Abstract:
A machine tool comprising a machine column, a work spindle moveable in guides along the machine column in two coordinate axes by a motor and adapted to receive a cutting tool, a machine bed arranged on the front end of the machine column and on the top side of which a horizontal linear guide for a workpiece table is arranged, and a linear motor for moving the workpiece table in the horizontal linear guide in a further coordinate axis. A channel-like chip space for collecting chips accumulating when the workpiece is machined extends on the top side of the machine bed in the direction of the further coordinate axis. The linear motor is arranged on the top side of the machine bed laterally and parallel to the channel-like chip space, wherein first and second guide rails of the horizontal linear guide are arranged on opposite sides of the linear motor.

Description:
FIELD 
     The present application relates to a universal machine tool for machining workpieces. 
     BACKGROUND 
     DE 100 61 934 B4 and DE 102 45 058 A1 disclose machine tools, which, due to their make, are distinguished by a special rigidity and thus also a high-cutting capacity as well as high accuracy during the machining operation. This machine tool has a dimensionally rigid machine column at the front end of which a work spindle is guided in guide rails and is arranged in a horizontally and vertically movable fashion. The universal machine tool comprises a highly rigid machine bed which is arranged at the front end of the machine column and the top side of which accommodates a horizontal linear guide for a workpiece table that can be moved by means of a linear motor in a further coordinate axis Z along the machine bed. 
     The chips accumulating with universal machine tools can be relatively extensive. For this reason, the protection of the machine units and components from flying chips as well as the collection and removal of accumulating chips have always been an inherent problem in the machining of metals by means of universal machine tools. 
     It has thus been proposed in the prior art to provide chip collecting and removing spaces when machine tools are designed. For example, DE 198 30 391 A1 proposes a milling machine in which the workpiece spindle is movably guided in a cantilever arrangement and a chip collecting space extending in the transverse direction relative to the machine bed is located at the rear end of the machine table in the direct vicinity of the workpiece clamping surface of the workpiece table. However, this design is not very suitable for a workpiece table which can be moved horizontally on the machine bed in a longitudinal direction since a reliable chip collection and removal would not be ensured in this case. 
     In addition, the provision of a chip collecting space is accompanied by design limitations as far as the fundamental configuration of the machine frame and of the machine column is concerned. An important aspect is to guarantee a sufficiently high rigidity of both the machine column and the machine bed. 
     A heavy-duty machining center which ensures a reliable and extremely fast chip disposal from the work area has been presented by the company StarragHeckert, by means of the CWK 400 D machining centers. However, the machine configuration of this machining center, which is a cross-bed design having an inclined bed, is rather complicated and not very compact. 
     BRIEF SUMMARY 
     Disclosed herein is a universal machine tool that is as compact as possible and is improved as regarding the collection and removal of accumulating chips, without reducing the rigidity of the machine frame. 
     The universal machine tool has a dimensionally stable machine column along which a work spindle is guided, which can be moved in guides in two coordinate axes X and Y by means of a motor and is adapted to receive a cutting tool. At the front end of the machine column a machine bed is attached, and the top side of said bed is provided with a horizontal linear guide for a workpiece table and a linear motor for moving the workpiece table in the horizontal linear guide with a further coordinate axis. 
     A channel-like chip space for collecting chips accumulating when the workpiece is machined is provided in or on the machine bed and the longitudinal axis of said chip space extends in a horizontal direction along the machine bed, wherein the linear motor is arranged on the top side of the machine bed laterally and parallel to the channel-like chip space. First and second guide rails of the horizontal linear guide for guiding the workpiece table are arranged on opposite sides of the linear motor, i.e., the linear motor is located between two guide rails of the horizontal linear guide, said rails being arranged laterally on the top side of the machine bed adjacent to the linear motor. 
     The arrangement of a channel-like chip space in the longitudinal direction of the machine bed enables an improved collection and removal of the chips accumulating when the workpiece is machined, without the stability of the machine bed being impaired. 
