Machining method and machining system

Abstract

To provide a technique for efficiently and / or highly accurately performing machining by using a moving mechanism.SOLUTION: The machining system 10 includes a movement mechanism 12 and a work device 30 attached to the movement mechanism 12. The work device 30 includes a contact component 36 that comes into contact with the surface of the workpiece 20, and a rotary tool 34 that cuts into or is inserted into the workpiece 20 to machine the workpiece 20 in a state in which the contact component 36 presses or the surface of the workpiece 20. The moving mechanism 12 moves the rotary tool 34 cutting into or inserted into the workpiece 20 in a direction different from the rotation axis of the spindle.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to techniques for machining a workpiece using a tool. [Background technology]

[0002] Traditionally, aircraft manufacturing processes, which involve many large parts, have used large, highly rigid processing equipment. In recent years, the use of large, highly rigid processing equipment has also been considered in assembly processes for automobiles and other products, as parts have become larger using techniques such as Gigacast. However, since large processing equipment is expensive, research and development is being conducted into assembly work using small, low-rigidity robots with low cost. Patent Document 1 discloses a robot processing system equipped with a first robot that holds a processing tool and a second robot that holds a workpiece. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-171503 Summary of the Invention [Problem to be solved by the invention]

[0004] In machining and friction stir welding (FSW), the machining force and machining reaction force act simultaneously on the tool and workpiece according to the law of action and reaction, causing a relative displacement between them. The machining reaction force acts on a physical closed loop consisting of the tool, machine tool, and workpiece, and the magnitude of the relative displacement depends on the rigidity of the loop.

[0005] Figure 1 shows an example of a vertical articulated robot 1 used for drilling holes. This small vertical articulated robot 1 is equipped with a working device 3 as an end effector and uses a drill 4 to drill holes in a workpiece 2. During machining, the physical closed loop consisting of the vertical articulated robot 1, working device 3, drill 4, workpiece 2, and ground (floor) is large and has low loop rigidity, making it prone to static and dynamic displacement due to machining reaction forces and self-excited vibration. This makes it difficult to stably perform high-precision machining. For example, it is possible to suppress displacement and vibration by having another robot hold down the workpiece 2 from the other side, but this is costly.

[0006] Therefore, an object of the present disclosure is to provide a technology for performing processing efficiently and / or with high precision by utilizing a low-rigidity moving mechanism such as a robot. [Means for solving the problem]

[0007] One aspect of the present disclosure is a method for machining a workpiece using a working device attached to a moving mechanism, comprising a first step of contacting a contact part provided on the working device with the surface of the workpiece, a second step of cutting or inserting a rotating tool provided on the working device into the workpiece while the contact part is pressing or adsorbing the surface of the workpiece, and a third step of moving the rotating tool in a direction different from the rotation axis of the spindle.

[0008] Another aspect of the present disclosure is a machining system including a moving mechanism and a working device attached to the moving mechanism, wherein the working device has a contact part that contacts the surface of a workpiece and a rotary tool that cuts into or is inserted into the workpiece to machine the workpiece while the contact part presses or adsorbs against the surface of the workpiece, and the moving mechanism moves the rotary tool that is cutting into or inserted into the workpiece in a direction different from the rotation axis of the spindle.

[0009] Any combination of the above components and conversion of the expressions of the present disclosure into methods, devices, systems, etc. are also valid aspects of the present disclosure. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an example of a vertical articulated robot. [Figure 2] FIG. 1 is a diagram illustrating a processing system according to an embodiment. [Figure 3] FIG. 2 is a diagram showing a state in which a rotary tool is machining a workpiece. [Figure 4] FIG. 1 is a schematic diagram of the experimental setup. [Figure 5] 10(a) and 10(b) are diagrams showing the results of frequency analysis. [Figure 6] 1A and 1B show examples of contact parts that can move on a workpiece surface. [Figure 7] FIG. 2 is a diagram illustrating an example of a working device. [Figure 8] FIG. 10 is a diagram illustrating another example of a working device. [Figure 9] FIG. 10 is a diagram illustrating another example of a working device. [Figure 10] FIG. 10 is a diagram illustrating another example of a working device. [Figure 11] FIG. 10 is a diagram illustrating another example of a working device. [Figure 12] 10(a) and 10(b) are diagrams showing another example of a working device. DETAILED DESCRIPTION OF THE INVENTION

[0011] FIG. 2 shows a machining system 10 according to an embodiment. The machining system 10 includes a moving mechanism 12, a working device 30 attached to the moving mechanism 12, and a control device 100 that controls the operation of the moving mechanism 12 and the working device 30. The moving mechanism 12 shown in FIG. 2 is a robotic device equipped with multiple robot arms and a rotation mechanism for rotating the robot arms. The working device 30 is attached to the tip of the robot arm as an end effector. The working device 30 has a housing 40 shaped like a box with at least one side open, and processes a workpiece 20 using a rotary tool 34. The workpiece 20 may also be referred to as a workpiece, a workpiece material, or a workpiece. In the embodiment, the workpiece 20 is an automobile structure, but may also be other structures. The rotary tool 34 may be a cutting tool for machining, or a friction stir tool for friction stir processing by friction stir welding (FSW) or friction stir processing (FSP). The following description will mainly focus on the case where the rotary tool 34 is a cutting tool such as a drill or milling tool.

