Patent Publication Number: US-2022234156-A1

Title: Cutting apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a cutting apparatus for cutting a workpiece with a cutting blade. 
     Description of the Related Art 
     Wafers with a plurality of devices, typically semiconductor integrated circuits, formed thereon are divided to produce a plurality of device chips that each include the device. After a plurality of device chips are mounted on a predetermined board, the device chips on the board are covered with a sealing material, e.g., molded resin, so that a package board is fabricated. The package board is divided to produce package devices each including one or more of the device chips. The package devices will be incorporated in various electronic appliances such as mobile phones and personal computers. 
     A cutting apparatus is used to divide a workpiece such as a wafer or a package board. The cutting apparatus includes a chuck table for holding the workpiece thereon and a cutting unit for cutting the workpiece on the chuck table. The cutting unit includes a spindle, a mount flange fixed to the distal end of the spindle, and an annular cutting blade for cutting the workpiece, the cutting blade being mounted on the mount flange. 
     The mount flange includes a boss inserted into an opening defined centrally in the cutting blade. The cutting blade is secured to the mount flange by a nut threaded and tightened over the boss that has been inserted into the opening in the cutting blade. When the spindle is rotated about its central axis with the cutting blade mounted on the mount flange, the cutting blade is rotated about its central axis. The rotating cutting blade is caused to cut into the workpiece held on the chuck table, the workpiece is cut and divided. 
     The cutting blade is progressively worn as it cuts workpieces one after another and is eventually replaced with a new one when necessary. For replacing the worn cutting blade, the nut is loosened and detached from the boss, and the cutting blade is dismounted from the mount flange. Then, a replacement cutting blade, e.g., an unused cutting blade, is mounted on the mount flange and thereafter secured to the mount flange by threading and tightening the nut over the boss. 
     It has been customary to replace worn cutting blades manually. However, the manual replacement process is tedious and time-consuming, and has also proven disadvantageous in that an operator may drop cutting blades or the nut or may happen to hit them on the cutting apparatus. Consequently, in order to replace cutting blades without a manual replacement process, there has been proposed a cutting apparatus incorporating therein a changing device for automatically replacing a cutting blade on a cutting unit, i.e., a spindle unit (see, for example, JP 2007-98536A). 
     The changing device of the cutting apparatus includes a cutting blade mounting and dismounting mechanism for mounting and dismounting cutting blades and a nut mounting and dismounting mechanism for mounting and dismounting a nut for securing a cutting blade to a cutting unit. The cutting blade mounting and dismounting mechanism includes a first holder for gripping a cutting blade mounted on a spindle and a second holder for gripping a replacement cutting blade with which to replace the cutting blade mounted on the spindle. 
     SUMMARY OF THE INVENTION 
     In the cutting apparatus, the second holder of the cutting blade mounting and dismounting mechanism grips a replacement cutting blade housed in a blade stocker of the cutting apparatus and mounts the replacement cutting blade on a spindle. The blade stocker has a shaft to be inserted into an opening in the replacement cutting blade. After the replacement cutting blade is manually removed from a blade case where it has been housed, the replacement cutting blade is manually placed on the shaft and housed in the blade stocker. 
     However, when the operator manually removes the replacement cutting blade from the blade case and manually place the replacement cutting blade into the blade stocker, the operator may drop the replacement cutting blade or a nut or may happen to hit them on the cutting apparatus. 
     It is therefore an object of the present invention to provide a cutting apparatus that makes it unnecessary for the operator to manually remove a cutting blade from a blade case. 
     In accordance with an aspect of the present invention, there is provided a cutting apparatus including a cutting unit including a spindle as a rotational shaft and a mount flange for mounting a cutting blade thereon, the mount flange being fixed to a distal end of the spindle, a support unit for supporting a cutting blade housed in a blade case, the support unit including a blade case support for supporting the blade case for housing the cutting blade therein, a changing mechanism for dismounting a cutting blade that has been mounted on the mount flange from the mount flange and mounting the cutting blade that has been supported on the support unit on the mount flange, and a moving mechanism for moving the changing mechanism between a changing position in which the cutting blade is able to be mounted on and dismounted from the mount flange, a blade transfer position in which the cutting blade is able to be transferred to and from the support unit, and a retracted position spaced from the changing position and the blade transfer position. 
     According to the aspect of the present invention, the support unit may further include a rotating mechanism for rotating the blade case support and have a plurality of the blade case supports for supporting respective blade cases, the blade case supports being arrayed along directions in which the blade case supports are rotatable by the rotating mechanism. 
     According to the aspect of the present invention, the mount flange may have a fixed mount fixed to the spindle and a holder flange mounted on the fixed mount with the cutting blade sandwiched and secured between the fixed mount and the holder flange, the support unit may further include a holder flange support for supporting the holder flange, and the changing mechanism may mount the cutting blade together with the holder flange on the fixed mount and dismount the cutting blade together with the holder flange from the fixed mount. 
     According to the aspect of the present invention, the blade case may have a storage casing for storing the cutting blade and a lid for closing the storage casing, and the cutting apparatus may further include an opening and closing unit for opening and closing the lid of the blade case. 
     According to the aspect of the present invention, the cutting apparatus may further include a table for holding a dressing board for use in dressing the cutting blade or an inspection board for being cut by the cutting blade to form an inspection groove therein. The support unit may further include a board support for supporting the dressing board or the inspection board. The moving mechanism may move the changing mechanism between a board transfer position in which the dressing board or the inspection board is able to be transferred to and from the support unit, a loading and unloading position in which the dressing board or the inspection board is able to be loaded to and unloaded from the table, the changing position, the blade transfer position, and the retracted position, and the changing mechanism may remove the dressing board or the inspection board from the table on which the dressing board or the inspection board has been held, and place, on the table, the dressing board or the inspection board that has been supported on the support unit. 
     According to the aspect of the present invention, the cutting apparatus may further include a reading unit for reading identification marks, and a blade case determining unit for determining whether information acquired when an identification mark attached to the cutting blade is read by the reading unit and information acquired when an identification mark attached to the blade case is read by the reading unit correspond to each other or not. 
     According to the aspect of the present invention, the cutting apparatus may further include a reading unit for reading identification marks, and a board determining unit for determining whether information acquired when an identification mark attached to the cutting blade is read by the reading unit and information acquired when an identification mark attached to the dressing board or the inspection board is read by the reading unit correspond to each other or not. 
     The cutting apparatus according to the aspect of the present invention includes a support unit for supporting a cutting blade housed in a blade case, a cutting unit including a mount flange on which the cutting blade is to be mounted, a changing mechanism for mounting a cutting blade that has been supported on a support unit on the mount flange, and a moving mechanism for moving the changing mechanism. 
     Consequently, by supporting a cutting blade housed in a blade case on the support unit and moving the changing mechanism with the moving mechanism, it is possible to change the cutting blade on the cutting unit. In other words, the cutting apparatus according to the aspect of the present invention makes it unnecessary to manually remove the cutting blade from the blade case as in the existing technology. 
     The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing a preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a cutting apparatus according to a preferred embodiment of the present invention; 
         FIG. 2  is an exploded perspective view of a cutting unit of the cutting apparatus, with a hub-type cutting blade mounted thereon; 
         FIG. 3  is an exploded perspective view of the cutting unit with a washer-type cutting blade mounted thereon; 
         FIG. 4  is a perspective view of a changer unit of the cutting apparatus; 
         FIG. 5  is a perspective view of the changer unit with a changing device disposed in a changing position; 
         FIG. 6  is a perspective view of the changing device; 
         FIG. 7A  is a side elevational view of the changing device; 
         FIG. 7B  is a front elevational view of the changing device; 
         FIG. 8A  is a front elevational view of a holder of the changing device; 
         FIG. 8B  is a cross-sectional view of the holder; 
         FIG. 9A  is a cross-sectional view of the holder as it is holding a hub-type cutting blade; 
         FIG. 9B  is a cross-sectional view of the holder as it is holding a washer-type cutting blade; 
         FIG. 10A  is a plan view of a support unit in which replacement cutting blades are supported and stored; 
         FIG. 10B  is a perspective view of a blade case; 
         FIG. 11A  is a plan view of a hub-type cutting blade with an identification mark attached thereto; 
         FIG. 11B  is a plan view of a washer-type cutting blade with an identification mark attached thereto; 
         FIG. 11C  is a plan view of a dressing board or an inspection board with an identification mark attached thereto; 
         FIG. 12A  is a schematic view of the changing device in a replacement cutting blade holding step; 
         FIG. 12B  is a schematic view of the changing device in a nut removing step; 
         FIG. 12C  is a schematic view of the changing device in a first retracting step; 
         FIG. 12D  is a schematic view of the changing device in a used cutting blade holding step; 
         FIG. 13A  is a schematic view of the changing device in a second retracting step; 
         FIG. 13B  is a schematic view of the changing device in a cutting blade mounting step; 
         FIG. 13C  is a schematic view of the changing device in a third retracting step; 
         FIG. 13D  is a schematic view of the changing device in a nut mounting step; 
         FIG. 14A  is a perspective view of the holder as it is holding a square dressing board; 
         FIG. 14B  is a perspective view of the holder as it is holding an elongate rectangular dressing board; 
         FIG. 15A  is a schematic view of the changing device in a replacement board holding step; 
         FIG. 15B  is a schematic view of the changing device in a used board holding step; 
         FIG. 15C  is a schematic view of the changing device in a retracting step; 
         FIG. 15D  is a schematic view of the changing device in a placing step; 
         FIG. 16  is a perspective view of a cutting apparatus including a support unit according to a modification; 
         FIG. 17  is a perspective view of the support unit including a rotatable support plate; 
         FIG. 18  is a perspective view of an opening and closing unit; 
         FIG. 19A  is a perspective view illustrating the manner in which a blade case placed on a blade case support is secured by a holding mechanism; 
         FIG. 19B  is a perspective view illustrating the manner in which a lid of the blade case is pushed upwardly by an unlocking mechanism; 
         FIG. 20A  is a perspective view illustrating the manner in which the lid of the blade case is further opened by a pushing mechanism; and 
         FIG. 20B  is a perspective view illustrating the manner in which the lid of the blade case is closed by a locking mechanism. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A preferred embodiment of the present invention will be described hereinbelow with reference to the accompanying drawings.  FIG. 1  illustrates in perspective a cutting apparatus  2  according to the preferred embodiment of the present invention. In  FIG. 1 , X-axis directions, i.e., processing feed directions, first horizontal directions, or forward and rearward directions, and Y-axis directions, i.e., indexing feed directions, second horizontal directions, or leftward and rightward directions, extend perpendicularly to each other. Z-axis directions, i.e., vertical directions, upward and downward directions, or heightwise directions, expend perpendicularly to the X-axis directions and the Y-axis directions. 
     The cutting apparatus  2  includes a base  4  supporting or housing various components of the cutting apparatus  2 . An elevator  6  having a lifting and lowering stage  6   a  is disposed on one side of a front corner of the base  4 . The elevator  6  includes a lifting and lowering mechanism, not depicted, for lifting and lowering the lifting and lowering stage  6   a  along the Z-axis directions. 
     On the lifting and lowering stage  6   a  of the elevator  6 , there are disposed a container  8  for containing various tools (parts, consumables, etc.) used on the cutting apparatus  2  and a cassette  10  for housing a plurality of workpieces  11  to be cut by the cutting apparatus  2 . In  FIG. 1 , the container  8  is illustrated as being placed on the lifting and lowering stage  6   a , and the cassette  10  is illustrated as being placed on the container  8 . The tools to be placed in the container  8  will be described in detail later. 
     The cassette  10  has a pair of side walls that are spaced from each other and face each other along the Y-axis directions. A plurality of guide rails  10   a  that are spaced at predetermined intervals along the heightwise directions of the cassette  10  are fixed to each of confronting inner surfaces of the side walls of the cassette  10 . Frame units, i.e., workpiece units,  17  that include the respective workpieces  11  are supported by respective pairs of the guide rails  10   a  that are positioned at respective vertical positions in the cassette  10 . 
     Each of the workpieces  11  is a disk-shaped wafer made of a semiconductor material such as silicon, for example. Each of the workpieces  11  has a face side, i.e., an upper surface, having a plurality of areas demarcated by a grid of projected dicing lines or streets established thereon. Devices such as integrated circuits (ICs) or large-scale-integration (LSI) circuits are formed on the face sides or upper surfaces of the respective areas of each of the workpieces  11 . Each of the workpieces  11  will be cut and divided along the projected dicing lines into a plurality of device chips that each include the device. 
     There are no limitations on the material, shape, structure, size, and so on of the workpieces  11 . The workpieces  11  may be wafers made of a semiconductor material other than silicon, such as GaAs, InP, GaN, or Sic, glass, ceramic, resin, metal, or the like, for example. There are no limitations on the kind, number, shape, structure, size, layout, or the like of the devices on the workpieces  11 , and the workpieces  11  may be devoid of devices. Further, the workpieces  11  may be package boards such as chip-size-package (CSP) boards or quad-flat-non-leaded-package (QFN) boards. 
     A circular tape, or a dicing tape,  13  is affixed to the reverse side, i.e., the lower surface, of each of the workpiece  11 . The tape  13  is larger in diameter than the workpiece  11 . The tape  13  may include a sheet having a circular film base and an adhesive layer, i.e., a glue layer, disposed on the film base. For example, the film base is made of a resin such as polyolefin, polyvinyl chloride, or polyethylene terephthalate, and the adhesive layer is made of an epoxy, acrylic, or rubber adhesive or the like. Alternatively, the adhesive layer may be made of an ultraviolet-curable resin that can be cured upon exposure to ultraviolet radiation. 
     The tape  13  has an outer circumferential portion affixed to an annular frame  15  made of metal or the like and having a circular opening defined centrally therein. The opening in the frame  15  is larger in diameter than the workpiece  11 , which is disposed within the opening in the frame  15 . 
     When the tape  13  is affixed to the workpiece  11  and the frame  15 , the workpiece  11  is supported on the frame  15  by the tape  13 , thereby making up a frame unit  17  including the workpiece  11 , the tape  13 , and the frame  15 . One or more frame units  17  are housed in the cassette  10 . 
