Method for monitoring a machining process in a machine tool, and machine tool

Abstract

The present invention relates to a method for monitoring machining processes (49) in a processing machine (1), the method comprising machining processes (49) for machining a workpiece (10) by means of a machining tool including an upper tool (11) and a lower tool (9), in each machining process (49) time-synchronous process signals (52, 53, 54, 55, 56, 57, 58) are detected by sensors (29, 31, 32, 33) of the processing machine (1) and transmitted to a control device (15), and the process signals (52, 53, 54, 55, 56, 57, 58) determined in a time-dependent manner during the machining process (49) are detected by sensors (29, 31, 32, 33) of the processing machine (1) and transmitted to a control device (15). 5, 56, 57, 58) are converted by a conversion into characteristic curves (59, 60, 62, 63, 64, 65, 67, 68, 69, 71, 72) having a force-displacement curve, which characteristic curves are plotted in a time-independent force-displacement graph, and from the progression of the characteristic curves (59, 60, 62, 63, 64, 65, 67, 68, 69, 71, 72) in the force-displacement graph the wear of the machining tools (11, 9) is determined independently of one another and / or the material of the workpiece (10) underlying at least one machining process (49).

Description

Technical Field

[0001] The present invention relates to a method for monitoring a machining process in a machine tool and to a machine tool, and more particularly to a machine tool for performing a machining process for machining a plate-shaped workpiece with a machining tool.

Background Art

[0002] From Patent Document 1, a method for monitoring a tool clamping device installed on a machine spindle is known. The clamping force of the machine spindle installed in the tool clamping device is generated by a spring assembly that applies a force in the direction of the clamping position to an operating element that clamps or releases the tool or tool holder. When the tool or tool holder is released and / or clamped, the spring force and the displacement of the operating element are continuously measured and recorded as a function of time. From these recorded functions, at least one parameter characterizing the state of the tool clamping device is determined. From the spring force and displacement as a function of time, a spring characteristic curve can be determined in the form of the spring force as a function of displacement, and information regarding a series of characteristic parameters can be obtained by evaluating the spring characteristic curve.

[0003] From Patent Document 2, a tool wear monitoring system is known, particularly for enhancing the effect in machining during automation. At that time, the wear of the tool is detected in relation to the cutting force. As indicated by a linearly increasing characteristic curve obtained from the measured values in a force-displacement graph, an increasing cutting force is required due to increasing wear.

[0004] Patent Document 3 discloses a method for monitoring tool wear in a machine tool. This method includes first determining an allowable range of tool wear. Next, data of the cutting tool is detected from a typical machining area, for example, by detecting the cutting force depending on time. Then, in order to determine the wear depending on the allowable range, the coefficient of the characteristic curve is determined from the values in the machine area and compared with the actually detected data.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] The object of the present invention is to propose a method for monitoring the machining process in a machine tool and a machine tool, thereby enabling stable quality during the machining of a workpiece.

Means for Solving the Problems

[0007] This problem is solved by a method for monitoring the machining process in a machine tool. In this machining process, a machining tool including an upper tool and a lower tool preferably machines a plate-shaped workpiece. During each machining process, a time-synchronized process signal is detected by a sensor of the machine tool in a control device, and a process signal determined depending on time during the machining process is converted by conversion into a characteristic curve having a force-displacement curve, and this characteristic curve is drawn in a force-displacement graph without depending on time. From the course of the characteristic curve in the force-displacement graph, the wear of the machining tool and / or the material of the plate-shaped workpiece is determined. Based on the detection of a large number of process signals during the respective machining processes of the machining tool and the workpiece by the sensor of the machine tool, by an evaluation strategy using the conversion of the determined process signal into a characteristic curve drawn in a force-displacement graph without depending on time, the change of the process signal in the machining process is evaluated, particularly with respect to the wear of the machining tool and / or the material of the workpiece being machined. As a result, the machining quality of the workpiece, particularly the cut surface quality, can also be evaluated. The above control device can be provided inside the machine tool or outside the machine tool. Further, the control device also means that signals and / or acquired values are exchanged with a cloud network, or the evaluation is performed in a cloud network or a similar network.

[0008] Before the conversion of the process signal, it is preferable to remove the signal dispersion of the process signal determined from a plurality of consecutive machining processes. By removing this signal dispersion, an accurate evaluation of the force-displacement curve regarding wear and / or the determination of the material of the machined workpiece becomes possible, and as a result, the quality of the cut surface applied to the workpiece can also be determined.

[0009] For removing the signal dispersion, during the machining process, particularly during the stroke movement of the machining tool, it is advantageous to detect an additional displacement portion of the upper and / or lower tool by one or more sensors that determine the same or different signals, particularly at least one displacement sensor and / or at least one acceleration sensor.

