machine tools

Abstract

A machine tool rotates its spindle via a rotary mechanism, and simultaneously vibrates and moves the workpiece and the tool relative to each other via a moving mechanism and a vibration mechanism to cut the workpiece. The machine tool has a means of determining the degree of wear on the tool tip by measuring the difference between the component of the force acting on the workpiece and the component of the force parallel to the direction of movement caused by the moving mechanism, based on the force of the relative vibration of the workpiece and the tool on the outward path and the return path.

Description

machine tools This invention relates to a machine tool. In machine tools, understanding the wear level of tool tips is crucial for improving machining accuracy. To avoid reduced efficiency due to repeated interruptions in machining to observe wear, it is ideal to monitor wear during the machining process. Therefore, a technique is known that incorporates various sensors to predict wear levels based on sensor readings (see Patent Documents 1-5). However, due to space constraints and other issues, it can be difficult to configure sensors at times, and the prediction accuracy may also decrease depending on the usage environment. Therefore, there is still room for improvement. [Patent Documents] [Patent Document 1] Japanese Patent Application Publication No. 2000-94273. [Patent Document 2] Japanese Patent Application Publication No. 2000-135605. [Patent Document 3] Japanese Patent Application Publication No. 2001-37567. [Patent Document 4] Japanese Patent Application Publication No. 2005-125480. [Patent Document 5] Japanese Patent Application Publication No. 2021-130159. The purpose of this invention is to provide a machine tool that can appropriately control the wear level of the tool tip during processing. The present invention employs the following means to solve the aforementioned problem. That is, the machine tool of the present invention comprises: a spindle on which a workpiece is mounted; a rotating mechanism for rotating the spindle; a tool for cutting the workpiece; a moving mechanism for moving the spindle and the tool relative to each other; and a vibrating mechanism for vibrating the spindle and the tool relative to each other in a direction parallel to the direction of movement caused by the moving mechanism; the machine tool cuts the workpiece by rotating the spindle through the rotating mechanism and vibrating and moving the workpiece and the tool relative to each other through the moving mechanism and the vibrating mechanism; the machine tool comprises a determination means for determining the degree of wear of the tool tip by measuring the difference between the component of the force on the tool from the workpiece in the direction parallel to the direction of movement, in terms of the component of the force in the direction of movement of the relative vibration of the workpiece and the tool. According to the present invention, the degree of wear on the tool tip can be determined by the difference between the component forces of the relative vibrations of the cutting object and the tool during the outward and inward paths. That is, the degree of wear can be determined simply by measuring the component forces. This determination method can determine the degree of wear on the tip of the tool by measuring the difference between the component force on the outgoing path and the component force on the returning path when the cutting thickness in the direction parallel to the moving direction of the object being cut is within a predetermined range. This can improve the accuracy of determining the degree of wear. The relationship between the difference and the degree of wear is pre-defined, and the determination method will determine the degree of wear according to the pre-defined relationship. It can have a notification method that, when the wear level has been determined by the determination method to have exceeded a preset threshold, informs the outside world that the wear of the tool has exceeded a predetermined amount. This allows operators to know when the wear level has exceeded a pre-set threshold. If the determination method confirms that the wear level has exceeded the preset threshold, the cutting action will be stopped. This prevents worn-out tools from being used in machining and also prevents a decrease in machining accuracy. The threshold can be set according to the alignment of the track in the direction parallel to the direction of movement relative to the rotation direction of the object being cut relative to the tip of the tool, and the track angle between the track and the plane perpendicular to the direction of movement. This allows for the setting of a more appropriate threshold. The threshold can be set according to the difference in the initial state of the tool's use. This allows for the setting of a more appropriate threshold. It can be equipped with a threshold setting method, which means that when the wear level is determined by the judgment method to exceed the preset threshold, the cutting action will be temporarily stopped, and the threshold will be reset after the temporary stop. This allows the threshold to be reset according to the level of wear and tear that the operator can tolerate. The threshold setting method can set the difference between the allowable wear amount input by the operator and the wear amplitude of the tool from the initial stage of use as the threshold. The moving mechanism comprises: a first moving mechanism for moving the spindle and the tool relative to each other in the axial direction of the spindle; and a second moving mechanism for moving the spindle and the tool relative to each other in a direction perpendicular to the axial direction; the vibration mechanism comprises: a first vibration mechanism for vibrating the spindle and the tool relative to each other in the axial direction of the spindle; and a second vibration mechanism for vibrating the spindle and the tool relative to each other in a direction perpendicular to the axial direction; the vibration mechanism further comprises: a first cutting mode in which, while rotating the spindle via the rotating mechanism, the object to be cut and the tool are vibrated relative to each other and moved in the axial direction of the spindle via the first moving mechanism and the first vibration mechanism; and a second cutting mode in which, while rotating the spindle via the rotating mechanism, the object to be cut and the tool are vibrated relative to each other and moved in a direction perpendicular to the axial direction via the second moving mechanism and the second vibration mechanism, for cutting the object to be cut. It may have: a measuring means, which measures the force exerted on the tool from the object being cut in order to derive the difference. This measurement method can measure the force exerted on the tool from the object being cut by measuring the current value of the motor driving the moving mechanism. Furthermore, the machine tool of the present invention comprises: a spindle on which a workpiece is mounted; a rotating mechanism for rotating the spindle; a tool for cutting the workpiece; a moving mechanism for moving the spindle and the tool relative to each other; a vibrating mechanism for vibrating the spindle and the tool relative to each other in a direction parallel to the moving direction of the moving mechanism; and a motor for driving the moving mechanism. The machine tool rotates the spindle via the rotating mechanism while simultaneously vibrating and moving the workpiece and the tool relative