WORKPIECE MASS DETERMINATION DEVICE, MACHINE MACHINING ESTIMATION DEVICE AND MACHINE MACHINING SYSTEM

Abstract

A workpiece mass determination device (131) is a workpiece mass determination device configured to calculate an analytical workpiece mass (M'w(Z')) for analyzing dynamic characteristics during machining in a machining device (2) configured to machine a workpiece (W) using a tool (T).The workpiece mass determination device comprises: a first correspondence relationship storage unit (103b) configured to store a mass correspondence relationship, which is a correspondence relationship between the analytical workpiece mass (M'w(Z')) and a machining state index (Z') that changes depending on a machining state of the workpiece by the tool; a machining state index acquisition unit (125) configured to acquire the machining state index (Z'); and a workpiece mass determination unit (122) configured to determine the analytical workpiece mass (M'w(Z')) based on the acquired machining state index (Z') and the mass correspondence relationship.

Description

Technical area

[0001] The present disclosure relates to a workpiece mass determination apparatus, a machining estimation apparatus, and a machining system. Background of the invention

[0002] In a grinding device that grinds a workpiece with a grinding wheel, it is necessary to correct the relative positions of the workpiece and the grinding wheel in the estimation process in order to estimate the machining result with high accuracy. In a configuration disclosed in Patent Document 1, when a workpiece is ground with a grinding wheel, the machining result of the workpiece is estimated by correcting the relative positions of the workpiece and the grinding wheel with high accuracy, taking into account a static contact rigidity between the workpiece and the grinding wheel, along with a support rigidity of the workpiece and a support rigidity of the grinding wheel, in addition to a grinding resistance.The static contact stiffness used here is not calculated using a value measured when the grinding wheel is stationary, but rather by using a theoretical static contact stiffness during grinding. Static contact stiffness is represented by a spring constant K between the workpiece and the grinding wheel. An analytical workpiece mass is a fixed value calculated from dynamic non-machining characteristics. Related prior artPatent documents

[0003] Patent Document 1: Japanese Unexamined Patent Application No.: 2015-208812 (JP 2015 - 208 812 A) Brief summary of the inventionProblem to be solved by the invention

[0004] The present inventors have previously proposed, in the configuration disclosed in Patent Document 1, to estimate the machining result with higher accuracy using a dynamic contact stiffness represented by the spring constant K and a damping coefficient C, instead of the static contact stiffness represented by the spring constant K. The present inventors have found that when the machining result is estimated using the dynamic contact stiffness, dynamic workpiece characteristics at a machining point change compared to the non-machining period, that is, the analytical workpiece mass changes depending on the machining state. This leads to an idea of a workpiece mass determination device for determining the analytical workpiece mass with high accuracy.

[0005] The present disclosure provides a workpiece mass determination apparatus capable of determining an analytical workpiece mass with high accuracy. Means to solve the problem

[0006] One embodiment of the present disclosure relates to a workpiece mass determination device configured to calculate an analytical workpiece mass (M'w(Z')) for analyzing dynamic characteristics during machining in a machining device (2) configured to machine a workpiece (W) using a tool (T).The workpiece mass determination device comprises: a first correspondence relationship storage unit (103b) configured to store a mass correspondence relationship, which is a correspondence relationship between the analytical workpiece mass (M'w(Z')) and a machining state index (Z') that changes depending on a machining state of the workpiece by the tool; a machining state index acquisition unit (125) configured to acquire the machining state index (Z'); and a workpiece mass determination unit (122) configured to determine the analytical workpiece mass (M'w(Z')) based on the acquired machining state index (Z') and the mass correspondence relationship. Effects of the invention

[0007] According to the above-described configuration, the analytical workpiece mass is determined based on the stored mass correspondence relationship, which is the correspondence relationship between the machining state index and the analytical workpiece mass, and the acquired machining state index. Thus, the analytical workpiece mass can be determined with high accuracy based on the correspondence relationship with the machining state index.

[0008] For example, when the analytical workpiece mass determined with high accuracy is used to estimate the machining result of the workpiece in combination with dynamic contact stiffness data between the workpiece and the tool shown by contact between the workpiece and the tool during machining, the accuracy of estimating the machining result is expected to increase.

[0009] As described above, according to the above-mentioned configuration, it is possible to provide the workpiece mass determining apparatus capable of determining the analytical workpiece mass with high accuracy.

[0010] The reference numerals in parentheses in the claims indicate a correspondence with specific devices described in the embodiments mentioned below, and are not intended to limit the technical scope of the present invention. Short description of the drawing Fig. 1 is a diagram showing a machining system including a workpiece mass determining device and a machining estimating device according to a first embodiment. Fig. 2 shows a functional block diagram of the workpiece mass determining device and the machining estimating device according to the first embodiment. Fig. 3 is a schematic diagram showing the state of interference between a workpiece and a grinding wheel during grinding. Fig. 4 is a diagram showing the shape of the workpiece in a grinding simulation represented using a group of radial line segments, and showing a state where the workpiece represented by the radial line segments coincides with or is superimposed on an outer peripheral line of the grinding wheel during grinding. Fig. Figure 5 shows a schematic diagram showing dynamic contact stiffness, dynamic workpiece holder stiffness, and dynamic tool holder stiffness during grinding. Fig. 6 is a diagram showing a first example (a) and a second example (b) of a correspondence relationship between a machining state index and dynamic contact stiffness data according to the first embodiment. Fig. 7 is a diagram showing a third example (a) and a fourth example (b) of the correspondence relationship between the machining condition index and the dynamic contact stiffness data according to the first embodiment. Fig. 8 is a flowchart showing a process of acquiring the dynamic contact stiffness data for generating the dynamic contact stiffness correspondence relationship. Fig. 9 shows a plan view of a grinding machine when the dynamic contact stiffness is obtained to generate the dynamic contact stiffness correspondence relationship. Fig. 10 is a diagram showing the states of the grinding machine in parts of the process for obtaining the dynamic contact stiffness to generate the dynamic contact stiffness correspondence relationship. Fig. 11 is a diagram showing an example of a correspondence relationship between the machining state index and an analytical workpiece mass in the first embodiment. Fig. 12 is a flowchart showing a process of acquiring the analytical workpiece mass for generating the mass correspondence relationship. Fig. 13 is a diagram showing a machining system including a workpiece mass determining device and a machining estimating device in a modification. Fig. 14 is a schematic diagram showing the state of interference between a workpiece, a grinding wheel, and a support device during grinding according to the modification. Embodiments of the Invention (First Embodiment) 1. Configuration of the Machining System 1

[0011] A workpiece mass determination unit 131, a machining estimation device 3b and a machining system 1 in a first embodiment will be described with reference to Fig. 1. The machining system 1 is intended to be a machining device that performs grinding. The machining system 1 includes a grinding machine 2, which serves as the machining device, and a processing unit 3.

[0012] The grinding machine 2 grinds the outer peripheral surface or the inner peripheral surface of a workpiece W by rotating the workpiece W, rotating a grinding wheel T serving as a tool that is a rotating body, and bringing the grinding wheel T relatively closer to the workpiece W in a direction intersecting the axis of the workpiece W. The grinding machine 2 may be a table-feed type grinder, a grindstone-head feed type grinder, etc. Alternatively, the grinding machine 2 may be a cylindrical grinder, a cam grinder, etc.

[0013] As it is in Fig. 1, the present embodiment illustrates an example in which the workpiece W includes a shank portion Wa, which is not a machining target portion, and a plurality of machining target portions Wb, whose outer peripheral surfaces are to be ground. The machining target portion Wb has, for example, a cylindrical outer peripheral surface coaxial with the shank portion Wa. The workpiece W shown in Fig. 1 is merely an example, whereby the grinding machine 2 can grind workpieces with different shapes.

[0014] The processing unit 3 includes a control device 3a that controls the grinding machine 2, and the machining estimation device 3b that estimates a machining result. The control device 3a can control grinding by controlling the grinding machine 2. The machining estimation device 3b performs a process of estimating a machining result of the workpiece W by receiving input of information to be used for grinding and executing a simulation.

[0015] The machining estimation device 3b may function as a simulation device independent of the grinding machine 2, or it may function as a simulation device operating in conjunction with the grinding machine 2. In the former case, for example, an optimal grinding condition can be determined without actually grinding the workpiece W. In the latter case, the machining estimation device 3b may operate, for example, to correct the grinding condition or influence various types of control by executing processing concurrently with grinding of the workpiece W by the grinding machine 2. The machining estimation device 3b may be a built-in system of the grinding machine 2 and the control device 3a. 2. Configurations of the grinding machine 2 and the control device 3a

[0016] An example of the configurations of the grinding machine 2 and the control device 3a will be described in detail with reference to Fig. 1. The grinding machine 2 is, for example, a table-feed type cylindrical grinding machine. That is, the grinding machine 2 is configured to move the workpiece W in the axial direction of the workpiece W and to move the grinding wheel T in a direction intersecting the axis of the workpiece W. The present embodiment illustrates an example in which the grinding machine 2 grinds a cylindrical outer peripheral surface of the workpiece W using the grinding wheel T.