[0010] Furthermore, preferably, in order to remove signal dispersion, elastic displacement portions of the machine frame of the processing machine can be detected by sensors such as displacement sensors and / or acceleration sensors. These elastic displacement portions of the processing tool and the machine frame lead to an extended displacement distance in the stroke movement of the processing tool in the processing machine, and the extended displacement distance is based on elastic deformation in the machine frame to which a force is applied, or results from machine parts to which a force is applied and a processing tool with an increased process force.

[0011] Furthermore, in order to remove signal dispersion, it is preferable to detect the difference in displacement portions of the upper and / or lower tools as a result of consecutive work cycles during a repeated processing process. In particular, such temporal drifts, or differences, can occur during the stroke movement of the processing tool as a result of the waiting time between two work cycles or between processing processes, and different accelerations, or speeds, in the movement of the upper and / or lower tools during the repeated process, which would falsify the evaluation of the process signal.

[0012] The additionally determined displacement portions are then evaluated by a regression function to determine the initial displacements of the upper and lower tools. This initial displacement is determined from the position displacement of the upper and / or lower tools as a result of the increased processing force of the processing machine, followed by subtraction or addition of the measured displacements of the stroke movement of the tool. Thereby, the dynamics of the tool and the processing machine can be almost frozen, and as a result, the signal dispersion of the processing signal caused by the dynamics of the processing machine and the tool can be removed.

[0013] Furthermore, the process signal with removed signal dispersion is preferably converted by transformation into a characteristic curve having a force-displacement curve in a force-displacement graph independent of time, with the initial displacement of the processing tool relative to the workpiece being processed as a reference. Alternatively, the elastic displacement portions of the machine frame can be represented by an analytical model of the machine parts and tool parts.

[0014] During the machining process, the stroke force is detected by at least one sensor of the machining machine, particularly a force sensor, the stroke movement of the upper tool and / or the lower tool is detected by at least one sensor, particularly a displacement sensor, and the displacement parts of the machine frame and the machining tool are detected by at least one acceleration sensor, each depending on the time of the respective machining process. From the process signals with the signal dispersion removed, it is preferably possible to represent, by conversion, a characteristic curve having a force-displacement curve in the force-displacement graph for the determination of tool wear. By considering and examining these parameters, an accurate evaluation of the force-displacement curve and, consequently, of the wear is possible.

[0015] In particular, it is preferable to determine the wear state of the machining tool from a comparison between a reference force-displacement curve using a non-worn machining tool and at least one force-displacement curve determined by the machining process. Thereby, an increase in the wear of the machining tool can be constantly monitored during the machining process, and the quality of the manufactured workpiece can also be mentioned.

[0016] For the upper and lower tools, the classification of the wear state is preferably determined jointly or individually, and the detected wear state is compared with the classification stored in the control device. Thereby, continuous monitoring of the increasing wear during machining is obtained, which can also be recorded for quality control. If the detected wear of the upper and / or lower tool deviates from a predetermined classification where the minimum requirements for the machining quality are met, preferably, a signal for tool replacement is output by the control device.

[0017] Furthermore, during the machining process, it is preferable to detect a sound signal in each machining process by at least one sound sensor, convert the sound signal into the frequency domain by Fourier transform, and then compare it with a reference value based on the amplitude in the frequency domain. The reference value is also based on the amplitude in the frequency domain. This comparison is used to verify the message from the characteristic curve of the force-displacement curve. During the machining of the workpiece, especially during punching, characteristic sound signals are generated for different materials of the workpiece being machined. These determined characteristic curves having a force-displacement curve from the detected process signal of the machining process are preferably compared with a reference force-displacement curve stored in the control device in order to be able to indicate which material is involved in the current machining process. This is particularly important for monitoring the machining process during automatic production in order to ensure that the correct workpiece material is provided as preparation for automatic production.

[0018] Furthermore, for a machining tool for the cutting process of cutting a workpiece piece from a workpiece, especially a plate-shaped workpiece, it is preferable to monitor the cutting surface quality determined from the direct correlation with the wear of the machining tool. When the wear of such a cutting machining tool, for example, a punch or a punch die, increases, a change occurs in the course of the cutting surface of the workpiece or the workpiece piece. Thereby, the quality of the cutting surface can be evaluated depending on the tool wear.

[0019] The underlying problem of the present invention is further solved by a processing machine provided for processing workpieces, particularly plate-shaped workpieces. This processing machine includes a processing tool having an upper tool, and the upper tool is movable along a stroke axis by a stroke drive in a direction towards the workpiece to be processed by the upper tool and in the opposite direction. Further, the upper tool is preferably positionable along an upper positioning axis extending perpendicular to the stroke axis and has a motor drive by which the upper tool is movable along the upper positioning axis. The processing tool further includes a lower tool, and the lower tool is aligned with the upper tool and is preferably movable along a lower stroke axis by a stroke drive in a direction towards the upper tool and in the opposite direction. The lower tool is positionable along a lower positioning axis oriented perpendicular to the stroke axis of the lower tool, and in particular, is movable along the lower positioning axis by a motor drive. The motor drives for the movement of the upper tool and the lower tool can be controlled by a control device connected to the processing machine. By means of the control device, any one of the processing machines of the above-described embodiments can be controlled for monitoring a processing process for processing a workpiece. Such a processing machine is preferably usable for automatic production. By detecting the state of the processing machine, the quality of the workpieces produced can be monitored throughout the entire automatic production process.