     Arranging the linear motor for the workpiece table laterally adjacent to the chip channel ensures an efficient protection from accumulating flying chips. In addition, the arrangement of the linear motor and of the channel-like chip space in combination with the arrangement of the guide rails on both sides of the linear motor makes it possible to position various workpiece tables for the universal machine tool in an optimum way. 
     A turnable rotary table can be guided on the first and second guide rails, advantageously by means of ball or linear roller bearings. 
     In an advantageous embodiment, the machine structure has, f r this purpose, a third guide rail which, with respect to the first guide rail, is arranged on an opposite side of the channel-like chip space, and therefore the bottom side of a table slide, which carries an NC rotary table and is guided along the three guide rails, overlaps the channel and is moved directly above the channel along its entire longitudinal side when the linear motor is driven. This arrangement enables an optimum chip collection when a workpiece clamped on the NC rotary table is machined. 
     In an alternative embodiment, the universal machine tool can be equipped for 5-axis machining, with a swivel rotary table that is advantageously also guided on first and second guide rails by means of ball or linear roller bearings, wherein the bottom side of the table slide covers the linear motor. 
     The swivel rotary table is advantageously equipped with a swivel axis that enables a swivel angle of &gt;180°, preferably up to 220°, so as to move the tool table to an upside-down position in which a workpiece clamped on the workpiece table can be machined by the work spindle, wherein the chips fall directly into the channel-like chip collecting space. 
     The channel-like chip space of a preferred exemplary embodiment is inserted in the top side of the machine bed and has side walls steeply sloping towards a bottom region. In addition, angular plates are mounted directly on the table and protrude downwardly into the channel-like chip space so as to ensure that the accumulating chips are conveyed directly into the chip space. 
     In a preferred exemplary embodiment, the channel-like chip space extends centrally in the machine bed in the Z-axis shown in  FIGS. 1 and 2 . 
     A chip screw conveyor for removing chips disposed in the chip space is advantageously provided at the bottom of the channel-like chip space in a horizontal direction. 
     The configuration of the machine bed of the universal machine tool is particularly advantageous in the case of a moving column-bed design of the universal machine tool since the machine stability necessary for precision machining is reliably ensured. 
     In a particularly stable version of the machine tool for machining workpieces, the machine column is equipped with three vertical and parallel guides along which the work spindle is guided, wherein the middle guide carries the load which is produced by the magnetic force of a linear motor that is provided for moving the work spindle in a vertical direction. In this way, the stability of the machine design can be further improved in the area of the moving column, without having to increase the masses contributing to stability. Surprisingly, this is particularly advantageous in the case of moving column-bed type machine tools in which the moving column is made as a triangular closed box design, as is the case, e.g., in DE 102 45 058 A1 described at the beginning, since the stability of a machine model of this type is thus particularly increased when the high-speed spindle is moved. 
     The machine bed configuration disclosed herein enables an optimum removal of machining chips for configurations having NC rotary tables and also for machine tools with a swivel rotary table for 5-axis machining, without having to make further design modifications to the machine. The basic configuration described herein can be realized according to the required conditions or customer&#39;s desire without further modification using both an NC rotary table and a swivel rotary table, in both cases a reliable chip removal being ensured over the entire travel of the respective workpiece table. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Further details and advantages of the present invention become apparent by means of the following description of exemplary embodiments of the universal machine tool including a chip space using the drawings, wherein: 
         FIG. 1  shows a perspective view of a first exemplary embodiment of a universal machine tool including an NC rotary table; 
         FIG. 2  shows a perspective view of a further exemplary embodiment of a universal machine tool which includes a chip space and on which a swivel rotary table is mounted; 
         FIG. 3  shows a cross-section of an exemplary embodiment of a universal machine tool including a chip space and an NC rotary table as illustrated in  FIG. 1 ; 
         FIG. 4  shows a cross-section of an exemplary embodiment of a universal machine tool including a chip space and a swivel rotary table as illustrated in  FIG. 1 ; 
         FIG. 5  shows a perspective view of an exemplary embodiment of a swivel rotary table for assembly on a universal machine tool; and 
         FIG. 6  shows a schematic diagram of a universal machine tool including a swivel rotary table to illustrate the swivel range. 
