinding wheel due to various possible reasons depending on the grinding wheel itself, like shape and/or constitution defects (inhomogeneity of the materials, concentricity errors between the external abrading surface and the internal centering hole, etc.), inaccurate assembling to the rotating spindle (hence causing the grinding wheel center of gravity to be spaced apart from the axis of rotation) , and, in general, deterioration due to wear and/or splinter occurring during the machining of the workpieces.
• balancing apparatuses or balancers, are coupled to the grinding wheel and comprise movable masses, driven by electric motors that adjust the position of the masses, in the course of the wheel rotation, along radial or angular paths in order to compensate the previously mentioned out- of-balance conditions.
• the driving motors are also part of the apparatus, rotate along with it and the grinding wheel, and are power supplied and controlled by a stationary, external power source, by means of an electric connection, including, for example, a brush collector and slip rings, or by means of a contactless connection, for example of the inductive type.
• the characteristics (like, for example, the amplitude) of the vibrations generated as a consequence of the out-of- balance are picked up by processing the signals provided by an appropriate sensor and displayed, or processed in a proper unit (that often comprises the previously mentioned power supply source, too) for providing suitable balancing signals and for controlling the motors to drive the movable masses .
• a balancing apparatus comprising the previously mentioned characteristics is disclosed in U.S. patent US-A-3698263.
• the automatic balancing of grinding wheels generally takes place in a heuristic way, i.e. on the basis of cycles for displacing the two masses in the balancing device in order to continuously reduce the vibration detected by the sensor until there is obtained its complete elimination or in any case its reduction to acceptable values.
• Patent application DE-A-2345664 describes a method and an associated apparatus for the dynamic balancing of an elongate grinding wheel for a centerless grinding machine, along two transversal sections relative to the longitudinal axis, by means of two devices each including a vibration- detecting sensor and an associated unit with movable masses, each device being arranged at one of the two sections. Processing, power supply and control units are alternately connected to the two balancing devices, for controlling in sequence displacements of the masses of each of the devices on the basis of the signal received by the associated vibration-detecting sensor.
• An object of the present invention is to provide a system and a method for the dynamic balancing of rotating systems, more specifically elongate structures including tools like grinding wheels, that enable to eliminate or reduce to a minimum the unwanted vibrations in a way that is simple, safe and inexpensive.
• figure 1 shows, in simplified form, an application of the system according to the invention, with some details cross-sectioned, in a phase of the method according to the invention
• figure 2 shows, in simplified form, the application of the system of figure 1, in a different phase of the method according to the invention
• figure 3 is a cross-sectional view, with enlarged scale, of a detail of the system of figures 1 and 2, viewed along line III-III of figure 1
• figure 4 is an enlarged scale, perspective view of the detail of figure 3
• figure 5 is a diagram with functional blocks of a balancing method according to the invention.
• Figure 1 illustrates, in extremely simplified and partial form, an elongate rotating structure 1 that defines a longitudinal axis L and includes a shaft or spindle 3 carrying at one end a grinding wheel 5, coupled in a known removable way.
• a grinding machine support 2 for example the wheel- carrier, defines an axis of rotation R and supports the rotating structure 1 in such a way that the longitudinal axis L substantially coincides with the axis of rotation R, and the spindle 3, that is driven in a known way not shown in the figure, can rotate about said axis R.
• a first vibration-detecting sensor 7, for example of the piezoelectric type, is coupled to the support 2 near a first transversal section SI, near the end of shaft 3 where the grinding wheel 5 is coupled to.
• a first, automatic, balancing device 9 is housed in a suitable recess 8 at the end of the spindle 3 near the transversal section Si, and includes a pair of eccentric balancing masses - shown in simplified form and identified by reference numbers 11 and 12 - angularly movable about the longitudinal axis L by means of associated motors, not shown in the figure.
• the power supply for the motors and the controls relating to the angular displacements to be performed by the masses are transmitted to the automatic balancing device 9 by means of an electric connection with a per se known contactless coupling 13, for example of the inductive type, including a stationary transmitter 15 and a rotary receiver 17.
• the receiver 17, also shown in figure 4, is part of the rotating structure 1 and is coupled to the spindle 3, in a recess of the latter, at the end opposite the one carrying the grinding wheel 5, centered relative to the longitudinal axis L.
• the stationary transmitter 15 faces the receiver 17 and is arranged at a limited distance from it.
• a longitudinal recess 14 in spindle 3, with substantially cylindrical cross-section and centered on axis L, houses a cable, for example a spiral cable 16, for electrically connecting the automatic balancing device 9 to the receiver 17. In static conditions, the cable 16 is substantially centered along the longitudinal axis L of the spindle 3.
• a second, manually-operated, balancing device 10 is coupled to the end of spindle 3 opposite the one carrying grinding wheel 5, more specifically it is mechanically coupled to receiver 17.
• the manually-operated device 10, also shown in figures 3 and 4, includes a graduated ring 19 and two displaceable elements or segments 21 and 22 that can be set at known pre-fixed angular positions identified by the graduated ring 19. The locking of the segments 21 and 22 in the desired position and their releasing are manually performed by utilizing suitable tools, according to a per se known procedure.
