Cutting Machining Apparatus

A cutting machining apparatus 1 includes: a head 5 including a spindle drive 51 that rotary drives a rotary spindle with a tool 20 secured to a tip of the rotary spindle; a proximity sensor 34; a signal acquirer obtaining a signal waveform of a detection signal that is output from the proximity sensor 34 when the rotary spindle 52 is rotated in a state in which the head 5 is moved so that the proximity sensor 34 faces a lateral side of the tool before and after cutting machining of the workpiece W using the tool; and a determiner determining whether or not the tool 20 is broken based on whether or not there is a difference in signal waveforms obtained before and after the cutting machining.

FIELD OF THE INVENTION

The present disclosure relates to a cutting machining apparatus.

BACKGROUND OF THE INVENTION

A gun drill formed by joining a cutting edge, a steel pipe, and a handle to each other by a silver soldering joint has been proposed, wherein one end of an enamel wire is connected to a copper plate that is provided at an end of the handle and the other end is connected, with a conductive adhesive, near a proximal end of the cutting edge, the enamel wire is buried in an electrically isolated state on the surface of the cutting edge, the steel pipe, and the handle (for example, refer to Japanese Patent Application Publication No. H09-225719). When the gun drill is broken at the silver soldering joint during use, the enamel wire is cut at the same time, and the conductivity of the enamel wire is blocked. Thus, the breakage of the gun drill can be detected by monitoring the conductivity state of the enamel wire.

However, in the case of the gun drill described in Japanese Patent Application Publication No. H09-225719, for example, when the tip of the cutting edge where the enamel wire is not embedded is broken, the breakage of the cutting edge cannot be detected. In such a case, the workpiece continues to be processed despite the tip of the cutting edge being damaged, and the machining accuracy of the workpiece may be greatly reduced.

The present disclosure was made in consideration of the above problem. Thus, an objective of the present disclosure is to provide a cutting machining apparatus that can improve machining accuracy of a workpiece by quickly detecting a breakage of a tool.

SUMMARY OF THE INVENTION

In order to achieve the above objective, the cutting machining apparatus according to the present disclosure includes:a head including a spindle drive that rotary drives a rotary spindle with a tool secured to a tip of the rotary spindle;a first proximity sensor;a signal acquirer obtaining detection signal information indicating an intensity of a detection signal that is output from the first proximity sensor when the rotary spindle is rotated in a state in which the head is moved so that the first proximity sensor faces a lateral side of the tool before and after cutting machining of a workpiece using the tool; anda determiner that determines whether or not the tool is broken based on whether or not there is a difference in signal waveforms corresponding to time transitions in intensities of detection signals indicated by detection signal information obtained before and after the cutting machining.

According to the present disclosure, the signal acquirer obtains detection signal information indicating an intensity of a detection signal that is output from the proximity sensor when the rotary spindle is rotated in a state in which the head is moved so that the proximity sensor is disposed on the lateral side of the tool before and after cutting machining of a workpiece. The determiner then determines whether or not the tool is broken based on whether or not there is a difference in signal waveforms corresponding to time transitions in intensities of detection signals indicated by detection signal information obtained before and after the cutting machining. As a result, a breakage of the tip of the tool during cutting machining can be detected quickly, and thus the machining accuracy of the workpiece can be improved.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a cutting machining apparatus according to an embodiment of the present disclosure is described with reference to the drawings. The cutting machining apparatus according to the present embodiment includes: a head including a spindle drive that rotary drives a rotary spindle with a tool secured to the tip of the rotary spindle; a proximity sensor; a signal acquirer obtaining detection signal information indicating an intensity of a detection signal that is output from the proximity sensor when the rotary spindle is rotated in a state in which the head is moved so that the proximity sensor faces a lateral side of the tool before and after cutting machining of a workpiece using the tool; and a determiner determining whether or not the tool is broken based on whether or not there is a difference in signal waveforms corresponding to time transitions of intensities of detection signals indicated by detection signal information obtained before and after cutting machining. The cutting machining apparatus according to the present embodiment is particularly used in a medical field where high precision machining of a workpiece is required while maintaining a clean environment of a machining area where machining of the workpiece is conducted. The cutting machining apparatus is used, for example, to create a so-called bone thread for joining a fractured bone of a patient from a bone fragment collected from the patient, or to create a filling member having a shape adapted to the shape of a defective portion to fill the defective portion of the patient's bone. Note that the cutting machining apparatus according to the present embodiment is not limited to those machining the aforementioned bone fragments, and may be applied for processing other living tissues or materials that are different from living tissues.

