Quick clamping system for connecting machine tools with robots

Abstract

The invention relates to a quick clamping system for mounting a tool or machine tool on a robot. According to one embodiment, the quick clamping system comprises a chuck having a base plate configured for mounting on a flange positionable by a robot, a tool holder configured for mounting on a machine tool, wherein the tool holder has a mounting plate which in a locked state rests on the base plate of the chuck, two or more pins configured to align the mounting plate on the base plate in a mounted state and to prevent a movement of the mounting plate relative to the base plate in a plane parallel to the base plate, at least one elastic element, and a clamping lock configured for locking the tool holder on the base plate of the chuck, wherein in the locked state the elastic element is deformed and causes a pre-tension between the base plate and the mounting plate.

Description

Technical Field

[0001] This invention relates to a rapid clamping system for connecting machine tools and robots. Background Technology

[0002] In robot-assisted surface finishing, machine tools (such as grinding machines, drilling machines, milling machines, polishing machines, etc.) are guided by robotic arms (such as industrial robots). Here, the machine tool can be connected to the robotic arm's so-called TCP (tool center point) in various ways; typically, the position and orientation of the robotic arm's TCP can be arbitrarily adjusted to allow the machine tool to move along a trajectory (e.g., parallel to the workpiece surface). Industrial robots are typically position-controlled, enabling the TCP to move precisely along the desired trajectory.

[0003] To achieve good results in robot-assisted grinding or other surface finishing processes, the process force (grinding force) needs to be controlled in many applications, which is often difficult to achieve with sufficient precision using traditional industrial robots. The large and heavy-duty arms of industrial robots have too much inertia for closed-loop controllers to react quickly enough to fluctuations in process force. To address this issue, a smaller (and lighter) linear actuator, compared to the industrial robot, can be placed between the robot's TCP and the machine tool, connecting the robot's TCP to the machine tool. During surface finishing, the linear actuator only controls the process force (i.e., the clamping force between the tool and the workpiece), while the robot moves the machine tool, along with the linear actuator, along a position-controlled path. Through force control, the linear actuator can compensate for inaccuracies in the position and shape of the workpiece and, (within certain limits) for inaccuracies in the robot's path. However, even without the aforementioned linear actuator, there are robots that can adjust the process force using force / torque control.

[0004] Various clamping systems are known to connect and disconnect different machine tools from a robot. In simpler systems, the operator must manually change the tools on the robot. Robots typically require relatively high precision, and currently commercially available clamping systems are relatively complex and expensive. Summary of the Invention

[0005] The objective of this invention is to provide a relatively simple and sufficiently accurate quick clamping system for connecting machine tools for many applications.

[0006] The above-described task is accomplished by the apparatus according to claim 1. Different implementations and modifications are the subject of the dependent claims.

[0007] This invention relates to a quick clamping system for mounting tools or machine tools onto a robotic arm. According to one embodiment, the quick clamping system includes: a chuck having a base plate configured for mounting onto a flange capable of being positioned by the robotic arm; a tool holder configured for mounting onto a machine tool, wherein the tool holder has a mounting plate abutting against the base plate of the chuck in a locked state; two or more pins configured to align the mounting plate on the base plate in the assembled state and prevent movement of the mounting plate relative to the base plate in a plane parallel to the base plate; at least one resilient element; and a clamping lock configured to lock the tool holder onto the base plate of the chuck, wherein in the locked state, the resilient element deforms and causes a preload force between the base plate and the mounting plate. Attached Figure Description

[0008] The different implementations will now be explained in more detail based on the examples shown in the accompanying drawings. The drawings are not necessarily to scale, and the invention is not limited to the aspects shown. Rather, the purpose is to illustrate the basic principles of the illustrated embodiments.

[0009] Figure 1 This is an exemplary schematic diagram of a robot-assisted grinding device, which includes a grinding machine connected to an industrial robot via a force-controlled linear actuator; the linear actuator causes partial mechanical decoupling between the industrial robot and the grinding machine.

[0010] Figure 2 This is an exploded perspective view of an example of a quick clamping system used to connect machine tools to robots.

