JP5713200B2 - Clamping device and clamping method - Google Patents

Description

  The present invention relates to a clamping device and a clamping method, and more particularly to a clamping device having a hole clamp and a clamping method using the clamping device.

  For example, some clamping devices used as workpiece fixing jigs for machine tools include a hole clamp (see, for example, Patent Document 1). The hole clamp is also called a pull-in clamp, and the workpiece can be clamped by expanding the diameter of the grip inserted into the clamp hole on the bottom surface of the workpiece and causing the clamp claw of the grip to be caught in the clamp hole. Since the clamping device including the hole clamp can approach the tool to all surfaces except the bottom surface of the workpiece, the number of setup changes can be reduced and the machining can be rationalized.

JP 2011-143530 A

  The clamping device described above is in a state where the bottom surface (reference surface) of the workpiece is lifted with respect to the workpiece seating surface, in particular, the grip insertion direction (clamp hole axis line) between the lower end position of the clamp claw of the grip of the hole clamp and the bottom surface of the workpiece. When the grip diameter is increased in a state where the distance (clearance, see C in FIG. 2) is not secured, the clamp pawl bites into the opening of the clamp hole and the workpiece There is a risk that the bottom surface (product appearance surface) of the material will be damaged and so-called chipping may occur.

  Therefore, the present invention has been made in view of the above circumstances, and provides a clamping device and a clamping method capable of preventing the workpiece from being damaged due to the clamping claws of the grips of the hole clamps biting into the openings of the clamping holes. It was made as an issue to do.

In order to solve the above-mentioned problems, a clamping device according to the present invention is a hole in which a workpiece is clamped by enlarging the grip inserted into a clamping hole opened on the bottom surface of the workpiece and causing the clamping claw to bite into the clamping hole. A clamp device including a clamp, an air ejection hole opening in the workpiece seating surface, an air circuit for supplying air to the air ejection hole, and a first pressure switch for monitoring the pressure in the air circuit; A seating confirmation means for confirming seating of the workpiece on the workpiece seating surface based on an output signal of the first pressure switch, and a second pressure switch for monitoring the pressure in the air circuit. the switch includes separately, in a state where the grip is inserted into the clamping bore, the gap than the gap between the workpiece and the workpiece seating surface is predetermined It includes an inspection means for inspecting for based whether the output signal of the second pressure switch is, and a clamping operation determination means for determining whether the clamping operation of said hole clamp based on the inspection result of the inspection means It is characterized by that.

In order to solve the above-described problem, the clamping method of the present invention is a hole clamp that clamps a workpiece by expanding the diameter of a grip inserted into a clamp hole opened on the bottom surface of the workpiece and causing the clamp pawl to bite into the clamp hole. a clamp method using an insertion step of inserting the grip on the clamping hole, in a state where the grip is inserted into the clamping bore, the gap clearance between the workpiece and the workpiece seating surface is predetermined It is determined that the clamping operation is possible in an inspection step for inspecting whether or not, a clamping operation availability determination step for determining whether the hole clamp can be operated based on an inspection result of the inspection step, and a clamping operation availability determination step. A clamping operation start step for starting the clamping operation of the hole clamp, A seating confirmation step of confirming seating of the workpiece on the workpiece seating surface based on an output signal of a first pressure switch for monitoring a pressure in an air circuit for supplying air to an air ejection hole opened in the workpiece seating surface. only contains, in the inspection step, the gap between the said workpiece and the workpiece seating surface on the basis of the output signal of the separate second pressure switch and said first pressure switch monitoring the pressure in the air circuit is inspected characterized in that that.

(Aspect of the Invention)
In the following, aspects of the invention that is recognized as being capable of being claimed in the present application (hereinafter referred to as claimable invention) will be exemplified, and each exemplified aspect will be described. Here, as in the claims, each aspect is divided into paragraphs, numbers are assigned to the respective paragraphs, and the descriptions of other paragraphs are cited as necessary. This is for the purpose of facilitating the understanding of the claimable invention, and is not intended to limit the combination of the constituent elements constituting the claimable invention to those described in the following sections. In other words, the claimable invention should be construed in consideration of the description accompanying each section, the description of the embodiment, etc., and as long as the interpretation is followed, another aspect is added to the aspect of each section. Moreover, the aspect which deleted the component from the aspect of each term can also be one aspect of the claimable invention.
In the following items, each of the items (1) to ( 3 ) corresponds to each of claims 1 to 3 described in the claims.