[0012] The movement mechanism 12 moves the working device 30 to a working position on the workpiece 20 and causes the rotary tool 34 to cut into the workpiece 20. The movement mechanism 12 shown in Fig. 2 is a low-rigidity vertical articulated robot device, but it may be another type of robot device, or it may be a movement device that does not have a robot arm and a rotation mechanism for rotating the robot arm. The movement mechanism 12 has the function of accurately positioning the working device 30 at a predetermined working position and imparting a feed motion to the rotating rotary tool 34.

[0013] The working device 30 includes a rotating device 32 that rotates the rotary tool 34, a contact element 36 that presses the workpiece 20, and a biasing mechanism 38 that applies a force to the contact element 36. The rotating device 32 has at least a spindle motor that rotates a spindle to which the rotary tool 34 is attached. The working device 30 preferably includes a plurality of contact elements 36 and a plurality of biasing mechanisms 38 that bias each of the plurality of contact elements 36. The biasing mechanism 38 has a spring mechanism and applies a force to the contact element 36 in a direction that pushes it outward. The rotating device 32 and the biasing mechanism 38 are housed in a housing 40.

[0014] The contact element 36 includes a linear rod-shaped element 36a and a pressing element 36b that presses a surface position of the workpiece 20 that is closer to the machining position of the rotary tool 34 than a surface position of the workpiece 20 positioned in the direction of movement of the rod-shaped element 36a. Here, the surface position of the workpiece 20 positioned in the direction of movement of the rod-shaped element 36a refers to a position where a line drawn through the center of the rod-shaped element 36a in the direction of movement of the rod-shaped element 36a intersects with the surface of the workpiece 20. The pressing element 36b is provided to press a surface of the workpiece 20 that is positioned between the surface position of the workpiece 20 positioned in the direction of movement of the rod-shaped element 36a and the machining position of the rotary tool 34. In the contact element 36 of this embodiment, the pressing element 36b is angled relative to the rod-shaped element 36a so as to face the axial direction of the rotary tool 34. The contact element 36 is formed of a metallic material and may have any cross-sectional shape. The cross-sectional shape of the rod-shaped member 36a may be, for example, circular, elliptical, or polygonal, and may be solid or hollow.

[0015] The rod-shaped member 36a is inserted into an opening of the guide portion 42, and the guide portion 42 guides the movement of the rod-shaped member 36a in a direction parallel to the rotation axis of the rotary tool 34. In the working device 30 shown in FIG. 2, two guide portions 42 are provided for one contact part 36, spaced apart in a direction parallel to the rotation axis, and each guide portion 42 restricts (limits) the movement of the rod-shaped member 36a in a direction perpendicular to the rotation axis of the rotary tool 34. In the working device 30, multiple guide portions 42 are provided for one rod-shaped member 36a, spaced apart in a direction parallel to the rotation axis, and the movement of the rod-shaped member 36a in a direction perpendicular to the rotation axis is restricted at least in two locations, thereby reliably guiding the movement of the rod-shaped member 36a in a direction parallel to the rotation axis of the rotary tool 34. The multiple guide portions 42 may form a linear guide. Furthermore, if one guide portion 42 has sufficient length and can restrict the movement of the rod-shaped member 36a in a direction perpendicular to the rotation axis at at least two locations within the guide portion 42 that are spaced apart in a direction parallel to the rotation axis, only one guide portion 42 may be provided.

[0016] In this embodiment, the pressing member 36b is angled relative to the rod-shaped member 36a in a direction approaching the rotary tool 34. If the size of the rotation device 32 is large, the rod-shaped member 36a will be positioned far away from the rotary tool 34. Therefore, by angling the pressing member 36b relative to the rod-shaped member 36a, the tip of the pressing member 36b can press near the processing position. For this reason, the guide portion 42 preferably has a structure that restricts the rotation of the rod-shaped member 36a.

[0017] In yet another example, the contact part 36 may be configured with a plurality of linear rod-shaped members 36a, a plate-shaped member fixed to the ends of the rod-shaped members 36a (the right ends in the example shown in FIG. 2), and a plurality of pressing members provided on the surfaces of the plate-shaped members. In this configuration example, the pressing members are provided so as to press a surface position of the workpiece 20 closer to the machining position where the rotary tool 34 performs machining than a surface position of the workpiece 20 positioned in the direction of movement of the rod-shaped members 36a. In this configuration example, the pressing members do not need to be angled relative to the rod-shaped members 36a. Note that, in a plane perpendicular to the rotation axis direction, it is preferable that the centers of gravity of the guide positions of the rod-shaped members 36a and the pressing positions of the pressing members 36b coincide with each other. By aligning the centers of gravity of the guide positions and the pressing positions, it is possible to avoid the generation of a moment that causes a change in posture during pressing.