[0020] The present invention, as well as other advantageous and further embodiments, will be described in more detail hereinafter with reference to the examples shown in the drawings. The features derivable from the present specification and the drawings can be used individually or in any combination in accordance with the present invention.

Brief Description of the Drawings

[0021]

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DETAILED DESCRIPTION OF THE INVENTION

[0022] FIG. 1 shows a processing machine 1 formed as a punch press machine, for example. This processing machine 1 includes a support structure having a closed machine frame 2. The machine frame 2 includes two horizontal frame members 3, 4 and two vertical frame members 5, 6. The machine frame 2 surrounds a frame internal space 7, and this frame internal space 7 forms a working area of the processing machine 1 having an upper tool 11 and a lower tool 9.

[0023] The processing machine 1 is used for processing a plate-shaped workpiece 10, which is not shown in FIG. 1 for simplicity and can be placed in the inner space 7 of the frame for processing purposes. The workpiece 10 to be processed is placed on a workpiece support provided in the inner space 7 of the frame. In a recess of the workpiece support provided in the lower horizontal frame member 4 of the machine frame 2, a lower tool 9 in the form of, for example, a punch die is attached. The punch die can be provided with a die opening. During punching, the upper tool 11 formed as a punch penetrates into the die opening of the lower tool formed as a punch die.

[0024] The processing tools of the processing machine 1 include an upper tool 11 and a lower tool 9. Instead of a punch and a punch die, the upper tool 11 and the lower tool 9 can also be used as a bending punch and a bending die for shaping the workpiece 10.

[0025] The upper tool 11 is fixed to the tool holder at the lower end of the plunger 12. The plunger 12 is part of a stroke drive device 13, and by this stroke drive device 13, the upper tool 11 can be moved in the stroke direction along the stroke axis 14. The stroke axis 14 extends in the direction of the Z-axis of the coordinate system of the control device 15 of the processing machine 1 shown in FIG. 1. Perpendicular to the stroke axis 14, the stroke drive device 13 can move along the positioning axis 16 in the direction of the double arrow. The positioning axis 16 extends in the Y direction of the coordinate system of the control device 15. The stroke drive device 13 holding the upper tool 11 moves along the positioning axis 16 by a motor drive device 17.

[0026] The movement along the stroke axis 14 of the plunger 12 and the positioning along the positioning axis 16 of the stroke drive 13 are performed by the motor drive 17. The motor drive 17 has a drive spindle 18 extending in the direction of the positioning axis 16 and firmly connected to the machine frame 2, in particular in the form of a spindle drive. The stroke drive 13 is guided along three guide rails 19 of the upper frame member 3 during the movement along the positioning axis 16, two of which guide rails 19 can be seen in FIG. 1. The remaining one guide rail 19 extends parallel to the visible guide rail 19 and is spaced apart in the X-axis direction of the coordinate system of the numerical control device 15. The guide shoe 20 of the stroke drive 13 extends on the guide rail 19. The mutual engagement of the guide rail 19 and the guide shoe 20 is formed such that the connection between the guide rail 19 and the guide shoe 20 can also absorb the load acting in the vertical direction. Accordingly, the stroke device 13 is suspended from the machine frame 2 via the guide shoe 20 and the guide rail 19. A further component of the stroke drive 13 is, for example, a wedge mechanism 21, by means of which the position of the upper tool 11 relative to the lower tool 9 can be adjusted.

[0027] The lower tool 9 is movably mounted along a lower positioning axis 25. This lower positioning axis 25 extends in the direction of the Y-axis of the coordinate system of the numerical control device 15. Preferably, the lower positioning axis 25 is oriented parallel to the upper positioning axis 16. The lower tool 9 can be moved along the positioning axis 25 directly by the motor drive 26 at the lower positioning axis 25. Alternatively or additionally, the lower tool 9 can also be provided on a stroke drive 27 that can be moved along the lower positioning axis 25 by the motor drive 26. This drive 26 is preferably formed as a spindle drive. The lower stroke drive 27 can correspond to the structure of the upper stroke drive 13. Similarly, the motor drive 26 can correspond to the motor drive 17.