[0011] Figure 3 yes Figure 2 A side view of an example.

[0012] Figure 4 This is a perspective view of the quick clamping system in the clamping state.

[0013] Figure 5 It shows Figure 4 The system includes machine tools. Detailed Implementation

[0014] Before explaining the different embodiments in detail, a general example of a robot-assisted grinding apparatus is first described. It should be understood that the concepts described herein can be applied to other types of surface finishing (e.g., polishing, milling, drilling, etc.) and are not limited to grinding. Using the quick-clamping system described herein, virtually any component can be quickly connected to the robot.

[0015] according to Figure 1The robot-assisted grinding device includes a manipulator 80 (e.g., an industrial robot) and a grinding machine 50 with a rotating grinding tool 51, wherein the grinding device is connected to the so-called tool center point (TCP) of the manipulator 1 via a linear actuator 20. TCP is not strictly a point, but a vector, and can be described, for example, by three spatial coordinates (position) and three angles (orientation). In robotics, generalized coordinates in configuration space (mostly the six hinge angles of the robot) are sometimes used to describe the position of TCP. The position and orientation of TCP are sometimes referred to as "pose". The position (including orientation) of TCP, as a function of time, defines the motion of the grinding tool, called its trajectory. TCP is often defined as the center point of the robot's end effector flange, but this is not always the case. TCP can be any point (and theoretically can be located outside the robot), whose position and orientation can be adjusted by the robot. TCP can also define the origin of the tool coordinate system.

[0016] In the case of an industrial robot with six degrees of freedom, the manipulator 80 can be constructed from four sections 82, 83, 84, and 85, which are respectively connected by hinges G. 11 G 12 and G 13 Connection. The first segment 82 is mostly rigidly connected to the base 81 (however, this is not always the case). Hinge G 11 Connecting sections 82 and 83. Hinge G 11 It can be 2-axis, and allows segment 83 to rotate about a horizontal axis of rotation (elevation) and a vertical axis of rotation (azimuth). Hinge G 12 Connecting segment 83 and segment 84, and allowing segment 84 to pivot relative to the position of segment 83. Hinge G 13 Connecting sections 84 and 85. Hinge G 13 It can be 2-axis, and therefore (similar to hinge G) 11 The manipulator enables pivoting motion in two directions. The TCP has a fixed relative position with respect to section 85, and typically includes a rotary hinge (not shown) that allows the end effector flange 86, arranged on section 85, to rotate about the longitudinal axis A of section 85. Figure 1 (Seen as dashed lines, also corresponding to the rotation axis of the grinding tool in the illustrated example). Actuators (e.g., electric motors) capable of causing rotational motion about the respective hinge axis are assigned to each axis of the hinge. The actuators in the hinge are controlled by robot control unit 70 according to the robot program. Different industrial robots / manipulators and their associated control units are well-known and therefore will not be further described here.

[0017] The robotic arm 80 is typically position-controlled, meaning the robot control unit can determine the TCP's posture (position and orientation) and cause the TCP to move along a predetermined trajectory. Figure 1 In this diagram, the TCP is located on the longitudinal axis of segment 85, denoted by A. The posture of the TCP is also used to define the posture of the grinding machine 50 (and the grinding disc 51) when the actuator 90 is against the end stop. As mentioned at the beginning, the actuator 90 is used to adjust the contact force (process force) between the tool and workpiece 60 to the desired value during the grinding process. For grinding applications, force control directly performed by the robot 80 is generally not very precise due to the large mass inertia of segments 83 to 85 of the robot 80, making it practically impossible to quickly compensate for force peaks (e.g., when placing the grinding tool onto the workpiece 60) using conventional robots. Therefore, the robot control unit 70 is configured to control the posture (position and orientation) of the TCP of the robot 80 while simultaneously controlling the force using only the actuator 90.

