Abstract:
The invention relates to a machine tool having a machine frame, a motor-driven machine spindle rotatably mounted on the machine frame, and at least one exchangeable processing head on the machine spindle. The processing head comprises a coupling element compatible with a receiving portion of the machine spindle. Furthermore, a rotary transmitter for data transfer between a stator fixed to the frame and a rotor fixed to the spindle is provided. The invention is characterized in that the machine spindle comprises a plurality of function modules on the spindle side as well as a line system forming a component of a spindle bus to which the function modules on the spindle side are connected to form subscriber stations of the spindle bus and wherein the spindle bus communicates via the rotary transmission path with a field bus fixed to the frame.

Description:
DESCRIPTION 
     The invention relates to a machine tool having a machine frame, having a motor-driven machine spindle which is arranged in a rotatable manner on the machine frame, having at least one machining head which can be exchanged on the machine spindle and has a coupling element that is compatible with a receptacle on the machine spindle, and having a rotary transmitter for transmitting data between a stator which is fixed to the frame and a rotor which is fixed to the spindle. 
     Machine tools of this kind are used for a large variety of manufacturing and metrological tasks. Usually, the various exchangeable machining heads are used for machining metal workpieces, plastics materials or wood. For workpieces which are not rotationally symmetrical, it is possible to carry out lathe-like machining with a rotating spindle which, supported by the machine kinematics, allows additional translational degrees of freedom between the workpiece and the machining head. For this purpose, use is also made for example of facing heads. Facing heads are rotary tool heads which allow a cutting edge to be moved radially with respect to the rotational axis of the spindle. This is put into practice for example in machine tools having special components, such as, for example, spindles having two-stage planetary gears and an additional external drive which makes it possible, when the spindle is rotating, to adjust the driveshaft for the facing slide. To this end, an electrical transmission interface, which allows the machining head to be changed and has a rotary transmitter, is integrated in customary spindle and tool interfaces without impairing the functionality of the mechanism. In principle, the transmission interface in the form of an electrical contactless and/or contacting rotary transmitter can be arranged at the head-side end or at the rear end of the spindle. 
     Depending on the complexity of the machining steps to be carried out and the mechatronic structure, known machine tools of this kind require considerable construction and wiring complexity, which differs from manufacturer to manufacturer even given identical objectives. 
     Proceeding from the above, the invention is based on the object of improving machine tools of the type specified at the beginning in such a way that the construction and wiring complexity can be simplified and standardized for all manufacturers. 
     The combination of features according to the present invention is proposed to achieve this object. Advantageous embodiments and developments of the invention are disclosed. 
     The solution according to the invention proceeds from the idea that the machine spindle and the machining heads of machine tools have a large number of actuating and sensing functional modules, which can be controlled easily via a central machine controller by way of a standardized spindle-side and head-side bus system. In order to make this possible, it is proposed according to the invention that the machine spindle has a plurality of spindle-side functional modules and also a cable system which forms a constituent part of a spindle bus and to which the spindle-side functional modules are connected in the form of subscriber stations or bus subscribers of the spindle bus, wherein the spindle bus additionally communicates via the rotary transmission path with a field bus which is fixed to the frame. On account of the frequently high spindle speeds, the data are expediently transmitted in a contactless manner from the stator side to the rotor side or vice versa, for example via an inductive, capacitive or optoelectronic transmission path or by radio. The rotary transmission path requires adaptation of the transmission protocols, and so the spindle bus expediently has a protocol converter which is fixed to the rotor and communicates, preferably via a field bus adapter, with the field bus. A protocol converter in this case converts protocols between bus systems that differ in terms of protocols. Protocol converters can be software or hardware products or else any desired combinations of the two. 
     Since a large number of different machining heads can be exchanged on the machine spindle and the machining heads can have a wide variety of tasks, the machining heads have a plurality of different head-side functional modules. Expediently, a cable system which forms a constituent part of a head bus and to which the head-side functional modules are connected in the form of bus subscribers of the head bus is also provided in the machining head. In this case, the head bus communicates with the spindle bus, and thus also with the field bus fixed to the frame, via a disconnection point. As a rule, both the machine spindle and the machining head contain sensing and/or actuating functional modules. 
     According to a preferred configuration of the invention, the machine spindle has at least one spindle-side functional module from the group of temperature sensor, vibration sensor, force sensor, pressure sensor, moisture sensor, purging air sensor, lubrication condition sensor, rotational speed sensor, acceleration sensor as measuring element and/or from the group of purging air valve, actuating drive, pneumatic or hydraulic solenoid valve, lubricant dispenser, coolant dispenser, spindle motor as actuator. 
