Patent Publication Number: US-11396109-B2

Title: Processing apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a processing apparatus. 
     Description of the Related Art 
     A cutting apparatus is known as a processing apparatus for cutting a workpiece such as a semiconductor wafer, an optical device wafer, and a package substrate along division lines. The cutting apparatus includes a chuck table for holding the workpiece and a cutting blade for cutting the workpiece held on the chuck table. The cutting blade wears with the use in cutting the workpiece. When the cutting blade wears, the workpiece cannot be cut to a desired depth. That is, the workpiece cannot be properly cut by this cutting blade worn. To cope with this problem, it is considered to detect the edge position of the cutting blade and then increase the depth of cut by an amount of wearing of the cutting blade according to the edge position detected. Under the circumstances, there has been proposed a technique of detecting the edge position of the cutting blade at a predetermined frequency. 
     Further, the cutting apparatus is designed so that when the edge projection amount of the cutting blade as the width of a cutting area of the cutting blade becomes less than the required depth of cut, an operator is informed of this condition and then prompted to exchange the cutting blade. 
     SUMMARY OF THE INVENTION 
     In performing an operation by using the cutting apparatus, there is an operator&#39;s desire such that the operator can grasp the timing of exchange of the cutting blade in advance to thereby efficiently perform the operation. 
     It is therefore an object of the present invention to provide a processing apparatus which can inform the operator of a guide for the timing of exchange of the cutting blade in advance. 
     In accordance with an aspect of the present invention, there is provided a processing apparatus including: a holding table for holding a workpiece; a spindle adapted to be rotated; a cutting blade mounted on the spindle, the cutting blade having a cutting edge for cutting the workpiece held on the holding table; measuring means for measuring an edge projection amount of the cutting edge at a predetermined frequency; and a data processing portion. The data processing portion includes: a lower limit recording portion for recording a lower limit of the edge projection amount of the cutting edge as an allowable limit for use of the cutting blade; a storing portion for storing blade information including the edge projection amount measured by the measuring means and a cutting distance traveled by the cutting blade at the time of measurement of the edge projection amount, the edge projection amount and the cutting distance being stored in a one-to-one correspondence manner; an inclination calculating portion for calculating an inclination such that the edge projection amount decreases with an increase in the cutting distance, from a plurality of pieces of the blade information stored in the storing portion by performing two or more measurements using the measuring means; and a predicting portion for calculating a maximum cutting distance corresponding to the lower limit of the edge projection amount from the inclination calculated by the inclination calculating portion. 
     With this configuration, the maximum cutting distance to be traveled by the cutting blade can be predicted and the operator can be informed of a guide for the timing of exchange of the cutting blade in advance. Accordingly, the workability of the operator can be improved. 
     Preferably, the inclination calculating portion performs recalculation of the inclination every time the measuring means measures the edge projection amount of the cutting blade. With this configuration, it is possible to improve the accuracy of calculation of the maximum cutting distance to be traveled by the cutting blade. 
     Preferably, the data processing portion further includes a time calculating portion for calculating the time required for cutting of the workpiece by a predetermined distance to be traveled by the cutting blade, from cutting conditions and the size of the workpiece. With this configuration, it is possible to calculate the time period until the maximum cutting distance to be traveled by the cutting blade is reached. 
     Preferably, the processing apparatus further includes displaying means for displaying blade exchange information as the timing of exchange of the cutting blade. The blade exchange information includes at least one of the cutting distance until the maximum cutting distance is reached, the time period until the maximum cutting distance is reached, the time when the maximum cutting distance is reached, and the number of workpieces that can be cut until the maximum cutting distance is reached. With this configuration, various kinds of information as a guide for the timing of exchange of the cutting blade can be provided to the operator. 
     According to the present invention, it is possible to exhibit an effect that the operator can be informed of a guide for the timing of exchange of the cutting blade in advance. 
     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 schematic perspective view depicting the configuration of a processing apparatus according to a preferred embodiment of the present invention; 
         FIG. 2  is a schematic block diagram depicting the function of an essential part of the processing apparatus depicted in  FIG. 1 ; 
         FIG. 3  is a schematic side view depicting a measuring method for an edge projection amount of a cutting blade according to the preferred embodiment; 
         FIG. 4  is a schematic block diagram depicting functional components of a data processing unit according to the preferred embodiment; 
         FIG. 5  is a table depicting an example of the lower limit of the edge projection amount of the cutting blade according to the preferred embodiment; 
         FIG. 6  is a table depicting an example of blade information according to the preferred embodiment; 
         FIG. 7  is a graph depicting an example of the relation between the edge projection amount and a cutting distance traveled by the cutting blade according to the preferred embodiment; 
         FIG. 8  is a block diagram depicting an example of blade exchange information displayed on a touch panel according to the preferred embodiment; 
         FIG. 9  is a flowchart depicting the procedure of information processing by the data processing unit according to the preferred embodiment; 
         FIG. 10  is a graph depicting the relation between the edge projection amount and the cutting distance according to a modification of the preferred embodiment; 
         FIG. 11  is a graph depicting the relation between the edge projection amount and the cutting distance according to another modification of the preferred embodiment; and 
         FIG. 12  is a side view of a cutting blade according to a further modification of the preferred embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A preferred embodiment of the present invention will now be described in detail with reference to the drawings. The present invention is not limited to the preferred embodiment. Further, the components used in the preferred embodiment may include those that can be easily assumed by persons skilled in the art or substantially the same elements as those known in the art. Further, the configurations described below may be suitably combined. Further, the configurations may be variously omitted, replaced, or changed without departing from the scope of the present invention. 