As illustrated inFIG.1, a cutting machining apparatus1according to the present embodiment includes: a holding unit3that holds a workpiece W; a head5that is positioned facing the holding unit3and holds a tool20; a controller (not illustrated) that controls the operation of the holding unit3and the head5; and a display panel11. In addition, the cutting machining apparatus1includes a chassis10of a rectangular box shape that has an opening10bin the +Y direction-side side wall formed for inserting and removing a workpiece W and housing the holding unit3, the head5, and the controller inside. Although not illustrated inFIG.1, the opening10bcan be occluded by a door15described later. Furthermore, as illustrated inFIG.2, the cutting machining apparatus1includes: an interior case13of a rectangular box shape one side of which is open and in which portions of the holding unit3and the head5are disposed; a first cover141and a second cover142formed of a soft material; and a door15covering the opening10bfrom the +Y direction side. The cutting machining apparatus1also includes a lift drive44that raises and lowers the head5in a vertical direction, an X-direction drive71that drives the head5along the X-axis direction, and a Y-direction drive76that drives the head5along the Y-axis direction. The chassis10has the interior case13disposed inside and the display panel11mounted on the +Z direction side of the opening10bin the +Y direction-side side wall. The display panel11displays, for example, a progress status of cutting machining processing performed on a workpiece W.

The interior case13has a machining area S1formed inside where machining of a workpiece W is conducted. The machining area S1is enclosed by the interior case13and the door15. The interior case13is disposed inside the chassis10in a posture in which the open portion of the interior case13is oriented toward the opening10bside of the chassis10and has openings13aand13bprovided in the +Z direction-side peripheral wall and the −Y direction-side peripheral wall, respectively. Here, the opening13ais a first opening through which the head5is inserted, and the opening13bis a second opening through which the holding unit3is inserted. In addition, a support member12that supports the head5, the holding unit3, and the like is disposed in an area S2outside the interior case13within the chassis10.

The head5includes: a long rotary spindle52provided, at one end of the longitudinal direction, with a chuck53that holds the tool20; a spindle drive51that rotates the rotary spindle52about a central axis along the longitudinal direction thereof; a head cover54; and a proximity sensor55. The chuck53includes a chuck (not illustrated) and an actuator (not illustrated) that drives the chuck, and the chuck opens and closes according to a control signal that is input from the controller. The head5is secured to a slider422that is slidably held on a rail421extending along the Z axis direction on the +Y direction side of a base41. The lift drive44includes: a long feed screw (not illustrated) arranged along the Z-axis direction and screwed to a nut (not illustrated) provided on a portion of the slider422; and a motor (not illustrated) coupled to the feed screw to rotate the feed screw. The lift drive44then raises and lowers the slider422and the head5secured to the slider422along the Z-axis direction by rotating the feed screw arranged along the Z-axis direction.

The base41is also secured via a bracket43to a slider722that is slidably held on a rail721extending along the X-axis direction. The X-direction drive71includes: a long feed screw (not illustrated) arranged along the X-axis direction and screwed to a nut (not illustrated) provided on a portion of the bracket43; and a motor (not illustrated) coupled to the feed screw to rotate the feed screw. The X-direction drive71then moves the slider722and the base41secured to the slider722along the X-axis direction by rotating the feed screw arranged along the X-axis direction. As a result, the X-direction drive71moves the base41and the head5together along the X-axis direction via the feed screw. The rail721is supported by sliders772that are slidably held on two rails771of which longitudinal ends extend along the Y-axis direction. The Y-direction drive76includes: a long feed screw (not illustrated) arranged along the Y-axis direction and screwed to a nut (not illustrated) provided on a portion of the base41; and a motor (not illustrated) coupled to the feed screw to rotate the feed screw. The Y-direction drive76then moves the sliders772and the rail721supported by the sliders772along the Y-axis direction by rotating the feed screw arranged along the Y-axis direction. As a result, the Y-direction drive76moves the rail721, the slider722, the base41, and the head5together via the feed screw along the Y-axis direction.