[0018] The control device 100 communicates with the moving mechanism 12 and the working device 30, respectively, and synchronously controls the moving mechanism 12 and the working device 30. Before starting machining, the control device 100 controls the moving mechanism 12 to move the working device 30 to a location to be machined (a working location) on the workpiece 20. The control device 100 then drives the rotating device 32 to rotate the rotary tool 34, and controls the moving mechanism 12 to move the working device 30 in a direction approaching the workpiece 20 to press against the workpiece 20, causing the rotary tool 34 to cut into the workpiece 20, thereby machining the workpiece 20. In this example, the rotary tool 34 is a drill, and a hole is machined in the workpiece 20. Note that the control device 100 may also move the working device 30 in a direction approaching the workpiece 20 to press against the workpiece 20, and then rotate the rotary tool 34, causing the rotary tool 34 to cut into the workpiece 20, thereby machining the workpiece 20.

[0019] Before machining begins, that is, in the initial state of the working device 30, the tip of the rotary tool 34 is located further back in the axial direction than the tip of the pressing member 36b. Therefore, when the working device 30 is brought closer to the workpiece 20, the tip of the pressing member 36b comes into contact with the workpiece 20 first, and then the tip of the rotary tool 34 comes into contact with the workpiece 20.

[0020] 3 shows the state in which the rotary tool 34 is machining the workpiece 20. The pressing member 36b is biased by the biasing mechanism 38 to press against the surface of the workpiece 20. During machining, the pressing member 36b presses against the surface of the workpiece 20, thereby forming a very small closed loop between the rotary tool 34, housing 40, contact part 36, and workpiece 20. Therefore, when the contact part 36 applies pressure, the loop rigidity (dynamic rigidity) of the machining system 10 can be significantly increased, and problems such as static and dynamic displacement due to machining reaction forces and self-excited vibration can be eliminated.

[0021] According to the embodiment of the processing system 10, displacement and self-excited vibration during processing can be suppressed, so there is no need to use a large, highly rigid robot or to hold the back surface of the workpiece 20 with a separate robot device, which makes it possible to reduce processing costs.

[0022] In order to increase the loop rigidity, the guide portion 42 that supports the rod-shaped member 36a is preferably configured to have high rigidity. An elastic part may be provided at the tip of the pressing member 36b to prevent damage to the surface of the workpiece 20, but it is preferable that the elastic part be limited to a very thin one to prevent a substantial decrease in the loop rigidity.

[0023] In this embodiment, the biasing mechanism 38 biases the contact part 36 using a spring mechanism. The biasing mechanism 38 generates a pressing force based on the feed motion imparted to the rotary tool 34 by the moving mechanism 12. Specifically, the biasing mechanism 38 generates a pressing force corresponding to the displacement of the contact part 36 from contacting the surface of the workpiece 20 to retracting into the housing 40. The biasing mechanism 38 may use a damping mechanism instead of or in addition to the spring mechanism to generate a pressing force proportional to the feed rate. By configuring the biasing mechanism 38 in this manner, the operation of the moving mechanism 12 can simultaneously control the pressing direction feed position during machining (which may also be called the cutting motion) and press the workpiece 20 with the contact part 36.

[0024] The working device 30 may also include a feed device that imparts a feed motion to the rotary tool 34. The working device 30 may also include a biasing mechanism 38 that can adjust the pressing force P. In this case, the control device 100 can obtain information that correlates with the pressing force P applied to the workpiece 20 from motor current and torque information of the drive motor of the movement mechanism 12. The control device 100 can also obtain information that correlates with the thickness direction component F of the processing force from a feed device that linearly moves the spindle that rotates the rotary tool 34. The control device 100 may monitor the pressing force P and the thickness direction component F of the processing force, and perform control to adjust the pressing force P and the thickness direction component F of the processing force.

[0025] The control device 100 may acquire information correlated with the machining torque T from motor current and torque information of the spindle motor that rotates the rotary tool 34. The control device 100 may perform control to adjust the pressing force P and the machining torque T by monitoring the pressing force P and the machining torque T.

[0026] In the embodiment, the contact part 36 contacts and presses against the surface of the workpiece 20, thereby forming a very small closed loop among the rotary tool 34, the housing 40, the contact part 36, and the workpiece 20. However, the contact part 36 may form a small closed loop by other means. For example, the contact part 36 may be provided with a mechanism that generates an adhesive force, and may contact and adhere to the surface of the workpiece 20. For example, the contact part 36 may be provided with a structure that generates electromagnetic force, and may be adhered to the surface of the metal workpiece 20. The contact part 36 may also press against the surface of the workpiece 20 while being adhered to the surface. The contact part 36 may also be provided with a mechanism that clamps the workpiece 20, and may clamp both sides of the workpiece 20 to fix the working device 30 to the workpiece 20.

[0027] 4 is a schematic diagram of an experimental device 50 that was prototyped to demonstrate the effects of the processing system 10 of the embodiment. Since this experimental device 50 uses a machine tool rather than a robot, an elastic structure 72 that simulates the low rigidity of a robot is attached to the workpiece side, which is made of two overlapping aluminum plate materials 70a and 70b.

