MACHINING SYSTEM FOR WORKPIECE MACHINING

A machining system for workpiece machining includes a machining cell, to which a workpiece holder for fixing a workpiece, a machining head for machining the workpiece and a robot for workpiece cleaning are assigned, wherein the robot has an articulated robot arm which is mounted with an initial section on a machine frame connected to the machining cell and which is provided at an end section remote from the initial section with a nozzle, which is designed to provide a jet of compressed air, a joint being arranged between the initial section and the end section, wherein the joint is provided with a pneumatic drive for providing a relative movement between the initial section and the end section.

BACKGROUND OF THE INVENTION

The invention relates to a machining system for workpiece machining with a machining cell, to which a workpiece holder for fixing a workpiece, a machining head for machining the workpiece and a robot for workpiece cleaning are assigned, wherein the robot has an articulated robot arm, which is attached with an initial section to a machine frame connected to the machining cell and which is equipped at an end section facing away from the initial section with a nozzle, which is designed to provide a jet of compressed air, wherein a joint is arranged between the initial section and the end section.

From EP 1 004 393 B1 it is known to perform an automatic tool change on at least one machine tool with a robot serving as a tool changer and having at least six axes. Here, in addition to its task as a tool changer, the robot can also be programmed and used for the targeted blowing off of drill holes.

SUMMARY OF THE INVENTION

The task of the invention is to provide a machining system in which workpiece cleaning can be performed at low cost.

This task is solved for a machining system of the type mentioned above in that the joint is provided with a pneumatic drive for providing a relative movement between the initial section, which also may be named a base section, and the end section. By using a pneumatic drive, a compact design of the joint is possible. Furthermore, the pneumatic drive enables the use of compressed air as an energy carrier, which must be provided anyway for carrying out cleaning operations for the workpiece. Apart from the fact that the use of compressed air avoids the need to provide different power sources for the operation of the robot, the use of compressed air as an energy carrier for the robot also is advantageous with respect to explosion protection, depending on the cleaning task to be performed. These properties are of particular interest if the machining system is used to perform machining operations in which ignitable mixtures may occur in the machining cell, as may be the case when performing 3D printing processes, for example.

The pneumatic drive can be designed, for example, as a pneumatic cylinder or as a compressed air motor with gear arrangement or as a pneumatic direct drive, in particular as a pneumatic swivel drive, and enables a relative movement for the joint. This relative movement is typically a pivoting movement of the end section with respect to the initial section about a single pivot axis defined by the respective joint. If necessary, it can also be provided that the pneumatic drive is designed for a spatial pivoting movement about several pivot axes and/or for a superimposed translational movement.

Preferably, it is provided that the robot arm comprises a plurality of joints which are arranged between the initial region and the end region and can each be operated individually, so that the nozzle attached to the end region can be brought into the most favorable spatial orientation with respect to the workpiece as a function of a geometry of the workpiece to be cleaned.

Advantageous further embodiments of the invention are the subject of the subclaims.

It is expedient if the machine frame is arranged in the machining cell and if the workpiece holder and/or the machining head are coupled to the machine frame. In this embodiment of the machining system, the robot can perform a cleaning of the workpiece before and/or during and/or after the machining of the workpiece by the at least one machining head. In this case, it is particularly advantageous if the robot is reliably protected against influences such as may be present in the machining cell during and/or after the execution of the machining operation. Such protection is already promoted due to the design characteristics of the pneumatic drive as used for the at least one joint, since an airtight connection between the components of the pneumatic drive that are movable relative to one another is required anyway for proper functioning of the pneumatic drive. Furthermore, it can be assumed that in the event of a malfunction or the occurrence of signs of wear, at most a leakage of compressed air from the pneumatic drive into the machining cell will occur. In the event of such a leakage of compressed air, no danger to the machining process is caused, and in addition, ignition of any ignitable mixture present in the machining cell by the escaping compressed air can also be ruled out.