     The base  4  has an opening  4   a  defined in a region of an upper surface thereof that is positioned adjacent to the elevator  6  along the X-axis directions. The opening  4   a  accommodates therein a cleaning unit  12  for cleaning a workpiece  11 . The cleaning unit  12  includes a spinner table  14  for holding the workpiece  11  thereon and a nozzle, not depicted, disposed above the spinner table  14  for supplying a cleaning fluid such as pure water to the workpiece  11  held on the spinner table  14 . 
     The spinner table  14  is connected to a rotary actuator, not depicted, such as an electric motor for rotating the spinner table  14  about a rotational axis generally parallel to the Z-axis directions. While the workpiece  11  is being held on the spinner table  14 , the spinner table  14  is rotated about the rotational axis by the rotary actuator and the cleaning fluid is supplied from the nozzle to the workpiece  11  on the spinner table  14 , thereby cleaning the workpiece  11 . The cleaning fluid may alternatively be a gas-liquid fluid made up of a mixture of a liquid such as pure water and air. 
     A pair of guide rails  16  extending along the X-axis directions for holding a frame unit  17  thereon are disposed above the cleaning unit  12 . The guide rails  16  are operatively connected to a moving mechanism, not depicted, for moving the guide rails  16  away from and toward each other along the Y-axis directions. The moving mechanism can move the guide rails  16  toward each other to sandwich the frame unit  17  on the guide rails  16 , thereby positioning the frame unit  17  along the Y-axis directions. 
     The base  4  also has a rectangular opening  4   b  defined in another region of the upper surface thereof that is positioned adjacent to the guide rails  16  along the Y-axis directions. The opening  4   b  has its longitudinal axis oriented along the X-axis directions. The opening  4   b  accommodates therein a table cover  18  shaped as a flat plate. Dust-proof and drip-proof covers  20  in the form of bellows that extensible and contractible in the X-axis directions are disposed on both sides of the table cover  18  and joined thereto in the X-axis directions. 
     A chuck table, i.e., a holding table,  22  for holding a workpiece  11 , etc. is disposed on the table cover  18 . The chuck table  22  has an upper surface providing a flat holding surface for holding the workpiece  11 , etc. thereon. The chuck table  22  is surrounded by a plurality of clamps  24  for gripping the frame  15  that supports the workpiece  11  to secure the frame  15  in position on the chuck table  22 . 
     The chuck table  22  includes a cylindrical frame, not depicted, made of metal such as stainless steel, for example. The frame has a circular recess defined centrally in an upper surface thereof. A disk-shaped porous member made of a porous material such as porous ceramic is fitted in the circular recess in the frame. The holding surface of the chuck table  22  that is mainly provided by the porous member is held in fluid communication with a suction source, not depicted, such as an ejector via a fluid channel, not depicted, defined in the porous member and the chuck table  22 , a valve, not depicted, etc. 
     A frame unit  17  is placed on the chuck table  22  such that the face side of the workpiece  11  is exposed upwardly and the reverse side thereof, i.e., the tape  13  side, faces the holding surface of the chuck table  22 . The frame  15  is gripped and fixed in position by the clamps  24 . Then, a negative pressure from the suction source is applied to the holding surface of the chuck table  22 , attracting and holding the workpiece  11  on the chuck table  22  under suction with the tape  13  interposed therebetween. 
     A pair of sub-tables, i.e., holding tables,  26  are mounted on the table cover  18  adjacent to the chuck table  22 . The sub-tables  26  are spaced from each other along the Y-axis directions behind the chuck table  22 . 
     The sub-tables  26  have respective flat upper surfaces providing holding surfaces for holding plate-shaped members to be used for setting up, inspecting, and assessing a cutting process. For example, the holding surfaces of the sub-tables  26  are of a rectangular shape and are held in fluid communication with a suction source, not depicted, such as an ejector via fluid channels, not depicted, defined in the sub-tables  26 , valves, not depicted, etc. Specifically, the sub-tables  26  hold thereon a dressing board  19 , an inspection board (see  FIG. 10A , etc.), etc. to be described later. 
     A moving unit, not depicted, and a rotary actuator, not depicted, are disposed in the base  4  below the table cover  18 . The moving unit includes a ball-screw-type moving mechanism or the like for moving the chuck table  22  and the sub-tables  26  as well as the table cover  18  along the X-axis directions. The rotary actuator includes an electric motor or the like for rotating the chuck table  22  about a rotational axis generally parallel to the Z-axis directions. 
     The opening  4   b  has a front region positioned adjacent to the opening  4   a  and providing a delivery region where a workpiece  11  can be loaded to and unloaded from the chuck table  22 . The opening  4   b  also has a rear region positioned behind the delivery region and providing a processing region where a workpiece  11  can be processed, i.e., cut. The moving unit moves the chuck table  22  and the sub-tables  26  as well as the table cover  18  along the X-axis directions to position the chuck table  22  and the sub-tables  26  selectively in the delivery region and the processing region. 
     A processing chamber cover  28  is disposed above the processing region to define a space, i.e., a processing chamber, where a workpiece  11  on the chuck table  22  is processed, i.e., cut. In  FIG. 1 , the processing chamber cover  28  has its outline indicated by the two-dot-and-dash lines. The processing chamber cover  28  is made of metal or the like and shaped as a rectangular parallelepiped, and is disposed in covering relation to the processing region. The processing chamber cover  28  has an inlet/outlet port, i.e., an opening,  28   a  defined in a front side wall thereof facing the delivery region, for allowing a changing device  100  (see  FIG. 6 , for example), to be described later, to pass therethrough. 
     The processing chamber cover  28  houses therein a pair of cutting units  30  for cutting a workpiece  11 . The cutting units  30  cut the workpiece  11  by causing respective annular cutting blades to rotate and cut into the workpiece  11 . A hub-type cutting blade  36  (see  FIG. 2 ), for example, is mounted on each of the cutting units  30 . 
       FIG. 2  illustrates in exploded perspective one of the cutting units  30  each with the hub-type cutting blade  36  mounted thereon. The cutting units  30  are identical in structure to each other, and hence one of them will be described hereinbelow. The cutting unit  30  includes a tubular housing  32  and a cylindrical spindle  34  rotatably housed as a rotational shaft in the housing  32  and extending along the Y-axis directions. 
     The spindle  34  has a distal end portion, i.e., one end portion, exposed out of the housing  32 . The distal end portion of the spindle  34  has an axial, internally threaded hole  34   a  defined therein that is open at an end face thereof. The spindle  34  has a proximal end portion, i.e., another end portion, connected to a rotary actuator such as an electric motor. The hub-type cutting blade  36 , which is of an annular shape, is mounted on the exposed distal end portion of the spindle  34 . The cutting blade  36  mounted on the distal end portion of the spindle  34  is rotatable about its own central axis by the rotational power transmitted from the rotary actuator through the spindle  34 . 
     The cutting blade  36  includes an annular base  38  made of metal or the like and an annular cutting edge  40  disposed on and extending along an outer circumferential edge portion of the base  38 . The cutting blade  36  has a circular opening  36   a  that is defined centrally therein, i.e., in the base  38  and that extends thicknesswise therethrough, i.e., through the base  38 . 
     The base  38  has a face side, i.e., a first surface,  38   a  and a reverse side, i.e., a second surface,  38   b  that lie generally parallel to each other. The face side  38   a  of the base  38  provides an annular holdable surface that is to be held when the cutting blade  36  is mounted and dismounted. The cutting edge  40  is formed on an outer circumferential edge portion of the reverse side  38   b  of the base  38 . For example, the cutting edge  40  is made of an electroformed grindstone including abrasive grains of diamond or the like that are secured together by a binder such as a nickel plating layer. 
     A mount flange  42  on which the cutting blade  36  is to be mounted is fixed to the distal end portion of the spindle  34 . The mount flange  42  includes a disk-shaped flange member  44  supporting the cutting blade  36  thereon and a cylindrical boss, i.e., a support shaft,  46  protruding centrally from a surface  44   a  of the flange member  44  that faces the cutting blade  36 . The mount flange  42  has a through hole  42   a  defined therein that extends axially through a central portion of the flange member  44  and a central portion of the boss  46 . 
     The flange member  44  includes an annular land  44   b  extending on an outer circumferential edge portion thereof and protruding axially from the surface  44   a . The land  44   b  has a distal end face lying generally parallel to the surface  44   a  and providing an annular support surface  44   c  that supports the cutting blade  36  thereon. 
     The boss  46  has a distal end portion having an externally threaded outer circumferential surface  46   a  having threads and grooves. An annular nut  48  is to be threaded over the externally threaded outer circumferential surface  46   a  of the boss  46 . The nut  48  has a circular opening  48   a  that is defined centrally therein and that extends thicknesswise through the nut  48 . The opening  48   a  is essentially equal in diameter to the boss  46  and defined by an internally threaded inner circumferential surface having threads and grooves that are complementary to those of the externally threaded outer circumferential surface  46   a  of the boss  46 . The nut  48  also has a plurality of through holes  48   b  defined therein that extend thicknesswise through the nut  48  and angularly spaced at substantially equal intervals circumferentially along the nut  48 . 
     The cutting blade  36  is fixedly mounted on the mount flange  42  as follows: A screw  50  is inserted through the through hole  42   a  in the mount flange  42  and threaded and tightened into the internally threaded hole  34   a  in the spindle  34 , thereby securing the mount flange  42  to the distal end portion of the spindle  34 . Then, the cutting blade  36  is placed on the boss  46  of the mount flange  42  such that the boss  46  is inserted in the opening  36   a  in the cutting blade  36 , so that the cutting blade  36  is mounted on the mount flange  42 . Thereafter, the nut  48  is threaded over the externally threaded outer circumferential surface  46   a  of the boss  46  to sandwich the cutting blade  36  between the support surface  44   c  of the flange member  44  and the nut  48 . The cutting blade  36  is now fixedly mounted on the mount flange  42 . 
     A washer-type cutting blade  52  (see  FIG. 3 ) may alternatively be mounted on the cutting unit  30 .  FIG. 3  illustrates in exploded perspective the cutting unit  30  with the washer-type cutting blade  52  mounted thereon. 
     The cutting blade  52  includes an annular cutting edge made of a grindstone including abrasive grains that are secured together by a binder such as a metal bond, a resin bond, or a vitrified bond. The cutting blade  52  has a circular opening  52   a  that is defined centrally therein and that extends thicknesswise therethrough. 
     A mount flange  54  on which the cutting blade  52  is to be mounted is fixed to the distal end portion of the spindle  34 . The mount flange  54  includes a fixed mount  56  to be fixed to the distal end portion of the spindle  34  and a holder flange  62  for holding the cutting blade  52  that is mounted on the fixed mount  56 . 
     The fixed mount  56  includes a disk-shaped flange member  58  supporting the cutting blade  52  thereon and a cylindrical boss, i.e., a support shaft,  60  protruding centrally from a surface  58   a  of the flange member  58  that faces the cutting blade  52 . The fixed mount  56  has a through hole  56   a  defined therein that extends axially through a central portion of the flange member  58  and a central portion of the boss  60 . The fixed mount  56  also has an annular rest  56   b  disposed in the through hole  56   a  for supporting a washer  66  to be described later. 
     The flange member  58  includes an annular land  58   b  extending on an outer circumferential edge portion thereof and protruding axially from the surface  58   a . The land  58   b  has a distal end face lying generally parallel to the surface  58   a  and providing an annular support surface  58   c  that supports the cutting blade  52  thereon. 
     The boss  60  includes an annular first boss member, i.e., a first support shaft,  60   a  protruding axially from the surface  58   a  of the flange member  58 , an annular second boss member, i.e., a second support shaft,  60   b  protruding axially from the distal end of the first boss member  60   a , and an annular third boss member, i.e., a third support shaft,  60   c  protruding axially from the distal end of the second boss member  60   b . The second boss member  60   b  is smaller in diameter than the first boss member  60   a , and the third boss member  60   c  is smaller in diameter than the second boss member  60   b . The first boss member  60   a , the second boss member  60   b , and the third boss member  60   c  are concentric with each other. 
     The holder flange  62  is mounted on the fixed mount  56 . The holder flange  62  is an annular component made of metal or the like and has a face side, i.e., a first surface,  62   a  and a reverse side, i.e., a second surface,  62   b  that lie generally parallel to each other. The face side  62   a  of the holder flange  62  provides an annular holdable surface that is to be held when the holder flange  62  is mounted and dismounted. The reverse side  62   b  of the holder flange  62  provides an annular holding surface for supporting the cutting blade  52 . 
     The holder flange  62  has a circular opening  62   c  that is defined centrally therein and that extends axially therethrough from the face side  62   a  to the reverse side  62   b  of the holder flange  62 . The holder flange  62  also has a plurality of through holes  62   d  that is defined in an annular region thereof between the outer circumferential edge thereof and the opening  62   c  and that extends axially therethrough from the face side  62   a  to the reverse side  62   b  of the holder flange  62 . The through holes  62   d  are angularly spaced at substantially equal intervals circumferentially along the holder flange  62 . 
     The boss  60  of the fixed mount  56  has a distal end portion having an externally threaded outer circumferential surface  60   d  having threads and grooves. An annular nut  64  is to be threaded over the externally threaded outer circumferential surface  60   d  of the boss  60 . The nut  64  has a circular opening  64   a  that is defined centrally therein and that extends thicknesswise through the nut  64 . The opening  64   a  is essentially equal in diameter to the third boss member  60   c  and defined by an internally threaded inner circumferential surface having threads and grooves that are complementary to those of the externally threaded outer circumferential surface  60   d  of the boss  60 . The nut  64  also has a plurality of through holes  64   b  defined therein that extend thicknesswise through the nut  64  and angularly spaced at substantially equal intervals circumferentially along the nut  64 . 
     The cutting blade  36  is fixedly mounted on the mount flange  54  as follows: The fixed mount  56  is mounted on the spindle  34  by a screw  68 . Specifically, the washer  66  is placed axially against the rest  56   b  of the fixed mount  56 . Then, the screw  68  is inserted through the washer  66  and the through hole  56   a  in the fixed mount  56  and threaded and tightened into the internally threaded hole  34   a  in the spindle  34 , thereby securing the fixed mount  56  to the distal end portion of the spindle  34 . 