(1) An air ejection hole opened on the workpiece seating surface, an air circuit for supplying air to the air ejection hole, and a first pressure switch for monitoring the pressure in the air circuit, Separately from the first pressure switch, a seating confirmation means for confirming the seating of the workpiece on the workpiece seating surface based on the output signal and a second pressure switch for monitoring the pressure in the air circuit, and the grip is inserted into the clamp hole Inspection means for inspecting , based on the output signal of the second pressure switch, whether the gap between the workpiece and the workpiece seating surface is equal to or less than a predetermined gap, and a hole clamp based on the inspection result of the inspection means A clamping operation availability determination means for determining whether or not the clamping operation can be performed.
According to the clamp device described in this section, the clamp pawl is clamped by configuring so that the clamp operation of the hole clamp is started only when the clamp operation determination unit determines that the clamp operation is possible. It is possible to reliably prevent damage (edge chipping) of the product external surface due to biting into the opening of the hole.
In the aspect of this section, the inspection means inspects a gap between the workpiece and the workpiece seating surface. Specifically, the inspection means is that the gap between the workpiece and the workpiece seating surface is equal to or less than a predetermined gap, that is, the grip insertion between the lower end position of the clamp claw of the grip and the workpiece bottom surface (reference surface). Make sure that the distance (clearance) in the direction is more than a predetermined distance. In other words, the inspection means confirms that the grip claw of the grip does not face the opening (work bottom surface) of the work clamp hole. The clamping operation availability determination unit determines that the hole clamp can perform the clamping operation only when it is confirmed by the inspection unit that the lower end position of the clamping claw and the bottom surface of the workpiece do not match in the grip insertion direction.
In the aspect of this section, the workpiece seating surface can be a workpiece seating surface formed on the hole clamp main body, and can be a reference member disposed on the base of the clamp device separately from the hole clamp. It is also possible to form.
Further, according to the clamp device described in this section, the inspection means is configured such that the inspection means has a gap (degree of clearance) between the workpiece and the workpiece seating surface based on an output signal of each second pressure switch provided corresponding to each hole clamp. Inspect. Here, the seating confirmation means (first pressure switch) is for detecting a clamping failure of the hole clamp. When the seating confirmation means (first pressure switch) is already provided, the second pressure switch is seated. By adding to the existing air circuit of the confirmation means, it is possible to configure the inspection means, and since only a simple modification of the existing equipment is required, it can be carried out at a low cost.

( 2 ) The clamp device according to ( 1 ), wherein the second pressure switch monitors the pressure of the second air supply path provided by bypassing the first air supply path whose pressure is monitored by the first pressure switch.
According to the clamp device described in this section, when the seating confirmation means (first pressure switch) is already provided, each second air supply path is formed by bypassing each existing first air supply path, The inspection means can be configured by monitoring the pressure of the second air supply path using the corresponding second pressure switch. In this case, the first pressure switch and the second pressure switch of the corresponding hole clamp are arranged in parallel.
The first pressure switch is for confirming the close contact between the workpiece and the workpiece seating surface, whereas the second pressure switch is for inspecting the degree of the gap between the workpiece and the workpiece seating surface. Therefore, the set pressure of the second pressure switch is set lower than the set pressure of the first pressure switch.

( 3 ) A clamping method using a hole clamp that clamps a workpiece by enlarging the grip inserted into the clamp hole opened in the bottom surface of the workpiece and causing the clamp pawl to bite into the clamp hole. An insertion step for inserting the grip, an inspection step for inspecting the gap between the workpiece and the workpiece seating surface with the grip inserted in the clamp hole, and whether or not the hole clamp can be operated based on the inspection result of the inspection step And a clamping operation start step for starting the clamping operation of the hole clamp when it is determined that the clamping operation is possible in the clamping operation availability determination step.
According to the clamping method described in this section, the clamping operation of the hole clamp is started only when it is determined that the clamping operation is possible in the clamping operation propriety determination step. It is possible to reliably prevent damage to the appearance of the product due to biting in (edge chipping).
In the aspect of this section, in the inspection step, the gap between the workpiece and the workpiece seating surface is inspected. Specifically, in the inspection step, the gap between the workpiece and the workpiece seating surface is equal to or less than a predetermined gap, that is, the grip is inserted between the lower end position of the grip claw of the grip and the workpiece bottom surface (reference surface). It is confirmed that the distance (clearance) in the direction is secured more than a predetermined distance. In other words, in the inspection step, it is confirmed that the gripping claw of the grip does not face the opening (workpiece bottom surface) of the workpiece clamping hole. Then, in the clamping operation propriety determination step, it is determined that the hole clamp can perform the clamping operation only when it is confirmed in the inspection step that the lower end position of the clamping claw and the workpiece bottom surface do not match in the grip insertion direction, Furthermore, in the clamp operation start step, the clamp operation of the hole clamp is started only when it is determined in the clamp operation availability determination step that the hole clamp can be clamped.
In the aspect of this section, the workpiece seating surface can be a workpiece seating surface formed on the hole clamp body, and a reference member disposed on the base of the clamp device separately from the hole clamp; can do.
Further, according to the clamping method described in this section, in the inspection step, the gap (degree of gap) between the workpiece and the workpiece seating surface based on the output signal of each second pressure switch provided corresponding to each hole clamp. Is inspected. Here, the first pressure switch is for detecting a clamping failure of the hole clamp. When the first pressure switch is already installed, the second pressure switch is added to the existing air circuit for inspection. A configuration for performing the steps can be achieved, and since only a simple modification of the existing equipment is required, the cost can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the clamp apparatus and clamp method which can prevent the damage of the workpiece | work by the clamp nail | claw of the grip of a hole clamp biting into the opening part of a clamp hole can be provided.