[0017] The grinding machine 2 includes a base 10, a table 20, a spindle device 30, a tailstock device 40, a grindstone head 50, a size determining device 60, and the control device 3a. The base 10 is formed to have a longer width (length in the Z-axis direction) on the front surface side (lower side in Fig. 1) in the X-axis direction and a shorter width on the rear surface side (upper side in Fig. 1) in the X-axis direction.

[0018] The base 10 includes a Z-axis guide surface 11 extending in the Z-axis direction on the upper surface of the front surface side in the X-axis direction. The base 10 further includes a Z-axis drive mechanism 12 driven along the Z-axis guide surface 11. The present embodiment illustrates an example in which the Z-axis drive mechanism 12 includes a ball screw mechanism 12a and a Z-axis motor 12b. The ball screw mechanism 12a extends parallel to the Z-axis guide surface 11, and the Z-axis motor 12b drives the ball screw mechanism 12a.

[0019] A Z-axis drive circuit (not shown) and a Z-axis detector 12c are provided to drive the Z-axis drive mechanism 12a. The Z-axis drive circuit includes an amplifier circuit and drives the Z-axis motor 12b. In the present embodiment, the Z-axis detector 12c is an angle detector such as an encoder and detects the angle of a rotating shaft of the Z-axis motor 12b. The Z-axis drive mechanism 12a may include a linear motor, etc., instead of the above-described ball screw mechanism 12a.

[0020] The base 10 also includes a guide surface 13 extending in a direction intersecting the Z-axis direction on the upper surface at the rear surface side in the X-axis direction. In the present embodiment, the guide surface 13 is an X-axis guide surface extending in the X-axis direction orthogonal to the Z-axis. The base 10 further includes an X-axis drive mechanism 14 driven along the X-axis guide surface 13. The present embodiment illustrates an example in which the X-axis drive mechanism 14 includes a ball screw mechanism 14a and an X-axis motor 14b. The ball screw mechanism 14a extends parallel to the X-axis guide surface 13, with the X-axis motor 14b driving the ball screw mechanism 14a.

[0021] An X-axis drive circuit (not shown) and an X-axis detector 14c are provided to drive the X-axis drive mechanism 14. The X-axis drive circuit includes an amplifier circuit and drives the X-axis motor 14b. In the present embodiment, the X-axis detector 14c is an angle detector such as an encoder and detects the angle of a rotating shaft of the X-axis motor 14b. The X-axis drive mechanism 14 may include a linear motor, etc., instead of the ball screw mechanism 14a described above.

[0022] The table 20 has an elongated shape and is supported on the Z-axis guide surface 11 of the base 10 to be movable in the Z-axis direction (horizontal right-left direction). The table 20 is fixed to a ball screw nut of the Z-axis ball screw mechanism 12a and is moved in the Z-axis direction by a rotary drive of the Z-axis motor 12b.

[0023] The spindle device 30 constitutes a workpiece holding device. The spindle device 30 holds the workpiece W and rotates the workpiece W. The spindle device 30 is arranged on the table 20 at one end in the Z-axis direction. The spindle device 30 includes a spindle housing 31, a spindle 32, a spindle motor 33, a spindle center 34, a spindle detection device 35, and a spindle drive circuit (not shown).

[0024] The spindle housing 31 is fixed to the table 20. The spindle 32 is rotatably supported in the spindle housing 31 via a bearing. The spindle motor 33 rotates the spindle 32. The spindle center 34 holds the end face of the workpiece W at one axial end. The spindle center 34 is fixed to the spindle 32 and is provided so that it is rotatable with respect to the spindle housing 31. When the spindle device 31 includes a rotating member such as a carrier (not shown), the spindle center 34 may be fixed to the spindle housing 31 and provided so that it is not rotatable with respect to the spindle housing 31. Alternatively, the spindle device 30 may include a chuck that grips the workpiece W instead of the spindle center 34. The chuck is rotationally driven by being coupled to the spindle 32.

[0025] The spindle detection device 35 and the spindle drive circuit are provided to drive the spindle motor 33. In the present embodiment, the spindle detection device 35 is an angle detection device, such as an encoder or a pulse generator, and detects the angle of a rotating shaft of the spindle motor 33. The spindle drive circuit includes an amplifier circuit and drives the spindle motor 33.

[0026] The tailstock device 40 constitutes the workpiece support device together with the spindle device 30. The tailstock device 40 is arranged on the table 20 at the other end side in the Z-axis direction. The tailstock device 40 is provided on the table 20 so as to be movable in the Z-axis direction. The tailstock device 40 includes a tailstock center point 41. The tailstock center point 41 holds the end surface of the workpiece W at the other axial end. The tailstock center point 41 may be provided so as to be non-rotatable or it may be provided so as to be rotatable. The tailstock device 40 is not necessary when the grinding machine 2 grinds the inner peripheral surface of the workpiece W.

[0027] The tailstock center 41 may be positioned at a fixed position with respect to the workpiece W, or it may be provided so as to be operable with the workpiece W in the axial direction of the workpiece W. In the latter case, the tailstock center 41 may be configured to adjust a pressing force applied to the workpiece W in the axial direction of the workpiece W. The pressing force may be controllable by means for adjusting a spring force, means for adjusting a hydraulic pressure, etc.

[0028] The grindstone head 50 includes the grinding wheel T serving as the tool, and rotationally drives the grinding wheel T. The grindstone head 50 includes a grindstone head body 51, a grindstone shaft 52, a grinding wheel motor 53, and a grinding wheel drive circuit (not shown) in addition to the grinding wheel T.

[0029] The grinding wheel T has a disc shape. The grinding wheel T is used to grind the outer peripheral surface or the inner peripheral surface of the workpiece W. The grinding wheel T is formed by fixing a plurality of abrasive grains using a binder. The abrasive grains can be general abrasive grains made of ceramic materials such as alumina or silicon carbide, superabrasives such as diamond and CBN, etc.

[0030] The binder can be sintered (V), a resinoid (B), rubber (R), silicate (S), shellac (E), metal (M), an electrodeposition (B), magnesia cement (Mg), etc. The grinding wheel T can have pores or it can have no pores. The grinding wheel T can be either elastically deformable or difficult to elastically deform, depending on the type of binder and the presence or absence of pores. The elastic modulus of the elastically deformable grinding wheel T can vary depending on the type of binder, the presence or absence of pores, the porosity, etc.

[0031] The grinding stone head body 51 has, for example, a rectangular shape in a plan view and is supported on the X-axis guide surface 13 of the base 10 so as to be movable in the X-axis direction (horizontal front-back direction). The grinding stone head body 51 is fixed to a screw nut of the X-axis ball screw mechanism 14a and is moved in the X-axis direction by a rotation drive of the X-axis motor 14b. The grinding stone head body 51 constitutes a tool holder device that holds the grinding wheel T.

[0032] The grindstone shaft 52 is rotatably supported on the grindstone head body 51 via a bearing. The grinding wheel T is fixed to the distal end of the grindstone shaft 52 and is rotated by rotation of the grindstone shaft 52. The grinding wheel motor 53 drives the grindstone shaft 52 to rotate. The bearing can be a hydrostatic bearing, a roller bearing, etc.

[0033] The grinding wheel motor 53 transmits a rotational drive force to the grindstone shaft 52, for example, via a belt. The grinding wheel motor 53 can be arranged coaxially with the grindstone shaft 52. Generally, the rotational speed of the grinding wheel T driven by the grinding wheel motor 53 is higher than the rotational speed of the workpiece W driven by the spindle motor 33. The grinding wheel drive circuit is provided to drive the grinding wheel motor 53. The grinding wheel drive circuit includes an amplifier circuit and drives the grinding wheel motor 53.

[0034] The size determination device 60 is provided on the upper surface of the base 10, and measures the outer diameter of the workpiece W. The size determination device 60 includes, for example, a pair of contact devices that can come into contact with the outer peripheral surface of the workpiece W, and measures the outer diameter of the workpiece W at the contact portion.