     In the following preferred embodiment, an XYZ orthogonal coordinate system is set to describe a positional relation between the components with reference to the XYZ orthogonal coordinate system. A predetermined direction in a horizontal plane is defined as an X direction depicted by an arrow X in the drawings, and a direction perpendicular to the X direction in this horizontal plane is defined as a Y direction depicted by an arrow Y in the drawings. Further, a direction perpendicular to both the X direction and the Y direction is defined as a Z direction depicted by an arrow Z in the drawings. An XY plane defined by the X direction and the Y direction is parallel to a horizontal plane. The Z direction perpendicular to the XY plane is a vertical direction. 
     The configuration of a processing apparatus  1  according to the preferred embodiment will now be described with reference to the drawings.  FIG. 1  is a schematic perspective view depicting the configuration of the processing apparatus  1 .  FIG. 2  is a schematic block diagram depicting the function of an essential part of the processing apparatus  1 . 
     The processing apparatus  1  depicted in  FIG. 1  is a cutting apparatus for cutting a workpiece  11 . The workpiece  11  is a disk-shaped wafer such as a semiconductor wafer and an optical device wafer including a substrate formed of silicon, sapphire, or gallium arsenide, for example. The workpiece  11  has a front side (upper surface as viewed in  FIG. 1 ) and a back side (lower surface as viewed in  FIG. 1 ) opposite to the front side. A plurality of crossing division lines are formed on the front side of the workpiece  11  to thereby define a plurality of separate regions where a plurality of devices are respectively formed. A circular tape  13  is attached to the back side of the workpiece  11 . The circular tape  13  has a diameter larger than that of the workpiece  11 , and a central circular portion of the tape  13  is attached to the back side of the workpiece  11 . A ring frame  15  is attached to a peripheral portion of the tape  13 . Thus, the workpiece  11  is supported through the tape  13  to the ring frame  15 . 
     In the case that the workpiece  11  includes a material that can absorb water to change characteristics, such as epoxy resin and green ceramic, the processing apparatus  1  performs a cutting operation in a dry condition where no cutting water is supplied (dry processing). 
     As depicted in  FIG. 1 , the processing apparatus  1  includes a base  4  on which various components are mounted. An X moving mechanism  6  is provided on the upper surface of the base  4 . The X moving mechanism  6  includes a pair of X guide rails  8  parallel to the X direction (work feeding direction). An X movable table  10  is slidably mounted on the pair of X guide rails  8 . 
     A nut portion (not depicted) is formed on the lower surface of the X movable table  10 , and an X ball screw  12  parallel to the X guide rails  8  is threadedly engaged with this nut portion. An X pulse motor  14  for rotating the X ball screw  12  is connected to one end of the X ball screw  12 . Accordingly, when the X ball screw  12  is rotated by the X pulse motor  14 , the X movable table  10  is moved in the X direction along the X guide rails  8 . The X moving mechanism  6  is provided with an X position measuring unit (not depicted) for measuring the X position of the X movable table  10  as the position in the X direction. 
     A table base  16  is provided on the upper surface of the X movable table  10 . A circular chuck table  18  for holding the workpiece  11  is provided through a rectangular cover table  17  on the upper surface of the table base  16 . A dressing board  19  is provided at one corner of the cover table  17 . The dressing board  19  functions to shape a cutting blade  46  (to be hereinafter described) reduced in cutting performance due to loading or dulling, thereby removing cutting dust adhering to the cutting blade  46  to recover the cutting performance of the cutting blade  46 . Thus, the operation of shaping the cutting blade  46  to thereby recover the cutting performance of the cutting blade  46  is called dressing. Further, four clamps  18   a  are provided on the outer circumference of the chuck table  18  so as to be arranged at equal intervals in the circumferential direction of the chuck table  18 . The four clamps  18   a  function to fix the ring frame  15  supporting the workpiece  11  through the tape  13 . 
     The chuck table  18  is connected to a motor (not depicted) as a rotational drive source. Accordingly, the chuck table  18  is rotatable about its vertical axis extending in the Z direction (cutter feeding direction). Further, when the X movable table  10  is moved in the X direction by the X moving mechanism  6 , the chuck table  18  is moved (fed) in the X direction. 
     The chuck table  18  has an upper surface as a holding surface  18   b  for holding the workpiece  11 . The holding surface  18   b  is substantially parallel to both the X direction and the Y direction (indexing direction). Accordingly, the holding surface  18   b  is substantially perpendicular to the Z direction. A suction passage (not depicted) is formed in the chuck table  18  and the table base  16 , and the holding surface  18   b  is connected through this suction passage to a vacuum source (not depicted). Accordingly, the workpiece  11  is held under suction on the holding surface  18   b  by using a vacuum produced by the vacuum source. This vacuum is also used to fix the chuck table  18  to the table base  16 . The dressing board  19  is supported on the upper surface of a base (not depicted), and the holding surface  18   b  is set at the same level as that of the upper surface of this base for supporting the dressing board  19 . 
     A transfer mechanism (not depicted) for transferring the workpiece  11  to the chuck table  18  is provided in the vicinity of the chuck table  18 . Further, a water case  20  is provided in the vicinity of the X movable table  10 . In the case that a cutting water such as pure water is used in cutting the workpiece  11 , the water case  20  functions to temporarily store a waste fluid including the cutting water used and cutting dust. The waste fluid stored in the water case  20  is discharged through a drain (not depicted) to the outside of the processing apparatus  1 . In the dry processing using no cutting water, the waste fluid is not stored in the water case  20 . The chuck table  18  is an example of the holding table in the present invention. 
     As depicted in  FIG. 1 , a double column type support structure  22  is provided on the upper surface of the base  4  so as to straddle the X moving mechanism  6 . Two sets of cutting unit moving mechanisms  24  for respectively moving a pair of cutting units  42  are provided on the front surface of the support structure  22  at an upper portion thereof, in which each set of cutting unit moving mechanism  24  functions as an indexing unit for moving the corresponding cutting unit  42  in the Y direction and a cutter feeding unit for moving the corresponding cutting unit  42  in the Z direction. Both of the two sets of cutting unit moving mechanisms  24  include a pair of Y guide rails  26  substantially parallel to the Y direction as an indexing direction. The pair of Y guide rails  26  are provided on the front surface of the support structure  22 . Each cutting unit moving mechanism  24  includes a Y movable plate  28  slidably mounted on the Y guide rails  26 . Each cutting unit moving mechanism  24  is an example of the moving mechanism in the present invention, and each cutting unit  42  is an example of the processing means in the present invention. 
