Contact dynamic rigidity calculation system, processing estimation device, and processing system

Abstract

To provide a contact dynamic rigidity calculation system which can calculate contact dynamic rigidity with higher accuracy.SOLUTION: A contact dynamic rigidity calculation system 130 includes: a correspondence relation storage unit 103 which stores a correspondence relation between a processing state index which changes according to a state of processing of a workpiece by a tool and contact dynamic rigidity data; a processing state index acquisition unit 124 which acquires the processing state index; a contact dynamic rigidity determination unit 121 which determines the contact dynamic rigidity data based on the acquired processing state index and the correspondence relation; a contact rigidity deflection acquisition unit 125 which acquires a contact rigidity deflection between the tool and the workpiece based on a workpiece deflection, a tool deflection, a total cutting amount of the tool cutting into the workpiece, and a workpiece removal amount by the tool observed during the processing; a contribution rate acquisition unit 126 which acquires a contribution rate indicating a degree that the contact rigidity deflection contributes to the contact dynamic rigidity data; and a contact dynamic rigidity correction unit 127 which corrects the contact dynamic rigidity data based on the contact rigidity deflection and the contribution rate.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a contact dynamic stiffness calculation system, a machining estimation device, and a machining system. [Background technology]

[0002] The configuration disclosed in Patent Document 1 is a grinding device that grinds a workpiece using a grinding wheel, and it is configured to estimate the processing results with high precision using the contact dynamic stiffness, which is the contact stiffness between the tool and the workpiece during processing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2023 / 047437 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration disclosed in Patent Document 1, the total cutting depth of the workpiece by the tool during machining, which is used to calculate the contact dynamic stiffness, can be expressed as the sum of the deflection of the workpiece, the deflection of the tool, the amount of workpiece removed by the tool, and the contact dynamic stiffness deflection between the tool and the workpiece. However, the inventors of the present application have found that the contact dynamic stiffness deflection changes during the machining process. And, in the configuration disclosed in Patent Document 1, the change in contact dynamic stiffness deflection is not sufficiently taken into consideration when calculating the contact dynamic stiffness, so there is room for improvement in order to improve the calculation accuracy.

[0005] The present invention provides a contact dynamic stiffness calculation system that can calculate contact dynamic stiffness with higher accuracy. [Means for solving the problem]

[0006] One aspect of the present disclosure is 1. A contact dynamic stiffness calculation system for calculating contact dynamic stiffness data between a workpiece and a tool exerted by contact between the workpiece and the tool during machining in a machining device that machines a workpiece with a tool, a correspondence relationship storage unit that stores a correspondence relationship between a machining state index that changes depending on a state of machining of the workpiece by the tool and contact dynamic stiffness data; a machining state index acquisition unit that acquires the machining state index; a contact dynamic stiffness determining unit that determines the contact dynamic stiffness data based on the acquired machining state index and the correspondence relationship; a contact stiffness deflection acquiring unit that acquires contact stiffness deflection between the tool and the workpiece based on workpiece deflection, which is deflection of the workpiece during machining, tool deflection, which is deflection of the tool, a total cutting amount of the tool into the workpiece, and an amount of workpiece removed by the tool; a contribution rate acquisition unit that acquires a contribution rate indicating a degree to which the contact stiffness deflection contributes to the contact dynamic stiffness data; and a contact dynamic stiffness correcting section that corrects the contact dynamic stiffness data determined by the contact dynamic stiffness determining section based on the contact stiffness deflection and the contribution rate. [Effects of the Invention]

[0007] According to the above aspect, the contact dynamic stiffness data determined based on the pre-stored correspondence relationship between the machining state index and the contact dynamic stiffness data and the acquired machining state index is corrected based on the contact stiffness deflection between the tool and the workpiece and the contribution rate indicating the degree to which the contact stiffness deflection contributes to the contact dynamic stiffness data. Therefore, the corrected contact dynamic stiffness data fully takes into account changes in the contact dynamic stiffness deflection, thereby improving the calculation accuracy of the contact dynamic stiffness.

[0008] As described above, according to the above aspect, it is possible to provide a contact dynamic stiffness calculation system that can calculate contact dynamic stiffness with higher accuracy. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing a machining system including a contact dynamic stiffness calculation system and a machining estimation device according to a first embodiment. [Figure 2] FIG. 2 is a functional block diagram of a contact dynamic stiffness calculation system and a processing estimation device according to the first embodiment. [Figure 3] 3 is a conceptual diagram showing the interference state between a workpiece and a grinding wheel during grinding in the first embodiment. FIG. [Figure 4] FIG. 1 is a conceptual diagram showing the shape of a workpiece in a grinding simulation of embodiment 1 represented by a group of radial line segments, and illustrating the state in which the workpiece represented by the radial line segments interferes with the outer peripheral line of the grinding wheel during grinding. [Figure 5] 3A to 3C are conceptual diagrams showing contact dynamic stiffness, workpiece support dynamic stiffness, and tool support dynamic stiffness in grinding processing according to the first embodiment. [Figure 6] 1A is a diagram showing a first example of the correspondence relationship between the processing state index and the contact dynamic stiffness data in the first embodiment, and FIG. 1B is a diagram showing a second example of the correspondence relationship between the processing state index and the contact dynamic stiffness data in the first embodiment. [Figure 7] 10A is a diagram showing a third example of the correspondence relationship between the processing state index and the contact dynamic stiffness data in the first embodiment, and FIG. 10B is a diagram showing a fourth example of the correspondence relationship between the processing state index and the contact dynamic stiffness data in the first embodiment. [Figure 8] 10 is a flowchart showing a process of acquiring contact dynamic stiffness data for creating a correspondence relationship. [Figure 9] FIG. 10 is a plan view of the grinding machine when obtaining the contact dynamic stiffness for creating the correspondence relationship. [Figure 10] 10A and 10B are diagrams showing the state of the grinding machine in a part of the process of acquiring contact dynamic stiffness for creating a correspondence relationship. [Figure 11] (a) First conceptual diagram showing the interference state between the workpiece and the grinding wheel to explain the contribution rate, (b) Second conceptual diagram with the interference area enlarged, and (c) Third conceptual diagram with the interference area enlarged. [Figure 12] FIG. 10 is a conceptual diagram showing the interference state between the workpiece and the grinding wheel for obtaining the contribution rate. [Figure 13] FIG. 10 is a diagram showing a machining system including a contact dynamic stiffness calculation system and a machining estimation device in a modified embodiment. [Figure 14]10 is a conceptual diagram showing interference between a workpiece, a grinding wheel, and a rest device during grinding in a modified embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Embodiment 1) 1. Configuration of Processing System 1 The contact dynamic stiffness calculation system 130, the processing estimation device 3b, and the processing system 1 in the present embodiment 1 will be described with reference to Fig. 1. The processing system 1 is a processing device that performs grinding. The processing system 1 includes a grinding machine 2 as the processing device and a processing unit 3.

[0011] The grinding machine 2 rotates the workpiece W, rotates a grinding wheel T as a tool that is a rotating body, and moves the grinding wheel T relatively close to the workpiece W in a direction intersecting the axis of the workpiece W, thereby grinding the outer or inner peripheral surface of the workpiece W. The grinding machine 2 can be a table traverse type grinding machine, a wheelhead traverse type grinding machine, or the like. The grinding machine 2 can also be a cylindrical grinding machine, a cam grinding machine, or the like.

[0012] In this embodiment 1, as shown in Fig. 1, the workpiece W has a shaft portion Wa as a non-machined portion and multiple machined portions Wb whose outer circumferential surfaces are to be ground. The machined portions Wb have, for example, a cylindrical outer circumferential surface coaxial with the shaft portion Wa. However, the workpiece W shown in Fig. 1 is just one example, and the grinding machine 2 can grind workpieces having various shapes.

