Replacement station for automatically replacing grinding parts

Abstract

The invention relates to components of a replacement station for the automated replacement of grinding elements (grinding discs) of a robot-assisted grinding device, as well as to an associated method for mounting grinding elements on a grinding machine, and to an associated method for pulling out worn grinding elements from a grinding machine.

Description

Technical Field

[0001] The invention relates to a changing station which enables the automated changing of abrasive parts, such as grinding fleece discs (also known as non-woven abrasives), in a robot-assisted grinding device. Background Art

[0002] Grinding machines, such as orbital grinders, are widely used in industry and trade. Orbital grinders convert oscillating motion (vibration) into rotational motion about an axis of rotation. Orbital grinders are typically used for final finishing of surfaces with high surface quality requirements. To achieve these requirements, irregularities should be avoided as much as possible during the grinding process. In practice, this is often achieved by having experienced specialists perform this task exclusively for smaller part production runs.

[0003] In robot-assisted grinding systems, a grinding tool (e.g., an orbital grinder) is guided by a robotic arm (e.g., an industrial robot). The grinding tool can be coupled in various ways to the robotic arm's so-called end effector (whose position determines the TCP (Tool Center Point)), allowing the robotic arm to position the machine tool virtually anywhere. Industrial robots are typically position-controlled, enabling precise movement of the TCP along the desired trajectory. To achieve good results with robot-assisted grinding, many applications require regulation of the process force (grinding force), which is often difficult to achieve with sufficient accuracy using conventional industrial robots. The larger and heavier arm sections of industrial robots have excessive mass inertia, exceeding the ability of the regulator (closed-loop controller) to respond quickly enough to fluctuations in the process force. To address this issue, a linear actuator, smaller than that of the industrial robot, can be arranged between the robotic arm's end effector and the grinding tool to couple the end effector to the grinding tool. The linear actuator merely adjusts the process force (ie the pressing force between the tool and the workpiece), while the robot arm moves the grinding tool and the linear actuator along a predeterminable trajectory in a position-controlled manner.

[0004] In robot-assisted grinding, a changing station is used, with the help of which a robot can automatically change the grinding element (e.g., grinding disc). This changing station typically consists of a pull-out unit, which removes worn grinding discs from the grinding machine's carrier plate (backing pad), and a magazine with new grinding discs, which is designed so that the robot can "take" the new grinding discs from the magazine and fasten them to the carrier plate. In many applications, the grinding discs are secured to the carrier plate using hook and loop fasteners (Velcro fasteners).

[0005] Changing stations for automatically changing abrasive parts are generally designed specifically for a certain type of abrasive part. In many grinding processes, abrasive discs made of abrasive felt (also known as non-woven abrasive) are used. Unlike abrasive discs made of abrasive paper, abrasive discs made of abrasive felt are significantly thicker and softer, which has an impact on the requirements of the changing process (for example, felt can tear more easily than paper). Although there are several concepts for robot-assisted changing stations for changing abrasive discs, the known solutions are relatively complex, difficult to implement, and therefore expensive. Even in robot-assisted grinding processes, worn abrasive discs are usually still replaced manually.

[0006] That is, one of the basic objects of the present invention can be considered to be to provide a pull-out unit and a magazine that can enable robot-assisted grinding equipment to automatically replace grinding discs (especially relatively thick and soft grinding discs such as felt grinding discs) in a relatively simple and still reliable manner. Summary of the Invention

[0007] This object is achieved by means of a device and a method according to the independent claims. Various embodiments and developments are the subject matter of the dependent claims.

[0008] A method for removing an abrasive article from a robot-assisted grinding machine will now be described. According to one embodiment, the method comprises: positioning the grinding machine near a clamping mechanism of a pullout device at a curved support element of the pullout device by means of a robot arm; clamping the abrasive article by closing the clamping mechanism; performing a rolling motion of the grinding machine by means of the robot arm while the abrasive article contacts the curved support element, thereby partially releasing the abrasive article from a carrier plate of the grinding machine; pulling the grinding machine back by means of the robot arm so that the abrasive article is completely released from the carrier plate; and releasing the clamping mechanism.