[0018] As already mentioned, during the grinding process, the contact force F between the grinding tool (grinding machine 50 with grinding disc 51) and the workpiece 60 can be controlled by means of a linear actuator 90 and a force regulator (which can be implemented, for example, in the control device 70). K Adjust to ensure that the contact force F between the grinding disc 51 and the workpiece 60 is... K (In the direction of the longitudinal axis A) corresponds to a predetermined theoretical value. Here, the contact force F K It is for the actuator force F A In response to the lack of contact between the workpiece 60 and the tool 51, the linear actuator 90 presses against the workpiece surface using its actuator force. When there is no contact between the workpiece 60 and the tool 51, due to the lack of contact force on the workpiece 60, the actuator 90 moves toward the end stop (not shown, integrated in the actuator 2) and presses against the end stop with a defined force. Here, force control remains active throughout. Therefore, in this case (no contact), the actuator offset is at its maximum, and the actuator 90 is in its abutment position. The defined force (the force with which the actuator 90 presses against the end stop) can be very small or (theoretically) even controlled to zero in order to achieve the smoothest possible contact on the workpiece surface.

[0019] The position control of the robotic arm 80 (which can also be achieved in the control unit 70) can operate completely independently of the force control of the actuator 90. The actuator 90 is not responsible for the positioning of the grinding machine 50, but only for adjusting and maintaining the desired contact force F during the grinding process. K It is also used to detect the contact between tool 51 and workpiece 60. For example, based on the actuator moving away from its contact position (actuator offset a at the end stop is less than the maximum offset a). MAX This allows for simple detection of the contact.

[0020] Actuator 90 can be a pneumatic actuator, such as a double-acting pneumatic cylinder. However, other pneumatic actuators, such as bellows cylinders and air sleeves, can also be used. Alternatively, an electric direct drive (gearless mechanism) can also be considered. It should be understood that the direction of action of actuator 90 and the axis of rotation of grinding machine 50 do not necessarily have to coincide with the longitudinal axis A of section 85 of robot arm 80. In the case of a pneumatic actuator, force control can be achieved in a manner known per se by means of a control valve, controller (e.g., implemented in control device 70), and compressed air reservoir or compressor. Because the tilt relative to the vertical is important for taking into account gravity (i.e., the gravity of grinding machine 50), actuator 2 can include a tilt sensor or this information can be determined based on the hinge angle of robot arm 80. The measured tilt is taken into account by the force controller. The specific implementation of force control is known per se and is not important for further explanation, and therefore will not be described in more detail. The actuator 90 not only achieves a certain degree of mechanical decoupling between the robot arm 80 and the workpiece 60, but also compensates for the inaccuracy of TCP positioning.

[0021] Figure 2 An exemplary implementation of a quick clamping system is shown, which makes it relatively easy to connect and disconnect machine tools (such as grinding machines, polishing machines, or milling machines) from a robot. Figure 2 A portion of the aforementioned linear actuator 90 is shown, one end of which is connected to the end effector flange 85 (located at the distal end of the robot's arm segment 85, see...). Figure 1 The actuator 90 is connected to the machine tool, and its other end itself has a flange 91 for assembling the machine tool. Therefore, the actuator 90 is often also referred to as the "active flange" because the actuator is able to actively adjust the force between the end effector flange and the machine tool. Figure 3 It corresponds to Figure 2 Side view. Figure 4 This is a perspective view of the assembled quick clamping system in the locked state.

[0022] according to Figure 2The quick-clamping system essentially includes a chuck 10 (called a chuck or clamping chuck in English) that can be mechanically connected to a flange 91 (e.g., by means of bolts). The quick-clamping system also includes an elastic element configured as a rubber disc 20 in this example and a tool holder 30 that can be mechanically and rigidly connected to a machine tool. In addition to rubber, materials suitable for the disc 20 may include plastic elastomers. The flange 91 has multiple threaded holes 210. In the example shown, the flange 91 has six threaded holes 210, into which a pin 11 is screwed. The pin has a cylindrical shape in the upper section and threads 110 in the lower section that can be screwed into the threaded holes 210. The pin (locating pin) is also commonly referred to as a locating pin. Instead of a threaded connection, the pin (without threads) can also be glued or pressed into the corresponding hole. The screw-in cylindrical pin 11 serves as a guide for the tool holder 30, preventing the tool holder 30 from being positioned relative to the z-axis (the axis perpendicular to the plane of the base plate 15, see...). Figure 2 The tool holder 30 is tilted. More generally, the pin 11 is used to prevent the mounting plate 31 of the tool holder 30 from moving relative to the base plate 15 of the chuck 10 in a plane (xy plane) parallel to the base plate plane, while allowing a certain degree of movement perpendicular to the plane.

