Seat confirmation method and seat confirmation device for a machine tool

Abstract

A seat confirmation procedure for confirming the presence or absence of close contact between a tool holder (14) and a seat surface (ES1, ES2) of a tool clamping device (16) of a machine tool (10) comprises the steps of: attaching the tool holder (14) with a predetermined seat confirmation clamping force less than a standard clamping force with which the tool clamping device (16) attaches the tool holder (14) when the machine tool is in operation; detecting a seat condition between the seat surface (ES1, ES2) and the tool holder (14) when the tool holder (14) is attached with the seat confirmation clamping force; and assessing the acceptability of the results of detecting the seat condition.

Description

Area The present invention relates to a seat confirmation method and a seat confirmation device for a machine tool. background To automate machining, it is desirable to automatically detect whether removable elements such as tool holders and workpiece pallets, which are attached to and removed from the machine tool, are properly clamped to the machine tool. Patent literature 1 discloses a tool attachment confirmation device that eliminates the escape of supply air to confirm the tight contact of a tool attached to a spindle, thereby enabling confirmation of the tool's tight contact.However, if foreign matter such as thin chips (e.g., 10 µm to 30 µm) become trapped between the spindle and the tool in a machine tool using a spindle tool, and the tool is clamped with a predetermined clamping force, the gap disappears due to the elastic deformation of the foreign matter, as well as the tool holder and the spindle element around the foreign matter. Therefore, if, for example, an attempt is made to confirm the seat by passing air over the seat surface and measuring the pressure and flow rate with a pneumatic seat sensor, the pressure in the airflow path, which has no gaps, will be high, or the flow rate will be zero. This presents a problem in that it is unclear whether the removable element is properly clamped or whether a small foreign matter is trapped within it. Furthermore, patent literature 2 discloses a tool clamping device that can detect a decrease in tool clamping force due to age-related deterioration of a preloading element by compressing a disc spring in a disengagement direction with a second pressure that is lower than a first pressure used in normal disengagement and by detecting the magnitude of the compression. However, patent literature 2 does not disclose how the jamming of foreign objects on the tool's seating surface is detected. Citation list Patent literature [PTL 1] Japanese Unexamined Patent Publication (Kokai) No. 2001-259906 [PTL 2] Japanese Unexamined Patent Publication (Kokai) No. 2019-14017 Summary Technical problem In general, accurately detecting the presence of small foreign bodies requires either the use of expensive sensors or measuring the runout accuracy of the tool attached to the spindle with each tool change, which is impractical for general-purpose machine tools. Given the above circumstances, it is an object of the present invention to provide a seat confirmation method and seat confirmation device for a machine tool that can automatically, accurately, and easily confirm that removable elements such as tools, pallets, and workpieces are seated on a mounting surface without any foreign bodies being trapped between them. Problem solving According to one aspect of the present invention, a seat confirmation method for a machine tool is provided for confirming the presence or absence of close contact between a removable element and a seat surface of a removal mechanism of a machine tool, wherein the method comprises the following steps: attaching the removable element with a predetermined seat confirmation clamping force that is less than a standard clamping force with which the removal mechanism attaches the removable element when the machine tool is in operation, detecting a seat condition between the seat surface and the removable element when the removable element is attached with the seat confirmation clamping force, and assessing the acceptability of the results of detecting the seat condition. According to one aspect of the present invention, a seat confirmation device for a machine tool is provided for confirming the presence or absence of close contact between a removable element and a seat surface of a removal mechanism of a machine tool, the device comprising: a removal mechanism capable of switching between at least two clamping forces, including a standard clamping force with which the removal mechanism engages the removable element when the machine tool is in operation, and a predetermined seat confirmation clamping force that is less than the standard clamping force; a seat detector for detecting a seat condition between the seat surface and the removable element; and a control element that adjusts a clamping force of the removal mechanism to the seat confirmation clamping force in order to detect a seat condition by means of the seat detector.and assesses the acceptability of the results of the assessment of sitting posture. Advantageous effects of the invention According to the seat confirmation method for a machine tool according to one aspect of the present invention, a removable element is fitted with a seat confirmation clamping force that is lower than the standard clamping force when the machine tool is in operation, thereby allowing the seat condition between the seat surface and the removable element to be accurately detected. If a small foreign object is trapped against the seat surface, the predetermined clamping force causes the gap to disappear due to the elastic deformation of the foreign object, the surrounding removable element, and the seat surface element. However, with the seat confirmation clamping force, the elastic deformation is small, and a gap remains. If the seat condition is adequate with the seat confirmation clamping force, the presence of a foreign object can be detected, and the workpiece can be machined safely and accurately with the predetermined clamping force.As a result, it can be automatically, accurately and easily confirmed whether a removable element such as a tool, pallet or workpiece is resting on the seat surface with a foreign object wedged between it and the seat. The seat confirmation device for a machine tool according to one aspect of the present invention comprises a removal mechanism capable of switching between at least two clamping forces, including a standard clamping force with which the removal mechanism secures the removable element when the machine tool is in operation, and a predetermined seat confirmation clamping force that is less than the standard clamping force. The seat confirmation device further comprises a seat detector for detecting a seat condition between the seat surface and the removable element, and a control element that adjusts the clamping force of the removal mechanism to the seat confirmation clamping force in order to detect a seat condition by means of the seat detector. Thus, the seat condition between the seat surface and the removable element can be accurately