[0009] Furthermore, a method is described for automatically mounting abrasives provided in a magazine onto a carrier plate of a robot-assisted grinding machine. According to one embodiment, the method comprises: pressing the abrasive (e.g., the topmost abrasive in a stack of abrasives) against the back side of a retaining ring by means of a linear actuator, wherein the linear actuator is force-regulated and presses the abrasive against the retaining ring with a defined pressing force; positioning the grinding machine above the magazine by means of a robot arm and pressing the carrier plate of the grinding machine against the top side of the retaining ring, thereby attaching the abrasive to the carrier plate; reducing the pressing force from a first value to a second, lower value; and subsequently pulling the grinding machine back from the magazine by means of the robot arm, thereby pulling the abrasive attached to the carrier plate out of the magazine through the retaining ring. After the grinding machine has been pulled back, the pressing force can be increased again to the first value.

[0010] The pulling device and the device with the magazine can be combined to form a replacement station for automatically replacing abrasive pieces. According to one embodiment, the pulling device for removing abrasive pieces from a robot-assisted grinding machine comprises: a curved placement element for the abrasive piece, the curved placement element being mounted on a carrier plate of the grinding machine; and a clamping mechanism configured to clamp the abrasive piece by closing the clamping mechanism in a clamping direction, while the abrasive piece is positioned on the curved placement element at an angle relative to the clamping direction.

[0011] According to one embodiment, an apparatus for automatically mounting abrasive pieces provided in a magazine onto a carrier plate of a robot-assisted grinding machine comprises: the magazine, which is formed for receiving a stack of the abrasive pieces, wherein the magazine has a retaining ring; a linear actuator, which is formed for forcing the stack of abrasive pieces against the retaining ring; a controller for the linear actuator, which is formed for setting a pressing force for forcing the stack of abrasive pieces against the retaining ring, so that the pressing force is initially a defined first value, wherein the controller is formed to reduce the pressing force from the first value to a lower second value while forcing the stack of abrasive pieces further against the retaining ring so that the topmost abrasive piece in the stack can be easily pulled out. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention will be described in detail below with reference to the exemplary embodiments shown in the accompanying drawings. The drawings are not necessarily to scale and the invention is not limited to the aspects shown. Instead, the basic principle of the invention is illustrated. In the drawings:

[0013] Figure 1 An example of a robot-assisted grinding apparatus is schematically shown.

[0014] Figure 2 The grinding tool and the grinding disk as well as the fastening of the grinding disk to the grinding tool are shown schematically.

[0015] Figure 3 Another example of a robot-assisted grinding apparatus is schematically shown.

[0016] Figure 4 An example of a magazine is shown, which enables the automatic installation of grinding discs on a grinding machine.

[0017] Figure 5 Shown Figure 4 An example of a retaining ring for a silo.

[0018] Figure 6 and Figure 7 The example shows the automated installation of the grinding wheel from the silo onto the grinding machine.

[0019] Figure 8 An exemplary embodiment of the automated installation of the grinding wheel from the silo to the grinding machine is presented with the aid of a flow chart.

[0020] Figure 9 An example shows Figure 8 A sub-aspect of the method.

[0021] Figure 10 A removal device for automatically removing a grinding wheel from a carrier plate of a grinding machine is shown.

[0022] Figure 11-16 Several (intermediate) steps of a removal process for automatically removing a grinding wheel from a carrier plate of a grinding machine are shown.

[0023] Figure 17 An example of a removal process for the automated removal of a grinding wheel is presented with the aid of a flow chart.

[0024] Figure 18 Shows the Figure 10 A modification / extension of the example. DETAILED DESCRIPTION

[0025] Before explaining various embodiments of the present invention in detail, an example of a robot-assisted grinding device is first described. This grinding device includes a robot arm 1, such as an industrial robot, and a grinding machine 10 (e.g., an orbital grinder) having a rotating grinding tool, wherein this grinding tool has an end effector and is therefore coupled to the TCP of the robot arm 1 via a linear actuator 20. In the case of an industrial robot with six degrees of freedom, the robot arm can be composed of four segments 2a, 2b, 2c, and 2d, which are connected via joints 3a, 3b, and 3c, respectively (see FIG. 2 ). Figure 1 ). The first segment 2d is in most cases rigidly connected to the base 41 (however, this is not necessarily the case). The joint 3c connects the segments 2c and 2d. The joint 3c can be of two-axis type and can enable a rotation of the segment 2c around a horizontal axis of rotation (pitch) and a vertical axis of rotation (azimuth). The joint 3b connects the segments 2b and 2c and can enable a pivoting movement of the segment 2b relative to the position of the segment 2c. The joint 3a connects the segments 2a and 2b. The joint 3a can be of two-axis type and can therefore (analogously to the joint 3c) enable a pivoting movement in two directions. Segment 2a forms the end effector and therefore has a fixed relative position with respect to the TCP. Segment 2a typically also has a rotary joint (not shown), which can enable a rotational movement around the longitudinal axis of segment 2a (in Figure 1 Each joint axis is assigned an actuator that can cause a rotational movement about the corresponding joint axis. The actuators in the joint are controlled by the robot controller 4 according to the robot program.