[0023] The chuck 10 essentially has a base plate 15 and two or more clamping clamps 13 mounted on its sides. The base plate 15 has multiple holes 12 (typically drilled holes). Figure 3 In this example, the base plate 15 has six holes. A cylindrical pin 11, screwed into the flange 91, passes through three of the drilled holes 12 to secure the chuck. The other three drilled holes 12 are for inserting bolts 14, which can be screwed into corresponding threaded drilled holes 21 within the flange 91 to secure the base plate 15 to the flange 91. Figure 2 In the example, the six threaded holes 210 are offset by 60°, so the three cylindrical pins 11 and the three bolts 14 can be offset by 120° (relative to the z-axis).

[0024] The base plate 15 has two cantilever arms 16 projecting toward the flange 91 on its side, the cantilever arms clamping the base plate 15 at an angle of approximately 90° (see [link]). Figure 3 Clamping clamps 13 are fitted onto these cantilever arms (e.g., by means of bolts). It should be mentioned that the column pins 11 can also be fitted onto the base plate 15 (e.g., screwed into said base plate) (instead of screwing into the flange 91). However, in maintaining the required tolerances, Figure 2The variant shown may be better (depending on the specific application), in which the column pin 11 is screwed into the flange 91. For it to function, the column pin 11 must extend from the base plate 15 at a right angle to the base plate.

[0025] Tool retainer 30 is rigidly attached to the machine tool (in Figures 2 to 4 (Not shown in the diagram) Connection. The specific construction of the tool holder 30 depends on the machine tool. In particular, those components of the tool holder 30 for securing the tool holder to the machine tool are variable and adapted to the corresponding machine tool. The tool holder 30 may be said to include an interface that allows the machine tool to be clamped into the chuck 10. The tool holder 30 has a mounting plate 31 with drill holes 33 and hooks 32. The mounting plate 32 mates with the base plate 15 of the chuck 10. In the assembled state, the mounting plate 32 of the tool holder 30 is inserted into a cylindrical pin 11, which extends through the drill holes 33. Therefore, the cylindrical pin 11 defines the position of the tool holder 30 in the x and y directions (i.e., perpendicular to the z-axis in the xy plane) (and thus also defines the position of the machine tool). In the clamped state, the mounting plate 32 of the tool holder 30 rests against the base plate 15 of the chuck 10, and the clamping clamps 13 (supports) are hooked into their respective hooks 32 and clamped (the hooks are sometimes referred to as holders). Thus, the clamping clamps 13 and the hooks together constitute the clamping lock. An elastic element (a rubber disc 20 arranged between the base plate 15 and the mounting plate 32 in the illustrated example) allows the tool holder 30 to undergo small elastic movements relative to the chuck 10 in the z-direction. The elastic element (e.g., the rubber disc 20) can deform (the rubber disc 20 is compressed) when the clamping lock is locked and is responsible for pre-tensioning the clamping lock in the locked state. That is, in the locked state, the clamping clamps 13 pull the corresponding hooks 32 (and vice versa). Simultaneously, the elastic element / rubber disc 20 is in a deformed, pre-tensioned state. The clamping clamps 13 and their respective hooks 32 are known and commercially available, and therefore will not be discussed further here.

[0026] Each clamping locking element (traction latch), consisting of a clamping clamp 13 and a hook 31 combined with an elastic element, is also called a stop locking element (eccentric pin) because the clamping clamp 13 engages with the corresponding hook 32 when locked, and then pivots about the hinge 131 until the stop of the pivoting movement and beyond the stop. The clamping locking element / stop locking element thus reliably prevents accidental release because the clamping clamp 13 cannot move back beyond the stop without external force. This external force must be manually applied by the operator when locking and unlocking the clamping locking element.