It is a perspective view of the clamp apparatus of this embodiment. It is explanatory drawing of the clamp apparatus of this embodiment, and is an axial plane sectional view of the clamp part which shows the state by which the workpiece | work was normally clamped by the hole clamp. It is a figure which shows schematic structure of the air circuit of the clamp apparatus of this embodiment. It is a time chart figure of the clamping method of this embodiment. It is a perspective view of the clamp device of other embodiments.

An embodiment of the present invention will be described with reference to the accompanying drawings.
The clamp apparatus 1 of this embodiment is used as a workpiece fixing jig attached to a machine table of a machining center, for example. As shown in FIG. 1, the clamping device 1 has a base 2 having a plate 2a. On the plate 2a, there are four hole clamps 3, four lifters 4 (for example, hydraulic cylinders) disposed in the vicinity of each hole clamp 3, and two generally disposed on one diagonal of the plate 2a. One positioning pin 5 and two guide pins 6 arranged on the other diagonal line of the plate 2a are provided.

  The hole clamp 3 has a flange portion fixed to the plate 2a by four bolts 7 and is inserted into a clamp hole 10 (see FIG. 2) of the workpiece 9 protruding upward in the center of the clamp body 8. And a workpiece seating surface 12 that is provided in the clamp body 8 and is formed in an annular shape around an axis of the clamp portion 11 (hereinafter referred to as a clamp shaft). As shown in FIG. 2, the clamp portion 11 includes a rod 13 that is arranged coaxially with respect to the clamp shaft, and a grip 14 that is provided so as to surround the rod 13.

  The rod 13 has an upper end portion 13a having an outer conical surface, and the upper end portion 13a has four tapered surfaces 15 (only two surfaces are shown in FIG. 2). ) At equal intervals (angle phase 90 °). The grip 14 is configured by dividing four grip pieces corresponding to the respective tapered surfaces 15 around the clamp axis. Further, each grip piece of the grip 14 is formed with a flat tapered surface 16 that slidably contacts the corresponding tapered surface 15. The grip 14 is always urged toward the reduced diameter side.

  The hole clamp 3 is moved downward in FIG. 2 with respect to the grip 14 when the rod 13 is pulled in an unclamped state (a state where the grip 14 is reduced in diameter). Thereby, the diameter of the grip 14 is expanded, and the clamp claws 17 formed on the outside of the grip 14 bite into the inner peripheral surface of the clamp hole 10 of the workpiece 9 as shown in FIG. As a result, the workpiece 9 is clamped by the hole clamp 3. As the hole clamp 3, a commercially available product can be used as it is. Therefore, further detailed description of the hole clamp 3 is omitted for the purpose of simplifying the description of the specification.

  As shown in FIG. 3, the clamping device 1 includes an air ejection hole 18 that opens on the workpiece seating surface 12 of the hole clamp 3, and an air circuit that supplies compressed air supplied from the equipment side to the air ejection hole 18. 19 and a first pressure switch 21 that monitors the pressure in the first air supply path 20 that communicates with the air ejection hole 18. As the seating confirmation means, the existing one in the clamping device 1 is used as it is, and the first pressure switch 21 blows air between the workpiece seating surface 12 and the bottom surface 9a of the workpiece 9 (hereinafter referred to as the workpiece bottom surface 9a). When it is detected that the pressure in the first air supply path 20 when air is ejected from the hole 18 has reached the set pressure P1, a detection signal is output. Then, the control means (seat confirmation means) has reached the set pressure P <b> 1 based on the output signal of each first pressure switch 21 provided corresponding to each hole clamp 3. By recognizing this, it can be confirmed that the workpiece bottom surface 9a (reference surface) is in close contact with the workpiece seating surface 12 of the hole clamp 3.