     A nut portion (not depicted) is formed on the back side (rear surface) of the Y movable plate  28  in each cutting unit moving mechanism  24 , and a Y ball screw  30  substantially parallel to the Y guide rails  26  is threadedly engaged with this nut portion. A Y pulse motor  32  for rotating the Y ball screw  30  is connected to one end of the Y ball screw  30 . Accordingly, when the Y ball screw  30  is rotated by the Y pulse motor  32 , the Y movable plate  28  is moved in the Y direction along the Y guide rails  26 . 
     A pair of Z guide rails  34  substantially parallel to the Z direction are provided on the front side (front surface) of the Y movable plate  28  in each cutting unit moving mechanism  24 . A Z movable plate  36  is slidably mounted on the Z guide rails  34 . 
     A nut portion (not depicted) is formed on the back side (rear surface) of the Z movable plate  36 , and a Z ball screw  38  substantially parallel to the Z guide rails  34  is threadedly engaged with this nut portion. A Z pulse motor  40  for rotating the Z ball screw  38  is connected to one end of the Z ball screw  38 . Accordingly, when the Z ball screw  38  is rotated by the Z pulse motor  40 , the Z movable plate  36  is moved in the Z direction along the Z guide rails  34 . 
     Each cutting unit moving mechanism  24  is provided with a Y position measuring unit (not depicted) for measuring the Y position of the Y movable plate  28  as the position in the Y direction. Further, each cutting unit moving mechanism  24  is provided with a Z position measuring unit (not depicted) for measuring the Z position of the Z movable plate  36  as the position in the Z direction. 
     A cutting unit  42  for cutting the workpiece  11  held on the chuck table  18  is fixed to the lower end of the Z movable plate  36  in each cutting unit moving mechanism  24 . Further, a camera  44  as an imaging unit for imaging the workpiece  11  is provided adjacent to the cutting unit  42 . In each cutting unit moving mechanism  24 , the cutting unit  42  and the camera  44  are moved together in the Y direction (indexing direction) by moving the Y movable plate  28  in the Y direction, and the cutting unit  42  and the camera  44  are moved together in the Z direction (cutter feeding direction) by moving the Z movable plate  36  in the Z direction, in which the Z direction is perpendicular to the holding surface  18   b  of the chuck table  18 . 
     The X position of each of the cutting unit  42  and the camera  44  with respect to the chuck table  18  is measured by the X position measuring unit mentioned above. The Y position of each of the cutting unit  42  and the camera  44  with respect to the chuck table  18  is measured by the Y position measuring unit mentioned above. The Z position of each of the cutting unit  42  and the camera  44  with respect to the chuck table  18  or the dressing board  19  is measured by the Z position measuring unit mentioned above. 
     Each cutting unit  42  includes a spindle  43  (see  FIG. 3 ) having a rotation axis substantially parallel to the Y direction. An annular cutting blade  46  is mounted on the spindle  43  at one end portion thereof. A motor (not depicted) as a rotational drive source for rotating the spindle  43  is connected to the other end of the spindle  43 . Accordingly, the cutting blade  46  is rotated by the torque output from this motor and transmitted through the spindle  43 . The cutting blade  46  includes an annular cutting edge having a cutting area allowed to cut the workpiece  11 . The cutting blade  46  is replaceably used according to the kind of the workpiece  11 . 
     An edge position detecting unit  50  is provided below the cutting blade  46 . The edge position detecting unit  50  functions to detect the position of the edge (lower end) of the cutting blade  46  in the Z direction. Further, a cutting water nozzle  48  is provided in the vicinity of the cutting blade  46 . The cutting water nozzle  48  is used in the case of supplying a cutting water to the workpiece  11  and the cutting blade  46 . 
     As depicted in  FIG. 2 , the edge position detecting unit  50  includes a base portion  54 . The base portion  54  has a blade receiving portion  54   a  for receiving the lower end portion of the cutting blade  46 . The blade receiving portion  54   a  is a cutout formed on the upper end surface of the base portion  54  in such a manner that the lower end portion of the cutting blade  46  is adapted to enter the cutout. The blade receiving portion  54   a  has a pair of inside surfaces opposed to each other in the Y direction. A light emitting portion  56  is provided on one of the inside surfaces of the blade receiving portion  54   a , and a light receiving portion  58  is provided on the other inside surface of the blade receiving portion  54   a . The light emitting portion  56  and the light receiving portion  58  constitute an optical sensor. Thus, the light emitting portion  56  and the light receiving portion  58  are opposed to each other with the blade receiving portion  54   a  interposed therebetween. A light source  60  is connected through an optical fiber or the like to the light emitting portion  56 . A photoelectric converting portion  62  is connected through an optical fiber or the like to the light receiving portion  58 . For example, the photoelectric converting portion  62  is constituted of one or more photoelectric conversion elements and functions to convert the quantity of light transmitted from the light receiving portion  58  into a voltage and then output the voltage. 
     The X moving mechanism  6 , the chuck table  18 , the transfer mechanism, each cutting unit moving mechanism  24 , each cutting unit  42 , the camera  44 , and the edge position detecting unit  50  are all connected to a control unit  52 . As depicted in  FIG. 1 , a data processing unit  100  and a touch panel  200  are also connected to the control unit  52 . The control unit  52  functions to control each component mentioned above according to processing conditions in cutting the workpiece  11 . 