[0027] It should be noted that the rubber disc 20 is merely one example of an elastic element. Generally, any elastic element is suitably (anywhere in a quick-clamping system) arranged such that it elastically deforms when the clamping closure (clamping clamp 13 and hook 32) is locked, and in the locked state applies a preload absorbed by the clamping closure in the z-direction between the chuck 10 and the tool holder 30. Small movement of the tool holder 30 relative to the chuck 10 in the z-direction is achieved by elastic deformation, while relative movement in the x and y directions is prevented by a column pin 11, which acts as a linear guide. Instead of the rubber disc 20, one or more elastic elements can be integrated into the clamping clamp 13 or hook 32. In this case, the rubber disc 20 can be omitted. For example, a portion of the hook 32 and / or clamping clamp 13 can itself be formed of an elastic or flexible material (at least partially). In this case, it is sometimes referred to as a flexible clamping closure fastener (flexible traction latch) or a clamping band closure. Alternatively, the clamping clamp 13 may be elastically supported on the cantilever 16 of the base plate 15 by means of a spring in the z-direction. Additionally or alternatively, the hook 32 may be elastically supported on the mounting plate 31 by means of a spring element or other elastic element. Additionally or alternatively, the support sleeve of the hinge 131 of the clamping clamp 13 may also be formed of an elastic material and allow the aforementioned elastic deformation when the clamping closure is locked.

[0028] Figure 5 The robot is shown being assembled in (the robot is in Figure 5 Not shown in the image, see [link / reference]. Figure 1 The linear actuator 90 on the ) has according to Figures 2 to 4 The example is a locking quick-clamping system in which a rod-shaped grinding machine 50 is fixed to a tool holder 30. As mentioned, the tool holder 30 serves as an interface for clamping the machine tool onto the chuck 10 of the quick-clamping system.

[0029] The rapid clamping system described herein is particularly applicable to robots capable of controlling the contact force between the tool and workpiece surfaces. As mentioned, this force control can be achieved either by means of actuator 90 or (where the robot is suitable) by the robot itself. In this case, actuator 90 can also be omitted and chuck 10 can be directly mounted on end effector flange 86 (see [link to documentation]). Figure 1 Instead of being mounted on flange 91 of actuator 90. In both cases (with or without actuator 90), the contact force (process force) is regulated during the surface finishing process, wherein during the finishing process, Figures 2-4The z-direction shown is typically perpendicular to the workpiece surface and is also the direction of the controlled contact force. Any potential inaccuracies in the machine tool's positioning in the z-direction will be compensated for by force control, as the machine tool is always pressed against the workpiece with a defined, controlled force. Therefore, inaccuracies in the machine tool's position caused by deformation of elastic elements (e.g., rubber disc 20) are practically negligible. These inaccuracies can also be compensated for virtually automatically by force control. Even when torque affects the quick-clamping system, this will not cause significant tilting or xy-displacement of the tool holder 30 relative to the chuck 10, as these movements are prevented by the cylindrical pin 11 extending into the bore 33. Thus, the torque is absorbed by the quick-clamping system. The only degree of freedom is a (very small) elastic movement in the z-direction, which is compensated for by force control as mentioned above.

[0030] Finally, it should be noted that the positions of hook 32 and clamping clamp 13 are interchangeable, although in practice it may be more meaningful for the clamping clamp to be supported on the base plate of chuck 10 (rather than on the mounting plate 13 of tool holder 30). Similarly, the position of the pin relative to the base plate 15 of chuck 10 is also important. Figure 2 It is irrelevant whether the pin 11 is guided through the drilled hole 33 in the mounting plate 31, or whether the pin is fixed (e.g., screwed into) to the mounting plate 31 and guided through the corresponding hole in the chuck 10. The pin 11 also need not be a separate component and could theoretically be manufactured integrally with the base plate 15 or the mounting plate 31 (although this would be more complex). In this case, the base plate (or mounting plate) and the pin would be integral components. The pin also need not be cylindrical; any shape is possible, as long as it engages with a corresponding opening in the opposite portion to prevent movement in a plane parallel to the base plate and allow small movements perpendicular to the base plate.

