Collection mechanism and collection method for collecting machined parts

Abstract

To provide a collection mechanism for collecting a machined portion (102) cut from a material by rotary machining. The collection mechanism includes a clamping unit (38) and a controller. The clamping unit (38) has a pair of arms (40) and clamps the machined portion (102) using the pair of arms (40). The clamping unit (38) is capable of switching between a clamping state and a standby state. In the clamping state, the pair of arms (40) are closed to contact the circumferential surface of the machined portion (102), thereby clamping the machined portion (102). In the standby state, the pair of arms are opened (40) so as to maintain proximity to the circumferential surface of the machined portion (102) with a certain gap between the arms (40) and the circumferential surface of the machined portion (102). The controller controls the drive of the clamping unit (38). The controller monitors whether the cutting of the machined part (102) is completed to keep the clamping unit (38) in a standby state before the cutting is completed, and switches the clamping unit (38) from the standby state to the clamping state when the cutting is completed.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Japanese Patent Application No. 2018-167090, filed on September 6, 2018, the entire content of which including specification, claims, drawings, and abstract are incorporated herein by reference. Technical Field

[0003] The present application discloses a collecting mechanism and a collecting method for collecting machined parts severed from a material in turning machining. Background Art

[0004] Generally, cutting machining (separation machining) of cutting off a machined portion from a material by rotary machining is known. In cutting machining, a rotatable clamping material is rotated and a tool is pressed against the material, thereby cutting off a portion of the material or the machined portion.

[0005] Here, although the material is usually rotatably held by the shaft, the portion cut off from the material (the machined portion) will fall due to the action of gravity when the cutting machine process is completed. The fallen machined portion may hit the machine tool, causing it to be dented or otherwise damaged.

[0006] In order to solve the above problems, conventional technology has proposed a technology for collecting machined parts and preventing the cut machined parts from being damaged. For example, Patent Document 1 and Patent Document 2 disclose a clamping mechanism that utilizes a pair of prongs to clamp the machined parts for collection. Since each prong has a bearing on its inner surface that can withstand the rotation of the material, the pair of prongs can be used to clamp the machined parts by clamping the machined parts even when cutting the machined parts. With this structure, damage to the cut machined parts caused by the falling of the machined parts can be effectively prevented, so that the quality of the machined parts can be improved to a certain extent.

[0007] Reference List

[0008] Patent Literature

[0009] Patent document 1: JP S4950880 U

[0010] Patent Document 2: JP 2002-233986 A

[0011] However, conventional clamping mechanisms have lower positioning accuracy than machine tools. This results in a mismatch between the material's rotational center position and the position of the clamping mechanism, which in some cases can cause the material to shift slightly when clamped by the clamping mechanism. As mentioned above, if the material rotates during this shift, it may vibrate, which can impair the quality of the cut section of the machined part.

[0012] In order to solve the above-mentioned problems, the present invention discloses a collecting mechanism and a collecting method for improving the quality of a machined portion cut off from a material by rotary machining. Summary of the Invention

[0013] According to one aspect of the present invention, there is provided a collecting mechanism for collecting machined parts cut off from materials by rotary machining, the collecting mechanism comprising: a clamping unit having a pair of arms, the clamping unit clamping the machined part by means of the pair of arms, the clamping unit being switchable between a clamping state and a standby state; in the clamping state, the pair of arms are closed so as to contact the circumferential surface of the machined part, thereby clamping the machined part; in the standby state, the pair of arms are opened so as to maintain proximity to the circumferential surface of the machined part with a certain gap between the pair of arms and the circumferential surface of the machined part; and a controller for controlling the drive of the clamping unit; wherein the controller monitors whether the cutting of the machined part has been completed, so as to maintain the clamping unit in the standby state before the cutting is completed, and switches the clamping unit from the standby state to the clamping state when the cutting is completed.

[0014] Because this structure keeps the clamping unit spaced apart from the material during cutting, it does not exert any additional force on the material. This prevents material deflection and vibration, improving the quality of the cut section of the machined part. When cutting is complete, the clamping unit holds the machined part in place, effectively preventing damage to the machined part from falling.

[0015] In one embodiment, each arm in the pair of arms may include a main arm body and one or more rollers mounted on the main arm body, wherein the rollers are capable of rolling on the circumferential surface of the machined portion.

[0016] The roller is provided to prevent friction between the arm and the machined part which keeps rotating due to inertia after being cut off, thereby further improving the quality of the machined part.

[0017] In one embodiment, the clamping unit may have an opening / closing actuator for causing the pair of arms to move linearly forward and backward in the width direction of the clamping unit; and each of the paired arms may have two rollers linearly arranged on the arm in the height direction of the clamping unit.

[0018] With this structure, the machined part is clamped by a total of four rollers so that the center of the machined part matches the center of the circumscribed circle of the four rollers. With this structure, since the position of the center of the circumscribed circle relative to the reference point at the base of the clamping unit remains unchanged regardless of the diameter of the machined part (regardless of the opening amount of the arm), simple control of the position of the clamping unit is achieved.

[0019] In one embodiment, at least one surface of the main arm body, the surface opposite to the other main arm body, is arcuate or curved so as to be convex in a direction away from the other main arm body.

[0020] This structure can prevent interference between the main arm body and the machined part.