[0028] The lower stroke drive device 27 is similarly attached to the guide rail 19 assigned to the lower horizontal frame member 4 so as to be movable. The guide shoe 20 of the stroke drive device 27 extends on the guide rail 19, whereby the connection between the guide rail 19 and the guide shoe 20 in the lower tool 9 can also absorb the load acting in the vertical direction. Accordingly, the stroke drive device 27 is also suspended on the machine frame 2 via the guide shoe 20 and the guide rail 19 and at a distance from the guide rail 19 and the guide shoe 20 of the upper stroke drive device 13. Further, the stroke drive device 27 can include a wedge mechanism 21, and the position or height of the lower tool 9 can be adjusted along the Z axis by this wedge mechanism 21.

[0029] Alternatively, the upper and / or lower drive devices 13, 27 can also be formed using other drive components or drive concepts. For example, an electrically controllable drive mechanism or a mechanical drive concept can be provided. Also, a pneumatic or hydraulic drive concept can be used.

[0030] The control device 15 can control both the motor drive device 17 for moving the upper tool 11 along the upper positioning axis 16 and the motor drive device 26 for moving the lower tool 9 along the lower positioning axis 25 independently of each other. Thereby, the upper tool 11 and the lower tool 9 can be moved synchronously in the Y-axis direction of the coordinate system. Also, the independent movements of the upper and lower tools 11, 9 can be controlled in different directions. These independent movements of the upper and lower tools 11, 9 can be controlled simultaneously. By separating the movements between the upper tool 11 and the lower tool 9, an improvement in flexibility in the processing of the workpiece 10 can be achieved. The upper and lower tools 11, 9 can also be formed in various ways for the processing of the workpiece 10.

[0031] FIG. 2 shows a perspective view of an alternative embodiment of the processing machine 1 shown in FIG. 1. In this processing machine 1, for example, the structure of the machine frame 2 is different. In this processing machine 1, the machine frame 2 is formed in a C shape, that is, a vertical machine frame 5 is provided between an upper horizontal frame member 3 and a lower horizontal frame member 4. An upper tool 11, for example, is provided at the open end of the upper horizontal machine member 3. Conversely, a lower tool 9 is provided at the open end of the lower horizontal frame member 4 and is adjacent to the upper tool 11. In addition to or instead of the upper tool 11, a cutting head 28 for laser cutting or plasma cutting, for example, can be provided on the upper horizontal frame member 3. Instead of and / or in addition to the upper and lower tools 11, 9, a bending tool can also be provided.

[0032] The processing machine 1 of the displaceable embodiment is provided with a plurality of sensors. By means of these sensors, various signals can be detected during the processing of the workpiece 10 by the processing machine 1. These sensors are preferably arranged in an effective direction in which signals are detected. In order to detect the bending stress of the machine frame 2 or, for example, the expansion of the C-shaped machine frame in the vertical frame member 6, the sensor can be formed as a strain gauge, for example. The sensor can also detect signals of driving forces such as current and / or voltage generated during the movement and / or stroke movement of the upper and / or lower tools 11, 9. In the case of hydraulic drive, the sensor can also detect the pressure curve in the pressure chamber generated during the working stroke. The sensor can also detect various sound levels in order to determine and monitor data. The selection and use of each sensor are determined and analyzed depending on the process signals to be monitored for the processing process in the processing machine. For example, at least one displacement sensor 29 is provided on and / or in the upper tool 11 and / or the lower tool 9 in order to detect the stroke movement of the upper tool 11 and / or the lower tool 9. Furthermore, at least one force sensor 31 can be provided on the upper tool 11 and / or the lower tool 9 in order to detect the force acting on the workpiece 10. Furthermore, at least one sound sensor 32 can be provided on the machine frame 2. Furthermore, one or more acceleration sensors 33 can be provided on the machine frame 2, the upper tool 11 and / or the lower tool 9. When the C-shaped machine frame 2 is provided, at least one acceleration sensor 33 is preferably arranged in the region of the free ends of the upper and lower horizontal frame members 3, 4.

[0033] FIG. 3 shows a schematic side view of the upper tool 11 and a schematic cross-sectional view of the lower tool 9. In this embodiment, it is a cutting tool or a punching tool. The upper tool 11 includes a body 35 having a clamp pin 36. A cutting tool 37 having a stamp surface or a punch surface 38 is formed on the body 35, and this cutting tool 37 is surrounded by a cutting edge 39 over the entire circumference. The lower tool 9 is formed as a die, particularly a perforated die. A through hole 42 is provided in the body 41 of the lower tool 9. A cutting edge 46 is provided at the transition portion from the through hole 42 to the support surface 44 of the workpiece 10, and a cutting surface 47 that joins the through hole 42 with an enlarged periphery is connected to this cutting edge 46.