     If the spindle bus and head bus are compatible with one another, they can be connected galvanically at the disconnection point. In the case of different bus systems, appropriate protocol converters must be used. 
     A preferred configuration of the invention provides that the machining head has at least one head-side functional module from the group of linear or rotary slide, actuating drive, drive motor, rotary transducer, position sensor, dispenser, heating element, laser, temperature sensor, acceleration sensor. The actuating drive and the drive motor are in this case expediently provided for slide actuation, while the rotary transducer and position sensor are provided for position measurement within a slide system. 
     For the cleaning, welding and soldering process, on the other hand, the dispensers and heating and cooling modules preferably come into consideration. 
     The head-side functional modules are preferably equipped with a tool from the group of cutting tool, drilling tool, milling tool, reaming tool, welding tool, soldering tool, hardening tool, coating tool, lettering tool, cleaning tool, measuring tool, camera. 
     A standardized field bus, preferably a controller area network (CAN) bus or local interconnect network (LIN) bus, preferably comes into consideration as the spindle bus and/or the head bus. 
     A further preferred configuration of the invention provides that the rotary transmission path has a transceiver for contactless, bidirectional data transmission. 
     Furthermore, the rotary transmission path can additionally have a transceiver for contactless or galvanic transmission of energy. The spindle bus and the head bus can be connected to a central machine controller via a bus system fixed to the frame. 
     The invention is explained in more detail in the following text on the basis of an exemplary embodiment illustrated schematically in the drawing, in which: 
       FIG. 1  shows a diagram of a spindle and head controller of a machine tool for machining workpieces; 
       FIG. 2  shows a diagram of an exemplary embodiment, modified with respect to  FIG. 1 , of the spindle and head controller of a machine tool for machining workpieces; and  FIG. 3  schematically shows alternative embodiments of tools. 
    
    
     The machine spindles  10  illustrated schematically in the drawing are a constituent part of a machine tool for machining workpieces, in particular for complete machining, which additionally has a tool magazine (not illustrated in the drawing) and also a handling apparatus for the tools of the machine. The machine spindle  10  is arranged within the machine tool in a machine frame on which it is arranged for example on a cross table such as to be displaceable in three axes X, Y, Z and also to be rotatable, or is motor-driven. A machining head  12  is exchangeable at a mechanical and electrical disconnection point  14  on the machine spindle  10 , said machining head  12  having a coupling element which is compatible with a receptacle on the machine spindle. Furthermore, there is provided a rotary transmitter  16  for data transmission between a stator  18  fixed to the frame and a rotor  20  fixed to the spindle. 
     Furthermore, the machine tool comprises a central machine controller  22  (NC controller), by way of which, inter alia, the movement of the machining tool  24  is controlled in the machining space of the machine tool. On account of the use of three axes X, Y and Z that are perpendicular to one another, every point in the machining space can be reached. In addition, in the exemplary embodiments shown in  FIGS. 1 and 2 , there is provided a machining head  12  having a facing slide  26  which is displaceable depending on the movement axes of the spindle  10  and which forms an additional, independently controllable U axis. In principle, rather than the facing slide  26  illustrated in the drawing, other kinds of tools can be used as machining head, such as a cutting tool, drilling tool, milling tool, reaming tool, welding tool, soldering tool, hardening tool, coating tool, lettering tool, laser, cleaning tool, measuring tool, camera and the like, as shown schematically in  FIG. 3 . 
     A particular feature of the spindle and head controller according to the invention of the machine tool is that the machine spindle  10  has a plurality of spindle-side functional modules  28 ′,  28 ″,  28 ′″ and also a cable system which forms a constituent part of a spindle bus  30 . The spindle-side functional modules  28 ′,  28 ″,  28 ′″ are connected to the spindle bus  30 , forming subscriber stations. The spindle bus for its part communicates via the rotary transmission path  16  with a field bus  32  fixed to the frame. The functional modules  28 ′,  28 ″,  28 ′″ shown in the two exemplary embodiments can be formed both as sensors and as actuators. In order to monitor the spindle  10 , there are provided a multiplicity of such functional modules, which can be monitored, controlled and regulated predominantly via the central machine controller  22 . Without going into details about the internal structure of the machine spindle  10 , spindle-side functional modules  28 ′,  28 ″,  28 ′″ from the group of temperature sensor, vibration sensor, force sensor, pressure sensor, moisture sensor, purging air sensor, lubrication condition sensor, rotational speed sensor, acceleration sensor, relative acceleration sensor come into consideration as measuring element and/or from the group of purging air valve, actuating drive, pneumatic or hydraulic solenoid valve, lubricant dispenser, coolant dispenser, spindle motor, drives such as rotary drives, actuating drives or linear direct drives, transducers of electrical variables come into consideration as actuator. Individual subscriber stations can also be formed as combination modules for example of a rotational speed sensor or of an actuating drive as purging air sensor and purging air valve. 