     The cutting blade  52  and the holder flange  62  are successively placed on the boss  60  such that the boss  60  is inserted in the opening  52   a  in the cutting blade  52  and the opening  62   c  of the holder flange  62 . The cutting blade  52  and the holder flange  62  are thus mounted on the fixed mount  56  successively in the order named. The reverse side  62   b  of the holder flange  62  has an annular ridge, not depicted, protruding axially therefrom. The annular ridge has an outer wall surface, i.e., an outer circumferential surface, that is slightly smaller in diameter than the opening  52   a  in the cutting blade  52 , for example, and also has an inner wall surface, i.e., an inner circumferential surface, that is slightly larger in diameter than the outer circumferential surface of the first boss member  60   a , for example. 
     The ridge of the holder flange  62  is fitted in the opening  52   a  in the cutting blade  52 . The holder flange  62  and the cutting blade  52  are positioned with respect to each other by the ridge fitted in the opening  52   a . The first boss member  60   a  is fitted against the inner wall surface of the ridge of the holder flange  62 , and the second boss member  60   b  is fitted in the opening  62   c  in the holder flange  62 . 
     Then, the nut  64  is threaded and tightened over the externally threaded outer circumferential surface  60   d  of the third boss member  60   c , fixing the cutting blade  36  and the holder flange  62  to the fixed mount  56 . The cutting blade  36  is thus sandwiched between the support surface  58   c  of the flange member  58  and the reverse side  62   b  of the holder flange  62  and fixedly mounted on the mount flange  54 . 
     As described above, the hub-type cutting blade  36  or the washer-type cutting blade  52  is mounted on each of the cutting units  30  illustrated in  FIG. 1 . The hub-type cutting blades  36  or the washer-type cutting blades  52  mounted respectively on the cutting units  30  are disposed in facing relation to each other. 
     Image capturing units, i.e., reading units,  70  (see  FIG. 1 ) for capturing images of a workpiece  11 , etc. held on the chuck table  22  are mounted respectively on the cutting units  30 . Each of the image capturing units  70  includes, for example, a visible-light camera including an image capturing device for generating electric signals in response to visible light applied thereto, an infrared-ray camera including an image capturing device for generating electric signals in response to infrared radiation applied thereto, or the like. The workpiece  11  on the chuck table  22  and the cutting units  30  are positioned with respect to each other on the basis of the images generated by the image capturing units  70 . 
     As illustrated in  FIG. 1 , a first delivery unit  72  for delivering workpieces  11  is disposed above the base  4 . The first delivery unit  72  includes an air cylinder having a rod telescopically movable vertically along the Z-axis directions. A moving mechanism, not depicted, for moving the first delivery unit  72  along the X-axis directions and the Y-axis directions is connected to an upper portion of the air cylinder. The rod of the air cylinder has a lower end fixed to a holding unit  72   a  for holding the frame  15  of a frame unit  17 . For example, the holding unit  72   a  has a plurality of suction pads for holding under suction the upper surface of the frame  15  of the frame unit  17 . The holding unit  72   a  includes, on an end thereof closer to the elevator  6 , a gripping mechanism  72   b  for gripping an end of the frame  15  of the frame unit  17 . 
     A second delivery unit  74  for delivering workpieces  11  is disposed above the holding unit  72   a  of the first delivery unit  72 . The second delivery unit  74  includes an air cylinder having a rod telescopically movable vertically along the Z-axis directions. A moving mechanism, not depicted, for moving the second delivery unit  74  along the Y-axis directions is connected to an upper portion of the air cylinder. 
     The rod of the air cylinder has a lower end fixed to a holding unit  74   a  for holding the frame  15  of a frame unit  17 . The holding unit  74   a  is structurally identical to the holding unit  72   a  of the first delivery unit  72  and hence will not be described in detail below. 
     A changer unit  76  for changing cutting blades  36 , cutting blades  52 , or the like on the cutting units  30  is mounted on the base  4  laterally of the chuck table  22 . The structural details of the changer unit  76  will be described in detail later. 
     A plate-shaped cover  78  is disposed on an edge of the base  4  that faces the changer unit  76 . The cover  78  has an end portion connected to the base  4  by hinges  80  and hence can be turned about the hinges  80 . 
     When a workpiece  11  is processed by the cutting units  30 , the cover  78  is erected along the Z-axis directions, i.e., is in an open state, as indicated by the solid lines in  FIG. 1 . On the other hand, when a cutting blade  36  or a cutting blade  52  is changed by the changer unit  76 , the cover  78  lies along the X-axis directions and the Y-axis directions, i.e., is in a closed state, as indicated by the two-dot-and-dash lines in  FIG. 1 . 
     The components of the cutting apparatus  2 , i.e., the elevator  6 , the cleaning unit  12 , the guide rails  16 , the chuck table  22 , the clamps  24 , the sub-tables  26 , the cutting units  30 , the image capturing units  70 , the first delivery unit  70 , the second delivery unit  74 , the changer unit  76 , etc., are electrically connected to a control unit, i.e., a controller,  82 . The control unit  82  generates control signals for controlling operation of the components of the cutting apparatus  2 . 
     The control unit  82  includes a computer, for example, and includes a processing unit, i.e., a blade case determining unit or a board determining unit,  82   a  for performing various processing operations, i.e., arithmetic operations or the like, required to operate the cutting apparatus  2 , and a storage unit  82   b  for storing various pieces of information, i.e., data, programs, etc., used in the processing by the processing unit  82   a . The processing unit  82   a  includes a processor such as a central processing unit (CPU). The storage unit  82   b  includes various memories acting as a main storage device, an auxiliary storage device, etc. 
     The cutting apparatus  2  constructed as described above operates to process, i.e., cut, a workpiece  11 . For processing the workpiece  11 , a frame unit  17  including the workpiece  11  to be processed is housed in the cassette  10 . Then, the cassette  10  that houses the frame unit  17  is placed on the lifting and lowering stage  6   a  of the elevator  6 . 
     The frame unit  17  housed in the cassette  10  is unloaded from the cassette  10  by the first delivery unit  72 . Specifically, while the gripping mechanism  72   b  is gripping an end of the frame  15  of the frame unit  17 , the first delivery unit  72  moves away from the cassette  10  along one of the X-axis directions. The frame unit  17  is thus pulled out of the cassette  10  and placed onto the guide rails  16 . The frame unit  17  is sandwiched between the guide rails  16  and positioned in place. 
     Then, the first delivery unit  72  holds the upper surface of the frame  15  with the holding unit  72   a , and delivers the frame unit  17  onto the chuck table  22  that is positioned in the delivery region. The chuck table  22  then moves from the delivery region to the processing region while holding the reverse side, i.e., the tape  13  side, of the workpiece  11  under suction. The workpiece  11  is now placed in the processing chamber cover  28 . 
     After the workpiece  11  and the cutting units  30  have been positioned with respect to each other on the basis of images captured by the image capturing units  70 , the workpiece  11  is cut by the cutting units  30 . For example, the workpiece  11  is cut along the projected dicing lines and divided into a plurality of device chips. 
     When the cutting process is completed, the chuck table  22  moves to the delivery region. The second delivery unit  74  holds the upper surface of the frame  15  with the holding unit  74   a  and delivers the frame unit  17  from the chuck table  22  to the cleaning unit  12 . The cleaning unit  12  then cleans the workpiece  11 . 
     When the cleaning of the workpiece  11  is completed, the first delivery unit  72  holds the frame  15  with the holding unit  72   a  and delivers the frame unit  17  onto the guide rails  16 . The frame unit  17  is sandwiched between the guide rails  16  and positioned in place. Thereafter, while the gripping mechanism  72   b  is gripping the frame  15 , the first delivery unit  72  moves toward the cassette  10  and then places the frame unit  17  into the cassette  10 . 
     The storage unit  82   b  of the control unit  82  stores programs descriptive of the above sequence of operation of the cutting apparatus  2 . When an operator of the cutting apparatus  2  instructs the cutting apparatus  2  to process the workpiece  11 , the processing unit  82   a  reads the programs from the storage unit  82   b  and successively generates control signals for controlling operation of the components of the cutting apparatus  2 . 
     The cutting blades  36  or the cutting blades  52  mounted on the cutting units  30  are progressively worn as they cut workpieces  11  one after another. Therefore, the cutting blades  36  or the cutting blades  52  are replaced with cutting blades when necessary. The cutting apparatus  2  automatically changes the cutting blades  36  or the cutting blades  52  with the changer unit  76 . 
       FIG. 4  illustrates the changer unit  76  in perspective. As illustrated in  FIG. 4 , the changer unit  76  includes a changing device, i.e., a changing mechanism,  100  for changing cutting blades  36  or cutting blades  52  and a moving unit, i.e., a moving mechanism,  84  for moving the changing device  100 . The moving unit  84  includes a lifting and lowering mechanism  86  for moving the changing device  100  along the Z-axis directions and an articulated arm  90  coupled to the lifting and lowering mechanism  86  for moving the changing device  100  along directions, i.e., horizontal directions, parallel to the X-axis directions and the Y-axis directions. 
     The lifting and lowering mechanism  86  includes a columnar base plate  88  extending along the Z-axis directions. The lifting and lowering mechanism  86  moves the articulated arm  90  in the Z-axis directions along the base plate  88 . The lifting and lowering mechanism  86  includes, for example, an electric motor, not depicted, that is mounted on a lower portion of the base plate  88  and that has a shaft with a drive pulley fixed thereto, and a driven pulley, not depicted, mounted on an upper portion of the base plate  88 . A toothed endless belt, not depicted, is trained around the drive pulley and the driven pulley. A first support  92 A of metal is secured to the toothed endless belt. 
     When the electric motor of the lifting and lowering mechanism  86  is energized to rotate the shaft thereof about its own central axis in a first direction, the first support  92 A is lifted. On the other hand, when the electric motor of the lifting and lowering mechanism  86  is reversed to rotate the shaft thereof about its own central axis in a second direction opposite the first direction, the first support  92 A is lowered. In this manner, the first support  92 A is moved one or the other of the Z-axis directions. 
     However, the lifting and lowering mechanism  86  is not limited to any structures insofar as it can lift and lower the first support  92 A. The lifting and lowering mechanism  86  may alternatively be a ball-screw-type lifting and lowering mechanism, for example. The ball-screw-type lifting and lowering mechanism has a pair of guide rails, not depicted, that are spaced from each other and that extend along the Z-axis directions, and a movable plate, not depicted, shaped as a flat plate slidably mounted on the guide rails for slidable movement therealong. 
     The first support  92 A is fixed to a face side, i.e., a first surface, of the movable plate, and a nut, not depicted, is disposed on a reverse side, i.e., a second surface, of the movable plate. The nut is operatively threaded over a ball screw extending generally parallel to the guide rails. The ball screw has an end coupled to a stepping motor, not depicted. When the stepping motor is energized, the first support  92 A is moved in one of the Z-axis directions, i.e., is lifted or lowered. 
     A first rotating mechanism  94 A having a rotary actuator such as an electric motor is fixedly mounted on the first support  92 A. The rotary actuator is oriented such that its rotational shaft extends generally parallel to the Z-axis directions. A first arm  96 A that extends along directions parallel to the X-axis directions and the Y-axis directions has an end mounted on the first rotating mechanism  94 A. 
     A second rotating mechanism  94 B is mounted on the other end of the first arm  96 A. The second rotating mechanism  94 B has a rotary actuator such as an electric motor whose rotational shaft extends generally parallel to the Z-axis directions. A second arm  96 B that extends along directions parallel to the X-axis directions and the Y-axis directions has an end mounted on the second rotating mechanism  94 B. 
     A third rotating mechanism  94 C is mounted on the other end of the second arm  96 B. The third rotating mechanism  94 C has a rotary actuator such as an electric motor whose rotational shaft extends generally parallel to the Z-axis directions. A second support  92 B of metal is mounted on the third rotating mechanism  94 C. The changing device  100  for changing cutting blades  36 , cutting blades  52 , etc. is mounted on the second support  92 B. 
     When the changing device  100  does not change cutting blades  36 , cutting blades  52 , etc., the changing device  100  is placed in a position, i.e., a retracted position, adjacent to the base plate  88 , as depicted in  FIG. 4 . When the changing device  100  is to change cutting blades  36 , cutting blades  52 , etc., the moving unit  84  is actuated to place the changing device  100  in a position, i.e., a changing position, above the base  4 .  FIG. 5  illustrates in perspective the changer unit  76  with the changing device  100  disposed in the changing position. 
     The changing device  100  is movable, i.e., liftable and lowerable, along the Z-axis directions by the lifting and lowering mechanism  86 , and is also movable along a plane, i.e., a horizontal plane, parallel to the X-axis directions and the Y-axis directions by the articulated arm  90 . In other words, the changing device  100  can be brought to any position in a three-dimensional space by the lifting and lowering mechanism  86  and the articulated arm  90 . 
     A structural example of the changing device  100  will be described hereinbelow.  FIG. 6  illustrates the changing device  100  in perspective.  FIG. 7A  illustrates the changing device  100  in side elevation, and  FIG. 7B  illustrates the changing device  100  in front elevation. In  FIG. 7B , a coupling member  114   a  and a coupling member  114   b  of the components of the changing device  100  are omitted from illustration. The structural details of the changing device  100  will be described below mainly with reference to  FIG. 6 . 
     The changing device  100  includes a mounting and dismounting unit  102  for mounting and dismounting a cutting blade  36  or a cutting blade  52  and a nut  48  or a nut  64  (see  FIGS. 2 and 3 ). A rotating mechanism  104  for rotating the mounting and dismounting unit  102  is coupled to the mounting and dismounting unit  102 . 
     The rotating mechanism  104  includes a rotational member, i.e., a shaft,  106  coupled to the mounting and dismounting unit  102  and a rotary actuator, not depicted, such as an electric motor for rotating the rotational member  106  about its central axis, i.e., a rotational axis,  106   a  extending through the rotational member  106 . The rotary actuator rotates the rotational member  106  bidirectionally, i.e., in a first direction and a second direction opposite the first direction, about the rotational axis  106   a . When the rotational member  106  is rotated about the rotational axis  106   a , the mounting and dismounting unit  102  coupled to the rotational member  106  is rotated about the rotational axis  106   a  in unison with the rotational member  106 . 
     The mounting and dismounting unit  102  includes a frame  110  coupled to the rotational member  106  of the rotating mechanism  104 . The frame  110  includes a pair of plate-shaped support members  112   a  and  112   b  of metal or the like that are vertically spaced from each other and extend generally parallel to each other. 
