JP7325904B2 - Cutting unit position detection method and cutting device - Google Patents

Description

The present invention provides a cutting apparatus having a cutting unit equipped with a cutting blade for cutting a workpiece, wherein the height position of the cutting unit is set when the lower end of the cutting edge of the cutting blade is positioned at a predetermined height position. The present invention relates to a position detection method for a cutting unit to be detected. The present invention also relates to a cutting apparatus capable of implementing the position detection method for the cutting unit.

A device chip on which a semiconductor device is mounted is formed from a semiconductor wafer, a package substrate, a ceramic substrate, a glass substrate, or the like. A plurality of intersecting planned division lines are set on the surface of a semiconductor wafer or the like, semiconductor devices are formed in respective regions partitioned by the planned division lines, and then the semiconductor wafer or the like is divided along the planned division lines to obtain individual devices. device chip can be formed.

A cutting device having a cutting unit equipped with an annular cutting blade, for example, is used to divide a semiconductor wafer or the like. The cutting device rotates a cutting blade in a plane perpendicular to the surface of a workpiece such as a semiconductor wafer, positions the lower end of the blade tip of the rotating cutting blade at a predetermined height position, and divides the workpiece. The workpiece is cut by feeding in the direction along the line.

When the cutting device repeatedly cuts the workpiece, the annular cutting blade gradually wears and the diameter of the cutting blade gradually decreases. Then, the height of the lower end of the cutting edge of the cutting blade gradually deviates from the predetermined height position, and the depth of cut changes. Therefore, a setup step is performed to detect the height position of the cutting unit when the lower end of the cutting edge of the cutting blade is positioned at a predetermined height. A cutting edge position detection unit is used in the setup process (see Patent Document 1, for example).

The cutting edge position detection unit has a main body with a groove-like blade entry portion that is open upward and forward and backward. A light-emitting window of the light-emitting portion is provided on one side wall of the blade entry portion, and a light-receiving window of the light-receiving portion is provided on the other side wall. The light emitting window and the light receiving window are provided at substantially the same height position.

In the setup step, the cutting unit is lowered to allow the cutting edge of the cutting blade to enter the blade entry portion while light is emitted from the light emitting window of the light emitting portion toward the light receiving window of the light receiving portion. Then, since part of the light is blocked by the cutting blade, the amount of light received by the light receiving portion is reduced. Then, the height of the cutting unit is detected when the amount of received light reaches the reference amount of received light, that is, when the lower end of the cutting edge of the cutting blade is positioned at a predetermined height.

Japanese Patent Application Laid-Open No. 2001-298001

When the cutting blade is rotated at high speed, the diameter of the cutting blade slightly increases due to the centrifugal force generated by the rotation. Therefore, in the setup process, for example, it is conceivable to rotate the cutting blade at the same speed as when cutting the workpiece. In this case, the set-up process is performed with the same centrifugal force applied to the cutting blade as during cutting of the workpiece.

When cutting a workpiece, cutting water is sprayed onto the cutting blade and the workpiece in order to remove machining heat and machining waste. Therefore, the temperature of the cutting blade that cuts the workpiece is kept constant. On the other hand, cutting water is not supplied to the cutting blade during the setup process because it interferes with detection of the cutting edge of the cutting blade. In this case, during the setup process, the temperature of the cutting blade gradually rises due to frictional heat between the rotating cutting blade and air, and the cutting blade thermally expands.

In recent years, the number of revolutions of cutting blades has been increased in order to improve the cutting speed, and the number of revolutions has reached about 80 krpm to 100 krpm. Also, it is desirable to rotate the cutting blade at the same speed when performing the set-up process. However, when the rotation speed of the cutting blade is increased, the frictional heat between the air and the cutting blade increases, the temperature of the cutting blade becomes higher than before, and the thermal expansion of the cutting blade cannot be ignored. Moreover, the amount of thermal expansion is not constant, and the longer the set-up process takes, the greater the thermal expansion.

Thus, the diameter of the cutting blade during the setup process becomes larger than the diameter of the workpiece during cutting due to the influence of thermal expansion. If the cutting blade is greatly thermally expanded when the setup process is performed, the height position of the cutting unit detected by performing the setup process will not match the height position that should be detected. Therefore, when the cutting unit is positioned at the cutting reference height based on the reference height detected in the setup process and the workpiece is cut, the cutting depth of the cutting blade becomes shallow, and the workpiece can be properly cut. Can not.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and an object of the present invention is to provide a cutting unit position detection method and a cutting apparatus that can appropriately perform a setup process.

According to one aspect of the present invention, a chuck table that holds a workpiece on a holding surface, a spindle extending in a direction parallel to the holding surface, and a cutting blade attached to the tip of the spindle, a cutting unit that cuts the workpiece with the cutting blade that rotates around the spindle while supplying cutting water to the workpiece and the cutting blade held on the chuck table; a cutting feed unit that feeds the cutting unit in a cutting feed direction; a cutting edge position detection unit that detects the height position of the lower end of the cutting edge of the cutting blade; and a control unit that controls each component, The cutting edge position detection unit includes a blade entry portion into which the cutting blade enters, and a light emitting portion and a light receiving portion facing each other across the blade entry portion. A position detection method for a cutting unit using a cutting device having a relationship registration unit capable of registering changes over time in the amount of light received, wherein the cutting feed unit detects the blade entrance portion of the cutting edge position detection unit. a cutting blade positioning step of advancing a cutting blade and positioning the cutting blade at a height at which a predetermined amount of light emitted by the light emitting portion and received by the light receiving portion is blocked; and after the cutting blade positioning step, the cutting unit While maintaining the height in the cutting feed direction, the amount of light received that changes with time due to thermal expansion of the rotating cutting blade is observed, and the time from the start of observation and the amount of change in the amount of light received a relationship registration step of registering a relationship in the relationship registration unit; The cutting blade is positioned at a height at which the light emitted by the light emitting portion and received by the light receiving portion is blocked by the predetermined amount, and the height of the lower end of the cutting edge of the cutting blade is the predetermined height. a height position detection step of determining the height position of the cutting unit when it reaches the height position as a reference height position, and in the height position detection step, the lower end of the cutting edge of the cutting blade is positioned at the predetermined height. A correction amount for the reference height position of the cutting unit is determined from the relationship registered in the relationship registration unit with reference to the time when it is detected that the cutting unit is positioned at the height position, and the calculated cutting A position detection method for a cutting unit is provided, characterized by correcting the reference height position of the unit with the correction amount .

Preferably, in the relationship registration step, the cutting blade is rotated at a rotation speed corresponding to the rotation speed of the cutting blade in the height position detection step.