[0028] A housing 60 containing a guide portion 62 and a spring mechanism 58 is attached to the spindle housing 52 of the machine tool, and a contact part 56 for pressing against the workpiece is biased by the spring mechanism 58. In this experimental device 50, the contact part 56 presses against an aluminum plate 70a independently at two points symmetrical about the rotation axis of the drill 54. Note that increasing the number of points pressing against the aluminum plate 70a can further increase the loop rigidity, but whether or not to press independently depends on the application. For example, if the plate has various curvatures or the pressing points are restricted, being able to press by independently displacing the parts provides greater versatility.

[0029] Using the experimental device 50, holes were drilled in both cases where the contact part 56 did not press against the aluminum plate 70a, and the vibration of the plate was measured. Figure 5(a) shows the frequency analysis results when no pressure was applied, and Figure 5(b) shows the frequency analysis results when pressure was applied. Both Figures 5(a) and (b) show the results of frequency analysis of acceleration measured in two directions perpendicular to the thickness direction of the plate during processing, and converting it into displacement. As shown in Figure 5(a), severe self-excited vibration occurred when no pressure was applied, but as shown in Figure 5(b), it was confirmed that applying pressure suppresses self-excited vibration and enables stable processing.

[0030] The machining system 10 of the embodiment has a function of moving the rotary tool 34 in a direction different from the rotation axis of the rotary tool 34. In the embodiment, the machining system 10 moves the rotary tool 34 in a direction parallel to the surface of the workpiece 20. By moving the rotary tool 34 in a direction parallel to the surface of the workpiece 20, the machining system 10 enables machining by machining feed in a direction perpendicular to the rotation axis, such as groove machining, side machining, trimming, and tapered surface machining (deburring) using an end mill or grinding wheel, as well as joining by FSW and material modification by FSP (Friction Stir Processing).

[0031] FIG. 6 shows an example of a contact element 78 that can move on the surface of the workpiece 20. A plate member 76 is provided at the lower end of the pressing mechanism 74, and a rotary tool 34, such as an end mill, passes through an opening 86 provided in the center of the plate member 76 to machine the workpiece 20. In the example shown in FIG. 6, four contact elements 78 are provided on the lower surface of the plate member 76 so as to surround the opening 86. The multiple contact elements 78 are provided with sufficient spacing between them to prevent material clogging. The multiple contact elements 78 are preferably provided at positions symmetrical with respect to the rotation axis.

[0032] In this example, the contact part 78 may be a free ball bearing. By using a free ball bearing for the contact part 78, it becomes possible to move the rotary tool 34 relative to the workpiece 20 in two directions perpendicular to the axial direction while multiple free ball bearings are pressing against the surface of the workpiece 20. Note that the balls may be made of a resin material or the ball surfaces may be coated with a thin elastic material to prevent contact marks from being left on the workpiece 20 by the contact part 78. The movement mechanism 12 can feed the rotary tool 34 cutting into the workpiece 20 in two directions perpendicular to the rotation axis of the spindle. Note that with this configuration, it is also possible to move the rotary tool 34 around the rotation axis, but this is usually not useful for machining using a rotary tool.

[0033] When roller bearings are used for the contact parts 78, the rotary tool 34 can be moved in one direction perpendicular to the rotation axis while movement in the other direction is restricted (limited) while multiple roller bearings are pressing against the surface of the workpiece 20. For example, when machining a linear groove, linear groove machining can be efficiently achieved by allowing movement in only one direction and restricting (limiting) movement in the other directions.

[0034] Conditions such as the pressing force in the processing system 10 will be considered below. First, let us consider the force P normal to the contact surface when the contact part 36 presses or adsorbs the workpiece surface. This force P normal to the contact surface is called the "pressing force P" when the contact part 36 presses the workpiece surface, and the "adsorption force P" when the contact part 36 adsorbs to the workpiece surface. However, for the sake of convenience, it will be simply referred to as the "pressing force P." Note that when the contact part 36 generates a pressing force and an adsorption force simultaneously, the force P normal to the contact surface is the sum of the pressing force and the adsorption force. Because the pressing force P must not cause the contact part 36 to separate from the workpiece surface during machining, the pressing force P on the contact surface must always be positive [Condition 1].

[0035] Next, when machining is performed while the rotary tool 34 moves in a direction parallel to the contact surface of the workpiece (a direction perpendicular to the rotation axis), the working device 30 is equipped with a guide that allows movement in that direction, but the guide must have sufficient dynamic rigidity. Since it is not easy to provide a guide with high rigidity in the direction of movement (a spring mechanism can achieve a short stroke, but it is not possible to achieve both high rigidity and a long stroke), it is effective to increase the friction force to improve damping. Generally, friction force increases in proportion to the normal force P, so in order to achieve dynamic rigidity in the direction of movement parallel to the contact surface, the normal force P must be greater than a predetermined value W (the normal force corresponding to the required damping) [Condition 2].

[0036] Furthermore, when no machining feed is performed in the direction within the contact surface, or when the movable direction of the rotary tool 34 is limited to one direction parallel to the contact surface and movement in another direction is constrained (restricted), in order to prevent slippage in the constrained direction, the product μP of the friction coefficient μ in the constrained direction and the normal force P must be larger than the machining force component Fr in that direction [Condition 3]. Note that this directional component Fr includes a translational component of the machining force in that direction and a directional force component that occurs at the radial position of the contact point due to the machining torque.