     A pair of coupling members  114   a  and  114   b , each in the shape of a rectangular parallelepiped, are disposed between the support members  112   a  and  112   b . The coupling member  114   a  is fixed to an end portion of the support member  112   a  that is closer to the rotational member  106  and an end portion of the support member  112   b  that is closer to the rotational member  106 . The coupling member  114   b  is fixed to another end portion of the support member  112   a  that is remoter from the rotational member  106  and another end portion of the support member  112   b  that is remoter from the rotational member  106 . The support members  112   a  and  112   b  are thus coupled to each other by the coupling members  114   a  and  114   b.    
     A nut turner, i.e., a nut mounting and dismounting unit,  120  for holding and rotating a nut  48  or a nut  64  (see  FIGS. 2 and 3 ) with which to mount a cutting blade  36  or a cutting blade  52  on the cutting unit  30  is mounted on the frame  110 . The nut turner  120  includes a nut holder  122  for holding a nut  48  or a nut  64  and a columnar rotor, i.e., shaft,  124  (see  FIG. 7B ) coupled to the nut holder  122 . 
     The rotor  124  is housed in a tubular housing  126 . The rotor  124  has an end portion, i.e., a distal end portion, exposed out of the housing  126  and connected to the nut holder  122 . The rotor  124  also has another end portion, i.e., a proximal end portion, coupled to a rotary actuator  128  such as an electric motor for rotating the rotor  124  about its central axis, i.e., a rotational axis,  124   a  extending through the rotor  124 . 
     The rotary actuator  128  rotates the rotor  124  bidirectionally, i.e., in a first direction and a second direction opposite the first direction, about the rotational axis  124   a . When the rotor  124  is rotated about the rotational axis  124   a , the nut holder  122  that is coupled to the rotor  124  is rotated about the rotational axis  124   a  in unison with the rotor  124 . 
     The support member  112   a  has an opening, not depicted, centrally defined therein that extends thicknesswise therethrough, and the support member  112   b  has an opening, not depicted, centrally defined therein that extends thicknesswise therethrough. The end portion of the rotor  124  that is exposed out of the housing  126  is inserted in the opening in the support member  112   a  and protrudes from the support member  112   a  out of the frame  110 . The other end portion of the rotor  124  is inserted, together with an end of the housing  126 , in the opening in the support member  112   b  and protrudes from the support member  112   b  out of the frame  110 . 
     The end portion of the rotor  124  is coupled to the nut holder  122  outside of the frame  110 . The other end portion of the rotor  124  is coupled to the rotary actuator  128  outside of the frame  110 . The nut turner  120  is thus mounted on the frame  110  with the frame  110  sandwiched between the nut holder  122  and the rotary actuator  128 . The nut turner  120  is disposed such that the rotational axis, corresponding to the rotational axis  124   a , of the nut holder  122  extends along direction perpendicular to the rotational axis  106   a  of the rotational member  106 . 
     The nut holder  122  includes a cylindrical rotational member  130  fixed to the end portion of the rotor  124 . The rotational member  130  is normally biased to move away from the support member  112   a  by a spring or the like. When an external force is axially applied to the rotational member  130  toward the support member  112   a , the rotational member  130  is axially moved toward the support member  112   a  against the bias of the spring or the like. 
     The rotational member  130  has a surface  130   a  positioned remotely from the support member  112   a . A plurality of (four in  FIG. 6 ) holding pins  132  project axially from the surface  130   a  and are angularly spaced at generally equal intervals along the circumferential directions of the surface  130   a.    
     The holding pins  132  are positioned for alignment with the respective through holes  48   b  (see  FIG. 2 ) in the nut  48  or the respective through holes  64   b  (see  FIG. 3 ) in the nut  64 , and can be inserted into the respective through holes  48   b  or the respective through holes  64   b . The number, size, layout, etc. of the holding pins  132  are appropriately selected depending on the through holes  48   b  or the through holes  64   b.    
     A plurality of (four in  FIG. 6 ) gripping members  134  for gripping the nut  48  or the nut  64  are disposed around the rotational member  130  and angularly spaced at substantially equal intervals circumferentially along the rotational member  130 . Each of the gripping members  134  is of a columnar shape and has a proximal end portion, i.e., an end portion, fixed to an outer circumferential surface of the rotational member  130 . 
     Each of the gripping members  134  has a distal end portion, i.e., another end portion, protruding from the surface  130   a  of the rotational member  130 . The distal end portion has a hook  134   a  bent toward the center of the rotational member  130 . The gripping members  134  are normally biased by springs or the like to move radially outwardly of the rotational member  130 . When an external force is applied radially inwardly to the gripping members  134 , the gripping members  134  are moved radially inwardly against the bias of the springs or the like. 
     A hollow cylindrical cover  136  is disposed around the rotational member  130 . The cover  136  is rotatable about the rotational axis  124   a  independently of the rotational member  130 , and extends in surrounding relation to the rotational member  130  and the proximal end portions of the gripping members  134 . When the surface  130   a  of the rotational member  130  is axially pressed into the cover  136 , i.e., toward the support member  112   a , the rotational member  130  and the gripping members  134  are pushed into the cover  136  while elastically deforming the spring or the like by which the rotational member  130  is normally biased. 
     When the rotational member  130  is pushed into the cover  136 , the distal end portions of the gripping members  134  where the hooks  134   a  are positioned are contacted and pressed by an inner wall surface of the cover  136 . At this time, the distal end portions of the gripping members  134  are moved radially inwardly with respect to the rotational member  130  while elastically deforming the springs or the like by which the gripping members  134  are normally biased. The gripping members  134  are oriented such that their longitudinal axes extend along the inner wall surface of the cover  136 . The gripping members  134  are now in a closed state. At this time, the hooks  134   a  of the gripping members  134  are disposed radially inwardly from an outer circumferential edge of the rotational member  130 , for example. 
     On the other hand, when the rotational member  130  is released from the axial push, the rotational member  130  is axially moved in a direction out of the cover  136  under the bias of the spring or the like, releasing the distal end portions of the gripping members  134  from the push from inner wall surface of the cover  136 . Therefore, the distal end portions of the gripping members  134  are moved radially outwardly with respect to the rotational member  130  under the bias of the springs or the like. The distal end portions of the gripping members  134  are now disposed more radially outwardly with respect to the rotational member  130  than they were in the closed state. The gripping members  134  are now in an open state. At this time, the hooks  134   a  of the gripping members  134  are disposed radially outwardly from the outer circumferential edge of the rotational member  130 , for example. 
     A plurality of (four, for example) pins  138  protrude from an outer circumferential surface of the rotational member  130 . The cover  136  has a plurality of (four, for example) openings  136   a  defined therein that extend radially from an outer circumferential surface to an inner circumferential surface of the cover  136 . At least portions of pins  138  are inserted respectively in the openings  136   a.    
     The openings  136   a  have respective ends remote from the support member  112   a  that are defined by respective stepped surfaces each including a first pin receiving portion  136   b  and a second pin receiving portion  136   c . The second pin receiving portion  136   c  is disposed in a position more spaced from the surface  130   a  of the rotational member  130 , i.e., closer to the support member  112   a , than the first pin receiving portion  136   b.    
     When the nut holder  122  is in an initial state where the rotational member  130  is not pushed into the cover  136 , the pins  138  are held in contact with, and hence are seated on, the first pin receiving portions  136   b . When the rotational member  130  is then pushed into the cover  136 , the pins  138  are spaced, i.e., unseated, from the first pin receiving portions  136   b . Then, the rotor  124  is turned in the first direction about the rotational axis  124   a , moving the pins  138  from the first pin receiving portion  136   b  side to the second pin receiving portion  136   c  side. 
     Thereafter, when the rotational member  130  is released from the push, the pins  138  are allowed to contact the respective second pin receiving portions  136   c  and hence to be supported by, i.e., seated on, the second pin receiving portions  136   c . The rotational member  130  remains pressed in the cover  136 , keeping the gripping members  134  in the closed state. 
     On the other hand, when the rotational member  130  pressed in the cover  136  is further pushed into the cover  136 , the pins  138  are unseated from the second pin receiving portions  136   c . Then, when the rotor  124  is turned in the second direction that is opposite the first direction, the pins  138  are moved from the second pin receiving portion  136   c  side to the first pin receiving portion  136   b  side. 
     Thereafter, when the rotational member  130  is released from the push, the pins  138  are allowed to contact the respective first pin receiving portions  136   b  and hence to be supported by, i.e., seated on, the first pin receiving portions  136   b . The rotational member  130  are pushed in a direction out of the cover  136 , bringing the gripping members  134  into the open state. 
     The nut turner  120  turns while holding the nut  48  or the nut  64 . Specifically, the surface  130   a  of the rotational member  130  contacts the nut  48  or the nut  64  such that the holding pins  132  are inserted into the respective through holes  48   b  (see  FIG. 2 ) in the nut  48  or the respective through holes  64   b  (see  FIG. 3 ) in the nut  64 . Then, when the rotational member  130  is pushed into the cover  136 , the gripping members  134  are brought into the closed state, causing the hooks  134   a  to contact the outer circumferential surface of the nut  48  or the nut  64  to thereby grip the nut  48  or the nut  64 . 
     When the rotary actuator  128  rotates the rotor  124  (see  FIG. 7B ) while the nut  48  or the nut  64  is being gripped by the gripping members  134 , the rotational member  130  coupled to the rotor  124  is rotated, rotating the nut  48  or the nut  64  held by the gripping members  134 . 
     Since the nut turner  120  holds and rotates the nut  48  or the nut  74 , the nut  48  or the nut  64  can automatically be loosened and detached or tightened and attached at the time the cutting blade  36  or the cutting blade  52  mounted on the cutting unit  30  is changed. 
     For example, for removing the nut  48  (see  FIG. 2 ) mounted on the mount flange  42  of the cutting unit  30 , the lifting and lowering mechanism  86  and the articulated arm  90  (see  FIGS. 4 and 5 ) move the changing device  100  and place the changing device  100  into the processing chamber cover  28  through the inlet/outlet port  28   a  (see  FIG. 1 ) defined therein. The rotating mechanism  104  then turns the mounting and dismounting unit  102  to cause the nut holder  122  to face the mount flange  42 . 
     Thereafter, the nut holder  122  is moved toward the mount flange  42  until the surface  130   a  of the rotational member  130  is pressed against the nut  48  mounted on the mount flange  42 . At this time, the holding pins  132  of the rotational member  130  are inserted into the respective through holes  48   b  in the nut  48 . 
     The rotational member  130  is pressed into the cover  136  by the nut  48 , bringing the gripping members  134  into the closed state. The nut  48  is now gripped by the hooks  134   a  of the gripping members  134 . 
     Then, the rotary actuator  128  rotates the rotor  124  (see  FIG. 7B ) to rotate the rotational member  130  in the first direction around the rotational axis  124   a , i.e., a direction to loosen the nut  48 . The nut  48  gripped by the rotational member  130  is rotated and detached from the boss  46  of the mount flange  42 . When the rotational member  130  that has been pushed into the cover  136  is rotated in the first direction, the pins  138  are moved from the first pin receiving portion  136   b  side to the second pin receiving portion  136   c  side. 
     Thereafter, the nut holder  122  is moved away from the mount flange  42 . At this time, the pins  138  are supported by the second pin receiving portions  136   c , keeping the rotational member  130  pushed in the cover  136 . The gripping members  134  thus remain in the closed state, continuously gripping the nut  48 . 
     On the other hand, for mounting the nut  48  on the mount flange  42 , the nut holder  122  that is holding the nut  48  is brought into facing relation to the mount flange  42  and moved toward the mount flange  42 . The nut  48  held by the nut holder  122  is positioned at the distal end of the boss  46  of the mount flange  42 , and then pushes the rotational member  130  into the cover  136  upon continued movement of the nut holder  122 . 
     Then, the rotary actuator  128  rotates the rotor  124  (see  FIG. 7B ), rotating the rotational member  130  in the second direction opposite the first direction around the rotational axis  124   a , i.e., a direction to tighten the nut  48 . The nut  48  is rotated and threaded and tightened over the externally threaded outer circumferential surface  46   a  of the boss  46  of the mount flange  42 , and mounted on the mount flange  42 . When the rotational member  130  that has been pushed into the cover  136  is rotated in the second direction, the pins  138  are moved from the second pin receiving portion  136   c  side to the first pin receiving portion  136   b  side. 
     Thereafter, the nut holder  122  is moved away from the mount flange  42 . The rotational member  130  is pushed in a direction out of the cover  136 , releasing the nut  48  from the gripping members  134 . The pins  138  are supported by the first pin receiving portions  136   b.    
     The gripping members  134  may be brought selectively into the closed state and the open state by any of various mechanisms other than those described above that include the pins  138  and the openings  136   a . For example, instead of the pins  138  on the rotational member  130 , an actuator for moving the cover  136  heightwise of the cover  136  in directions parallel to the rotational axis  124   a  may be incorporated in the mounting and dismounting unit  102 . The actuator may include an air cylinder or the like and may be fixed to the support member  112   a . The actuator moves the cover  136  to bring the gripping members  134  selectively into the closed state and the open state. 
     An annular member  140  made of metal or the like is disposed between the support members  112   a  and  112   b . The annular member  140  that lies generally parallel to the support members  112   a  and  112   b  surrounds the housing  126 , i.e., the rotor  124 , and stays out of contact with the housing  126 . 
     The annular member  140  is coupled to the support member  112   a  by a plurality of resilient bodies, i.e., resilient members,  142   a  and is also coupled to the support member  112   b  by a plurality of resilient bodies, i.e., resilient members,  142   b . The annular member  140  is suspended by the resilient members  142   a  and  142   b  and held out of contact with the support members  112   a  and  112   b  (see  FIG. 7B ). 
     For example, each of the resilient members  142   a  and  142   b  is a resiliently contractible and extensible member such as a spring or a rubber band. When an external force is applied to the annular member  140 , the annular member  140  is moved or turned in a direction depending on the applied external force while being resiliently supported by the resilient members  142   a  and  142   b  as they are contracted and extended. 
     A holder  150 A, i.e., a first holder, and a holder  150 B, i.e., a second holder, for holding the cutting blade  36  or the cutting blade  52  are coupled to respective outer circumferential surfaces of the annular member  140 . Each of the holders  150 A and  150 B is a disk-shaped member made of resin, metal, or like, and has a circular surface  150   a  facing away from the annular member  140  for holding the cutting blade  36  or the cutting blade  52  thereon. The holders  150 A and  150 B are disposed in respective positions opposite each other across the frame  110  such that the surfaces  150   a  of the holders  150 A and  150 B face outwardly away from the frame  110 . 