As illustrated inFIG.3A, the head cover54has a bottomed square tube shape with a bottom wall provided with an opening54athrough which the tool20is inserted and has the tip of the spindle drive51and the rotary spindle52disposed inside. The proximity sensor55is, for example, an inductive proximity sensor that is a second proximity sensor including a sensor part551and a signal output part552, as illustrated inFIG.3B. The sensor part551has an induction coil (not illustrated) and a flat rectangular plate-shaped package in which the induction coil is buried. The signal output part552has a flat rectangular plate-shaped package that internally includes: an oscillation circuit (not illustrated) connected to the induction coil; an amplitude detection circuit (not illustrated) that detects the amplitude of an output current of the oscillation circuit and outputs a detection voltage reflecting the intensity of the detected amplitude; and an output circuit (not illustrated) that generates a detection signal based on the detection voltage output from the amplitude detection circuit and transmits the detection signal to the controller. The sensor part551and the signal output part552are disposed in an area between the head cover54and the spindle drive51inside the head cover54.

As illustrated inFIG.4, the holding unit3includes: a workpiece holder32that holds a workpiece W; a tool holder33that has a substantially bottomed circular shape and holds the tool20in a state in which the tool20is inserted inside; a box-shaped unit body31; and a proximity sensor34. Also, as illustrated inFIG.2, the holding unit3includes: a rotary drive81that causes the entire unit body31to rotate about a rotational axis (hereinafter, referred to as “B axis”) JB extending along the longitudinal direction of the unit body31; and a rotary drive86that causes the workpiece holder32to rotate about a rotational axis (hereinafter, referred to as the “C axis”) JC extending along a direction orthogonal to the longitudinal direction of the unit body31.

The rotary drive86includes a motor that is disposed inside the unit body31and rotates a shaft (not illustrated) that extends along the C axis JC and of which tip is coupled to the workpiece holder32. The rotary drive81includes a motor that supports the −Y direction-side end of a shaft82that has a tubular shape and extends along the B axis to rotate the shaft82about the B axis JB. The unit body31is secured to the +Y direction-side end of the shaft82. The rotary drive81is supported by the support member12provided on the outside of the interior case13within the housing10.

The unit body31has a hollow rectangular first section311and a rectangular box-shaped second section312that is continuous to the first section311at the +Y direction-side end of the first section311. The first section311is secured to the shaft82at the −Y direction side end of the first section311, as illustrated inFIG.2. Then, when the shaft82of the rotary drive81rotates about the B axis JB, the unit body31rotates about the B axis JB accordingly. The workpiece holder32is a chuck that grips the proximal end of a long workpiece W. The workpiece holder32is secured to the peripheral wall of the second section312of the unit body31. The tool holder33is secured to the unit body31in such a way that, in a state in which the tool20is not inserted in the tool holder33, the inside of the tool holder33is in communication with the outside of the unit body31and the outer wall of the tool holder33is isolated from the outside of the unit body31.

The proximity sensor34is, for example, an inductive proximity sensor that is a first proximity sensor including a sensor part341and a signal output part342. The sensor part341has an induction coil (not illustrated) and a flat rectangular plate-shaped package in which the induction coil is buried. The signal output part342has a flat rectangular plate-shaped package that internally includes: an oscillation circuit (not illustrated) connected to the induction coil; an amplitude detection circuit (not illustrated) that detects the amplitude of an output current of the oscillation circuit and outputs a detection voltage reflecting the intensity of the detected amplitude; and an output circuit (not illustrated) that generates a detection signal based on the detection voltage output from the amplitude detection circuit and transmits the detection signal to the controller. The sensor part341is disposed inside the side wall of the first section311of the unit body31, facing the workpiece holder32in the Y-axis direction, and the signal output part342is disposed adjacent to the workpiece holder32inside the second section312of the unit body31.

The first cover141is formed of a soft material such as a thin rubber film, a vinyl film, or the like, and is preferably sterilized using, for example, ethylene oxide gas. The first cover141has a tube shape having a shape in which one end in the tube axial direction is reduced in diameter toward the other end, the entire one end in the tube axial direction is secured to the outer periphery of the opening13aof the interior case13, and the other entire end in the tube axial direction is secured to the entire end opposite to the bottom wall side of the head cover54. The second cover142is also formed of a soft material such as a thin rubber film, a vinyl film, or the like, and is preferably sterilized using, for example, ethylene oxide gas. The second cover142has a tube shape having a shape in which one end in the tube axial direction is reduced in diameter toward the other end, the entire one end in the tube axial direction is secured to the outer periphery of the opening13bof the interior case13, and the other entire end in the tube axial direction is secured to the unit body31of the holding unit3.