[0034] FIG. 4 shows an alternative embodiment of the upper tool 11 and the lower tool 9 with respect to the embodiment shown in FIG. 3. In this embodiment, the length of the cutting edge 46 of the lower tool 9 is different from the length and / or shape of the cutting edge 39 of the upper tool 11. From this embodiment, it is shown that, for example, the cutting edge 46 can be provided inside the through hole 42 on the die 9, and can also be provided outside the through hole 42. Further, the upper tool 11 may include a square punch surface or stamping surface, or a circular punch surface, or other free-form shapes instead of the rectangular punch surface 38.

[0035] Both the cutting edge 39 of the upper tool 11 and the cutting edge 46 of the lower tool 9 wear. The wear of the upper and lower tools 11, 9 has an adverse effect on the cutting quality or the processing quality of the workpiece 10. During a number of consecutive processing processes 49 (see FIG. 5), particularly during automatic production, in order to achieve stable processing quality, monitoring of the processing process 49, which will be described in detail below, is carried out. At the same time, by monitoring the processing process 49, it becomes possible to actively adjust the parameters of the processing process 49 by the control device 15 based on the obtained information, and thereby perform automated improvements even during automatic production.

[0036] The monitoring method described below can determine the wear of the upper and lower tools 11 and 9. It is also possible to examine and determine which material of the workpieces 10 being processed, particularly the plate-shaped workpieces, forms the basis. Furthermore, when further processing is planned for the workpiece pieces 8, and the residual grids generated from the workpiece 10 thereby function as waste, it is also possible to mention the cut surface quality of the workpiece pieces 8 cut out from the workpiece 10. Also, it is possible to mention the cut surface quality of the workpiece 10 from which one or more workpiece pieces 8 have been separated or cut off as waste. At that time, the processing of the workpiece 10 can include blanking, punching, cutting, trimming, etc.

[0037] FIG. 5 shows a schematic graph displaying process signals synchronized in time for, for example, three consecutive machining processes 49. This machining process 49 relates to, for example, the punching of a workpiece 10 using a punch tool as shown in FIG. 3. During the machining process 49, before subsequent strokes of the upper tool 11 and / or the lower tool 9 are controlled, for example, until the plate-shaped workpiece 10 is moved to a new machining position and / or until the upper tool 11 and the lower tool 9 are moved to corresponding machining positions, there is a waiting time or idle time 50 for the upper and lower tools 11, 9. The graph shows a plurality of process signals synchronized in time, and each process signal is detected by a sensor. The process signal 52 can detect, for example, the stroke movement of the upper tool 11 by a displacement sensor 29. This is particularly applicable when only the upper tool 11 is controlled by a stroke movement. The process signal 53 indicates, for example, the force determined by a force sensor 31 during the cutting process. The process signal 54 is obtained, for example, by an acceleration sensor 33 and indicates the displacement portion during the expansion of the machine frame 2 during the machining process 49. The process signal 55 is determined by a sound sensor 32. The process signals 56 and / or 57 and / or 58 are each detected by an acceleration sensor 33. The acceleration sensor 33 can detect the displacement portion in the X, Y, and / or Z directions of the machine frame 2. The names of the individual sensors for detecting the process signals 52 to 58 are merely exemplary, and it is understood that data or information can also be calculated and determined by other sensors from the detected process signals.

[0038] FIG. 6 shows a displacement-time graph of the upper tool 11 from, for example, a superposition of a number of characteristic curves of the machining process 49. The approach movement of the upper tool 11 towards the workpiece 10 starts at time t1. The upper tool 11 hits the workpiece 10 at time t2. The cutting process ends at time t3. From this, it can be seen that, at the start of the cutting process, for example, a signal dispersion of 10% can already occur. In the cutting region near time t3, for example, a signal dispersion of 40% may be present. The signal dispersion is caused by interference, and as a result, changes occur during the machining of the workpiece, which has an adverse effect on the machining quality. These signal dispersions affect the evaluation of the process signals and are removed as described below.

[0039] FIG. 7 shows the characteristic curves in the force-time graph of a plurality of machining processes 49, simultaneous with the stroke displacement according to FIG. 6, during the stroke movement of the upper tool 11 with respect to the workpiece 10 and during punching. From the increase in force at time t2, the start of the cutting process can be recognized. Even at this point already, there is, for example, a force signal dispersion of 15% in the applied force, that is, the time when the upper tool 11 contacts the workpiece 10 is not the same in the time series during a plurality of successive machining steps. In such a time series, signal dispersions that are not actually observable are visualized. The same applies to the time t3 when the workpiece 10 is cut.

[0040] The signal dispersions shown in FIGS. 6 and 7 for a number of successive machining processes 49 are based on the following facts. That is, in particular, as a result of the elastic deformation of the upper and / or lower tools 11, 9 loaded with force, and of the machine frame 2, additional displacement portions of the upper and lower tools 11, 9, and elastic displacement portions of the machine frame 2 result in longer stroke displacements in the stroke movement of the upper and / or lower tools 11, 9. Furthermore, as a result of the waiting time 50 during the machining process 49, a temporal shift or difference occurs in the stroke movement of the upper and / or lower tools 11, 9. This temporal difference is caused, for example, by the changing response behavior of the electric motor, the filling level of the hydraulic buffer storage provided in the processing machine 1, and the like.