to each other via the moving mechanism and the vibrating mechanism to cut the workpiece. The machine tool includes a determination means for determining the degree of wear on the tool tip based on the difference between the current value generated by the motor during the relative vibration of the workpiece and the tool when the spindle and the tool move relative to each other, in terms of the current value generated by the motor. According to the present invention, the degree of wear on the tip of the tool can be determined by the difference between the current value of the motor during the outward vibration of the cutting object and the tool and the current value of the motor during the return vibration. That is, the degree of wear can be determined simply by obtaining the motor current value. This determination method can determine the degree of wear on the tool tip by measuring the difference between the current value on the outgoing path and the current value on the returning path when the cutting thickness in the direction parallel to the moving direction of the object being cut is within a predetermined range. This can improve the accuracy of determining the degree of wear. The relationship between the difference and the degree of wear can be pre-defined, and the determination method will determine the degree of wear according to the pre-defined relationship. This allows the degree of wear to be determined based on the pre-defined relationships. Furthermore, the above structures can be combined to the extent possible and thus adopted. As explained above, according to the present invention, the degree of wear on the tool tip can be appropriately controlled during processing. Hereinafter, with reference to the accompanying drawings, embodiments will be described in detail illustratively. However, unless otherwise specified, the dimensions, materials, shapes, and relative arrangements of the structural components described in these embodiments are not intended to limit the scope of the invention to these. (Example) Referring to Figures 1 to 11, a machine tool related to an embodiment of the present invention will be described. In Figures 1 to 3, for ease of explanation, three mutually orthogonal axes (X-axis, Y-axis, and Z-axis) are illustrated. The axis of the spindle 110 is the Z-axis, and the X-axis and Y-axis are mutually orthogonal and perpendicular to the Z-axis. <Structure of the Machine Tool> The structure of the machine tool 10 according to an embodiment of the present invention will be described with reference to FIG1. ​​FIG1 is a schematic structural diagram of the machine tool 10 according to an embodiment of the present invention, and is a diagram that simply shows the structure of each part. The machine tool 10 includes a spindle 110 on which a workpiece W is mounted, a rotating mechanism 120 for rotating the spindle 110, and a tool (cutting tool) 210 for cutting the workpiece W. The tip of the spindle 110 is provided with a clamp for holding the workpiece W. The rotating mechanism 120 can employ various conventional technologies such as motors. Furthermore, the machine tool 10 has a moving mechanism that moves the spindle 110 and the tool 210 relative to each other. In this embodiment, the moving mechanism includes a first moving mechanism 130 and a second moving mechanism 220. The first moving mechanism 130 moves the spindle 110 and the tool 210 relative to each other in the axial direction (Z-axis direction) of the spindle 110. The second moving mechanism 220 moves the spindle and the tool 210 relative to each other in a direction perpendicular to the Z-axis direction (X-axis direction). Various conventional technologies, such as linear servo motors, ball screw mechanisms, or rack and pinion mechanisms, can be used as these moving mechanisms. Furthermore, the machine tool 10 includes a vibration mechanism that causes the spindle 110 and tool 210 to vibrate relative to each other in a direction parallel to the direction of movement of the moving mechanism. In this embodiment, the vibration mechanism includes a first vibration mechanism 140 and a second vibration mechanism 230. The first vibration mechanism 140 causes the spindle 110 and tool 210 to vibrate relative to each other in the axial direction (Z-axis direction) of the spindle 110. The second vibration mechanism 230 causes the spindle 110 and tool 210 to vibrate relative to each other in a direction perpendicular to the Z-axis direction (X-axis direction). These vibration mechanisms can employ various conventional techniques capable of causing the vibrating object to reciprocate. The first vibration mechanism 140 is fixed to a movable stage 131 configured to move in the Z-axis direction via the first moving mechanism 130. Then, the rotation mechanism 120, which rotates the spindle 110 via the first vibration mechanism 140, is configured to vibrate in the Z-axis direction. With this structure, the workpiece W is configured to move in the Z-axis direction via the first moving mechanism 130 (refer to arrow S1), and while being configured to vibrate in the Z-axis direction via the first vibration mechanism 140 (refer to arrow T1), it is also configured to rotate via the rotation mechanism 120 (refer to arrow R). The second vibration mechanism 230 is fixed to a moving stage 221 configured to move in the X-axis direction via the second moving mechanism 220. Therefore, the tool 210 is configured to move in the X-axis direction via the second moving mechanism 220 (refer to arrow S2) and to vibrate in the X-axis direction via the second vibration mechanism 230 (refer to arrow T2). Furthermore, in this embodiment, a measuring device 240 is provided as a measuring means to measure the force exerted by the tool 210 on the object being cut, W. However, the means of measuring the force exerted by the tool 210 on the object being cut, W, is not limited to the measuring device 240. For example, the force can be measured by utilizing the variation in the current value of the servo motor used by the moving mechanism due to the cutting load, or by using an estimation method based on a disturbance observer. In this embodiment, when the force is measured using the current value of the servo motor used by the moving mechanism, for example, the force in the Z-axis direction experienced by the tool 210 can be measured using the current value of the servo motor of the first moving mechanism 130 that drives the object to be cut W in the Z-axis direction. Furthermore, for example, the force in the X-axis direction experienced by the tool 210 can be measured using the current value of the servo motor of the second moving mechanism 220 that drives the tool 210 in the X-axis direction. Then, the machine tool 10 is equipped with a control device C, which performs calculations on the data obtained from the measuring device 240 while controlling the operation of the various mechanisms. Furthermore, the machine tool 10 is equipped with an input means 311 for the operator to input processing conditions and other input data into the control device C, and a notification means 312 for informing the operator of the various data obtained through the control device C. Specific examples of the input means 311 include a keyboard, a small keyboard, and a mouse. Specific examples of the notification means 312 include a loudspeaker that emits light and sound, and a display that shows images. Furthermore, in this embodiment, in order to move the cutting object W and the tool 210 relative to each other in the two-axis direction, the configuration is such that the cutting object W can be moved and vibrated in the Z-axis direction, and