detected by securing the removable element with a seat confirmation clamping force that is less than the standard clamping force.If a small foreign object is wedged in the seat, the predetermined clamping force would eliminate the gap due to the elastic deformation of the foreign object and the removable element and seat element surrounding it. However, with the seat confirmation clamping force, the elastic deformation is minimal, and a gap remains. If the seating condition is appropriate with the seat confirmation clamping force, it can detect whether a foreign object is wedged, and the workpiece can be machined safely and accurately with the predetermined clamping force. Consequently, the seat confirmation device can automatically, accurately, and easily confirm whether a removable element, such as a tool, pallet, or workpiece, is seated on the seat with a foreign object wedged between them. Brief description of the drawings Fig. 1 shows a side view in cross-section of a seat confirmation device for a machine tool according to a first embodiment. Fig. 2 shows a block diagram of the seat confirmation device for a machine tool according to the first embodiment. Fig. 3 shows a flow diagram of the seat confirmation according to the first embodiment. Fig. 4 shows a side view of a seat confirmation device for a machine tool according to a second embodiment. Fig. 5 shows a side view in cross-section of the seat confirmation device for a machine tool according to the second embodiment. Fig. 6 shows a side view in cross-section of a seat confirmation device for a machine tool according to a third embodiment. Description of the embodiments The seat confirmation device for a machine tool according to one embodiment is described below with reference to the accompanying drawings. Identical or corresponding elements have been assigned the same reference numerals, and repetition of these descriptions has been omitted. For ease of understanding, the scale of the drawings may have been changed in some cases. (First embodiment) Fig. 1 shows a schematic side view in cross-section of a spindle device 12 as a seat confirmation device for a machine tool 10 according to a first embodiment. The spindle device 12 includes a tool clamping device 16 as a removal mechanism for attaching and removing a tool holder 14 as a removable element. The spindle device 12 comprises a spindle head 12a as a housing and a spindle 12b, which is rotatably arranged inside the spindle head 12a. The spindle 12b is held inside the spindle head 12a by a bearing 18 and is arranged so that it is rotatable relative to the spindle head 12a. A built-in motor 20 is integrated in the section where the spindle head 12a and the spindle 12b are opposite each other and can drive and mechanically rotate the spindle 12b. The spindle device 12 is configured to rotate the tool TL and the tool holder 14 by mounting the tool holder 14, to which the tool TL is attached, on the spindle 12b, thereby performing cutting and other machining operations using the tool TL. The tool holder 14 comprises a flanged section 30, which rests on a first seating surface ES1 at one end of the spindle 12b, and a hollow, conical shank section 32, which extends along the longitudinal direction of the spindle 12b and whose diameter gradually decreases from the flanged section 30 to the rear end of the spindle 12b. Furthermore, an engagement element 32a, which projects radially inward along the inner circumference of the shank section 32 toward the spindle 12b, is formed at the rear end of the shank section 32. The tool clamping device 16 comprises a rod-shaped drawbar 22, which is arranged in the central section of the spindle 12b so that it is movable within the spindle 12b along the longitudinal direction. The drawbar 22 has a recessed section 26 at its front end, specifically at the end that is attached to the tool TL and tool holder 14. This recessed section is designed to have a smaller outer diameter than other sections of the drawbar 22. A plurality of collets 28, arranged in a cylindrical shape such that their front ends can expand and contract radially, are located around the outer circumference of the recessed section 26. The drawbar 22 and the collets 28 are each configured to be movable independently of one another within the spindle 12b. Furthermore, the tip portions of the collets 28 are designed to have a larger outer diameter in the longitudinal direction than other sections.When the tool holder 14 is attached to the spindle 12b by a tool changing device (figure omitted), the drawbar 22 is first moved towards the tip by a release piston 40, which will be described later. Then, the tip side of the collet 28 is retracted into the recess part 26 by a preloading device (figure omitted), and its outer diameter becomes smaller than the inner diameter of the engagement part 32a. The tool holder 14 is inserted into a tapered hole 12c in the spindle 12b until the rear end face of the flange part 30 of the tool holder 14 contacts the first seating surface ES1 of the tip of the spindle 12b. When the release piston 40 then moves backward, the drawbar 22 is moved backward by the preload force of a disc spring 34, which will be described later.The tip portion of the drawbar 24, which has a larger outer diameter, then presses radially from the inside out against the tip side of the collet 28, expanding its diameter and engaging the engagement portion 32a, thereby pulling the tool holder 14 backward. Simultaneously, it expands the diameter of the shank portion 32, causing it to contact a second seating surface ES2, which is the inner surface of the tapered hole 12c of the spindle 12b. This secures or clamps the tool holder 14 on the spindle 12b at two surfaces in the axial and radial directions. The description given here uses a tool holder with two surfaces, such as a so-called "HSK shank," as an example, but is not limited to this; a tool holder with a single surface, such as the so-called "BT shank," can also be used.In this case, there is no first seating surface ES1 between the flange of the tool holder and the end face of the spindle, and there is only a second seating surface ES2 between the shank of the tool holder and the tapered hole of the spindle. Therefore, it can be understood that a tip-side flow path 50b is closed at the spindle tip side and air is only discharged from a branched flow path 54. Furthermore, a disc spring 34 is arranged longitudinally at the rear end of the spindle 12b, and a retaining nut 36 located at the rear end of the disc spring 34 restricts its movement beyond the retaining nut 36. The disc spring 34 is designed to bias the drawbar 22 from its front end to its rear end, and more precisely in the direction of the drawbar 22's insertion into the spindle 12b. As a result, the shaft section 32 pulls the tool holder 14, which engages with the collet 28, towards the spindle 12b, thereby clamping the tool holder 14 securely to the spindle 12b. A release cylinder 38 for releasing the clamping of the tool holder 14 is arranged at the rear end of the spindle assembly 12. A release piston 40, which is hydraulically actuated, is arranged inside the release cylinder 38. The release piston 40 is configured to be movable along the