The controller includes: for example, a programmable logic controller (PLC) including a central processing unit (CPU) unit and an input/output control unit; and an input device, such as a keyboard and a touch panel, connected to the PLC. As illustrated inFIG.5, the controller100has a CPU unit101, a main storage102, an auxiliary storage103, an inputter105, interfaces106,104, and a bus109that connects the units with each other. The controller100also includes drive circuits107a,107b,107c,107d,107e,107f, and107g. The main storage102is a volatile memory such as, for example, a random access memory (RAM) and is used as a working area of the CPU unit101. The auxiliary storage103is a non-volatile memory, such as a semiconductor memory, and stores a program for realizing various functions of the controller100including a machining program. The inputter105includes the aforementioned input device and an interface for connecting the input device to the bus109. When the inputter105receives various operation information that is input by a user operating the input device, the inputter105outputs the received various operation information to the CPU unit101. The interface106is connected to the drive circuits107a,107b,107c,107d,107e,107f, and107gand converts control information input from the CPU unit101into a control signal to output to the drive circuits107a,107b,107c,107d,107e,107f, and107g. The interface106is also connected to the proximity sensors34,55to convert the detection signal input from the proximity sensors34,55into detection signal information and output the detection signal information to the CPU unit101. The interface104outputs notification information that is input from the CPU unit101to the display panel11to notify a user of whether or not the tool20is broken.

The drive circuit107adrives the spindle drive51based on a control signal that is input via the interface106. The drive circuit107bdrives the lift drive44based on a control signal that is input via the interface106. The drive circuit107cdrives the X-direction drive71based on a control signal that is input via the interface106, and the drive circuit107ddrives the Y-direction drive76based on a control signal input via the interface106. The drive circuit107edrives the rotary drive81based on a control signal that is input via the interface106, and the drive circuit107fdrives the rotary drive86based on a control signal that is input via the interface106. The drive circuit107gdrives the chuck53based on a control signal that is input via the interface106.

The CPU unit101functions as a head controller111, a holding unit controller112, a signal acquirer113, a determiner114, and a notifier115by reading the aforementioned program stored in the auxiliary storage103into the main storage102and executing the program. The auxiliary storage103also includes a reference signal waveform storage131that stores signal waveform information that is obtained by the proximity sensor34and reflects the shape of the tool20before cutting machining of the workpiece W serving as a reference for determining whether or not the tool20is broken. The main storage102temporarily stores signal waveform information indicating the waveform of a detection signal of the proximity sensor34with regard to the tool20after cutting machining of the workpiece W and signal waveform information indicating the waveform of a detection signal of the proximity sensor55with regard to the workpiece W. The reference signal waveform storage131stores signal waveform information indicating the signal waveform of a detection signal that is output from the proximity sensor34when the rotary spindle52is rotated in a state in which the head5is moved so that the proximity sensor34provided in the holding unit3faces a lateral side of the tool20before cutting machining of the workpiece W, in association with the tool identification information that identifies the tool20.

The signal waveform storage121temporarily stores signal waveform information indicating the waveform of a detection signal that is output from the proximity sensor34when the rotary spindle52is rotated in a state in which the head5is moved so that the proximity sensor34provided in the holding unit3faces the lateral side of the tool20after cutting machining of the workpiece W. The signal waveform storage121further temporarily stores signal waveform information indicating the waveform of a detection signal that is output from the proximity sensor55when the workpiece holder32is rotated in a state in which the head5is moved so that the proximity sensor55provided in the head5faces the lateral side of the workpiece W after cutting machining of the workpiece W.

The head controller111generates control information for rotating the rotary spindle52or maintaining the rotary spindle52in a non-rotating state in accordance with the method of cutting machining the workpiece W, and outputs the control information to the interface106. At this time, the drive circuit107aoperates or stops the spindle drive51based on the control signal input from the interface106. The head controller111also generates control information for raising and lowering the head5in accordance with the machining program according to the shape of the workpiece W and outputs the control information to the interface106. At this time, the drive circuit107boperates the lift drive44based on the control signal input from the interface106. The head controller111also generates control information for causing the chuck53to hold or release the tool20and outputs the control information to the interface106. At this time, the drive circuit107gcauses the chuck53to be a holding state of the tool20or to release the holding state of the tool20based on the control signal input from the interface106. Furthermore, the head controller111generates control information for moving the head5in the X-axis direction and the Y-axis direction and outputs the control information to the interface106. At this time, the drive circuits107cand107drespectively operate or stop the X-direction drive71and the Y-direction drive76based on the control signal input from the interface106.