the tool 210 can also be moved and vibrated in the X-axis direction. However, by fixing the tool 210 and enabling the cutting object W to move and vibrate in the two-axis direction, the cutting object W and the tool 210 can be moved and vibrated relative to each other in the two-axis direction. Similarly, by fixing the cutting object W and enabling the tool 210 to move and vibrate in the two-axis direction, the cutting object W and the tool 210 can be moved and vibrated relative to each other in the two-axis direction. Furthermore, in this embodiment, a structure is shown in which the moving mechanism and the vibration mechanism are provided independently, and the latter are controlled and operated independently. However, a structure that combines the functions of both the moving mechanism and the vibration mechanism can be adopted. For example, by using a linear servo motor to control the linear servo motor to move and vibrate the cutting object W or the tool 210, the same operation as in the case where the moving mechanism and the vibration mechanism are provided and operated independently can be performed. Furthermore, in this embodiment, a structure is shown in which the object to be cut, W, and the tool 210 move relative to each other and vibrate in the two-axis direction. However, a structure in which the object to be cut, W, and the tool 210 move relative to each other and vibrate in the three-axis direction can also be adopted. That is, in addition to the structure described above, a structure in which the object to be cut, W, and the tool 210 move relative to each other and vibrate in the Y-axis direction can be further provided. With the machine tool 10 structured as described above, the spindle 110 can be rotated via the rotary mechanism 120, while the workpiece W and the tool 210 can be vibrated and moved relative to each other via the moving mechanism and the vibration mechanism, thereby cutting the workpiece W. In the machine tool 10 of this embodiment, at least cutting operations caused by a first cutting mode and cutting operations caused by a second cutting mode can be performed. This will be explained below. <Cutting Modes> Referring to Figures 2 and 3, the cutting modes will be explained. Figures 2 and 3 are operational descriptions of the cutting modes in a machine tool related to embodiments of the present invention. Figure 2 shows the operation in the first cutting mode. Figure (a) shows the cutting object W and tool 210 viewed from the Y-axis direction, and Figure (b) shows their views from the Z-axis direction. Figure 3 shows the operation in the second cutting mode. Figure (a) shows the cutting object W and tool 210 viewed from the Y-axis direction, and Figure (b) shows their views from the Z-axis direction. First, the cutting action in the first cutting mode will be explained with reference to FIG2. In this case, the spindle 110 is rotated by the rotary mechanism 120, while the object to be cut, W, and the tool 210 are vibrated and moved relative to each other in the Z-axis direction by the first moving mechanism 130 and the first vibration mechanism 140 to perform cutting. The operator only needs to input the number of rotations of the spindle 110 per unit time, the feed rate caused by the first moving mechanism 130 (the feed rate in the direction of arrow S1 in FIG2), the radial cutting width, and the vibration frequency and amplitude caused by the first vibration mechanism 140 into the input means 311. In addition, the input data can be set to directly input various data or indirectly input various data. That is, it can also be set not to directly input the required data, but to input data that can be derived from calculation. Referring to Figure 3, the cutting action in the second cutting mode will be explained. In this case, the spindle 110 is rotated by the rotary mechanism 120, while the object to be cut, W, and the tool 210 vibrate and move relative to each other in the X-axis direction via the second moving mechanism 220 and the second vibration mechanism 230 to perform cutting. The operator only needs to input the number of rotations of the spindle 110 per unit time, the feed rate caused by the second moving mechanism 220 (the feed rate in the direction of arrow S2 in Figure 3), the cutting width in the axial direction, and the data on the vibration frequency and amplitude caused by the second vibration mechanism 230 into the input means 311. In addition, as mentioned above, the input data can be set to be input directly or indirectly. <Cutting Characteristics> Referring to Figures 4 and 5, the cutting characteristics caused by the machine tool 10 will be explained. During the cutting action caused by the machine tool 10, the tool 210 experiences a force (cutting resistance) from the workpiece W. It is known that the cutting resistance is divided into three forces: the main force F1, the feed force F2, and the back force F3. In Figures 2 and 3 above, the directions of these forces are also indicated by arrows. The feed force F2 is a force parallel to the relative movement direction of the spindle 110 and the tool 210, and can be described as a force acting in the opposite direction to the relative movement direction (feed direction) of the tool 210 relative to the workpiece W. Figures 4 and 5 show the graphs of the relative movement of the tool tip 210 relative to the spindle 1, with the upper graph showing the relative movement of the cutting resistance (three forces) relative to the spindle 1. Figure 4 illustrates the cutting characteristics without vibration. That is, it illustrates the cutting characteristics when performing cutting without a vibration mechanism, or in other words, when using a conventional machine tool (NC lathe) without a vibration mechanism. Figure 5 illustrates the cutting characteristics with vibration. In the charts above each figure, the solid line N represents the Nth rotation of the spindle 110, the dotted chain line N-1 represents the (N-1)th rotation of the spindle 110, and the dashed line N-2 represents the (N-2)th rotation of the spindle 110. Furthermore, in these charts, WO represents the portion of the object W that will not be cut by the tool 210 during the Nth rotation of the spindle 110, and WO1 represents the portion of the object W that will be cut by the tool 210 during the Nth rotation of the spindle 110. Moreover, SA and SB represent the relative movement of the tool 210 relative to the object W caused by the moving mechanism. In the absence of vibration, SA corresponds to the movement (feed) of the tool 210 tip relative to the spindle 1. In contrast, in the presence of vibration, the movement of the tool 210 tip relative to the object W is the sum of the movement caused by the moving mechanism and the movement caused by the vibration. Therefore, SB can be described as the average amount of movement (feed) of the tip of tool 210 relative to the spindle 1. It can be seen that in the absence of cutting, the thickness of the part being cut (the part that becomes chips) (cutting thickness) is constant during the rotation of the spindle 110, and the three components of the cutting resistance are constant. In the case of cutting operations accompanied by vibration, depending on the vibration conditions (amplitude and frequency), as shown in Figure 5, during the rotation of the spindle 110, there can be a period of idle movement during which the tool 210 does not contact the workpiece W. In the graph shown in Figure 5, TA represents the period during which the workpiece W is cut by the tool 210, and TB represents the idle movement period. This allows for the precise cutting of chips. Furthermore, in