According to another aspect of the present invention, a chuck table for holding a workpiece on a holding surface, a spindle extending in a direction parallel to the holding surface, a cutting blade attached to the tip of the spindle, a cutting unit for cutting the workpiece with the cutting blade rotating around the spindle while supplying cutting water to the workpiece and the cutting blade held on the chuck table; A cutting feed unit that feeds the cutting unit in a cutting feed direction orthogonal to the plane, and a height position of the cutting unit when the lower end of the cutting edge of the cutting blade reaches a predetermined height position are used as a reference height position. A cutting edge position detection unit for detecting and a control unit for controlling each component. The cutting edge position detection unit includes a blade entry portion into which the cutting blade enters and light emitting beams facing each other across the blade entry portion. and a light receiving portion, and a photoelectric conversion portion for outputting an electric signal having a voltage value corresponding to the amount of light received by the light receiving portion. a relation registering unit capable of registering changes over time in the amount of light received by the unit as changes over time in the voltage value of the electrical signal output from the photoelectric conversion unit; reference voltage value registration in which the voltage value of the electrical signal output from the photoelectric conversion unit when the light emitted from the light emitting unit is received by the light receiving unit is registered as the reference voltage value and when the voltage value of the electrical signal output from the photoelectric conversion unit matches the reference voltage value registered in the reference voltage value registration unit, the lower end of the cutting edge of the cutting blade is positioned at the predetermined height. a voltage value comparison unit connected to the voltage value comparison unit for detecting that the lower end of the cutting edge of the cutting blade is positioned at the predetermined height position; A cutting unit height detection unit that detects the height of the cutting unit at the time of detection as the reference height position, and a correction that corrects the reference height position of the cutting unit detected by the cutting unit height detection unit. and the relationship registration unit registers the relationship between the voltage value of the electrical signal output by the photoelectric conversion unit that changes with time due to the thermal expansion of the rotating cutting blade, and the time. The correction unit refers to the time when the voltage value comparison unit detects that the lower end of the cutting edge of the cutting blade is positioned at the predetermined height position, and registers the relationship in the relationship registration unit. A cutting apparatus is provided, wherein a correction amount for the reference height position of the cutting unit is determined from the established relationship.

In the cutting unit position detection method and the cutting apparatus according to one aspect of the present invention, the tendency that the amount of light received by the light receiving section of the cutting edge position detection unit changes with time due to the thermal expansion of the cutting blade is stored in the relationship registration section. Registered. More specifically, the relationship between time and the amount of change in the amount of received light is registered in the relationship registration section.

Then, when the height position of the cutting unit when the lower end of the cutting edge of the cutting blade reaches a predetermined height position is determined as the reference height position by the cutting edge position detection unit, the cutting unit indexed using this relationship. Correct the reference height position. More specifically, the reference height position of the cutting unit, which is determined when the cutting blade is thermally expanded, is corrected by a value corresponding to the amount of expansion of the cutting blade, so that the reference of the cutting unit that should be determined is corrected. Calculate the height position.

The calculated reference height position of the cutting unit that should be indexed is the height of the cutting unit when the lower end of the cutting edge of the cutting blade reaches the predetermined height position when the cutting blade does not thermally expand. position. By positioning the cutting unit at the height calculated based on the corrected reference height position, the workpiece can be cut appropriately.

Therefore, according to one aspect of the present invention, there are provided a cutting unit position detection method and a cutting apparatus that can appropriately perform a setup process.

It is a perspective view which shows a cutting device typically. FIG. 2(A) is a perspective view schematically showing a cutting edge position detection unit, and FIG. 2(B) is a configuration diagram schematically showing a cutting unit, a cutting edge position detection unit, and a control unit. be. FIG. 3(A) is a graph schematically showing the relationship between the voltage value of the electrical signal corresponding to the amount of light received when the cutting blade enters the blade entry portion and the time, and FIG. ) is a graph schematically showing the relationship between the voltage value of an electrical signal corresponding to the amount of change in the amount of light received by a cutting blade whose diameter changes due to thermal expansion, and time. 4 is a flow chart schematically showing the flow of each step of a cutting unit position detection method.

An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. First, with reference to FIG. 1, a cutting apparatus in which the method for detecting the position of the cutting unit according to the present embodiment is implemented will be described. FIG. 1 shows a workpiece such as a substantially disk-shaped substrate made of materials such as silicon, silicon carbide (SiC), gallium arsenide (GaAs), or other semiconductors, or materials such as sapphire, glass, or quartz. is a cutting device 2 for cutting.

A plurality of devices such as ICs (Integrated Circuits) are formed on the surface of the workpiece. Finally, individual device chips are formed by dividing the workpiece for each device. For example, the workpiece is cut while attached to a tape stretched over an annular frame. When the workpiece is properly cut, the lower end of the cutting edge of the cutting blade, which will be described later, reaches the tape.

As shown in FIG. 1, the cutting device 2 includes a device base 4 that supports each component. An X-axis moving table 6, an X-axis moving mechanism for moving the X-axis moving table 6 in the X-axis direction (processing feed direction), and a drainage channel 20 covering the X-axis moving mechanism are provided at the upper center of the apparatus base 4. , is provided. The X-axis moving mechanism has a pair of X-axis guide rails 12 parallel to the X-axis direction, and an X-axis moving table 6 is slidably attached to the X-axis guide rails 12 .

A nut portion (not shown) is provided on the lower surface side of the X-axis moving table 6, and an X-axis ball screw 14 parallel to the X-axis guide rail 12 is screwed into this nut portion. An X-axis pulse motor 16 is connected to one end of the X-axis ball screw 14 . When the X-axis ball screw 14 is rotated by the X-axis pulse motor 16, the X-axis moving table 6 moves along the X-axis guide rail 12 in the X-axis direction.

A chuck table 8 for sucking and holding a workpiece is provided on the X-axis moving table 6 . The chuck table 8 is connected to a rotation drive source (not shown) such as a motor, and is rotatable around a rotation axis perpendicular to the upper surface of the chuck table 8 . Also, the chuck table 8 is fed in the X-axis direction by the X-axis moving mechanism described above.

The surface (upper surface) of the chuck table 8 serves as a holding surface 8a for sucking and holding the workpiece. The holding surface 8a is connected to a suction source (not shown) through a channel (not shown) formed inside the chuck table 8. As shown in FIG. A clamp 10 is arranged around the holding surface 8a for fixing an annular frame holding the workpiece via a tape.

A support structure 22 for supporting two cutting units 18 for cutting a workpiece is arranged on the upper surface of the device base 4 so as to straddle the X-axis movement mechanism. An index feed unit for moving the two cutting units 18 in the Y-axis direction (index feed direction) and a cutting feed unit for moving the two cutting units 18 in the Z-axis direction (cut feed direction) are provided on the upper front surface of the support structure 22. ing.

A pair of Y-axis guide rails 24 parallel to the Y-axis direction are provided on the front surface of the support structure 22 . Two Y-axis movement plates 26 corresponding to the cutting units 18 are slidably attached to the Y-axis guide rail 24 . A nut portion (not shown) is provided on the back side (rear side) of each Y-axis moving plate 26, and a Y-axis ball screw 28 parallel to the Y-axis guide rail 24 is screwed into this nut portion. are combined.