[0013] The processing unit 3 includes a control device 3a that controls the grinding machine 2 and a processing estimation device 3b that estimates the processing result. The control device 3a can control the grinding process by controlling the grinding machine 2. The processing estimation device 3b inputs information used in the grinding process and performs a simulation to estimate the processing result of the workpiece W.

[0014] The processing estimation device 3b can function as a simulation device independent of the grinding machine 2, or as a simulation device that operates in conjunction with the grinding machine 2. In the former case, for example, optimal grinding conditions can be determined without actually grinding the workpiece W. In the latter case, the processing estimation device 3b can, for example, correct the grinding conditions or operate to affect various controls by processing in parallel with the grinding of the workpiece W by the grinding machine 2. The processing estimation device 3b can also be an embedded system in the grinding machine 2 and the control device 3a.

[0015] 2. Configuration of the grinding machine 2 and the control device 3a An example of the configuration 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 exemplified as a table traverse 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 move the grinding wheel T in a direction intersecting the axis of the workpiece W. In addition, in this embodiment 1, the grinding machine 2 is exemplified as a case in which the cylindrical outer peripheral surface of the workpiece W is ground using the grinding wheel T.

[0016] The grinding machine 2 includes a bed 10, a table 20, a spindle device 30, a tailstock device 40, a grinding wheel head 50, a sizing device 60, and a control device 3a. The bed 10 is installed on an installation surface. The bed 10 is formed so that the width (length in the Z-axis direction) of the front side in the X-axis direction (lower side in Fig. 1) is long, and the width of the back side in the X-axis direction (upper side in Fig. 1) is short.

[0017] Bed 10 is provided with a Z-axis guide surface 11 extending in the Z-axis direction on the upper surface on the front side in the X-axis direction. Bed 10 also has a Z-axis drive mechanism 12 that drives along Z-axis guide surface 11. In this first embodiment, Z-axis drive mechanism 12 includes a ball screw mechanism 12a and a Z-axis motor 12b. Ball screw mechanism 12a extends parallel to Z-axis guide surface 11, and Z-axis motor 12b drives ball screw mechanism 12a.

[0018] A Z-axis drive circuit and Z-axis detector 12c (not shown) are provided to drive Z-axis drive mechanism 12. The Z-axis drive circuit includes an amplifier circuit and drives Z-axis motor 12b. In this first embodiment, Z-axis detector 12c is, for example, an angle detector such as an encoder, which detects the angle of the rotation shaft of Z-axis motor 12b. Note that Z-axis drive mechanism 12 may also employ a linear motor or the like instead of the configuration including ball screw mechanism 12a.

[0019] Bed 10 also has a guide surface 13 on the upper surface on the rear side in the X-axis direction, which extends in a direction intersecting the Z-axis direction. In this embodiment 1, guide surface 13 is an X-axis guide surface that extends in the X-axis direction, which is perpendicular to the Z-axis. Bed 10 also has an X-axis drive mechanism 14 that drives along X-axis guide surface 13. In this embodiment 1, X-axis drive mechanism 14 includes a ball screw mechanism 14a and an X-axis motor 14b. Ball screw mechanism 14a extends parallel to X-axis guide surface 13, and X-axis motor 14b drives ball screw mechanism 14a.

[0020] An X-axis drive circuit and an X-axis detector 14c (not shown) 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 this first embodiment, the X-axis detector 14c is, for example, an angle detector such as an encoder, which detects the angle of the rotation shaft of the X-axis motor 14b. Note that the X-axis drive mechanism 14 may also be configured with a linear motor or the like instead of the ball screw mechanism 14a.

[0021] Table 20 is formed in an elongated shape and is supported movably in the Z-axis direction (horizontal left-right direction) on Z-axis guide surface 11 of bed 10. Table 20 is also fixed to a ball screw nut of Z-axis ball screw mechanism 12a, and moves in the Z-axis direction by rotational driving of Z-axis motor 12b.

[0022] The spindle device 30 constitutes a workpiece support device. The spindle device 30 supports the workpiece W and drives it to rotate. The spindle device 30 is disposed on one end side in the Z-axis direction on the table 20. The spindle device 30 includes a spindle housing 31, a spindle 32, a spindle motor 33, a spindle center 34, a spindle detector 35, and a spindle drive circuit (not shown).

[0023] The spindle housing 31 is fixed on the table 20. The spindle 32 is rotatably supported by the spindle housing 31 via a bearing. A spindle motor 33 drives the spindle 32 to rotate. A spindle center 34 supports one axial end face of the workpiece W. The spindle center 34 is fixed to the spindle 32 and is rotatable relative to the spindle housing 31. However, if the spindle unit 30 is equipped with a turning member such as a cage (not shown), the spindle center 34 may be fixed to the spindle housing 31 and installed so as to be non-rotatable relative to the spindle housing 31. Furthermore, the spindle unit 30 may be equipped with a chuck for gripping the workpiece W instead of the spindle center 34. The chuck is rotationally driven by being connected to the spindle 32.

[0024] The spindle detector 35 and the spindle drive circuit are provided to drive the spindle motor 33. In the first embodiment, the spindle detector 35 is, for example, an angle detector such as an encoder, and detects the angle of the rotation shaft of the spindle motor 33. The spindle drive circuit includes an amplifier circuit and drives the spindle motor 33.

[0025] The tailstock device 40, together with the spindle device 30, constitutes a workpiece support device. The tailstock device 40 is arranged on the other end side of the table 20 in the Z-axis direction. The tailstock device 40 is provided so as to be movable in the Z-axis direction on the table 20. The tailstock device 40 is equipped with a tailstock center 41. The tailstock center 41 supports the end face of the other axial end of the workpiece W. The tailstock center 41 may be provided so as to be non-rotatable or so as to be rotatable. Note that when the grinding machine 2 grinds the inner peripheral surface of the workpiece W, the tailstock device 40 is not necessary.

[0026] The tailstock center 41 may be positioned at a fixed position relative to the workpiece W, or may be provided so as to be movable in the axial direction of the workpiece W relative to the workpiece W. In the latter case, the tailstock center 41 may be configured so that the pressing force in the axial direction of the workpiece W against the workpiece W is adjustable. The pressing force can be controlled by means of adjusting a spring force, means of adjusting a fluid pressure, or the like.

[0027] The wheel head 50 is provided with a grinding wheel T as a tool and rotates the grinding wheel T. In addition to the grinding wheel T, the wheel head 50 is provided with a wheel head body 51, a grinding wheel spindle 52, a grinding wheel motor 53, and a grinding wheel drive circuit (not shown).

[0028] The grinding wheel T is formed in a disk shape. The grinding wheel T is used to grind the outer or inner surface of the workpiece W. The grinding wheel T is composed of multiple abrasive grains fixed with a binder. The abrasive grains used include general abrasive grains made of ceramic materials such as alumina and silicon carbide, and super abrasive grains such as diamond and CBN.

[0029] Binders include vitrified (V), resinoid (B), rubber (R), silicate (S), shellac (E), metal (M), electroplated (P), and magnesia cement (Mg). Furthermore, grinding wheels T are available in porous and non-porous configurations. Depending on the type of binder and the presence or absence of pores, grinding wheels T can be elastically deformable or virtually non-elastically deformable. Elastic modulus of elasticity of elastically deformable grinding wheels T varies depending on the type of binder, the presence or absence of pores, and the porosity.

[0030] The wheel head body 51 is formed, for example, in a rectangular shape in a plan view, and is supported on the X-axis guide surface 13 of the bed 10 so as to be movable in the X-axis direction (horizontal front-to-back direction). The wheel head body 51 is also fixed to the ball screw nut of the X-axis ball screw mechanism 14a, and moves in the X-axis direction by the rotational drive of the X-axis motor 14b. The wheel head body 51 constitutes a tool support device that supports the grinding wheel T.