the period TA, period TA1 represents the period during which the cutting thickness gradually increases, period TA23 represents the period during which the cutting thickness is theoretically constant, and period TA4 represents the period during which the cutting thickness gradually decreases. Then, in periods TA1 and TA23, period TA2 represents the period during which the tip of tool 210 moves in a deeper direction relative to the object being cut, W, due to the vibration of tool 210 (outbound journey). Furthermore, in period TA23, periods TA3 and TA4 represent the period during which the tip of tool 210 moves in a farther direction relative to the object being cut, W, due to the vibration of tool 210 (return journey). Then, it can be seen that the main component of the cutting resistance, F1, increases proportionally with the cutting thickness during period TA1, remains almost constant during period TA23, and decreases proportionally with the cutting thickness during period TA4. It can also be seen that the feed component, F2, increases proportionally with the cutting thickness up to period TA1, then remains almost constant up to periods TA23 and TA4, and decreases proportionally with the cutting thickness from period TA4 onwards. The back component, F3, remains almost constant throughout periods TA1, TA23, and TA4. <Difference between the outgoing and returning feed forces> As shown in Figure 5, the feed force F2 is almost constant during the outgoing period TA2 and the returning period TA3 within the time interval TA23. However, the inventors have observed that as the tip of the tool 210 wears down and its rounded end enlarges over time, the difference between the outgoing feed force F2 and the returning feed force F2 gradually increases. This point will be explained with reference to Figures 6 to 9. Figure 6 is a graph showing the relationship between cutting thickness and cutting resistance. Figure (a) shows the situation at the initial stage of tool 210 use (the case of a brand new tool 210), and Figure (b) shows the situation when the tip wear of tool 210 continues and the roundness of the tip increases. In each graph, the changes of the main component force F1, feed component force F2, and back component force F3 are shown with respect to cutting resistance. Furthermore, the arrows TA1 and TA4 in the graph correspond to the changes in TA1 and TA4 during the period shown in Figure 5, respectively, while TA23, TA2, and TA3 correspond to the changes in TA23, TA2, and TA3 during the period shown in Figure 5, respectively. From Figure 6, the following can be observed. First, compared to a brand-new tool 210, the cutting resistance components of a tool 210 with greater tip wear (roundness) are all larger. Second, it is also observed that with a brand-new tool 210, the cutting resistance components are almost identical in both the outgoing and returning directions. In this regard, it is observed that with a tool 210 having greater tip wear, the main component F1 and the back component F3 of the cutting resistance components are almost identical in both the outgoing and returning directions, but the feed component F2 will exhibit a difference d between the outgoing and returning directions. Referring to Figures 7 to 9, the results of the investigation into the reason why the difference between the feed force F2 on the outward path and the feed force F2 on the return path gradually increases as the tip of tool 210 wears down and its round end becomes larger over time. Before discussing the results, let's refer to Figure 7 and explain the trajectory angle θ. In the figure, arrow S represents the direction of movement of tool 210 relative to the object being cut, W, and arrow R represents the direction of rotation of the spindle 110 and the object being cut, W. The solid line WW represents the surface of the object being cut, W, and the dashed line NN represents the trajectory of the tip of tool 210. As shown, the trajectory angle θ is defined as the angle between the line connecting the trajectory of the tip of tool 210 parallel to the direction of movement S relative to the direction of rotation of the object being cut, and the plane perpendicular to the direction of movement S. The trajectory angle of tool 210 on its outward journey is considered positive, and the trajectory angle on its return journey is considered negative. Figures 8 and 9 show the path NN of the tool 210 tip and the surface WW of the object being cut by the tool 210. Figures 8 and 9 (a) and (b) show the condition of a brand new tool 210N, while (c) and (d) show the condition of a tool 210O after wear has occurred. Furthermore, (a) and (c) show the case where the path angle θ is positive (outbound path), and (b) and (d) show the case where the path angle θ is negative (return path). Figures 8 and 9 then show the case where the maximum path angle θ of the former is greater than that of the latter. After being cut by tool 210, the portion pressed by tool 210 immediately springs back, causing the surface WW of the workpiece W to slightly return to a direction opposite to the relative movement direction (feed direction) of tool 210 relative to workpiece W. The feed component F2 is equivalent to the rebound force on the tip of tool 210 from workpiece W in the opposite direction to the feed direction, and the wider the contact area between the tip of tool 210 and workpiece W, the greater the contact width. Figures 8 and 9, A11, A12, A13, A14, A21, A22, A23, and A24, show the contact width between the tip of tool 210 and workpiece W, which is almost proportional to the contact area. From Figures 8 and 9, the following can be observed geometrically: When the orbital angle θ is positive, the contact area is smaller than when the orbital angle θ is negative. This difference in contact area is larger in the case of a worn tool 210O compared to a brand new tool 210N; furthermore, the larger the maximum orbital angle θ, the greater the difference. From the above, it can be concluded that as the tip of tool 210 wears down over time and its rounded end becomes larger, the difference between the feed force F2 on the outward path and the feed force F2 on the return path will gradually increase. It can also be seen that the larger the maximum trajectory angle θ is, the larger the difference will be. Based on the insights gained above, by measuring (monitoring) the changes in the feed force during machining, the degree of wear (roundness) of the tool tip can be determined. Therefore, based on the data obtained from the measuring device 240, the control device C can function as a means of determining the degree of wear of the tool tip 210 by measuring the difference between the feed force F2 on the outward path and the feed force F2 on the return path. In other words, by simply measuring the feed force, the degree of wear of the tool tip can be determined during machining. Therefore, once a certain degree of wear has occurred, the operator can be prompted to change the tool 210 to suppress the decrease in machining accuracy. The specific method will be explained below. <Machine Tool Motion Control> The motion control of machine tool 10 will be described with reference to Figures 10 and 11. Figure 10 is an explanatory diagram of a threshold setting method related to an embodiment of the present invention. Figure 11 is a flowchart of machine tool motion control related to an embodiment of the present invention. The relationship between the difference between the feed force F2 on the outward path and the feed force F2 on the return path, and the degree of wear on the tip of tool 210, can be pre-established