[0037] From the above, it is preferable that the pressing force P of the workpiece satisfies conditions 1 and 3 when no machining feed is performed in the direction within the contact surface, it is preferable that conditions 1 and 2 are satisfied when the rotating tool 34 is movable in two perpendicular directions within the contact surface, it is preferable that conditions 1 and 2 are satisfied when the rotating tool 34 is movable in one direction and is constrained in the other direction, it is preferable that conditions 1 and 2 are satisfied in the direction of movement, and it is preferable that conditions 1 and 3 are satisfied in the direction of constraint. [Condition 1] P>0 [Condition 2] P>W [Condition 3] μP>Fr ∴P>Fr / μ Regarding condition 1, if condition 2 or condition 3 is met, then condition 1 will always be met. Furthermore, in an actual machining system 10, there is not only a high-rigidity closed loop created by contact between the contacting parts and the workpiece 20, but also an inherently large low-rigidity closed loop. Because this large low-rigidity closed loop receives a small amount of force, the action of this low-rigidity closed loop may make it possible to restrict movement in a direction parallel to the contact surface or in a constraint direction, even if condition 2 or condition 3 is not completely satisfied.

[0038] Below, we will explain structural examples of the working device 30. While Fig. 6 shows a structure in which the contact part 78 is movable on the surface of the workpiece 20, Figs. 7 to 9 below show examples of working device 30 that has a structure in which the contact part is fixed to the surface of the workpiece 20 and in which the rotary tool 34 can be moved by a moving mechanism provided above the fixed structure.

[0039] FIG. 7 shows an example of a working device 30. The working device 30 includes a rotating device 102 that rotates the rotating tool 34 and a contact element 120 that contacts and attracts the workpiece 20. The rotating device 102 has at least a spindle motor that rotates a spindle to which the rotating tool 34 is attached. The contact element 120 has an electromagnet, receives power from the control device 100, and attracts the metal workpiece 20. When the contact element 120 attracts the workpiece 20, a very small closed loop can be formed among the rotating tool 34, the rotating device 102, the guide 110, the guide 112, the contact element 120, and the workpiece 20. The end surface (attraction surface) of the contact element 120 may be coated with a thin elastic material to prevent the contact element 120 from leaving a contact mark on the workpiece surface.

[0040] The working device 30 includes a guide unit 110 that guides movement of the rotating tool 34 in the rotation axis direction, and a guide unit 112 that guides movement of the rotating tool 34 in a direction perpendicular to the rotation axis. The guide unit 110 has a rail 110a that extends in a direction parallel to the rotation axis and a block 110b that is connected to a part of the rotating device 102, and the block 110b moves along a movement trajectory determined by the rail 110a. The guide unit 112 has a rail 112a that extends in a direction perpendicular to the rotation axis and a block 112b that is connected to a part of the rail 110a, and the block 112b moves along a movement trajectory determined by the rail 112a. The working device 30 may further include a guide unit that includes a rail that extends in a direction perpendicular to the rail 110a and the rail 112a. Spring 114 is provided to determine the initial position of block 110b relative to rail 110a, and spring 116 is provided to determine the initial position of block 112b relative to rail 112a. Springs 114 and 116 are provided to prevent the initial positions of the blocks from becoming indefinite, so their spring constants can be small.

[0041] During machining, while the contact part 120 is attached to the surface of the workpiece 20, the control device 100 controls the movement mechanism 12 to cause the rotary tool 34 to cut into the workpiece 20, and then moves the rotary tool 34 in a direction perpendicular to the rotation axis. At this time, the movement mechanism 12 moves the rotary tool 34 in a direction parallel to the rotation axis along a movement trajectory determined by the rail 110a to cut into the workpiece 20, and then moves the rotary tool 34 in a direction perpendicular to the rotation axis along a movement trajectory determined by the rail 112a. By forming a physically small closed loop, static and dynamic displacements due to machining reaction forces and self-excited vibrations can be suppressed.

[0042] The guide portion 110 and the guide portion 112 may be linear guides with adjustable preload. When the contact part 120 adheres to the workpiece 20, it is preferable to satisfy the conditions 1 and 3 so that the adhering surface does not slip due to the machining force.

[0043] FIG. 8 shows another example of the working device 30. The working device 30 includes a rotating device 102 that rotates the rotating tool 34 and a contact element 122 that contacts the workpiece 20 and clamps both sides of the workpiece 20. The rotating device 102 has at least a spindle motor that rotates a spindle to which the rotating tool 34 is attached. The contact element 122 includes a clamping mechanism 126 that clamps and secures the workpiece 20, and an actuator 124 that receives power from the control device 100 and drives the clamping mechanism 126. Clamping the workpiece 20 with the contact element 122 allows a very small closed loop to be formed among the rotating tool 34, the rotating device 102, the guide unit 110, the guide unit 112, the contact element 122, and the workpiece 20. The end faces of the contact element 122 that clamp the workpiece 20 may be coated with a thin elastic material to prevent contact marks from being left on the workpiece surface by the contact element 122. The working device 30 includes guide portions 110 and 112, which are linear guides with adjustable preload.