[0031] The grinding wheel spindle 52 is rotatably supported by the wheel head body 51 via a bearing. A grinding wheel T is fixed to the tip of the grinding wheel spindle 52, and the grinding wheel T rotates as the grinding wheel spindle 52 rotates. A grinding wheel motor 53 drives the grinding wheel spindle 52 to rotate. The bearing may be a hydrostatic bearing, a rolling bearing, or the like.

[0032] The grinding wheel motor 53 transmits the rotational driving force to the grinding spindle 52 via, for example, a belt. However, the grinding wheel motor 53 may be arranged coaxially with the grinding spindle 52. In general, the rotation speed of the grinding wheel T driven by the grinding wheel motor 53 is higher than the rotation speed of the workpiece W driven by the spindle motor 33. A 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.

[0033] The sizing device 60 is provided on the upper surface of the bed 10 and measures the outer diameter dimension of the workpiece W. The sizing device 60 is equipped with, for example, a pair of contacts that can come into contact with the outer peripheral surface of the workpiece W, and measures the outer diameter dimension at the contact point with the workpiece W.

[0034] The control device 3a is a CNC (Computer Numerical Control) device and a PLC (Programmable Logic Controller) device that executes machining control. That is, the control device 3a drives the Z-axis drive mechanism 12 and the X-axis drive mechanism 14, which serve as moving devices, based on the grinding program and the measurement results from the sizing device 60, to control the positions of the table 20 and the wheel head 50. That is, the control device 3a controls the positions of the table 20, the wheel head 50, etc., thereby moving the workpiece W and the grinding wheel T closer to or farther apart from each other. Furthermore, the control device 3a controls the spindle device 30 and the wheel head 50. That is, the control device 3a controls the rotation of the spindle 32 and the grinding wheel T.

[0035] 3. Configuration of the processing estimation device 3b 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 contact dynamic stiffness table storage unit (correspondence storage unit) 103, a workpiece support dynamic stiffness table storage unit 104, a tool support dynamic stiffness table storage unit 105, a machining condition acquisition unit 106, a dynamic stiffness determination unit 107, a correction amount calculation unit 108, an output unit 109, a machining condition optimization unit 110, a machining state index acquisition unit 124, a contact stiffness deflection acquisition unit 125, and a contribution rate acquisition unit 126.

[0036] The command value acquisition unit 101 acquires command values for controlling the grinding machine 2 in the grinding process. When the processing estimation device 3b is a simulation device independent of the grinding machine 2, the command value acquisition unit 101 inputs a grinding program and configuration information of the grinding machine 2, and generates command values by calculation for controlling each part of the grinding machine 2. When the processing estimation device 3b functions as a simulation device that operates in conjunction with the grinding process by the grinding machine 2, the command value acquisition unit 101 can acquire command values directly from the control device 3a of the grinding machine 2.

[0037] The estimation unit 102 performs a grinding simulation using the command values acquired by the command value acquisition unit 101, thereby estimating 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.

[0038] The state of the workpiece W includes, for example, the vibration state and temperature state of the workpiece W. The state of the grinding wheel T includes, for example, the vibration state and temperature state of the grinding wheel T, the grinding resistance generated at each part of the outer surface of the grinding wheel T, the sharpness of the grinding wheel T, and the state of the abrasive grains that make up the grinding wheel T. The state of the abrasive grains includes, for example, the average protrusion amount of the abrasive grains and the abrasive grain distribution. The shape of the workpiece W includes the shape at an intermediate stage of the grinding process and the shape at the end of the grinding process. The shape of the grinding wheel T includes the shape at an intermediate stage of the grinding process and the shape at the end of the grinding process. The mechanical state of the grinding machine 2 includes the vibration state and temperature state of the parts that make up the grinding machine 2.

[0039] In the present embodiment 1, the estimation unit 102 performs a grinding simulation in which the shape of the workpiece W changes sequentially, and thereby estimates the shape of the workpiece W, the state of the workpiece W, and the mechanical state of the grinding machine 2 as estimation targets. In the present embodiment 1, the grinding simulation is performed assuming that the grinding wheel T does not deform. Note that the estimation unit 102 can also estimate the grinding resistance generated at each location on the outer peripheral surface of the grinding wheel T in addition to the above estimation targets.

[0040] The estimation unit 102 includes an interference amount calculation unit 111 , a grinding efficiency calculation unit 112 , a grinding characteristic determination unit 113 , and a grinding resistance calculation unit 114 .

[0041] 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 obtained using the command value acquired by the command value acquisition unit 101. The interference amount corresponds to the amount of radial grinding of the workpiece W at each portion in the circumferential direction of the workpiece W. In other words, the interference amount is the amount of removal of the workpiece W ground by the grinding wheel T, more specifically, the amount of radial removal of the workpiece W at each portion in the circumferential direction of the workpiece W. As shown in FIG. 3, the interference amount is the volume of the portion where the workpiece W interferes with the grinding wheel T (the shaded portion in FIG. 3: the interference area).

[0042] The interference amount calculation unit 111 geometrically calculates the amount of interference through arithmetic processing. Here, the interference 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 on the right side of FIG. 4, the outer peripheral surface shape of the workpiece W is expressed by a group of multiple radial line segments on a polar coordinate system with the rotation center Ow of the workpiece W as the origin. In other words, the interference amount calculation unit 111 stores, as the outer peripheral surface shape of the workpiece W, a group of multiple line segments connecting division points (white dots in FIG. 4) on the outer peripheral surface obtained by dividing the workpiece W equiangularly (α) with the rotation center Ow (origin) of the workpiece W. The division points indicated by white dots in FIG. 4 are stored as the outer peripheral surface shape of the workpiece W before removal by the grinding wheel T.

[0043] The interference amount calculation unit 111 determines the intersections (black dots in FIG. 4) between each line segment of the workpiece W and the line representing the outer peripheral surface shape of the grinding wheel T from the relative position (center distance) between the workpiece W and the grinding wheel T and the outer peripheral surface shape of the grinding wheel T. The interference amount calculation unit 111 stores the determined intersections (black dots in FIG. 4) as the outer peripheral surface shape of the workpiece W after it has been removed by the grinding wheel T. In other words, the interference amount calculation unit 111 changes the stored outer peripheral surface shape of the workpiece W.

[0044] The interference amount calculation unit 111 then subtracts the area of a triangle △Ow-b1-b2 formed by points b1 and b2 (intersections with the grinding wheel T) after removal and the origin Ow from the area of a triangle △Ow-a1-a2 formed by adjacent points a1 and a2 among the points defining the outer peripheral surface shape of the workpiece W before removal and the origin Ow. The areas after subtraction are calculated for all adjacent points that define the outer peripheral surface shape of the workpiece W.

[0045] The interference amount calculation unit 111 then adds up the areas after each subtraction and multiplies the total area by the thickness of the workpiece W to calculate the interference amount (removal amount). In the above example, the area of the portion to be removed is calculated by calculating the areas of two types of triangles and then calculating the difference between the areas. Alternatively, the area of the portion to be removed may be calculated by directly calculating the rectangle a1-a2-b1-b2.

[0046] 2, the grinding efficiency calculation unit 112 calculates the grinding efficiency (processing efficiency) Z' based on the interference amount calculated by the interference amount calculation unit 111. The grinding efficiency Z' calculates the volume of the workpiece W removed by the grinding wheel T per unit time and unit width.