through analysis or experimental testing. Therefore, the control device C, which functions as a determination means, can determine the degree of wear on the tip of tool 210 according to the pre-established relationship. That is, by pre-storing the relationship in the memory of the control device C, the degree of wear on the tip of tool 210 can be determined by the control device C based on data obtained from the measuring device 240. Then, if the control means C determines that the degree of wear (difference) has exceeded a pre-set threshold, it will notify the outside world via the notification means 312 that the wear of tool 210 has exceeded a predetermined amount. This allows the operator to know that the wear of tool 210 has exceeded the pre-set threshold. The notification method can be by flashing a light source, emitting a sound through a speaker, or displaying a message on a display screen. Furthermore, if the control means C determines that the wear level has exceeded a preset threshold, it is preferable to stop the cutting action. In this way, the reduction in machining accuracy caused by continuing the cutting action through the worn tool 210 can be suppressed. Here, regarding the difference used by the control device C in making the determination, it is preferable to use the difference between the component of the cutting thickness of the workpiece W in the direction parallel to the moving direction (the moving direction caused by the moving mechanism) during the outward journey and the component of the cutting thickness during the return journey, within a predetermined range. As a preferred specific example, in Figure 5, during the theoretically constant cutting thickness period TA23, it is preferable to use the difference between the feed component F2 during the outward journey (within period TA2) and the feed component F2 during the return journey (within period TA3). For example, the difference between the feed component F2 at a certain point in period TA2 and the feed component F2 at a certain point in period TA3 can be used. Alternatively, the difference between the maximum value of the feed component F2 during period TA2 and the minimum value of the feed component F2 during period TA3 can also be used. Furthermore, the difference between the average value of the feed component F2 during period TA2 and the average value of the feed component F2 during period TA3 can also be used. By using the above differential method, the accuracy of determining the degree of wear can be improved. The threshold values ​​shown can be preset based on analytical or experimental testing and the generally required machining accuracy. However, the required machining accuracy will vary depending on the workpiece being processed. Therefore, in order to ensure that the replacement of tool 210 is only necessary to the minimum, it is best to set the threshold based on the required machining accuracy. Thus, it is preferable to first set a temporary threshold based on the generally required machining accuracy, and when the temporary threshold is exceeded, the operator should check the degree of wear on the tip of tool 210 and then reset the threshold. The following sections will explain the method for setting the temporary threshold, the method for resetting the threshold, and specific examples of motion control. Figure 10(a) is a graph showing the relationship between the number of processing operations (processing time) and the difference between the feed component F2 on the outward path and the feed component F2 on the return path. Furthermore, it goes without saying that the more processing operations (processing time) there are, the greater the wear (roundness) of the tool tip 210 will be. Figure 10(b) is a graph showing the relationship between the wear amplitude of the tool tip 210 from its initial state and the indicated difference. The results of this investigation show that even with a brand-new tool 210, a greater degree of roundness at the tip will result in the aforementioned difference. In Figure 10(a), the solid lines in graphs G1 and G2 represent cases where the tool 210 is brand-new and has not experienced wear, and the tip has a less rounded tip. In contrast, the dashed lines in graphs G3 and G4 represent cases where the tool 210 is brand-new and has not experienced wear, and the tip has a greater rounded tip. As mentioned above, the larger the maximum trajectory angle θ, the greater the difference. Graph G2 shows cases where the maximum trajectory angle θ is larger compared to graph G1, and graph G4 shows cases where the maximum trajectory angle θ is larger compared to graph G3. In the case of tool 210 corresponding to charts G1 and G2, when the number of processing steps (processing time) corresponding to the allowable value of wear based on the generally required machining accuracy is M01, the temporary threshold can be set to J01 in chart G1 and J02 in chart G2. Then, when the temporary threshold is exceeded, the operator can observe (measure) the wear degree of the tool tip 210, and determine how much the threshold can be increased based on the machining accuracy required for the processed product, and then reset the threshold. For example, by setting the number of processing steps to M11, the threshold can be reset to J11 in chart G1 and J12 in chart G2. Similarly, for tool 210 corresponding to charts G3 and G4, when the number of processing steps (processing time) corresponding to the allowable wear level based on the generally required machining accuracy is M02, the temporary threshold can be set to K01 in chart G3 and K02 in chart G4. Then, when the temporary threshold is exceeded, the operator can observe (measure) the wear level of the tool 210 tip, and determine how much the threshold can be increased based on the required machining accuracy of the processed product, and then reset the threshold. For example, by setting the number of processing steps to M12, the threshold can be reset to K11 in chart G3 and K12 in chart G4. Furthermore, the above diagrams G1, G2, G3, and G4 are merely examples. Preferably, the control device C stores the correspondence between the number of machining operations and the differential, so that it can correspond to the roundness of the tip of each usable tool 210 in its initial state of use, and can also correspond to a settable track angle θ. This allows for the setting of temporary thresholds corresponding to the tool 210 used and the set track angle θ. In addition to the roundness of the tool 210's tip in its initial state of use, temporary thresholds can also be set based on various data such as machining conditions, tool conditions (tool shape or material, etc.), and the material of the object being cut, W. As an example of machining conditions, the temporary threshold can be set considering the variation in the feed force differential due to the size of the depth of cut. Furthermore, as an example of tool conditions, the temporary threshold can be set considering the variation in the feed force differential when the take-off angle decreases. Here, when the temporary threshold is exceeded, it may be difficult to determine how much to increase the threshold based on the required machining accuracy of the workpiece by relying solely on the temporary threshold provided by the operator. Therefore, it is preferable to allow the operator to input the allowable wear amplitude to set the threshold. This point is illustrated in Figure 10(b), which shows the relationship between the wear amplitude and the difference in tool 210 from the initial stage of use. In Figure 10(b), J0 is the temporary threshold, and H0 is the wear