[0021] In addition, the collecting mechanism may also include: a cutting determination sensor, which is used to measure a physical quantity that depends on at least one of the rotational resistance of the axis that rotatably clamps the material and the cutting resistance in cutting the material, and the controller may determine the time when the cutting of the machined part is completed based on the measurement value of the cutting determination sensor.

[0022] This structure can accurately determine when the cutting is completed.

[0023] In one embodiment, the cutting determination sensor may include a sensor that measures any one of the following: the torque of the rotary motor of the shaft, the current of the rotary motor, the torque of the mobile motor of the tool post that clamps the tool, the current of the mobile motor, and the twist of the tool; and the controller may determine the time when the differential value of the measured value of the cutting determination sensor becomes equal to or less than a threshold value of a predetermined negative value as the time when the cutting of the machined part is completed.

[0024] This structure can more accurately determine the time when the cutting is completed.

[0025] In addition, the collecting mechanism may further include a multi-degree-of-freedom robot installed in a machine room, and the gripping unit may be attached to the robot as an end effector.

[0026] This structure can increase the freedom of movement of the clamping unit and improve the versatility of the collecting mechanism.

[0027] In one embodiment, the controller may control the clamping unit such that the clamping unit collects remaining material remaining after the machined portion is cut off.

[0028] With this structure, since the remaining materials do not fall into the machine chamber, it is possible to prevent the machine chamber from being damaged by the remaining materials.

[0029] According to another aspect of the present disclosure, there is provided a method for collecting a machined part severed from a material by rotary machining, the method comprising: monitoring whether the severing of the machined part is completed during cutting machining of the machined part; and driving a clamping unit based on the monitoring result so that the clamping unit having a pair of arms opens before the severing is completed, so that the pair of arms remain close to the circumferential surface of the machined part with a certain gap between the arms and the circumferential surface of the machined part, and so that the clamping unit closes when the severing is completed, so that the pair of arms contacts the circumferential surface of the machined part, thereby clamping the machined part.

[0030] With this structure, since the clamping unit is spaced apart from the material during cutting machining, it does not exert additional force on the material. Consequently, material deflection and vibration are prevented, which improves the quality of the cut section of the machined part. Furthermore, when cutting machining is completed, the clamping unit holds the machined part, effectively preventing it from falling and causing damage.

[0031] According to the collecting mechanism and collecting method disclosed in this specification, the quality of the machined portion severed from the material in cutting machining can be further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] One or more embodiments of the present disclosure will be described based on the following drawings, in which:

[0033] Figure 1 is a schematic side view of a machine tool having a built-in collection mechanism;

[0034] Figure 2 is a schematic front view of the machine tool;

[0035] Figure 3 Shows the status of the cutting machine processing;

[0036] Figure 4 The clamping unit is shown in a standby state;

[0037] Figure 5 shows the clamping unit in a clamping state;

[0038] Figure 6An example of another clamping unit is shown;

[0039] Figure 7 is a block diagram showing the electrical structure of the units involved in determining when cutting is complete;

[0040] Figure 8 Graphs showing changes in a measured value of a cutting determination sensor, a differential value of the measured value, and a minimum amount c of a gap;

[0041] Figure 9 is a flow chart for cutting and collecting the machined portion 102.

[0042] Explanation of Reference Symbols

[0043] 10: Machine tool, 12: Cover, 14: Door, 16: Machine room, 18: Axis, 20: Tool holder, 22: Turret, 24: Tail stock, 26: Internal robot, 28: Controller, 30: Chuck, 36: End effector, 38: Clamping unit, 40: Arm, 42: Main arm body, 44: Roller, 46: Cutting determination sensor, 48: Open / close actuator, 100: Material, 102: Machined part, 110: Tool. DETAILED DESCRIPTION

[0044] The structure of a collecting mechanism for collecting machined parts will now be described with reference to the accompanying drawings. Figure 1 is a schematic side view of a machine tool 10 having a built-in collection mechanism. Figure 2 is a schematic front view of machine tool 10. Hereinafter, the direction parallel to the rotational axis of shaft 18 is defined as the Z-axis, the direction parallel to the movement direction of the Z-axis orthogonal to tool holder 20 is defined as the X-axis, and the direction orthogonal to the X-axis and Z-axis is defined as the Y-axis. With respect to the Z-axis, the direction from shaft 18 toward tool holder 20 is defined as the positive direction. With respect to the X-axis, the direction from shaft 18 toward tool holder 20 is defined as the positive direction. With respect to the Y-axis, the direction upward from shaft 18 is defined as the positive direction.

[0045] The machine tool 10 is a machine tool that uses a tool 110 placed on the rotating material to rotate the material. Figure 1 and Figure 2 A lathe (not shown) is used for machining, wherein the tool 110 is held by a tool holder 20. More specifically, the machine tool 10 is a rotation center controlled by an NC and has a turret 22 that holds a plurality of tools 110. Rotary machining using this lathe includes cutting machining (separation machining) for cutting a material into pieces of predetermined length. During cutting machining, it is necessary to collect the pieces (machined parts) severed from the material. This specification discloses a collection mechanism that collects the machined parts 102 severed by cutting machining.

[0046] The machine tool 10 has a machine chamber 16, the circumference of which is covered by a cover 12. The machine chamber 16 has a large opening on its front surface. This opening is opened and closed by a door 14. An operator accesses the corresponding units in the machine chamber 16 through this opening. During machining, the door 14 provided to the opening remains closed to ensure safety and a suitable environment.