Preferably, it is provided that the machine frame is arranged outside the machining cell and has a workpiece changing station, and that the initial section of the robot arm is arranged above the workpiece changing station on the machine frame. In this embodiment, the robot can be used to clean workpieces delivered from a previous processing station at the workpiece changing station prior to processing in the machining cell and/or to clean workpieces that have been processed in the machining cell at the workpiece changing station prior to further transport. The advantage here is that the cleaning process can be carried out independently of the machining that is taking place in the machining cell, so that the cleaning does not cause any time delay for the machining of the workpiece in the machining cell. Mounting the robot arm above the workpiece changing station allows good use of space for the machining system, since no additional floor space is required for the robot. By using pneumatic drives for the robot's joints, the robot can be realized with a low overall mass and can be designed and operated in such a way that the robot does not pose a hazard to a user, even when the user is present close to the workpiece changing station.

In a further embodiment of the invention, it is provided that the robot is assigned an electronic control which is designed for actuating a first valve module which is connected to the pneumatic drive and for actuating a second valve module which is connected to the nozzle, and that the joint is assigned a sensors system for detecting a joint position, which sensor system is designed for providing a sensor signal to the electronic control, the electronic control being designed for controlled actuation of the first valve module using the sensor signal. Preferably, the electronic control is or comprises a microcontroller or microprocessor on which a computer program runs, with the aid of which the desired cleaning process for the workpiece can be carried out. For this purpose, the electronic control controls a first valve module, which is connected to the pneumatic drive, or a plurality of first valve modules, each of which is connected to a pneumatic drive, in order to achieve a desired spatial orientation of the end section of the robot arm with respect to the workpiece. Here, the electronic control uses sensor signals from at least one sensor system designed to detect the joint position of the at least one joint and performs a position control (closed loop) for the respective joint by correspondingly actuating the first valve module. Furthermore, the electronic control is designed for actuating a second valve module which is provided for influencing a compressed air flow to the nozzle, the electronic control preferably influencing the compressed air flow provided by the second valve module to the nozzle as a function of the spatial orientation of the nozzle.

In a further embodiment of the invention, it is provided that the first valve module is arranged on the joint and the second valve module is arranged on the machine frame or that the first valve module and the second valve module are arranged on the machine frame. If the first valve module is arranged on the joint or in the immediate vicinity of the joint, it is advantageous that the fluid lines between the first valve module and the pneumatic drive can be kept very short, which supports a spontaneous response of the pneumatic drive to a change in the valve positions of the first valve module. However, in this case it is necessary to run electrical control lines, which run between the electronic control of the first valve module, from the initial section of the robot arm to the respective first valve module. The attachment of the second valve module to the machine frame, in particular in the vicinity of the initial section of the robot arm, is advantageous because the nozzle requires a high mass flow of compressed air and therefore the second valve module must be sufficiently large. Therefore it is advantageous if the second valve module is mounted directly to the machine frame. In an alternative embodiment, it is provided that both the first valve module and the second valve module are mounted to the machine frame. In this case, it is advantageous that apart from fluid lines for connecting the at least one first valve module to the at least one pneumatic actuator and a fluid line for connecting the second valve module to the nozzle, only at least one sensor line from the sensor system associated with the at least one joint has to be routed along the robot arm. In particular, this minimizes the risk of electrical sparking, which means that the robot can also be used in ambient conditions that are subject to the requirements of explosion protection.

Advantageously, the electronic control is associated with a human machine interface configured to be triggered by a user, wherein the electronic control is configured to store a joint position upon receipt of a trigger signal provided by the human machine interface. The human machine interface can be used by a user to store a spatial orientation of the robot in order to establish a path of motion for the robot and nozzle assembly attached thereto as part of a learning process for the electronic control. Such a process is also referred to as “teaching”.

The human machine interface may be located remote from the robot and is in electrical communication with the electronic control. Exemplarily, the human machine interface may be designed as a camera with downstream electronic image processing to store the respective spatial orientation of the robot based on predetermined movements or gestures of the user. Alternatively, the human machine interface can be attached to the surface of the robot, in particular in the immediate vicinity of the nozzle, and can be designed as a pushbutton switch. In this case, the user can bring the robot arm and the nozzle attached thereto stepwise into spatial orientations which are advantageous for the intended cleaning of the workpiece and, when the respective spatial orientation is reached, actuate the human machine interface in order to store this spatial orientation in the electronic control. After completion of the teach-in process, the task of the electronic control is to determine a movement path for the robot arm from the taught-in spatial orientations and then to execute this path by controlling the valve modules accordingly. Depending on the design of the nozzle, it can be provided that the human machine interface also enables a selection of a configuration of the nozzle, for example with regard to the question of which of a plurality of nozzles should be used in the respective spatial orientation of the robot arm or whether, if necessary, no compressed air should be supplied to the nozzle in the specific spatial orientation of the robot arm.