longitudinal direction of the spindle 12b and the drawbar 22, and is configured to contact and press against the rear end of the drawbar 22 when it is moved towards the front end of the spindle 12b. A piston body 40a of the release piston 40 divides the interior of the release cylinder 38 into a front end chamber and a rear end chamber, thus forming a front chamber 44 and a rear chamber 42. The front chamber 44 and the rear chamber 42 are configured to be connected to a hydraulic power source 64 or an oil tank 66 via a switchable first solenoid valve 60. The first solenoid valve 60 is configured to switch between three modes. In forward mode 60a, the oil in the front chamber 44 can flow into the oil tank 66, and hydraulic pressure is exerted on the rear chamber 42. By decreasing the hydraulic pressure in the front chamber 44 and increasing the hydraulic pressure in the rear chamber 42 in this way, the piston body 40a can be moved toward the drawbar 22, and the drawbar 22 can be pushed toward the tip. In reverse mode 60c, the oil in the rear chamber 42 can flow into the oil tank 66, and hydraulic pressure is exerted on the front chamber 44.By reducing the hydraulic pressure in the rear chamber 42 and increasing the hydraulic pressure in the front chamber 44 in this way, the piston body 40a can be moved rearward and away from the pull rod 22. Furthermore, in neutral mode 60b, no hydraulic pressure is exerted on the release piston 40. When the piston body 40a is moved in forward mode 60a towards the drawbar 22 and the drawbar 22 is pushed towards the tip, the tip portion of the drawbar 24, which was pressed into the collet 28, moves towards the tip of the spindle 12b. As a result, the tip of the collet 28 moves into the recess portion 26 and, since it is no longer pressed by the tip portion of the drawbar 24, its diameter is reduced by the clamping element. Consequently, the engagement between the collet 28 and the engagement portion 32a of the shank portion 32 is released, and the locking of the tool holder 14 on the spindle 12b is released, i.e., disengaged. Furthermore, an electromagnetic proportional control valve 62 is connected between the hydraulic power source 64 and the unclamping piston 40. The electromagnetic proportional control valve 62 is configured to change the opening degree of the relief valve depending on the current supplied to the solenoid, thereby adjusting the hydraulic pressure exerted on the unclamping piston 40. The hydraulic pressure can be switched between two stages, including high pressure (e.g., 7 MPa) and low pressure (e.g., 2 MPa). The high pressure exerted on the rear chamber 42 of the unclamping piston 40 (7 MPa in the present embodiment) corresponds to the unclamping force required to unclamp the tool holder 14. The predetermined clamping force required to fully engage the tool holder 14 on the spindle 12b corresponds to this unclamping force.Alternatively, a dual-pressure valve can be used to switch between high pressure and low pressure instead of the electromagnetic proportional control valve 62. The low hydraulic pressure (2 MPa in the present embodiment) exerted on the rear chamber 42 of the release piston 40 is set to a pressure lower than the release force, thus preventing the toolholder 14 from being fully released. Therefore, when the release piston 40 presses on the drawbar 22 at this low pressure, a condition is created in which the toolholder 14 is loosely clamped to the spindle 12b. This is referred to below as the intermediate clamping condition. The clamping force, which is lower than the predetermined clamping force and causes the intermediate clamping condition, is referred to as the seat confirmation clamping force. Furthermore, the release piston 40 remains stationary in the neutral mode 60b, without pressing on the drawbar 22, since no hydraulic pressure is exerted on the release piston 40. One embodiment in which the hydraulic pressure can be switched between two stages is described below; however, the present invention is not limited thereto, and the hydraulic pressure can be switched between several stages to confirm a seating condition in more detail, depending on the intended use of the machine tool. Furthermore, the high pressure of the hydraulic pressure, corresponding to the predetermined clamping force, is set to 7 MPa and the low pressure, corresponding to the seating confirmation clamping force, to 2 MPa; however, such predetermined clamping force and seating confirmation clamping force can be adjusted according to the dimensions and intended use of the machine tool. An airflow path 48 in the form of a tube extending along the longitudinal direction of the spindle 12b is formed inside the release piston 40. The airflow path 48 is connected to an air supply source 58, and air supplied by the air supply source 58 can flow through its interior. A pneumatic seat sensor 46 is also arranged (connected) between the airflow path 48 and the air supply source 58, which can detect the pressure or flow rate of the air flowing in from the air supply source 58. A spindle-side flow path 50, which connects to the airflow path 48 when the release piston 40 contacts the pull rod 22 to press against it, and which allows air to flow from the rear end of the pull rod 22 to the first seating surface ES1 of the spindle 12b, is formed inside the spindle 12b. The spindle-side flow path 50 has a tubular rear flow path 50a extending longitudinally from the rear end of the pull rod 22, which the release piston 40 contacts (presses), and a tubular tip-side flow path 50b extending radially outside the pull rod 22 such that it connects to the rear flow path 50a and extends to the first seating surface ES1.Furthermore, the spindle-side flow path 50 includes an adjusting element 52, which is formed in the section on the side of the pull rod 22 where the rear flow path 50a and the tip-side flow path 50b are connected, and which has a length along the longitudinal direction of the pull rod 22. Thus, even if the positional relationship between the rear flow path 50a and the tip-side flow path 50b changes when the pull rod 22 moves within the spindle 12b for clamping or unclamping, their connection is maintained, and air can flow from the rear flow path 50a to the tip-side flow path 50b. In addition, a branched flow path 54 is formed in the spindle-side flow path 50, branching off from the tip-side flow path 50b to allow air to flow to the second seat surface ES2. The pneumatic seat sensor 46 and the airflow path 48 are connected to the air supply source 58 via a switchable second solenoid valve 56. The second solenoid valve 56 is configured to switch between two modes. In air discharge mode 56a, air discharged (sent) from the air supply source 58 can flow through the airflow path 48 and the spindle-side flow path 50 to the first seat ES1 and second seat ES2. This allows for the removal of chips and dust around the first seat ES1 and second seat ES2 before the tool holder 14 is attached, thus cleaning the first seat ES1 and second seat ES2. If cleaning is not performed and the seat condition described later is not confirmed, the second solenoid valve 56 is switched to air intake mode 56b, and the airflow path 48 is opened to atmospheric pressure