[0047] The machine tool 10 includes a shaft assembly, a tool holder 20, and a tailstock 24. The shaft assembly rotatably clamps one end of a material. The tool holder 20 clamps a tool 110. The tailstock 24 supports the other end of the material. The shaft assembly includes a headstock (not shown) and a shaft 18 mounted on the headstock. For example, the headstock has a built-in rotary motor. The shaft 18 has a chuck 30 or collet that removably clamps the material, allowing the material to be clamped to be freely replaced. The shaft 18 and the chuck 30 rotate about a rotation axis extending in the horizontal direction (Z-axis direction).

[0048] The tail stock 24 is provided so as to be opposed to the shaft 18 in the Z-axis direction, and supports the other end of the material clamped by the shaft 18. The tail stock 24 can move in the Z-axis direction so as to approach or move away from the material.

[0049] The tool holder 20 holds a tool (e.g., a rotary tool called a cutting tool) 110 and serves as a clamping device. The tool holder 20 can move in a direction parallel to the Z axis (i.e., the axis of the material). The tool holder 20 can also advance and retreat in a direction parallel to the X axis (i.e., the diameter direction of the material). Figure 1 It is apparent that the X-axis is tilted upward relative to the horizontal because it is farther from the opening of the machine chamber 16 in the opposite direction of the opening. The tool holder 20 has a turret 22 at one end. The turret 22 can hold a plurality of tools 110. When viewed in the Z-axis direction, the turret 22 is polygonal in shape and can rotate about an axis parallel to the Z-axis. The turret 22 has one or more tools 110 removably mounted on its circumferential surface. Rotating the turret 22 allows for replacement of the tool 110 to be used in machining.

[0050] The tool 110 clamped on the turret 22 is moved in a direction parallel to the Z axis by moving the tool holder 20 in a direction parallel to the Z axis, and is moved in a direction parallel to the X axis by moving the tool holder 20 in a direction parallel to the X axis. For example, the amount of material bitten by the tool 110 can be changed by moving the tool holder 20 in a direction parallel to the X axis.

[0051] An internal robot 26 is installed inside the machine room 16. The internal robot 26 serves as a part of the collecting mechanism. Specifically, the internal robot 26 is a multi-degree-of-freedom robot installed in the machine room 16, and is a multi-joint robot having a plurality of robot arms connected via joints. Although in the present embodiment, the internal robot 26 is set on the floor surface of the machine room 16, if the internal robot 26 can clamp the machined part using the clamping unit 38 described later, the installation position and structure of the internal robot 26 can be changed at will. For example, the internal robot 26 can be set on, for example, the wall surface of the machine room 16 or on the shaft 18. Alternatively, the internal robot 26 can be installed on a component that moves in the machine room 16 (for example, the tailstock 24). This structure can ensure a wider area in which the internal robot 26 can move.

[0052] The internal robot 26 has a gripping unit 38, which is a type of end effector 36. The gripping unit 38 grips a material (including a machined part) by gripping the material, and has a pair of arms 40 that can be opened and closed. Although in the illustrated example, only one gripping unit 38 is attached to the tip of the internal robot 26, the gripping unit 38 may be attached to different positions, or two or more gripping units 38 may be attached when necessary. The end effector 36 attached to the internal robot 26 may be replaceable. For example, when there is no need to collect the machined part, an end effector 36 (e.g., a sensor) other than the gripping unit 38 may be attached to the internal robot 26. The specific structure of the gripping unit 38 will be described later.

[0053] In response to operator commands, the controller 28 controls the driving of the respective units of the machine tool 10. For example, the controller 28 includes a CPU for various operations and a memory for storing various control programs and control parameters. The controller 28 has a communication function and can transmit and receive various data related to other devices, such as NC program data. The controller 28 may include, for example, a digital controller for arbitrarily calculating the positions of the tool 110 and the material. The controller 28 may be a single device or a combination of two or more operating devices.

[0054] The controller 28 controls the movement of the spindle 18, the tool holder 20, and the tailstock 24, for example, during rotational machining relative to a material using the tool 110. The controller 28 in this embodiment also serves as a controller for a collection mechanism for collecting machined parts, and controls the driving of the internal robot 26 and the gripper unit 38 when necessary. Collecting machined parts will now be described in detail.

[0055] Figure 3 Schematic diagram showing a state where separation machining is performed. Figure 4 and Figure 5Shown in Figure 3 The machined portion 102 and the clamping unit 38 are viewed in the Z direction. Figure 4 Concerning the state of the machined part before it is cut off; Figure 5 Concerning the state of the machined part after it has been cut off. Figure 3 and Figure 4 The arrow G in FIG. 1 indicates a vertically downward direction.

[0056] like Figure 3 As shown, during cutting machining, the material 100 is clamped by the shaft 18 via the chuck 30. The shaft 18 rotates the material 100 at a predetermined rotation per minute. Simultaneously, the tool holder 20 advances the tool 110 for use in cutting machining in the diameter direction of the material 100 while pressing the tool 110 against the circumferential surface of the material 100, thereby gradually cutting the material 100. As the tool 110 eventually reaches the center of the material 100, a portion of the material 100 closer to the tip of the material 100 than the tool 110 is cut off as the machined portion 102.

