Patent Publication Number: US-9884464-B2

Title: Method for setting up and operating a press

Description:
TECHNICAL FIELD 
     The invention relates to a method for setting up and operating a press for producing a pellet made of powdered material, in particular metal powder. 
     BACKGROUND 
     A press is known for example from DE 10 2011 116 552 A1. For example, metal powder is pressed into pellets with such a press. Two upper drives or two lower drives are thereby frequently provided, wherein the upper drives jointly move an upper press punch and the lower drives jointly move a lower press punch in the vertical direction. It is also known that the lower drives jointly move the die plate. So that the upper or respectively lower drives can act respectively jointly on the pressing tools, the upper or respectively lower drives must be respectively mechanically coupled with each other. In the press known from DE 10 2011 116 552 A1, this occurs for example for the upper drives through a force transmission bridge connected with an upper punch plate holding the upper press punch. A corresponding force transmission bridge is provided for the lower drives. The upper or respectively lower drives are thereby respectively fastened on opposite-lying ends of the force transmission bridge. After the mechanical coupling, the drives must move synchronously in order to avoid tilting or twisting and thus damage to the mechanical coupling or other components of the press to the greatest extent possible. For this, during commissioning of the press before the mechanical coupling, the drives can be moved individually so that a mechanical coupling is possible without tilting or twisting of the mechanical coupling. The drives are then only run synchronously at a synchronized speed. 
     SUMMARY 
     When operating the press, deviations between the drives may occur, for example due to a drive lag in an emergency stop situation or a loss of power. This is not necessarily detected by the operator of the press, in particular if they are comparatively small deviations. If the drives then continue to be synchronously operated by the controller of the press, the once generated deviations from the synchronized speed and thus the tilting or respectively twisting of the mechanical coupling persist. This asynchronous state of the drives can become larger with each fault and thus damage the mechanical coupling and other components of the press, such as drive spindles, adapters or pressing tools. The operator of the press must thus regularly check the synchronized speed of the drives manually. A synchronization of the drives with each other is thereby only possible with considerable measurement effort; in particular, an exact path measurement of the drives or respectively a distance measurement to a machine zero point. 
     According to the teachings herein, however, a mechanical coupling of the drives is possible without risk of damage to the mechanical coupling or other components of the press with less effort than that previously described. 
     A press may comprise a press frame, at least one upper punch plate with at least one upper press punch held on it and/or at least one lower punch plate with at least one lower press punch held on it and a die plate with at least one receiver for powdered material to be pressed by the upper and/or lower press punch. The press may also comprise at least two upper drives mechanically coupled in the operation of the press, engaging at the upper punch plate for moving the upper press punch in the vertical direction and/or at least two lower drives mechanically coupled in the operation of the press, engaging on the lower punch plate and/or the die plate for moving the lower press punch and/or the die plate in the vertical direction. 
     In a setup procedure of such a press according to the teachings herein, upper drives are respectively moved into a coupling position in which they are coupled mechanically and/or lower drives are respectively moved into a coupling position in which they are coupled mechanically. Before a pressing procedure, the positions of the mechanically coupled upper drives are measured and, if a maximum permissible position deviation is exceeded, at least one of the upper drives is moved so that the maximum permissible position deviation is no longer exceeded. Alternatively, or in addition thereto, the positions of the mechanically coupled lower drives are determined, and, if a maximum permissible position deviation is exceeded, at least one of the lower drives is moved so that the maximum permissible position deviation is no longer exceeded. 
     The press used in the method above may have a press frame, for example with an upper and a lower holding plate, which are interconnected by several vertical spacers. A bearing element can be arranged between the upper and the lower holding plates. Moreover, a tool guiding unit or respectively an adapter is provided with at least one upper press punch, which is fastened on an upper punch plate, and/or with a lower press punch, which is fastened on a lower punch plate, as well as with a die plate with a receiver for powdered material to be pressed by the upper and/or lower press punches. The powdered material may be, for example, metal powder or also ceramic powder. The tool guiding unit can be arranged on the bearing element. Moreover, the press has at least two upper drives and/or at least two lower drives. The upper drives drive the upper press punch and/or the lower drives drive the lower press punch or the die unit. The drives can be supported during operation on the bearing element, which can be designed for example as a support frame. 