The head controller111also generates control information for moving the head5so that the sensor part341of the proximity sensor34provided in the holding unit3faces the lateral side of the tool20before and after cutting machining of the workpiece W, as illustrated inFIG.6A, and outputs the control information to the interface106. Furthermore, after cutting machining of the workpiece W, the head controller111generates control information for moving the head5so that the proximity sensor55provided in the head5faces the lateral side of the workpiece W and outputs the control information to the interface106, as illustrated inFIG.6B.

Returning toFIG.5, the holding unit controller112generates control information for rotating the entire unit body31about the B-axis JB and outputs the control information to the interface106. At this time, the drive circuit107eoperates or stops the rotary drive81based on the control signal input from the interface106. The holding unit controller112also generates control information for rotating the workpiece holder32about the C-axis JC and outputs the control information to the interface106. At this time, the drive circuit107foperates or stops the rotary drive86based on the control signal input from the interface106.

The signal acquirer113obtains detection signal information indicating an intensity of a detection signal that is output from the proximity sensors34,55. Here, the signal acquirer113obtains detection signal information indicating an intensity of a detection signal that is output from the proximity sensor34when the rotary spindle52of the head5is rotated in a state in which the head5is moved so that the sensor part341of the proximity sensor34faces a lateral side of the tool20, as illustrated inFIG.6A, before cutting machining of the workpiece W. The signal acquirer113then stores the detection signal information of the proximity sensor34obtained for each of the plurality of tools20to be used in the cutting machining in the reference signal waveform storage131as reference signal waveform information in association with sampling time information indicating sampling time by the proximity sensor55and tool identification information of each of the plurality of tools20, before the cutting machining of the workpiece W. The signal acquirer113also obtains detection signal information indicating an intensity of a detection signal that is output from the proximity sensor34when the rotary spindle52of the head5is rotated in a state in which the head5holding the tool20used in the cutting machining is moved so that the proximity sensor34faces the lateral side of the tool after the cutting machining of the workpiece W. Then, the signal acquirer113stores the detection signal information of the proximity sensor34obtained after the cutting machining of the workpiece W in the signal waveform storage121in association with the sampling time information indicating the sampling time by the proximity sensor55.

Furthermore, after the cutting machining of the workpiece W using the tool20, the signal acquirer113obtains detection signal information indicating an intensity of a detection signal that is output from the proximity sensor55when the workpiece holder32is rotated in a state in which the head5is moved so that the sensor part551of the proximity sensor55faces a lateral side of the workpiece W, as illustrated inFIG.6B. Then, the signal acquirer113stores the detection signal information of the proximity sensor55obtained after the cutting machining of the workpiece W in the signal waveform storage121in association with the sampling time information indicating the sampling time by the proximity sensor55.

The determiner114determines whether or not the tool20is broken based on the intensity of the detection signal indicated by each of the detection signal information obtained by the proximity sensor34before and after the cutting machining of the workpiece W, that is, whether there is a difference in the signal waveforms corresponding to time transitions in the amplitude values of the detection signals. Specifically, the determiner114first performs processing for synchronizing the sampling time for the detection signal information constituting the reference signal waveform information stored in the reference signal waveform storage131and the sampling time for the detection signal information obtained by the proximity sensor34stored in the signal waveform storage121. Next, the determiner114calculates a difference value between the amplitude value indicated by the detection signal information constituting the reference signal waveform information and the amplitude value indicated by the detection signal information stored in the signal waveform storage unit121at the same sampling time for all sampling times that are synchronized with each other, and calculates the sum of the calculated difference values as a difference integration value. Then, when the calculated difference integration value is greater than or equal to a preset difference integration threshold, the determiner114determines that the tool20is broken. In addition, the determiner114determines whether there is a broken piece of the tool20attached to the workpiece W based on the signal waveform information obtained by the proximity sensor55after the cutting machining of the workpiece W. Specifically, the determiner114determines that a broken piece of the tool20is attached to the workpiece W, for example, when a peak waveform is present in the signal waveform corresponding to the time transition of the amplitude value of the detection signal indicated by each of the detection signal information obtained by the proximity sensor55and stored in the signal waveform storage unit121, and the difference value between the peak value of the peak waveform and the average value of the signal waveform is greater than or equal to a preset difference threshold.

Based on the result of the determination performed by the determiner114, the notifier115generates notification information for notifying an operator of whether or not the tool20is broken and whether or not a broken piece of the tool20is attached to the workpiece W, and outputs the notification information to the interface104.