[0057] In the above, if the clamping unit 38 is not provided, upon completion of the cutting of the machined portion 102, the machined portion 102 will fall to the floor surface of the machine room 16 due to gravity. In some cases, the machined portion 102 may be dented or otherwise damaged due to the impact of the fall or friction with other components.

[0058] To prevent such damage, a technique has been proposed for pre-clamping the machined portion 102 with a pair of arms so that the machined portion 102 does not fall after being cut. According to this technique, since the arms have bearings that withstand the rotation of the material 100, the machined portion 102 can be clamped by the pair of arms while the cutting process is in progress (i.e., while the machined portion 102 is still rotating). When the machined portion 102 is clamped by the pair of arms, the machined portion 102 does not fall after being cut from the material 100. This effectively prevents damage to the machined portion 102.

[0059] However, it should be noted that the positioning of the clamping unit 38 is generally less accurate than that of the machine tool 10. This lower accuracy may result in a positional mismatch between the center of rotation of the material 100 and the position of the clamping unit 38. Consequently, in some cases, the material 100 may shift slightly when clamped by the clamping unit 38. If the material rotates while shifted, the material may vibrate, which may impair the quality of the cut section of the machined portion 102.

[0060] To solve the above problem, in this embodiment, Figure 4As shown, before the machined portion 102 is cut off, that is, when the machined portion 102 is still connected to the material 100, the clamping unit 38 is opened to be in a standby state, in which the arm 40 of the clamping unit 38 is held close to the circumferential surface of the machined portion 102 with a certain gap between the arm 40 and the circumferential surface of the machined portion 102. Then, as shown in FIG. Figure 5 As shown, when the cutting is completed, the clamping unit 38 is closed to be in a clamping state in which the arm 40 contacts the circumferential surface of the machined portion 102. In order to close and open the clamping unit 38, as described above, the controller 28 continuously monitors whether the cutting machining associated with the machined portion 102 has been completed. When it is determined that the cutting machining associated with the machined portion 102 is completed, the controller 28 switches the clamping unit 38 from the standby state (e.g., Figure 4 Switch to the clamping state (as shown) Figure 5 shown).

[0061] With this structure, since the clamping unit 38 does not apply additional force to the material 100 during cutting machining, the deviation and vibration of the material 100 can be effectively prevented, which can further improve the quality of the cut section of the machined portion 102. In addition, since the machined portion 102 is clamped by the clamping unit 38 when cutting is completed, damage to the machined portion 102 due to falling of the machined portion 102 can be effectively prevented.

[0062] The gripping unit 38 for collecting such machined parts 102 will now be described in detail. Figure 4 and Figure 5 As shown, the clamping unit 38 in this embodiment includes two arms 40, which are arranged in the width direction (in the direction with the printing Figure 4 and Figure 5 The two arms 40 are arranged in a mirror image relative to the center line of the clamping unit 38 in the up-down direction on the paper. The two arms 40 can move in the direction in which the two arms 40 approach and move away from each other. In other words, the two arms 40 can advance and retreat in the width direction of the clamping unit 38.

[0063] Inside the clamping unit 38, an open / close actuator (not shown) for opening and closing the two arms 40 is installed. For example, the open / close actuator may include at least one of an electric motor, a hydraulic piston, a pneumatic piston, and an electromagnetic cylinder. The movement through the actuator is transmitted to the arm 40 directly or through various transmission mechanisms. The transmission mechanism may include, for example, a screw, a gear, or a cam. The movement to be transmitted to the two arms 40 may have a mirror relationship. In the present embodiment, as actuated by the open / close actuator 48, each arm 40 can move linearly in the width direction of the clamping unit 38. However, it goes without saying that the two arms 40 can be moved in any manner other than linearly. For example, as Figure 6 As shown, each of the two arms 40 can be swung about the rotation axis R with its root as the center.

[0064] Each arm 40 includes a main arm body 42 and two rollers 44 mounted on the main arm body 42. Each roller 44 can be wound around the thickness direction of the clamping unit 38 (the thickness direction of the clamping unit 38). Figure 4 and Figure 5 The machined portion 102 is rotated about an axis extending in a direction perpendicular to the paper surface. In clamping the machined portion 102 by the clamping unit 38, the clamping unit 38 is arranged so that the rotation axis of the roller 44 is parallel to the central axis of the machined portion 102. With this arrangement, when the roller 44 protrudes from the width of the main arm body 42, the machined portion 102 is clamped by a total of four rollers 44 mounted on the two corresponding arms 40. Since the rollers 44 that clamp the machined portion 102 are rollable on the circumferential surface of the machined portion 102, friction between the clamping unit 38 and the machined portion 102 can be reduced.