through a drain pipe 56c. The pneumatic seat sensor 46 and the air supply source 58 arranged in the machine tool 10 also function as a seat detector for the spindle device 12. More precisely, when the tool holder 14 is fully attached to the spindle 12b, the flange part 30 is in close contact with the first seat surface ES1 and the second seat surface ES2. Thus, the tip of the tip-side flow path 50b is closed by the flange part 30, and the branched flow path 54 is closed, i.e., sealed, by the shank part 32.If, in this state, the second solenoid valve 56 is set to air release mode 56a and air is directed from the air supply source 58 to the first seat ES1 and to the second seat ES2, once the spindle-side flow path 50 is sufficiently filled with air, the air stops flowing to the spindle-side flow path 50, and the pneumatic seat sensor 46 detects a high pressure or a low flow rate. Furthermore, if the tool holder 14 is not attached to the spindle 12b (tool-free clamping state) or if the tool holder 14 is attached to the spindle 12b in an intermediate clamping state with foreign objects wedged between them, the tip-side flow path 50b and / or the branched flow path 54 are not closed, and the incoming air flows out of the tip of the tip-side flow path 50b. Thus, air flows continuously through the spindle-side flow path 50, and the pneumatic seat sensor 46 detects either a low pressure or a high flow rate.Based on the pressure or flow rate detected by the pneumatic seat sensor 46, the spindle device 12 can determine whether the tool holder 14 is fully attached to the spindle 12b (clamping state), whether no foreign bodies are clamped in it (intermediate clamping state), whether it is not attached to the spindle 12b (tool-free clamping state), or whether foreign bodies are clamped in it (intermediate clamping state). On the other hand, chips and other deposits generated during machining can remain around the first seating surface ES1. If, in this condition, an attempt is made to attach the tool holder 14 to the spindle 12b, the chips can become trapped (jammed) between the flange part 30 and the first seating surface ES1 or between the shank part 32 and the second seating surface ES2. If the foreign body trapped in the seating surface ES1, ES2 is small, the gap disappears at the predetermined clamping force due to the elastic deformation of the foreign body and the removable element and seating surface element surrounding it. However, with the seat-confirming clamping force, the elastic deformation is small, resulting in a gap at the tip of the tip-side flow path 50b or the branched flow path 54.Even when chips are trapped in an intermediate state, the pneumatic seat sensor 46 can therefore detect a low pressure or a high flow rate. Furthermore, a plurality of pneumatic seat sensors 46 are arranged circumferentially in the tip-side flow path 50b and in the branched flow path 54 to prevent false detections. As described later, the spindle device 12 sets the pressure or flow rate that can occur in the pneumatic seat sensor 46 when chips are trapped in this manner as the first threshold. If, in the intermediate state, the pressure detected by the pneumatic seat sensor 46 is below the first threshold, or if the detected flow rate exceeds the first threshold, the spindle device 12 is configured to judge that chips are trapped between the flange part 30 and the seat surface ES1 and / or between the shaft part 32 and the second seat surface ES2.Furthermore, the spindle device 12 assesses that the seat of the tool holder 14 is appropriate if the pressure detected by the pneumatic seat sensor 46 exceeds the first threshold or if the detected flow rate falls below the first threshold. Furthermore, the pneumatic seat sensor 46 and the air supply source 58 can distinguish and assess whether small chips are clamped in the intermediate clamping state or whether the tool holder 14 is not attached to the spindle 12b. More precisely, the spindle device 12 defines the pressure or flow rate that the pneumatic seat sensor 46 can detect when the tool holder 14 is not attached to the spindle 12b as a second threshold, and if the pressure detected by the pneumatic seat sensor 46 is below the second threshold or if the detected flow rate exceeds the second threshold, it can be assessed that nothing is attached to the spindle 12b (tool-free clamping state).The spindle device 12 can detect the presence or absence of chips that hinder the attachment of the tool holder 14 to the spindle 12b by measuring the air pressure or the flow rate in this way, and further assesses the presence or absence of the tool holder 14 and the suitability of the seat. The first threshold can be determined based on the pressure or flow rate detected by the pneumatic seat sensor 46 when air is passed through the first seat ES1 and / or second seat ES2 of the spindle 12b, with shims (feeler gauges) of a predetermined thickness (10 µm, 20 µm, 30 µm, etc.) arranged as simulated chips, inserted between the flange part 30 of the toolholder 14 and the first seat ES1. Alternatively, the pressure or flow rate can be detected (measured) for a plurality of toolholder types 14 and shims of a plurality of thicknesses, and the first threshold can be set for each tool and machining target based on these results. Fig. 2 shows a block diagram of a seat confirmation device for a machine tool. The machine tool 10 includes a machine control 70 for its control. The machine control 70 is configured to include a seat confirmation control unit 72 as a control unit for controlling the seat confirmation of the spindle device 12. The machine control 70 further includes a spindle control unit 78, which is electrically connected to the spindle device 12, the release piston 40, the pneumatic seat sensor 46, the first solenoid valve 60, the second solenoid valve 56, and the electromagnetic proportional control valve 62, and controls these in conjunction with the seat confirmation control unit 72. The machine control 70 also includes a tool change control unit 80 for controlling the attachment, and more precisely the installation and removal, of the tool holder 14. The machine control 70 is also configured to be versatile enough to control devices other than the spindle device 12, which has a built-in tool clamping device 16, either simultaneously or by switching connections. For example, it is configured to control a table device 100 (see Fig. 4 and Fig. 5), which has a built-in pallet clamping device 106, and a workpiece clamping base 150 (see Fig. 6), which has a workpiece clamping device 156. Thus, the machine control 70 comprises a table control section 82 for controlling the table device 100 and a workpiece changer control section 84 for controlling the workpiece clamping base 150. Furthermore, an additional control section 86 is provided for controlling devices other than those mentioned above. The seat confirmation control unit 72 comprises an evaluation unit 74 for evaluating the seating condition of the tool holder 14 and a memory unit 76 for storing (recording) the first and second threshold values, which are threshold values ​​for the pneumatic seat sensor 46 for evaluating the seating condition and which are set in accordance with the specifications