[0047] The grinding characteristic determination unit 113 determines the grinding characteristic kc based on the material of the workpiece W, the types of abrasive grains and binder of the grinding wheel T, and the condition of the outer circumferential surface of the grinding wheel T. The condition of the outer circumferential surface of the grinding wheel T is expressed, for example, using an index that indicates the wear state and sharpness of the abrasive grains of the grinding wheel T. Here, the grinding characteristic determination unit 113 stores the grinding characteristics in each state in advance through experiments, analysis, etc.

[0048] Based on the grinding efficiency Z' and the grinding characteristic kc, the grinding resistance calculation unit 114 calculates the grinding resistance Fn in the normal direction (X-axis direction) of the outer peripheral surface of the workpiece W. The grinding resistance Fn is obtained by multiplying the grinding efficiency Z' by the grinding characteristic kc (Fn = kc × Z').

[0049] The grinding characteristics kc have a substantially linear relationship such that the grinding resistance Fn in the normal direction (X-axis direction) increases as the grinding efficiency Z' increases. The grinding characteristics kc change in this relationship, for example, when the grinding wheel T is worn. For example, when the grinding wheel T is worn, the grinding resistance Fn in the normal direction changes to increase with respect to the grinding efficiency Z'.

[0050] The contact dynamic stiffness table storage unit 103 stores contact dynamic stiffness data Ci, Ki between the workpiece W and the grinding wheel T. In particular, the correspondence storage unit 103 constitutes a correspondence storage unit that stores the correspondence between the machining state index (described later) and the contact dynamic stiffness data Ci, Ki. The workpiece support dynamic stiffness table storage unit 104 stores workpiece support dynamic stiffness data Cw, Kw for the spindle unit 30 and tailstock unit 40 as workpiece support devices. In particular, the workpiece support dynamic stiffness table storage unit 104 stores the correspondence between the machining conditions and the workpiece support dynamic stiffness data Cw, Kw. The tool support dynamic stiffness table storage unit 105 stores tool support dynamic stiffness data Ct, Kt for the wheel head body 51 as a grinding wheel support device. In particular, the tool support dynamic stiffness table storage unit 105 stores the correspondence between the machining conditions and the tool support dynamic stiffness data Ct, Kt.

[0051] 4. Obtaining processing conditions 2, the machining condition acquisition unit 106 acquires the machining conditions when grinding is performed by the grinding machine 2. In detail, the machining condition acquisition unit 106 acquires the machining conditions at the time of estimation (time of processing target) by the estimation unit 102. The machining conditions acquired by the machining condition acquisition unit 106 are information used by the dynamic stiffness determination unit 107 to calculate each dynamic stiffness. The acquired machining conditions include, for example, the type of workpiece W, the type of workpiece support member, the type of grinding wheel T, and the pressing forces by the spindle center 34 and the tailstock center 41.

[0052] When the processing estimation device 3b is a simulation device independent of the grinding machine 2, the processing condition acquisition unit 106 acquires conditions for determining dynamic stiffness by inputting the mechanical configuration and grinding program of the grinding machine 2. When the processing estimation device 3b functions as a simulation device that operates in conjunction with the grinding process by the grinding machine 2, the processing condition acquisition unit 106 may acquire conditions for determining dynamic stiffness by inputting the mechanical configuration and grinding program of the grinding machine 2 from the control device 3a, or may acquire information about the conditions directly from the control device 3a of the grinding machine 2.

[0053] 5. Configuration of dynamic stiffness determination unit 107 The dynamic stiffness determination unit 107 determines dynamic stiffness data that affect the grinding process. The dynamic stiffness determination unit 107 separately determines contact dynamic stiffness data Ci, Ki, workpiece support dynamic stiffness data Cw, Kw, and tool support dynamic stiffness data Ct, Kt, as shown in Fig. 5. That is, the dynamic stiffness determination unit 107 includes a contact dynamic stiffness determination unit 121, a workpiece support dynamic stiffness determination unit 122, and a tool support dynamic stiffness determination unit 123.

[0054] The contact dynamic stiffness (Ci, Ki), workpiece support dynamic stiffness (Cw, Kw), and tool support dynamic stiffness (Ct, Kt) will be described with reference to Fig. 5. The contact dynamic stiffness (Ci, Ki) is the dynamic stiffness between the workpiece W and the grinding wheel T. The workpiece support dynamic stiffness (Cw, Kw) includes the workpiece W and is the dynamic stiffness on the workpiece W side relative to the table 20, spindle unit 30, and tailstock unit 40. The tool support dynamic stiffness (Ct, Kt) includes the grinding wheel T and is the dynamic stiffness relative to the wheel head 50. Each of these will be described in detail below.

[0055] 5-1. Contact dynamic stiffness and machining condition index Dynamic contact stiffness is the dynamic stiffness between the workpiece W and the grinding wheel T, and is the dynamic stiffness exerted by 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. Note that static contact stiffness data, which is distinguished from dynamic contact stiffness, is expressed 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 that represents the relationship between the relative speed between the workpiece W and the grinding wheel T and the external force that the workpiece W or the grinding wheel T receives. The spring constant Ki is a value that represents the relationship between the relative position between the workpiece W and the grinding wheel T and the external force that the workpiece W or the grinding wheel T receives.

[0056] The contact dynamic stiffness corresponds to a processing state index that changes depending on the state of processing of the workpiece W by the tool (grinding wheel T) during grinding in the processing device 2. Examples of the processing state index include processing efficiency (grinding efficiency Z'), contact arc length L, and g / a (abrasive grain cutting depth / abrasive grain cutting edge spacing). The correspondence relationship between the processing state index and the contact dynamic stiffness data Ci and Ki can be obtained by actual measurement. As shown in Figure 3, the contact arc length L is the length of the arc of the outer surface of the grinding wheel T that is in contact with the workpiece W during grinding in a cross section perpendicular to the axis of the grinding wheel T. The contact arc length L changes depending on the feed rate 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.

[0057] Examples of the correspondence between the machining condition index and the contact dynamic stiffness data Ci and Ki are shown in Figures 6(a) and 6(b) and Figures 7(a) and 7(b). In the examples shown in Figures 6(a) and 6(b), the grinding efficiency Z' is used as the machining condition index, and the damping coefficient Ci and spring constant Ki of the contact dynamic stiffness have a nonlinear relationship with the grinding efficiency Z', rather than a linear (proportional) relationship. More specifically, the correspondence between the machining condition index and the contact dynamic stiffness data (Ci, Ki) is such that the degree of change in the contact dynamic stiffness data (Ci, Ki) varies with the machining condition index. For example, a function representing a curve with a continuously changing slope can be defined as an approximate equation in a quadratic plane with the machining condition index on the horizontal axis and the contact dynamic stiffness data (Ci or Ki) on the vertical axis. The approximate equation can be a higher-order function; for example, the curves shown in Figures 6(a) and 6(b) are defined as cubic functions.

[0058] In the examples shown in Figures 7(a) and (b), the contact arc length L is used as the machining condition index. In this case, the machining condition index shows a tendency similar to that when the grinding efficiency Z' is used, but it tends to be more difficult to fit the curve expressed by a cubic function than when the grinding efficiency Z' is used. On the other hand, when the grinding efficiency is used as the machining condition index, as shown in Figures 6(a) and (b), it is preferable to use the grinding efficiency Z' as the machining condition index, because it is easier to fit the curve expressed by a cubic function and it is easier to create an approximate equation. Even when the machining condition index is g / a, the correspondence relationship between the machining condition index and the contact dynamic stiffness data Ci and Ki shows a tendency similar to that in the case of the grinding efficiency Z' shown in Figures 6(a) and (b). The correspondence relationship may be expressed by connecting multiple straight lines on the quadratic plane instead of the curve. Furthermore, instead of being defined as a function such as an approximate equation, the correspondence relationship may be in the form of a data table containing correspondence relationships between multiple data.