For this purpose, it is particularly advantageous if the human machine interface is arranged at the end section of the robot arm, preferably in the area of the nozzle, and if the electronic control is designed to distinguish between at least two trigger signals of the human machine interface. The arrangement of the human machine interface on the end section of the robot arm makes it possible to ensure particularly intuitive operation of the robot during the teach-in process. A distinction between at least two trigger signals of the input device makes it possible to distinguish between a determination of a spatial orientation of the robot arm and a determination of a start or end of a compressed air supply process for the nozzle. By way of example, it can be provided that a short actuation of the input device serves to define the spatial orientation of the robot arm and a long actuation of the input device influences the compressed air supply.

In an advantageous further embodiment of the invention, it is provided that the nozzle is designed as a compressed air nozzle with an adjustable jet cross-section or is designed as a set of compressed air nozzles from the group: point jet nozzle, fan nozzle, deflection nozzle, with different jet cross-sections. A design of the nozzle as a compressed air nozzle with adjustable jet cross-section can be provided, for example, in such a way that the jet cross-section of the compressed air jet emerging from the nozzle is in a predetermined dependence on a supply pressure which is provided by the second valve module. In this case, the second valve module can be designed as a proportional valve arrangement. Alternatively, an adjustment of the jet cross-section can be provided by an electric or pneumatic actuator acting on the nozzle. In an alternative embodiment, the nozzle includes a set of several compressed air nozzles with different geometries, which can be supplied with compressed air individually or in parallel depending on the requirements for cleaning the workpiece. In this case, it can be provided that a third valve module, which is designed for switching between the different compressed air nozzles, is arranged in the immediate vicinity of the nozzle and can be electrically controlled by the electronic control.

In a further embodiment of the invention, it is provided that the robot arm is surrounded by a, preferably two-layer, protective hose made of flexible, in particular elastic, material. The task of the protective hose is to protect the at least one joint and the at least one pneumatic drive from contamination, such as may be present in the machining cell and/or may occur during cleaning of the workpiece. To enable cost-effective manufacture of the protective hose, the latter is made of a flexible material, in particular a textile material such as a woven fabric. It is advantageous if the flexible material is also elastic so as not to offer a significant resistance to the movements of the robot arm. It is particularly advantageous if the protective hose is made in multiple layers from at least two different materials. In this case, an inner tube can be designed in such a way that it has the lowest possible sliding friction with respect to the robot arm and the outer tube arranged coaxially with the inner tube, in the manner of an inner lining of a garment. In this case, the outer hose is used to ensure that the robot arm is sealed off from environmental influences and can preferably be designed to be waterproof and/or dustproof within a predefined range of use.

Preferably, it is provided that a compressed air inlet for providing an overpressure with respect to an environment of the robot arm is assigned to a spatial volume delimited by the protective hose. This measure can ensure that no undesirable ingress of contamination occurs even at interfaces between the protective hose and the robot arm, the tightness of which is often difficult to guarantee.

DETAILED DESCRIPTION

A machining system1shown purely schematically inFIG. 1is designed as a milling center and enables a workpiece2to be machined. For this purpose, the machining system1comprises a box-shaped machine frame3, to which a robot4, a machining head5, a workpiece carrier plate6and a workpiece lock7are attached.

The machine frame3, which is shown only schematically, is provided with planking on all side surfaces in a manner not shown in greater detail, so that a spatial section is formed which is sealed off from an environment of the machining system1and which can also be referred to as a machining cell8.

The robot4has a base-like initial section21that is fixedly attached to an upper surface of the machine frame3. Connected to the initial section21is a robot arm22which, purely by way of example, comprises a first arm part28, a second arm part29, a third arm part30and a fourth arm part31, as well as associated joints33,34,35and36for the articulated connection of respectively adjacently arranged arm parts28,29,30and31. In this case, the fourth arm part31forms, purely by way of example, the end section of the robot arm22and is provided at the end with a nozzle23. For reasons of clarity, all joints33to36are shown in the drawing in such a way that their swivel axes37are aligned normal to the plane of representation ofFIG. 1. In practice, the swivel axes of the joints33to36can be arranged in different spatial orientations relative to one another.