     The control unit  52  is a computer capable of executing a computer program, in which the computer includes a computing unit having a microprocessor such as a central processing unit (CPU), a storing unit having a memory such as a read only memory (ROM) and a random access memory (RAM), and an input/output interface unit. As depicted in  FIG. 2 , the control unit  52  includes a voltage comparing portion  52   a , an edge position detecting portion  52   b , a measuring portion  52   c  (an example of the measuring means in the present invention), a calculating portion  52   d , and a position correcting portion  52   e.    
     The voltage comparing portion  52   a  functions to compare the voltage output from the photoelectric converting portion  62  with any reference voltage and then output the result of this comparison to the edge position detecting portion  52   b . The edge position detecting portion  52   b  functions to detect the position of the circumferential edge (the lower end of the cutting edge)  46   a  of the cutting blade  46  according to the output from the voltage comparing portion  52   a . More specifically, when the voltage output from the photoelectric converting portion  62  has reached the above reference voltage or less (i.e., when the light quantity from the light receiving portion  58  has reached a predetermined light quantity or less), the edge position detecting portion  52   b  detects the Z position of the cutting unit  42  as the position of the edge (lower end)  46   a  of the cutting blade  46 . 
     The measuring portion  52   c  functions to measure the radius D 1  of the cutting blade  46  according to the position of the edge (lower end)  46   a  of the cutting blade  46  as detected by the edge position detecting portion  52   b  and according to a signal from each cutting unit moving mechanism  24  (Z position measuring unit). Information regarding the radius D 1  of the cutting blade  46  as measured by the measuring portion  52   c  and the position of the edge (lower end)  46   a  of the cutting blade  46  is transmitted to the calculating portion  52   d.    
     The calculating portion  52   d  functions to calculate a correction amount for the Z position of the cutting blade  46  (the cutting unit  42 ) according to the radius D 1  of the cutting blade  46  and the position of the edge  46   a  of the cutting blade  46  as informed from the measuring portion  52   c . The correction amount for the Z position of the cutting blade  46  (the cutting unit  42 ) as calculated by the calculating portion  52   d  is transmitted to the position correcting portion  52   e.    
     The position correcting portion  52   e  functions to correct the Z position of the cutting blade  46  (the cutting unit  42 ) according to the correction amount informed from the calculating portion  52   d . In this manner, the edge (lower end)  46   a  of the cutting blade  46  is detected according to a change in light quantity received by the light receiving portion  58  when the cutting blade  46  enters the blade receiving portion  54   a . This operation is called noncontact setup. 
     In the preferred embodiment, the measuring portion  52   c  included in the control unit  52  can measure an edge projection amount of the cutting blade  46  by using this noncontact setup.  FIG. 3  is a schematic side view depicting a measuring method for the edge projection amount according to the preferred embodiment. 
     As depicted in  FIG. 3 , in the measuring method for the edge projection amount, the cutting unit  42  is first positioned above the blade receiving portion  54   a  of the edge position detecting unit  50 . Thereafter, the cutting unit  42  is lowered by operating the cutting unit moving mechanism  24  until the cutting blade  46  being rotated enters the blade receiving portion  54   a . At this time, light  23  is applied from the light emitting portion  56  to the light receiving portion  58  in the edge position detecting unit  50 . That is, the cutting unit  42  is lowered while the light  23  being applied. Accordingly, the light  23  being applied from the light emitting portion  56  to the light receiving portion  58  is partially blocked by the cutting blade  46 , so that the light quantity received by the light receiving portion  58  becomes a predetermined threshold value or less. The reference voltage to be used as a threshold value in the voltage comparing portion  52   a  is set so as to correspond to this threshold value for the light quantity. 
     When the light quantity received by the light receiving portion  58  becomes the predetermined threshold value or less, the voltage output from the photoelectric converting portion  62  depicted in  FIG. 2  becomes the reference voltage or less. When the voltage output from the photoelectric converting portion  62  becomes the reference voltage or less, the edge position detecting portion  52   b  detects the Z position of the cutting unit  42  as the position of the edge (lower end)  46   a  of the cutting blade  46 . 
     As depicted in  FIG. 3 , the cutting blade  46  included in the cutting unit  42  is a so-called washer blade, and the cutting blade  46  is mounted through a mounting member  41  on the spindle  43 . The cutting blade  46  is an annular blade formed by binding abrasive grains such as diamond abrasive grains with a bond such as electroformed/electrodeposited bond, metal bond, resin bond, and vitrified bond. The mounting member  41  includes an annular mount flange  45  fixed to the front end portion of the spindle  43 , an annular pressure flange  47  opposed to the mount flange  45 , and a fixing nut  49  threadedly engaged with the pressure flange  47 . In mounting the cutting blade  46  on the spindle  43  by using the mounting member  41 , the cutting blade  46  is sandwiched between the mount flange  45  and the pressure flange  47 , and the fixing nut  49  is next tightened to the pressure flange  47 . Thus, the cutting blade  46  is fixed between the mount flange  45  and the pressure flange  47 . The mount flange  45  and the pressure flange  47  constituting the mounting member  41  have the same diameter (outer diameter) which is smaller than the diameter (outer diameter) of the cutting blade  46 . Accordingly, the cutting blade  46  projects radially outward from the outer circumferential edges of the mount flange  45  and the pressure flange  47 . The amount of projection of such a projecting portion of the cutting blade  46  is the edge projection amount. 