One end of the Y-axis ball screw 28 is connected to a Y-axis pulse motor 28a. When the Y-ball screw 28 is rotated by the Y-axis pulse motor 28a, the corresponding Y-axis moving plate 26 moves along the Y-axis guide rail 24 in the Y-axis direction. That is, the Y-axis guide rail 24, the Y-axis moving plate 26, the Y-axis ball screw 28, and the Y-axis pulse motor 28a constitute an indexing feed unit.

A pair of Z-axis guide rails 30 parallel to the Z-axis direction is provided on the surface (front surface) of each Y-axis moving plate 26 . A Z-axis movement plate 32 is slidably attached to each Z-axis guide rail 30 . A nut portion (not shown) is provided on the back side (rear side) of the Z-axis moving plate 32, and a Z-axis ball screw 34 parallel to the Z-axis guide rail 30 is screwed into this nut portion. ing. A Z-axis pulse motor 36 is connected to one end of the Z-axis ball screw 34 .

When the Z-axis ball screw 34 is rotated by the Z-axis pulse motor 36, the Z-axis moving plate 32 moves along the Z-axis guide rail 30 in the Z-axis direction (infeed direction). That is, the Z-axis guide rail 30, the Z-axis moving plate 32, the Z-axis ball screw 34, and the Z-axis pulse motor 36 constitute a cutting feed unit.

A cutting unit 18 that processes a workpiece and an imaging unit (camera) 38 that can capture an image of the workpiece held on the chuck table 8 are fixed below each of the two Z-axis movement plates 32 . there is When the Y-axis moving plate 26 is moved in the Y-axis direction, the cutting unit 18 and the imaging unit 38 are moved in the Y-axis direction (index feed direction), and when the Z-axis moving plate 32 is moved in the Z-axis direction, The cutting unit 18 and imaging unit 38 move in the Z-axis direction (infeed direction).

The cutting unit 18 includes a spindle 18c (see FIG. 2B) along the Y-axis direction parallel to the holding surface 8a of the chuck table 8, and an annular cutting blade 18a attached to the tip of the spindle 18c. (See FIG. 2B). A rotary drive source (not shown) such as a motor is connected to the other end of the spindle 18c. When the rotary drive source is operated to rotate the spindle 18c, the cutting blade 18a rotates around the spindle 18c. do.

The cutting blade 18a has, for example, a disk-shaped base. A substantially circular mounting hole is provided in the central portion of the base and passes through the base. When the cutting blade 18a is mounted on the cutting unit 18, the tip of the spindle 18c is passed through the mounting hole. . An annular cutting edge for cutting into the workpiece held on the chuck table 8 is fixed to the outer peripheral portion of the base. The cutting edge is also called a grindstone portion. The cutting edge has abrasive grains such as diamond, and a binding material that disperses and fixes the abrasive grains. The binding material is made of, for example, metal or resin.

When cutting a workpiece, the imaging unit 38 detects the devices, patterns, etc. formed on the surface of the workpiece in advance, thereby recognizing the position of the planned division line set on the surface of the workpiece. be done. Then, the chuck table 8 is rotated so that the extension direction of the planned division line matches the processing feed direction of the cutting device 2 . Then, the machining feed unit and the indexing feed unit are operated to position the cutting blade 18a above the extension line of the planned division line of the workpiece.

The cutting unit 18 includes a cutting water supply nozzle 18d for supplying cutting water such as pure water to the workpiece held on the chuck table 8 and the cutting blade 18a. The workpiece is cut by rotating the cutting blade 18a around the spindle 18c and bringing the cutting edge of the cutting blade 18a into contact with the workpiece. At this time, frictional heat is generated between the workpiece and the cutting edge of the cutting blade 18a. Moreover, chips are generated from the workpiece and the cutting blade 18a. Frictional heat and cutting waste can be removed by supplying cutting water to the workpiece and the cutting blade 18a when cutting the workpiece.

When cutting the workpiece with the cutting blade 18a to divide the workpiece, the lower end 18b (see FIG. 2B) of the cutting edge of the cutting blade 18a is below the back surface (lower surface) of the workpiece. The height of the cutting unit 18 is adjusted so as to reach the height position. The cutting feed unit including the Z-axis pulse motor 36 further includes, for example, a position recognition unit (not shown) that recognizes the position of the cutting unit 18 in the cutting feed direction. The cutting device 2 positions the cutting unit 18 at a predetermined height position using a position recognition unit including a scale or the like.

Then, the cutting blade 18a is rotated and the processing feed unit is operated to move the chuck table 8 in the processing feed direction for processing feeding, and the cutting blade 18a cuts into the workpiece to cut the workpiece. . After cutting the workpiece along one planned dividing line, the indexing feed unit is operated to index feed the cutting unit 18, and then the chuck table 8 is again processed and fed along another planned dividing line. Cut the workpiece. The cutting device 2 thus cuts the workpieces one after another.

The cutting device 2 further comprises a control unit 42 . The control unit 42 has a function of controlling each component of the cutting device 2 such as the cutting unit 18, the chuck table 8, each moving mechanism, the imaging unit 38, and the cutting edge position detection unit 40 (described later). The functions of the control unit 42 are implemented, for example, as software for a device control computer.

That is, the control unit 42 is configured by a computer including a processing device such as a CPU and a storage device such as a flash memory. By operating the processing device according to software such as programs stored in the storage device, the control unit 42 functions as concrete means in which the software and the processing device (hardware resources) cooperate.

When the cutting blade 18a is repeatedly used to cut the workpiece, the cutting edge of the cutting blade 18a is gradually worn away and the diameter of the cutting blade 18a is gradually reduced. In this case, the height position of the lower end 18b of the tip of the cutting blade 18a when the cutting unit 18 is positioned at a height suitable for cutting gradually rises. Then, the workpiece cannot be sufficiently cut.

Therefore, after cutting the workpiece with the cutting blade 18a so that the lower end 18b of the cutting edge of the cutting blade 18a is positioned at a height position lower than the back surface (lower surface) of the workpiece, a setup process is periodically performed. be implemented. In the setup process, the height position of the cutting unit 18 when the lower end 18b of the cutting edge of the cutting blade 18a is positioned at a height position below the back surface (lower surface) of the workpiece is a height suitable for cutting. Detected as a position.

A cutting edge position detection unit 40 is arranged in the vicinity of the cutting unit 18 of the cutting device 2 . By using the cutting edge position detection unit 40, a setup process can be performed for positioning the lower end 18b of the cutting edge of the cutting blade 18a at a height position below the back surface (lower surface) of the workpiece when cutting the workpiece. 2A is a perspective view schematically showing the cutting edge position detection unit 40, and FIG. 2B schematically shows the cutting unit 18, the cutting edge position detection unit 40, and the control unit 42. It is a conceptual diagram showing.