[0026] The robot arm 1 is typically position-controlled, meaning that the robot controller can determine the pose (position and orientation) of the TCP and move it along a predefined trajectory. When the actuator 20 abuts the end stop, the pose of the grinding tool is also defined along with the pose of the TCP. As mentioned at the outset, the actuator 20 is used to set the contact force (process force) between the tool (grinder 10) and the workpiece 40 to the desired value during the grinding process. Direct force control by the robot arm 1 is generally too imprecise for grinding applications because, due to the high mass inertia of the segments 2a-c of the robot arm 1, force peaks (e.g., when the grinding tool is attached to the workpiece 40) cannot be quickly compensated with conventional robots. For this reason, the robot controller is designed to control the pose of the robot arm's TCP, while force control can be performed entirely by the actuator 20.

[0027] As already mentioned, during the grinding process, the contact force FK between the tool (grinding machine 10) and the workpiece 40 can be set using a (linear) actuator 20 and a force control (e.g., which can be implemented in the controller 4) so that the contact force between the grinding tool and the workpiece 40 corresponds to a predefined setpoint value. The contact force corresponds to the actuator force of the linear actuator 20 pressing against the workpiece surface (and also the weight of the grinding machine). If contact between the workpiece 40 and the tool is lost, the actuator 20 resists the movement of the end stop due to the lack of contact force on the workpiece 40. The position control of the robot arm 1 (which can also be implemented in the controller 4) can operate completely independently of the force control of the actuator 20. The actuator 20 is not responsible for positioning the grinding machine 10, but rather for setting and maintaining the desired contact force during the grinding process and for detecting contact between the tool and the workpiece. The actuator can be a pneumatic actuator, such as a double-acting cylinder. However, other pneumatic actuators, such as bellows cylinders and pneumatic muscles, are also suitable. Alternatively, direct electric drives (electric drives without a gearbox) are also conceivable.

[0028] In the case of a pneumatic actuator, force regulation can be achieved in a manner known per se by means of a regulating valve, a regulator (implemented in the control unit 4 ) and a compressed air reservoir. However, the specific implementation is not important for the further explanation and is therefore not described in detail.

[0029] The grinding machine 10 has a grinding disc 11 mounted on a carrier disc 12. The surface of the carrier disc 12 or the back surface of the grinding disc 11, or both surfaces, are provided so that the grinding disc 11 can be attached to the carrier disc 12 without difficulty by contact. For example, a hook-and-loop fastener is used to keep the grinding disc 11 attached to the carrier disc. A releasable adhesive connection, a releasable snap-on connection, or a similar connection can also be used.

[0030] Figure 2 Figure a shows a grinding machine 10 with an installed grinding wheel 11. During operation, the carrier plate 12 is driven by the motor of the grinding machine 10, and the grinding wheel 11 rotates along with the carrier plate 12 (rotation axis A). In the case of an orbital grinding machine, the carrier plate 12 performs a complex movement, namely, rotating about two parallel rotation axes with a defined axis offset. The grinding wheel 11, for example, consists of a grinding felt, is flexible (bendable), and can be pulled out of the carrier plate. Figure 2 b shows the grinding machine 10 with the grinding disc 11 pulled out. In addition to the side view, Figure 2 c also shows a bottom view of the grinding wheel 11 (in the direction of the axis of rotation A).

[0031] Figure 3Another example of a grinding machine 10 mounted at an actuator 20 is shown in FIG. The actuator 20 has a structure that can be connected to a robot arm 1 (e.g. Figure 1 The first flange 21 is rigidly connected to the end effector 2a in the second flange ( Figure 3 The end of the actuator 20 opposite the flange 21 is located at the end where the grinder 10 is mounted. Figure 3 The figure also shows, for example, a connection 15 for a hose, via which the grinding dust can be extracted. However, the extraction of grinding dust is optional. It should be noted at this point that felt grinding discs are usually Figure 3 The one shown is much thicker.