[0041] FIG. 8 shows, for example, the stroke displacement of the upper tool 11 together with the elastic displacement portion of the machine frame 2. The Y-axis represents the elastic displacement portion of the machine frame 2, and the displacement portion is depicted over time along the X-axis. The characteristic curve 58 shows, for example, the displacement portion detected by a displacement measurement detectable by a sensor.

[0042] FIG. 9 shows a graph similar to FIG. 8, where, for example, the elastic displacement portion detected by the acceleration sensor 33 has been removed in the machine frame 2. For example, the first bend of the characteristic curve 58 at time t4 indicates the impact of the upper tool 11 against the workpiece 10, while the subsequent bend of the characteristic curve 58 at time t5 indicates the penetration of the upper tool 11 into the workpiece 10. The elastic portion of the machine frame 2 can also be measured directly from the value of the characteristic curve 58, or can be determined as a regression function by an analytical model of the elastic component. By adding or subtracting the displacement portion of the machine frame 2, only this signal dispersion can be removed from the characteristic curve 58. This step can also be referred to as freezing the tool dynamics and machine dynamics, or removing the tool dynamics and machine dynamics. For example, the same applies to the process signal 53 showing the cutting force curve during the machining process 49.

[0043] Based on this, the removal of the time-dependence of the process signals 55 - 58 is performed by converting the characteristic curve 58 of the displacement-time graph into a force-displacement graph. FIG. 10 shows such a force-displacement curve of the characteristic curve 59 obtained by this conversion. By making the process signals 55 - 58 synchronized in time according to FIG. 5 independent of time, the transitions of the characteristic curve 59 of each machining process, particularly the bending process or the cutting process, become more comparable. Thereby, under certain workpiece and tool conditions, the same work, i.e., the same force per displacement, is required for each moving displacement, so that the variation of the characteristic curve 59 can be reduced.

[0044] By removing the time-dependence, it becomes possible to accurately evaluate the force-displacement curves of the upper and / or lower tools 11, 9 with respect to wear and, preferably, with respect to the quality of the produced cut surface.

[0045] FIG. 11 shows, for example, a force-displacement graph in which a plurality of force-displacement curves of characteristic curves are assigned to each other. Displacement, in particular punch displacement, is depicted along the X-axis, and cutting force is depicted along the Y-axis. This graph according to FIG. 11 serves to show the detected wear of the upper tool 11 and / or lower tool 9 and / or the machining tool with respect to the upper and / or lower tools 11, 9 and / or the machining tool without wear.

[0046] FIG. 12 schematically shows the cutting edge 39 of the upper tool 11 and the cutting edge 46 of the lower tool 9 in an enlarged view. When the upper tool 11 and the lower tool 9 are still unused, the cutting edges 39 and 46 are formed, for example, at a right angle and particularly with a pointed corner as shown by the solid line. During the process of use, these cutting edges 39, 46 wear. At that time, these cutting edges 39, 46 become rounded as shown by the broken line 40. The cutting edge 39 of the upper tool 11 wears much more severely and faster than the cutting edge 46 of the lower tool 9 at that time.

[0047] FIG. 13 shows an enlarged schematic cross-sectional view of the cutting edges of the upper and lower tools 11, 9 during the machining process. During this machining process, the workpiece piece 8 is cut from the workpiece 10 by punching with the upper and lower tools 11, 9. The cutting edge 39 of the upper tool 11 and the cutting edge 46 of the lower tool 9 are not worn. In this case, the following cutting surface characteristics are obtained on the workpiece 10 or the workpiece piece 8. The height hE of the edge draw-in part (Kanteneinzug) is small. The width bE of the edge draw-in part is also small and slightly rounded. Subsequently, the height hS of the smooth cut part (Glattschnitt) extends, and subsequently, the height hB of the fracture zone (Bruchzone) exists. At the lower end of the workpiece 10 or the workpiece piece 8, only the height hG of a slight cutting burr (Schnittgrat) exists. The relationship between the workpiece piece 8 and the workpiece 10 along the cut surface is shown to be approximately similar but mirror-imaged.

[0048] Figure 14 shows a schematic cross-sectional view similar to that of Figure 13. In contrast, the cutting edges 39 of the upper tool 11 and the cutting edge 46 of the lower tool 9 each have wear 40, as indicated by the dashed line 40 in Figure 12, for example. As a result, the cutting surface characteristics change as follows. The width bE and the height hE of the edge drawing-in portion increase significantly. The height hS of the smooth cutting portion increases, and the height hB of the fracture zone decreases. At this time, an increase in the wear of the cutting edge 46 of the lower tool 9 causes an increase in the height hG of the cutting burr. In particular, this results in the formation of a significant burr on the workpiece piece 8. When such a cutting result occurs, the upper and / or lower tools 11, 9 must be replaced.