     The holders  150 A and  150 B are angularly spaced 90° from the nut holder  122  in the circumferential directions of the rotational member  106  of the rotating mechanism  104 , i.e., in the rotational directions along which the rotational member  106  rotates. The nut holder  122 , the surface  150   a  of the holder  150 A, and the surface  150   a  of the holder  150 B are angularly spaced from each other around the rotational axis  106   a , and face outwardly away from the rotational axis  106   a.    
     A structural example of the holders  150 A and  150 B will be described below.  FIG. 8A  illustrates the holder  150 A in plan and  FIG. 8B  illustrates the holder  150 A in cross section. Although the structural and functional details of the holder  150 A will be described below, the structural and functional details of the holder  150 B are identical to those of the holder  150 A and hence will not be described below. 
     The holder  150 A includes a disk-shaped frame  152  made of resin, metal, or the like. The frame  152  includes a face side, i.e., a first surface,  152   a , and a reverse side, i.e., a second surface,  152   b  that lie generally parallel to each other. The face side  152   a  of the frame  152  acts as the surface  150   a  of the holder  150 A. The face side  152   a  of the frame  152  has a circular first groove, i.e., a first recess,  152   c  defined centrally therein. The first groove  152   c  is larger in diameter than the face side  38   a  (see  FIG. 9A ) of the base  38  of the cutting blade  36  and the face side  62   a  (see  FIG. 9B ) of the holder flange  62 . 
     Moreover, the bottom of the first groove  152   c  has a circular second groove, i.e., a second recess,  152   d  defined centrally therein. The bottom of the second groove  152   d  has an annular third groove, i.e., a third recess,  152   e  that is defined therein and that has a predetermined width along the outer circumferential edge of the second groove  152   d.    
     An annular elastic member  154  is fitted in the third groove  152   e . The elastic member  154  is made of an elastic material that is elastically deformable, such as rubber or resin. The elastic member  154  includes an annular base  154   a  fitted in the third groove  152   e  and a pair of lips  154   b  protruding from the base  154   a . One of the lips  154   b  extends continuously along a radially outer portion of the annular base  154   a , whereas the other lip  154   b  extends continuously along a radially inner portion of the annular base  154   a.    
     The lips  154   b  are progressively spaced away from each other in a direction toward their tip ends away from the base  154   a . Specifically, the lips  154   b  that protrudes from the base  154   a  fitted in the third groove  152   e  are inclined to the face side  152   a  of the frame  152 . 
     The lips  154   b  spread from the inside toward outside of the base  154   a  in the radial directions of the base  154   a . Specifically, the lips  154   b  are oriented from the inside toward outside of the base  154   a  in the widthwise directions of the third groove  152   e . The tip ends of the lips  154   b  protrude from the face side  152   a  of the frame  152  in the widthwise directions of the frame  152 . 
     The base  154   a  has a plurality of through holes  154   c  defined therethrough in a region thereof that overlaps the space between the lips  154   b . For example, as illustrated in  FIG. 8A , the base  154   a  has six through holes  154   c  spaced at generally equal intervals along the circumferential directions of the elastic member  154 . The through holes  154   c  have ends that are open at the face side  152   a  of the frame  152  and other ends joined to an annular fourth groove, i.e., a fourth recess,  152   f  defined in the bottom of the third groove  152   e.    
     The fourth groove  152   f  is connected to an end of a fluid channel  156  that includes a tube, a pipe, or the like. The other end of the fluid channel  156  is connected through a valve  158  to a suction source  160 . The valve  158  includes, for example, a solenoid-operated valve that is selectively openable and closable by an electric signal applied to its solenoid. The suction source  160  includes an ejector or the like. When the valve  158  is opened, a negative pneumatic pressure generated by the suction source  160  is transmitted through the fluid channel  156 , the fourth groove  152   f  in the frame  152 , and the through hole  154   c  in the elastic member  154  and acts in the space between the lips  154   b.    
     A pressure measuring device, i.e., a pressure sensor,  162  for measuring the pneumatic pressure in the fluid channel  156  is connected to the fluid channel  156  at a position between the fourth groove  152   f  and the valve  158 . For example, the pressure measuring device  162  measures the pneumatic pressure in the fluid channel  156  based on the gage pressure, i.e., the difference between the absolute pressure and the atmospheric pressure. The value of the pneumatic pressure in the fluid channel  156  that is measured by the pressure measuring device  162  is output to the control unit  82  (see  FIG. 1 ) where the measured value of the pneumatic pressure is stored in the storage unit  82   b.    
     The cutting blade  36  or the cutting blade  52  is held by the holder  150 A described above. For changing the cutting blade  36  or the cutting blade  52 , the cutting blade  36  or the cutting blade  52  that is mounted on the cutting unit  30 , e.g., a used cutting blade, and a cutting blade  36  or a cutting blade  52  as a replacement cutting blade, e.g., an unused cutting blade, are held by the holder  150 A. The holder  150 A is capable of holding either hub-type cutting blades  36  or washer-type cutting blades  52 . 
       FIG. 9A  illustrates in cross section the holder  150 A as it is holding a hub-type cutting blade  36 . When the holder  150 A is to hold the cutting blade  36 , the valve  158  is opened to allow the negative pneumatic pressure from the suction source  160  to act in the space between the lips  154   b . Then, while the surface  150   a  of the holder  150 A is facing the cutting blade  36 , the holder  150 A is moved closely to the base  38  of the cutting blade  36 . 
     Upon contact of the face side  38   a  of the base  38  with the tip ends of the lips  154   b , the space between the lips  154   b  is closed and starts being evacuated by the negative pneumatic pressure from the suction source  160 . The lips  154   b  are elastically deformed and brought into intimate contact with the cutting blade  36 , which is now held under suction by the holder  150 A. 
       FIG. 9B  illustrates in cross section the holder  150 A as it is holding a washer-type cutting blade  52 . When the holder  150 A is to hold the cutting blade  52 , the holder  150 A attracts the face side  62   a  of the holder flange  62  under suction and also attracts the cutting blade  52  under suction through the through holes  62   d  in the holder flange  62 . 
     Specifically, for example, the valve  158  is opened to allow the negative pneumatic pressure from the suction source  160  to act in the space between the lips  154   b . Then, while the surface  150   a  of the holder  150 A is facing the holder flange  62  and the cutting blade  52 , the holder  150 A is moved closely to the holder flange  62 . 
     Upon contact of the face side  62   a  of the holder flange  62  with the tip ends of the lips  154   b , the space between the lips  154   b  is closed and starts being evacuated by the negative pneumatic pressure from the suction source  160 . The lips  154   b  are elastically deformed and brought into intimate contact with the holder flange  62 , which is now held under suction by the holder  150 A. 
     The negative pneumatic pressure from the suction source  160  also acts through the through holes  62   d  in the holder flange  62  on the cutting blade  52 . Therefore, the cutting blade  52  is held under suction by the holder  150 A through the holder flange  62 . 
     The through holes  62   d  are open in an area of the face side  62   a  of the holder flange  62  that corresponds to the elastic member  154  and in an area of the reverse side  62   b  of the holder flange  62  that is held in contact with the cutting blade  52 . Each of the through holes  62   d  has a diameter of approximately 1 mm, for example. 
     The holder  150 A may hold only the holder flange  62 . Specifically, the holder  150 A attracts under suction the holder flange  62  that is not held in contact with the cutting blade  52 . At this time, though the negative pneumatic pressure from the suction source  160  slightly leaks through the through holes  62   d  in the holder flange  62 , the negative pneumatic pressure, i.e., the suction force, from the suction source  160  can adequately be controlled to enable the holder  150 A to hold the holder flange  62 . 
     The holder  150 A holds the cutting blade  36  or the cutting blade  52  in the manner described above. It is possible to ascertain whether the holder  150 A is properly holding a desired object or not by measuring the pneumatic pressure in the fluid channel  156  with the pressure measuring device  162 . 
     For example, when the holder  150 A holds the cutting blade  36  (see  FIG. 9A ), the space between the lips  154   b  is closed. The pneumatic pressure, denoted by Pal, developed in the fluid channel  156  when the holder  150 A is holding the cutting blade  36  and the pressure, denoted by P a2 , developed in the fluid channel  156  when the holder  150 A is not holding the cutting blade  36  are different from each other (P a2 &gt;P a1 ). Therefore, it is possible to ascertain whether the holder  150 A is holding the cutting blade  36  or not by comparing the pneumatic pressure measured by the pressure measuring device  162  with a preset threshold value P tha  (P a1 &lt;P tha &lt;P a2 ). 
     When the holder  150 A holds the cutting blade (see  FIG. 9B ), the pneumatic pressure, denoted by P b1 , developed in the fluid channel  156  when the holder  150 A is holding the cutting blade  52  and the holder flange  62 , the pneumatic pressure, denoted by P b2 , developed in the fluid channel  156  when the holder  150 A is holding only the holder flange  62 , and the pneumatic pressure, denoted by P b3 , developed in the fluid channel  156  when the holder  150 A is holding neither the cutting blade  52  nor the holder flange  62 , are different from each other (P b3 &gt;P b2 &gt;P b1 ). 
     Consequently, it is possible to ascertain whether the holder  150 A is holding the cutting blade  52  and the holder flange  62  or not by comparing the pneumatic pressure measured by the pressure measuring device  162  with a preset threshold value P thb1  (P b1 &lt;P thb1 &lt;P b2 ) and a preset threshold value P thb2  (P b2 &lt;P thb2 &lt;P b3 ). 
     The above ascertaining processes can be performed by storing the threshold values P tha , P thb1 , and P thb2  in the storage unit  82   b  (see  FIG. 1 ) of the control unit  82  and having the processing unit  82   a  perform a processing sequence for comparing the pneumatic pressure measured by the pressure measuring device  162  with the threshold values. For example, the storage unit  82   b  stores a program descriptive of the processing sequence for comparing the measured pneumatic pressure with the threshold values. The processing unit  82   a  accesses the storage unit  82   b , reads the program from the storage unit  82   b , and executes the read program to compare the measured pneumatic pressure with the threshold values. 
     As described above, the holder  150 A holds the cutting blade  36  or the cutting blade  52 . The holder  150 B also holds the cutting blade  36  or the cutting blade  52  in the same manner as the holder  150 A. 
     A cylindrical fifth groove, i.e., a fifth recess,  152   g  is defined in the face side  152   a  of the frame  152  radially inwardly of the fourth groove  152   f . The fifth groove  152   g  is larger in diameter than the boss  46  (see  FIG. 2 ) of the mount flange  42  and the third boss member  60   c  (see  FIG. 3 ) of the mount flange  54 . When the holder  150 A or the holder  150 B is moved closely to the cutting unit  30 , the distal end of the boss  46  or the third boss member  60   c  is inserted into the fifth groove  152   g , avoiding contact between the holder  150 A or the holder  150 B and the cutting unit  30 . 
     The holder  150 A or the holder  150 B may not necessarily have the elastic member  154 , but may have two concentric O-rings having different diameters instead of the elastic member  154 . One of the O-rings may be disposed on and extend along a side wall of the third groove  152   e  that is located in a radially outer position with respect to the frame  152  and the other O-ring may be disposed on and extend along a side wall of the third groove  152   e  that is located in a radially inner position with respect to the frame  152 . 
     As illustrated in  FIGS. 6 and 7B , the holder  150 A and the holder  150 B are coupled to the rotational member  106  of the rotating mechanism  104  through the resilient members  142   a  and the resilient members  142   b . Therefore, the holder  150 A and the holder  150 B can be tilted through respective certain angles. In other words, when an external force is applied to the holder  150 A or the holder  150 B, the surface  150   a  thereof is tilted in a certain direction. 
     When the cutting blade  36  or the holder flange  62  is brought into contact with the surface  150   a  of the holder  150 A or the surface  150   a  of the holder  150 B, the holder  150 A or the holder  150 B is tilted to have the surface  150   a  thereof lie parallel to the face side  38   a  of the cutting blade  36  or the face side  62   a  of the holder flange  62 . Therefore, the surface  150   a  of the holder  150 A or the surface  150   a  of the holder  150 B appropriately contacts the cutting blade  36  or the holder flange  62 , allowing the cutting blade  36  or the holder flange  62  to be reliably held under suction on the surface  150   a  of the holder  150 A or the surface  150   a  of the holder  150 B. 
     The changing device  100  described above changes the cutting blade  36  or the cutting blade  52 . For changing the cutting blade  36  or the cutting blade  52 , the cutting blade  36  or the cutting blade  52  mounted on the cutting unit  30  is detached, and then a replacement cutting blade  36  or a replacement cutting blade  52  is mounted on the cutting unit  30 . Replacement cutting blades  36  and replacement cutting blades  52  have been stored in the cutting apparatus  2  in advance. 
       FIG. 10A  illustrates in plan a support unit, i.e., a stocker,  200  where replacement cutting blades  36  and replacement cutting blades  52  are supported and stored. As illustrated in  FIG. 10A , the support unit  200  includes a support plate  202  having the same outline as a frame  15  that supports a workpiece  11 , for example. 
     The support plate  202  has an upper surface  202   a  having a plurality of blade case supports  204  constructed to support respective blade cases  172  that house cutting blades  36  or cutting blades  52 . The blade cases  172  are structurally identical to each other. For example, each of the blade case supports  204  includes a recessed region shaped complementarily to a blade case  172  and is capable of supporting a blade case  172  rested therein. Alternatively, each of the blade case supports  204  may be of a guide structure shaped complementarily to a blade case  172 . 
       FIG. 10B  illustrates one of the blade cases  172  in perspective. As illustrated in  FIG. 10B , the blade case  172  includes, for example, a storage casing  174  and a lid  176 , both made of synthetic resin such as polypropylene. The storage casing  174  and the lid  176  are coupled to each other by a hinge  178 . 
     The storage casing  174  has a bottom plate  180  and a side wall  182  extending along an outer peripheral edge of the bottom plate  180 . The storage casing  174  provides a storage area  174   a  defined inside of the side wall  182  for storing a cutting blade  36  or a cutting blade  52  therein. The side wall  182  includes a first hook  184  facing outwardly on an outer surface thereof opposite the hinge  178 . 
     The lid  176  has a top plate  186  and a side wall  188  extending along an outer peripheral edge of the top plate  186 . The height of the side wall  188  is lower than the height of the side wall  182  of the storage casing  174 . The side wall  188  includes a second hook  190  facing inwardly on an outer surface thereof opposite the hinge  178 . 