[0059] The machining state index is acquired by a machining state index acquisition unit 124 provided in the contact dynamic stiffness determination unit 121, and the correspondence between the machining state index and the contact dynamic stiffness data (Ci, Ki) is stored in the correspondence storage unit 103. Then, based on the machining state index acquired by the machining state index acquisition unit 124, the contact dynamic stiffness data (Ci, Ki) is determined by the contact dynamic stiffness determination unit 121.

[0060] 5-2. Contact dynamic stiffness acquisition process for creating correspondence relationships The process of acquiring the contact dynamic stiffness for creating the above-mentioned correspondence will be described with reference to Figs. 8 to 10. As shown in Fig. 8, the process of acquiring contact dynamic stiffness begins with attaching the measuring jig 4 to the grinding machine 2 and the workpiece W (S1). The measuring jig 4 is a non-contact vibrator that applies a vibrating force to the workpiece W. As shown in Fig. 9, the measuring jig 4 is provided on the upper surface of the table 20. The fixing position of the measuring jig 4 in the Z-axis direction on the upper surface of the table 20 can be adjusted.

[0061] The measuring jig 4 holds the workpiece W with the workpiece W inserted therethrough. In detail, a part of the shank Wa, which is the non-machined portion of the workpiece W, is inserted into the measuring jig 4, and a plurality of machined portions Wb to be ground are located outside the measuring jig 4. The workpiece W inserted and held in the measuring jig 4 is supported by the spindle device 30 and tailstock device 40, in the same manner as during normal grinding.

[0062] Here, the configuration of the measuring jig 4 will be described with reference to Figures 10(a) to 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. Furthermore, the housing 131 is formed with a hole 131a that penetrates in the Z-axis direction.

[0063] The electromagnet 132 is embedded in the housing 131. The rotor 133 is attached to the outer circumferential surface of the workpiece W and is provided integrally with the workpiece W. The rotor 133 is made of a magnetic material and moves by the magnetic force generated by the electromagnet 132. The rotor 133 is formed in a cylindrical shape, and the outer circumferential surface of the rotor 133 is disposed with a predetermined gap relative to the inner circumferential surface of the housing 131. This gap determines the distance the rotor 133 can move relative to the housing 131. The inner circumferential surface of the rotor 133 is formed according to the shape of the outer circumferential surface of the workpiece W. The lock nut 134 is a member for fixing the rotor 133 to the workpiece W. The method of fixing the rotor 133 is not limited to a method using the lock nut 134, and various means can be used.

[0064] Displacement sensor 135 is provided at a position close to the inner circumferential surface of housing 131, and measures the distance from the outer circumferential surface of rotor 133. In other words, when rotor 133 is vibrated by electromagnet 132, displacement sensor 135 measures the displacement of rotor 133 in the direction in which rotor 133 approaches or moves away from the inner circumferential surface of housing 131 (hereinafter referred to as radial displacement).

[0065] 10(c), the control device 136 supplies a driving current to the electromagnet 132 so that the electromagnet 132 applies an excitation force. The control device 136 also acquires the displacement measured by the displacement sensor 135, i.e., the radial displacement of the rotor 133.

[0066] 8, the shaft portion Wa, which is the non-machined portion of the workpiece W, is inserted into the rotor 133 of the measuring jig 4 as shown in Fig. 10(a). Then, the rotor 133 is fixed to the workpiece W with a lock nut 134 as shown in Fig. 10(b).

[0067] Then, the housing 131 of the measuring jig 4 is attached to the table 20. Furthermore, the workpiece W to which the rotor 133 is attached is supported by the spindle unit 30 and the tailstock unit 40. At this time, the position of the housing 131 is adjusted so that the outer peripheral surface of the rotor 133 faces the inner peripheral surface of the housing 131 of the measuring jig 4, as shown in FIG. 10(b).

[0068] Next, grinding is started (S2). That is, while the workpiece W and the grinding wheel T are rotating, the grinding wheel T is moved in the X-axis direction to grind the outer peripheral surface of the processing portion Wb of the workpiece W.

[0069] Next, an excitation force is applied by the measuring jig 4 (S3). The application of the excitation force by the measuring jig 4 is performed while the workpiece W is being ground by the grinding wheel T. The applied excitation force may be impulse excitation or sweep excitation in which the excitation frequency is continuously changed. The application of the excitation force is performed by the control device 136 of the measuring jig 4 supplying a current to the electromagnet 132. The excitation force is controlled by the current supplied to the electromagnet 132 by the control device 136.

[0070] Next, when an excitation force is applied during grinding, the radial displacement of the rotor 133 is measured by the displacement sensor 135 of the measuring jig 4 (S4). Here, the displacement of the rotor 133 coincides with the radial displacement of the portion of the workpiece W that is fixed to the rotor 133. Therefore, the displacement sensor 135 of the measuring jig 4 measures the radial displacement that occurs in the workpiece W when an excitation force is applied to the workpiece W.

[0071] Next, when the measurement by the displacement sensor 135 is completed, the grinding process is ended (S5).

[0072] Next, the overall dynamic stiffness data Ccom, Kcom during grinding is calculated (S6). The overall dynamic stiffness data Ccom, Kcom is overall (composite) dynamic stiffness data represented by the above-mentioned contact dynamic stiffness data Ci, Ki, workpiece support dynamic stiffness data Cw, Kw, and tool support dynamic stiffness data Ct, Kt. The overall dynamic stiffness data Ccom, Kcom is represented as the sum of the above-mentioned contact dynamic stiffness data Ci, Ki, workpiece support dynamic stiffness data Cw, Kw, and tool support dynamic stiffness data Ct, Kt.

[0073] As described above, the radial displacement measured by the displacement sensor 135 of the measuring jig 4 is measured when an excitation force is applied to the workpiece W during grinding. Therefore, the measured displacement is affected by the contact dynamic stiffness data Ci, Ki, workpiece support dynamic stiffness data Cw, Kw, and tool support dynamic stiffness data Ct, Kt. Therefore, the calculation of the overall dynamic stiffness data Ccom, Kcom is data generated from the relationship between the excitation force and the radial displacement of the workpiece W when an excitation force is applied to the workpiece W during grinding.

[0074] Next, workpiece support dynamic stiffness data Cw, Kw and tool support dynamic stiffness data Ct, Kt are acquired (S7). The workpiece support dynamic stiffness data Cw, Kw and tool support dynamic stiffness data Ct, Kt are acquired in advance by a hammering test or the like.

[0075] Next, the contact dynamic stiffness data Ci, Ki are calculated (S8). The contact dynamic stiffness data Ci, Ki are obtained by subtracting the workpiece support dynamic stiffness data Cw, Kw and the tool support dynamic stiffness data Ct, Kt from the overall dynamic stiffness data Ccom, Kcom.

[0076] Next, an interpolation process is performed on the contact dynamic stiffness data Ci and Ki (S9). The interpolation process is a process in which the contact dynamic stiffness data Ci and Ki obtained by actual measurement are used to obtain contact dynamic stiffness data Ci and Ki under grinding conditions different from those obtained by actual measurement. For example, an empirical formula that defines the relationship between the contact arc length L, the damping coefficient Ci, and the spring constant Ki can be used. The interpolation process can also apply empirical formulas, machine learning, theoretical calculations, etc. The obtained contact dynamic stiffness data Ci and Ki can be used to create a correspondence relationship with the machining condition index (grinding efficiency) shown in Figures 6(a) and 6(b).

[0077] 5-3. Correction of contact dynamic stiffness data The contact dynamic stiffness data (Ci, Ki) determined by the contact dynamic stiffness determination unit 121 is corrected based on the contact stiffness deflection Xi and the contribution rate p by the contact dynamic stiffness correction unit 127 shown in Fig. 2. The correction of the contact dynamic stiffness data (Ci, Ki) will be described in detail below.