[0032] Even if the grinding process is automated using robot-assisted grinding equipment, the replacement of the grinding disc is usually still carried out manually, in that the operator grasps the edge of the grinding disc 11 with the thumb and index finger and then pulls it out of the carrier plate. Existing automatic solutions for automatically changing grinding discs are relatively complex, the complexity arising, for example, from the fact that the grinding disc 11 must be grasped before being pulled out of the mechanical device. The embodiments described herein can provide advantages in particular in the case of thick and flexible grinding discs (for example, formed from grinding felt). In the following, a magazine for grinding discs will first be described, which allows the automatic filling of a robot-guided grinding machine with (new) grinding discs. In addition, a corresponding method is described. Subsequently, a pulling-out device and a corresponding method are described, which allow the automatic removal of grinding discs from the carrier plate of the grinding machine.

[0033] Figure 4 An example of a silo 5 is shown, which allows the grinding discs 11 to be automatically mounted on the grinding machine 10. The silo 5 includes a frame or housing 50. In the example shown, a support plate 53 is movably supported in the housing. In the housing 50, the stack of grinding discs 11 is located on the support plate 53. A linear actuator 51 is connected to the support plate 53. The linear actuator is formed to push the support plate 53 and the stack of grinding discs upward. In the example shown, the actuator 51 is also located below the support plate 53 in the housing 50. The actuator 51 can be a pneumatic actuator, such as a cylinder. However, other types of linear actuators can also be used, such as a bellows cylinder or a direct electric drive. The actuator 51 can also include a combination of an active drive and a (passive) spring.

[0034] In the example shown, a retainer ring 52 is arranged at the top surface of the housing 50 so that the actuator 51 presses the stack of grinding discs 11 against the bottom surface of the retainer ring 52. The actuator force F of the linear actuator 51 pressing the topmost grinding disc against the retainer ring 52 is AFor this purpose, the actuator 51 is coupled to a controller 59 which can set the force applied by the actuator to the support plate 53. The manner and purpose of force regulation by the controller 59 will be explained in detail later.

[0035] Figure 5 Shown Figure 4 An example of a retaining ring 52 for a silo 5 is shown. The maximum inner diameter of the retaining ring 52 is denoted by R1, while the outer diameter of the grinding disk 11 is denoted by R2. The inner diameter R1 of the retaining ring 52 is greater than the outer diameter R2 of the stack of grinding disks (R1>R2). To prevent the actuator 51 from pushing the grinding disks out of the silo, the retaining ring 52 has one or more protrusions 52a-d that extend beyond (overlap) the edge of the topmost grinding disk in the stack. That is, the protrusions 52a-d point inward (toward the center point of the retaining ring 52).

[0036] The force of the actuator 51 is controlled by means of a controller 59. In other words, the force required to press the topmost grinding disc with its rear face upward against the projections 52a-d of the retaining ring 52 is adjustable (e.g., 50 Newtons). In the case of a pneumatic actuator, the force can be controlled in a manner known per se using a regulating valve (not shown), a regulator (implemented in the controller 59), and a compressed air reservoir (not shown). However, the specific implementation of the force control is not essential for the further explanation and will therefore not be discussed in detail at this point.

[0037] Figure 4 The silo 5 filled with grinding discs is shown in an initial state, in which the actuator 51 is moving with a defined (regulated) force F A =F A1 The grinding disc stack is brought upwards against the retaining ring 52. During operation of the silo (after filling with grinding discs), the topmost grinding disc of the stack contacts the retaining ring 52, i.e. the grinding disc stack is not lowered between two successive installation processes and the silo 5 remains ready for use without the need to raise the grinding disc stack before each filling process (installation process).

[0038] At the start of the loading process, the robot positions the grinder 10 above the hopper so that the carrier plate 12 of the grinding discs is substantially coaxial with the stack of abrasive discs. In other words, the carrier plate 12 of the grinder 10 is positioned centrally above the stack of abrasive discs and is positioned substantially parallel to the retaining ring 52 and then bears against the top surface of the retaining ring with less force. Because the stack of abrasive discs is actively pressed upward (by the actuator 51), the back side of the topmost abrasive disc 11 contacts the bottom surface of the carrier plate 12. As a result, the back side of the topmost abrasive disc 11 adheres to the bottom surface of the carrier plate 12 because the two corresponding surfaces are composed of materials that together form a hook-and-loop fastener, for example. As mentioned, other connection techniques can also be used.