     When the lid  176  is turned about the hinge  178  toward the storage casing  174  until the lid  176  covers the storage casing  174 , the lid  176  closes the storage area  174   a  to prevent the cutting blade  36  or the cutting blade  52  stored in the storage area  174   a  from being dislodged out of the blade case  172 . When the first hook  184  and the second hook  190  intermesh each other in a locked state, the storage area  174   a  keeps itself closed by the lid  176 . On the other hand, when the lid  176  is turned about the hinge  178  away from the storage casing  174 , the storage area  174   a  is opened, allowing external access to the cutting blade  36  or the cutting blade  52  stored in the storage area  174   a.    
     When a blade case  172  that stores a cutting blade  36  or a cutting blade  52  therein is placed to rest in one of the blade case supports  204 , the cutting blade  36  or the cutting blade  52  is supported on the support unit  200 . Each of the blade case supports  204  of the support unit  200  supports a blade case  172  with its lid  176  being open. 
     The support plate  202  also has on the upper surface  202   a  thereof a plurality of holder flange supports  206  for supporting respective holder flanges  62 . For example, each of the holder flange supports  206  includes a recessed region shaped complementarily to a holder flange  62  and is capable of supporting a holder flange  62  rested therein. Alternatively, each of the holder flange supports  206  may be of a guide structure shaped complementarily to a holder flange  62 . 
     In addition, the support plate  202  has on the upper surface  202   a  thereof a plurality of board supports  208  for supporting a dressing board  19  for use in dressing cutting blades  36  or cutting blades  52  and an inspection board  21  for use in inspecting cutting blades  36  or cutting blades  52 . 
     For example, each of the board supports  208  is a recessed region shaped complementarily to a dressing board  19  or an inspection board  21  and is capable of supporting a dressing board  19  or an inspection board  21  rested therein. Alternatively, each of the board supports  208  may be of a guide structure shaped complementarily to a dressing board  19  or an inspection board  21 . 
     When a cutting blade  36  or a cutting blade  52  processes, i.e., cuts, workpieces  11 , a dressing process is carried out to intentionally wear the cutting edge of the cutting blade  36  or the cutting blade  52  on the dressing board  19  for the purpose of correcting the shape of the cutting blade  36  or the cutting blade  52  and keeping the cutting edge of the cutting blade  36  or the cutting blade  52  sharp enough. 
     The dressing process is carried out by having the cutting blade  36  or the cutting blade  52  cut into the dressing board  19 . The dressing board  19  is made up of abrasive grains of green carborundum (GC), white alundum (WA), or the like that are bound together by a binder such as a resin bond or a vitrified bond, for example. 
     When the dressing process is carried out, the binder of the cutting blade  36  or the cutting blade  52  is worn away by contact with the dressing board  19 , making the cutting blade  36  or the cutting blade  52  concentric with the spindle  34 , i.e., shaping the cutting blade  36  or the cutting blade  52  into a true circle. At the same time, as the binder is worn away, the abrasive grains are exposed from the binder, i.e., the cutting blade  36  or the cutting blade  52  is dressed. The accuracy with which the workpiece  11  is processed by the cutting blade  36  or the cutting blade  52  thus dressed increases. 
     Further, when a cutting blade  36  or a cutting blade  52  processes, i.e., cuts, workpieces  11 , another process is carried out using the inspection board  21  to inspect the shape of the cutting blade  36  or the cutting blade  52  and to correct the position of the cutting blade  36  or the cutting blade  52  by having the cutting blade  36  or the cutting blade  52  cut into the inspection board  21 . 
     Specifically, for example, the cutting blade  36  or the cutting blade  52  is caused to cut into the inspection board  21 , and a groove, i.e., a cut groove, formed in the inspection board  21  is observed to inspect whether the cutting edge of the cutting blade  36  or the cutting blade  52  is of a desired shape or not. Moreover, the position of the lower end of the cutting blade  36  or the cutting blade  52 , i.e., the cut depth to which the cutting blade  36  or the cutting blade  52  has cut into the inspection board  21 , is calculated on the basis of the depth of the cut groove formed in the inspection board  21 , and the height of the cutting blade  36  or the cutting blade  52  is adjusted on the basis of the calculated cut depth. 
     The inspection board  21  includes a plate-shaped member made of silicon, i.e., a silicon board. However, the inspection board  21  is not limited to any particular material insofar as the cutting blade  36  or the cutting blade  52  can cut into the inspection board  21 . For example, the inspection board  21  may be of the same material as the workpiece  11 . 
     A cutting blade  36  or a cutting blade  52  cuts into a dressing board  19  or an inspection board  21  while the dressing board  19  or the inspection board  21  is being held on the sub-tables  26  (see  FIG. 1 ). Specifically, for example, one of the sub-tables  26  holds thereon a dressing board  19  or an inspection board  21  to be cut by a cutting blade  36  or a cutting blade  52  mounted on one of the cutting units  30 . 
     The other sub-table  26  holds thereon a dressing board  19  or an inspection board  21  to be cut by a cutting blade  36  or a cutting blade  52  mounted on the other cutting unit  30 . Consequently, the sub-tables  26  are disposed in association with the respective cutting units  30 . 
     The various tools supported on the support unit  200  may be assigned identification marks representing information regarding those tools.  FIG. 11A  illustrates in plan a cutting blade  36  with an identification mark  212  attached thereto.  FIG. 11B  illustrates in plan a cutting blade  52  with an identification mark  214  attached thereto.  FIG. 11C  illustrates in plan a dressing board  19  or an inspection board  21  with an identification mark  216  attached thereto. 
     The identification mark  212 , the identification mark  214 , and the identification mark  216  each include a one-dimensional code, i.e., a barcode, a two-dimensional code, or the like. The identification mark  212 , the identification mark  214 , and the identification mark  216  may be directly printed on the objects to be identified thereby or seals or the like with the identification mark  212 , the identification mark  214 , and the identification mark  216  printed thereon may be affixed to the objects to be identified thereby. 
     The identification mark  212  attached to the cutting blade  36  and the identification mark  214  attached to the cutting blade  52  contains information representing, for example, the kind, i.e., the hub type or the washer type, the outside diameter, the inside diameter, the thickness, i.e., the width, the material of the abrasive grains, the particle size of the abrasive grains, the material of the binder, the serial number, etc. of the cutting blade  36  and the cutting blade  52 . 
     The identification mark  216  attached to the dressing board  19  contains information representing, for example, the size, the shape, the material of the abrasive grains, the particle size of the abrasive grains, the material of the binder, etc. of the dressing board  19 . The identification mark  216  attached to the inspection board  21  contains information representing, for example, the size, the shape, the material, the serial number, etc. of the inspection board  21 . 
     The identification mark  212  attached to the cutting blade  36 , the identification mark  214  attached to the cutting blade  52 , and the identification mark  216  attached to the dressing board  19  or the inspection board  21  are read by a reading unit included in the cutting apparatus  2 , for example. The reading unit includes a camera, a barcode reader, or the like, which is selected depending on the kind of the identification mark  212 , the identification mark  214 , and the identification mark  216 . 
     For example, the image capturing units  70  (see  FIG. 1 ) that are positioned adjacent to the cutting units  30  also function as reading units for reading the identification mark  212 , the identification mark  214 , and the identification mark  216 . However, reading units for reading those identification marks may be included in the cutting apparatus  2  separately from the image capturing units  70 . 
     The information read from the identification marks by the reading units is input to the control unit (see  FIG. 1 ) where the information is stored in the storage unit  82   b . For example, for changing the cutting blade  36  or the cutting blade  52 , the processing unit  82   a  of the control unit  82  refers to the information stored in the storage unit  82   b  and specifies an object to be held by the changer unit  76 . 
     Each of the blade cases  172  should preferably have an identification mark attached thereto that corresponds to a cutting blade  36  or a cutting blade  52  to be stored therein. The identification mark thus attached to a blade case  172  makes it possible to confirm easily a mismatch between the blade case  172  and a cutting blade  36  or a cutting blade  52  to be stored therein. 
     In this case, the information read and acquired by the reading unit from the identification mark  212  attached to the cutting blade  36  or the identification mark  214  attached to the cutting blade  52 , and the information read and acquired by the reading unit from the identification mark attached to the blade case  172  are stored in the storage unit  82   b.    
     Thereafter, the processing unit  82   a  of the control unit  82  refers to the information stored in the storage unit  82   b  and determines whether the blade case  172  and the cutting blade  36  or the cutting blade  52  to be stored therein correspond to each other or not. Specifically, the processing unit  82   a  determines whether the information acquired from the identification mark  212  or the identification mark  214  and the information acquired from the identification mark attached to the blade case  172  correspond to each other or not. In this case, the processing unit  82   a  functions as a blade case determining unit for performing such a determining process. 
     Similarly, the processing unit  82   a  of the control unit  82  also can refer to the information stored in the storage unit  82   b  and determine whether the cutting blade  36  or the cutting blade  52  and a dressing board  19  or an inspection board  21  to be used correspond to each other or not. Specifically, the processing unit  82   a  determines whether the information acquired from the identification mark  212  or the identification mark  214  and the information acquired from the identification mark  216  correspond to each other or not. In this case, the processing unit  82   a  functions as a board determining unit for performing such a determining process. 
     Moreover, in a case where processing conditions including information that represents the types, etc. of cutting blades are stored in the storage unit  82   b , the processing unit  82   a  of the control unit  82  can refer to the information stored in the storage unit  82   b  and determine whether the processing conditions and a cutting blade  36  or a cutting blade  52  to be processed correspond to each other or not. In this case, the processing unit  82   a  functions as a processing condition determining unit for performing such a determining process. 
     If the processing unit  82   a  determines that a blade case  172  and a cutting blade  36  or a cutting blade  52  to be stored therein do not correspond to each other, if the processing unit  82   a  determines that a cutting blade  36  or a cutting blade  52  and a dressing board  19  or an inspection board  21  to be used therewith do not correspond to each other, or if the processing unit  82   a  determines that processing conditions employed in cutting a workpiece  11  and a cutting blade  36  or a cutting blade  52  do not correspond to each other, then the control unit  82  may indicate such a discrepancy to the operator or the like or may shut down the cutting apparatus  2 . 
     The support unit  200  described above is housed in the container  8  (see  FIG. 1 ) included in the cutting apparatus  2 . The support unit  200  is pulled out of the container  8  by the first delivery unit  72  and delivered onto the cover  78  that is in the closed state. An openable and closable door, not depicted, is disposed on one side of the container  8  that faces the cleaning unit  12 . At the time at which the support unit  200  is to be removed from the container  8 , the door is opened and the lifting and lowering stage  6   a  of the elevator  6  is lifted or lowered to vertically align the container  8  placed thereon with the guide rails  16 . 
     The support plate  202  of the support unit  200  is similar in shape to the frames  15  that support respective workpieces  11 . Therefore, the first delivery unit  72  can deliver the support unit  200  onto the cover  78  in the closed state in the same manner as it delivers a frame unit  17  onto the chuck table  22 . 
     The destination to which the first delivery unit  72  delivers the support unit  200  is not limited to the cover  78 . The first delivery unit  72  may deliver the support unit  200  onto the guide rails  16 , for example. Furthermore, the cover  78  may be dispensed with, and the first delivery unit  72  may deliver the support unit  200  onto the chuck table  22 . 
     A specific example of a process of changing cutting blades  36  or cutting blades  52  mounted on the cutting units  30  of the cutting apparatus  2  will be described below. In the example, the cutting blades  36  (see  FIG. 2 ) mounted on the mount flanges  42  will be described below as cutting blades to be changed according to the changing process. 
     First, replacement cutting blades  36  are placed on the upper surface  202   a  of the support plate  202  of the support unit  200  (preparing step). Specifically, blade cases  172  housing respective replacement cutting blades  36 , e.g., unused cutting blades  36 , therein are placed on respective blade case supports  204 A on the upper surface  202   a  of the support plate  202 . 
     It is desirable that the blade cases  172  should be placed on the respective blade case supports  204  with the lids  176  being open. The lids  176  that remain open allows the replacement cutting blades  36  to replace the cutting blades  36  on the cutting units  30  properly even if the cutting apparatus  2  lacks an opening and closing unit for opening and closing the lids  176 . The support unit  200  that supports the replacement cutting blades  36  housed in the blade cases  172  is housed in the container  8  (see  FIG. 1 ). 
     Then, the first delivery unit  72  pulls the support unit  200  out of the container  8  and delivers the support unit  200  onto the cover  78  in the closed state. The replacement cutting blades  36  are now held on the cover  78 . As described above, the support unit  200  may be placed on the guide rails  16  or the chuck table  22 . 
     Then, the holder  150 B of the changing device  100  holds one of the replacement cutting blades  36  placed on the upper surface  202   a  of the support plate  202  (replacement cutting blade holding step).  FIG. 12A  schematically illustrates the changing device  100  in the replacement cutting blade holding step. 
     In the replacement cutting blade holding step, the lifting and lowering mechanism  86  and the articulated arm  90  (see  FIGS. 4 and 5 ) move the changing device  100  and place the changing device  100  in a blade transfer position over the support plate  202  held on the cover  78 , etc. The rotating mechanism  104  (see  FIG. 6 , etc.) turns the frame  110  to cause the holder  150 B to face the upper surface  202   a  of the support plate  202 . 
     Then, the changing device  100  is lowered to bring the holder  150 B into contact with the replacement cutting blade  36  placed on the upper surface  202   a  of the support plate  202 . The holder  150 B then holds the replacement cutting blade  36  under suction. Thereafter, the changing device  100  is lifted to move the holder  150 B away from the upper surface  202   a  of the support plate  202 . The replacement cutting blade  36  is now lifted off the upper surface  202   a  of the support plate  202  by the holder  150 B. 
     Then, the nut  48  mounted on the mount flange  42  of one of the cutting units  30  is removed from the mount flange  42  (nut removing step).  FIG. 12B  schematically illustrates the changing device  100  in the nut removing step. In the nut removing step, the lifting and lowering mechanism  86  and the articulated arm  90  (see  FIGS. 4 and 5 ) move the changing device  100  and place the changing device  100  in the processing chamber cover  28  (see  FIG. 1 ). The nut holder  122  of the changing device  100  is brought into facing relation to the mount flange  42  on which the cutting blade  36  and the nut  48  are mounted. 