[0044] When the contact part 122 clamps the workpiece 20, a clamping force Pc is applied to both sides of the workpiece, so it is preferable to satisfy the following condition 3a to prevent the clamping surfaces from slipping due to the processing force. [Condition 3a] 2μPc>Fr ∴Pc>Fr / 2μ

[0045] FIG. 9 shows another example of the working device 30. The working device 30 includes a rotating device 102 that rotates the rotary tool 34, a contact element 128 that contacts and presses against a recessed portion of the workpiece 20, and a biasing mechanism 118 that applies a force to the contact element 128. The biasing mechanism 118 has a spring mechanism and applies a downward force to the contact element 128. The contact element 128 has multiple tapered portions that protrude downward, and the multiple tapered portions fit into multiple tapered recessed portions formed in the workpiece 20. The multiple tapered portions of the contact element 128 press against the tapered surfaces of the recessed portions to fix the working device 30 to the workpiece 20. When the contact element 128 is pressed against the workpiece 20, a very small closed loop can be formed among the rotary tool 34, the rotating device 102, the guide portion 110, the guide portion 112, the contact element 128, and the workpiece 20. The working device 30 includes guide units 110 and 112, which are linear guides with adjustable preload. The plurality of tapered recesses may be formed in a jig fixed to the workpiece 20. Alternatively, the plurality of tapered recesses may be provided in the contact part 128, and tapered protrusions may be provided on the surface of the workpiece 20 or on the jig fixed to the workpiece 20.

[0046] When the multiple tapered portions of the contact part 128 press against the tapered recesses of the workpiece 20, the condition 3b for preventing slippage on the mating surfaces can be determined as follows using the taper angle θ and the friction coefficient μ. [Condition 3b] μ(Frcosθ+Pfsinθ)>Frsinθ-Pfcosθ ∴ Pf>Fr(sinθ-μcosθ) / (μsinθ+cosθ) Condition 3b is satisfied by condition 1 in the region where (sinθ - μ cosθ) < 0, i.e., tanθ < μ. For example, when μ = 0.3, if θ < 16.7 degrees, all that is required is a pressing force against the positive tapered surface. Note that if the angle θ is set too small, the pressing force will not allow the contact part 128 to be released from the workpiece 20.

[0047] 10 shows another example of working device 30. In this working device 30, damping mechanism 130 is provided in the movement direction of block 110b in guide section 110, and damping mechanism 132 is provided in the movement direction of block 112b in guide section 112. By providing damping mechanism 130 and damping mechanism 132 in this way, it is possible to increase the dynamic rigidity in the movement direction.

[0048] Since the working device 30 of this embodiment is driven by a low-rigidity moving mechanism 12, it is necessary to ensure high dynamic rigidity by increasing damping in the direction in which the rotary tool 34 is movable, among the three orthogonal directions, i.e., the normal direction of the contact surface and two directions within the contact surface. For this reason, damping may be increased by adding damping mechanisms 130, 132 to the guide sections 110, 112 as shown in Fig. 10, or by increasing the guide surface normal load (preload) of the guide sections 110, 112 to increase frictional force. The preload conditions may be set in accordance with the required damping, similar to condition 2.

[0049] 11 shows another example of the working device 30. In order to improve machining accuracy, the working device 30 is equipped with a position sensor 140 that measures the relative movement amount of the block 110b with respect to the rail 110a, and a position sensor 142 that measures the relative movement amount of the block 112b with respect to the rail 112a. Therefore, the position sensor 140 measures the movement amount of the rotary tool 34 along the movement trajectory determined by the rail 110a, and the position sensor 142 measures the movement amount of the rotary tool 34 along the movement trajectory determined by the rail 112a. The position sensors 140 and 142 may be, for example, linear encoders.

[0050] If the position of the rotary tool 34 is measured using a sensor provided on the moving mechanism 12, the low rigidity of the moving mechanism 12 will result in a large measurement error due to its elastic displacement. Therefore, by providing a position sensor 140 on the movement path determined by the rail 110a and a position sensor 142 on the movement path determined by the rail 112a, it becomes possible to accurately measure the machining position and / or machining path based on the contact position between the operating device 30 and the workpiece 20. To accurately identify the contact position, the relative positional relationship between the operating device 30 and the workpiece 20 can be determined by photographing a marker provided at a predetermined position with a camera. Alternatively, as shown in FIG. 9, the relative positional relationship between the operating device 30 and the workpiece 20 may be physically determined by fitting a contact part 128 to the workpiece 20.

[0051] In the machining system 10 of the embodiment, all movements of the working device 30 are performed in a passive manner using the moving mechanism 12, which is a low-rigidity robot device. By employing such a passive mechanism, it is possible to realize the machining system 10 at low cost. On the other hand, in cases where it is necessary to actively change the control characteristics in the feed direction, where higher servo rigidity is required, or where it is necessary to monitor the process from control information, a mechanism for actively driving some of the feed axes by motor control or the like may be provided in the working device 30.