  Further, the clamp device 1 is configured such that the gap between the workpiece bottom surface 9a (reference surface) and the workpiece seating surface 12 (the extent of the gap, in FIG. 3) in a state where the grip 14 of the hole clamp 3 is inserted into the clamp hole 10 of the workpiece 9. L), that is, an inspection means for inspecting the distance between the workpiece bottom surface 9a and the workpiece seating surface 12 in the direction along the clamp axis (the vertical direction in FIGS. 2 and 3, hereinafter referred to as the grip insertion direction). The inspection means monitors the pressure in each second air supply path 22 and each second air supply path 22 provided by bypassing each first air supply path 20 corresponding to each hole clamp 3. Pressure switch 23. As shown in FIG. 3, the second pressure switch 23 is arranged in parallel to the first pressure switch 21, and air is ejected from the air ejection hole 18 between the workpiece seating surface 12 and the workpiece bottom surface 9a. When it is detected that the pressure in the second air supply path 22 has reached the set pressure P2, the detection signal is output.

  Further, the clamping device 1 includes a clamping operation availability determination unit that determines whether the clamping operation of the hole clamp 3 is possible based on the inspection result of the inspection unit. Specifically, the clamping operation availability determination means is incorporated in the control means described above, and the pressure in the second air supply path 22 has reached the set pressure P2 based on the output signal of the second pressure switch 23. , It is determined that the gap L between the workpiece bottom surface 9a (reference plane) and the workpiece seating surface 12 is equal to or less than a predetermined gap L0 (L0 ≧ L).

  That is, the clamping operation propriety judging means secures a clearance (C in FIG. 2) between the lower end position of the clamping claw 17 and the position of the workpiece bottom surface 9a based on the output signal of the second pressure switch 23 to a predetermined clearance C0 or more. In other words, in other words, it is determined that the hole clamp 3 can perform the clamping operation only when it is confirmed that the lower end position of the clamp claw 17 and the position of the work bottom surface 9a do not coincide with each other. To do. The clamp device 1 is configured such that the clamp operation of each hole clamp 3 is started only when it is determined by the clamp operation availability determination means that all the hole clamps 3 can be clamped.

Next, the operation (clamping method) of the present embodiment will be described based on the time chart shown in FIG.
In the initial state of the clamping device 1, that is, before the clamping device 1 receives the workpiece 9 (T0 in FIG. 4), it is confirmed that each lifter 4 is positioned at the rising end. The rising end of each lifter 4 can be confirmed by the output signal of the cylinder switch attached to each lifter 4. In the initial state T0, air is released into the atmosphere from the air ejection holes 18 formed on the workpiece seating surfaces 12 of the respective hole clamps 3, in other words, there is a sufficient gap above the workpiece seating surfaces 12. The pressure in the first air supply path 20 is required to be a certain level or less.

  The control means determines that all of the first pressure switches 21 (seat confirmation means) and each of the second pressure switches 23 (in the initial state T0, there is nothing on the workpiece seating surface 12). This can be confirmed by the fact that the clamping operation availability determination means) is OFF. Then, the control means (clamp operation availability determination means) determines that the clamp operation of each hole clamp 3 is impossible by confirming that at least one second pressure switch 23 is OFF. Since the set pressure P2 of the second pressure switch 23 is set lower than the set pressure P1 of the first pressure switch 21, normally, when the second pressure switch 23 is in the OFF state, the first pressure switch 21 Is also in an OFF state.

  When it is confirmed that the lifted ends of the lifters 4 and all the first pressure switches 21 are OFF (clamping is not possible), the workpiece 9 is loaded into the clamping device 1 in the initial state T0 by the loading device (for example, a robot hand). . When the work 9 is carried in, each guide pin 6 of the clamping device 1 is inserted into each corresponding guide hole of the work 9. Thereby, the work 9 is placed on each lifter 4 in a state of being roughly positioned with respect to the clamping device 1. In this state, the top portions of the clamp portions 11 of the respective hole clamps 3 (top portions of the rods 13) face the corresponding clamp holes 10 of the workpiece 9, and the top portions of the positioning pins 5 face the positioning holes of the corresponding workpiece 9. It will be.