amplitude when the temporary threshold is reached. Furthermore, it can be seen that the tip of tool 210 is prone to wear on the separation surface (the surface where tool 210 contacts the workpiece W during machining), and the wear amplitude represents the wear amplitude on the separation surface. When the difference reaches the temporary threshold J0, the machining operation can be temporarily stopped, allowing the operator to measure the wear amplitude and input the measurement result to predict the relationship between the wear amplitude and the difference. Figure G is a graphical representation of the predicted relationship. Then, the operator inputs the allowable wear amount, which sets the threshold. H1 is the allowable wear amount input by the operator, and J1 is the threshold that is reset. Next, referring to Figure 11, the operation flow of the machine tool 10 will be explained. When the operation of the machine tool 10 begins (step S11), the operator inputs the machining conditions into the input means 311 (step S11). The control device C determines whether it is a test machining based on the operator's input information (step S12). In the case of performing new machining (such as when the input information is new), it is determined to be a test machining. When it is determined to be a test machining, the machining operation begins, and based on the data obtained from the measuring device 240, the control device C measures (calculates) the difference between the feed component F2 on the outward path and the feed component F2 on the return path (step S13). Then, the control device C determines a temporary threshold based on the roundness of the tool 210 tip in the initial use state and the trajectory angle θ calculated from the input data (step S14). In addition, the determination of the temporary threshold, as described above, can be set based on other information. Then, the control device C determines sequentially during the machining operation whether the difference exceeds a temporary threshold (step S15). When the difference exceeds the temporary threshold, the control device C notifies the operator that the wear of tool 210 has exceeded the predetermined limit by notifying the operator (step S16). Furthermore, the control device C temporarily stops the machining operation (S17). This allows the operator to confirm the degree of wear on the tip of tool 210. For example, as described above, the operator measures the wear amplitude on the separation surface. Then, the operator determines the allowable wear amount based on the required machining accuracy of the workpiece and decides whether to change the threshold. The method for setting the threshold in cases of threshold changes has already been explained. The operator inputs whether to change the threshold and the threshold value for which the threshold needs to be changed in input means 311. If the threshold is not changed, the control device C sets a temporary threshold as the final threshold (step S19). If the threshold needs to be changed, the control device C sets a new threshold value as the new temporary threshold (step S20). Thus, the control device C has the function of a threshold setting means for resetting the threshold. When a new temporary threshold is set in step S20, the process returns to step S15 until it is determined in step S18 that the threshold has not been changed. The actions from step S15 to step S18 are repeated. When the threshold is set in step S19, the process ends (step SE). Then, when restarting the machining operation (step S11), the input of machining conditions can be omitted. Then, if it is determined in step S12 that the machining is not a test machining operation, formal machining will be performed based on the previously input machining conditions (step S21). When formal machining begins, the control device C will sequentially determine whether a machining end command signal has been issued (step S22). That is, when formal machining ends, for example, the operator issues a machining end command signal to the control device C by pressing the end button. In the control device C, the operation ends when a machining end command signal is determined to have been issued (step SE). In the control device C, unless a machining end command signal is received, the control device C will sequentially determine whether the difference exceeds the threshold set in step S19 (step S23). When the difference exceeds the threshold, the control device C will notify the operator that the wear of tool 210 has exceeded the predetermined amount by notifying the external system via notification means 312 (step S24). Furthermore, the control device C will stop the processing action (S25), thus ending the action (step SE). In this situation, after the operator exchanges for a brand new tool 210, the machining operation will restart (step SS). Then, in step S21, the machining conditions can be re-entered, or it can be set to directly continue from the previously entered data. The subsequent operation steps are as described above. (Modification) In the illustrated embodiment, the tip wear of tool 210 is determined by the difference between the feed force F2 on the outward journey and the feed force F2 on the return journey. However, the parameter used to determine wear is not necessarily the feed force F2 itself, but may be other parameters related to the feed force F2. That is, determining the degree of tip wear of tool 210 by the difference between the feed force F2 on the outward journey and the feed force F2 on the return journey includes determining the degree of wear by using the difference of parameters related to the feed force F2 on the outward and return journeys. Therefore, a method for determining the degree of tip wear of a tool based on the current value of a servo motor will be described with reference to FIG12 as a wear determination method related to a modification of the present invention. FIG12 is an explanatory diagram of the variation of the motor current value. When a servo motor is used as the drive source for the moving mechanism that moves the tool 210 and spindle 110 relative to each other, the current value of the servo motor is related to the feed force F2. As an example, under certain vibration conditions of a machine tool, when the moving mechanism is driven to move the tool 210 relative to the spindle 110 in a direction where the feed force F2 increases, the current value of the servo motor driving the moving mechanism decreases. Conversely, when the moving mechanism is driven to move the tool 210 relative to the spindle 110 in a direction where the feed force F2 decreases, the current value of the servo motor driving the moving mechanism increases. For example, when the feed direction of the tool 210 is the Z-axis direction, the feed force F2 acting in the Z-axis direction is negatively correlated with the current value I2 of the servo motor driving the first moving mechanism 130 that moves the tool 210 relative to the spindle 110 in the Z-axis direction. Then, as the tip of tool 210 wears down and its round end becomes larger over time, the difference between the current value I2 on the outward journey and the current value I2 on the return journey will gradually decrease. The following explanation describes a method for determining the degree of wear on the tip of tool 210 by using the current value I2 of the servo motor of the first moving mechanism 130, which has a negative correlation with the feed component F2, in the case where the feed direction of tool 210 is the Z-axis. Figure 12(a) is a graph showing the relationship between the cutting thickness