[0035] The control device 3a is a CNC (Computer Numerical Control) device and a PLC (Programmable Logic Controller) device that perform machining control. That is, the control device 3a controls the positions of the table 20 and the grindstone head 50 by driving the Z-axis drive mechanism 12 and the X-axis drive mechanism 14, which serve as moving devices, based on a grinding program and a measurement result from the size determination device 60. That is, the control device 3a moves the workpiece W and the grinding wheel T closer to or away from each other by controlling the positions of the table 20, the grindstone head 50, etc. Furthermore, the control device 3a controls the spindle device 30 and the grindstone head 50. That is, the control device 3a controls rotation of the spindle 32 and rotation of the grinding wheel T. 3. Configuration of the machining estimation device 3b

[0036] The configuration of the machining estimation device 3b will be described with reference to Fig. 2. The machining estimation device 3b includes a command value acquisition unit 101, an estimation unit 102, a dynamic contact stiffness table storage unit (second correspondence relationship storage unit) 103a, a workpiece mass table storage unit (first correspondence relationship storage unit) 103b, a dynamic workpiece support stiffness table storage unit 103c, a dynamic tool support stiffness table storage unit 103d, a machining condition acquisition unit 106, a dynamic characteristic determination unit 107, a correction amount calculation unit 108, an output unit 109, and a machining condition optimization unit 110.

[0037] The command value acquisition unit 101 acquires a command value for controlling the grinding machine 2 during grinding. When the machining estimation device 3b is a simulation device independent of the grinding machine 2, the command value acquisition unit 101 generates a command value for controlling various sections of the grinding machine 2 through calculation by receiving an input of a grinding program and configuration information about the grinding machine 2. When the machining estimation device 3b functions as a simulation device operating in conjunction with grinding by the grinding machine 2, the command value acquisition unit 101 may acquire a command value directly from the control device 3a for the grinding machine 2.

[0038] The estimation unit 102 estimates at least one of the state of the workpiece W or the grinding wheel T during grinding, the shape of the workpiece W, the shape of the grinding wheel T, and the mechanical state of the grinding machine 2 by performing a grinding simulation using the command value acquired by the command value acquisition unit 101.

[0039] Examples of the state of the workpiece W include the vibration state and the temperature state of the workpiece W. Examples of the state of the grinding wheel T include the vibration state and the temperature state of the grinding wheel T, the grinding resistance caused to each portion of the outer peripheral surface of the grinding wheel T, the sharpness of the grinding wheel T, and the state of the abrasive grains constituting the grinding wheel T. Examples of the state of the abrasive grains include the average protrusion amount of the abrasive grains and the distribution of the abrasive grains. The shape of the workpiece W includes the shape of the workpiece W in the middle stage of grinding and the shape of the workpiece W in the final stage of grinding. The shape of the grinding wheel T includes the shape of the grinding wheel T in the middle stage of grinding and the shape of the grinding wheel T in the final stage of grinding.The mechanical state of the grinding machine 2 includes the vibration state and the temperature state of sections constituting the grinding machine 2.

[0040] The present embodiment illustrates an example in which the estimation unit 102 estimates the shape of the workpiece W, the state of the workpiece W, and the mechanical state of the grinding machine 2 by executing a process of sequentially varying the shape of the workpiece W through a grinding simulation. In the present embodiment, a grinding simulation is performed under the assumption that the grinding wheel T is not deformed. The estimation unit 102 can also estimate the grinding resistance caused for each portion of the outer peripheral surface of the grinding wheel T, in addition to the above-mentioned estimation targets.

[0041] The estimation unit 102 includes an overlay amount calculation unit 111, a grinding efficiency calculation unit 112, a grinding characteristic determination unit 113, and a grinding resistance calculation unit 114.

[0042] The interference amount calculation unit 111 calculates the amount of interference between the workpiece W and the grinding wheel T based on the relative positions of the workpiece W and the grinding wheel T, the outer peripheral surface shape of the workpiece W, and the outer peripheral surface shape of the grinding wheel T, which are obtained using the command value acquired by the command value acquisition unit 101. The interference amount corresponds to the amount of grinding in the radial direction of the workpiece W at each position in the circumferential direction of the workpiece W. In other words, the interference amount is the amount of the workpiece W removed by grinding by the grinding wheel T, specifically, the amount of the workpiece W to be removed in the radial direction at each portion in the circumferential direction of the workpiece W. As shown in Fig. 3, the amount of interference is the volume of a section where the workpiece W and the grinding wheel T meet or overlap (hatched section in Fig. 3; overlay region).

[0043] The overlay amount calculation unit 111 geometrically calculates the overlay amount through a calculation. The overlay amount calculation unit 111 stores the outer peripheral surface shape of the workpiece W and the outer peripheral surface shape of the grinding wheel T. As shown in the right section of Fig. 4, the outer peripheral surface shape of the workpiece W is expressed by a group of a plurality of radial line segments on polar coordinates with a rotation center Ow of the workpiece W as the origin. That is, the superposition amount calculation unit 111 stores, as the outer peripheral surface shape of the workpiece W, a group of a plurality of line segments including the rotation center Ow (the origin) of the workpiece W and division points (white dots in Fig. 4) on the outer peripheral surface of the workpiece W, which are obtained by dividing the outer peripheral surface by equal angles (a). The division points, which are indicated by the white dots in Fig. 4 are stored as the outer peripheral surface shape of the workpiece W before removal by the grinding wheel T.

[0044] The overlay amount calculation unit 111 determines crossing points (black dots in Fig. 4) between the line segments for the workpiece W and a line representing the outer peripheral surface shape of the grinding wheel T, from the relative positions (interaxial distance) of the workpiece W and the grinding wheel T and the outer peripheral surface shape of the grinding wheel T. The superposition amount calculation unit 111 stores the determined crossing points (black dots in Fig. 4) as the outer peripheral surface shape of the workpiece W after removal by the grinding wheel T. That is, the superposition amount calculation unit 111 changes the stored outer peripheral surface shape of the workpiece W.

[0045] The overlay amount calculation unit 111 subtracts the area of a triangle ΔOw-b1-b2 formed by the origin Ow and points b1, b2 after removal (intersection points with the grinding wheel T) from the area of a triangle ΔOw-a1-a2 formed by the origin Ow and points a1, a2, which are adjacent points among the points defining the outer peripheral surface shape of the workpiece W before removal. The area after the subtraction is calculated for all pairs of adjacent points defining the outer peripheral surface shape of the workpiece W.

[0046] The overlap amount calculation unit 111 calculates the overlap amount (removal amount) by integrating the areas after subtraction and multiplying the total integrated area by the thickness of the workpiece W. In the above description, the area of the removed portion is calculated by calculating the areas of two types of triangles and calculating the difference between such areas. Alternatively, the area of the removed portion may be calculated by directly calculating the area of a rectangle a1-a2-b1-b2.

[0047] As it is in Fig. As shown in Fig. 2, the grinding efficiency calculation unit 112 calculates a grinding efficiency (machining efficiency) Z' based on the overlay amount calculated by the overlay amount calculation unit 111. The grinding efficiency Z' is the overlay amount per unit time, that is, it is obtained by calculating the volume of the workpiece W to be ground by the grinding wheel T in a unit time.

[0048] The grinding characteristic determination unit 113 determines a grinding characteristic kc based on the material of the workpiece W, the types of abrasive grains and binder of the grinding wheel T, the condition of the outer peripheral surface of the grinding wheel T, etc. The condition of the outer peripheral surface of the grinding wheel T is expressed using, for example, an index representing the wear state of the abrasive grains of the grinding wheel T or the sharpness of the grinding wheel T. The grinding characteristic determination unit 113 stores the grinding characteristic in each state obtained in advance through experiments, analysis, etc.

[0049] The grinding resistance calculation unit 114 calculates a grinding resistance Fn in a direction (X-axis direction) normal to the outer peripheral surface of the workpiece W based on the grinding efficiency Z' and the grinding characteristic kc. The grinding resistance Fn is obtained by multiplying the grinding efficiency Z' by the grinding characteristic kc (Fn = kc × Z').

[0050] The grinding characteristic kc has a substantially linear relationship in which the grinding resistance Fn in the normal direction (X-axis direction) increases as the grinding efficiency Z' increases. This relationship of the grinding characteristic kc changes, for example, when the grinding wheel T is worn. For example, the relationship changes such that the grinding resistance Fn in the normal direction increases with respect to the grinding efficiency Z' as the grinding wheel T is worn.