     
    
    
     DETAILED DESCRIPTION 
     A first exemplary embodiment of a universal machine tool including an NC rotary table is shown in a perspective inclined front view in  FIG. 1 . The universal machine tool having a moving column-bed design consists of a front machine bed  2  made as a box design and a rear stationary moving column  3  at the front end of which the box-shaped machine bed  2  is attached. In this embodiment according to  FIG. 1 , the column is made of two parts and has a bottom part  4  which is permanently fixed to the machine bed  2  and a moving column part  5  which can be moved in two guide rails  6  and  7  in the X-direction by means of a linear motor. The moving column part  5  has a front side including three vertical guide rails  8 ,  9 ,  10 , on which a vertical slide  11  with a spindle head  12  for receiving a cutting tool is movably arranged by means of a linear motor  70 . The middle guide rail  9  carries the load of the magnetic drive. The machine bed is supported via the two supports  2   a ,  2   b  towards the bottom. 
     The top side of the box-like machine bed  2  accommodates three guide rails  13 ,  14 ,  15  of a horizontal linear guide, on which a workpiece table  16  is movably guided in a Z-direction by means of a linear motor. The linear motor (not shown in  FIG. 1 ) for moving the table slide is arranged between the guide rails  14 ,  15  and is protected toward the top by a cover  20 . 
     A table slide  18  carries an NC rotary table  21 , the top side of which carries a pallet  22  which is suitable for clamping a workpiece (not shown). The bottom side of the table slide  18  is movably arranged directly above a channel-like chip space  19 , the structure of which is more clearly seen in  FIG. 3 . 
     In the front area of the machine bed, a recess having a U-shaped section  25  is inserted in the machine bed  2 , which enables the connection of a pallet changer (not shown in  FIG. 1 ). The spatial arrangement of the channel-like chip space  19 , which directly borders on the U-shaped wall portion of the machine bed enables an optimum space efficiency with the machine bed configuration, and therefore the universal machine tool is also compact when designed as a machining center having a pallet changer. 
       FIG. 2  shows an inclined front view of a further exemplary embodiment of a universal machine tool, said exemplary embodiment differing from that shown in  FIG. 1  in that the machine bed  2  of this exemplary embodiment carries a swivel rotary table  30 , and in addition a pallet changer  40  is attached to the front area of the machine bed  2 , said pallet changer having an exchangeable pallet  41  for exchange with the pallet  31  supported on the swivel rotary table  30 . 
     The swivel rotary table  30  comprises a lower slide part  32  which is guided on the guide rails  14 ,  15  and carries a box-shaped table housing  33 . A drive motor for swiveling the console  34  of the machine table is attached to or accommodated in or at the box-shaped housing  33 . By means of said motor, the working plane of the workpiece table can be rotated, as explained in detail below with reference to  FIGS. 5 and 6 . By means of the swivel axis, it is possible to take the working plane of the workpiece table  34  by swiveling the console  34  to an upside-down position which is shown in  FIG. 6 , and therefore the working plane  35  of the workpiece table which is swiveled so as to be upside-down can be positioned directly above the chip channel  19 . 
     A pallet changer  40  is attached to the front head end of the machine bed  2  and is inserted in the recess that has a U-shaped section and is shown in  FIG. 1 . The compactness here results, above all, from the fact that the pallet changer can be attached directly to a machine bed portion which borders on the channel-like chip space so as to guarantee, on the one hand, that the pallet changer must only travel short distances when the pallet is exchanged and, on the other hand, that even in the basic exchange position of the pallet changer, the workpiece table is also already arranged directly above the channel-like chip space. 
       FIG. 3  shows a cross-section through the machine bed  2  of the exemplary embodiment of  FIG. 1 , said cross-section clearly showing the structure of the channel-like chip space  19  in the machine bed  2 . 