of the spindle device 12. The evaluation unit 74 is electrically connected to the spindle control unit 78 and is configured to evaluate the seating condition by comparing the pressure or flow rate detected by the pneumatic seat sensor 46 with the first and second threshold values.Furthermore, if, as a result of comparing the pressure or flow rate with the first threshold value, it is determined that the seating condition is failing due to chip jamming or the like, it sends a command to the spindle control unit 78 to clean the first seating surface ES1 and the second seating surface ES2, as described later. Upon receiving the command, the spindle control unit 78 actuates the unclamping piston 40 to connect it to the drawbar 22, unclamps the tool holder 14, and actuates the air supply source 58 to supply air to the airflow path 48 and the spindle-side flow path 50, thereby controlling the cleaning of the first seating surface ES1 and the second seating surface ES2. Furthermore, the evaluation unit 74 is also electrically connected to the tool change control unit 80. If the evaluation unit 74 determines that the tool holder 14 is properly seated on the spindle 12b, it sends a signal to the tool change control unit 80 indicating that it is properly seated. Upon receiving this signal, the tool change control unit 80 terminates the tool change operation. If, furthermore, the evaluation unit 74 determines that the tool holder 14 is not properly seated on the spindle 12b, it sends a signal to the tool change control unit 80 indicating the failure. Upon receiving this signal, the tool change control unit 80 re-seats the tool holder 14, or a newly replaced tool holder 14, onto the spindle 12b and operates the machine tool 10 to clean the seating surface by releasing air from the air supply source. The machine control 70 further comprises an operating panel 90 for the user of the machine tool 10 to operate the machine control 70 and a numerical control unit 88 for transmitting a command entered by the user via the operating panel 90 to confirm the seating status to the evaluation unit. The numerical control unit 88 controls the timing of this seating status confirmation and also executes all operating commands of the machine tool 10 using numerical information. In addition, the operating panel 90 includes a display unit 92 for visualizing the seating status evaluation result for the user. As a result, the user can easily understand the seating status of the tool holder 14. The operating mode and effects of the spindle device 12 of the machine tool 10 according to the present embodiment are explained below with reference to the flow diagram of the seat confirmation shown in Fig. 3. When the exchange of tool TL and toolholder 14 is initiated (step S10), the process proceeds to step S20, and the assessment part 74 of the seat confirmation control part 72 activates the machine tool 10 via the spindle control part 78 to initiate the attachment (insertion) of the toolholder 14 onto the spindle 12b. Next, the process proceeds to step S30, and the spindle control part 78 activates the air supply source 58 to supply air to the airflow path 48 and the spindle-side airflow path 50 to clean the first seat surface ES1 and the second seat surface ES2. Once the cleaning is complete, the process proceeds to step S40, and the assessment part 74 begins assessing the seat condition. When the seating condition assessment process begins, the process proceeds to step S50, and the assessment part 74 actuates the machine tool 10 to press the toolholder 14 onto the spindle 12b with a predetermined clamping force, i.e., attempts to fully seat it. Once this pressing is complete, the process proceeds to step S60, and the assessment part 74 actuates the release piston 40 via the spindle control part 78 to press the drawbar 22 with a seating confirmation clamping force. This results in an intermediate clamping condition. When the pull rod 22 is in the intermediate clamping state, the process proceeds to step S70, and the evaluation part 74 activates the air supply source 58 via the spindle control part 78 to supply air to the first seat surface ES1 and the second seat surface ES2, and simultaneously detects (measures) the pressure or flow rate using the pneumatic seat sensor 46. Once the pressure or flow rate has been detected by the pneumatic seat sensor 46, the process proceeds to step S80, and the evaluation part 74 compares these pressures or flow rates with the first threshold and the second threshold to evaluate the seat condition, and the process then proceeds to step S90, and the seat condition evaluation result is displayed on the display part 92. If the seating condition is judged to be failed, i.e., if chips are judged to be jammed in step S80, the process proceeds to step S100, and the judging part 74 actuates the unclamping piston 40 via the spindle control part 78 to push the drawbar 22 under high pressure. This forces the drawbar 22 into the unclamping state. Once the tool holder 14 is unclamped, the process proceeds to step S110, and the judging part 74 actuates the air supply source 58 via the spindle control part 78 to supply air for cleaning to the first seating surface ES1 and the second seating surface ES2. After cleaning, the process proceeds to step S30, and the seating condition is judged again (from step S30 to step S80).If the seating condition continues to indicate "failure" after a predetermined number of cleaning cycles, the process moves from step S110 to step S120, and the machine tool 10 issues an alarm indicating that the seating condition has "failed". If the evaluation part 74 determines in step S80 that the seating condition is satisfactory, i.e., that no chips are jammed, the process proceeds to step S130, and the evaluation part 74 reactivates the machine tool 10 to retract the unclamping piston 40 and attach the tool holder 14 to the spindle 12b with a predetermined clamping force. Once the attachment of the tool holder 14 is complete, the process proceeds to step S140, and the evaluation part 74 activates the air supply source 58 via the spindle control part 78 to stop the air supply. Furthermore, the process proceeds to step S150, and the evaluation part 74 performs the tool change operation for tool TL and tool holder 14 using the machine tool 10 via the tool change control part 80.Once the exchange process of tool TL and tool holder 14 is completed, the process moves to step S160, and the machine tool 10 begins machining. The spindle device 12 for the machine tool 10 according to the present embodiment comprises a tool clamping device 16 that can switch between at least two clamping forces, including a standard clamping force for securing the tool holder 14 when the machine tool 10 is in operation, and a predetermined seat confirmation clamping force that is lower than the standard clamping force. The spindle device 12 further comprises a pneumatic seat sensor 46 and an air supply source 58 as a seat detector for detecting the seating status between the first seating surface ES1 and the second seating surface ES2 and the tool holder 14. The spindle device 12 also includes a seat confirmation control unit 72 for adjusting the clamping force of the tool clamping device 