[0051] The dynamic contact stiffness table storage unit 103a stores dynamic contact stiffness data Ci(Z'), Ki(Z') between the workpiece W and the grinding wheel T. Specifically, the dynamic contact stiffness correspondence relationship storage unit 103a constitutes the second correspondence relationship storage unit that stores a correspondence relationship between the machining state index and the dynamic contact stiffness data (Ci(Z'), Ki(Z')) described below. The dynamic workpiece support stiffness table storage unit 103c stores dynamic workpiece support stiffness data (Cw, Kw) for the spindle device 30 and the tailstock device 40 serving as the workpiece support device.Specifically, the dynamic workpiece fixture stiffness table storage unit 103c stores a correspondence relationship between the machining condition and the dynamic workpiece fixture stiffness data (Cw, Kw). The dynamic tool fixture stiffness table storage unit 103d stores dynamic workpiece fixture stiffness data (Ct, Kt) for the grindstone head body 51 serving as a grinding wheel support device. Specifically, the dynamic tool fixture stiffness table storage unit 103d stores a correspondence relationship between the machining condition and the dynamic tool fixture stiffness data (Ct, Kt). 4. Procurement of machining conditions

[0052] As it is in Fig. As shown in FIG. 2, the machining condition acquisition unit 106 acquires a machining condition for grinding to be performed by the grinding machine 2. Specifically, the machining condition acquisition unit 106 acquires a machining condition during estimation performed by the estimation unit 102 (during processing). The machining condition acquired by the machining condition acquisition unit 106 is information to be used by the dynamic characteristic determination unit 107 to calculate dynamic rigidity. Examples of the acquired machining condition include the type of workpiece W, the type of workpiece support member, the type of grinding wheel T, and the pressing forces applied by the spindle center 34 and the tailstock center 41.

[0053] When the machining estimation device 3b is a simulation device independent of the grinding machine 2, the machining condition acquisition unit 106 acquires a condition for determining dynamic stiffness by receiving an input of the mechanical configuration of the grinding machine 2 and a grinding program. When the machining estimation device 3b functions as a simulation device operating in conjunction with grinding by the grinding machine 2, the machining condition acquisition unit 106 may acquire the condition for determining dynamic stiffness by receiving an input of the mechanical configuration of the grinding machine 2 and the grinding program from the control device 3a, or it may acquire information about the condition directly from the control device 3a for the grinding machine 2. 5. Configuration of the Dynamic Characteristic Determination Unit 107

[0054] The dynamic characteristic determination unit 107 determines dynamic stiffness data and an analytical workpiece mass (M'w(Z')) that affect grinding. The dynamic characteristic determination unit 107 separately determines the dynamic contact stiffness data (Ci(Z'), Ki(Z')), the dynamic workpiece fixture stiffness data (Cw, Kw), the dynamic tool fixture stiffness data (Ct, Kt), and the analytical workpiece mass (M'w(Z')) that are in Fig. 5. That is, the dynamic characteristic determination unit 107 includes a dynamic contact stiffness determination unit 121, a workpiece mass determination unit 122, a dynamic workpiece fixture stiffness determination unit 123, and a dynamic tool fixture stiffness determination unit 124.

[0055] The dynamic contact stiffness (Ci(Z'), Ki(Z')), the dynamic workpiece holder stiffness (Cw, Kw), the dynamic tool holder stiffness (Ct, Kt) and the workpiece mass (Mw) are calculated with reference to Fig. 5. The dynamic contact stiffness (Ci(Z'), Ki(Z')) is a dynamic stiffness between the workpiece W and the grinding wheel T. The dynamic workpiece support stiffness (Cw, Kw) is a dynamic stiffness on the workpiece W side with respect to the table 20, the spindle device 30, and the fixture 40 including the workpiece W. The dynamic tool support stiffness (Ct, Kt) is a dynamic stiffness with respect to the grindstone head 50 including the grinding wheel T. The workpiece mass (Mw) is a mass of the workpiece W. Each of these will be described in detail below. 5-1. Dynamic contact stiffness, machining condition index

[0056] Dynamic contact stiffness is a dynamic stiffness between the workpiece W and the grinding wheel T and is exhibited by a contact between the workpiece W and the grinding wheel T during grinding. Dynamic contact stiffness is defined by a damping coefficient Ci and a spring constant Ki. Static contact stiffness, which is distinguished from dynamic contact stiffness, is represented only by the spring constant K and does not include the damping coefficient C. The damping coefficient Ci in dynamic contact stiffness is a value representing the relationship between the relative velocities of the workpiece W and the grinding wheel T and an external force received by the workpiece W or the grinding wheel T.The spring constant Ki is a value representing the relationship between the relative positions of the workpiece W and the grinding wheel T and an external force received by the workpiece W or the grinding wheel T.

[0057] The dynamic contact stiffness corresponds to a machining state index that changes depending on the machining state of the workpiece W by the tool (the grinding wheel T) during grinding in the machining device 2. Examples of the machining state index include the machining efficiency (grinding efficiency Z'), a contact arc length L, and g / a (grain cutting depth / grain cutting edge interval). A dynamic contact stiffness correspondence relationship, which is the correspondence relationship between the machining state index and the dynamic contact stiffness data (Ci(Z'), Ki(Z')), can be obtained by performing an actual measurement. As shown in Fig. 3, the contact arc length L is the length of an arc of the outer peripheral surface of the grinding wheel T in contact with the workpiece W during grinding in a cross-sectional direction in the direction orthogonal to the axis of the grinding wheel T. The contact arc length L changes depending on the feed speed of the grinding wheel T in the X-axis direction, the outer diameter of the grinding wheel T, the outer diameter of the workpiece W, etc.

[0058] Examples of the dynamic contact stiffness correspondence relationship between the machining condition index and the dynamic contact stiffness data (Ci(Z'), Ki(Z')) are shown in parts (a) and (b) according to Fig. 6 and parts (a) and (b) according to Fig. 7. In the examples shown in parts (a) and (b) according to Fig. 6, the grinding efficiency Z' is applied as the machining state index, and both the damping coefficient Ci and the spring constant Ki in the dynamic contact stiffness have nonlinear relationships instead of linear relationships (proportional relationships) with respect to the grinding efficiency Z'. Specifically, the dynamic contact stiffness correspondence relationship between the machining state index and the dynamic contact stiffness data (Ci(Z'), Ki(Z')) is a relationship in which the degree of change in the dynamic contact stiffness data (Ci(Z'), Ki(Z')) varies with respect to the machining state index.For example, in a quadratic plane with the machining condition index on the horizontal axis and the dynamic contact stiffness data (Ci or Ki) on the vertical axis, a function representing a curve with a continuously changing slope can be defined as an approximate expression. The approximate expression can be a higher-order function. For example, the curves shown in parts (a) and (b) according to . Fig. 6 are defined by cubic functions.

[0059] In the examples given in parts (a) and (b) according to Fig. 7, the contact arc length L is applied as the machining state index. In this case, the tendency is roughly the same as that in the case where the machining state index is the grinding efficiency Z', but this case does not easily fit the curve represented by the cubic function as in the case where the machining state index is the grinding efficiency Z'. The case where the machining state index is the grinding efficiency, as shown in parts (a) and (b) according to Fig. 6 simply fits the curve represented by the cubic function, and the approximate expression is easily generated. Consequently, the grinding efficiency Z' is preferably used as the machining condition index. Even in the case where the machining condition index is g / a, the correspondence relationship between the machining condition index and the dynamic contact stiffness data (Ci(Z'), Ki(Z')) shows roughly the same tendency as that in the case of the grinding efficiency Z' shown in parts (a) and (b) according to Fig. 6. The dynamic contact stiffness correspondence relationship may be represented by connecting a plurality of straight lines on the quadratic plane instead of the curve. The dynamic contact stiffness correspondence relationship may be in the form of a data table including a plurality of data correspondence relationships, rather than being defined as a function such as an approximate expression.

[0060] The machining state index is acquired by a machining state index acquisition unit 125 provided in the dynamic contact stiffness determination unit 121, and the dynamic contact stiffness correspondence relationship, which is the correspondence relationship between the machining state index and the dynamic contact stiffness data (Ci(Z'), Ki(Z')), is stored in the second correspondence relationship storage unit 103a. The dynamic contact stiffness data (Ci(Z'), Ki(Z')) is determined by the dynamic contact stiffness determination unit 121 based on the machining state index acquired by the machining state index acquisition unit 125.That is, the machining state index acquisition unit 125, the second correspondence relationship storage unit 103a, and the dynamic contact stiffness determination unit 121 constitute a dynamic contact stiffness determination device 130. 5-2. Dynamic contact stiffness acquisition process for generating the dynamic contact stiffness correspondence relationship

[0061] A process for obtaining the dynamic contact stiffness to generate the above-mentioned dynamic contact stiffness correspondence relationship will be described with reference to the Fig. 8 to 10. In the dynamic contact stiffness acquisition process, as described in Fig. 8, first, a measuring jig 4 is attached to the grinding machine 2 and the workpiece W (S1). The measuring jig 4 is a non-contact vibration device that applies a vibration force to the workpiece W. As shown in Fig. As shown in Fig. 9, the measuring jig 4 is provided on the upper surface of the table 20. The position at which the measuring jig 4 is fixed in the Z-axis direction on the upper surface of the table 20 is adjustable.

[0062] The measuring jig 4 holds the workpiece W, with the workpiece W being inserted therethrough. Specifically, a part of the shank portion Wa of the workpiece W, which is not the machining target portion, is inserted through the measuring jig 4, with the plurality of machining target portions Wb to be ground positioned outside the measuring jig 4. The workpiece W, inserted into and held by the measuring jig 4, is held by the spindle device 3 and the tailstock device 4 in the same manner as during normal grinding.