(Insert step)
Next, at time T1 in FIG. 4, each lifter 4 is lowered and the work 9 is lowered. Thereby, each positioning pin 5 corresponding to each positioning hole of the workpiece 9 is fitted, and the workpiece 9 is positioned with a positioning accuracy required for the clamping device 1. At the same time, the clamp portions 11 of the corresponding hole clamps 3 are inserted into the clamp holes 10 of the workpiece 9.

(Inspection step)
By lowering each lifter 4, a gap L (see FIG. 3) is formed between the workpiece seating surface 12 and the workpiece bottom surface 9a (reference surface) of each hole clamp 3. Thereby, the back pressure of the air ejected from each air ejection hole 18 rises, and the pressure in each 2nd air supply path 22 rises with the raise of this back pressure. When the gap L is equal to or smaller than the predetermined gap L0 (L0 ≧ L), the second pressure switch 23 is turned on when the pressure in the second air supply path 22 reaches the set pressure P2. . In other words, when the second pressure switch 23 is turned on, it is confirmed that the gap L between the workpiece seating surface 12 and the workpiece bottom surface 9a is equal to or less than the predetermined gap L0.

  Thus, in the inspection step, when the second pressure switch 23 is turned on, as shown in FIG. 2, the grip insertion direction between the lower end position of the clamp claw 17 of the grip 14 and the work bottom 9a. The clearance C in the vertical direction in FIG. 2 is secured at a predetermined distance C0 or more, that is, the clamp claw 17 of the grip 14 faces the opening (work bottom surface 9a) of the clamp hole 10 of the work 9. It is confirmed that it is not.

(Clamping operation determination step)
Then, the control means (clamp action availability determination means) corresponds to the lower end position of the clamp claw 17 of each grip 14 and the work 9 by the output signal of each second pressure switch 23 provided corresponding to each hole clamp 3. By recognizing that the opening (work bottom surface 9a) of each clamp hole 10 does not coincide with the grip insertion direction, it is determined that all the hole clamps 3 can perform the clamping operation. When the output signal (ON state) of at least one second pressure switch 23 is not obtained within the time set by the timer, the control means cannot perform the clamping operation of the hole clamp 3, that is, the workpiece 9 It is determined that there is a set mistake.

(Clamping operation start step)
Then, the control means confirms that each lifter 4 is positioned at the descending end at time T2 in FIG. 4, and confirms that each hole clamp 3 can be clamped. At this point, each hole clamp 3 is operated. That is, the rod 13 of each clamp part 11 inserted in each clamp hole 10 of the workpiece 9 is lowered to increase the diameter of the grip 14 of each clamp part 11. As a result, as shown in FIG. 2, the clamp claw 17 of the grip 14 bites into the inner wall of the clamp hole 10, and the workpiece 9 is pulled and clamped by the hole clamps 3.

(Sitting confirmation step)
Then, the control means confirms the clamp end at time T4 in FIG. 4, that is, if it is confirmed by a cylinder switch or the like that the rod 13 of each hole clamp 3 has been stroked by a predetermined distance, FIG. At time T5 in FIG. 4, based on the output signal of the first pressure switch 21 (seat confirmation means), it is confirmed whether or not the work bottom surface 9a (reference surface) is in close contact with the work seating surfaces 12 of all the hole clamps 3. Is done. When it is confirmed that all the first pressure switches 21 are in the ON state, that is, the work bottom surface 9a (reference surface) is in close contact with the work seating surfaces 12 of all the hole clamps 3, the control device Recognizes that the workpiece 9 has been clamped normally.

  Then, when recognizing that the workpiece 9 has been clamped normally, the control device outputs a signal notifying that the clamping has been completed at time T6 in FIG. 4 and ends all the processes. If the output signal (ON state) of at least one first pressure switch 21 (seat confirmation means) cannot be obtained at time T6 in FIG. It is determined that

This embodiment has the following effects.
According to the present embodiment, after the clamp portions 11 of the respective hole clamps 3 corresponding to the respective clamp holes 10 of the workpiece 9 are inserted, it is determined whether or not each hole clamp 3 can be clamped. When it is determined that the clamping operation is possible, that is, when it is confirmed that the gap L between each workpiece seating surface 12 and the workpiece bottom surface 9a is equal to or less than the predetermined gap L0, in other words, 11 when the clearance C in the grip insertion direction between the lower end position of the clamp claw 17 of the grip 14 and the work bottom surface 9a is secured at a predetermined distance C0 or more, that is, the clamp of the grip 14 of each clamp portion 11 When it is confirmed that the claw 17 does not face the opening (workpiece bottom surface 9a) of the clamp hole 10 of the workpiece 9, Since the lip 14 is expanded and the workpiece 9 is clamped, it is possible to reliably prevent the workpiece from being damaged (edge missing) due to the clamping claw 17 of the grip 14 of the hole clamp 3 biting into the opening of the clamp hole 10. Can do.