[0065] In this embodiment, the two rollers 44 on one main arm body 42 are arranged in the height direction of the clamping unit 38 (in the actual printing direction). Figure 4 and Figure 5The clamping unit 38 is linearly arranged in the right-left direction on the paper. This structure can simplify the calculation process of the target position of the clamping unit 38. That is, in order for the clamping unit 38 to clamp the machined part 102, the clamping unit 38 should be positioned so that the center of the circumscribed circle of the four rollers 44 coincides with the center of the machined part 102. If the center position of the circumscribed circle relative to the reference point P varies depending on the distance between the two arms 40 in the open state (that is, the diameter of the machined part 102 to be clamped), this arrangement requires calculation of the center position of the circumscribed circle relative to the reference point P at the root of the clamping unit 38 (or the tip of the internal robot 26). This makes the calculation process complicated. In contrast, in a structure in which the two rollers 44 are linearly arranged in the height direction of the clamping unit 38 and a pair of rollers 44 advance and retreat linearly in the width direction of the clamping unit 38, the straight line connecting the two rollers 44 on one arm 40 is always parallel to the straight line connecting the two rollers 44 on the other arm 40. In this case, if the distance between the two arms 40 in the open state (and therefore, the diameter of the machined portion 102) should change, the center positions of the circumscribed circles of the four rollers 44 relative to the reference point P remain constant. Therefore, it is unnecessary to calculate the center positions of the circumscribed circles relative to the reference point P, which can simplify the calculation process.

[0066] Note that at least one surface of the main arm body 42 (the surface opposite to the other main arm body 42) is desirably arcuate or curved so as to be convex in a direction away from the other main arm body 42. In this embodiment, each main arm body 42 has a substantially dogleg shape so that the opposing main arm bodies 42 are convex in a direction away from each other. Figure 5 As shown, this structure makes it impossible for the main arm body 42 to interfere with the machined portion 102 clamped by the four rollers 44.

[0067] As described above, each arm 40 in standby mode is positioned slightly spaced from the outer circumferential surface of the machined portion 102. The minimum clearance c between the arm 40 in standby mode and the outer circumferential surface of the machined portion 102 needs to be determined taking into account the amount of overhang or swinging of the machined portion 102 during cutting machining. For example, when the machined portion 102 is massive, it overhangs a greater distance in the direction of gravity before being cut. Furthermore, when the shaft rotates at a higher speed, the machined portion 102 swings over a larger range due to centrifugal force. Since the minimum clearance c between the arm 40 in standby mode is desired to be greater than the overhang or swinging amount, the minimum clearance c between the arm 40 in standby mode can be set larger for a more massive machined portion 102 or a faster shaft rotation speed. Furthermore, the minimum clearance c can be a constant value or a variable value that changes as the cutting machining process progresses. For example, the minimum clearance c may gradually decrease as the cutting machining process progresses.

[0068] The determination of the completion of cutting by controller 28 will now be described in detail. Controller 28 monitors the state of the severing process of machined portion 102 and, upon determining that cutting is complete, switches clamping unit 38 from a standby state to a clamped state. It is known that the cutting resistance and rotational resistance of a shaft drop sharply upon completion of cutting. Based on this observation, in this embodiment, at least one of the cutting resistance and rotational resistance of the shaft is monitored during cutting machining, and the time at which the resistance drops sharply is determined to be the completion of cutting.

[0069] To monitor at least one of the cutting resistance and rotational resistance of shaft 18, a sensor (hereinafter referred to as "cutting determination sensor 46") is provided in this embodiment. The sensor measures a physical quantity dependent on at least one of the cutting resistance and rotational resistance of shaft 18. The physical quantity dependent on the cutting resistance includes, for example, the output torque and applied current of the motor that moves tool holder 20 in the X-direction or the X-direction movement motor, and the deflection of tool 110. These output torque, applied current, and twisting amount are all larger with greater cutting resistance. Meanwhile, physical quantities dependent on the rotational resistance of shaft 18 include, for example, the output torque and applied current of the rotation motor of shaft 18. These output torque and applied current are both larger with greater rotational resistance of shaft 18. Therefore, at least one of a torque sensor for measuring the torque of the X-direction movement motor, a current sensor for measuring the applied current of the X-direction movement motor, a twist sensor (e.g., a piezoelectric element) for measuring the twist of tool 110, a torque sensor for measuring the output torque of the rotation motor of shaft 18, and a current sensor for measuring the applied current of the rotation motor of shaft 18 is provided as cutting determination sensor 46 in this embodiment for determining whether cutting is complete.

[0070] The controller 28 determines the time when the measurement value measured by the cutting determination sensor 46 drops sharply as the time when the cutting is completed. Figure 7 FIG. 1 is a block diagram showing the electrical structure of the units involved in determining the time when cutting is completed. Figure 7 , the cutting determination sensor 46 is a sensor that measures a physical quantity that depends on at least one of the cutting resistance and the rotational resistance of the shaft 18. The measurement result by the cutting determination sensor 46 is input to the controller 28, and the controller 28 then determines whether the cutting of the machined portion 102 is completed based on the measurement value. For example, the controller 28 may perform time differentiation on the measurement value to determine the time at which the differential value D becomes equal to or less than a predetermined threshold value α (α<0) as the time at which the cutting is completed.

[0071] It is noted that the differentiation of the measured value and the comparison with the threshold value α can be performed in an analog or digital manner. For example, a commonly known differential circuit and a comparison circuit can be connected in series between the cutting determination sensor 46 and the controller 28, so that the output value from the comparison circuit is A / D converted before being input to the controller 28. Alternatively, the output value from the cutting determination sensor 46 can be A / D converted before being input to the controller 28, and then the controller 28 digitally differentiates the input measured value (discrete data) before being compared with the threshold value α. In either case, the measured value of the cutting determination sensor 46 can be low-pass filtered before the differentiation process to remove high-frequency noise. The threshold value α compared with the differential value D is a negative value and can be predetermined, for example, in an experiment. The threshold value α can be a fixed value or can be a variable value that varies, for example, depending on the diameter of the material 100 to be cut.