[0063] The configuration of the measuring clamp 4 is described with reference to Fig. 10(a) to Fig. 10(c). The measuring jig 4 includes a housing 131, an electromagnet 132, a rotor 133, a lock nut 134, a displacement sensor 135, and a control device 136. The housing 131 is fixed to the upper surface of the table 20 of the grinding machine 2. The housing 131 has a hole 131a extending through the housing 131 in the Z-axis direction.

[0064] The electromagnet 132 is embedded in the housing 131. The rotor 133 is attached to the outer peripheral surface of the workpiece W and provided integrally with the workpiece W. The rotor 133 is made of a magnetic substance and is moved by a magnetic force generated by the electromagnet 132. The rotor 133 has a cylindrical shape, and the outer peripheral surface of the rotor 133 is arranged with a predetermined clearance from the inner peripheral surface of the housing 131. This clearance defines the distance by which the rotor 133 is movable with respect to the housing 131. The inner peripheral surface of the rotor 133 is formed in accordance with the outer peripheral surface shape of the workpiece W. The lock nut 134 is a member for fixing the rotor 133 to the workpiece W.The method for fixing the rotor 133 is not limited to one using the lock nut 134, and various methods may be used.

[0065] The displacement sensor 135 is provided at a position near the inner peripheral surface of the housing 131, and measures the distance from the outer peripheral surface of the rotor 133. That is, the displacement sensor 135 measures a displacement (hereinafter referred to as "radial displacement") of the rotor 133 in the direction in which the rotor 133 is moved closer to the inner peripheral surface of the housing 131 and away from the inner peripheral surface of the housing 131 when the rotor 133 is vibrated by the electromagnet 132.

[0066] As it is in Fig. As shown in Figure 10(c), the control device 136 supplies a drive current to the electromagnet 132 so that the electromagnet 132 exerts a vibrating force. The control device 136 acquires a displacement measured by the displacement sensor 135, i.e., a radial displacement of the rotor 133.

[0067] In S1 in Fig. 8, as in Fig. 10(a), the shaft portion Wa of the workpiece W, which is not the machining target portion, is inserted through the rotor 133 of the measuring jig 4. Then, as shown in Fig. 10(b), the rotor 133 is fixed to the workpiece W by the lock nut 134.

[0068] Then, the housing 131 of the measuring jig 4 is attached to the table 20. The workpiece W, to which the rotor 133 has been attached, is held by the spindle device 30 and the tailstock device 40. At this time, as shown in Fig. 10(b), the position of the housing 131 is adjusted such that the outer peripheral surface of the rotor 133 is positioned to face the inner peripheral surface of the housing 131 of the measuring jig 4.

[0069] Subsequently, grinding is started (S2). That is, the outer peripheral surface of the machining target portion Wb of the workpiece W is ground by moving the grinding wheel T in the X-axis direction while rotating the workpiece W and the grinding wheel T.

[0070] Subsequently, a vibration force is applied by the measuring jig 4 (S3). The vibration force is applied by the measuring jig 4 while the grinding wheel T is grinding the workpiece W. The vibration force can be applied by pulse vibration, or it can be applied by sweep vibration in which the frequency of an applied vibration is continuously changed. The vibration force is applied by the control device 136 of the measuring jig 4 by supplying a current to the electromagnet 132. Then, the vibration force is controlled according to the current supplied to the electromagnet 132 by the control device 136.

[0071] Subsequently, a radial displacement of the rotor 133 is measured by the displacement sensor 135 of the measuring jig 4 (S4) when the vibration force is applied while grinding is performed. The displacement of the rotor 133 coincides with a radial displacement of a portion of the workpiece W fixed to the rotor 133. Thus, the displacement sensor 135 of the measuring jig 4 measures a radial displacement that occurs in the workpiece W when the vibration force is applied to the workpiece W.

[0072] When the measurement by the displacement sensor 135 is finished, the grinding is stopped (S5).

[0073] Next, the total dynamic stiffness data (Ccom, Kcom) during grinding are calculated (S6). The total dynamic stiffness data (Ccom, Kcom) are total dynamic stiffness data (composite data) represented by the dynamic contact stiffness data (Ci(Z'), Ki(Z')), the dynamic workpiece fixture stiffness data (Cw, Kw), and the dynamic tool fixture stiffness data (Ct, Kt) described above. The total dynamic stiffness data (Ccom, Kcom) is represented as a value obtained by adding the dynamic contact stiffness data (Ci(Z'), Ki(Z')), the dynamic workpiece holder stiffness data (Cw, Kw), and the dynamic tool holder stiffness data (Ct, Kt) described above.

[0074] As described above, the radial displacement measured by the displacement sensor 135 of the measuring jig 4 is measured when the vibration force is applied to the workpiece W while grinding is performed. Thus, the measured displacement is influenced by the dynamic contact stiffness data (Ci(Z'), Ki(Z')), the dynamic workpiece fixture stiffness data (Cw, Kw), and the dynamic tool fixture stiffness data (Ct, Kt). Consequently, the calculation of the dynamic total stiffness data (Ccom, Kcom) results in data generated based on the relationship between the vibration force and the radial displacement of the workpiece W when the vibration force is applied to the workpiece W while grinding is performed.

[0075] Next, the dynamic workpiece clamping stiffness data (Cw, Kw) and the dynamic tool clamping stiffness data (Ct, Kt) are acquired (S7). The dynamic workpiece clamping stiffness data (Cw, Kw) and the dynamic tool clamping stiffness data (Ct, Kt) are obtained in advance through a tapping test, etc.

[0076] Next, the dynamic contact stiffness data (Ci(Z'), Ki(Z')) are calculated (S8). The dynamic contact stiffness data (Ci(Z'), Ki(Z')) are calculated by subtracting the dynamic workpiece fixture stiffness data (Cw, Kw) and the dynamic tool fixture stiffness data (Ct, Kt) from the total dynamic stiffness data (Ccom, Kcom).

[0077] Subsequently, an interpolation process is performed on the dynamic contact stiffness data (Ci(Z'), Ki(Z')) (S9). The interpolation process is a process in which dynamic contact stiffness data (Ci, Ki) obtained through actual measurement are used to determine the dynamic contact stiffness data (Ci(Z'), Ki(Z')) under grinding conditions different from the actual measurement. For example, an experimental expression defining the relationship between the contact arc length L, the damping coefficient Ci, and the spring constant Ki can be used. An experimental expression, machine learning, theoretical calculation, etc. can be applied to the interpolation process.With the obtained dynamic contact stiffness data (Ci(Z'), Ki(Z')), it is possible to determine the dynamic contact stiffness correspondence relationship with respect to the machining condition index (the grinding efficiency) obtained in parts (a) and (b) according to . Fig. 6 is shown. 5-3. Dynamic workpiece holder stiffness

[0078] The dynamic workpiece holder stiffness is a dynamic stiffness with respect to a holder in the spindle device 30 and the tailstock 40, which is Fig. 1, wherein it is shown when the workpiece W is held by the spindle device 30 and the tailstock device 40, which serve as the workpiece holding device constituting the grinding machine 2. The dynamic workpiece holding stiffness is defined by a damping coefficient Cw and a spring constant Kw, as shown in Fig. 5. The damping coefficient Cw is a value representing the relationship between the relative speed of the workpiece W with respect to the reference positions of the spindle device 30 and the tailstock device 40 and an external force received by the workpiece W. The spring constant Kw is a value representing the relationship between the relative position of the workpiece W with respect to the reference positions of the spindle device 30 and the tailstock device 40 and an external force received by the workpiece W.

[0079] As described above, the dynamic workpiece support rigidity data (Cw, Kw) is stored in the dynamic workpiece support rigidity table storage unit 103c in association with the machining conditions described above. For example, in a case where the tailstock center 41 is capable of controlling the pressing force for the workpiece W in the axial direction of the workpiece W, the dynamic workpiece support rigidity data (Cw, Kw) is data that changes when the contact state between the tailstock center 41 and the workpiece W changes due to a change in the pressing force of the tailstock center 41.The dynamic workpiece support stiffness data (Cw, Kw) can be obtained, for example, by performing a tapping test while changing the pushing force of the tailstock center 41 with the workpiece W held by the spindle center 34 and the tailstock center 41.