[0039] In particular when using hook and loop fasteners, it may be advantageous if the robot slightly reciprocates the carrier plate 12 parallel to the retaining ring 52 while the carrier plate 12 contacts the uppermost grinding disc. This slight movement causes the loops and hooks of the hook and loop fastener to be firmly connected (hooked to each other). Figure 6 The arrow represents the actuator force F of the actuator 51. A , the pressing action of the grinder against the top surface of the retaining ring 52 and the mentioned movement in the lateral direction.

[0040] exist Figure 6 During the installation process shown in A1 The top grinding disc of the stack must be relatively high so that the top grinding disc of the stack is slightly "oozed out" of the retaining ring 52 and the grinding disc 11 is well attached to the carrier disc. By pressing the grinding disc stack, the top grinding disc of the stack is pressed against the bottom surface of the retaining element 52 (for the projections 52a-d, see Figure 5 ) is clamped. This clamping can sometimes lead to the connection between the carrier plate 12 and the grinding discs 11 being released again when the grinder 10 is lifted from the silo and the installation process failing. Therefore, in some systems, the stack of grinding discs is lowered after the installation process in order to release the aforementioned clamping. However, this lowering has the disadvantage that the grinding discs rub along their periphery against the inside of the frame / housing 50 or other components in the housing interior and cause wear. However, according to the embodiment described herein, the actuator 51 operates in a force-regulated manner, so that the actuator force F can be adjusted before the grinder is lifted from the silo. A From F A1 Reduce to F A0 (F A0 <F A1 ) in order to significantly reduce the clamping effect and enable the grinding discs to be simply “pulled out” from the hopper 5 without having to lower the grinding disc stack (i.e. the grinding disc stack is in full contact with the bottom surface of the retaining ring). AIncrease again to the rated value F A1 , and the silo is immediately ready for the next installation process. Figure 7 The support plate 53 is only lowered (ie the force control is switched off or the actuator force is reduced to zero) in order to fill the silo 5 with new grinding discs.

[0041] The following will refer to Figure 8 The above process is summarized in the flowchart in FIG. A1 The grinding disc stack in the silo 4 is brought against the retaining ring 52 ( Figure 8 , step S1), and the silo is ready for a new installation process. The robot positions the grinder 10 (approximately coaxially with the retaining ring 52) above the silo 5 ( Figure 8 , step S2). Then the carrier plate of the grinding machine (for example, by actuator 20, see Figure 3 ) against the retaining ring 52 ( Figure 8 , step S3) and the top grinding disc of the stack is attached to the carrier plate, for example, by means of a hook and loop fastener. Before the grinder 10 is lifted from the silo, the controller 59 (see Figure 4 ) obtains a signal (e.g. a signal from the robot controller 4, see Figure 1 ), said signal representing the actuator force F generated by the actuator 51 A should decrease, and the actuator 51 will therefore change the force applied to the grinding disc stack from F to A1 Reduce to F A0 ( Figure 8 , step S4). Then, the grinder 10 is lifted away from the silo 5 and the installed grinding disc is pulled out of the silo ( Figure 8 , step S5).

[0042] Figure 9 Another aspect of the concept described herein for improving the accuracy of force regulation is shown, in which the weight of the grinding disc stack is taken into account. First the actuator 51 first forces the grinding disc stack against the back side of the retaining ring 52 ( Figure 9 , step S1.1). The actuator deflection (actuator position) depends on the number of grinding discs in the silo. The fewer grinding discs a stack has, the further the actuator 51 needs to deflect the support plate 53 upwards. The actuator deflection can be measured, and the controller 59 can calculate the weight of the grinding disc stack ( Figure 9, step S1.2). For example, the number of grinding discs in the silo can be calculated from the actuator deflection and the known thickness of the grinding discs. Since the weight of the individual grinding discs is known, the total weight of the stack of grinding discs can be determined from the known number. Alternatively, the density of the grinding disc material (for example, grinding felt) (weight per unit height of the stack) can also be stored in the controller, so that the controller 59 can simply calculate the weight of the stack currently in the silo from the density and the actuator deflection. Subsequently, when setting the actuator force F A The gravity of the stack can be taken into account ( Figure 9 , step S1.2).

[0043] If, for example, the weight of the grinding disc stack is known to be 10 Newtons, the actuator force F A It is set to 40 Newtons (rated force plus gravity) to effectively use 30 Newtons to force the top grinding disc against the retaining ring 52. This prevents the actuator force (especially the value F) from being too high when there are only a few grinding discs in the hopper 5. A0 ) becomes too large. If, for example, the gravity force is only 2 Newtons, the actuator force F A Reduce to 32 Newtons to continue with 30 Newtons to force the top grinding disc against the retaining ring 52. Without taking gravity into account, this force will be too large.