and the current value I2 in the initial stage of use of tool 210 (the case of a brand new tool 210). Figure 12(b) is a graph showing the relationship between the cutting thickness and the current value I2 in the case where the tip wear of tool 210 continues and the roundness of the tip increases. Figure 12(c) is a graph showing the relationship between the wear amplitude from the initial state of the tip of tool 210 and the difference between the current value I2 on the outward journey and the current value I2 on the inward journey. Arrows TA1 and TA4 in the graphs correspond to the changes in TA1 and TA4 during the periods shown in Figure 5, respectively, while TA2 and TA3 correspond to the changes in TA2 and TA3 during the periods shown in Figure 5, respectively. As shown in Figures 12(a) and 12(b), during period TA1, when the cutting thickness gradually increases and the feed force F2 gradually increases, the current value I2 gradually decreases. On the other hand, during period TA4, when the cutting thickness gradually decreases and the feed force F2 gradually decreases, the current value I2 gradually increases. Then, the current value I2 during the outward movement of period TA2 differs from the current value I2 during the return movement of period TA3. As shown in Figure 12, the difference between the current value I2 when the tool 210 is traveling to and returning to its origin gradually decreases as the tip of the tool 210 wears down over time, causing its rounded end to enlarge. That is, in the case of a brand-new tool 210, if the difference between the current value I2 of the servo motor when traveling to and returning to its origin is dIa, and in the case of a tool 210 with greater tip wear, the difference is dIb, then it can be seen that dIa > dIb. As described above, as the tip of tool 210 wears down and its rounded end enlarges over time, the difference between the outgoing current value I2 and the returning current value I2 gradually decreases. Therefore, the degree of wear on the tip of tool 210 is negatively correlated with the difference dI between the outgoing and returning current values ​​I2 of the servo motor. By utilizing this correlation, the degree of wear on the tip of tool 210 can be determined based on the difference in current value I2, instead of the difference in feed force F2. When using the current value I2 to determine the wear level of the tool tip 210, for example, it is preferable to temporarily stop the machining operation and prompt the operator to change the tool 210 when the difference dI between the current value I2's outward and inward journeys reaches a threshold Q1. In the graph P shown in Figure 12(c), H1 represents the wear level when the difference dI between the current values ​​I2 reaches the threshold Q1. The graph P is a formulaic representation of the predicted relationship, which can be preset based on analysis or experimental testing. With this structure, the operator can timely grasp the wear level of the tool tip during machining, thereby suppressing the decrease in work efficiency. Furthermore, it is preferable to set a temporary threshold in the same way as in the embodiment described above. As described above, the wear level (roundness) of the tool tip can be determined by acquiring (monitoring) the current value of the motor, which is related to the feed force. Then, by setting up a detection method to detect the current value I2 of the servo motor, the control device C can function as a means of determining the wear level of the tool tip 210 by the difference between the current value I2 during the outward and return journeys. That is, as long as the servo motor current value is acquired, the wear level of the tool tip can be determined during machining. Therefore, when a certain degree of wear has occurred, prompting the operator to change the tool 210 can suppress the decrease in machining accuracy. Furthermore, it is not necessary to convert the servo motor current value into a force component to determine the wear level of the tool tip. Furthermore, in the modified example described above, although the degree of wear on the tool tip is determined based on the current value of the servo motor of the first moving mechanism 130, the current value used is not limited to the stated current value. For example, the degree of wear can also be determined based on the sum of the current values ​​of the servo motors of the first moving mechanism 130, which drive the spindle 110 in the Z-axis direction, and the servo motors of the first vibration mechanism 140. Also, when the feed direction of the tool 210 is the X-axis direction, the degree of wear can be determined based on the current value of the servo motor of the second moving mechanism 220 or the servo motor of the second vibration mechanism 230. Furthermore, in the aforementioned variation, although the wear level of the tool tip is determined by using the current value of the servo motor instead of the feed force, the parameters used are not limited to the current value of the servo motor. Parameters used to determine the wear level can be, for example, a converted value from the current value of the servo motor or a value obtained through an inference method using an interference observer. That is, by using a parameter related to the feed force, and also based on the numerical difference between the forward and return paths of the tool 210 at the feed force, the wear level of the tool tip can be determined during machining. 10: Machine tool; 110: Spindle; 120: Rotary mechanism; 130: First moving mechanism; 131: Moving table; 140: First vibration mechanism; 210, 210N, 210O: Tool; 220: Second moving mechanism; 221: Moving table; 230: Second vibration mechanism; 240: Measuring device; 311: Input means; 312: Notification means; C: Control device; F1: Main component force; F2: Feed component force; F3: Back component force; W: Cutting object. Figure 1 is a schematic structural diagram of a machine tool related to an embodiment of the present invention. Figure 2 is an operational diagram illustrating the operation in the first cutting mode of the machine tool related to an embodiment of the present invention. Figure 3 is an operational diagram illustrating the operation in the second cutting mode of the machine tool related to an embodiment of the present invention. Figure 4 is an explanatory diagram of cutting characteristics when performing cutting without vibration. Figure 5 is an explanatory diagram of cutting characteristics when performing cutting with vibration. Figure 6 is a graph comparing the variation of cutting impedance between a tool in the initial stage of use and a tool after wear has occurred. Figure 7 is an explanatory diagram of the track angle. Figure 8 is an explanatory diagram of the mechanism for generating a difference in the component forces. Figure 9 is an explanatory diagram of the mechanism for generating a difference in the component forces. Figure 10 is an explanatory diagram of a method for setting a threshold related to an embodiment of the present invention. Figure 11 is a flowchart of the operation control of the machine tool related to an embodiment of the present invention. Figure 12 is an explanatory diagram of the variation of the motor current value. 10: Machine Tools 110: Spindle 120: Rotating mechanism 130: Mobile mechanism 131: Mobile station 140: First Vibration Mechanism 210: Tools 220: Second moving mechanism 221: Mobile station 230: Second Vibration Mechanism 240: Measuring device 311: Input device 312: Notification Methods S1: Arrow S2: Arrow T1: Arrow T2: Arrow R: Arrow C: Control device W: Object to be cut