     The chip channel  19  is formed by two almost vertically sloping side walls  19   a ,  19   b . The bottom area of the channel is formed by the slightly inclined bottom portions  19   c ,  19   d . The area of the lowest point at the bottom of channel  19  accommodates a conveyor screw  50  which serves for removing the accumulating chips. Angular guide plates  25   a ,  25   b  are mounted on the workpiece table and ensure that the chips accumulating when a workpiece clamped on the pallet  22  is machined are directly fed to the channel-like chip space so as to prevent, in particular, contamination of the horizontal linear guide and the linear motor  17 . These angular guide plates  25   a ,  25   b , which are mounted in the longitudinal direction of the machine bed advantageously on the front and rear sides of the workpiece table, move at the front end of the machine bed into a recess of the pallet changer or the machine bed portion receiving the same and at the rear side into a recess formed for this purpose in the front end of the moving column, and therefore the travel of the table is not limited by the guide plates. 
     On the bottom side, the workpiece table  16  has a table slide  18 , at the bottom side of which linear roller bearings  13   a ,  14   a ,  15   a  are mounted which are guided on the profile rails  13 ,  14 ,  15 . The table slide  18  is movable by means of the linear motor  17  in the Z-direction shown in  FIG. 1 , wherein the linear motor primary part  17   a  is connected to the console of the table slide  18  and is guided along the linear motor secondary part  17   b  which is formed on magnetic path segments. In this connection, it is advantageous for the linear motor primary part  17   a  and the linear motor secondary part  17   b  to be arranged in a width-wise direction between the profile rails  14 ,  15  and parallel to the channel-like chip space  19  which, in turn, extends along the entire length of the linear guide rails  13 ,  14 ,  15  and parallel thereto. 
     The profile rails are advantageously provided with thermo-symmetrical linear measuring scales  13   b ,  14   b ,  15   b , which contribute considerably to the accuracy of the determination of the position of the workpiece table. 
     The table slide  18  carries a cylindrical middle part  21 , the top side of which supports a workpiece pallet  22  that can hold a workpiece in clamped fashion by means of a suitable clamping device. As evident from the illustration of  FIG. 3 , the table slide  18  overlaps the channel-like chip space in the width-wise direction, wherein the top side of the workpiece table  16 , on which the workpiece (not shown) is clamped, is arranged so as to be moveable directly above the channel and over its entire length in a Y-direction. 
     An improved stability of the guide is achieved by guiding the NC rotary table in the three guide rails  13 ,  14 ,  15 . An optimum protection of the linear motor from accumulating chips is simultaneously achieved by a lateral displacement of the linear motor with respect to the plane of the channel-like chip space or the movement plane of the NC table. In addition, the inventive structure of the machine bed enables an optimum combination of the machine tool with a chip conveyor. 
     A cross-section through a universal machine tool, as shown in the exemplary embodiment of  FIG. 2 , is explained below by means of  FIG. 4 . Reference signs identical to those in  FIGS. 2 and 3  refer to corresponding parts without special mention. 
     In the example illustrated in  FIG. 4 , an overhung swivel rotary table  30  is mounted on the universal machine tool, said table being guided via linear roller bearings  14   a ,  15   a , which are mounted on the bottom side of the table housing  33 , in the profile rails  14 ,  15  of the horizontal linear guide. The drive for moving the swivel rotary table  30  in a Z-direction is accomplished via the linear motor  17  which is arranged between the guide rails  14 ,  15 , wherein the linear motor primary part  17   a  oriented horizontally in cross-section is mounted on the bottom side of the housing  33  of the swivel rotary table  30  and is moved along the linear motor secondary part  17   b . As in the exemplary embodiment of  FIGS. 1 and 3  and as illustrated in  FIG. 2 , the channel-like chip space extends along the entire length of the guide rails  14 ,  15 , and therefore a reliable feed of the accumulating chips into the chip space is ensured in every operating position of the swivel rotary table  30  movable in a Z-direction. 