[0052] 12(a) shows another example of the working device 30. The working device 30 includes a rotating device 150 that rotates the rotary tool 34, a contact part 164 for pressing the workpiece 20, and a biasing mechanism 166 that applies a force to the contact part 164. The biasing mechanism 166 has a spring mechanism and applies a downward force to the contact part 164. The rotating device 150 includes at least a spindle motor that rotates a spindle to which the rotary tool 34 is attached.

[0053] The working device 30 includes multiple guides 160 that guide the movement of the rotary tool 34 in the rotation axis direction and multiple guides 162 that guide the movement of the rotary tool 34 in a direction different from the rotation axis. The guides 160 include a rail 160a extending in a direction parallel to the rotation axis and a block 160b connected to a portion of the rotating device 150, and the block 160b moves along a movement trajectory determined by the rail 160a. The guides 162 include a rail 162a extending in a direction different from the rotation axis and a block 162b connected to a portion of the rail 160a, and the block 162b moves along a movement trajectory determined by the rail 162a. The rail 162a may be provided parallel to the surface of the workpiece 20, but does not have to be parallel. The rail 162a may have a portion that moves up and down in the cutting direction, depending on, for example, the depth of the groove formed by the rotary tool 34.

[0054] The movement path defined by the rail 160a is provided with a mechanical stopper 170 for limiting the downward movement of the rotary tool 34. When the rotary tool 34 descends, the block 160b abuts against the stopper 170, preventing the rotary tool 34 from descending further. This prevents the rotary tool 34 from cutting too deeply into the workpiece 20, and allows the amount of cutting to be determined accurately.

[0055] Fig. 12(b) shows the AA cross section in Fig. 12(a). The movement trajectory determined by the rail 162a includes a curve. For example, the movement trajectory determined by the rail 162a may be a trajectory that combines a circular arc and a straight line. When performing groove machining using an end mill or joining processing using FSW, a movement trajectory that includes a curve is practical.

[0056] A mechanical stopper 172 is provided on the movement trajectory determined by the rail 162a to limit the movement of the rotary tool 34. When the rotary tool 34 moves laterally, the block 162b abuts against the stopper 172, thereby preventing the rotary tool 34 from moving further. This prevents the rotary tool 34 from cutting too much of the workpiece 20, and makes it possible to accurately determine the machining end position.

[0057] An elastic member such as a spring or rubber may be inserted between the working device 30 and the low-rigidity moving mechanism 12. Inserting an elastic member can mitigate the influence of positional errors of the low-rigidity moving mechanism 12 on the machining accuracy.

[0058] We will consider a method to increase the friction force and damping by increasing the normal load (preload) on the guide surface of the guide section. An example of a rough calculation of the relationship between the preload of the guide section and the required damping is shown below.

number

[0059] The present disclosure has been described above based on the embodiments. This embodiment is merely an example, and those skilled in the art will understand that various modifications are possible in the combination of each component and each process, and that such modifications are also within the scope of the present disclosure. In the embodiments, the rotary tool 34 is described as a cutting tool such as a drill or milling tool. However, the rotary tool 34 may also be a friction stir tool for performing friction stir processing using FSW or FSP. During friction stir processing, the friction stir tool is inserted into the workpiece 20, which is a metallic material, while rotating at high speed. The generated friction heat softens the base material, and the rotational force causes plastic flow and mixing of the workpiece 20 near the tool insertion point. The working device 30 of the embodiment allows the friction stir tool to move relatively with high dynamic rigidity in a direction parallel to the surface of the workpiece 20, enabling accurate friction stir processing over a wide range.

[0060] In the embodiment, the guide unit 112 guides the movement of the rotary tool 34 in a direction perpendicular to the rotation axis. However, the guiding direction is not limited to the direction perpendicular to the rotation axis, and the guide unit 112 may guide the movement of the rotary tool 34 in a direction different from the rotation axis. For example, if the workpiece surface is curved, the guide unit 112 may guide the movement of the rotary tool 34 along the workpiece surface. In this case, the guide unit 112 may be provided so that the distance from the workpiece surface is constant. Furthermore, if it is desired to change the cutting depth of the rotary tool 34 into the workpiece 20, the guide unit 112 may be provided so that the distance from the workpiece surface is variable. Furthermore, in the embodiment, the rotation axis of the rotary tool 34 is perpendicular to the workpiece surface. However, this is not limited to being perpendicular. For example, when forming a tapered surface on a workpiece by end milling, the workpiece may be cut with the rotation axis tilted by the taper angle, and the tapered surface may be machined with the side cutting edge of the end mill.

[0061] The outline of the aspects of the present disclosure is as follows. One aspect of the present disclosure is a method for machining a workpiece using a working device attached to a moving mechanism, the method comprising: a first step of contacting a contact part provided on the working device with the surface of the workpiece; a second step of cutting or inserting a rotary tool provided on the working device into the workpiece while the contact part is pressing or adsorbing the surface of the workpiece; and a third step of moving the rotary tool in a direction different from the rotation axis of the spindle. The first step may be to engage a recess or protrusion provided on the workpiece with a protrusion or recess provided on the contact part. The second step may be performed before the third step, or the second and third steps may be performed simultaneously, or the third step may be performed before the second step. For example, the rotary tool may cut into the workpiece while being fed. The rotary tool may be a cutting tool for machining or a friction stir tool for friction stir machining.