Claims

1. A machine tool comprising: a spindle on which a workpiece is mounted; a rotating mechanism for rotating the spindle; a tool for cutting the workpiece; a moving mechanism for moving the spindle and the tool relative to each other; and a vibrating mechanism for vibrating the spindle and the tool relative to each other in a direction parallel to the direction of movement caused by the moving mechanism; the machine tool cuts the workpiece by rotating the spindle via the rotating mechanism and vibrating and moving the workpiece and the tool relative to each other via the moving mechanism and the vibrating mechanism; the machine tool includes a determination means for determining the degree of wear of the tool tip by measuring the difference between the component of the force acting on the tool from the workpiece in the direction parallel to the direction of movement, in terms of the component force in the direction of return of the relative vibration of the workpiece and the tool.

2. The machine tool as described in claim 1, wherein, The determination method uses the difference between the component force on the outgoing path and the component force on the returning path when the cutting thickness in the direction parallel to the moving direction of the object being cut is within a predetermined range to determine the degree of wear on the tip of the tool.

3. The machine tool as described in claim 1, wherein, The relationship between the difference and the degree of wear is pre-defined, and the determination method will determine the degree of wear according to the pre-defined relationship.

4. The machine tool described in claim 1 is equipped with a notification means that, when the determination means has determined that the wear level has exceeded a preset threshold, it can notify the outside that the wear of the tool has exceeded a predetermined amount.

5. The machine tool as described in claim 1, wherein, If the determination method confirms that the wear level has exceeded the preset threshold, the cutting action will be stopped.

6. The machine tool described in claim 4 sets the threshold value based on the alignment of the track in the direction parallel to the direction of movement relative to the rotation direction of the workpiece being cut relative to the tool tip, and the track angle between the track and the surface perpendicular to the direction of movement.

7. The machine tool described in Request 4 sets the threshold based on the difference in the initial state of use of the tool.

8. The machine tool described in claim 1 has a threshold setting means that, when the determination means determines that the wear level has exceeded a preset threshold, it will temporarily stop the cutting operation and, after the temporary stop, reset the threshold.

9. The machine tool as described in claim 8, wherein, The threshold setting method uses the correlation between the wear rate of the tool from the beginning of its use and the difference to set the difference of the allowable wear rate input by the operator as the threshold.

10. The machine tool as described in claim 1, wherein, The moving mechanism comprises: a first moving mechanism for moving the spindle and the tool relative to each other in the axial direction of the spindle; and a second moving mechanism for moving the spindle and the tool relative to each other in a direction perpendicular to the axial direction; the vibration mechanism comprises: a first vibration mechanism for vibrating the spindle and the tool relative to each other in the axial direction of the spindle; and a second vibration mechanism for vibrating the spindle and the tool relative to each other in a direction perpendicular to the axial direction; the vibration mechanism further comprises: a first cutting mode in which, while rotating the spindle via the rotating mechanism, the object to be cut and the tool are vibrated relative to each other and moved in the axial direction of the spindle via the first moving mechanism and the first vibration mechanism; and a second cutting mode in which, while rotating the spindle via the rotating mechanism, the object to be cut and the tool are vibrated relative to each other and moved in a direction perpendicular to the axial direction via the second moving mechanism and the second vibration mechanism, so as to cut the object to be cut.

11. The machine tool according to any one of claims 1 to 10, comprising: a measuring means for measuring the force exerted on the tool from the workpiece in order to derive the difference.

12. The machine tool as described in claim 11, wherein, This measurement method measures the force exerted on the tool from the object being cut by measuring the current value of the motor driving the moving mechanism.

13. A machine tool comprising: a spindle on which a workpiece is mounted; a rotating mechanism for rotating the spindle; a tool for cutting the workpiece; a moving mechanism for moving the spindle and the tool relative to each other; a vibrating mechanism for vibrating the spindle and the tool relative to each other in a direction parallel to the moving direction of the moving mechanism; and a motor for driving the moving mechanism; the machine tool cuts the workpiece by rotating the spindle via the rotating mechanism and vibrating and moving the workpiece and the tool relative to each other via the moving mechanism and the vibrating mechanism; the machine tool includes a determination means for determining the degree of wear of the tool tip by measuring the difference between the current value generated by the motor during the relative movement of the spindle and the tool, based on the current value generated by the motor.

14. The machine tool as described in claim 13, wherein, The determination method uses the difference between the current value on the outgoing path and the current value on the returning path when the cutting thickness in the direction parallel to the moving direction of the object being cut is within a predetermined range to determine the degree of wear on the tip of the tool.

15. The machine tool as described in claim 13, wherein, The relationship between the difference and the degree of wear is pre-defined, and the determination method will determine the degree of wear according to the pre-defined relationship.

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