Starting from the initial section21up to the nozzle23, the robot arm22is surrounded by a protective hose40which is designed to seal off the robot arm22from environmental influences such as may be present in the machining cell8. By way of example, the protective hose40has two layers and comprises an inner hose41and an outer hose42.

Associated with the initial section21of the robot4are a source of compressed air24, a source of electrical power25, and a fluid outlet26provided with a muffler. Furthermore, an electronic control27and a second valve module, the function of which will be described in more detail below, are accommodated in the initial section21.

The machining head5is connected to the machine frame3via a multi-axis manipulator50, which is configured to allow a milling tool53to move in three dimensions in order to allow the workpiece2to be machined as completely as possible. A supply of cooling lubricant from the machining head5to the milling tool51may be provided for carrying out a workpiece machining operation. In any case, the machining of the workpiece2results in a contamination of the workpiece2by chips which are to be removed before further transport of the workpiece2by means of the robot4.

By way of example, it is provided that a conveyor, which is not shown, is integrated in the workpiece carrier plate6, which is only shown schematically, and which conveyor is designed for a movement of the workpiece2between a workpiece holder51arranged below the machining head5and a workpiece changing station52arranged below the robot4. The conveyor enables a rapid exchange of workpieces2between the workpiece changing station52and the workpiece holder51, whereby a simultaneous machining of a workpiece2with the machining head5as well as a cleaning of a further workpiece2can preferably be carried out with the robot4.

Purely by way of example, the machining cell8is divided by a workpiece lock7into a working area, in which the machining head5and the workpiece holder51are arranged, and into a changing area, in which the robot4and the workpiece changing station52are arranged. The workpiece lock7can be opened for the exchange of workpieces2and is closed during the machining of the workpiece2or the cleaning of the workpiece2. InFIGS. 2 and 3, the joint36arranged between the third arm part30and the fourth arm part31is shown from two opposite spatial directions. The joint36is representative of the other joints33to35, which are preferably of the same type, in particular identical, as the joint36.

Purely exemplarily, the joint36which is arranged between the third arm part30and the fourth arm part31also includes the pneumatic drive43, which is designed as a pneumatic swivel drive and which enables a limited swivel movement between the third arm part30and the fourth arm part31about the swivel axis37aligned normal to the plane of representation ofFIGS. 2 and 3.

By way of example, the pneumatic actuator43comprises an annular actuator housing44extending along the pivot axis37and having an outer surface connected to the third arm portion30.

As can be seen from the illustration ofFIG. 3, a drive shaft45is rotatably mounted in the drive housing44, which is connected to the fourth arm part31and which determines the pivot axis37. Fixed to the drive shaft45is a sealing sleeve47which carries a working vane46extending outwardly in the radial direction. The working vane46, together with the undesignated inner surface of the drive housing44and a sealing ridge48of the drive housing44projecting inwardly in the radial direction, defines a first working chamber55and a second working chamber56. In this regard, the working vane46and the sealing sleeve47are pivotally sealingly received in the drive housing44, thereby allowing the volume of the first working chamber55and the second working chamber56to be varied.

A fluid connection57,58is associated with each of the working chambers55,56, via which a supply and discharge of compressed air into and out of the respective working chamber55resp.56from the respective working chamber55or56can be carried out. In the presence of a pressure difference between a first fluid pressure in the first working chamber55and a second fluid pressure in the second working chamber56, there is a resulting force effect on the working vane46, which leads to a torque on the drive shaft45, whereby a pivoting movement of the fourth portion31relative to the third arm portion30can be caused.