A main body 44 of the cutting edge position detection unit 40 is provided with a groove-shaped blade entry portion 46 that opens upward. When using the cutting edge position detection unit 40, the cutting blade 18a is positioned above the blade entry portion 46, the cutting feed unit is operated to lower the cutting blade 18a, and the cutting blade 18a is moved to the blade entry portion 46. let in.

A light emitting portion 50 is provided on one side wall of the blade entering portion 46 , and a light receiving portion 52 is provided on the other side wall of the blade entering portion 46 at a position facing the light emitting portion 50 . That is, the light-emitting portion 50 and the light-receiving portion 52 face each other with the blade entry portion 46 interposed therebetween. The light emitting section 50 includes a light emitting window 50b and a light source 50a connected to the light emitting window 50b via an optical fiber or the like. When the light source 50a is operated, light is emitted from the light emitting window 50b. A dimmer (not shown) having a function of adjusting the amount of light emitted is connected to the light source 50a.

The light receiving section 52 includes a light receiving window 52b and a photoelectric conversion section 52a connected to the light receiving window 52b via an optical fiber or the like. The light that has reached the light receiving window 52b is received by the photoelectric conversion section 52a, and an electric signal having a voltage value corresponding to the amount of received light is output from the photoelectric conversion section 52a. The photoelectric conversion section 52 a is electrically connected to the control unit 42 and sends the electrical signal to the control unit 42 .

The light emitting window 50b and the light receiving window 52b are provided at approximately the same predetermined height position. The cutting edge position detection unit 40 is provided with an openable/closable cover 48 that protects the light emitting section 50 and the light receiving section 52 when the cutting edge position detection unit 40 is not in use. When the cutting edge position detection unit 40 is used, the cover 48 is opened in advance to expose the body 44 .

The main body 44 is further provided with a plurality of fluid ejection nozzles facing the light emitting window 50b or the light receiving window 52b. When a fluid such as air or water is ejected from the fluid ejection nozzle, dirt attached to the light emitting window 50b and the light receiving window 52b can be removed.

When the cutting edge position detection unit 40 detects the lower end 18b of the cutting edge of the cutting blade 18a, the light source 50a is operated to emit light from the light emitting window 50b, and the light is emitted to the light receiving window 52b of the light receiving portion 52. The light is received by the photoelectric conversion unit 52a connected to . The photoelectric conversion section 52 a includes a light receiving element such as a CMOS sensor or a CCD sensor, converts the light into an electric signal having a voltage value corresponding to the amount of light received, and sends the electric signal to the control unit 42 .

When the cutting blade 18a is lowered toward the blade entry portion 46, the light emitted from the light emitting window 50b is gradually blocked by the cutting blade 18a, reaches the light receiving window 52b, and is received by the photoelectric conversion portion 52a. The amount of received light gradually decreases. Therefore, the height position of the lower end 18b of the tip of the cutting blade 18a can be detected by analyzing the electrical signal output from the photoelectric conversion portion 52a by the control unit 42. FIG.

Then, the height position of the cutting unit 18 when the amount of light received by the photoelectric conversion portion 52a becomes a reference amount of light for confirming that the lower end 18b of the cutting edge has reached the predetermined height position. is detected as the reference height position. Then, based on the detected reference height position of the cutting unit 18, a height position suitable for cutting at which the cutting unit 18 should be positioned when cutting the workpiece is calculated.

The graph shown in FIG. 3A schematically shows an example of a time change in the voltage value of the electrical signal sent from the photoelectric conversion section 52a to the control unit 42 when the cutting edge of the cutting blade 18a enters the blade entry section 46. is a graph shown in FIG. In FIG. 3A, the voltage value corresponding to the amount of received light in the initial state before the amount of received light decreases is 5V. FIG. 3A schematically shows the time change 66 of the voltage value. However, the voltage value is not limited to this.

When the tip of the cutting blade 18a enters the blade entry portion 46 and the light hits the cutting blade 18a, the amount of light received decreases and the voltage value decreases. Then, the light is completely blocked by the cutting blade 18a. In the example shown in FIG. 3A, the voltage value corresponding to the amount of light received when the cutting blade 18a stops the light from reaching the light receiving window 52b is set to 0V. However, the voltage value is not limited to this.

A reference voltage value 68 is set in advance as the voltage value of the electrical signal output from the photoelectric conversion unit 52a. In the example shown in FIG. 3A, the reference voltage value 68 is set to 3V. However, the reference voltage value 68 is not limited to this.

In the setup process, the cutting unit 18 is gradually lowered, and the height position of the cutting unit 18 when the voltage value reaches the reference voltage value 68 is detected as the reference height position. Based on this reference height position, a height position suitable for cutting by the cutting unit 18 is detected.

More specifically, the height position (predetermined height position) of the lower end of the cutting blade 18a when the voltage value becomes the reference voltage value 68 is lower than the holding surface 8a of the chuck table 8 by a predetermined distance. position. Then, when the height position of the cutting unit 18 when the voltage value becomes the reference voltage value 68 is detected as the reference height position, the height position higher than the reference height position by the predetermined distance or more is used for cutting. It is registered in the control unit 42 as a height position suitable for cutting by the unit 18 . When cutting the workpiece, the cutting feed unit is operated to position the cutting unit 18 at a height suitable for cutting, and the workpiece is cut.

It should be noted that such a setup process is preferably performed while rotating the cutting blade 18a around the spindle 18c. For example, the number of rotations of the cutting blade 18a may be matched to the number of rotations of the cutting blade 18a when cutting the workpiece. This is because when the cutting blade 18a is rotated at high speed, a centrifugal force acts on the cutting blade 18a, increasing the diameter of the cutting blade 18a. The influence of the centrifugal force can be offset by matching the number of rotations of the cutting blade 18a when performing the setup process and when cutting the workpiece.

When cutting the workpiece as described above, cutting water is supplied to the cutting blade 18a and the workpiece from the cutting water supply nozzle 18d or the like in order to remove machining waste and frictional heat. On the other hand, when using the cutting edge position detection unit 40, cutting water is not supplied to the cutting blade 18a. When cutting water is supplied to the cutting blade 18a, the cutting water affects the light traveling from the light emitting window 50b of the light emitting portion 50 to the light receiving window 52b of the light receiving portion 52, and the height position of the lower end 18b of the cutting edge of the cutting blade 18a. This is because it interferes with detection.

When performing a set-up process on a cutting unit 18 having a worn cutting blade 18a after machining a workpiece, the cutting blade 18a rotating for cutting the workpiece is maintained at its rotational speed. It is efficient to enter the blade entry portion 46 while holding the blade. That is, the cutting water that has been continuously supplied to the rotating cutting blade 18a is stopped. When the cutting water supplied to the cutting blade 18a is stopped, the temperature of the cutting blade 18a gradually rises due to the frictional heat generated by the friction between the cutting blade 18a and the air.