     The nut holder  122  then holds and rotates the nut  48  mounted on the mount flange  42 . Specifically, while the gripping members  134  (see  FIG. 6 , etc.) are gripping the nut  48 , the rotary actuator  128  rotates the rotational member  130  (see  FIG. 6 , etc.) to rotate the nut  48  in the first direction around the rotational axis  124   a , i.e., the direction to loosen the nut  48 . As a result, the nut  48  is loosened and removed from the mount flange  42 . 
     Then, the nut holder  122  and the mount flange  42  are spaced apart from each other (first retracting step).  FIG. 12C  schematically illustrates the changing device  100  in the first retracting step. In the first retracting step, the articulated arm  90  (see  FIGS. 4  and  5 ) moves the changing device  100  away from the mount flange  42 . The nut holder  122  now moves away from the mount flange  42  while holding the nut  48 . 
     Then, the holder  150 A of the changing device  100  holds the cutting blade  36 , e.g., a used cutting blade  36 , mounted on the mount flange  42  of the cutting unit  30  (used cutting blade holding step).  FIG. 12D  schematically illustrates the changing device  100  in the used cutting blade holding step. 
     In the used cutting blade holding step, the rotational member  106  (see  FIG. 6 , etc.) of the rotating mechanism  104  is rotated to bring the surface  150   a  (see  FIG. 8A , etc.) of the holder  150 A into facing relation to the mount flange  42 . The changing device  100  is moved toward the mount flange  42  to cause the holder  150 A to contact the used cutting blade  36  mounted on the mount flange  42 . Then, the holder  150 A holds the used cutting blade  36  under suction. 
     Then, the holder  150 A and the mount flange  42  are spaced apart from each other (second retracting step).  FIG. 13A  schematically illustrates the changing device  100  in the second retracting step. In the second retracting step, the articulated arm  90  (see  FIGS. 4 and 5 ) moves the changing device  100  away from the mount flange  42 . The holder  150 A now moves away from the mount flange  42  while holding the used cutting blade  36 , dismounting the used cutting blade  36  from the mount flange  42 . 
     Then, the replacement cutting blade  36  held by the holder  150 B of the changing device  100  is mounted on the mount flange  42  (cutting blade mounting step).  FIG. 13B  schematically illustrates the changing device  100  in the cutting blade mounting step. In the cutting blade mounting step, the rotational member  106  (see  FIG. 6 , etc.) of the rotating mechanism  104  is rotated to bring the surface  150   a  (see  FIG. 8A , etc.) of the holder  150 B that is holding the replacement cutting blade  36  into facing relation to the mount flange  42 . 
     Then, the changing device  100  is moved toward the mount flange  42  to position the replacement cutting blade  36  such that the boss  46  (see  FIG. 2 ) of the mount flange  42  is inserted into the opening  36   a  (see  FIG. 2 ) in the replacement cutting blade  36 . When the replacement cutting blade  36  is then released from the holder  150 B, the replacement cutting blade  36  is mounted on the mount flange  42 . 
     Then, the holder  150 B and the mount flange  42  are spaced apart from each other (third retracting step).  FIG. 13C  schematically illustrates the changing device  100  in the third retracting step. In the third retracting step, the articulated arm  90  (see  FIGS. 4 and 5 ) moves the changing device  100  away from the mount flange  42 . The holder  150 B now moves away from the mount flange  42  and is spaced apart from the replacement cutting blade  36  mounted on the mount flange  42 . 
     Then, the nut  48  held by the nut holder  122  is mounted on the mount flange  42  (nut mounting step).  FIG. 13D  schematically illustrates the changing device  100  in the nut mounting step. In the nut mounting step, the rotational member  106  (see  FIG. 6 , etc.) of the rotating mechanism  104  is rotated to cause the nut holder  122  holding the nut  48  to face the mount flange  42 . The changing device  100  is moved toward the mount flange  42  to position the nut  48  at the distal end portion of the boss  46  (see  FIG. 2 ) of the mount flange  42 . 
     The rotary actuator  128  rotates the rotational member  130  (see  FIG. 6 , etc.) to rotate the nut  48  gripped by the gripping members  134  (see  FIG. 6 , etc.) in the second direction, i.e., a direction to tighten the nut  48 . The nut  48  is now tightened over the boss  46  (see  FIG. 2 ) of the mount flange  42 , and hence mounted on the mount flange  42 . The replacement cutting blade  36  is thus sandwiched between the mount flange  42  and the nut  48 , and secured to the distal end portion of the spindle  34 . 
     The cutting blade  36  mounted on the mount flange  42  has been changed according to the above sequence. The used cutting blade  36  held by the holder  150 A is placed on one of the blade case supports  204 A of the support unit  200 . 
     In the above changing process, the mount flange  42  and the changing device  100  may be moved toward and away from each other by moving the cutting unit  30 , i.e., the mount flange  42 . For example, in the first retracting step, the second retracting step, and the third retracting step, the cutting unit  30  may be moved away from the changing device  100  along one of the Y-axis directions to space the changing device  100  and the mount flange  42  apart from each other. 
     In the above changing process, the changing of the cutting blade  36  mounted on the mount flange  42  has been described. The cutting blade  52  (see  FIG. 3 ) mounted on the mount flange  54  may be changed in the same fashion as the cutting blade  36  mounted on the mount flange  42 . When the cutting blade  52  is to be changed, however, the cutting blade  52  and the holder flange  62  are held by the holder  150 A and the holder  150 B (see  FIG. 9B ), as described above. In other words, the cutting blade  52  and the holder flange  62  are changed instead of the cutting blade  36 . 
     For changing the cutting blade  52 , moreover, the holder  150 B holds the holder flange  62  and thereafter holds the cutting blade  52  in the replacement cutting blade holding step. Specifically, the holder  150 B is caused to face the holder flange  62  supported on one of the holder flange supports  206  (see  FIG. 10A ), and then holds the holder flange  62 . 
     Then, the holder  150 B that is holding the holder flange  62  is brought into facing relation to a replacement cutting blade  52  in one of the blade cases  172  supported on one of the blade case supports  204  (see  FIG. 10A ), and holds the replacement cutting blade  52  as well as the holder flange  62 . At this time, the replacement cutting blade  52  is held by the holder  150 B under a negative pneumatic pressure that is transmitted from the suction source  160  and that acts on the cutting blade  52  through the through holes  62   d  (see  FIG. 9B ) in the holder flange  62 . 
     The changing device  100  is also capable of changing the dressing board  19  or the inspection board  21  (see  FIG. 10A ) held on each of the sub-tables  26  (see  FIG. 1 ). When a cutting blade  36  or a cutting blade  52  is dressed by the dressing board  19 , for example, the cutting blade  36  or the cutting blade  52  forms a cut groove in the dressing board  19 . 
     When the dressing board  19  has had cut grooves formed over its entire surface by dressing numerous cutting blades  36  or cutting blades  52 , the dressing board  19  is replaced as a used dressing board with a replacement dressing board  19 , e.g., an unused dressing board  19 . Similarly, an inspection board  21  that has been used to inspect cutting blades  36  or cutting blades  52  is also replaced with a replacement inspection board  21 , e.g., an unused inspection board  21 , at an appropriate timing. 
     The holder  150 A and the holder  150 B of the changing device  100  are capable of holding plate-shaped members that include not only cutting blades  36  and cutting blades  52 , but also dressing boards  19  and inspection boards  21 . Consequently, the changing device  100  can change dressing boards  19  and inspection boards  21  held on the sub-tables  26 . 
       FIG. 14A  illustrates in perspective view the holder  150 A as it is holding a square dressing board  19 , depicted as a dressing board  19 A. The dressing board  19 A illustrated in  FIG. 14A  is of a size large enough to cover the entire face side  152   a  of the frame  152 . In  FIG. 14A , the dressing board  19 A has its outline indicated by the two-dot-and-dash lines. 
     For holding the dressing board  19 A on the holder  150 A, the lips  154   b  of the elastic member  154  are brought into contact with the dressing board  19 A. At this time, the holder  150 A is positioned such that the elastic member  154  is covered in its entirety by the dressing board  19 A. The space between the lips  154   b  is now closed by the dressing board  19 A. The dressing board  19 A is held under suction by the holder  150 A under a negative pneumatic pressure that is transmitted from the suction source  160  (see  FIG. 8B ) and that acts in the space between the lips  152   b.    
     The dressing board  19  to be held by the holder  150 A is not essentially limited to any size and shape.  FIG. 14B  illustrates in perspective the holder  150 A as it is holding an elongate rectangular dressing board  19 , depicted as a dressing board  19 B. The dressing board  19 B illustrated in  FIG. 14B  has longer sides longer than the diameter of the frame  152  and shorter sides shorter than the diameter of the frame  152 . However, the shorter sides of the dressing board  19 B are longer than the diameter of the elastic member  154 . 
     For holding the dressing board  19 B on the holder  150 A, the lips  154   b  of the elastic member  154  are brought into contact with the dressing board  19 B. At this time, the holder  150 A is positioned such that the elastic member  154  is covered in its entirety by the dressing board  19 B. The space between the lips  154   b  is now closed by the dressing board  19 B. The dressing board  19 B is held under suction by the holder  150 B under a negative pneumatic pressure that is transmitted from the suction source  160  (see  FIG. 8B ) and that acts in the space between the lips  154   b.    
     The holder  150 A may hold the dressing board  19  in various fashions other than the details described above. For example, the holder  150 A may hold the dressing board  19  with the lips  154   b  kept out of contact with the dressing board  19 . The lips  154   b  kept out of contact with the dressing board  19  are prevented from being worn by contacting the dressing board  19 . 
     Specifically, the lips  154   b  may have their tip ends not protruding from the face side  152   a  of the frame  152  but disposed within the first groove  152   c . With this arrangement, the holder  150 A can hold the dressing board  19 A such that the lips  154   b  are kept out of contact with the dressing board  19 A ( FIG. 14A ). 
     Specifically, the holder  150 A is positioned such that the first groove  152   c  is covered in its entirety by the dressing board  19 A. At this time, the dressing board  19 A is supported by the face side  152   a  of the frame  152  and kept out of contact with the lips  154   b . When a negative pneumatic pressure from the suction source  160  (see  FIG. 8B ) acts in the first groove  152   c , the dressing board  19 A is held under suction on the holder  150 A. 
     The holder  150 A may include a mechanism for ejecting a gas such as air to hold the dressing board  19  out of contact therewith according to the Bernoulli effect. Even when the dressing board  19 B that is sized and shaped not to cover the first groove  152   c  in its entirety, as illustrated in  FIG. 14B , the holder  150 A with such a mechanism is able to hold the dressing board  19 B out of contact with the lips  154   b.    
       FIGS. 14A and 14B  illustrate the manner in which the dressing board  19  is held by the holder  150 A. However, the holder  150 B is also able to hold the dressing board  19  in a similar manner. The holder  150 A and the holder  150 B are able to hold the inspection board  21  in the same manner as the dressing board  19 . 
     Next, a specific example of a process of changing a dressing board  19  and an inspection board  21  held on the sub-tables  26  of the cutting apparatus  2  will be described below. In the example, a dressing board  19  that is used to dress cutting blades  36  or cutting blades  52  will be described below as a board to be changed according to the changing process. 
     First, a replacement dressing board  19  is placed on the upper surface  202   a  of the support plate  202  of the support unit  200  (see  FIG. 10A ) (preparing step). Specifically, a replacement dressing board  19 , e.g., an unused dressing board  19 , is placed on the one of the board supports  208  on the upper surface  202   a  of the support plate  202 . The support unit  200  that supports the replacement dressing board  19  is housed in the container (see  FIG. 1 ). 
     The support unit  200  is pulled out of the container  8  by the first delivery unit  72  and delivered onto the cover  78  that is in the closed state. The replacement dressing boards  19  are now prepared on the cover  78 . Alternatively, the support unit  200  may be positioned on the guide rails  16  or the chuck table  22 . 
     Then, the holder  150 B of the changing device  100  holds the replacement dressing board  19  placed on the upper surface  202   a  of the support plate  202  (replacement board holding step).  FIG. 15A  schematically illustrates the changing device  100  in the replacement board holding step. 
     In the replacement board holding step, the lifting and lowering mechanism  86  and the articulated arm  90  (see  FIGS. 4 and 5 ) move the changing device  100  and place the changing device  100  in a board transfer position over the support plate  202  held on the cover  78 . The rotating mechanism  104  (see  FIG. 6 , etc.) turns the frame  110  to cause the holder  150 B to face the upper surface  202   a  of the support plate  202 . 
     Then, the changing device  100  is lowered to bring the holder  150 B into contact with the replacement dressing board  19  placed on the upper surface  202   a  of the support plate  202 . The holder  150 B then holds the replacement dressing board  19  under suction. Thereafter, the changing device  100  is lifted to move the holder  150 B away from the upper surface  202   a  of the support plate  202 . The replacement dressing board  19  is now lifted off the upper surface  202   a  of the support plate  202  by the holder  150 B. 
     Then, the holder  150 A of the changing device  100  holds a used dressing board  19  held on one of the sub-tables  26  (used board holding step).  FIG. 15B  schematically illustrates the changing device  100  in the used board holding step. 
     In the used board holding step, the lifting and lowering mechanism  86  and the articulated arm  90  (see  FIGS. 4 and 5 ) move the changing device  100  and place the changing device  100  in a loading and unloading position over the sub-table  26  on which the used dressing board  19  is positioned. The rotational member  106  (see  FIG. 6 , etc.) of the rotating mechanism  104  is rotated to cause the holder  150 A to face the sub-table  26 . 
     The changing device  100  is moved toward the sub-table  26  to bring the holder  150 A into contact with the used dressing board  19  held on the sub-table  26 . Thereafter, the holder  150 A holds the used dressing board  19  under suction. 
     Then, the holder  150 A and the sub-table  26  are spaced apart from each other (retracting step).  FIG. 15C  schematically illustrates the changing device  100  in the retracting step. In the retracting step, the lifting and lowering mechanism  86  (see  FIGS. 4 and 5 ) lifts the changing device  100 , moving the changing device  100  away from the sub-table  26 . The holder  150 A that is holding the used dressing board  19  is moved away from the sub-table  26 , and hence lifts the used dressing board  19 . 