16 to the seat confirmation clamping force in order to detect the seating status using the pneumatic seat sensor 46. In machine tool 10, small chips generated during machining can remain around the first seat ES1 and the second seat ES2. If, in this condition, an attempt is made to attach the toolholder 14 to the spindle 12b, fine chips can become trapped between the flange part 30 and the seat ES1 and / or between the shank part 32 and the second seat ES2. When these trapped chips are compressed with a predetermined clamping force, the tip-side flow path 50b and / or the branched flow path 54 are closed off, as if no chips were trapped at all. Consequently, the pneumatic seat sensor 46 can detect high pressure or a low flow rate, even though the toolholder 14 is not, strictly speaking, fully attached to the spindle 12b. Therefore, in the spindle device 12 of the machine tool 10 of the present embodiment, the pressure or flow rate that can occur in the pneumatic seat sensor 46 when chips are trapped is defined as the first threshold. With the seat confirmation clamping force, the elastic deformation is small, which can leave a gap at the tip of the tip-side flow path 50b or the branched flow path 54. Thus, if, in the intermediate clamping state, the pressure detected by the pneumatic seat sensor 46 is below the first threshold, or if the detected flow rate exceeds the first threshold, it can be determined that small chips are trapped between the flange part 30 and the seat surface ES1 and / or between the shank part 32 and the second seat surface ES2.Furthermore, the spindle device 12 can assess that the seat of the tool holder 14 is adequate if the pressure detected by the pneumatic seat sensor 46 exceeds the first threshold or if the detected flow rate is below the first threshold. Furthermore, the spindle device 12 of the machine tool 10 of the present embodiment can distinguish and assess whether, if the seat of the tool holder 14 is judged to be failed, the assessment result is based on the fact that the tool holder 14 is not properly attached to the spindle 12b because chips are trapped in the intermediate clamping state, or on the fact that the drawbar 22 has been retracted into the clamping position without the tool holder 14 being attached to the spindle 12b, which corresponds to the so-called “toolless clamping state”.More precisely, the spindle device 12 sets the pressure or flow rate that the pneumatic seat sensor 46 can detect when the toolholder 14 is not attached to the spindle 12b as the second threshold. If the seat of the toolholder 14 is judged to be failed using the first threshold, and if the pressure detected by the pneumatic seat sensor 46 is below the second threshold, or if the detected flow rate exceeds the second threshold, it can be judged that nothing is attached to the spindle 12b. Although this explanation is not described in detail in the flowchart in Fig. 3, the seat assessment in step S80 compares the detection value of the pneumatic seat sensor 46 with the second threshold to assess the tool-free clamping condition, and the result is displayed in the display section 92 in step S90.In the tool-free clamping state, steps S100, S110, and S120, which involve cleaning the first seat surface ES1 and the second seat surface ES2, are not performed. In this way, the spindle device 12 can detect the presence or absence of chips that would impede the attachment of the tool holder 14 to the spindle 12b by measuring the air pressure or flow rate in the intermediate clamping state with the pneumatic seat sensor 46, and can assess the presence or absence of the tool holder 14 and the suitability of the seat. It has been experimentally shown that detection by the pneumatic seat sensor 46 can be performed more quickly if the drawbar 22 is pulled with a predetermined clamping force in step S50 and then moved into the intermediate clamping state (step S60).Although the process of the present embodiment includes step S50, it is not limited to it, and step S50 can be omitted from the process. As described above, the spindle device 12 and the seat confirmation method for the machine tool 10 according to the present embodiment can automatically, accurately and easily confirm that a removable element such as a tool holder 14 is seated on the seat surface ES1 without jamming foreign objects. (Modification example) Although one embodiment is described in which the pull rod 22 is moved by being pushed by the unclamping piston 40 and the hydraulic power source 64, the present invention is not limited thereto, and the pull rod 22 can be moved by other means such as a servo motor and a ball screw nut. With a servo motor, the screw shaft corresponding to the unclamping piston can be driven axially by rotating the ball screw nut. Thus, the pull rod can be moved back and forth, and the clamping and unclamping states can be generated. Furthermore, the intermediate clamping state can be generated by adjusting the current value of the servo motor. In the first embodiment, the cleaning air circuit and the seat confirmation air circuit were used together, but the present invention is not limited thereto, and separate air circuits can be used. Furthermore, the present invention is not limited to detecting the presence or absence of chip jamming by the pneumatic seat sensor 46, although it is described that this detection can also be achieved by measuring the distance (gap) between the flange part of the tool holder and the seating surface in the intermediate clamping state, for example using a position sensor. (Second embodiment) The seat confirmation device according to the second embodiment is described below. Elements that are identical or corresponding to those of the first embodiment have been assigned the same reference numerals, and repeated descriptions thereof have been omitted. As shown in Fig. 4, a schematic side view of a machine tool 10 is depicted, which includes a table fixture 100 as a seat confirmation device. The table fixture 100 is configured to clamp a workpiece pallet 102, which is a removable element to which a workpiece W, representing the machining target, is attached, and includes a pallet clamping device 106 as a removal mechanism, which is attached to the top of a table 104. The pallet clamping device 106 is arranged at the four corners of the rectangular table 104 in the top view, and positioning cones 108 are arranged above each of them. Positioning bushings 110 are arranged at the four lower corners of the workpiece pallet 102 at positions corresponding to the positioning cones 108.The workpiece pallet 102 is positioned and secured on the table 104 by engaging the positioning bushings 110 with the positioning cones 108 and clamping the workpiece pallet 102 by the pallet clamping device 106. As shown in Fig. 5, a cylindrical drawbar 112 is attached to the workpiece pallet 102, penetrating the central part of the positioning bushing 110 and extending along the thickness direction (vertical direction) of the workpiece pallet 102. The drawbar 112 comprises a bolt shank section 112a extending along the vertical direction and a substantially frustoconical bolt head section 112b formed at the lower end of the bolt shank section 112a, which has a radial