When the temperature of the cutting blade 18a rises, thermal expansion occurs and the diameter of the cutting blade 18a increases. This tendency becomes more pronounced as the rotation speed of the cutting blade 18a increases. Therefore, even if the height of the cutting unit 18 in the cutting feed direction is maintained after the cutting edge of the cutting blade 18a enters the blade entry portion 46, the height position of the lower end 18b of the cutting edge changes with time. end up

FIG. 3B is a graph showing how the diameter of the cutting blade 18a changes over time due to thermal expansion. The graph shown in FIG. 3B shows the time from the start of observation when the amount of light received by the light receiving unit 52 is observed in the form of the voltage value of the electric signal output by the photoelectric conversion unit 52a, It is a graph which shows typically the relationship between the variation|change_quantity of the voltage value corresponded to the variation|change_quantity of the light reception amount, and.

FIG. 3B shows a relationship 70 between the amount of change in voltage value and time when the number of rotations of the cutting blade 18a is relatively high, and the amount of change in voltage value and time when the number of rotations of the cutting blade 18a is relatively low. Relationships 72 and are shown schematically. When the supply of cutting water to the cutting blade 18a is stopped, the temperature of the rotating cutting blade 18a gradually increases, and accordingly the amount of thermal expansion of the cutting blade 18a also gradually increases.

Furthermore, the temperature rise of the cutting blade 18a due to frictional heat varies depending on the rotation speed of the cutting blade 18a, and the temperature of the cutting blade 18a tends to rise more easily as the rotation speed of the cutting blade 18a increases. Moreover, the diameter of the cutting blade 18a changes depending on the time required to complete the setup process.

For example, when a 2-inch diameter cutting blade that had been rotated at a rotational speed of 30 krpm was rotated at a rotational speed of 80 krpm, a thermal expansion of the cutting blade 18a of about 6 to 7 μm was confirmed.

Also, the cutting blade was rotated at a rotational speed of 80 krpm while supplying cutting water, and then the tendency of temperature rise was observed when the supply of cutting water was stopped. As a result of observation, the temperature of the cutting blade, which was about 27°C before stopping the cutting water, reached about 31°C in 10 seconds after stopping, about 34°C in 20 seconds, and about 35°C in 30 seconds. Ta. After that, when the supply of cutting water was restarted, the temperature dropped to about 27°C within 10 seconds.

Since cutting water adhering to the cutting unit 18 may drop into the blade entry portion 46, the height of the cutting unit 18 is repeatedly detected in the setup process in order to perform the setup process with high accuracy. Therefore, the execution time of the setup process also varies. In the setup process, the temperature of the cutting blade 18a rises moment by moment, and the diameter of the cutting blade 18a changes. It's not easy.

If the cutting blade 18a is thermally expanded during the setup process, the reference height position of the cutting unit 18 detected by the setup process does not match the height position that should be detected. Therefore, when the height position suitable for cutting of the cutting unit 18 is calculated based on the detected reference height position, and the cutting unit 18 is positioned at the height position suitable for cutting to cut the workpiece, The depth of cut of the cutting blade 18a becomes shallow, and the workpiece cannot be cut appropriately.

Therefore, in the cutting unit position detection method and the cutting apparatus according to the present embodiment, the thermal expansion tendency of the cutting blade 18a is measured in advance, and the reference height position of the cutting unit 18 detected in the setup process is corrected. The description of the cutting apparatus 2 capable of implementing the method for detecting the position of the cutting unit according to the present embodiment will be continued below.

As shown in FIG. 2B, the control unit 42 of the cutting device 2 includes, for example, a voltage value comparison section 54, a reference voltage value registration section 56, a cutting unit height detection section 58, and a correction section 60. A registration section 62 and a cutting unit height registration section 64 are provided. The functions of each section of the control unit 42 are implemented by software stored in a storage device on a computer having a processing device such as a CPU and a storage device, for example. Each part of the control unit 42 will be described below.

The voltage value comparison unit 54 is connected to the photoelectric conversion unit 52a of the light receiving unit 52, and receives an electric signal having a voltage value corresponding to the amount of light received by the photoelectric conversion unit 52a from the photoelectric conversion unit 52a. . The voltage value comparison section 54 records how the light is gradually blocked by the cutting blade 18a entering the blade entry section 46 in the setup process, the amount of received light decreases, and the voltage value decreases.

The voltage value comparison unit 54 detects the cutting blade 18a when the voltage value of the electric signal output from the photoelectric conversion unit 52a of the light receiving unit 52 matches the reference voltage value registered in the reference voltage value registration unit 56 described below. is positioned at a predetermined height position. When the voltage value of the electrical signal matches the reference voltage value, the voltage value comparing section 54 outputs information indicating that the lower end 18b of the cutting edge of the cutting blade 18a is positioned at a predetermined height position to a cutting unit described later. It is sent to the height detection section 58 .

The reference voltage value registration unit 56 stores a photoelectric conversion voltage when light emitted from the light emitting unit 50 is received by the light receiving unit 52 when the lower end 18b of the cutting edge of the cutting blade 18a is positioned at a predetermined height. The voltage value of the electrical signal output from the section 52a is registered in advance as the reference voltage value. Here, the predetermined height position of the lower end 18b of the cutting edge of the cutting blade 18a means a height position lower than the holding surface 8a of the chuck table 8 by a predetermined distance.

The cutting unit height detection section 58 is connected to the cutting feed unit including the Z-axis pulse motor 36 and the like and the voltage value comparison section 54 . The cutting unit height detector 58 can acquire the height position of the cutting unit 18 in the cutting feed direction from the cutting feed unit. Then, the height position of the cutting unit 18 when the voltage value comparator 54 detects that the lower end 18b of the cutting edge of the cutting blade 18a is positioned at the predetermined height position is detected as the reference height position. Then, a height position suitable for cutting by the cutting unit 18 is calculated based on the reference height position. The reference height position is corrected by the correction section 60 described below.

The correction section 60 corrects the reference height position of the cutting unit 18 detected by the cutting unit height detection section 58 . The correction unit 60 refers to the time when the voltage value comparison unit 54 detects that the lower end 18b of the cutting edge of the cutting blade 18a is positioned at the predetermined height position, and determines the reference height position of the cutting unit 18. to correct. The reason why the corrector 60 refers to this time is that this time determines the amount of thermal expansion of the cutting blade 18a. The temporal change in the amount of thermal expansion of the cutting blade 18a is registered in the relationship registration section 62 described below.

The relationship registering unit 62 calculates the temporal change in the amount of light received by the photoelectric conversion unit 52a of the light receiving unit 52 emitted from the light source 50a of the light emitting unit 50, and the voltage value of the electric signal output by the photoelectric conversion unit 52a. It can be registered as a change. The relationship registration unit 62 registers, for example, the relationship between the voltage value of the electrical signal that changes due to thermal expansion of the rotating cutting blade 18a and time.