     The measuring portion  52   c  measures the radius D 1  of the cutting blade  46  according to the position of the edge (lower end)  46   a  of the cutting blade  46  as detected by the edge position detecting portion  52   b  and according to the signal from the cutting unit moving mechanism  24 . The radius D 1  of the cutting blade  46  corresponds to the distance from the axis of the spindle  43  to the edge (lower end)  46   a  of the cutting blade  46 . After measuring the radius D 1  of the cutting blade  46 , the measuring portion  52   c  reads out the radius D 2  of the mount flange  45 , the radius D 2  being previously stored in the memory. The radius D 2  of the mount flange  45  corresponds to the distance from the axis of the spindle  43  to the outer circumferential edge  45   a  of the mount flange  45 . Thereafter, the measuring portion  52   c  determines the difference between the radius D 1  of the cutting blade  46  and the radius D 2  of the mount flange  45 . Accordingly, the measuring portion  52   c  can measure the edge projection amount T f  as this difference between the radius D 1  and the radius D 2 . That is, the edge projection amount T f  is the width of the cutting area of the cutting edge of the cutting blade  46 , this cutting area projecting radially outward from the outer circumferential edge  45   a  of the mount flange  45 . That is, the workpiece  11  can be cut by this cutting area. The edge projection amount T f  is decreased with the use of the cutting blade  46  due to wearing of this cutting area. 
     The measurement of the edge projection amount by the edge position detecting unit  50  and the control unit  52  is performed by an operator every time a preset cutting distance is traveled by the cutting blade  46 . The edge projection amount measured by the control unit  52  and the cutting distance at the time of measurement of the edge projection amount are transmitted to the data processing unit  100 . 
     The data processing unit  100  according to the preferred embodiment will now be described with reference to  FIG. 4 .  FIG. 4  is a schematic block diagram depicting functional components of the data processing unit  100  according to the preferred embodiment. For example, the data processing unit  100  is a computer capable of executing a computer program, in which the computer includes a computing unit, a storing unit, and an input/output interface unit. The data processing unit  100  is an example of the data processing portion in the present invention. 
     The computing unit functions to compute according to the program stored in the storing unit, thereby executing various kinds of processing by the data processing unit  100 . The computing unit includes a processor such as a CPU microprocessor, a microcomputer, a digital signal processor (DSP), and a system large scale integration (LSI). 
     The storing unit functions to store a program for realizing the function for various kinds of processing to be executed by the data processing unit  100  and also store data to be used for the processing by the program. The storing unit includes a nonvolatile or volatile semiconductor memory such as a RAM, a ROM, a flash memory, an erasable programmable read only memory (EPROM), and an electrically erasable programmable read only memory (EEPROM) (registered trademark). The storing unit may be used also as a temporary working area by the processor included in the computing unit in executing the commands described in the program. The program stored in the storing unit may be called also a program product having a processor readable and non-transitory recording medium including a plurality of commands for performing data processing that can be executed by the processor included in the computing unit. 
     As depicted in  FIG. 4 , the data processing unit  100  includes a lower limit recording portion  111 , a storing portion  112 , an inclination calculating portion  113 , a predicting portion  114 , a time calculating portion  115 , and an exchange information creating portion  116 . 
     The lower limit recording portion  111  functions to record a lower limit of the edge projection amount of the cutting blade  46 . That is, the lower limit recording portion  111  functions to record an allowable limit of the edge projection amount of the cutting blade  46  for use in cutting the workpiece  11 .  FIG. 5  is a table depicting an example of the lower limit of the edge projection amount of the cutting blade  46 . The lower limit recording portion  111  is an example of the lower limit recording portion in the present invention. 
     As depicted in  FIG. 5 , the lower limit recording portion  111  includes an item for a blade ID and an item for the lower limit of the edge projection amount and records data in the item for the lower limit of the edge projection amount in correspondence with data in the item for the blade ID. The lower limit of the edge projection amount is decided according to cutting conditions. For example, when the depth of cut in the workpiece  11  is 1.5 mm, the lower limit of the edge projection amount is decided to a value of 2.0 mm obtained by adding a predetermined allowance of 0.5 mm to 1.5 mm as the depth of cut. 
     The storing portion  112  functions to store the edge projection amount measured by the measuring portion  52   c  (the edge position detecting unit  50  and the control unit  52 ) in correspondence with the cutting distance traveled by the cutting blade  46  at the time of measurement of the edge projection amount. That is, the edge projection amount measured and the cutting distance are stored in a one-to-one correspondence manner as blade information.  FIG. 6  is a table depicting an example of the blade information according to the preferred embodiment. The storing portion  112  is an example of the storing portion in the present invention. 
     As depicted in  FIG. 6 , the blade information to be stored by the storing portion  112  includes an item for the measured values for the edge projection amount and an item for the cutting distance, in which data in these items corresponds to each other. The storing portion  112  obtains the edge projection amount and the cutting distance from the control unit  52  (the measuring portion  52   c ) and then stores the edge projection amount and the cutting distance in a one-to-one correspondence manner. 
     The inclination calculating portion  113  functions to calculate an inclination such that the edge projection amount decreases with an increase in the cutting distance, from a plurality of pieces of blade information stored in the storing portion  112  by performing two or more measurements using the measuring portion  52   c  (the edge position detecting unit  50  and the control unit  52 ).  FIG. 7  is a graph depicting an example of the relation between the edge projection amount and the cutting distance. The inclination calculating portion  113  is an example of the inclination calculating portion in the present invention. The inclination calculating portion  113  obtains a predetermined number of pieces of blade information d 1  to d 8  from the plurality of pieces of blade information stored in the storing portion  112  and then determines a linear function f 1  depicting the relation that the edge projection amount decreases with an increase in the cutting distance, by using a method of least squares, for example. The slope of the line depicting the linear function f 1  calculated by the inclination calculating portion  113  corresponds to the inclination that the edge projection amount decreases with an increase in the cutting distance. 
     The predicting portion  114  functions to calculate a maximum cutting distance at which the edge projection amount of the cutting blade  46  reaches a lower limit, from the slope calculated by the inclination calculating portion  113 . More specifically, the predicting portion  114  uses the slope of the line depicting the linear function f 1  calculated by the inclination calculating portion  113 , thereby calculating a cutting distance (maximum cutting distance L max1 ) at which the edge projection amount of the cutting blade  46  reaches a lower limit t z . That is, the maximum cutting distance L max1  corresponds to the lower limit t z  of the edge projection amount. The predicting portion  114  is an example of the predicting portion in the present invention. 