Next, the cutting machining processing performed by the cutting machining apparatus1according to the present embodiment is described with reference toFIGS.7to9. Here, the cutting machining apparatus1is described as executing at least one machining step on a workpiece W in the cutting machining processing. In addition, in an initial state, the holding unit3is assumed to be maintained in a posture in which the tool holder33is oriented toward the +Z direction side. Furthermore, in the initial state, the head5is assumed to be positioned in the initial position on the +Z direction side of the holding unit3. First, as illustrated inFIG.7, when the cutting machining processing is started, the cutting machining apparatus1specifies one tool20from among at least one tool20to be used in the cutting machining (step S1). Next, the cutting machining apparatus1moves the head5to a position for receiving the specified tool20and causing the head5to hold the specified tool20(step S2). Specifically, the head controller111specifies one tool20from among the at least one tool20to be used in the cutting machining and controls the operation of the X-direction drive71and the Y-direction drive76so that the head5moves from the aforementioned initial position to the +Z direction side of the specified tool20. In addition, the holding unit controller112rotates the holding unit3about the B axis JB to control the operation of the rotary drive81so that the workpiece W held in the holding unit3becomes a posture oriented vertically upward. The head controller111then controls the operation of the lift drive44to lower the head5in the −Z direction to move the head5to a position for receiving the specified tool20. Furthermore, the head controller111controls the operation of the chuck53so that the chuck53holds the specified tool20in a state in which the head5is arranged at a position for receiving the specified tool.

Subsequently, the cutting machining apparatus1moves the head5to a position where the tool20held by the head5faces the proximity sensor34of the holding unit3(step S3). Specifically, the head controller111controls the operation of the X-direction drive71, the Y-direction drive76, and the lift drive44so that the head5is arranged at a position where the sensor part341of the proximity sensor34provided in the holding unit3becomes a state facing a lateral side of the tool20, as illustrated inFIG.6A. Returning toFIG.7, the cutting machining apparatus1then obtains signal waveform information that is obtained by the proximity sensor34while rotating the tool20and stores the signal waveform information in the reference signal waveform storage131(step S4). Specifically, the signal acquirer113obtains detection signal information indicating an intensity of a detection signal that is output from the proximity sensor34while the head controller111controlling the operation of the spindle drive51so that the rotary spindle52holding the tool20rotates at a preset rotational speed. Then, the signal acquirer113stores the obtained detection signal information in the reference signal waveform storage unit131in association with the sampling time information and the tool identification information of the specified tool20. The head controller111stops the rotation of the rotary spindle52after rotating the rotary spindle52for a preset number of rotations. Next, the cutting machining apparatus1moves the head5to a position for transferring the tool20held in the head5to the holding unit3, and then causes the tool20held in the head5to be stored in the tool holder33of the holding unit3(step S5). Specifically, the head controller111controls the operation of the X-direction drive71, the Y-direction drive76, and the lift drive44so that the head5is arranged at a position where a portion of the tool20held in the head5becomes a state disposed inside the tool holder33of the holding unit3. In addition, the holding unit controller112rotates the holding unit3about the B axis JB to control the operation of the rotary drive81so that the workpiece W held in the holding unit3becomes a posture oriented vertically upward. The head controller111then controls the operation of the chuck53to release the holding of the tool20by the chuck53.

Subsequently, the cutting machining apparatus1determines whether or not the acquisition of the signal waveform information has been completed for all the tools20used in the cutting machining processing (step S6). Here, it is assumed that the cutting machining apparatus1determines that, of all the tools20used in the cutting machining processing, there is a tool20of which signal waveform information has not yet been obtained (step S6: No). In this case, the cutting machining apparatus1specifies one of the tools20of which signal waveform information has not yet acquired (step S1), and executes a series of processing after step S2onward again. On the other hand, it is assumed that the cutting machining apparatus1determines that the acquisition of the signal waveform information has been completed for all the tools20used in the cutting machining processing (step S6: Yes). In this case, the cutting machining apparatus1specifies the tool20to be used in the first machining step according to the machining program and holds the specified tool20(step S7). The cutting machining apparatus1then moves the head5to a position for receiving the specified tool20and then causes the head5to hold the specified tool20(step S8). Next, the cutting machining apparatus1starts one machining step included in the cutting machining processing (step S9). Specifically, in accordance with the content of the machining step, the head controller111controls the operation of the spindle drive51, the X-direction drive71, the Y-direction drive76, and the lift drive44to move the head5so that the tip of the tool20contacts the workpiece W while rotating the rotary spindle52holding the tool20. Here, the holding unit controller112controls the operation of the rotary drive81so that the workpiece holder32maintains a posture oriented toward the +Z direction or a direction tilted from the Z axis in accordance with the content of the machining step. Alternatively, the head controller111controls the operation of the spindle drive51, the X-direction drive71, the Y-direction drive76, and the lift drive44to move the head5so that the tip of the tool20contacts the workpiece W while maintaining a state in which the rotary spindle52holding the tool20stops in accordance with the content of the machining step. Here, the holding unit controller112controls the operation of the rotary drives81,86so that the workpiece holder32maintains a posture oriented toward the +Z direction or a direction tilted from the Z axis while rotating the workpiece holder32in accordance with the content of the machining step.