[0049] The states of the upper tool 11 and the lower tool 9 described with reference to FIGS. 13 and 14 can be seen in the characteristic curve of FIG. 11. The characteristic curve 60 shows the force-displacement curves of the upper tool 11 and the lower tool 9 without wear, that is, having a shape according to the solid line in FIG. 12. The characteristic curves 62, 63, 64, 65 located in the range 61 show an increase in wear of the cutting edge 39 of the upper tool 11. At this time, for example, the characteristic curve 64 accompanying an increase in punch displacement is characterized by an increase in wear compared to the characteristic curves 63 or 62. The characteristic curves in the range 66 represent the wear of the lower tool 9. For example, the characteristic curve 67 shows less wear than the other characteristic curves 68, 69 on its right side. The characteristic curves 62, 63, 64, 65 of the upper tool 11 are, for example, subdivided into three classifications. The characteristic curve 62 shows the wear of Class 1 with a roundness of 0.25 mm, and the characteristic curve 63 shows the wear of the upper tool of Class 2 with a roundness of, for example, 0.5 mm. The same applies to the lower tool 9. In the characteristic curve 67, the roundness of the wear of the Class 1 tool is only 0.025 mm. The characteristic curve 68 shows the wear of the lower tool of Class 2 with a roundness of, for example, 0.05 mm. The characteristic curve 71 shows the upper tool 11 and the lower tool 9 with wear superimposed according to the characteristic curves 62 and 67, for example. The characteristic curve 72 shows the superimposition of the wear of the upper tool 11 and the lower tool 9 by the characteristic curves 63 and 67. Thereby, by comparison with the characteristic curve 60 showing the state without wear of the upper tool 11 and / or the lower tool 9, the increase in wear of the upper tool 11 and / or the lower tool 9 can be determined individually, and evaluation can be performed according to a predetermined classification.

[0050] For recognition of the material or plate thickness, a similar force-displacement graph according to FIG. 11 can be created based on the process signal 55 determined by the sound sensor 32. For example, the characteristic curves determined for aluminum, steel, or stainless steel are different from each other.

Explanation of Signs

[0051] 1 Processing machine 2 Machine frame 3 Horizontal Frame Member 4 Horizontal Frame Member 5 Vertical Frame Member 6 Vertical Frame Member 7 Frame Interior Space 8 Work Piece 9 Lower Tool 10 Work 11 Upper Tool 12 Plunger 13 Stroke Drive Device 14 Stroke Shaft 15 Control Device 16 Upper Positioning Shaft 17 Motor Drive Device 18 Drive Spindle 19 Guide Rail 20 Guide Shoe 21 Wedge Mechanism 25 Lower Positioning Shaft 26 Motor Drive Device 27 Stroke Drive Device 29 Displacement Sensor 31 Force Sensor 32 Sound Sensor 33 Acceleration Sensor 35 Main Body 36 Clamp Pin 37 Cutting Tool 38 Punch Surface 39 Cutting Edge 40 Worn Cutting Edge 41 Main Body 42 Through-Hole 44 Support Surface 46 Cutting Edge 47 Cutting Surface 49 Machining Process 50 Waiting Time 52 Process Signal 53 Process Signal 54 Process Signal 55 Process Signal 56 Process Signal 58 Characteristic Curve 60 Characteristic Curve of Upper Tool 61 Range 62 Characteristic Curve 63 Characteristic Curve 64 Characteristic Curve 65 Characteristic Curve of Lower Tool 66 Range 67 Characteristic Curve 68 Characteristic Curve 69 Characteristic Curve 71 Characteristic Curve 72 Characteristic Curve

Claims

Claim 1 A method for monitoring a machining process (49) in a machine tool (1), comprising: in the machining process (49), machining a workpiece (10) with a machining tool including an upper tool (11) and a lower tool (9); during each machining process (49), detecting time-synchronized process signals (52, 53, 54, 55, 56, 57, 58) by sensors (29, 31, 32, 33) of the machine tool (1) and transmitting them to a control device (15); converting the process signals (52, 53, 54, 55, 56, 57, 58) determined depending on time during the machining process (49) by conversion into characteristic curves (59, 60, 62, 63, 64, 65, 67, 68, 69, 71, 72) having a force-displacement curve, the characteristic curves being drawn in a force-displacement graph and not depending on time; determining the wear of the machining tools (11, 9) separately from each other from the course of the characteristic curves (59, 60, 62, 63, 64, 65, 67, 68, 69, 71, 72) in the force-displacement graph and / or determining the material of the workpiece (10) underlying at least one of the machining processes (49); removing the signal dispersion of the process signals (52, 53, 54, 55, 56, 57, 58) determined from a plurality of consecutive machining processes (49) in the control device (15); for removing the signal dispersion, detecting an elastic displacement portion of a machine frame (2) of the machine tool (1) during a stroke movement of the upper and / or lower tool (11, 9) by at least one sensor; a method of removing only the signal dispersion from the characteristic curve by adding or subtracting the detected displacement portion. Claim 2 The method according to claim 1, characterized in that for removing the signal dispersion, detecting a displacement portion of the upper and / or lower tool (11, 9) to which a force is applied during the machining process (49) by at least one sensor, and removing only the signal dispersion from the characteristic curve by adding or subtracting the detected displacement portion. Claim 3 For removing the signal dispersion, the difference in the displacement portions of the upper and / or lower tools (11, 9) is detected as a result of the waiting time (50) during the processing process (49) in the repeated processing process (49), and only the signal dispersion is removed from the characteristic curve by adding or subtracting the detected difference in the displacement portions. The method according to claim 2, characterized in that.