[0044] Figure 10 A pulling device 6 is shown for automatically pulling a grinding disc from a carrier plate of a grinding machine. In the example shown, the pulling device has a housing 60 with a clamping mechanism 62. The housing 60 is not necessarily closed and can also be formed by a frame (open housing) or the like. The clamping mechanism 62 is formed by clamping jaws 622 and 623, which are arranged in a clamping direction (in the direction of the clamping direction). Figure 10 The clamping jaws 623 are part of a plate arranged on the top surface of the housing 60, and the clamping jaws 622 are movably supported in or in the housing in the clamping direction (for example, by means of a linear guide) and can be moved by means of a linear actuator 61. In other words, the linear actuator 61 is formed to close or release the clamping mechanism (along the clamping direction). The clamping edge ( Figure 10 The left side of the clamping jaw 622 is flush with the corresponding edge of the clamping jaw 623 in the clamping direction. The actuator 61 can be any linear actuator, such as a cylinder, an electric linear actuator, etc.

[0045] On the side of the housing 60 where the clamping jaws 622, 623 are located, a support element 64 is arranged, which has a convexly curved outer contour on its outer side (the side facing away from the housing). Before the pulling process, the clamping device 62 is opened. The robot positions the grinder with the (worn) grinding wheel 11 in front of the support element 64 at an angle (relative to the vertical clamping direction, for example) and then places the grinding wheel against a part of the curved surface of the support element 64. The orientation of the grinder 10 is Figure 10 This is also shown by an arrow (labeled with the text "positioning"). In the example shown, the axis of rotation of the grinding machine is inclined at about 45° relative to the clamping direction. It should be understood that the clamping direction does not necessarily extend in the vertical direction, but also depends on the inclination of the grinding machine relative to the clamping direction. Figure 10 Based on the situation shown in FIG, the clamping device 62 can be closed by means of the actuator 61 in order to clamp the grinding wheel 11 at the edge.

[0046] The actuator may have a sensor for detecting the final position (e.g. a final position switch). If the actuator 61 advances to its final position when the clamping mechanism is closed, this indicates that the grinding disc 11 has been incorrectly clamped between the clamping jaws 622 and 623. Figure 11 The situation shown in FIG is that the grinding disc 11 is correctly clamped between the clamping jaws 622 and 623 and the actuator 61 has therefore not reached its final position. In addition to the clamping mechanism 62 being closed, Figure 11 and Figure 10 same.

[0047] The inclination of the grinding machine solves several problems that can arise with known designs. According to a known solution (see US Patent Publication No. 8,517,799 B2), to release the grinding wheel, a spacer is pushed between the carrier plate 12 and the grinding wheel 11, parallel to the surface of the carrier plate 12. However, this method of use only works when the thickness of the grinding wheel, especially the grinding paper, is known. However, the thickness of the grinding wheel is not always uniform and can vary greatly (especially when relatively thick grinding felt discs become thinner due to grinding, so that the thickness of the worn disc can vary greatly from case to case). According to another solution, the (worn) grinding wheel is placed against a flat support surface (parallel to the carrier plate 12) and clamped against the support surface with clamping jaws. In this case, the clamping direction (without tilt) is parallel to the rotation axis of the grinding machine. This method of use only works when the grinding wheel is slightly adjacent to the carrier plate, which is often the case when using emery cloth (so-called daisy discs).

[0048] The concept described here also works reliably even when the actual thickness of the grinding disc is unknown and the grinding disc does not protrude beyond the carrier plate. The grinding disc can even have a slightly smaller diameter than the carrier plate 12 of the grinding machine. Figure 11 It can be easily seen that, due to the inclination, the lower edge (at the periphery of the grinding wheel) is between the jaws 622 and 623 even when the grinding wheel 11 is not larger (or even slightly smaller) than the carrier plate 12 mounted on the grinding wheel 11.

[0049] Depend on Figure 11 Starting from the situation shown in , the robot moves the grinding machine 10 in such a way that the carrier plate 12 performs a rolling motion on the convexly curved surface of the support element 64, while the actuator 20 (with a small force) presses the carrier plate 12 against the support surface 64. During the rolling motion, the grinding machine 10 rotates (rolls) away from the clamping mechanism. Figure 12 、 13 , 14 and 15 illustrate the rolling motion with a number of intermediate steps. This rolling motion reduces the tensile forces in the grinding disc in the clamping area and prevents the grinding disc 11 from being torn out of the clamping mechanism 62 again before the grinding disc has completely detached from the carrier disc 12.