     Then, the replacement dressing board  19  that is held by the holder  150 B of the changing device  100  is placed on the sub-table  26  (placing step).  FIG. 15D  schematically illustrates the changing device  100  in the placing step. 
     In the placing step, the rotational member  106  (see  FIG. 6 , etc.) of the rotating mechanism  104  is rotated to bring the holder  150 B that is holding the replacement dressing board  19  into facing relation to the sub-table  26 . The changing device  100  is moved toward the sub-table  26  to position the replacement dressing board  19  over the sub-table  26 . Thereafter, when the replacement dressing board  19  is released from the holder  150 B, the replacement dressing board  19  is placed on the sub-table  26 . 
     The dressing board  19  held on the sub-table  26  has been changed according to the above sequence. The used dressing board  19  held by the holder  150 A is placed on one of the board supports  208  of the support unit  200 . In the above changing process, the changing of the dressing board  19  has been described. In a case where an inspection board  21  is placed on one of the sub-tables  26 , the inspection board  21  can be changed in the same manner as the dressing board  19 . 
     As described above, the cutting apparatus  2  according to the present embodiment includes a support unit  200  for supporting a cutting blade  36  or a cutting blade  52  housed in a blade case  172 , a cutting unit  30  including a mount flange  42  on which a cutting blade  36  is to be mounted or a mount flange  54  on which a cutting blade  52  is to be mounted, a changing device, i.e., a changing mechanism,  100  for attaching a cutting blade  36  or a cutting blade  52  supported on the support unit  200  to the mount flange  42  or the mount flange  54 , and a moving unit, i.e., a moving mechanism,  84  for moving the changing device  100 . 
     Consequently, by supporting a cutting blade  36  or a cutting blade  52  housed in the blade case  172  on the support unit  200  and moving the changing device  100  with the moving unit  84 , it is possible to change the cutting blade  36  or the cutting blade  52  on the cutting unit  30 . In other words, the cutting apparatus  2  according to the present embodiment makes it unnecessary to manually remove the cutting blade  36  or the cutting blade  52  from the blade case  172  as in the existing technology. 
     The present invention is not limited to the details of the embodiment describe above, and various changes and modifications may be made therein.  FIG. 16  illustrates in perspective a cutting apparatus  2  including a support unit, i.e., a stocker,  250  according to a modification. The support unit  250  included in the cutting apparatus  2  illustrated in  FIG. 16  includes the rotary support unit  250 , instead of the container  8  (see  FIG. 1 ), for the rotary support unit  250  supporting various tools used on the cutting apparatus  2 , disposed in the vicinity of the changer unit  76 . For example, the support unit  250  is disposed in a region adjacent to the opening  4   b  in the base  4 . 
     The support unit  250  is arranged to support tools including cutting blades  36 , cutting blades  52 , holder flanges  62 , dressing boards  19 , inspection boards (see  FIG. 10A ), etc. Specifically, the support unit  250  includes a support plate, i.e., a support base,  252  for supporting the various tools placed thereon. 
       FIG. 17  illustrates in perspective the support unit  250  including a rotatable support plate  252 . For example, the support plate  252  is a disk-shaped member having an upper surface  252   a  on which there are disposed a plurality of blade case supports  254  each capable of supporting a blade case  172  that houses a cutting blade  52  therein. In  FIG. 17 , the blade case  172  has its lid, which may be similar to the lid  176  illustrated in  FIG. 10B , omitted from illustration. 
     For example, each of the blade case supports  254  is a recessed region shaped complementarily to a blade case  172  and is capable of supporting a blade case  172  rested therein. Alternatively, each of the blade case supports  254  may be of a guide structure shaped complementarily to a blade case  172 . 
     The support plate  252  also has on the upper surface  252   a  thereof a plurality of holder flange supports  256  for supporting respective holder flanges  62 . For example, each of the holder flange supports  256  is a recessed region shaped complementarily to a holder flange  62  and is capable of supporting a holder flange  62  rested therein. Alternatively, each of the holder flange supports  256  may be of a guide structure shaped complementarily to a holder flange  62 . 
     The blade case supports  254  and the holder flange supports  256  are angularly spaced at substantially equal intervals circumferentially along the support plate  252 . A shaft, i.e., a rotating mechanism,  258  rotatable by the power transmitted from a rotary actuator, i.e., a rotating mechanism, not depicted, such as an electric motor is coupled to the lower surface of a central portion of the support plate  252 . When the rotary actuator rotates the shaft  258  about its central axis, the support plate  252  is rotated about a rotational axis generally parallel to the Z-axis directions. The blade case supports  254  and the holder flange supports  256  are arrayed along the directions in which the support plate  252  is rotatable by the shaft  258 . 
     Below the support plate  252 , there are disposed a reading unit  260  for reading identification marks  214 , etc. attached to cutting blades  52  and a ring-shaped light source  262  for illuminating the identification marks  214 , etc. For example, cutting blades  52  are supported on the blade case supports  254  by the blade cases  172  such that the surfaces of the cutting blades  52  to which the identification marks  214  are attached face downwardly. 
     The reading unit  260  includes, for example, a visible-light camera, an infrared-ray camera, or the like, and reads the identification marks  214  attached to the cutting blades  52  through the support plate  252  and the blade cases  172 . The materials of the support plate  252  and the blade cases  172  are selected depending on the kind of the reading unit  260 . 
     For example, if the reading unit  260  includes a visible-light camera, then the support plate  252  and the blade cases  172  are made, wholly or partly, of a material that transmits visible light therethrough. Specifically, the support plate  252  is made, wholly or partly, of a transparent material such as plastic, e.g., polypropylene or the like, glass, e.g., quartz glass or borosilicate glass, or the like. The blade cases  172  are made, wholly or partly, of a transparent material such as plastic, e.g., polypropylene or the like. 
     The materials of the support plate  252  and the blade cases  172  may be changed as desired depending on the kind of the reading unit  260 . For example, if the reading unit  260  includes an infrared-ray camera, then the support plate  252  and the blade cases  172  are made, wholly or partly, of a material that transmits infrared radiation therethrough. 
     When the support plate  252  is rotated to position the reading unit  260  directly below a desired one of the blade case supports  254 , the reading unit  260  can read the identification mark  214  attached to the cutting blade  52  that is supported on the desired blade case support  254  through the blade case  172 . 
     The information of the identification mark  214  read by the reading unit  260  is output to the control unit  82  (see  FIG. 16 ). The reading unit  260  may be disposed above the support plate  252 . In this case, the cutting blades  52  are supported on the blade case supports  254  by the blade cases  172  such that the surfaces of the cutting blades  52  to which the identification marks  214  are attached are exposed upwardly. 
     Blade cases  172  that house cutting blades  36  may be placed on the blade case supports  254  on the support plate  252 . The support plate  252  may have on its upper surface  252   a  a plurality of board supports, which are similar to the board supports  208  illustrated in  FIG. 10A , for supporting dressing boards  19  and inspection boards  21 . 
     An opening and closing unit for opening and closing the lids  176  of the blade cases  172  supported on the support plate  252  is disposed in the vicinity of the support unit  250  thus constructed.  FIG. 18  illustrates in perspective the opening and closing unit, denoted by  270 . The opening and closing unit  270  includes a holding mechanism  272  disposed below the support plate  252 , for example, for holding under suction and securing, from below, the storage casing  174  of the blade case  172  placed on one of the blade case supports  254 . 
     The holding mechanism  272  includes a box-shaped base  272   a  housing therein an actuator, not depicted, such as an electric motor. The base  272   a  has two openings, for example, defined in an upper surface thereof. Two tubular holding rods  272   b  that can be lifted and lowered by the power of the actuator have respective lower ends inserted in the respective openings. 
     Suction pads  272   c  shaped as suction cups are mounted on the respective upper ends of the holding rods  272   b . The suction pads  272   c  are used in contact with the bottom plate  180  of the storage casing  174  of the blade case  172 . The suction pads  272   c  are held in fluid communication with a suction source, not depicted, such as an ejector, through fluid channels, etc. defined in the holding rods  272   b.    
     An unlocking mechanism  274  for lifting the lid  176  of the blade case  172  secured by the holding mechanism  272  to unlock the first hook  184  and the second hook  190  from each other is disposed laterally of the holding mechanism  272 . The unlocking mechanism  274  includes a push rod  274   a  that can be lifted and lowered by an actuator, not depicted, such as an electric motor. Alternatively, the unlocking mechanism  274  may include an air cylinder or the like for lifting and lowering the push rod  274   a  under pneumatic pressure. 
     A pushing mechanism  276  for further opening the lid  176  of the blade case  172  after the first hook  184  and the second hook  190  have been unlocked from each other and the lid  176  has been lifted from the storage casing  174  is disposed laterally of the unlocking mechanism  274  and the support plate  252 . 
     The pushing mechanism  276  includes a box-shaped base  276   a  housing therein an actuator, not depicted, such as an electric motor. The base  276   a  has an opening, for example, defined in a side surface thereof that faces the support plate  252 . A push rod  276   b  (see  FIG. 19A , etc.) movable laterally by the power of the actuator has an end inserted in the opening in the base  276   a.    
     A locking mechanism  278  for closing the lid  176  that has been opened by the pushing mechanism  276  to intermesh the first hook  184  and the second hook  190  is disposed above the support plate  252 . The locking mechanism  278  is disposed on an extension of the path along which the push rod  276   b  is movable, for example. 
     The locking mechanism  278  includes a movable arm  278   a  that can be moved laterally by an actuator, not depicted, such as an electric motor. Specifically, the movable arm  278   a  is movable along the extension of the path along which the push rod  276   b  is movable. The movable arm  278   a  has a distal end, oriented toward the pushing mechanism  276 , to which there are attached a pair of pressing wheels  278   b  usable in contact with the top plate  186  of the lid  176  and rotatable about its central axis, i.e., a rotational axis perpendicular to the directions along which the movable arm  278   a  is movable and the Z-axis directions. 
     For opening the lid  176  of the blade case  172  with the opening and closing unit  270 , the support plate  252  is rotated about the rotational axis thereof to position one of the blade cases  172  over the two holding rods  272   b  of the holding mechanism  272 . Then, the holding rods  272   b  are lifted to bring the suction pads  272   c , from below, into contact with the bottom plate  180  of the storage casing  174  of the blade case  172 . 
       FIG. 19A  illustrates in perspective the manner in which the blade case  172  placed on the blade case support  254  is secured by the holding mechanism  272 . After the suction pads  272   c  have contacted the bottom plate  180  of the storage casing  174 , the suction pads  272   c  hold the storage casing  174  under the negative pneumatic pressure from the suction source. Each of the blade case supports  254  has a clearance, i.e., an opening, defined therein for allowing the suction pads  272   c  to pass therethrough. 
     After the blade case  172  placed on the blade case support  254  has been secured by the holding mechanism  272 , the push rod  274   a  of the unlocking mechanism  274  is lifted to push the second hook  190  of the lid  176  upwardly. The first hook  184  and the second hook  190  are now unlocked from each other.  FIG. 19B  illustrates in perspective the manner in which the lid  176  of the blade case  172  is pushed upwardly by the unlocking mechanism  274 . 
     After the lid  176  has been pushed upwardly by the unlocking mechanism  274 , the push rod  276   b  of the pushing mechanism  276  is moved laterally to open the lid  176  further.  FIG. 20A  illustrates in perspective the manner in which the lid  176  of the blade case  172  is further opened by the pushing mechanism  276 . Specifically, the push rod  276   b  is moved laterally to have its distal end push an inner surface of the top plate  186  of the lid  176 , thereby further opening the lid  176 , as illustrated in  FIG. 20A . 
     After the lid  176  has been sufficiently opened, the push rod  276   b  is moved back from above the blade case  172 . With the lid  176  being sufficiently opened, the changing device  100  can easily access the cutting blade  52  housed in the blade case  172 . 
     For closing the lid  176  of the blade case  172  with the opening and closing unit  270 , the push rod  274   a  of the unlocking mechanism  274  is moved downwardly, for example. The negative pneumatic pressure applied from the suction source to the suction pads  272   c  of the holding mechanism  272  is cut off, and the holding rods  272   b  are lowered. Thereafter, the movable arm  278   a  of the locking mechanism  278  is moved toward the pushing mechanism  276 . 
       FIG. 20B  illustrates in perspective the manner in which the lid  176  of the blade case  172  is closed by the locking mechanism  278 . When the movable arm  278   a  is moved toward the pushing mechanism  276 , the pressing wheels  278   b  of the locking mechanism  278  are brought into contact with an outer surface of the top plate  186  of the lid  176 . When the movable arm  278   a  is moved further toward the pushing mechanism  276 , the pressing wheels  278   b  push the lid  176  toward the storage casing  174  until the lid  176  is closed over the storage casing  174 , intermeshing the first hook  184  and the second hook  190 . 
     For changing a used cutting blade  52  on one of the cutting units  30 , replacement cutting blades  52  and holder flanges  62  are supported on the support unit  250 . Then, the changer unit  76  holds one of the replacement cutting blades  52  and one of the holder flanges  62  that are supported on the support unit  250  with the changing device  100  (see  FIG. 9B ). 
     At this time, the control unit  82  controls the changer unit  76  on the basis of the information represented by the identification marks  214  attached to the cutting blades  52  to cause the changing device  100  to hold one of the cutting blades  52  and one of the holder flanges  62 . Accordingly, a desired cutting blade  52  on the support unit  250  can be selected as a replacement cutting blade  52 . Thereafter, the used cutting blade  52  and the used holder flange  62  that are mounted on the cutting unit  30  are replaced with the replacement cutting blade  52  and the holder flange  62  from the changing device  100  (see  FIGS. 12A through 13D ). 
     Similarly, for changing a used dressing board  19  or a used inspection board  21  on one of the sub-tables  26 , a replacement dressing board  19  or a replacement inspection board  21  are supported on the support unit  250 . The changer unit  76  holds the replacement dressing board  19  or the replacement inspection board  21  supported on the support unit  250 , and replaces the used dressing board  19  or the used inspection board  21  on the sub-table  26  with the replacement dressing board  19  or the replacement inspection board  21  from the support unit  250  (see  FIGS. 15A through 16D ). 
     The structural details and process details according to the above embodiment and modifications may be changed or modified without departing from the scope of the present invention. 
     The present invention is not limited to the details of the above described preferred embodiment. The scope of the invention is defined by the appended claims and all changes and modifications as fall within the equivalence of the scope of the claims are therefore to be embraced by the invention.