For example, when the cutting blade 18 a is attached to the cutting device 2 , the cutting edge position detection unit 40 observes how the cutting blade 18 a thermally expands due to frictional heat generated by rotation. to register. An example of the observation procedure will be explained.

In order to match the situation of the setup process that is performed after cutting the workpiece, for example, cutting water is sprayed onto the cutting blade 18a while rotating the cutting blade 18a at the same number of rotations as when cutting the workpiece. . Next, the injection of cutting water to the cutting blade 18a is stopped. When the injection of cutting water is stopped, thermal expansion of the cutting blade 18a begins.

Then, the cutting edge of the rotating cutting blade 18 a is caused to enter the blade entrance portion 46 of the cutting edge position detection unit 40 . Then, the cutting unit 18 is positioned at a height suitable for observing how the cutting blade 18a thermally expands.

In the cutting edge position detection unit 40, light is emitted from the light emitting section 50 to the light receiving section 52, and changes in the amount of light received by the light receiving section 52 are observed. Then, in the control unit 42, the relationship between the voltage value of the electrical signal output by the photoelectric conversion section 52a that changes with time due to the thermal expansion of the rotating cutting blade 18a and the time is obtained. Registered in the registration unit 62 .

Strictly speaking, the thermal expansion of the cutting blade 18a starts when the supply of cutting water to the cutting blade 18a is stopped. However, even when the setup process of the cutting blade 18a is performed after cutting the workpiece, the thermal expansion of the cutting blade 18a is the same from when the supply of cutting water is stopped to when the cutting edge position detection unit 40 starts observation. progress to some extent.

Therefore, if the state of thermal expansion of the cutting blade 18a from when the cutting blade 18a starts to thermally expand to when the cutting edge position detection unit 40 starts observation is obtained by another procedure, the correcting unit 60 can detect the thermal expansion of the cutting unit 18. The reference height position can be corrected with higher accuracy. For example, the cutting edge of the cutting blade 18a that is not rotating is caused to enter the blade entry portion 46 of the cutting edge position detection unit 40, and then the cutting blade 18a starts rotating. The initial trend of thermal expansion of the cutting blade 18a can then be observed.

Further, the relation registration unit 62 may register a plurality of relations between the voltage value of the electric signal and time. The state of thermal expansion of the cutting blade 18a changes depending on the rotation speed of the cutting blade 18a. Therefore, the tendency of thermal expansion is measured by the cutting edge position detection unit 40 while rotating the cutting blade 18a at a plurality of rotation speeds that can be set when cutting the workpiece. Then, when correcting the reference height position of the cutting unit 18, the correcting section 60 selects an appropriate relationship from a plurality of relationships registered in the relationship registering section 62 and performs the correction.

FIG. 3B shows an example of the relationship registered in the relationship registration unit 62. As shown in FIG. The relationship registration unit 62 stores, for example, the relationship between the amount of change in the amount of received light that changes over time due to thermal expansion of the rotating cutting blade 18a and the time from the start of observation as an electric signal output by the photoelectric conversion unit 52a. is registered as a graph of the voltage value of

The correction unit 60 refers to the time when the voltage value comparison unit 54 detects that the lower end 18b of the cutting edge of the cutting blade 18a is positioned at the predetermined height position, and refers to the time registered in the relationship registration unit 62. A correction amount for the reference height position of the cutting unit 18 is determined from the relationship. The correction amount corresponds to the amount of thermal expansion of the cutting blade 18a at that time. Then, the reference height position of the cutting unit 18 corrected by the correction amount is registered in the cutting unit height registration section 64 .

When cutting the workpiece, the cutting feed unit is controlled to position the cutting unit 18 at a height position suitable for cutting calculated from the corrected reference height position, and the cutting blade 18a cuts the workpiece. Can cut properly. As described above, in the cutting device 2, the thermal expansion of the cutting blade 18a is taken into account, and the setup process is performed with the influence of the thermal expansion eliminated. Therefore, the reference height position of the cutting unit 18 to be determined in the setup process can be determined appropriately.

Next, a method for detecting the height position of the cutting unit according to this embodiment will be described. The height position detection method of the cutting unit is implemented in the cutting device 2, for example. A case where the height position detection method of the cutting unit is carried out in the cutting device 2 will be described below. FIG. 4 is a flow chart showing the flow of each step of the method for detecting the height position of the cutting unit.

In the cutting unit height position detection method, the cutting blade mounting step S10 may be performed first. In the cutting blade mounting step S10, the cutting blade 18a is mounted on the tip of the spindle 18c of the cutting unit 18 provided in the cutting device 2. As shown in FIG.

Cutting a workpiece with the cutting blade 18a causes wear of the cutting edge, so a setup process is required. In order to perform a setup process that takes into consideration the thermal expansion of the cutting blade 18a, it is preferable to observe the thermal expansion tendency of the cutting blade 18a immediately after the cutting blade mounting step S10 is performed.

Next, a cutting blade positioning step S20 is performed. In the cutting blade positioning step S20, the cutting blade 18a is caused to enter the blade entry portion 46 of the cutting edge position detection unit 40 by the cutting feed unit, and the light emitted by the light emitting portion 50 and received by the light receiving portion 52 is blocked by a predetermined amount. position the cutting blade 18a on the .

At this time, the height at which the cutting blade 18a is positioned is suitable for observing the state of thermal expansion of the cutting blade 18a. For example, it may be the height of the cutting blade 18a positioned when the reference height position of the cutting unit 18 is detected in the setup process. That is, the height of the cutting blade 18a may be set when the lower end 18b of the cutting edge of the cutting blade 18a is positioned at a predetermined height position.

After the cutting blade positioning step S20, a relation registration step S30 is performed. In the relationship registration step S30, the cutting edge position detection unit 40 is operated while the height of the cutting unit 18 in the cutting feed direction is maintained, and the light receiving unit 52, which changes with time due to thermal expansion of the rotating cutting blade 18a, receives light. Observe the amount of light received. Then, the relationship between the time from the start of observation and the amount of change in the voltage value corresponding to the amount of change in the amount of received light is registered in the relationship registration section 62 of the control unit 42 .

In the cutting blade positioning step S20, the cutting blade 18a is rotating. At this time, the rotation speed of the cutting blade 18a is adjusted to the rotation speed of the cutting blade 18a during cutting of the workpiece. Note that the rotation of the cutting blade 18a may be started, for example, before the cutting edge of the cutting blade 18a enters the blade entry portion 46 of the cutting edge position detection unit 40, and after the cutting edge enters the blade entry portion 46. may be started.