[0080] The dynamic workpiece support stiffness determining unit 123 determines the dynamic workpiece support stiffness data (Cw, Kw) associated with the machining condition acquired by the machining condition acquiring unit 106 from a dynamic workpiece support stiffness table stored in the dynamic workpiece support stiffness table storage unit 103c. 5-4.Workpiece mass

[0081] The analytical workpiece mass (M'w(Z')) is an analytical mass of the workpiece W and is a value correlated with the machining state index. A mass correspondence relationship, which is a correspondence relationship between the analytical workpiece mass (M'w(Z')) and the machining state index, is stored in the workpiece mass table storage unit 103b, which serves as the first correspondence relationship storage unit. The machining state index in the mass correspondence relationship may be the same as that in the case of the aforementioned dynamic contact stiffness correspondence relationship.

[0082] Fig. Figure 11 shows an example of the mass correspondence relationship, which is the correspondence relationship between the machining state index and the analytical workpiece mass (M'w(Z')). As shown in Fig. As shown in Figure 11, the analytical workpiece mass (M'w(Z')) has a nonlinear relationship instead of a linear relationship (proportional relationship) with respect to the grinding efficiency Z', which serves as the machining state index. Specifically, the mass correspondence relationship, which is the correspondence relationship between the machining state index and the analytical workpiece mass (Mw(Z')), is a relationship in which the degree of change in the analytical workpiece mass (Mw(Z')) varies with respect to the machining state index. For example, in a quadratic plane with the machining state index on the horizontal axis and the analytical workpiece mass (M'w(Z')) on the vertical axis, a function representing a curve with a continuously changing slope can be defined as an approximate expression. The approximate expression can be a higher-order function.For example, the curve shown in . Fig. 11, a curve defined by a cubic function. The mass correspondence relationship may be represented by connecting a plurality of straight lines on the quadratic plane instead of the curve. The mass correspondence relationship may be in the form of a data table including a plurality of data correspondence relationships, rather than being defined as a function such as an approximate expression.

[0083] Fig. Figure 11 shows the case where the machining condition index is the grinding efficiency Z'. Even in the case where the machining condition index is the contact arc length L or g / a, the mass correspondence relationship between the machining condition index and the analytical workpiece mass (Mw(Z')) shows roughly the same tendency as that in the case of the grinding efficiency Z' shown in Fig. 11. However, the machining condition index is preferably the grinding efficiency Z as in the case of the dynamic contact stiffness correspondence relationship.

[0084] The machining state index is acquired by the machining state index acquisition unit 125, and the mass correspondence relationship, which is the correspondence relationship between the machining state index and the analytical workpiece mass (M'w(Z')), is stored in the first correspondence relationship storage unit 103b. The analytical workpiece mass (M'w(Z)) is determined by the workpiece mass determination unit 122 based on the machining state index acquired by the machining state index acquisition unit 125. That is, the machining state index acquisition unit 125, the first correspondence relationship storage unit 103b, and the workpiece mass determination unit 122 constitute the workpiece mass determination device 131. 5-5. Analytical workpiece mass procurement process for generating the mass correspondence relationship

[0085] The analytical workpiece mass (M'w(Z')) in the mass correspondence relationship is generated based on dynamic non-machining workpiece characteristics (Mw, Cw, Kw) and the dynamic contact stiffness data (Ci(Z), Ki(Z')). A workpiece mass acquisition process for generating the mass correspondence relationship is described below with reference to a flowchart shown in Fig. 12 is described.

[0086] In step S11, which is Fig. 12, dynamic machining characteristics at a detection position We of the displacement sensor 135 are first actually measured using the vibration device 4 in each of a plurality of states in which the grinding efficiency Z' is changed by the process shown in Fig. 8. Since the grinding efficiency Z' is changed at this time, the grinding resistance changes in correlation with the grinding efficiency Z'. Consequently, the grinding resistance can be represented by Fn (Z').

[0087] Next, in step S12, non-machining dynamic characteristics (Mw, Cw, Kw) at the detection position We of the displacement sensor 135 are analyzed. The dynamic characteristics are set as initial dynamic characteristics (initial mass Mw, Cw, Kw) using, for example, actually measured values in a knock test during the non-machining period.

[0088] In step S13, the dynamic contact stiffness data (Ci(Z'), Ki(Z')) are identified so that the dynamic non-machining characteristics (initial mass Mw, Cw, Kw) at the detection position We of the displacement sensor 135 match the dynamic machining characteristics at each of the plurality of grinding efficiencies Z' at the detection position We of the displacement sensor 135. Specifically, in step S13, the initial masses Mw, Cw, and Kw are set to fixed parameters, Ci(Z') and Ki(Z') are set to variable parameters, and an analysis model is generated by adding the dynamic contact stiffness data (Ci(Z'), Ki(Z')) to the dynamic non-machining characteristics (initial mass Mw, Cw, Kw).The dynamic contact stiffness data (Ci(Z'), Ki(Z')) are identified so that the dynamic characteristics of the analysis model (initial mass Mw, Cw, Kw, Ci(Z'), Ki(Z')) match the dynamic machining characteristics at each of the plurality of grinding efficiencies Z'.

[0089] It has been found that the vibration force frequency compliance characteristics using the dynamic characteristics of the analysis model (Mw, Cw, Kw, Ci(Z'), Ki(Z')) do not completely agree with the vibration force frequency compliance characteristics during machining at each of the plurality of grinding efficiencies Z', which were actually measured values. Therefore, the workpiece mass Mw in the dynamic characteristics of the analysis model is set as a corrected workpiece mass M'w(Z'), which is a variable parameter, and the identification process is performed on the analytical corrected workpiece mass (M'w(Z')) at the machining point position Wb, so that the dynamic characteristics of the analysis model agree with the dynamic machining characteristics at each of the plurality of grinding efficiencies Z'.

[0090] That is, in step S14, the dynamic characteristics of the analysis model are defined as (M'w(Z'), Cw, Kw, Ci(Z'), Ki(Z')), Cw, Kw, Ci(Z'), Ki(Z') are set to fixed parameters, and M'w(Z') is set to a variable parameter. Then, the corrected analytical workpiece mass (M'w(Z')) at the machining point position is determined such that the dynamic characteristics of the analysis model match the dynamic machining characteristics at each of the plurality of grinding efficiencies Z'.

[0091] The corrected analytical workpiece mass (M'w(Z')) is represented by the following expression (1) based on the equation of motion. M'w(Z')x¨1=−Kwx1−Cwx˙1−Ki(Z')(x1−x2)−Ci(Z')(x˙1−x˙2)−Fn(Z')

[0092] As shown in expression (1), the analytical workpiece mass (M'w(Z')) is correlated with the machining efficiency (grinding efficiency) Z', and the dynamic contact stiffness data (Ci(Z'), Ki(Z')) are also correlated with the machining efficiency (grinding efficiency) Z'.

[0093] In the present embodiment, the detection position We of the displacement sensor 135 and the machining point position Wb are different positions, but the two positions may be the same. 5-6. Dynamic tool holder stiffness

[0094] The dynamic tool holder stiffness is a dynamic stiffness with respect to a holder of the grindstone head body 51 which is in Fig. 1, wherein it is shown when the grinding wheel T is held by the grindstone head body 51 serving as the grinding wheel holding device constituting the grinding machine 2. The dynamic tool holding stiffness is defined by a damping coefficient Ct and a spring constant Kt as shown in Fig. 5. The damping coefficient Ct is a value representing the relationship between the relative speed of the grinding wheel T with respect to the reference position of the grindstone head body 51 and an external force received by the grinding wheel T. The spring constant Kt is a value representing the relationship between the relative position of the grinding wheel T with respect to the reference position of the grindstone head body 51 and an external force received by the grinding wheel T.

[0095] As described above, the dynamic tool holder rigidity data (Ct, Kt) are stored in the dynamic tool holder rigidity table storage unit 103d in association with the above-mentioned machining condition. The dynamic tool holder stiffness table storage unit 103d stores the dynamic tool holder stiffness data (Ct, Kt) for each type of the grinding wheel T, for example. In a configuration where the grinding wheel T is supported by a hydrostatic bearing, if the pressure of the hydrostatic bearing can be controlled and the dynamic tool holder stiffness data (Ct, Kt) changes depending on the machining condition, the dynamic tool holder stiffness table storage unit 103d can store the correspondence relationship between the machining condition and the dynamic tool holder stiffness data (Ct, Kt).

[0096] The dynamic tool holder stiffness determination unit 124 determines the dynamic tool holder stiffness data (Cw, Kw) associated with the machining condition acquired by the machining condition acquisition unit 106 from a dynamic tool holder stiffness table stored in the dynamic tool holder stiffness table storage unit 103d. A tool mass Ms of the tool T is represented by the following expression (2) based on the equation of motion. Msx¨2=−Ksx2−Csx˙2−Kcon(Z')(x2−x1)−Ccon(Z')(x˙2−x˙1)+Fn(Z') 6. Correction amount calculation unit 108

[0097] The correction amount calculation unit 108 calculates a correction amount for a relative displacement of the grinding wheel T and the workpiece W in the X-axis direction due to the grinding resistance based on the dynamic stiffness data and the analytical workpiece mass (M'w(Z')) acquired by the dynamic characteristic determination unit 107. The correction amount regarding the displacement can be determined from the dynamic stiffness data, the analytical workpiece mass (M'w(Z')), and the grinding resistance. That is, the offset correction amount can be calculated from the grinding resistance, the dynamic contact stiffness data (Ci(Z'), Ki(Z')), the dynamic workpiece fixture stiffness data (Cw, Kw), the dynamic tool fixture stiffness data (Ct, Kt), and the analytical workpiece mass (M'w(Z')).