[0062] According to this type of machining method, by bringing the contact parts provided on the working device into contact with the workpiece surface, the loop rigidity of the machining system can be increased, and static and dynamic displacements due to machining reaction forces and self-excited vibrations can be suppressed.

[0063] The second step may include moving the rotary tool along a movement path determined by the first guide unit. The movement path may be provided with a position sensor that measures the amount of movement of the rotary tool. The movement path may be provided with a stopper that limits the movement of the rotary tool. The first guide unit may be a linear guide with adjustable preload.

[0064] The third step may include moving the rotary tool in a direction different from the rotation axis of the spindle along a movement path determined by the second guide unit. The movement path determined by the second guide unit may include a curve. A position sensor that measures the amount of movement of the rotary tool may be provided on the movement path. A stopper that limits movement of the rotary tool may be provided on the movement path. The second guide unit may be a linear guide with adjustable preload.

[0065] Another aspect of the present disclosure is a machining system including a moving mechanism and a working device attached to the moving mechanism, wherein the working device has a contact part that contacts the surface of a workpiece and a rotary tool that cuts into or is inserted into the workpiece to machine the workpiece while the contact part presses or adsorbs against the surface of the workpiece, and the moving mechanism moves the rotary tool that is cutting into or inserted into the workpiece in a direction different from the rotation axis of the spindle.

[0066] According to this type of machining system, by bringing the contact parts of the working device into contact with the surface of the workpiece, the loop rigidity of the machining system can be increased, and static and dynamic displacements due to machining reaction forces and self-excited vibrations can be suppressed. [Explanation of symbols]

[0067] 10 Machining system, 12 Moving mechanism, 20 Workpiece, 30 Working device, 32 Rotating device, 34 Rotating tool, 36 Contact part, 36a Rod-shaped member, 36b Pressing member, 38 Biasing mechanism, 40 Housing, 42 Guide part, 50 Experimental device, 52 Spindle housing, 54 Drill, 56 Contact part, 58 Spring mechanism, 60 Housing, 62 Guide part, 70a, 70b Aluminum plate material, 72 Elastic structure, 74 Pressing mechanism, 76 Plate member, 78 Contact part, 86 Opening, 100 Control device, 102 Rotating device, 110 Guide portion, 110a, rail, 110b, block, 112, guide portion, 112a, rail, 112b, block, 114, 116, spring, 118, biasing mechanism, 120, 122, contact part, 124, actuator, 126, clamping mechanism, 128, contact part, 130, 132, damping mechanism, 140, 142, position sensor, 150, rotation device, 160, guide portion, 160a, rail, 160b, block, 162, guide portion, 162a, rail, 162b, block, 164, contact part, 166, biasing mechanism, 170, 172, stopper.

Claims

1. A method for machining a workpiece using a working device attached to a moving mechanism, comprising: a first step of bringing a contact element provided on the working device into contact with a surface of the workpiece; a second step of cutting or inserting a rotary tool provided on the working device into the workpiece while the contact part is pressing or sucking against the surface of the workpiece; a third step of moving the rotary tool in a direction different from the rotation axis of the spindle; A processing method characterized by comprising:

2. The rotary tool is a cutting tool for performing machining or a friction stir tool for performing friction stir processing. The processing method according to claim 1 .

3. the second step includes a step of moving the rotary tool along a movement trajectory determined by a first guide unit. The processing method according to claim 1 .

4. a position sensor for measuring a movement amount of the rotary tool is provided on the movement trajectory; The processing method according to claim 3 .

5. a stopper for limiting the movement of the rotary tool is provided on the movement trajectory; The processing method according to claim 3 .

6. The first guide portion is a linear guide with adjustable preload. The processing method according to claim 3 .

7. the third step includes a step of moving the rotary tool in a direction different from the rotation axis of the spindle along a movement trajectory determined by a second guide unit. The processing method according to claim 1 .

8. The movement trajectory includes a curve. The processing method according to claim 7 .

9. a position sensor for measuring a movement amount of the rotary tool is provided on the movement trajectory; The processing method according to claim 7 .

10. a stopper for limiting the movement of the rotary tool is provided on the movement trajectory; The processing method according to claim 7 .

11. The second guide portion is a linear guide with adjustable preload. The processing method according to claim 7 .

12. the first step includes fitting a recess or a protrusion provided on the workpiece with a protrusion or a recess provided on the contact component; The processing method according to claim 1 .

13. A processing system including a moving mechanism and a working device attached to the moving mechanism, The working device is a contact part that contacts the surface of the workpiece; a rotary tool that cuts into or is inserted into the workpiece to machine the workpiece while the contact part is pressing or sucking the surface of the workpiece, The moving mechanism moves the rotary tool cutting into or inserted into the workpiece in a direction different from the rotation axis of the spindle. A processing system characterized by:

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