     The press can stand on feet or directly on the ground via the lower retaining plate of the press frame. The press generally comprises at least one upper punch and at least one lower punch, which interact in the receiver of the die plate for pressing the filled powder. However, it is also possible to provide a pressing, for example, only from above using only one upper punch if the receiver of the die plate has a closed bottom. As explained, the lower drives can drive a lower press punch or a die plate in the vertical direction. Thus, it is possible to operate the press both in an ejection method, in which the die plate is stationary and the upper and lower punches move with respect to the die plate, as well as in the pull-off method, in which the lower punch is stationary and the die plate and the upper punch are movable. 
     In the method according to the teachings herein, the upper drives and/or the lower drives are respectively moved in a setup procedure before the mechanical coupling so that a mechanical coupling is possible without tilting or respectively twisting the components involved in the mechanical coupling as far as possible. In this coupling position, the upper drives are mechanically coupled and/or the lower drives are mechanically coupled. 
     Before a pressing procedure is performed with the press, the proper position of the drives is checked. This can take place in particular before each pressing procedure. It can also take place during a pressing procedure or at other times. For this, the positions of the upper and/or the lower drives are measured for example with a position measuring device integrated into the drives. The maximum permissible position deviation forms a threshold value, which would lead to an impermissible tilting or respectively twisting of the components of the mechanical coupling. The position deviation can be a deviation between the measured positions of the upper drives and/or a position deviation between the measured positions of the lower drives. It can also be a deviation to a respective target position specified for the upper drives and/or the lower drives. As already mentioned, the maximum permissible position deviation is determined such that, up until this position deviation is reached, a just acceptable tilting or respectively twisting of the mechanical coupling is present. The tilting or twisting may exist at, for example, the connection of the drives with a force transmission bridge or respectively the force transmission bridge itself or its connection to the respective punch plate or respectively the die plate. 
     Thus, the synchronized speed of the drives is checked before the pressing procedure. If an impermissible position deviation is determined, the drives are synchronized again by the machine controller of the press in that at least one of the upper drives and/or at least one of the lower drives is moved far enough that a present position deviation and thus tilting or respectively twisting of the mechanical coupling again assumes an acceptably low value, preferably the value zero. Only after this procedure is complete, the movement of the drives is started for the actual pressing procedure of the press. 
     The activation of the measuring devices for measuring the position of the drives and the activation of the drives for moving one or more drives can take place as explained in particular through the machine controller of the press. According to the invention, the upper drives or respectively the lower drives thus only need to be aligned during the setup procedure taking place in the course of the commissioning. Deviations in the synchronized speed potentially occurring during operation are then automatically detected and compensated for by the machine controller. The effort during operation of the press, in particular for avoiding an impermissible tilting or twisting of the mechanical coupling and thus damage to components, is considerably simplified compared to the art previously described. 
     According to one embodiment, the coupling position and a maximum permissible position deviation from the coupling position are respectively saved in the setup procedure for the upper drives and/or the coupling position and a maximum permissible position deviation from the coupling position are respectively saved in the setup procedure for the lower drives. 
     According to one implementation, at least before a pressing procedure, a first of the mechanically coupled upper drives is moved into its coupling position and a position deviation of the second of the upper drives to its coupling position is measured and is moved when the saved maximum permissible position deviation from the coupling position of the second of the upper drives is exceeded such that the maximum permissible position deviation is no longer exceeded. Alternatively, or in addition thereto, at least before a pressing procedure, a first of the mechanically coupled lower drives is moved into its coupling position and a position deviation of the second of the lower drives to its coupling position is measured and is moved when the saved maximum permissible position deviation from the coupling position of the second of the lower drives is exceeded such that the maximum permissible position deviation is no longer exceeded. 
     In the case of these embodiments, the coupling position of the upper drives and/or the lower drives is saved as a machine zero point. In their coupling position, the upper drives or respectively the lower drives are each positioned the same to the greatest extent possible so that no tilting or respectively twisting of the mechanical coupling is present as far as possible. A maximum permissible position deviation from the coupling position is simultaneously saved for each of the drives. Before a pressing procedure, one of the mechanically coupled upper drives or respectively one of the mechanically coupled lower drives is moved into its coupling position. In the case of a proper synchronized speed, the other of the upper or respectively lower drives would then have to be located in its coupling position. This is checked metrologically. If a position deviation of the other of the upper or respectively lower drives with respect to its coupling position is determined, this is compared to the previously saved maximum permissible position deviation. If the maximum permissible position deviation is exceeded, the other of the upper or respectively lower drives is correspondingly moved in order to re-establish the desired synchronized speed. It is in particular possible that the second of the upper drives is also moved into its coupling position when the saved maximum permissible position deviation from the coupling position is exceeded and/or that the second of the lower drives is also moved into its coupling position when the saved maximum permissible position deviation from the coupling position is exceeded. 