  In addition, the determination of whether or not the clamping operation is possible is performed based on the inspection result of the inspection unit configured using the existing seating confirmation unit, so that an increase in equipment cost can be suppressed. That is, the inspection means bypasses each first air supply path 20 of the seating confirmation means to form a second air supply path 22 and each second pressure switch corresponding to the pressure in each second air supply path 22. Therefore, it is possible to carry out by simply modifying the existing equipment.

In addition, embodiment is not limited above, For example, it can comprise as follows.
In the present embodiment, the clamp device 1 is configured using the hole clamp 3 on which the workpiece seating surface 12 is formed. However, as shown in FIG. 5, the hole clamp 33 on which the workpiece seating surface 12 is not formed is used. Thus, the clamping device 31 can be configured. In this case, the reference member 34 provided with the workpiece seating surface 12 (the height reference of the workpiece 9) with the air ejection holes 18 opened is provided in the vicinity of each hole clamp 33, as is implemented in a clamping device using a link clamp. The clamping device 31 may be configured by disposing it. In this case, the first air supply path 20 (see FIG. 3) is provided corresponding to the air ejection hole 18 of each reference member 34, and the second air supply path 23 bypasses each first air supply path 20. It is constituted by. In FIG. 5, components corresponding to those in FIG.

DESCRIPTION OF SYMBOLS 1 Clamping device, 3 Hole clamp, 9 Workpiece, 9a Workpiece bottom face, 10 Clamp hole, 12 Workpiece seating surface, 14 Grip, 17 Clamp claw, 18 Air ejection hole, 19 Air circuit, 20 1st air supply path, 21 1st Pressure switch, 22 second air supply path, 23 second pressure switch

Claims (3)

A clamp device comprising a hole clamp in which a workpiece is clamped by enlarging the grip inserted into a clamp hole opened in the bottom surface of the workpiece and causing the clamp pawl to bite into the clamp hole,
The first pressure switch, comprising: an air ejection hole opening in the workpiece seating surface; an air circuit for supplying air to the air ejection hole; and a first pressure switch for monitoring the pressure in the air circuit. Seating confirmation means for confirming the seating of the workpiece on the workpiece seating surface based on the output signal of
A second pressure switch for monitoring the pressure in the air circuit is provided separately from the first pressure switch, and the gap between the workpiece and the workpiece seating surface is previously set in a state where the grip is inserted into the clamp hole. Inspection means for inspecting whether the gap is equal to or less than a predetermined gap based on an output signal of the second pressure switch ;
A clamping operation availability determination unit that determines whether or not the clamping operation of the hole clamp is based on an inspection result of the inspection unit;
A clamping device comprising: The second pressure switch, according to claim 1, characterized in that for monitoring the pressure of the second air supply passage that pressure by the first pressure switch is provided to bypass the first air supply passage to be monitored Clamping device. It is a clamping method using a hole clamp that clamps a work by expanding the diameter of a grip inserted into a clamp hole opened on the bottom surface of the work and allowing a clamp claw to bite into the clamp hole,
An insertion step of inserting the grip into the clamp hole;
An inspection step for inspecting whether a gap between the workpiece and the workpiece seating surface is equal to or less than a predetermined gap in a state where the grip is inserted into the clamp hole;
A clamping operation propriety determination step for determining whether or not the hole clamp can be operated based on an inspection result of the inspection step;
A clamp operation start step for starting the clamp operation of the hole clamp when it is determined that the clamp operation is possible in the clamp operation availability determination step;
A seating confirmation step of confirming seating of the workpiece on the workpiece seating surface based on an output signal of a first pressure switch for monitoring a pressure in an air circuit for supplying air to an air ejection hole opened in the workpiece seating surface. only including,
In the inspection step, a gap between the workpiece and the workpiece seating surface is inspected based on an output signal of a second pressure switch separate from the first pressure switch for monitoring the pressure in the air circuit. Clamping method.

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