[0072] In any case, when the differential value D of the measured value becomes equal to or less than the threshold value α which is a negative value, the controller 28 determines that the cutting of the machined portion 102 is completed. In this case, the controller 28 drives the opening / closing actuator 48 provided to the clamping unit 38 to switch the clamping unit 38 from the standby state to the clamping state.

[0073] Figure 8 An example of changes in the measured value of the cutting determination sensor 46 and the minimum amount c of the gap is shown. Figure 8 , the upper graph indicates the measurement value of the current sensor (cutting determination sensor) installed on the X-direction moving motor of the tool holder 20; the middle graph indicates the differential value D of the measurement value; and the bottom graph indicates the minimum amount c of the gap between the arm 40 and the machined part 102.

[0074] like Figure 8As shown in the upper figure, when cutting machining begins and the tip of tool 110 contacts the circumference of material 100, the cutting resistance increases sharply, and subsequently, the current applied to the X-direction movement motor increases sharply. Once tool 110 engages material 100, the current sensor measurement value remains substantially constant. The controller 28 then gradually moves the tool holder 20 in the X-direction, causing the tip of tool 110 to move in the diametrical direction. When the tip of tool 110 reaches the center axis of material 100, the machined portion 102 is severed. As the machined portion 102 is severed, the cutting resistance decreases sharply, and the current sensor measurement value also decreases significantly.

[0075] like Figure 8 As shown in the middle graph in , the differential value of the measured value exhibits a large peak in the positive direction at the start of the cutting machine process and in the negative direction when the cutting is completed. The controller 28 determines that the cutting is completed at time t1 when the differential value D becomes equal to or less than the threshold value α.

[0076] From the start of cutting machining to the completion of cutting, the minimum clearance c between the arm 40 and the machined portion 102 remains substantially constant. At time t1, upon determining that cutting is complete, the controller 28 switches the clamping unit 38 from the standby state to the clamping state. Therefore, at time t1, the minimum clearance c between the arm 40 and the machined portion 102 begins to decrease rapidly, ultimately reaching zero, whereby the severed machined portion 102 is clamped by the clamping unit 38 and prevented from falling onto the floor surface.

[0077] See also Figure 9 , the process of cutting and collecting such a machined part 102 will now be described. In order to cut off the machined part 102, the material 100 and the tool 110 are pre-mounted on the shaft 18 and the tool holder 20, respectively, and the clamping unit 38 is set on standby (S10). Specifically, the arm 40 of the clamping unit 38 is kept open widely to a range larger than the diameter of the machined part 102, and the internal robot 26 is then driven to move the arm 40 to a position near the center of gravity of the machined part 102. In the above, the center of the circumscribed circle of the four rollers 44 is matched with the center of the machined part 102. Then, the arm 40 of the clamping unit 38 is closed until a predetermined gap is left between the arm 40 and the circumferential surface of the machined part 102 before being in the standby state.

[0078] With the clamping unit 38 in the standby state, the controller 28 drives the shaft 18 and the tool holder 20 to start cutting machining relative to the machined portion 102 (S12). In the above, because the pair of arms 40 are spaced apart from the machined portion 102, the clamping unit 38 does not apply an additional force to the machined portion 102. Therefore, the deviation and vibration of the material 100 can be prevented, so that a better cut section of the machined portion 102 can be obtained.

[0079] After the cutting machine processing starts, the controller 28 occasionally obtains the measurement value of the cutting determination sensor 46 and differentiates the measurement value; the cutting determination sensor 46 measures a physical quantity that depends on the cutting resistance or rotation resistance of the shaft (S14). The controller 28 then compares the obtained differential value D with a predetermined threshold value α (S16). When the comparison result shows that the differential value D is greater than the threshold value α, steps S14 to S16 are repeated. At the same time, when the differential value is equal to or less than the threshold value α, the controller 28 determines that the cutting is completed, and then switches the clamping unit 38 from the standby state to the clamping state (S18). That is, the opening / closing actuator 48 is driven to move a pair of arms 40 so that the arms 40 approach each other, thereby clamping the machined part 102. Through the above, the machined part 102 can be effectively prevented from falling onto the floor surface and thus prevented from being damaged by the impact of the fall.

[0080] Here, due to the instantaneous inertia after cutting, the machined part 102 continues to rotate. Since the arm 40 in this embodiment has a roller 44 that rolls on the circumferential surface of the machined part 102, the inertial rotation of the machined part 102 is not hindered, and damage to the machined part 102 due to friction can be effectively avoided. With the clamping unit 38 clamping the machined part 102, the controller 28 drives the internal robot 26 to carry the machined part 102 to the predetermined discharge port, and then ends the cutting and collection process (S20).

[0081] As will be apparent from the above description, the completion of the cutting of the machined portion 102 is monitored, maintaining the clamping unit 38 in a standby state until the cutting is complete. Upon completion, the clamping unit 38 is switched from the standby state to the clamped state. This effectively prevents the material 100 from shifting or vibrating during the cutting process, as the clamping unit 38 does not apply additional force to the material 100 during the cutting process. Consequently, the quality of the cut section of the machined portion 102 is further improved. Furthermore, since the machined portion 102 is clamped by the clamping unit 38 upon completion of the cutting process, damage to the machined portion 102 caused by its falling can be effectively prevented.