     The time calculating portion  115  functions to calculate the time required for cutting of the workpiece  11  by a predetermined distance to be traveled by the cutting blade  46 , from the cutting conditions and the size of the workpiece  11 . For example, the time calculating portion  115  may calculate a remaining cutting distance up to the maximum cutting distance calculated by the predicting portion  114  and then calculate a remaining time period until the maximum cutting distance is reached, according to the above-calculated remaining cutting distance and a cutting speed. The time calculating portion  115  is an example of the time calculating portion in the present invention. 
     The exchange information creating portion  116  functions to create blade exchange information as a guide for exchange timing with which the cutting blade  46  is to be exchanged. For example, the exchange information creating portion  116  may create the blade exchange information including at least one of the maximum cutting distance calculated by the predicting portion  114 , the remaining time period until the maximum cutting distance is reached as calculated by the time calculating portion  115 , and the number of workpieces  11  that can be cut until the maximum cutting distance is reached. The remaining time period until the maximum cutting distance is reached may be converted into the time when the maximum cutting distance is reached. The remaining time period until the maximum cutting distance is reached may be converted into the number of workpieces  11  that can be cut until the maximum cutting distance is reached. The number of workpieces  11  that can be cut until the maximum cutting distance is reached includes the number of wafers that can be cut or the number of cassettes storing the wafers that can be cut. That is, the remaining time period until the maximum cutting distance is reached can be converted into the number of workpieces  11  that can be cut until the maximum cutting distance is reached, according to information regarding the number of workpieces  11  that can be cut per unit time. The blade exchange information created by the exchange information creating portion  116  is sent to the touch panel  200 . 
     The touch panel  200  functions to display various kinds of information relating to the processing apparatus  1 . The touch panel  200  is adapted to receive from the operator various kinds of operation inputs relating to the processing apparatus  1 , such as an input for setting of the cutting conditions. For example, the touch panel  200  displays the blade exchange information sent from the data processing unit  100 . The touch panel  200  is an example of the displaying means in the present invention. 
       FIG. 8  is a block diagram depicting an example of the blade exchange information displayed on the touch panel  200 . As depicted in  FIG. 8 , the touch panel  200  includes a blade exchange information displaying area  210  for displaying the blade exchange information and an EXIT button  220  for ending the display of the blade exchange information. The blade exchange information displaying area  210  displays the information regarding the cutting distance until exchange, the time period until exchange, the exchange time, the number of wafers that can be cut, and the number of cassettes that can be loaded. While the blade exchange information displaying area  210  displays all of the cutting distance until exchange, the time period until exchange, the exchange time, the number of wafers that can be cut, and the number of cassettes that can be loaded as depicted in  FIG. 8 , at least one of these items may be actually displayed in the blade exchange information displaying area  210 . The blade exchange information to be displayed in the blade exchange information displaying area  210  may be changed according to setting by the operator. 
     The procedure of information processing by the data processing unit  100  will now be described with reference to  FIG. 9 .  FIG. 9  is a flowchart depicting the procedure of information processing by the data processing unit  100 . The information processing depicted in  FIG. 9  is performed by the above-mentioned portions of the data processing unit  100 . As depicted in  FIG. 9 , the inclination calculating portion  113  obtains a predetermined number of pieces of blade information from the plurality of pieces of blade information stored in the storing portion  112  (step S 101 ). 
     Thereafter, the inclination calculating portion  113  calculates the inclination that the edge projection amount of the cutting blade  46  decreases with an increase in the cutting distance traveled by the cutting blade  46 , from the blade information obtained in step S 101  (step S 102 ). More specifically, the inclination calculating portion  113  determines a linear function depicting the relation between the cutting distance increasing and the edge projection amount decreasing, from the blade information obtained from the storing portion  112 , by using a method of least squares, for example. 
     Thereafter, the predicting portion  114  calculates a maximum cutting distance corresponding to a lower limit of the edge projection amount, from the inclination calculated by the inclination calculating portion  113  (step S 103 ). More specifically, the predicting portion  114  calculates the cutting distance corresponding to the lower limit of the edge projection amount, by using the linear function determined by the inclination calculating portion  113  (i.e., by using the slope of the line depicting the linear function). Thereafter, the time calculating portion  115  calculates the time period until the maximum cutting distance calculated by the predicting portion  114  is reached (step S 104 ). 
     Thereafter, the exchange information creating portion  116  creates blade exchange information according to the maximum cutting distance and the time period until the maximum cutting distance is reached (step S 105 ), and then transmits the blade exchange information created above to the touch panel  200  (step S 106 ). In this manner, the processing depicted in  FIG. 9  is finished. In the case that the maximum cutting distance is transmitted to the touch panel  200  and displayed on the touch panel  200 , the creation of the blade exchange information may be omitted. 
     As described above, the processing apparatus  1  according to the preferred embodiment includes the chuck table  18  for holding the workpiece  11 , the cutting blade  46  mounted on the rotatable spindle  43  and including a cutting edge having a cutting area allowed to cut the workpiece  11 , the measuring portion  52   c  for measuring the edge projection amount of the cutting blade  46  at a predetermined frequency, and the data processing unit  100 . The data processing unit  100  includes the lower limit recording portion  111 , the storing portion  112 , the inclination calculating portion  113 , and the predicting portion  114 . The lower limit recording portion  111  records the lower limit of the edge projection amount of the cutting blade  46 . The storing portion  112  stores the blade information composed of the edge projection amount measured by the measuring portion  52   c  and the cutting distance traveled by the cutting blade  46  at the time of measurement of the edge projection amount, in which the edge projection amount and the cutting distance are stored in a one-to-one correspondence manner. The inclination calculating portion  113  calculates the inclination such that the edge projection amount decreases with an increase in the cutting distance, from a plurality of pieces of blade information stored in the storing portion  112  by performing two or more measurements using the measuring portion  52   c . The predicting portion  114  calculates a maximum cutting distance corresponding to the lower limit of the edge projection amount from the inclination calculated above. 