A compressed air supply and a compressed air discharge for the first working chamber55are provided via a first fluid line63connected to the first fluid port57and connected to a first control valve59and a second control valve60. In a purely exemplary manner, the first control valve59is provided as a venting valve and controls a fluid flow from the compressed air source24into the first working chamber55. In an exemplary embodiment, the second control valve60is provided as a venting valve and allows venting of the first working chamber55via the fluid outlet26. Similarly, the second working chamber56is connected via a second fluid line64to a third control valve61and a fourth control valve62, by means of which it is also possible to pressurize or vent the second working chamber56. The control valves59to62are fluidically connected to the compressed air source24and the fluid outlet26, respectively, depending on their assigned task. The control valves59to62are fluidically connected to the compressed air source24or the fluid outlet26, depending on their assigned task, and are electrically connected to a valve control15mounted directly on the third arm part30, which is also referred to as the first valve module. Depending on the design of the control valves59to62, which can be selected, for example, from the group: switching valves, proportional valves, the valve control15is set up to control the control valves59to62as required depending on control signals which are provided by the electronic control27via a control line16. Furthermore, the valve control15is connected to the compressed air source24via a compressed air line38and to the fluid outlet26via an outlet line39and can thus influence compressed air flows to the pneumatic drive43or from the pneumatic drive43.

Furthermore, according to the representation ofFIG. 2, it is provided that a sensor system17is arranged in the drive housing44, which comprises an encoding disk18connected to the drive shaft45in a rotationally fixed manner and a sensor19, wherein the sensor19is electrically connected to the valve control15via a sensor line20. By way of example, the coding disk18has an optically or magnetically scannable incremental or absolute coding arranged in an annular manner coaxially with the pivot axis37, which is scanned by the sensor19. The sensor19provides a sensor signal, dependent on the result of the scanning, to the valve control15via the sensor line20. Depending on the design of the valve control15as well as the electronic control27, it may be provided that a control of a swivel position is performed by the valve control15. In this case, a swivel angle information for the fourth joint36is provided by the electronic control27. Alternatively, it can be provided that the sensor signal of the sensor19is forwarded to the electronic control27without intermediate processing in the valve control15, where a comparison is made between a stored setpoint value and an actual value for the pivoting position of the fourth joint36. From any deviation between the setpoint value and the actual value, the electronic control27then determines suitable control signals which are transmitted to the valve control15and are converted there into corresponding valve control signals for the control valves59to62.

A pneumatic supply to the nozzle23, which is arranged at the end of the fourth arm part31, is provided via a fluid supply line65which, starting from the second valve module12, which is accommodated purely exemplarily in the initial section21and which is connected to the compressed air source24, extends to the end of the fourth arm part31and is connected there to a fluid connection66of the nozzle23.

Furthermore, a human machine interface9is associated with the fourth arm portion31, which human machine interface is designed, for example, as an electrical push-button switch and which is connected to the electronic control27via an electrical line which is not shown. The human machine interface9makes it possible, for example, to store joint positions of the joints33to36which the robot arm22is to assume in order to carry out a cleaning operation for the workpiece2. Purely by way of example, it can be provided that such a storage of joint positions is carried out by briefly actuating the human machine interface. Furthermore, it can be provided that a setting of a jet cross-section for the nozzle23, which is designed to be adjustable in a manner not shown in more detail, may be set by a longer-lasting actuation of the human machine interface9in the respective cleaning position.

In an alternative embodiment of a nozzle73, as shown inFIG. 4, this nozzle73is a system which comprises three differently designed compressed air nozzles74,75,76which are arranged on the fourth arm part31in a purely exemplary manner The compressed air nozzles74,75,76can be controlled by a valve arrangement arranged in the fourth arm part31, not shown, which is electrically connected to the electronic control27, in an alternative or parallel manner for providing compressed air.

Purely by way of example, each of the compressed air nozzles74,75,76is assigned a respective indicator lamp77,78,79, by means of which it can be indicated which of the compressed air nozzles74,75,76is to be activated during the performance of the teach-in process. Switching between the compressed air nozzles74,75,76can be carried out, for example, with the aid of the human machine interface9. Alternatively, it can be provided that a, in particular capacity based, scanning of the compressed air nozzles74,75,76is carried out by the electronic control27or the valve control15and user inputs are detected by this scanning process. By way of example, during the execution of the teach-in process, a user can, by touching the respective compressed air nozzle74,75,76, select an activation position and/or an activation time for the use of the respective compressed air nozzle74,75,76during the subsequent execution of the cleaning process and receives a visual feedback about the respective activation carried out by the associated indicator lamp77,78,79. In addition, it can be provided that, for example, the storage of a position of the robot4is triggered by a longer lasting contact with one of the compressed air nozzles74,75,76.