[0078] The contact stiffness deflection acquisition unit 125 shown in FIG. 2 acquires the contact stiffness deflection Xi used to correct the contact dynamic stiffness data (Ci, Ki). The contact stiffness deflection Xi is the deflection of the contact stiffness between the tool T and the workpiece W, and is generated when the grinding wheel as the tool T comes into contact with the workpiece W, due to the elastic deformation of the bond that holds the abrasive grains on the grinding wheel, causing the abrasive grains to be displaced. Here, the total cutting amount ut when machining the workpiece W with the tool T is detected as the sum of the workpiece deflection X1, which is the deflection of the workpiece W during machining, the tool deflection X2, which is the deflection of the tool T, the workpiece removal amount Δr, which is the amount removed from the workpiece W by the tool T, and the contact stiffness deflection Xi. Therefore, the contact stiffness deflection Xi can be acquired by calculating it based on the following equation (1):

[0079]

number

[0080] 2 acquires the contribution rate p used to correct the contact dynamic stiffness data (Ci, Ki). The contribution rate p indicates the degree to which the contact stiffness deflection Xi contributes to the contact dynamic stiffness data (Ci, Ki). The degree to which the contact stiffness deflection Xi contributes to the contact dynamic stiffness data (Ci, Ki) changes based on changes in the interference state between the tool T and the workpiece W depending on the machining state.

[0081] For example, as shown in the conceptual diagram of FIG. 11(a), a grinding wheel serving as a tool T has a damping coefficient Cag and a spring constant Kag for each abrasive grain A G. During rough machining, the grinding efficiency Z' is high, so the interference area deforms into a roughly triangular shape, as shown in the conceptual diagram of FIG. 11(b), and the displacement of the abrasive grain A G is biased within the interference area. Therefore, the degree to which the contact stiffness deflection Xi contributes to the contact dynamic stiffness data (Ci, Ki) decreases; for example, the contribution rate p becomes approximately 1 / 2. On the other hand, during finish machining, the grinding efficiency Z' is low, so the outer peripheral surface of the workpiece W in the interference area becomes nearly arc-shaped, as shown in the conceptual diagram of FIG. 11(c), and the displacement of the abrasive grain A G is less biased within the interference area. Therefore, the degree to which the contact stiffness deflection Xi contributes to the contact dynamic stiffness data (Ci, Ki) increases; for example, the contribution rate p approaches 1. That is, the contribution rate p can be made different between rough machining and finish machining, and the contribution rate p in rough machining can be set lower than the contribution rate in finish machining.

[0082] In the first embodiment, the contribution rate p is acquired in the contribution rate acquisition unit 126 as follows. As shown in Fig. 12, of the multiple sections obtained by dividing the machining position of the workpiece W at equal intervals in the circumferential direction, the length ln (n = 1, 2, 3, 4, 5, 6, 7, 8, 9, etc.) of the line segment in the radial direction of the workpiece W at the portion where the grinding wheel T and the workpiece W interfere with each other is acquired. Then, based on the maximum length lmax of the line segment and the average length lmean of the line segment, the contribution rate p is set as contribution rate p = average value lmean / maximum value lmax. Note that the average value lmean may be the arithmetic average of ln of each section, or a weighted average in which weighting is performed based on the removal area of each section.

[0083] The contribution rate p acquired as described above by the contribution rate acquisition unit 126 is set to be different for rough machining and finish machining. Furthermore, if the finish machining includes a precision grinding process, a fine grinding process, and a spark-out process, and is performed in the order of decreasing grinding efficiency Z', the contribution rates p for the precision grinding process, the fine grinding process, and the spark-out process are set to be increasing in this order.

[0084] Alternatively, the contribution rate p can be set according to the cutting depth per unit time in machining the workpiece W, according to the feed rate of the tool T in machining the workpiece W, or according to the machining condition index of the workpiece W by the tool T. When setting according to the machining condition index, for example, the machining efficiency (grinding efficiency Z'), contact arc length L, g / a (grain cutting depth / grain cutting edge spacing), etc. can be used as the machining condition index.

[0085] As described above, the contact dynamic stiffness data (Ci, Ki) determined by the contact dynamic stiffness determiner 121 based on the machining index acquired by the machining state index acquirer 124 and the correspondence stored in the correspondence storage unit 103 is corrected by the contact dynamic stiffness corrector 127 based on the contact stiffness deflection Xi acquired by the contact stiffness deflection acquirer 125 and the contribution rate p acquired by the contribution rate acquirer 126, and the corrected contact dynamic stiffness data can be expressed as (p*Ci*Xi, p*Ki*Xi). Therefore, the contact dynamic stiffness calculation system 130 that calculates the corrected contact dynamic stiffness data is made up of the machining state index acquirer 124, the correspondence storage unit 103, the contact dynamic stiffness determiner 121, the contact stiffness deflection acquirer 125, the contribution rate acquirer 126, and the contact dynamic stiffness corrector 127.

[0086] 5-4. Workpiece support dynamic stiffness The workpiece support dynamic stiffness is the dynamic stiffness related to support in the spindle unit 30 and tailstock unit 40 shown in FIG. 1, and is the dynamic stiffness exhibited when the workpiece W is supported by the spindle unit 30 and tailstock unit 40 as workpiece support devices that make up the grinding machine 2. As shown in FIG. 5, the workpiece support dynamic stiffness is defined by the damping coefficient Cw and spring constant Kw. The damping coefficient Cw is a value that represents the relationship between the relative speed of the workpiece W with respect to the reference positions of the spindle unit 30 and tailstock unit 40 and the external force that the workpiece W receives. The spring constant Kw is a value that represents the relationship between the relative position of the workpiece W with respect to the reference positions of the spindle unit 30 and tailstock unit 40 and the external force that the workpiece W receives.

[0087] As described above, the workpiece support dynamic stiffness data Cw, Kw are stored in the workpiece support dynamic stiffness table storage unit 104 so as to correspond to the above-mentioned machining conditions. For example, in a case where the tailstock center 41 is capable of controlling the pressing force against the workpiece W in the axial direction of the workpiece W, the workpiece support dynamic stiffness data Cw, Kw are data that change in accordance with changes in the contact state between the tailstock center 41 and the workpiece W due to changes in the pressing force by the tailstock center 41. The workpiece support dynamic stiffness data Cw, Kw can be obtained, for example, by conducting a hammering test while changing the pressing force by the tailstock center 41 in a state where the workpiece W is supported by the spindle center 34 and the tailstock center 41.

[0088] Then, the workpiece support dynamic stiffness determination unit 122 determines the workpiece support dynamic stiffness data Cw, Kw corresponding to the machining conditions acquired by the machining condition acquisition unit 106 from the workpiece support dynamic stiffness table stored in the workpiece support dynamic stiffness table storage unit 104.

[0089] 5-5. Tool support dynamic rigidity The tool support dynamic stiffness is the dynamic stiffness related to support in the wheel head body 51 shown in FIG. 1, and is the dynamic stiffness exhibited when the grinding wheel T is supported by the wheel head body 51, which serves as a grinding wheel support device constituting the grinding machine 2. As shown in FIG. 5, the tool support dynamic stiffness is defined by a damping coefficient Ct and a spring constant Kt. The damping coefficient Ct is a value that represents the relationship between the relative speed of the grinding wheel T with respect to a reference position on the wheel head body 51 and the external force that the grinding wheel T receives. The spring constant Kt is a value that represents the relationship between the relative position of the grinding wheel T with respect to the reference position on the wheel head body 51 and the external force that the grinding wheel T receives.