diameter larger than that of the bolt shank section 112a. Furthermore, the drawbar 112 comprises a bolt locking part 112c, which is formed in the connecting section between the bolt shaft part 112a and the bolt head part 112b and has a cross-sectional shape in the front view that essentially corresponds to the outer circumferential shape of a sphere 124, which will be described later, so that the surface of the sphere 124 can come into contact with it. The pallet clamping device 106 comprises a cylinder 114, which is cylindrical and extends vertically, and a collet 116, which is arranged in the central part of the cylinder 114 and has a cylindrical collet shank 116a that extends vertically. The collet shank 116a extends over the cylinder 114, and a positioning cone 108 is arranged to cover its upper surface. The positioning cone 108 and the collet 116 are open in their upper part, i.e., hollow throughout, and are arranged coaxially with the drawbar 112 on the cylinder 114, so that the drawbar 112 can be inserted from above. The inner diameter of the cylindrical collet shank 116a is slightly larger than the outer diameter of the drawbar head 112b, so that the drawbar 112 can be inserted into it.A disc-shaped piston part 116b is formed at the lower end of the collet chuck part 116a. The collet chuck section 116a includes a spherical hole section 116c at its upper end, which extends through the collet chuck section 116a such that it is circular in the side view along the radial direction of the collet chuck section 116a. A plurality of spherical hole sections 116c, having an inner diameter slightly larger than the outer diameter of the ball 124 to accommodate the ball 124, are formed along the circumferential direction of the collet chuck section 116a. To attach the workpiece pallet 102 to the pallet clamping device 106, the piston section 116b of the collet chuck 116 is first raised by the hydraulic pressure of the hydraulic source 64 described later, so that the height of the ball 124 corresponds to that of the recess section 108a formed on the inner diameter side of the positioning cone 108.When the drawbar 112 is subsequently inserted into the collet chuck part 116a, the bolt head part 112b comes into contact with the ball 124, and the ball 124 retracts into the recess part 108a. As the bolt head part 112b moves downwards beyond the ball 124, a conical hole part 110a of the positioning bushing 110 comes into contact with the positioning cone 108 and stops. Thus, the conical outer diameter surface of the positioning cone 108 serves as the seating surface ES3 of the present embodiment. A shaft element 118 is arranged on the inner circumferential side of the collet chuck part 116a, extending in a vertical direction and having a cover part 118a at its upper end. A cover spring 120 is arranged along the shaft element 118 under the cover part 118a and pre-tensions the cover part 118a relative to the collet 116 upwards. When the workpiece pallet 102 is placed on the table 100, the shaft element 118 is pressed downwards by the drawbar 112, as shown in Fig. 5. When the workpiece pallet 102 is not on the table 100, the preload force of the cover spring 120 causes the cover part 118a to rise to the position of the upper end face of the collet 116, thus preventing foreign matter such as chips from entering the interior of the collet 116. When the first solenoid valve 60 switches to clamping mode 60e, oil is supplied from the hydraulic source 64 to an upper chamber 130, the collet 116 lowers, and the ball 124 moves radially inward from the recessed part 108a, engages with the bolt head part 112b of the drawbar 112, and thereby presses the conical hole part 110a of the positioning bushing 110 against the seat surface ES3. This process is carried out simultaneously between the positioning cones 108 and the positioning bushings 110 at the four locations, and the workpiece pallet 102 is clamped to the table fixture 100. At this point, the oil is collected in a lower chamber 132 in the oil tank 66. When the first solenoid valve 60 is switched to the unclamping mode 60d, oil is supplied to the lower chamber 132, and the oil in the upper chamber 130 is collected in the oil tank 66.Thus, the collet 116 lifts, and as described above, the ball 124 retracts into the recess 108a. This unclamping process is performed simultaneously at all four points (corners), and the pallet changer (figure omitted) lifts the workpiece pallet 102 to perform the pallet change. During the pallet change process, air supplied from the air supply source 58 into a chamber 122 at the bottom of the collet 116 is released from the upper part of the collet 116 into the interior of the positioning bushing 110 through the gap inside the collet 116, thereby cleaning the inner surface of the conical hole 110a and the outer surface of the positioning cone 108.At this point, the second solenoid valve 56 is set to air discharge mode 56a, and when the pallet change operation is complete, it is switched to air intake mode 56b, the circuit is opened to atmospheric pressure and the cleaning is complete. The pallet clamping device 106 can generate an intermediate clamping state by using an electromagnetic proportional control valve 62 installed in the hydraulic circuit to reduce the hydraulic pressure to a level lower than that during clamping. Furthermore, the pallet clamping device 106 includes a pneumatic seat sensor 46 in the cleaning air circuit and can detect the air pressure or flow rate during the intermediate clamping state, similar to the first embodiment. In the table fixture 100 for the machine tool 10 of the present embodiment, the pressure or flow rate that can occur in the pneumatic seat sensor 46 when chips are jammed in the seat surface ES3 is defined as the first threshold value. If, in the intermediate jamming state, the pressure detected by the pneumatic seat sensor 46 is below the first threshold value, or if the detected flow rate exceeds the first threshold value, it can be determined that chips are jammed between the positioning bushing 110 and the seat surface ES3. Furthermore, the table fixture 100 can determine that the seat of the workpiece pallet 102 is adequate if the pressure detected by the pneumatic seat sensor 46 exceeds the first threshold value, or if the detected flow rate is below the first threshold value. As described above, the table device 100 and the seat confirmation method for the machine tool 10 according to the present embodiment can automatically, accurately and easily confirm that a removable element such as a workpiece pallet 102 is seated on the seat surface ES3 without jamming foreign objects. (Third embodiment) The seat confirmation device according to a third embodiment is described below. Elements that are identical or corresponding to those of the first and second embodiments have been assigned the same reference numerals, and repeated descriptions thereof have been omitted. As shown in Fig. 6, a schematic side view of a machine tool 10 is depicted, which includes a workpiece clamping base 150 as a seat confirmation device. The workpiece clamping base 150 comprises an angle bracket 152 for arranging (placing) a workpiece W, which is a removable element serving as the machining