Subsequently, when one machining step ends (step S10), the cutting machining apparatus1moves the head5to a position where the tool20held in the head5faces the proximity sensor34of the holding unit3as illustrated inFIG.6A(step S11). Returning toFIG.7, the cutting machining apparatus1then obtains the signal waveform information obtained by the proximity sensor34while rotating the tool20and stores the signal waveform information in the signal waveform storage unit121(step S12).

Next, the cutting machining apparatus1determines whether or not there is a difference in the signal waveforms indicated by the signal waveform information obtained by the proximity sensor34before and after the machining step (step S13). Specifically, the determiner114compares a signal waveform corresponding to the time transition of the amplitude value of the detection signal indicated by the detection signal information that is obtained by the proximity sensor34and stored in the signal waveform storage121and a signal waveform corresponding to the time transition of the amplitude value of the detection signal indicated by the detection signal information that is stored in the reference signal waveform storage131, and determines whether or not there is a difference in the signal waveforms. Here, the determiner114determines that there is a difference in the signal waveforms when the signal waveform corresponding to the reference signal waveform information is, for example, the waveform illustrated inFIG.8A, and the signal waveform corresponding to the detection signal information stored in the signal waveform storage unit121is different from the signal waveform illustrated inFIG.8A, for example, as illustrated inFIG.8B. Returning toFIG.7, when the cutting machining apparatus1determines that there is a difference in the signal waveforms (step S13: Yes), the cutting machining apparatus1performs the processing of step S15described later. On the other hand, when the cutting machining apparatus1determines that the signal waveforms are the same (step S13: No), the cutting machining apparatus1determines whether or not all the machining steps included in the cutting machining processing have ended (step S14). Here, it is assumed that the cutting machining apparatus1determines that there is a machining step that has not yet ended among the machining steps included in the cutting machining processing, (step S14: No). In this case, the cutting machining apparatus1specifies the tool20to be used in the next machining step (step S7) and executes the series of processing from step S8onwards again.

On the other hand, when the cutting machining apparatus1determines that all the machining steps included in the cutting machining processing have ended (step S14: Yes), the cutting machining apparatus1moves the head5to a position where the proximity sensor55of the head5faces the workpiece W, as illustrated inFIG.9(step S15). Specifically, the head controller111controls the operation of the X-direction drive71, the Y-direction drive76, and the lift drive44so that the sensor part551of the proximity sensor55provided in the head5is arranged at a position facing a lateral side of the workpiece W held in the workpiece holder32as illustrated inFIG.6B. Returning toFIG.9, the cutting machining apparatus1then obtains signal waveform information obtained by the proximity sensor55while rotating the workpiece W and stores the signal waveform information in the signal waveform storage unit121(step S16). Specifically, w % bile the holding unit controller112controls the operation of the rotary drive86to rotate the workpiece holder32that holds the workpiece W, the signal acquirer113obtains detection signal information indicating an intensity of a detection signal that is output from the proximity sensor55, and stores the obtained detection signal information in the signal waveform storage unit121in association with sampling time information. Thereafter, the cutting machining apparatus1determines whether or not there is a broken piece of the tool20attached to the workpiece W based on the signal waveform corresponding to the time transition of the amplitude value of the detection signal indicated by the detection signal information that is obtained by the proximity sensor55and stored in the signal waveform storage121(step S17). Next, the cutting machining apparatus1generates notification information for notifying an operator whether or not the tool20is broken and whether or not a broken piece of the tool20is attached to the workpiece W, and displays the notification information on the display panel11(step S18). Specifically, the notifier115generates notification information indicating the result of the determination performed by the determiner114and outputs the notification information to the interface104. Then, the cutting machining processing ends.