[0098] The correction amount calculation unit 108 outputs the calculated correction amount to the estimation unit 102. As described above, the estimation unit 102 estimates the estimation targets based on the relative positions of the workpiece W and the grinding wheel T, the outer peripheral surface shape of the workpiece W, and the outer peripheral surface shape of the grinding wheel T, which are acquired by the command value acquisition unit 101. However, the relative positions of the workpiece W and the grinding wheel T are different from the relative positions corresponding to the command value due to the grinding resistance.

[0099] Therefore, when estimating the estimation targets, the estimation unit 102 uses relative positions obtained by adding the correction amount calculated by the correction amount calculation unit 108 in addition to the relative positions acquired by the command value acquisition unit 101 as the relative positions of the workpiece W and the grinding wheel T. That is, the estimation unit 102 estimates the estimation targets based on the relative positions corresponding to the command value and the correction amount calculated using the dynamic stiffness data.

[0100] Specifically, in the first embodiment, the correction amount calculation unit 108 outputs the calculated correction amount to the interference amount calculation unit 111 of the estimation unit 102. As described above, the interference amount calculation unit 111 calculates the interference amount between the workpiece W and the grinding wheel T based on the relative positions of the workpiece W and the grinding wheel T, the outer peripheral surface shape of the workpiece W, and the outer peripheral surface shape of the grinding wheel T, which are acquired by the command value acquisition unit 101. However, the relative positions of the workpiece W and the grinding wheel T are different from the relative positions according to the command value due to the grinding resistance.

[0101] Therefore, the interference amount calculation unit 111 uses the relative positions obtained by adding the correction amount calculated by the correction amount calculation unit 108 to the relative positions acquired by the command value acquisition unit 101 as the relative positions of the workpiece W and the grinding wheel T to be used to calculate the interference amount. That is, the interference amount calculation unit 111 calculates the interference amount based on the relative positions corresponding to the command value and the correction amount calculated using the dynamic stiffness data.

[0102] In order for the superposition amount calculation unit 111 to calculate a superposition amount determined taking the correction amount into consideration, the grinding efficiency calculation unit 112, the grinding characteristic determination unit 113, and the grinding resistance calculation unit 114 obtain the grinding efficiency Z', the grinding characteristic kc, and the grinding resistance Fn obtained based on the superposition amount determined taking the correction amount into consideration.

[0103] The output unit 109 outputs the estimation targets estimated by the estimation unit 102. That is, the output unit 109 estimates at least one of the state of the workpiece W or the grinding wheel T during grinding, the shape of the workpiece W, the shape of the grinding wheel T, and the mechanical state of the machining system 1 (corresponding to the mechanical state of the grinding machine 2). The output unit 109 can teach the estimation result to, for example, a teaching device (not shown).

[0104] The machining condition optimization unit 110 optimizes the machining condition based on the estimation result obtained by the estimation unit 102. Then, the machining condition optimization unit 110 can output the optimized machining condition to the control device 3a for the grinding machine 2. In this case, the control device 3a can perform grinding using the optimized machining condition. In addition, the control device 3a can control machining using the various types of dynamic stiffness data and the analytical workpiece mass (M'w(Z')) determined by the dynamic characteristic determination unit 107, regardless of the estimation result. 7. Actions and effects

[0105] In the workpiece mass determination device 131 according to the first embodiment, the analytical workpiece mass (M'w(Z')) is determined based on the stored mass correspondence relationship, which is the correspondence relationship between the machining state index and the analytical workpiece mass (M'w(Z')), and the acquired machining state index. Thus, the analytical workpiece mass (M'w(Z')) can be determined with high accuracy based on the correspondence relationship with the machining state index.

[0106] When the analytical workpiece mass (M'w(Z')) determined with high accuracy is used to estimate the machining result of the workpiece W in combination with the dynamic contact stiffness data (Ci(Z'), Ki(Z')) between the workpiece W and the tool T shown by the contact between the workpiece W and the tool T during machining, the accuracy of estimating the machining result is expected to increase.

[0107] In the workpiece mass determination device 131 according to the first embodiment, the analytical workpiece mass (M'w(Z')) is generated in the mass correspondence relationship based on the dynamic non-machining workpiece characteristics (Mw, Cw, Kw) and the dynamic contact stiffness data (Ci(Z'), Ki(Z')). Thus, the change in the analytical workpiece mass (M'w(Z')) can be more accurately obtained. Consequently, the analytical workpiece mass (M'w(Z')) can be determined with high accuracy.

[0108] In the workpiece mass determination device 131 according to the first embodiment, the dynamic contact stiffness data (Ci(Z'), Ki(Z')) is data generated from the relationship between the vibration force applied to the workpiece W and the displacement of the workpiece W when the vibration force is applied to the workpiece W while the workpiece W is being machined by the tool T. Thus, the dynamic contact stiffness data (Ci(Z'), Ki(Z')) accurately indicates the dynamic stiffness between the workpiece W and the grinding wheel T. Consequently, the analytical workpiece mass (M'w(Z')) can be determined with high accuracy.

[0109] In the workpiece mass determination device 131 according to the first embodiment, the mass correspondence relationship is defined as the approximate expression of the function representing a curve with a continuously changing slope in the quadratic plane with the machining state index on the horizontal axis and the analytical workpiece mass on the vertical axis. By defining the mass correspondence relationship as the approximate expression of the function representing the curve, which is a nonlinear relationship, the change in the analytical workpiece mass can be obtained more accurately. Consequently, the analytical workpiece mass (M'w(Z')) can be determined with high accuracy.

[0110] In the workpiece mass determination device 131 according to the first embodiment, the machining state index is the machining efficiency of the tool T for the workpiece W. Since the machining efficiency is closely related to the machining state of the workpiece W, the analytical workpiece mass (Mw(Z')) can be determined with high accuracy according to the machining state of the workpiece W by using the machining efficiency as the machining state index.

[0111] In the workpiece mass determination device 131 according to the first embodiment, the machining device 2 is the cylindrical grinder that grinds the cylindrical outer peripheral surface of the workpiece W using the grinding wheel T serving as the tool, and includes the workpiece support device including the spindle device 30 that holds and rotatably drives one axial end of the workpiece W, and the tailstock center 41 that holds the other axial end of the workpiece W. The machining state index is the grinding efficiency Z of the grinding wheel T for the workpiece W. By using the grinding efficiency as the machining state index, the analytical workpiece mass (M'w(Z')) easily fits the curve represented by the cubic function.Consequently, the approximate expression is generated in a simple manner, and the analytical workpiece mass (M'w(Z')) can be determined with higher accuracy.

[0112] In the workpiece mass determination device 131 according to the first embodiment, the machining device 2 is the cylindrical grinder that grinds the cylindrical outer peripheral surface of the workpiece W using the grinding wheel T serving as the tool, and includes the workpiece support device including the spindle device 30 that holds and rotatably drives one axial end of the workpiece W, and the tailstock center 41 that holds the other axial end of the workpiece W. The machining state index is the contact arc length L of the grinding wheel T with the workpiece W. Thus, the machining state index can be easily obtained, and the calculation load can be reduced.

[0113] The machining estimation device 3b according to the first embodiment includes the workpiece mass determination device 131, and estimates the result of machining of the workpiece W by the machining device 2. The machining estimation device 3b further includes the second correspondence relationship storage unit 103a that stores the dynamic contact stiffness correspondence relationship, which is the correspondence relationship between the machining state index (Z') and the dynamic contact stiffness data (Ci(Z'), Ki(Z')), the dynamic contact stiffness determination unit 121 that determines the dynamic contact stiffness data (Ci(Z'), Ki(Z')) based on the machining state index (Z') acquired by the machining state index acquisition unit 125 and the dynamic contact stiffness correspondence relationship, and the estimation unit 102.which estimates the machining result of the workpiece W using the dynamic contact stiffness data (Ci(Z'), Ki(Z')) determined by the dynamic contact stiffness determination unit and the analytical workpiece mass (M'w(Z')) determined by the workpiece mass determination unit 122. By determining the analytical workpiece mass (M'w(Z')) based on the correspondence relationship with the machining state index, the change in the analytical workpiece mass (M'w(Z')) is reflected in the estimation of the machining result. Consequently, the machining result can be estimated with higher accuracy.