     Accordingly, the processing apparatus  1  according to the preferred embodiment can predict the maximum cutting distance to be traveled by the cutting blade  46  and can inform the operator of a guide for the timing of exchange of the cutting blade  46  in advance. As a result, the workability of the operator can be improved. 
     Further, the data processing unit  100  further includes the time calculating portion  115  for calculating the time required for cutting of the workpiece  11  by a predetermined distance to be traveled by the cutting blade  46 , from cutting conditions and the size of the workpiece  11 . Accordingly, the processing apparatus  1  according to the preferred embodiment can predict the time period until the maximum cutting distance to be traveled by the cutting blade  46  is reached and can inform the operator of a guide for the timing of exchange of the cutting blade  46  in advance. As a result, the workability of the operator can be improved. 
     Further, the processing apparatus  1  according to the preferred embodiment further includes the touch panel  200  for displaying blade exchange information as the timing of exchange of the cutting blade  46 . The blade exchange information includes at least one of the cutting distance until the maximum cutting distance is reached, the time period until the maximum cutting distance is reached, the time when the maximum cutting distance is reached, and the number of workpieces  11  that can be cut until the maximum cutting distance is reached. 
     Accordingly, the processing apparatus  1  according to the preferred embodiment can provide various kinds of information to the operator as a guide for the timing of blade exchange. As a result, the workability of the operator can be improved. 
     As a modification, the processing apparatus  1  may further include an operation selecting window (not depicted) for operating a control unit included in another processing apparatus  1 . With this configuration, the operator can operate the other processing apparatus  1  from the processing apparatus  1 , thereby improving the workability. 
     Modifications of the Preferred Embodiment 
     The inclination calculating portion  113  of the data processing unit  100  may perform recalculation of the inclination every time the measuring portion  52   c  measures the edge projection amount of the cutting blade  46 .  FIG. 10  is a graph depicting the relation between the edge projection amount and the cutting distance according to a modification of the preferred embodiment. 
     The inclination calculating portion  113  calculates the inclination (linear function f 2 ) depicting the relation between the cutting distance increasing and the edge projection amount decreasing, from blade information d 11  to d 18  stored in the storing portion  112 . The predicting portion  114  determines a maximum cutting distance (L max2 ) corresponding to the lower limit t z  of the edge projection amount of the cutting blade  46 , from the inclination (linear function f 2 ) calculated by the inclination calculating portion  113  (ST 1  in  FIG. 10 ). 
     Thereafter, the measurement of the edge projection amount is performed again by the measuring portion  52   c , and new blade information d 19  is stored into the storing portion  112 . Then, the inclination calculating portion  113  obtains blade information d 11  to d 19  including the new blade information dig from the storing portion  112  and next calculates the inclination (linear function f 3 ) depicting the relation between the cutting distance increasing and the edge projection amount decreasing, from the blade information d 11  to d 19 . Thereafter, the predicting portion  114  determines a maximum cutting distance (L max3 ) corresponding to the lower limit t z  of the edge projection amount of the cutting blade  46 , from the inclination (linear function f 3 ) calculated by the inclination calculating portion  113  (ST 2  in  FIG. 10 ). 
     In general, the edge projection amount of the cutting blade  46  decreases with an increase in wearing amount of the cutting blade  46 . That is, the outer diameter of the cutting blade  46  decreases (i.e., the outer circumference of the cutting blade  46  becomes shorter) with an increase in wearing amount of the cutting blade  46 . Thus, the cutting amount of the cutting blade  46  (i.e., the amount of the workpiece  11  to be cut by the cutting blade  46 ) is increased and a wearing rate is also increased. Accordingly, it is estimated that the inclination (e.g., the slope of the line depicting the linear function f 3 ) calculated by the inclination calculating portion  113  in the case of adding the new blade information (e.g., the blade information d 19 ) becomes steeper than the previous inclination (e.g., the slope of the line depicting the linear function f 2 ). As a result, it is estimated that the maximum cutting distance (e.g., L max3 ) based on the inclination calculated in the case of adding the new blade information becomes shorter than the previous maximum cutting distance (e.g., L max2 ). 
     In consideration of this estimation, the inclination calculating portion  113  in the data processing unit  100  performs recalculation of the inclination (linear function) every time the measuring portion  52   c  measures the edge projection amount. Accordingly, the processing apparatus  1  can improve the accuracy of calculation of the maximum cutting distance of the cutting blade  46 . 
     As another modification, in performing the recalculation of the inclination (linear function) by the data processing unit  100 , a predetermined number of pieces of blade information before the new blade information may be obtained rather than using all pieces of the blade information including the new blade information. For example, in the case that the number of pieces of blade information to be obtained is set to “8” in the example of  FIG. 10 , the inclination calculating portion  113  obtains blade information d 12  to d 19  from the storing portion  112  and next calculates the inclination depicting the relation between the cutting distance increasing and the edge projection amount decreasing, from the blade information d 12  to d 19 . 
     As another modification, every time the recalculation of the inclination (linear function) is performed, the data processing unit  100  may recalculate a maximum cutting distance and the time period until the maximum cutting distance is reached, thereby creating new blade exchange information and displaying this new blade exchange information on the touch panel  200 . 
     As another modification, the inclination calculating portion  113  in the data processing unit  100  may extract a last half portion of the blade information from the plurality of pieces of blade information stored in time sequence in the storing portion  112 , and next calculate the inclination (linear function) from the last half portion of the blade information, thereby determining a maximum cutting distance.  FIG. 11  is a graph depicting the relation between the edge projection amount and the cutting distance according to the modification. 