[0082] Here, after the machined portion 102 is cut off, the material 100 remains on the shaft 18. The material 100 remaining after machining (hereinafter referred to as "residual material") can also be collected using the internal robot 26 and the clamping unit 38. That is, after the machined portion 102 is carried to a predetermined discharge outlet, the controller 28 drives the internal robot 26 to move the clamping unit 38 (which opens wider than the diameter of the residual material) to a position near the center of gravity of the residual material. Then, the controller 28 drives the open / close actuator 48 to clamp the residual material at a position close to the center of gravity of the residual material using the clamping unit 38 and release the chuck 30. Then, the controller 28 drives the internal robot 26 to carry the residual material to a predetermined disposal location. As described above, collecting the residual material using the internal robot 26 and the clamping unit 38 achieves the collection of the residual material without damaging the machine tool 10.

[0083] Note that, although it is assumed in the above that the material is installed or removed from the front of the shaft 18, the material may be supplied from a bar feeder provided behind the shaft 18. Generally, when a bar feeder is used, the remaining material is pushed out by the newly supplied material and falls to the floor surface of the machine room 16 before being discharged by the sheet conveyor. In this case, the remaining material will damage the machine room 16.

[0084] In order to solve the above problem, when using a bar feeder, the clamping unit 38 and the internal robot 26 can also be used to collect the remaining material. In this case, the controller 28 opens a pair of arms 40 widely to a range larger than the diameter of the remaining material, and causes the clamping unit 38 to support the remaining material at a position close to the center of gravity of the remaining material. In addition, the controller 28 releases the chuck 30. In this case, the remaining material is supported at two points by the clamping unit 38 and the released chuck 30 respectively. Then, the controller 28 drives the bar feeder to supply new material to push the remaining material out through it. In the above, the controller 28 drives the internal robot 26 so that the clamping unit 38 is synchronized with the movement of the remaining material. When the rear end of the remaining material finally comes out of the chuck 30, the controller 28 closes the arms 40 of the clamping unit 38 to clamp the remaining material using the clamping unit 38.

[0085] Alternatively, the gripping unit 38 can support the remaining material near the tip of the remaining material until the remaining material is moved so that its center of gravity is exposed from the chuck 30. Once the center of gravity is exposed from the chuck 30, the remaining material can be clamped near the center of gravity of the remaining material. Specifically, the controller 28 moves the gripping unit 38 (which has a pair of arms 40 that open wider than the diameter of the remaining material) to a position near the tip of the remaining material, and the gripping unit 38 supports the remaining material near the tip of the remaining material. The controller 28 then releases the chuck 30 and drives the bar feeder to supply new material 100 to push the remaining material through it. Once the remaining material is moved so that its center of gravity is exposed from the chuck 30, the controller 28 closes the chuck 30 again, moves the gripping unit 38 to a position near the center of gravity of the remaining material, and closes the gripping unit 38 to clamp the remaining material. The controller 28 then releases the chuck 30 again and drives the internal robot 26 to carry the remaining material.

[0086] As described above, since the internal robot 26 and the gripper unit 38 are also used to collect the surplus material when the bar feeder is used, it is possible to prevent the surplus material from falling and causing damage to the machine chamber 16. In addition, since the gripper unit 38 grips the surplus material at a position close to the center of gravity of the surplus material, long surplus material can be reliably collected.

[0087] It should be noted that the structure described above is an example and can be modified arbitrarily. For example, the roller 44 provided to each arm 40 in the above description can be omitted. That is, since the material 100 is not clamped by the clamping unit 38 before the cutting is completed, the roller 44 is not necessary. However, since the machined part 102 continues to rotate for a period of time due to inertia after being cut from the material 100, it is desirable to provide a roller 44 to prevent friction between the machined part 102 and the arm 40. In any case, regardless of whether there is a roller 44, the contact surface between the arm 40 and the machined part 102 is expected to be soft so that the machined part 102 is not damaged. For example, the contact surface between the arm 40 and the machined part 102 (such as the circumferential surface of the roller 44) can be covered with an elastic material (such as rubber or sponge).

[0088] Although the time when the cutting is completed is determined based on the differential value D of the measurement value of the cutting determination sensor 46 in the above description, the time when the cutting is completed may be determined directly based on the measurement value of the cutting determination sensor 46 instead of the differential value D of the measurement value. For example, the time when the measurement value of the cutting determination sensor 46 becomes equal to or less than the threshold value β (see Figure 8) is determined as the time when cutting is completed. In addition, since the cutting resistance may fluctuate greatly immediately before the machined portion 102 is cut, depending on the machining method, in some cases, such fluctuation in cutting resistance may be detected to determine the time when the fluctuation is detected as the time when cutting is completed.