4. The detected displacement portions are evaluated by a regression function to determine the initial displacements of the upper and lower tools (11, 9), or The method according to claim 2 or 3, characterized in that the elastic displacement portion of the machine frame (2) is represented by an analytical model of mechanical parts and tool parts.

5. The process signals (52, 53, 54, 55, 56, 58) with the signal dispersion removed are converted by conversion into characteristic curves (59, 60, 62, 63, 64, 65, 67, 68, 69, 71, 72) having a force-displacement curve in a force-displacement graph that is independent of time, In this case, the initial displacement is determined by a regression function for the position displacement of the upper tool (11) and the lower tool (9) based on the subtraction or addition of the position displacement of the upper and / or lower tools by the processing force and the measured displacements of the upper tool (11) and the lower tool (9), and is assigned to the force-displacement curve of the characteristic curve (59, 60, 62, 63, 64, 65, 67, 68, 69, 70, 71, 72). The method according to claim 4, characterized in that.

6. During the processing process (49), the stroke force is detected by at least one force sensor (31), the stroke movement of the upper and / or lower tools (11, 9) is detected by at least one displacement sensor (29), and the displacement portion of the machine frame (2) is detected by at least one acceleration sensor (33) as a function of time for each of the processing processes (49), Removing the signal dispersion from the process signals (52, 53, 54, 56, 57, 58) and, by one conversion, using the force-displacement curve of the characteristic curve (59) as a basis for determining the wear of the processing tools (11, 9). The method according to any one of claims 1 to 3, characterized in that.

7. Determining the wear state of the upper and / or lower tool (11, 9) from a comparison between a reference force-displacement curve of the characteristic curve (60) of the non-wearing upper and lower tools (11, 9) and a force-displacement curve determined from the processing process (49) of the characteristic curve (62, 63, 64, 65) of the upper tool (11) and / or the characteristic curve (67, 68, 69) of the lower tool (9), the method according to claim 1 or 2.

8. Determining the classification of the wear state separately or jointly for the upper tool (11) and the lower tool (9), Comparing the wear state detected by the characteristic curves (62, 63, 64, 65; 67, 68, 69, 71, 72) with the classification, Instructing tool change by the control device (15) when the detected wear state deviates from an acceptable classification, the method according to claim 7.

9. Determining the wear state of the upper and / or lower tool (11, 9) from a comparison between a reference force-displacement curve of the characteristic curve (60) of the non-wearing upper and lower tools (11, 9) and an overlay of the determined force-displacement curves of the characteristic curves (71, 72) of the upper tool (11) and the lower tool (9), the method according to claim 1 or 2.

10. During the processing process (49), detecting a sound signal by at least one sound sensor (32), converting it into the frequency domain by Fourier transform, and then comparing it with a reference value based on the amplitude in the frequency domain, the method according to claim 1 or 2.

11. For the upper and lower tools (11, 9) for a processing process (49) including a cutting process of cutting a workpiece piece (8) from a workpiece (10), monitoring the cutting surface quality determined from the direct correlation with the wear of the upper tool (11) and the lower tool (9), the method according to claim 1 or 2.

12. A processing machine for processing a workpiece (10), An upper tool (11) movable by a stroke drive device (13) along a stroke axis (14) in a direction towards and in the opposite direction of the workpiece (10) to be processed by the upper tool (11), an upper tool (11), A lower tool (9) aligned with the upper tool (11) and movable by a stroke drive (27) in a direction towards the upper tool (11) along a lower stroke axis and in the opposite direction thereto, A control device (15), and the control device enables at least the upper tool (11) and / or the lower tool (9) to be controllable for a stroke motion, in a processing machine, The control device (15) is configured to execute a method for monitoring a machining process (49) in a processing machine (1) according to claim 1 or 2, characterized in that, a processing machine.

13. Characterized by comprising a closed machine frame (2) or a C-shaped machine frame, The processing machine according to claim 12.

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