     In the basic position of the swivel rotary table, the working area for clamping the workpiece on the workpiece table  35  is oriented horizontally on the protruding console  34  and is arranged below the work spindle  12 . By means of a swivel axis which is not shown in  FIG. 4 , the console  34  of the swivel rotary table  30  can, however, be swiveled upwards about a swivel axis in a horizontal drawing plane, and therefore the surface  35  of the swivel rotary table on which the workpiece is clamped is arranged above the work spindle in an upside-down position. 
     Optimum removal of the accumulating chips into the chip space is ensured in every operating position of the work spindle and of the swivel rotary table by the arrangement described herein and the movability of the swivel rotary table via the channel-like chip space in any swivel position of the workpiece table. 
     In this exemplary embodiment too, the channel-like chip space has almost vertical side walls  19   a ,  19   b  to which a bottom portion having the inclined bottom portions  19   c ,  19   d  is attached. As in the preceding exemplary embodiment, a chip conveyor screw  50  is provided at the lowest point of the bottom of the channel-like chip space in the exemplary embodiment of  FIG. 4 , said conveyor screw serving for removing the accumulating chips. 
     The arrangement of the guide rails of the linear motor and of the channel-like chip space in the machine bed of the universal machine tool, and in particular in the moving column-bed model, ensures that in both the use of an NC rotary table and the use of a swivel rotary table, the workpiece table top side is moved directly above the channel-like chip space so as to ensure optimum chip removal in every operating position. Due to the steeply sloping side walls of the channel-like chip space in combination with the lateral arrangement of the guide plates, an optimum collection of the chips is ensured, which is, in particular, important for a dry processing operation on the machine tool. 
       FIG. 5  shows details of a preferred embodiment of a swivel rotary table for use with the machine configuration described herein. It should be noted here that the swivel rotary table shown in  FIG. 5  is not confined to use with the machine configuration described herein but can also be employed in conventional machine tools. For this reason, separate protection may be sought for the central features of the swivel rotary table. 
     The swivel rotary table comprises two electric motors  37  and  38  for turning and swiveling the table  30  about an A-axis shown in  FIG. 6 . Here, the motor  38  is mounted outside the housing  33  on the outer side thereof, and the motor  37  is mounted centrally in the housing. At least one of the motors  37 ,  38 , preferably both motors as shown in the swivel rotary table of  FIG. 5 , is arranged in the range of the housing  34  outside the cast parts of the machine. The advantage is that the motors are well accessible on the one hand, which is useful in the case of a repair or exchange, and in addition they are arranged outside the zone of thermal influence, i.e., in the temperature-neutral portion and not in the overhung portion, and therefore their functioning is not impaired by heat transfer caused by the cast parts. In addition, the motors  37 ,  38  which are not arranged in the overhung portion of the console  34  of the swivel rotary table are not exposed to any weight load, which also adds to the positioning accuracy. 
     A cable carrier system for conducting electric supply cables to the motor  37  is mounted on the rear side of the table housing  33 , which ensures an efficient and reliable cable guiding for operating the motors when the swivel rotary table  30  is moved. The drive torque of the motor  38  for pivoting the console is transmitted to the transmission  39  via a V-belt. 
       FIG. 6  illustrates the swivel range of the swivel rotary table for use with a machine configuration described herein. The diagram illustrates that the swivel axis (A-axis) enables swiveling of the working plane  35  of the tool table by up to 220°, which allows optimum 5-axis processing. 
     Because of this swivel range, optimum processing of workpieces in an upside-down position is possible, wherein a combination of the swivel rotary table and of the machine configuration ensures a reliable removal of the accumulating chips via the channel-like chip space. 
     The achievable acceleration or speed values, which can be 20/S 2  and/or 20 minutes −1  for the A-axis and 30/S 2  and 40 minutes −1  for the axis of rotation, are further features of the swivel rotary table. 
     The invention is not confined to the presented exemplary embodiments but comprises further combinations of the structural details presented in this description so as to create further exemplary embodiments according to the required use on the basis of the knowledge of a person skilled in the art.