As described thus far, with the cutting machining apparatus1according to the present embodiment, the signal acquirer113obtains detection signal information indicating an intensity of a detection signal that is output from the proximity sensor34when the rotary spindle52is rotated in a state in which the head5is moved so that the proximity sensor34is disposed on a lateral side of the tool20before and after the cutting machining of the workpiece W. Then, the determiner114determines whether or not the tool20is broken based on whether or not there is a difference in the signal waveforms corresponding to the time transitions in the intensities of the detection signals indicated by the detection signal information obtained before and after the cutting machining. This makes it possible to quickly detect a breakage of the tip of the tool20during cutting machining of the workpiece W, thereby improving the machining accuracy of the workpiece W.

Incidentally, when the dimensions of a workpiece W become smaller, the dimensions of the tool20used for machining the workpiece W also become smaller accordingly. In a case where the workpiece W is subjected to micro-cutting machining, even a micro crack occurring in the tool20greatly affects the machining accuracy. However, a micro crack in the tool20may not be visible to an operator. To address such a problem, the cutting machining apparatus1according to the present embodiment utilizes a correlation between the waveform of the detection signal that is output from the proximity sensor34and the shape of the tool20to detect the presence of a breakage in the tool20during cutting machining by obtaining detection signal information indicating the amplitude of a detection signal that is output from the proximity sensor34while rotating the rotary spindle52holding the tool20before and after cutting machining of the workpiece W and comparing the signal waveforms corresponding to the time transitions of the amplitudes of the detection signals indicated by the obtained detection signal information. This makes it possible to detect a micro crack in the tool20that is difficult for an operator to visually check.

In addition, the proximity sensor34according to the present embodiment is disposed inside the unit body31of the holding unit3, and the proximity sensor55is disposed inside the head cover54. In this way, the proximity sensors34,55are arranged in a state isolated from the machining area S1, so that the cleanliness of the machining area S1can be maintained. In addition, cleaning, sterilization, or other processing of the proximity sensors34,55are not necessary for each cutting machining of the workpiece W, providing an advantage in that the workload of the operator performing cutting machining of the workpiece W is reduced.

Furthermore, the signal acquirer113according to the present embodiment obtains signal waveform information indicating the waveform of a detection signal that is output from the proximity sensor55when the workpiece holder32is rotated in a state in which the head5is moved so that the proximity sensor55faces a lateral side of the workpiece W after cutting machining of the workpiece W. Then, the determiner114determines whether or not there is a broken piece of the tool20attached to the workpiece W based on the signal waveform information obtained from the proximity sensor55. This makes it possible to detect attachment of a broken piece to the workpiece W that is generated when the tool20broke. Accordingly, for example, a workpiece W having a machining defect due to a breakage of the tool20can be prevented from flowing out to a post-process after the process of the cutting machining processing.

In addition, in the cutting machining apparatus1according to the present embodiment, the workpiece holder32, the tool holder33, and the chuck53are disposed inside the interior case13, the first cover141occludes between the head5and the outer periphery of the opening13ain the interior case13, and the second cover142occludes between the holding unit3and the outer periphery of the opening13bin the interior case13. The tool holder33is also secured to the unit body31in such a way that, in a state in which the tool20is not inserted in the tool holder33, the inside of the tool holder33is in communication with the outside of the unit body31of the holding unit3and the outer wall of the tool holder33is isolated from the outside of the unit body31. As a result, the machining area S1where cutting machining is conducted and that is isolated from the outside of the interior case13can be formed inside the interior case13, thereby suppressing foreign matters present outside the interior case13from entering into the machining area S1.

Although an embodiment of the present disclosure has been described above, the present disclosure is not limited to the configuration of the aforementioned embodiment. For example, as illustrated inFIG.10, the holding unit may have a proximity sensor2034disposed in the vicinity of a portion where the blade21of the tool20is stored in the tool holder33. In this case, the controller may include: a type specifier that specifies the type of the blade21of the tool20based on a detection signal output from the proximity sensor2034in a state in which the tool20is held in the tool holder33; and a type determiner that determines whether or not the type of the tool20specified by the type specifier and the type of the tool20that is set in advance to be held by each tool holder33.

According to this configuration, the occurrence of a setting error of the tool20in the tool holder33can be suppressed.

In an embodiment, the cutting machining apparatus1may move the head5to a position where the workpiece W faces the proximity sensor55of the head5just prior to starting the machining step to obtain signal waveform information while rotating the workpiece W and specify the shape of the workpiece W held in the workpiece holder32based on the obtained signal waveform information. The cutting machining apparatus1may then specify the type of the tool20to be used in the machining step based on the shape of the specified workpiece W.

The present disclosure is suitable as a cutting machining apparatus for cutting machining of bones.