For example, the cutting blade 18a may be rotated in advance to create a situation similar to the setting-up process of the cutting blade 18a after cutting the workpiece. In this case, in the cutting blade positioning step S20, first, a cutting blade rotation start step and a cutting water supply step of supplying cutting water to the cutting blade 18a are performed. After that, a cutting water stop step is performed to stop the supply of cutting water to the cutting blade 18 a , and then the cutting edge of the cutting blade 18 a enters the blade entry portion 46 .

Alternatively, in the cutting blade positioning step S<b>20 , the cutting blade 18 a may start rotating after the cutting edge of the cutting blade 18 a enters the blade entry portion 46 of the cutting edge position detection unit 40 . In this case, when the cutting blade 18a starts to rotate, the temperature of the cutting blade 18a gradually rises, and the thermal expansion of the cutting blade 18a can be observed by the cutting edge position detection unit 40 from the initial stage of thermal expansion.

When the relationship registration step S30 is performed, the setup process can be performed in consideration of the thermal expansion of the cutting blade 18a. Then, after the relationship registration step S30, a cutting step of cutting the workpiece with the cutting blade 18a may be performed. In the cutting step, the workpiece is held by the holding surface 8a of the chuck table 8, the cutting blade 18a is rotated, the cutting unit is positioned at a height suitable for cutting, and the chuck table 8 is processed and fed to feed the cutting blade 18a. cut into the workpiece.

In order to position the cutting unit 18 at a height suitable for cutting in the cutting step, after the cutting blade 18a is mounted on the spindle 18c and before the workpiece is processed, the cutting edge position detection unit 40 is used for setup. steps may be performed. When the cutting unit 18 is positioned at a height suitable for cutting, the workpiece can be cut appropriately. When the workpiece is repeatedly cut, the tip of the cutting blade 18a is worn and the diameter of the cutting blade 18a is reduced.

Next, the height position detection step S40 performed as part of the setup process will be described. In the height position detection step S40, the cutting blade 18a that has machined the workpiece is rotated around the spindle 18c to enter the blade entry portion 46 of the cutting edge position detection unit 40. FIG. Light emitted from the light-emitting window 50b of the light-emitting portion 50 passes through the light-receiving window 52b of the light-receiving portion 52 and is received by the photoelectric conversion portion 52a. Then, the cutting blade 18a is positioned at a height where the light is blocked by a predetermined amount.

That is, when the voltage value of the electrical signal output by the photoelectric conversion unit 52a matches the reference voltage value registered in the reference voltage value registration unit 56, the height of the lower end 18b of the cutting edge of the cutting blade 18a reaches the predetermined height. The voltage value comparison unit 54 detects that the position is reached. At this time, the cutting unit height detector 58 detects the height position of the cutting unit 18 from the cutting feed unit as the reference height position, and the height position suitable for cutting of the cutting unit 18 is calculated from the reference height position. be done.

Here, in the height position detection step S40, in order to detect the reference height position of the cutting unit 18 with high accuracy, the cutting blade 18a may be moved up and down repeatedly in the blade entry portion 46. FIG.

The cutting water supplied to the cutting blades 18a and the like when cutting the workpiece may adhere to the cutting unit 18 and drop into the blade entry portion 46 while the height position detection step S40 is being performed. . In addition, cutting water clings to the cutting edge of the cutting blade 18a rotating at high speed, and may remain on the cutting edge even when the supply of cutting water is stopped. In these cases, there is a risk that the cutting water will hinder the passage of light from the light-emitting portion 50 to the light-receiving portion 52 .

Therefore, when the cutting blade 18a is repeatedly moved up and down to the blade entry portion 46, the air flow around the cutting blade 18a changes and the cutting water clinging to the cutting blade 18a is removed. Further, by repeatedly raising and lowering the cutting blade 18a while operating the cutting edge position detection unit 40 and repeating the detection by the voltage value comparison unit 54 to increase the number of measurements, the reference height position of the cutting unit 18 can be made highly accurate.

Further, in the height position detection step S40, the indexed reference height position of the cutting unit 18 is corrected by the relationship registered in the relationship registration section 62 in the relationship registration step S30. That is, the correction section 60 corrects the reference height position of the cutting unit 18 calculated by the cutting unit height detection section 58 using the relationship registered in the correction section 60 .

In the height position detection step S40, the time required to detect that the lower end 18b of the cutting edge of the cutting blade 18a is positioned at a predetermined height varies. The longer the time required for detection, the greater the thermal expansion of the cutting blade 18a. Therefore, when correcting the reference height position of the cutting unit 18, the time when it is detected that the lower end 18b of the cutting edge of the cutting blade 18a is positioned at the predetermined height position is referred to.

That is, from the relationship registered in the relationship registration unit 62, the amount of change in the amount of light received due to the thermal expansion of the cutting blade 18a at that time is calculated in the form of the amount of change in the voltage value of the electrical signal output by the photoelectric conversion unit 52a. do. Then, the amount of thermal expansion of the cutting blade 18a is calculated from the amount of change in the voltage value.

Then, the reference height position of the cutting unit 18 detected by the cutting unit height detector 58 is corrected by the amount of thermal expansion of the cutting blade 18a. More specifically, the reference height position of the cutting unit 18 before correction is higher than the reference height position to be detected by the thermal expansion amount. Therefore, the thermal expansion amount is subtracted from the reference height position of the cutting unit 18 before correction. Then, the corrected reference height position is registered in the cutting unit height registration section 64 .

When cutting the workpiece again with the cutting blade 18a, the control unit 42 positions the height of the cutting unit 18 at a height position suitable for cutting calculated based on the corrected reference height position. . Since cutting water is supplied to the cutting blade 18a and the workpiece when cutting the workpiece, the thermal expansion of the cutting blade 18a is suppressed. Then, the lower end 18b of the cutting edge of the cutting blade 18a becomes a height below the lower surface of the workpiece, and the workpiece is appropriately cut.

In the relationship registration step S30, the cutting blade 18a may be rotated at a rotation speed corresponding to the rotation speed of the cutting blade 18a in the height position detection step S40. That is, the relationship registration step S30 and the height position detection step S40 may be performed by rotating the cutting blade 18a at the number of rotations of the cutting blade 18a when cutting the workpiece with the cutting blade 18a. If the number of revolutions of the cutting blades 18a is made uniform, the influence of the centrifugal force applied to the cutting blades 18a can be eliminated.

As described above, according to the cutting unit height detection method and the cutting device 2 according to the present embodiment, the setup process is appropriately performed, and the cutting unit 18 is positioned at a height suitable for cutting the workpiece. be done.

In the above-described embodiment, the relationship registration unit 62 registers the time change due to thermal expansion of the diameter of the cutting blade 18a in the form of the voltage value of the electrical signal output from the photoelectric conversion unit 52a. may be registered in the relationship registration unit 62 in another form. Further, the correction unit 60 refers to the time change due to thermal expansion of the diameter of the cutting blade 18a registered in the form of the voltage value of the electric signal registered in the relationship registration unit 62, and determines the reference height position of the cutting unit 18. Although corrected, the correction of the reference height position may be implemented in other ways.