     As depicted in  FIG. 11 , a plurality of pieces of blade information d 21  to d 28  are stored in the storing portion  112 . The inclination calculating portion  113  extracts a last half portion d 25  to d 28  from the blade information d 21  to d 28 . Thereafter, the inclination calculating portion  113  calculates the inclination (linear function f 4 ) depicting the relation between the cutting distance increasing and the edge projection amount decreasing, from the blade information d 25  to d 28 . Thereafter, the predicting portion  114  calculates a maximum cutting distance (L max4 ) corresponding to the lower limit t z  of the edge projection amount of the cutting blade  46 , from the inclination (the slope of the line depicting the linear function f 4 ) calculated by the inclination calculating portion  113 . 
     In this manner, the data processing unit  100  calculates the inclination (e.g., the slope of the line depicting the linear function f 4 ) from a predetermined number of pieces of blade information as a last half portion of the blade information stored in the storing portion  112  and then determines the maximum cutting distance (e.g., L max4 ) corresponding to the lower limit t z  of the edge projection amount of the cutting blade  46 . Accordingly, the processing apparatus  1  can derive the inclination depicting the relation between the cutting distance increasing and the edge projection amount decreasing, by using a minimum number of data samples extracted from a plurality of pieces of blade information stored in time sequence. As a result, the accuracy of calculation of the maximum cutting distance of the cutting blade  46  can be improved. 
     While the cutting blade  46  included in the cutting unit  42  in the preferred embodiment is a so-called washer blade, the present invention is not limited to this configuration. That is, the cutting blade usable in the present invention may be a so-called hub blade. In this case, the processing apparatus  1  can also measure the edge projection amount of this hub blade in a manner similar to that for the cutting blade  46  as a washer blade. Further, the data processing unit  100  can create blade exchange information for such a cutting blade as a hub blade in a manner similar to that for the cutting blade  46  as a washer blade and then provide this blade exchange information to the operator.  FIG. 12  is a side view of such a cutting blade as a hub blade according to the modification. 
     As depicted in  FIG. 12 , the cutting unit  42  includes a cutting blade  71  as a so-called hub blade. The cutting blade  71  is constituted of a blade portion  73  and a hub portion  75  integrated with each other. The blade portion  73  is an annular cutting wheel having a very small thickness. The blade portion  73  is an annular blade formed by binding abrasive grains such as diamond abrasive grains with an electroformed/electrodeposited bond. The blade portion  73  projects radially outward from the outer circumferential edge of the hub portion  75 . The hub portion  75  is an annular plate-shaped member. The cutting blade  71  is mounted on the spindle  43  through a mounting member  77 . The mounting member  77  includes a mount flange  77   a  fixed to the front end portion of the spindle  43  and a fixing nut  77   b  threadedly engaged with the mount flange  77   a . In mounting the cutting blade  71  to the spindle  43  by using the mounting member  77 , the hub portion  75  of the cutting blade  71  is sandwiched between the mount flange  77   a  and the fixing nut  77   b , and the fixing nut  77   b  is next tightened to the mount flange  77   a , thereby fixing the cutting blade  71  to the spindle  43 . 
     The measuring portion  52   c  measures the radius D 3  of the cutting blade  71  according to the position of the edge (lower end)  73   a  of the blade portion  73  of the cutting blade  71  as detected by the edge position detecting portion  52   b  and according to the signal from the cutting unit moving mechanism  24 . The radius D 3  of the cutting blade  71  corresponds to the distance from the axis of the spindle  43  to the edge (lower end)  73   a  of the blade portion  73  of the cutting blade  71 . After measuring the radius D 3  of the cutting blade  71 , the measuring portion  52   c  reads out the radius D 4  of the hub portion  75 , the radius D 4  being previously stored in the memory. The radius D 4  of the hub portion  75  corresponds to the distance from the axis of the spindle  43  to the outer circumferential edge  75   a  of the hub portion  75 . The measuring portion  52   c  next determines a difference between the radius D 3  of the cutting blade  71  and the radius D 4  of the hub portion  75 . This difference corresponds to an edge projection amount T h . Thus, the measuring portion  52   c  can measure the edge projection amount T h  as the width of a cutting area of the cutting edge of the cutting blade  71 , the cutting area projecting radially outward from the outer circumferential edge  75   a  of the hub portion  75 . 
     Thereafter, the inclination calculating portion  113  in the data processing unit  100  calculates the inclination (the slope of a line depicting a linear function) depicting the relation between the cutting distance increasing and the edge projection amount decreasing, according to the edge projection amount of the cutting blade  71  as measured by the measuring portion  52   c . Thereafter, the predicting portion  114  in the data processing unit  100  determines a maximum cutting distance corresponding to the lower limit of the edge projection amount of the cutting blade  71 , from the inclination (the slope of the line depicting the linear function) as calculated above. Thereafter, blade exchange information is created by using this maximum cutting distance and then displayed on the touch panel  200 . That is, the blade exchange information is provided to the operator. 
     Other Preferred Embodiments 
     The processing apparatus  1  according to the present invention is not limited to the above preferred embodiment, but various modifications may be made without departing from the scope of the present invention. For example, the processing by the data processing unit  100  included in the processing apparatus  1  according to the present invention may be performed by an information processing apparatus such as a server adapted to be connected through a communication network to the processing apparatus  1 . 
     Each component of the processing apparatus  1  is merely functional and conceptual, and it is not always necessary to configure each component physically as depicted in the drawings. That is, a specific embodiment of dispersion and unification in the processing apparatus  1  is not limited to that depicted in the drawings, but the whole or part of the processing apparatus  1  may be dispersed or unified functionally or physically in any unit according to various loads or use conditions. For example, the inclination calculating portion  113 , the predicting portion  114 , the time calculating portion  115 , and the exchange information creating portion  116  in the data processing unit  100  may be suitably united functionally or physically according to the content of information processing. Further, the control unit  52  and the data processing unit  100  may be united functionally or physically. For example, the processing function to be realized by the data processing unit  100  may be incorporated into the control unit  52 . 
     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.