[0090] As described above, the tool support dynamic stiffness data Ct, Kt are stored in the tool support dynamic stiffness table storage unit 105 so as to correspond to the above-mentioned machining conditions. The tool support dynamic stiffness table storage unit 105 stores the tool support dynamic stiffness data Ct, Kt, for example, for each type of grinding wheel T. Furthermore, in a configuration in which the grinding wheel T is supported by a hydrostatic bearing, if the pressure of the hydrostatic bearing is controllable and the tool support dynamic stiffness data Ct, Kt changes depending on the machining conditions, the tool support dynamic stiffness table storage unit 105 may be configured to store the correspondence between the machining conditions and the tool support dynamic stiffness data Ct, Kt.

[0091] Then, the tool support dynamic stiffness determination unit 123 determines the tool support dynamic stiffness data Ct, Kt corresponding to the machining conditions acquired by the machining condition acquisition unit 106 from the tool support dynamic stiffness table stored in the tool support dynamic stiffness table storage unit 105.

[0092] 6. Correction amount calculation unit 108 The correction amount calculation unit 108 calculates the correction amount for the relative displacement of the grinding wheel T and workpiece W in the X-axis direction due to grinding resistance, based on each dynamic stiffness data determined by the dynamic stiffness determination unit 107. The correction amount for displacement can be found from each dynamic stiffness data and the grinding resistance. That is, the correction amount for displacement can be calculated from the grinding resistance Fn, contact dynamic stiffness data Ci, Ki, workpiece support dynamic stiffness data Cw, Kw, tool support dynamic stiffness data Ct, Kt, contribution rate p, and contact stiffness deflection Xi. That is, the correction amount for displacement can be found based on the equation of motion using the workpiece mass Mw and the tool mass Mt so as to satisfy the following equations (2) and (3).

[0093]

number

[0094] 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 target based on the relative position between 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 acquired by the command value acquisition unit 101. However, due to grinding resistance, the relative position between the workpiece W and the grinding wheel T will be different from the relative position determined by the command value.

[0095] Therefore, when estimating the estimation target, the estimation unit 102 uses, as the relative position between the workpiece W and the grinding wheel T, the relative position obtained by adding the correction amount calculated by the correction amount calculation unit 108 to the relative position acquired by the command value acquisition unit 101. In other words, the estimation unit 102 estimates the estimation target based on the relative position according to the command value and the correction amount calculated using each dynamic stiffness data.

[0096] In particular, 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 amount of interference between the workpiece W and the grinding wheel T based on the relative position between 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 acquired by the command value acquisition unit 101. However, due to grinding resistance, the relative position between the workpiece W and the grinding wheel T will be different from the relative position determined by the command value.

[0097] Therefore, the interference amount calculation unit 111 uses the relative position between the workpiece W and the grinding wheel T used to calculate the amount of interference, which is the sum of the relative position acquired by the command value acquisition unit 101 and the correction amount calculated by the correction amount calculation unit 108. In other words, the interference amount calculation unit 111 calculates the amount of interference based on the relative position determined by the command value and the correction amount calculated using each dynamic stiffness data.

[0098] The interference amount calculation unit 111 calculates the amount of interference taking the amount of correction into consideration, and the grinding efficiency calculation unit 112, grinding characteristic determination unit 113, and grinding resistance calculation unit 114 obtain the grinding efficiency Z', grinding characteristic kc, and grinding resistance Fn based on the amount of interference taking the amount of correction into consideration.

[0099] The output unit 109 outputs the estimation target 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 processing system 1 (corresponding to the mechanical state of the grinding machine 2). The output unit 109 may be configured to teach the estimation result to a teaching device (not shown), for example.

[0100] The machining condition optimization unit 110 optimizes the machining conditions based on the estimation results by the estimation unit 102. Then, the machining condition optimization unit 110 can output the optimized machining conditions to the control device 3a of the grinding machine 2. In this case, the control device 3a can perform grinding using the optimized machining conditions. In addition, the control device 3a can also control machining using various dynamic stiffness data determined by the dynamic stiffness determination unit 107, regardless of the estimation results.

[0101] 7. Action and Effects According to the contact dynamic stiffness calculation system 130 of the first embodiment, the contact dynamic stiffness data (Ci, Ki) determined based on the pre-stored correspondence between the machining state index and the contact dynamic stiffness data and the acquired machining state index is corrected based on the contact stiffness deflection Xi between the tool T and the workpiece W and the contribution rate p indicating the degree to which the contact stiffness deflection Xi contributes to the contact dynamic stiffness data (Ci, Ki). Therefore, the corrected contact dynamic stiffness data (p*Ci*Xi, p*Ki*Xi) fully takes into account changes in the contact dynamic stiffness deflection Xi, thereby improving the calculation accuracy of the contact dynamic stiffness.

[0102] Furthermore, in the first embodiment, the machining of the workpiece W includes at least rough machining and finish machining, and the contribution rate p in the rough machining is different from the contribution rate p in the finish machining. This allows for more accurate consideration of changes in the contact dynamic stiffness deflection Xi according to the machining state, thereby further improving the calculation accuracy of the contact dynamic stiffness.

[0103] Furthermore, in this embodiment 1, the contribution rate p in rough machining is lower than the contribution rate p in finish machining, except at the start of rough machining. As a result, the contact dynamic stiffness deflection Xi that occurs in rough machining with a high grinding efficiency Z' and finish machining with a low grinding efficiency Z' is taken into account more accurately in the period excluding the start of rough machining, and therefore the calculation accuracy of the contact dynamic stiffness can be further improved.

[0104] Furthermore, the contribution rate p can be set according to the cutting depth per unit time in machining the workpiece W. Furthermore, the contribution rate p can be set according to the feed rate of the tool T in machining the workpiece W. Furthermore, the contribution rate p can be set according to the machining state index of the workpiece by the tool. In either case, the change in the contact dynamic stiffness deflection Xi according to the machining state is taken into account more accurately, thereby further improving the calculation accuracy of the contact dynamic stiffness.

[0105] Furthermore, in the first embodiment, the machining state index can include any of the machining efficiency (grinding efficiency Z') of the tool T on the workpiece W, the contact arc length L between the tool T and the workpiece W, the abrasive grain cutting depth / abrasive grain cutting edge spacing (g / a) of the tool T, and the cutting depth of the tool T. This allows for more accurate consideration of changes in the contact dynamic stiffness deflection Xi according to the machining state, thereby further improving the calculation accuracy of the contact dynamic stiffness.

[0106] Furthermore, in this embodiment 1, the machining efficiency (grinding efficiency Z') of the workpiece W by the tool T is adopted as the machining state index. Since the machining efficiency is closely related to the machining state of the workpiece W, by using the machining efficiency as the machining state index, it is possible to calculate the contact dynamic stiffness data with high accuracy according to the machining state of the workpiece W.

[0107] Furthermore, in this embodiment 1, the processing device 2 is a cylindrical grinding machine that grinds the cylindrical outer peripheral surface of the workpiece W with a grinding wheel, which is the tool T, and the contribution rate acquisition unit 126 acquires the lengths ln of line segments in the radial direction of the workpiece W in the interference area between the grinding wheel T and the workpiece W in multiple sections obtained by dividing the processing position of the workpiece W at equal intervals in the circumferential direction, and sets the contribution rate p based on the maximum value lmax of the line segment lengths ln and the average value lmean of the line segment lengths ln in the multiple sections. As a result, the contribution rate p can more accurately indicate the degree to which the contact stiffness deflection Xi contributes to the contact dynamic stiffness data (Ci, Ki), thereby further improving the calculation accuracy of the contact dynamic stiffness.