[0031] In another example, the linear actuator 90, along with the quick-clamping system and the machine tool, is not fixed to the manipulator (industrial robot), but rather to a stationary (fixed-position) base. In this case, the robot holds the workpiece in a positional manner so that the machine tool can access and process the workpiece held by the robot. The robot operates in a position-controlled manner and moves the workpiece along a predetermined trajectory during the machining process, while the linear actuator 90, mounted on the fixed base, performs force control and presses the machine tool against the workpiece held by the robot. An example of such a system is described in published document US 2018 / 0126512 A1, but this system does not include the quick-clamping system.

Claims

1. A quick clamping system, comprising: a chuck (10) having a base plate (15) configured for assembly on a flange (86, 91) positionable in a force-regulated manner by means of a robot (80, 90) or a linear actuator (90), a tool holder (30) configured for assembly on a machine tool, wherein the tool holder (30) has an assembly plate (31) which, in a locked state, lies against the base plate (15), two or more pins (11) configured to align the assembly plate (31) on the base plate (15) in an assembled state and to prevent movement of the assembly plate (31) relative to the base plate (15) in a plane parallel to the base plate (15), at least one elastic element (20), and a clamping lock (13, 32) configured to lock the tool holder (30) on the base plate (15) of the chuck (10), wherein, in the locked state, the elastic element (20) is deformed and causes a pretension between the base plate (15) and the assembly plate (31) to maintain the locking of the tool holder (30) and the base plate (15); wherein the at least one elastic element (20) comprises a disc of elastic material arranged between the base plate (15) and the assembly plate (31) and the clamping lock comprises a plurality of clamping clips (13) and hooks (32) corresponding to the clamping clips (13).

2. The quick clamping system of claim 1, wherein, The at least one elastic element (20) is part of the clamping lock.

3. The quick clamping system according to claim 1, wherein the hooks (32) are assembled on the tool holder (30) and the clamping clips are pivotably supported on the base plate (15), or wherein the hooks (32) are assembled on the base plate (15) and the clamping clips are pivotably supported on the tool holder (30).

4. The quick clamping system according to any one of claims 1 to 3, wherein the pins (11) extend in the assembled state into corresponding holes in the assembly plate (31), and / or wherein the pins (11) extend in the assembled state into corresponding holes in the base plate (32).

5. The quick clamping system according to any one of claims 1 to 3, wherein the pins (11) are assembled on the flange (86, 91) and extend through corresponding holes (12, 33) of the base plate (15) and the assembly plate (31).

6. The quick clamping system according to any one of claims 1 to 3, wherein the clamping lock (13, 32) comprises a dead point lock.

7. An apparatus for machining a surface of a workpiece in a robot- assisted manner, comprising: a quick clamping system according to any one of claims 1 to 6, wherein the flange positionable in a force-regulated manner is a first flange of the linear actuator (90), a robot (80), wherein a second flange of the linear actuator (90) is connected to an end effector flange (86) of the robot (80), wherein the manipulator (80) is configured for positioning the linear actuator (90) together with a machine tool (50) in a position-controlled manner relative to the workpiece (60), wherein the machine tool (50) is connected to the linear actuator (90) by the fast clamping system and the linear actuator (90) is configured for adjusting a force between the machine tool (50) and the workpiece (60).

8. An apparatus for machining a surface of a workpiece in a robotically assisted manner, comprising: the fast clamping system according to any one of claims 1 to 6, wherein the flange positioned in a force-controlled manner is a first flange of the linear actuator (90), a position-fixed base on which a second flange of the linear actuator is mounted; a manipulator (80) configured for holding a workpiece and positioning the workpiece relative to a machine tool (50), wherein the machine tool (50) is connected to the linear actuator (90) by the fast clamping system, wherein the linear actuator (90) is configured for adjusting a force between the machine tool and the workpiece.

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