[0050] As in Figure 12 、 13 As can be seen in Figures 14 and 15, during the rolling motion, the flexible grinding disc 11 contacts the curved surface of the support surface 64, which results in relatively high friction (similar to winding a cable around a bollard). This friction prevents the load when pulling out the grinding disc from being fully introduced into the clamping mechanism. In this way, the grinding disc 11 can be reliably prevented from being torn out of the clamping device 62 during the pulling process. During the rolling motion of the grinder, the grinding disc 11 gradually detaches from the carrier plate 12 (for example, the hook and loop fastener is separated). Figure 15 The situation shown in shows the end point of the tumbling movement, at which only a small part of the grinding wheel 11 remains attached to the carrier plate.

[0051] from Figure 15 Starting from the situation shown in FIG, the robot can pull back the grinding machine 10 so that the carrier plate 12 is lifted off the surface of the support element 64, thereby detaching the part of the carrier plate 12 that is still attached to the grinding wheel 11. The actuator 61 can then be controlled so that the clamping mechanism 62 is opened again and the grinding wheel 11 falls (for example into a collection container). The signal for closing and clamping the clamping device can be generated, for example, by the robot controller (see FIG. Figure 1 , robot controller 4).

[0052] The following will use Figure 17 The process of pulling out is summarized in the flowchart shown in Figure 17The robot positions the grinding machine 10 and the grinding disc 11 at the convexly curved placement element 64 of the clamping mechanism 62 ( Figure 17 , step R1), wherein the grinding machine 10 is positioned obliquely relative to the clamping direction of the clamping mechanism 62 so that the edge at the periphery of the grinding disc 11 can be clamped by the clamping device 62. The grinding disc 62 is then clamped at the edge ( Figure 17 , step R2, activating the clamping mechanism). Subsequently, the robot controls the rolling motion of the grinding machine 10 on the placement element 64, while the carrier plate 12 abuts against the surface of the curved placement element 64 ( Figure 17 , step R3). Finally, the robot pulls the grinding machine 10 back from the placement element 64 ( Figure 17 , step R4), thereby finally separating the grinding disc 11 from the carrier plate 12. The clamping mechanism 62 can then be released ( Figure 17 , step R5) and the grinding disc 11 can fall (for example from the pull-out device into a collecting container).

[0053] It should be understood that according to Figure 10 Pull-out equipment and according to Figure 4 The silos can be combined into a replacement station. It is clear from the above description that a person skilled in the art can supplement or modify the described embodiments in order to create further embodiments without changing the concepts underlying these embodiments. Figure 10 The pull-out device can be mounted displaceably in the (for example horizontal) direction and fixed by means of a spring, so that when the robot places the grinder and the grinding disc on the convexly curved placement element, the pull-out device can be deflected against the spring force. Figure 18 As shown in the figure, Figure 10 Very generally speaking, the robot arm positions the grinding machine so that the edge of the carrier plate 12 is as close as possible to the clamping device (however, only the grinding felt extends into the clamping device), so that when the clamping device is closed, the clamping jaws 622 and 623 grip the grinding felt as close as possible to the edge of the carrier plate 12 (see Figure 18 , the spacing a is as small as possible, theoretically zero).

[0054] From Figure 4 The hopper can also be supported movably in the vertical direction against the force of a spring, so that the entire hopper is retracted when the robot puts the grinder and the carrier plate onto the hopper. This variant can be advantageous when the grinder is directly connected to the end effector of the robot (excluding the actuator 20). In some applications, the actuator 20 can be omitted (see FIG. Figure 1) or the actuator 20 can be replaced by a passive spring. After removing the grinding disc from the carrier plate, it can be verified by visual inspection (for example with the aid of a camera) that the grinding disc has actually been completely removed. Visual inspection can also be used to verify whether the grinding disc is correctly attached to the carrier plate after the installation process.

[0055] It is subsequently noted that polishing is considered a special case of grinding and therefore everything that has been stated with respect to grinding machines or grinding processes also applies to polishing machines and polishing processes.