     According to the teachings herein, the maximum permissible position deviation can generally also be specified such that any position deviation from the specified synchronized speed, in particular from the specified coupling position, is defined as impermissible and is correspondingly compensated for by the machine controller by moving the respective drive. 
     The measuring of the positions of the mechanically coupled upper drives and/or the measuring of the positions of the mechanically coupled lower drives can take place automatically before a pressing procedure, in particular automatically before each pressing procedure. As already mentioned, the measuring can be triggered for example by the machine controller of the press. The movement of at least one of the upper drives when a maximum permissible position deviation is exceeded and/or the movement of at least one of the lower drives when a maximum permissible position deviation is exceeded can also take place automatically. In turn, this can take place in particular automatically before each pressing procedure, triggered for example by the machine controller of the press. The pressing procedure is only released and executed after proper checking or respectively re-establishment of the synchronized speed. 
     The exceeding of a maximum permissible position deviation can be displayed by a warning signal. This can be an optical or an acoustic warning signal. 
     It is also possible that the movement of at least one of the upper drives when a maximum permissible position deviation is exceeded and/or the movement of at least one of the lower drives when a maximum permissible position deviation is exceeded takes place after confirmation by an operator. In this case, an operator confirms, for example after a warning signal, that the re-establishment of the synchronized speed of the drives, in particular the movement of the drives respectively into their coupling position, should be performed. This is thus a semi-automatic variant. 
     The upper drives and/or the lower drives can be electric drives, in particular electric spindle drives. Spindle drives are particularly suitable since they can transfer very high forces in a precise manner. Moreover, the vertical position of the spindle drives is measurable very exactly for example via a measurement of the rotational position of the spindle drives. 
     According to a further embodiment, the upper drives are mechanically coupled via an upper force transmission bridge acting on the upper punch plate and/or that the lower drives are mechanically coupled via a lower force transmission bridge acting on the lower punch plate and/or the die plate. The upper drives or respectively the lower drives can be fastened, for example screwed, for example on opposite-lying ends of the upper force transmission bridge or respectively of the lower force transmission bridge. The screw connection can take place if necessary via elastic compensation elements for compensating for a certain deviation from the synchronized speed of the drives and an associated tilting of the force transmission bridge. The upper or respectively lower force transmission bridge can be connected with the upper or respectively lower punch plate or respectively die plate via a force transmission element, which can be arranged for example centrally on the respective force transmission bridge. 
     According to a further embodiment, respectively one spindle nut of the upper spindle drives can be fastened on the upper force transmission bridge and/or respectively one spindle nut of the lower spindle drives can be fastened on the lower force transmission bridge. Electric drive motors of the elastic drives can be fastened for example on the upper or respectively lower holding plate of the press frame. In the aforementioned embodiment, the spindles can respectively be permanently arranged axially and coupled in a rotatable manner with the drive motors. The spindle nuts and the force transmission bridges connected with them are then moved axially during a rotation of the spindles. However, alternatively, it is also possible that the spindles of the spindle drives are fastened on the force transmission bridge and the spindle nuts are permanently arranged axially and coupled in a rotatable manner with the drive motor. In this case, the respective spindles and the force transmission bridges connected with them are moved axially during a rotation of the spindle nuts moved by the drive motor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the invention is explained in greater detail below with reference to a figure wherein: 
         FIG. 1  is a schematic view of a press used in a method according to the exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The press has a press frame with an upper retaining plate  10  and a lower retaining plate  12 . The upper retaining plate  10  and the lower retaining plate  12  can be interconnected via vertical spacers (not shown in greater detail). With the lower retaining plate  12 , the press stands on feet  14  on the ground. In the example shown, the press has two upper drives and two lower drives. The upper and lower drives here are respectively electric drives. The upper drives each have an upper electric drive motor  16  fastened on the upper retaining plate  10 , which rotatably drives an upper, axially fixed spindle  18 . The upper spindles  18  are respectively supported on a support frame  20  on its end facing away from the drive motors  16 . Correspondingly, the lower drives each have a lower electric drive motor  22  arranged on the lower retaining plate  12 , wherein the lower electric drive motors  22  respectively rotatably drive a lower, axially fixed spindle  24 . The lower spindles  24  are also supported on the support frame  20 . Moreover, the upper drives each have a spindle nut  26  running on the upper spindles  18 . The upper spindle nuts  26  are mechanically coupled with each other via an upper force transmission bridge  28 . In particular, the upper spindle nuts  26  are screwed with opposite-lying ends of the upper force transmission bridge  28 , if applicable via elastic compensation elements. The upper force transmission bridge  28  is connected with an upper punch plate  34  via a central force transmission element  30  and two further compensation elements  32 . An upper press punch  36  is fastened on the upper punch plate  34 . The upper punch plate  34  is guided in the vertical direction on vertical guide columns  38 . 