For example, the relationship registration unit 62 may register the amount of thermal expansion of the cutting blade 18a that changes with time. In this case, the correction unit 60 corrects the detected reference height position of the cutting unit 18 by subtracting the amount of thermal expansion from the reference height position.

In addition, the relationship related to the time change in the diameter due to thermal expansion of the cutting blade 18a registered in the relationship registration unit 62 was acquired using the cutting blade 18a attached to the cutting unit 18 when the setup process was performed. It doesn't have to be something. For example, when the cutting blades 18a of the same type are exchanged one after another for each life of the cutting device 2 to repeatedly cut the workpiece, the relationship registered in the relationship registration unit 62 is the cutting blade 18a that was first attached. It may be obtained by using.

In such a case, the relationship registered in the relationship registration unit 62 may be used to correct the reference height position of the cutting unit 18 to which another cutting blade 18a of the same type is mounted. That is, even when correcting the reference height position of the cutting unit 18 to which a cutting blade 18a other than the cutting blade 18a used to acquire the relationship registered in the relationship registration unit 62 is mounted, the setup process can be appropriately performed. When implemented, the effects of one aspect of the present invention are obtained.

In addition, the structures, methods, and the like according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention.

2 cutting device 4 device base 6 X-axis movement table 8 chuck table 8a holding surface 10 clamp 12, 24, 30 guide rail 14, 28, 34 ball screw 16, 28a, 36 pulse motor 18 cutting unit 18a cutting blade 18b cutting edge Lower end 18c Spindle 18d Cutting water supply nozzle 20 Drainage channel 22 Support structure 26, 32 Moving plate 38 Imaging unit (camera)
40 cutting edge position detection unit 42 control unit 44 main body 46 blade entry portion 48 cover 50 light emitting portion 50a light source 50b light emitting window 52 light receiving portion 52a photoelectric conversion portion 52b light receiving window 54 voltage value comparison portion 56 reference voltage value registration portion 58 cutting unit height Detection unit 60 Correction unit 62 Relationship registration unit 64 Cutting unit height registration unit 66 Time change of voltage value 68 Reference voltage value 70, 72 Relationship

Claims (3)

a chuck table for holding a workpiece on a holding surface;
It has a spindle extending in a direction parallel to the holding surface and a cutting blade attached to the tip of the spindle, and supplies cutting water to the workpiece and the cutting blade held on the chuck table. a cutting unit for cutting the workpiece with the cutting blade rotating around the spindle while
a cutting feed unit that feeds the cutting unit in a cutting feed direction orthogonal to the holding surface;
a cutting edge position detection unit that detects the height position of the lower end of the cutting edge of the cutting blade;
A control unit that controls each component,
The cutting edge position detection unit includes a blade entry portion into which the cutting blade enters, and a light emitting portion and a light receiving portion facing each other across the blade entry portion,
A position detection method for a cutting unit using a cutting device in which the control unit includes a relationship registration unit capable of registering temporal changes in the amount of light received by the light-receiving unit emitted from the light-emitting unit,
The cutting blade is caused to enter the blade entry portion of the cutting edge position detection unit by the cutting feed unit, and the cutting blade is positioned at a height at which a predetermined amount of light emitted by the light emitting portion and received by the light receiving portion is blocked. a cutting blade positioning step;
After the cutting blade positioning step, while maintaining the height of the cutting unit in the cutting feed direction, the amount of received light that changes with time due to thermal expansion of the rotating cutting blade is observed, and the time from the start of observation is and the amount of change in the amount of received light, and a relationship registration step of registering the relationship between
After the relationship registration step, the cutting blade after machining the workpiece is rotated around the spindle and enters the blade entry portion of the blade edge position detection unit, The cutting blade is positioned at a height where the light received by the part is blocked by the predetermined amount, and the height position of the cutting unit when the height of the lower end of the cutting edge of the cutting blade is at the predetermined height position and a height position detection step for indexing as a reference height position,
In the height position detection step, referring to the time when it is detected that the lower end of the cutting edge of the cutting blade is positioned at the predetermined height position, the cutting position is determined from the relationship registered in the relationship registration unit. A position detection method for a cutting unit, comprising: determining a correction amount for the reference height position of the unit; and correcting the calculated reference height position of the cutting unit with the correction amount . 2. The cutting unit position detecting method according to claim 1, wherein in said relationship registration step, said cutting blade is rotated at a number of rotations corresponding to the number of rotations of said cutting blade in said height position detecting step. a chuck table for holding a workpiece on a holding surface;
It has a spindle extending in a direction parallel to the holding surface and a cutting blade attached to the tip of the spindle, and supplies cutting water to the workpiece and the cutting blade held on the chuck table. a cutting unit for cutting the workpiece with the cutting blade rotating around the spindle while
a cutting feed unit that feeds the cutting unit in a cutting feed direction orthogonal to the holding surface;
a cutting edge position detection unit that detects, as a reference height position, the height position of the cutting unit when the lower end of the cutting edge of the cutting blade reaches a predetermined height position;
A control unit that controls each component,
The cutting edge position detection unit is
a blade entry portion into which the cutting blade enters;
a light-emitting portion and a light-receiving portion facing each other across the blade entry portion;
a photoelectric conversion unit that outputs an electric signal having a voltage value corresponding to the amount of light received by the light receiving unit;
The control unit is
a relationship registration unit capable of registering changes over time in the amount of light received by the light-receiving unit emitted from the light-emitting unit as changes over time in the voltage value of the electrical signal output from the photoelectric conversion unit;
of the electric signal output from the photoelectric conversion portion when the light emitted from the light emitting portion is received by the light receiving portion when the lower end of the cutting edge of the cutting blade is positioned at the predetermined height position a reference voltage value registration unit in which a voltage value is registered as a reference voltage value;
When the voltage value of the electrical signal output from the photoelectric conversion unit matches the reference voltage value registered in the reference voltage value registration unit, the lower end of the cutting edge of the cutting blade is positioned at the predetermined height position. a voltage value comparator for detecting that
Connected to the voltage value comparing portion, the height of the cutting unit when the voltage value comparing portion detects that the lower end of the cutting edge of the cutting blade is positioned at the predetermined height position is the reference height a cutting unit height detector that detects as a position;
a correction unit that corrects the reference height position of the cutting unit detected by the cutting unit height detection unit;
In the relationship registration unit, the relationship between the voltage value of the electrical signal output by the photoelectric conversion unit that changes with time due to thermal expansion of the rotating cutting blade and time is registered,
The correcting unit refers to the time when the voltage value comparing unit detects that the lower end of the cutting edge of the cutting blade is positioned at the predetermined height position, and refers to the time registered in the relationship registering unit. A cutting apparatus, wherein a correction amount for the reference height position of the cutting unit is determined from the relationship.