Claims

1. A method for removing an abrasive article (11) from a robot-assisted abrading machine (10), the method comprising: Positioning the grinding machine (10) on a curved placement element (64) of the pull-out device (6) near a clamping mechanism (62) of the pull-out device (6) by means of a robot arm (1); clamping the abrasive member (11) by closing the clamping device (62); performing a rolling movement of the grinding machine (10) by means of the robot arm (1), while the grinding element (10) contacts the curved support element (64), thereby partially detaching the grinding element (11) from the carrier plate (12) of the grinding machine (10); Pulling back the grinding machine (10) by means of the robot arm (1) so that the grinding piece (11) is completely separated from the carrier plate (12); and Release the clamping mechanism (62).

2. The method according to claim 1, wherein When the grinding machine (10) is placed on the curved placement element (64), the rotation axis of the grinding machine (12) is tilted relative to the clamping direction of the clamping mechanism (62).

3. The method of claim 2, wherein the inclination is in the range of approximately 30 to 60 degrees.

4. The method according to any one of claims 1 to 3, wherein: The clamping mechanism (62) is closed in a vertical direction, and wherein the grinder is positioned obliquely relative to the vertical direction.

5. The method according to claim 1 , wherein the grinding machine ( 10 ) is positioned such that the edge of the carrier plate ( 12 ) is positioned as close as possible to the clamping mechanism ( 62 ) and the grinding element ( 11 ) extends into the clamping mechanism ( 62 ).

6. A method according to one of claims 1 to 5, wherein the placement element (64) is convexly curved and the grinding piece (11) is clamped between the placement element (64) and the carrier plate (12) during the rolling movement, while being retained on one side by the clamping mechanism.

7. Method according to one of claims 1 to 6, wherein the pull-out device (6) is linearly movable against the action of a spring force, in particular linearly movable in the horizontal direction.

8. A method for automatically mounting grinding elements (11) provided in a hopper (5) onto a carrier plate (12) of a robot-assisted grinding machine (10), the method comprising: The grinding element (11) is pressed against the back side of the retaining ring (52) by means of a linear actuator (51), wherein the linear actuator (51) is force-regulated and acts with a defined pressing force (F A =F A1 ) causing the grinding element (11) to abut against the retaining ring (52); Positioning the grinding machine (10) above the hopper (5) with the aid of a robot arm (1) and placing the carrier plate (12) of the grinding machine (10) against the top surface of the retaining ring (52), thereby attaching the grinding element (11) to the carrier plate (12); The pressing force is reduced from a first value to a second, lower value (F A =F A0 ); and subsequently The grinding machine (10) is pulled back from the silo by means of the robot arm (1), thereby pulling the grinding element (11) attached to the carrier plate (12) out of the silo through the retaining ring (52).

9. The method according to claim 8, further comprising the step of increasing the pressing force to the first value (F A =F A1 ).

10. Method according to claim 8 or 9, wherein the abrasive element (11) is attached to the carrier plate by means of an adhesive layer or a magnetic fastener or a hook and loop fastener.

11. Method according to one of claims 8 to 10, wherein the grinding machine (10) is subjected to an oscillating movement parallel to the retaining ring (52) by means of the robot arm (1) while the carrier plate (12) is brought into contact with the retaining ring (52).

12. Method according to any one of claims 8 to 11, wherein the grinding element (11) is the topmost grinding element in a stack of grinding elements, the stack of grinding elements being arranged on a support plate (53) in the silo.

13. Method according to claim 12, wherein the linear actuator (51) pushes the support plate (53) upwards in the direction of the retaining ring (52) and the stack of grinding elements does not repeatedly rise and fall during operation.

14. A pulling device (6) for removing an abrasive article (11) from a robot-assisted abrading machine (10), the device comprising: a curved support element (64) for a grinding element (11) mounted on a carrier plate (12) of the grinding machine (10); A clamping mechanism is formed to clamp the grinding member (11) by closing the clamping mechanism (62) in a clamping direction while the grinding member is positioned on the curved placement element (64) at an angle relative to the clamping direction.

15. A device for automatically mounting grinding elements (11) provided in a hopper (5) onto a carrier plate (12) of a robot-assisted grinding machine (10), the device comprising: The silo (5) is formed for receiving a stack of the abrasive elements (11), wherein the silo has a retaining ring (52); a linear actuator (51) formed to abut the stack of abrasive elements (11) against the retaining ring (52); A controller (59) for the linear actuator, the controller being configured to set a pressing force for pressing the stack of abrasive elements (11) against the retaining ring (52) such that the pressing force is a defined first value (F A =F A1 ), The controller (59) is configured to reduce the pressing force from the first value to a lower second value (F A =F A0 ) while the stack of abrasive elements (11) is brought further against the retaining ring (52) so that the top abrasive element in the stack can be easily pulled out.

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