[0089] While the above description of cutting completion is based on the measurement value of only one cutting determination sensor 46, two or more cutting determination sensors 46 may be provided, and the cutting completion may be determined based on the measurement values ​​of these cutting determination sensors 46. For example, a current sensor for the shaft rotation motor, a current sensor for the X-direction movement motor of the tool holder 20, and an offset sensor for the tool 110 may be provided, and threshold values ​​α1, α2, and α3 may be set for the corresponding sensors. The time when the corresponding differential values ​​D1, D2, and D3 of the measurement values ​​of these three sensors are all equal to or less than the corresponding threshold values ​​α1, α2, and α3, that is, when D1 ≤ α1, D2 ≤ α2, and D3 ≤ α3, can be determined as the time when cutting is complete. This structure can prevent over-determination of cutting completion, that is, it can prevent erroneous determination of cutting completion before the actual cutting is complete. Alternatively, the time when any differential value D1, D2, or D3 of the corresponding measurement values ​​of the three sensors is equal to or less than a corresponding threshold value α1, α2, or α3, that is, the time when D1 ≤ α1, D2 ≤ α2, or D3 ≤ α3, can be determined as the time when cutting is completed. This structure can prevent determination failure, that is, it can prevent the erroneous determination that the cutting machine process is not completed when the cutting machine process has already been completed.

[0090] While the present embodiment determines the completion of cutting based on at least one of the cutting resistance and rotational resistance of the shaft, the cutting status may also be determined based on other parameters. For example, the position of the tip of the tool 110 may be estimated based on the position of the tool holder 20 in the X-direction, and the time when the tip of the tool 110 reaches the central axis of the material 100 may be determined as the completion of cutting. Alternatively, the time required to complete the cutting process may be estimated in advance based on the diameter of the material 100 or the feed speed of the tool 110, and the completion of cutting may be determined based on the time period that has elapsed since the start of the cutting process.

[0091] Although the multi-degree-of-freedom internal robot 26 is used as a moving device for moving the gripping unit 38 in the above description, any other moving mechanism may be used as long as the mechanism can move the gripping unit 38 at least in the Z-axis direction. For example, a Z moving mechanism may be provided on the ceiling of the machine room 16 so that the gripping unit 38 is suspended from the Z moving mechanism to be held.

Claims

1. A collecting mechanism for collecting machined portions severed from a material by rotary machining, the collecting mechanism comprising: a clamping unit having a pair of arms, the clamping unit clamping the machined part with the pair of arms, the clamping unit being switchable between a clamping state and a standby state; in the clamping state, the pair of arms are closed so as to contact the circumferential surface of the machined part that continues to rotate due to instantaneous inertia after cutting, thereby clamping the machined part; In the standby state, the pair of arms are opened so as to maintain proximity to the circumferential surface of the machined portion, which is clamped and rotated by the shaft before cutting is completed, with a certain gap between the pair of arms and the circumferential surface of the machined portion; a cutting determination sensor for measuring a physical quantity depending on at least one of a rotation resistance of a shaft rotatably clamping the material and a cutting resistance in cutting the material; as well as a controller for controlling the driving of the clamping unit; wherein the controller monitors whether the cutting of the machined portion is completed, so as to maintain the clamping unit in the standby state before the cutting is completed, and switches the clamping unit from the standby state to the clamping state when the cutting is completed; and the controller determines the time when the cutting of the machined portion is completed based on the differential value of the measurement value of the cutting determination sensor; wherein each of the paired arms comprises: main boom body; and one or more rollers mounted on the main arm body, and capable of rolling on the circumferential surface of the machined portion; the gripping unit having an opening / closing actuator for linearly advancing and retracting the pair of arms in a width direction of the gripping unit; and Each of the paired arms has two rollers linearly provided on the arm in a height direction of the gripping unit.

2. The collecting mechanism according to claim 1, characterized in that: At least one surface of the main arm body, the surface opposite to the other main arm body, is arcuate or curved so as to be convex in a direction away from the other main arm body.

3. The collecting mechanism according to claim 2, characterized in that: The cutting determination sensor includes a sensor that measures any one of the following: torque of a rotary motor of the shaft, current of the rotary motor, torque of a moving motor of a tool holder that clamps the tool, current of the moving motor, and twist of the tool; The controller determines a time at which a differential value of a measurement value of the cutting determination sensor becomes equal to or smaller than a threshold value that is a predetermined negative value as a time at which cutting off of the machined portion is completed.

4. The collecting mechanism according to any one of claims 1 to 3, characterized in that: Also includes: A multi-degree-of-freedom robot is installed in a machine room, wherein the gripping unit is attached to the robot as an end effector.

5. The collecting mechanism according to any one of claims 1 to 3, characterized in that: The controller controls the clamping unit so that the clamping unit collects remaining material remaining after the machined portion is cut off.

6. A method for collecting machined portions severed from a material by rotary machining, comprising: During cutting machining of the machined portion, monitoring whether severing of the machined portion is completed; as well as driving a clamping unit based on the monitoring result, so that before the cutting is completed, the clamping unit having a pair of arms is opened so that the pair of arms are kept close to the circumferential surface of the machined part that is clamped and rotated by the shaft before the cutting is completed, with a certain gap between the arms and the circumferential surface of the machined part; and so that when the cutting is completed, the clamping unit is closed so that the pair of arms are in contact with the circumferential surface of the machined part that is kept rotating due to instantaneous inertia after the cutting, thereby clamping the machined part; wherein the time of completion of the cutting is determined based on a differential value of a measurement value of a cutting determination sensor; wherein each of the paired arms comprises: main boom body; and one or more rollers mounted on the main arm body, and capable of rolling on the circumferential surface of the machined portion; the gripping unit having an opening / closing actuator for linearly advancing and retracting the pair of arms in a width direction of the gripping unit; and Each of the paired arms has two rollers linearly provided on the arm in a height direction of the gripping unit.

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