[0114] In the machining estimation device 3b according to the first embodiment, the dynamic contact stiffness data in the dynamic contact stiffness correspondence relationship is data generated from the relationship between the vibration force applied to the workpiece W and the displacement of the workpiece W when the vibration force is applied to the workpiece W while the workpiece W is being machined by the tool T. Thus, the dynamic contact stiffness data (Ci(Z'), Ki(Z')) accurately indicates the dynamic stiffness between the workpiece W and the grinding wheel T. Consequently, the machining result can be estimated with higher accuracy.

[0115] The machining estimation apparatus 3b according to the first embodiment further includes the dynamic workpiece holding stiffness determining unit 123 that determines the dynamic workpiece holding stiffness data shown in the workpiece holding device 30, 40 constituting the machining apparatus 2 when the workpiece W is held by the workpiece holding device 30, 40, the dynamic tool holding stiffness determining unit 124 that determines the dynamic tool holding stiffness data shown in the tool holding device 51 constituting the machining apparatus 2 when the tool T is held by the tool holding device 51, and the correction amount calculating unit 108 that calculates the correction amount for the relative positions of the tool T and the workpiece W based on the dynamic contact stiffness data, (Ci(Z'), Ki(Z')),The dynamic tool holder stiffness data (Ct, Kt), the dynamic workpiece holder stiffness data (Cw, Kw), and the analytical workpiece mass (M'w(Z')) are calculated. The estimation unit 102 estimates the machining result of the workpiece W by the tool T based on the correction amount and the command value for machining the workpiece W. Since the analytical workpiece mass (M'w(Z')), which is calculated with high accuracy, is used to calculate the correction amount for the relative positions of the tool T and the workpiece W, the machining estimation device 3b can estimate the machining result of the workpiece W with high accuracy.

[0116] In the machining system 1 according to the first embodiment, the machining estimation device 3b further includes the machining condition optimization unit 110 that optimizes the machining condition for the workpiece W based on the machining result estimated by the estimation unit 102, and the machining device 2 is configured to machine the workpiece W using the tool T based on the optimized machining condition. Thus, the workpiece W can be machined under the machining condition optimized based on the machining result estimated with high accuracy. Consequently, a highly accurate workpiece W can be stably manufactured, and the manufacturing cost can be reduced.

[0117] As described above, according to the above-described configuration, it is possible to provide the workpiece mass determination device 131 capable of determining the analytical workpiece mass with high accuracy, and to provide the machining estimation device 3b and the machining system 1.

[0118] As an alternative to the first embodiment, in a modification shown in Fig. 13, the machining device 2 comprises a support device 70. As shown in Fig. 14, the support device 70 includes a first arm 71 and a second arm 72. Both arms 71, 72 slidably hold a lower portion W1 of the workpiece W and a portion W2 of the workpiece W opposite to the tool T. The support device 70 prevents the workpiece W from being deformed away from the tool T during machining.

[0119] When the workpiece W is held by the support device 70, the dynamic characteristics of the machining point Wa change. Consequently, the analytical workpiece mass (M'w(Z')) also changes. The dynamic characteristic determination unit 107 can determine the dynamic characteristics taking this into account. In this case, too, the same actions and effects as those in the first embodiment can be achieved. When the support device 70 is provided, the workpiece W can be held by either a single-sided fixture or a double-sided fixture.

[0120] The above-described embodiment illustrates the example regarding cutting using grinding with the grinding machine 2 serving as the machining device. In addition, cutting using a lathe or a turning center is similarly applicable. In the case of cutting, cutting efficiency, cutting depth, etc., can be used as the machining condition index. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2015-208812

[0003] JP 2015 - 208 812 A

[0003]

Claims

[1] A workpiece mass determination device (131) configured to calculate an analytical workpiece mass (M'w(Z')) for analyzing dynamic characteristics during machining in a machining device (2) configured to machine a workpiece (W) using a tool (T), the workpiece mass determination device comprising: a first correspondence relationship storage unit (103b) configured to store a mass correspondence relationship that is a correspondence relationship between the analytical workpiece mass (M'w(Z')) and a machining state index (Z') that changes depending on a state of machining of the workpiece by the tool; a machining state index acquisition unit (125) configured to acquire the machining state index (Z'); and a workpiece mass determination unit (122) configured to determine the analytical workpiece mass (M'w(Z')) based on the acquired machining state index (Z') and the mass correspondence relationship. [2] A workpiece mass determining apparatus according to claim 1, wherein the analytical workpiece mass (M'w(Z')) in the mass correspondence relationship is generated based on a non-machining dynamic workpiece stiffness (Cw, Kw) and dynamic contact stiffness data (Ci(Z'), Ki(Z')) exhibited between the workpiece and the tool by a contact between the workpiece and the tool during machining. [3] The machining estimation apparatus according to claim 3, wherein the dynamic contact stiffness data is data generated from a relationship between a vibration force applied to the workpiece and a displacement of the workpiece when the vibration force is applied to the workpiece while the workpiece is machined by the tool. [4] A workpiece mass determining device according to any one of claims 1 to 3, wherein the mass correspondence relationship is defined as an approximate expression of a function representing a curve having a continuously changing slope in a quadratic plane with the machining state index on a horizontal axis and the analytical workpiece mass (M'w(Z')) on a vertical axis. [5] The workpiece mass determining device according to any one of claims 1 to 3, wherein the machining state index is a machining efficiency of the tool for the workpiece. [6] Workpiece mass determining device according to one of claims 1 to 3, wherein the machining device (2) is a cylindrical grinding machine configured to grind a cylindrical outer peripheral surface of the workpiece using a grinding wheel serving as the tool, and comprises a workpiece holding device including a spindle device (30) configured to hold and rotatably drive one axial end of the workpiece, and a tailstock center point (41) configured to hold the other axial end of the workpiece, and the machining condition index is a grinding efficiency (Z') of the grinding wheel for the workpiece. [7] Workpiece mass determining device according to one of claims 1 to 3, wherein the machining device (2) is a cylindrical grinding machine configured to grind a cylindrical outer peripheral surface of the workpiece using a grinding wheel serving as the tool, and comprises a workpiece holding device including a spindle device (30) configured to hold and rotatably drive one axial end of the workpiece, and a tailstock center point (41) configured to hold the other axial end of the workpiece, and the machining condition index is a contact arc length (L) of the grinding wheel with the workpiece. [8] A machining estimation device (3b) comprising the workpiece mass determining device according to claim 1 and configured to estimate a result of machining of the workpiece (W) by the machining device (2), the machining estimation device comprising: a second correspondence relationship storage unit (103a) configured to store a dynamic contact stiffness correspondence relationship, which is a correspondence relationship between the machining state index (Z') and the dynamic contact stiffness data (Ci(Z'), Ki(Z')) exhibited between the workpiece and the tool by contact between the workpiece and the tool during machining; a dynamic contact stiffness determination unit (121) configured to determine the dynamic contact stiffness data (Ci(Z'), Ki(Z')) based on the machining state index (Z') acquired by the machining state index acquisition unit and the dynamic contact stiffness correspondence relationship; and an estimation unit (102) configured to estimate the result of machining the workpiece using the dynamic contact stiffness data (Ci(Z'), Ki(Z')) determined by the dynamic contact stiffness determination unit and the analytical workpiece mass (M'w(Z')) determined by the workpiece mass determination unit. [9] The machining estimation apparatus according to claim 8, wherein the dynamic contact stiffness data in the dynamic contact stiffness correspondence relationship is data generated from a relationship between a vibration force applied to the workpiece and a displacement of the workpiece when the vibration force is applied to the workpiece while the workpiece is machined by the tool. [10] A machining estimation apparatus according to claim 8, further comprising: a dynamic workpiece holding rigidity determining unit (123) configured to determine dynamic workpiece holding rigidity data exhibited in a workpiece holding device (30, 40) constituting the machining apparatus when the workpiece is held by the workpiece holding device; a dynamic tool holding rigidity determining unit (124) configured to determine dynamic tool holding rigidity data exhibited in a tool holding device (51) constituting the machining apparatus when the tool is held by the tool holding device; and a correction amount calculation unit (108) configured to calculate a correction amount for relative positions of the tool and the workpiece based on the dynamic contact stiffness data, the dynamic workpiece holder stiffness data, the dynamic tool holder stiffness data, and the analytical workpiece mass (M'w(Z')), wherein the estimation unit is configured to estimate the result of machining the workpiece by the tool based on the correction amount and a command value for machining the workpiece. [11] Machining system (1) with: the machining estimation device according to any one of claims 8 to 10, wherein the machining estimation device further comprises a machining condition optimization unit (110) configured to optimize a machining condition for the workpiece based on the result of machining estimated by the estimation unit; and the machining device configured to machine the workpiece using the tool based on the optimized machining condition.

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