• a second vibration-detecting sensor 27, for example of the piezoelectric type, is coupled to support 2 near a second transversal section S2 , at the end of shaft 3 where the receiver 17 is coupled to.
• a processing, display and control unit 40 is connected to the first vibration-detecting sensor (7) , to the second vibration-detecting sensor (27) , and to the stationary transmitter unit 15.
• a dummy balancer 29, consisting of a mechanical piece with rotational symmetry, has shape and external dimensions similar to those of the automatic balancing device 9, and is coupled to the spindle 3, housed in recess 8 instead of automatic device 9, in a preliminary phase of the method according to the invention, as hereinafter described and shown in figure 2.
• the mechanical piece or dummy balancer 29 is made, for example, from aluminum and has specific manufacturing features that guarantee the coincidence between the axis of inertia and the geometrical axis of symmetry.
• the functional blocks of the diagram indicate the steps of a balancing method according to the present invention and more specifically: Block 50: the balancing cycle starts;
• Block 51 the grinding wheel 5 and the automatic balancing device 9 are removed from spindle 3 and the dummy balancer 29 is placed in recess 8 at the end of the spindle 3, and is mechanically coupled to the cable 16 (see figure 2) ;
• Block 52 the segments 21 and 22 are placed in known angular positions;
• Block 53 spindle 3 is caused to rotate and unit 40 detects and memorizes the signals provided by the second vibration- detecting sensor 27;
• Block 54 spindle 3 is stopped and at least one of the segments 21 and 22 is displaced to a different known angular position;
• Block 55 spindle 3 is caused to rotate again and the unit 40 detects and memorizes the signals provided by the second vibration-detecting sensor 27;
• Block 56 as the spindle 3 is stopped, depending on the signals detected and memorized at steps 53 and 55, unit 40 processes and displays information relating to angular balance positions of the segments 21 and 22 that enable to balance the assembly including spindle 3 according to the arrangement shown in figure 2;
• Block 57 the segments 21 and 22 are placed in the angular balance positions displayed in unit 40;
• Block 58 the dummy balancer 29 is removed from recess 8 and the automatic balancing device 9 is mounted in its place and coupled to spindle 3, whereto there is also coupled the grinding wheel 5;
• Block 59 spindle 3 is driven into rotation and unit 40 receives the signals of the first vibration-detecting sensor 7 only;
• Block 60 the positions of the masses 11 and 12 are automatically changed in the course of the rotation of spindle 3 by control signals transmitted to the associated motors by unit 40, through the contactless coupling 13;
• Block 61 on the basis of the signal provided by sensor 7, it is detected whether it is necessary to furtherly change the position of the masses 11 and 12; and
• Block 62 the balancing cycle ends.
• a preliminary phase of the balancing cycle according to the present invention is manually carried out - from time to time - in a substantially deterministic way by means of the device 10, on the rotating assembly that includes the spindle 3, the receiver 17 and the dummy balancer 29 in the recess 8, before coupling grinding wheel 5 or after having removed it from spindle 3 (block 51) .
• spindle 3 After having placed the segments 21 and 22 in known angular positions, for example at 180° mutually opposite positions, as shown in figure 3 (block 52) , spindle 3 is driven into rotation and unit 40 detects and memorizes the signals provided by the second vibration-detecting sensor 27 (block 53) . The rotation is stopped and one of the segments, for example segment 21, is placed in a different known position, for example it is displaced by 60° with respect to the previous position (block 54) . Again spindle 3 is driven into rotation and unit 40 detects and memorizes the signals of the second vibration-detecting sensor 27 (block 55) .
• unit 40 processes and displays information (block 56) relating to angular balance positions, i.e. positions at which segments 21 and 22 have to be set in order to achieve the balance condition of the rotating assembly including the spindle 3 and the receiver 17 according to the arrangement shown in figure 2. Thereafter, the segments 21 and 22 are actually placed in the angular balance positions displayed in unit 40 (block 57) .
• the automatic balancing phase of the rotating structure 1 starts, and takes place in a known way, under the control of unit 40 and on the basis of the signals provided by the first vibration-detecting sensor 7 only (blocks 59, 60, 61 and 62) .
• the herein described system and method enable to achieve in an extremely simple and safe way the dynamic balancing of structure 1 including the grinding wheel 5 arranged at the end of the spindle 3, without the need of utilizing additional, expensive and delicate automatic balancers.
• the manually-carried out balancing phase enables to compensate in advance the causes determining the dynamic torque out-of-balance of the structure 1, apart from those due to changes in the shape, structure or arrangement of grinding wheel 5.
• the latter causes are then compensated in a known way - during the rotation of spindle 3 - by means of the single automatic balancing device 9 located in correspondence of the grinding wheel 5.
• the above-mentioned preliminary steps are usually to be carried out just once for a specific rotating assembly including spindle 3 and receiver 17.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• General Engineering & Computer Science (AREA)
• General Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Aviation & Aerospace Engineering (AREA)
• Testing Of Balance (AREA)
• Constituent Portions Of Griding Lathes, Driving, Sensing And Control (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=11440162

Family Applications (1)

Country Status (3)

Cited By (1)

Citations (8)

• 2002
  • 2002-05-23 IT IT2002BO000316A patent/ITBO20020316A1/it unknown
  • 2002-12-27 WO PCT/EP2002/014768 patent/WO2003100374A1/en not_active Application Discontinuation
  • 2002-12-27 AU AU2002358798A patent/AU2002358798A1/en not_active Abandoned

Patent Citations (8)

Non-Patent Citations (3)

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