target, and a plurality of workpiece clamping devices 156 attached to the top of the angle bracket 152, forming a removal mechanism configured to clamp the workpiece W. Furthermore, the workpiece clamping base 150 is connected via an electromagnetic proportional control valve 62 to a hydraulic power source 64 and an oil tank 66 and includes a hydraulic cylinder 154 that actuates the workpiece clamping device 156.The workpiece clamping device 156 comprises a clamping shaft 156a, which is configured to move vertically and rotate horizontally by the hydraulic cylinder 154, and a clamping plate 156b, which is connected to the upper end of the clamping shaft 156a for clamping the workpiece W. The workpiece clamping device 156 is configured to clamp the workpiece W upwards by rotating the clamping shaft 156a and the clamping plate 156b, and to release the workpiece W by moving the clamping plate 156b away from the top of the workpiece W. Furthermore, an intermediate clamping state can be generated by adjusting the pressure exerted by the hydraulic cylinder 154 to push the clamping shaft 156a downwards with a predetermined pressure that is less than the clamping pressure.Furthermore, by lowering the clamping shaft 156a from the intermediate clamping state and pressing the clamping plate 156b against the workpiece W, a clamping state can be created in which the workpiece is clamped between the angle bracket 152 and the clamping plate 156b. The workpiece clamping base 150 comprises an airflow path 158 that extends downwards along the thickness direction of the angle bracket 152 from the seat surface ES4, where the workpiece W rests against the top of the angle bracket 152. The airflow path 158 is connected to an air supply source 58 via a switchable second solenoid valve 56. The second solenoid valve 56 is configured to be switchable between two modes. In the air discharge mode 56a, air discharged (sent) from the air supply source 58 can flow through the airflow path 158 to the seat surface ES4. This allows confirmation of whether chips are trapped in the seat surface ES4 in the intermediate clamping state, in the same manner as in the first embodiment. In the workpiece clamping base 150 for the machine tool 10 according to the present embodiment, the pressure or flow rate that may occur in the pneumatic seat sensor 46 when chips are trapped between the workpiece W and the top of the angle bracket 152 is defined as the first threshold. If, in the clamping state, the pressure detected by the pneumatic seat sensor 46 is below the first threshold, or if the detected flow rate exceeds the first threshold, it can be determined that chips are trapped between the workpiece W and the top of the angle bracket 152. Furthermore, the workpiece clamping base 150 can determine that the seating of the workpiece W is adequate if the pressure detected by the pneumatic seat sensor 46 exceeds the first threshold, or if the detected flow rate is below the first threshold. As described above, the workpiece mounting base 150 and the seat confirmation method for the machine tool 10 according to the present embodiment can automatically, accurately and easily confirm that a removable element such as a workpiece W is seated on the seat surface ES4 without jamming foreign objects. Although the embodiments of the seat confirmation devices 12, 100, 150 and the seat confirmation method for the machine tool 10 have been described above, the present invention is not limited to the embodiments described above. In addition to the foregoing, a person skilled in the art will recognize that various modifications can be made to the embodiments described above. Description of reference symbols 10 Machine tool 12 Spindle device (seat confirmation device) 14 Tool holder (removable element) 16 Tool clamping device (removal mechanism) 46 Pneumatic seat sensor (seat detector) 58 Air supply source (seat detector) 72 Seat confirmation control unit (control unit) 100 Table device (seat confirmation device) 102 Workpiece pallet (removable element) 106 Pallet clamping device (removal mechanism) 150 Workpiece mounting base (seat confirmation device) 156 Workpiece clamping device (removal mechanism) ES1 First seat surface ES2 Second seat surface ES3 Seat surface ES4 Seat surface W Workpiece (removable element) QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature JP 2001-259906

[0003] JP 2019-14017

[0003]

Claims

A seat confirmation method for a machine tool for confirming the presence or absence of close contact between a removable element and a seat surface of a removal mechanism of a machine tool, wherein the method comprises the following steps: attaching the removable element with a predetermined seat confirmation clamping force less than a standard clamping force with which the removal mechanism attaches the removable element when the machine tool is in operation; detecting a seat condition between the seat surface and the removable element when the removable element is attached with the seat confirmation clamping force; and assessing the acceptability of the results of detecting the seat condition. Seat confirmation method for a machine tool according to claim 1, wherein a combination of the removal mechanism and the removable element is one of the following combinations: a tool clamping device and a tool holder integrated in a spindle device, a pallet clamping device and a pallet integrated in a table device, and a workpiece clamping device and a workpiece arranged on a workpiece mounting base. Seat confirmation method for a machine tool according to claim 1, wherein the assessment of the acceptability of results of the detection of the seat condition when the removable element is attached with the seat confirmation clamping force comprises an assessment by comparing a detection value of a pneumatic seat sensor arranged in an airflow path leading into the seat surface of the removal mechanism with a preset first threshold value. Seat confirmation method for a machine tool according to claim 3, wherein, if a faulty seat is assessed by comparing a detection value of the pneumatic seat sensor with the preset first threshold value, the presence or absence of the removable element is further assessed by comparing a detection value of the pneumatic seat sensor with a preset second threshold value. A seat confirmation device for a machine tool for confirming the presence or absence of close contact between a removable element and a seat surface of a removal mechanism of a machine tool, the device comprising: a removal mechanism capable of switching between at least two clamping forces, including a standard clamping force with which the removal mechanism engages the removable element when the machine tool is in operation, and a predetermined seat confirmation clamping force less than the standard clamping force; a seat detector for detecting a seat condition between the seat surface and the removable element; and a control unit that adjusts a clamping force of the removal mechanism to the seat confirmation clamping force in order to detect a seat condition by means of the seat detector, and that assesses the acceptability of the results of detecting the seat condition.

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