[0108] Furthermore, the machining estimation device 3b in this embodiment 1 includes a contact dynamic stiffness calculation system 130, a workpiece support dynamic stiffness determination unit 122 that determines workpiece support dynamic stiffness data (Cw, Kw) of the workpiece support devices 30, 40 that are exerted when the workpiece W is supported by the workpiece support devices 30, 40 that constitute the machining device 2, a tool support dynamic stiffness determination unit 123 that determines tool support dynamic stiffness data (Ct, Kt) of the tool support device 51 that is exerted when the tool T is supported by the tool support device 51 that constitutes the machining device 2, a correction amount calculation unit 108 that calculates a correction amount for the relative position between the tool T and the workpiece W based on the corrected contact dynamic stiffness data (p*Ci*Xi, p*Ki*Xi), the tool support dynamic stiffness data (Ct, Kt) and the workpiece support dynamic stiffness data (Cw, Kw), and an estimation unit 102 that estimates the machining result of the workpiece W by the tool T based on the command value and the correction amount for machining the workpiece W. As a result, the machining estimation device 3b uses corrected contact dynamic stiffness data calculated with high accuracy based on the contact dynamic stiffness calculation system 130, and therefore can estimate the machining result with high accuracy.

[0109] Moreover, in the machining system 1 of the present embodiment 1, the machining estimation device 3b further includes a machining condition optimization unit 110 that optimizes the machining conditions of 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 with the tool T based on the optimized machining conditions. This allows the workpiece W to be machined under machining conditions optimized based on the machining result estimated with high accuracy, making it possible to stably produce high-accuracy workpieces W and reduce manufacturing costs.

[0110] Furthermore, in the contact dynamic stiffness calculation system 130 of the first embodiment, the correspondence between the machining state index and the contact dynamic stiffness data (Ci, Ki) stored in the correspondence storage unit 103 is defined as an approximation of a function that represents a curve with a continuously changing slope on a quadratic plane with the machining state index on the horizontal axis and the contact dynamic stiffness on the vertical axis. In this way, by defining the correspondence as an approximation of a function that represents a curve that is a nonlinear relationship, it is possible to calculate the contact dynamic stiffness data with higher accuracy than when a conventional linear relationship is used.

[0111] As described above, according to the above-described aspect, it is possible to provide the contact dynamic stiffness calculation system 130, the processing estimation device 3b, and the processing system 1 that are capable of calculating contact dynamic stiffness with higher accuracy.

[0112] As an alternative to the first embodiment, in a modified embodiment shown in Fig. 13, the processing apparatus 2 is provided with a rest device 70. As shown in Fig. 14, the rest device 70 is provided with a first arm 71 and a second arm 72, and is configured so that both arms 71, 72 slide and support a lower part W1 of the workpiece W and a part W2 opposite to the tool T at the same position in the spindle direction as the grinding wheel T. The rest device 70 prevents the workpiece W from being displaced away from the grinding wheel T during processing.

[0113] This modified embodiment can also achieve the same effects as those of the embodiment 1. When the rest device 70 is provided, the workpiece W may be supported by either cantilever support or double-support support.

[0114] In the above embodiment, cutting processing using grinding with a grinding machine 2 as a processing device has been described as an example, but the present invention is also applicable to cutting processing using a lathe or machining center. In the case of cutting processing, cutting efficiency, cutting depth, etc. can be used as the processing condition index. [Explanation of symbols]

[0115] 1 Processing System 2 Grinding machine (processing equipment) 3a Control device 3b Processing estimation device 30 Spindle device (workpiece support device) 32 Workpiece spindle 33 Work spindle motor (drive unit) 40 Tailstock device (workpiece support device) 51 Grinding wheel head body (tool support device) 52 Grindstone spindle (tool spindle) 53 Grinding wheel motor (drive unit) 70 Rest Device 102 Estimation part 103 Contact dynamic stiffness table storage unit (correspondence storage unit) 104 Workpiece support dynamic stiffness table memory unit 105 Tool support dynamic stiffness table memory unit 106 Machining condition acquisition section 107 Dynamic stiffness determination unit 108 Correction amount calculation section 109 Output section 110 Processing Condition Optimization Department 121 Contact dynamic stiffness determination section 122 Workpiece support dynamic stiffness determination section 123 Tool support dynamic stiffness determination section 124 Processing condition index acquisition unit 125 Contact stiffness deflection acquisition unit 126 Contribution Rate Acquisition Unit 127 Contact dynamic stiffness correction section 130 Contact Dynamic Stiffness Calculation System

Claims

1. 1. A contact dynamic stiffness calculation system for calculating contact dynamic stiffness data between a workpiece and a tool exerted by contact between the workpiece and the tool during machining in a machining device that machines a workpiece with a tool, a correspondence relationship storage unit that stores a correspondence relationship between a machining state index that changes depending on a state of machining of the workpiece by the tool and contact dynamic stiffness data; a machining state index acquisition unit that acquires the machining state index; a contact dynamic stiffness determining unit that determines the contact dynamic stiffness data based on the acquired machining state index and the correspondence relationship; a contact stiffness deflection acquiring unit that acquires contact stiffness deflection between the tool and the workpiece based on workpiece deflection, which is deflection of the workpiece during machining, tool deflection, which is deflection of the tool, a total cutting amount of the tool into the workpiece, and an amount of workpiece removed by the tool; a contribution rate acquisition unit that acquires a contribution rate indicating a degree to which the contact stiffness deflection contributes to the contact dynamic stiffness data; a contact dynamic stiffness correction unit that corrects the contact dynamic stiffness data determined by the contact dynamic stiffness determination unit based on the contact stiffness deflection and the contribution rate.

2. The machining of the workpiece includes at least rough machining and finish machining, The contact dynamic stiffness calculation system according to claim 1 , wherein the contribution rate in the rough machining and the contribution rate in the finish machining are different from each other.

3. 2. The contact dynamic stiffness calculation system according to claim 1, wherein the contribution rate is set in accordance with a cutting amount per unit time in machining the workpiece.

4. The contact dynamic stiffness calculation system according to claim 1 , wherein the contribution rate is set in accordance with a feed rate of the tool when machining the workpiece.

5. The contact dynamic stiffness calculation system according to claim 1 , wherein the contribution rate is set in accordance with a machining state index of the workpiece by the tool.

6. 6. The contact dynamic stiffness calculation system according to claim 5, wherein the machining state index includes any one of a machining efficiency of the workpiece by the tool, a contact arc length between the tool and the workpiece, an abrasive grain cutting depth / abrasive grain cutting edge interval of the tool, and a cutting depth of the tool.

7. the processing device is a cylindrical grinding machine that grinds the cylindrical outer peripheral surface of the workpiece with a grinding wheel that is the tool, 2. The contact dynamic stiffness calculation system according to claim 1, wherein the contribution rate acquisition unit acquires lengths of line segments in the radial direction of the workpiece in an interference area between the grinding wheel and the workpiece in a plurality of sections obtained by dividing the machining position of the workpiece at equal intervals in the circumferential direction, and sets the contribution rate based on a maximum value of the lengths of the line segments and an average value of the lengths of the line segments in the plurality of sections.

8. The contact dynamic stiffness calculation system according to claim 1 ; a work support dynamic stiffness determination unit that determines work support dynamic stiffness data of a work support device that is exhibited when the work support device of the processing apparatus supports the work; a tool support dynamic stiffness determination unit that determines tool support dynamic stiffness data of a tool support device that is exhibited when the tool is supported by a tool support device that configures the processing apparatus; a correction amount calculation unit that calculates a correction amount for the relative position between the tool and the workpiece based on the corrected contact dynamic stiffness data, the workpiece support dynamic stiffness data, and the tool support dynamic stiffness data; an estimation unit that estimates a result of machining the workpiece by the tool based on a command value for machining the workpiece and the correction amount.

9. 9. The machining estimation device according to claim 8, further comprising: a machining condition optimization unit that optimizes machining conditions for the workpiece based on the machining result estimated by the estimation unit; and the machining device that machines the workpiece using the tool based on the optimized machining conditions.

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