     A further particular feature of the invention consists in the fact that the machining head  12 , too, has a plurality of head-side functional modules  34 ′,  34 ″,  34 ′″ and also a cable system forming a constituent part of a head bus  36 . In this case, the head-side functional modules  34 ′,  34 ″,  34 ′″ are connected to the head bus  36 , forming subscriber stations, wherein the head bus  36  communicates with the spindle bus  30 , or a connecting cable  37  provided specifically for this purpose, at the disconnection point  14 . Without going into details about the specific structure of the machining head  12 , the machining head  12  can have at least one functional module  34 ′,  34 ″,  34 ′″ from the group of linear or rotary slide, actuating drive, drive motor, rotary transducer, position sensor, dispenser, heating element. Furthermore, the functional modules  34 ′,  34 ″,  34 ′″ of the machining head  12  can be equipped with a tool  24  from the group of cutting tool, drilling tool, milling tool, reaming tool, welding tool, soldering tool, hardening tool, coating tool, lettering tool, cleaning tool, measuring tool. The above lists of functional modules are by way of example and therefore not complete. 
     In the exemplary embodiment shown in  FIG. 1 , it is indicated that the spindle bus  30  and the head bus  36  are connected in a wireless manner to the field bus  32  of the central machine controller  22  via an additional field bus adapter  38  via the contactless rotary transmission path  16  between the rotor  20  fixed to the spindle and the stator  18  connected to the frame. 
     In the exemplary embodiment according to  FIG. 2 , the machine controller  22  comprises an NC controller  43  having a PLC interface  40 ,  40 ′ and an axis interface  42 ,  42 ′, said NC controller  43  bringing output data for transmission in a contactless manner via an analog NCA control unit  44  and a modulator  46 , which modulates the data onto a carrier signal, and via the data transmission path  16  between the stator  18  and the rotor  20 . In order to match the protocols between different bus systems, a protocol converter  48 ,  50  is arranged both in the spindle  10  and in the machining head  12 . 
     As can also be seen from  FIG. 2 , the digital NC controller can also communicate directly with the modulator  46  of the rotary transmission path  16  via the cable  54  via a standardized field bus  32  and a field bus coupler  52 . Advantageously, standardized field bus systems, such as, for example, a CAN bus, are used as spindle bus  30  and as head bus  36 , and so tool heads from different manufacturers can be connected without great effort. 
     In summary, the following can be stated: the invention relates to a machine tool having a machine frame, having a motor-driven machine spindle  10  which is arranged in a rotatable manner on the machine frame, and having at least one machining head  12  which can be exchanged on the machine spindle  10 . The machining head  12  has a coupling element that is compatible with a receptacle on the machine spindle  10 . Also provided is a rotary transmitter  16  for transmitting data between a stator  18  which is fixed to the frame and a rotor  20  which is fixed to the spindle. A particular feature of the invention is that the machine spindle  10  has a plurality of spindle-side functional modules  28 ′,  28 ″,  28 ′″ and also a cable system which forms a constituent part of a spindle bus  30  and to which the spindle-side functional modules  28 ′,  28 ″,  28 ′″ are connected, forming subscriber stations of the spindle bus  30 , and wherein the spindle bus  30  communicates via the rotary transmission path  16  with a field bus  32  which is fixed to the frame. Advantageously, the machining head  12 , too, has a plurality of head-side functional modules  34 ′,  34 ″,  34 ′″ and also a cable system which forms a constituent part of a head bus  36  and to which the head-side functional modules are connected, forming subscriber stations, and wherein the head bus  36  communicates with the spindle bus  30  via a disconnection point  14 . 
     LIST OF REFERENCE SIGNS 
     
         
           10  Machine spindle 
           12  Machining head 
           14  Disconnection point 
           16  Rotary transmitter 
           18  Stator 
           20  Rotor 
           22  Machine controller 
           24  Machining tool 
           26  Facing slide 
           28 ′,  28 ″,  28 ′″ Spindle-side functional modules 
           30  Spindle bus 
           32  Field bus fixed to the frame 
           34 ′,  34 ″,  34 ′″ Head-side functional modules 
           36  Head bus 
           37  Connecting cable 
           38  Field bus adapter 
           40 ,  40 ′ PLC interface 
           42 ,  42 ′ Axis interface 
           43  NC controller 
           44  NCA control unit 
           46  Modulator 
           48  Protocol converter 
           50  Protocol converter 
           52  Field bus coupler 
           54  Cable