     Correspondingly, the lower drives each have a lower spindle nut  40  guided on the lower spindles  24 . The lower spindle nuts  40  are in turn screwed on opposite-lying ends of a lower force transmission bridge  42 , if applicable via elastic compensation elements. The lower force transmission bridge  42  is connected with a lower punch plate  48 , which carries a lower press punch  50 , via a lower force transmission element  44  and compensation elements  46 . The lower punch plate  48  is also guided in the vertical direction on vertical guide columns  52 . The vertical guide columns  38 ,  52  are supported on a die plate  54  fastened on the support element or frame  20 . The die plate  54  has a die  56 , which forms a receiver  58  for powder to be pressed with the press, for example metal powder. During operation, the upper punch  36  and the lower punch  50  work together with the receiver  58  to press the powder filled into the receiver  58  into a pellet. For this, the upper spindle nuts  26  are moved in the vertical direction by rotation of the upper spindles  18  and the lower spindle nuts  40  by rotation of the lower spindles  24 . This arrangement is known. 
       FIG. 1  also shows position measuring devices  60  for measurement of the position of the upper drives. The position measurement can take place for example by measuring the rotational position of the upper spindles  18 . Corresponding position measuring devices  62  for the position measuring of the lower drives are designed identically to the position measuring devices  60  for the upper drives. Reference number  64  shows a machine controller of the press. 
     In the method according to the exemplary embodiment, the upper spindle nuts  26  are first moved into a coupling position while they are not yet connected with the upper force transmission bridge  28 . The coupling position is selected such that a coupling takes place via the upper force transmission bridge  28  without a tilting or twisting of the components transmitting the mechanical coupling. In this state, the upper spindle nuts  26  are coupled with each other through the upper force transmission bridge  28 . The coupling positions of the upper drives, in particular of their spindles  18  or respectively spindle nuts  26 , assumed in this coupling are measured by the position measuring devices  60  and saved in the machine controller  64 . Moreover, a maximum permissible position deviation from the coupling position for each of the upper drives, in particular their spindles  18  or respectively spindle nuts  26  is saved in the machine controller  64 . In an analogous manner, the lower drives, in particular the lower spindle nuts  40  are moved into their respective coupling position and mechanically coupled with each other, wherein the coupling positions of both lower drives, in particular of their spindles  24  or respectively spindle nuts  40 , are in turn measured by the position measuring devices  62  and saved together with a maximum permissible position deviation in the machine controller  64 . 
     Each time before a pressing procedure is performed with the press, one of the upper drives, in particular one of the upper spindles  18  or respectively spindle nuts  26 , is automatically moved into the coupling position by the machine controller  64  and the position of the other upper drive, in particular of the other upper spindle  18  or respectively spindle nut  26 , is measured with the position measuring devices  60 . The measurement results are given to the machine controller  64 . In the case of a deviation from the saved coupling position, the corresponding upper electric drive motor  16  is automatically controlled by the machine controller  64  such that the drive deviating from the coupling position, in particular the spindle  18  or respectively spindle nut  26  deviating from the coupling position, is moved back into the coupling position. In an analogous manner, this is also performed automatically for the other drives, in particular the lower spindles  24  or respectively spindle nuts  40 , by the machine controller  64 . Only after the synchronized speed of the upper and lower drives has been checked and, if necessary, re-established in this manner, the pressing procedure is triggered by the machine controller  64 .