Contact dynamic stiffness calculation system and machining system

Abstract

To provide a contact dynamic stiffness calculation system that is capable of calculating contact dynamic stiffness with high accuracy by taking into account contact states between a workpiece and workpiece support members.SOLUTION: A contact dynamic stiffness calculation system 130 acquires basic information related to a workpiece W containing information of a processing position I on the workpiece W supported by workpiece support members 34, 41. Further, the contact dynamic stiffness calculation system 130 calculates a difference bending angle that is a difference between a workpiece bending angle and a support member bending angle at a contact part of the workpiece W and the workpiece support members 34, 41, at the time an initial state in which acting force is not applied by an abrasive wheel T to the workpiece W supported by the workpiece support members 34, 41, changes to an acting state in which the acting force is applied. In addition, a spring constant and an attenuation coefficient at the contact part of the workpiece W and the workpiece support members 34, 41 are calculated on the basis of, the basic information and the difference bending angle, in order to calculate contact dynamic stiffness.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] Various configurations have been proposed for estimating the results of machining a workpiece using a tool such as a grinding wheel. For example, Patent Document 1 describes a method for estimating the depth of grinding marks on a workpiece by taking into account the static contact stiffness between the workpiece and the grinding wheel when grinding the workpiece with a grinding wheel. The static contact stiffness used here is calculated using theoretical static contact stiffness during grinding, rather than a value measured when the grinding wheel is stationary. The static contact stiffness is expressed by the spring constant K between the workpiece and the grinding wheel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-208812 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration disclosed in Patent Document 1, the grinding mark depth on the workpiece is estimated taking into account the support stiffness of the workpiece support member that supports the grinding wheel and the workpiece. The support stiffness varies not only depending on the stiffness of the support member that supports the workpiece, but also on the contact state between the workpiece and the workpiece support member. However, because the configuration disclosed in Patent Document 1 does not take into account the change in the contact state, errors occur in the calculation result of the dynamic stiffness on the workpiece side, reducing the estimation accuracy. Therefore, in order to accurately estimate the machining results of the workpiece, it is necessary to accurately calculate the dynamic stiffness of the machining point on the workpiece, taking into account the contact state between the workpiece and the workpiece support member.

[0005] The present invention has been made in view of the above-mentioned problems, and aims to provide a contact dynamic stiffness calculation system that can calculate contact dynamic stiffness with high accuracy, taking into account the contact state between a workpiece and a workpiece support member. [Means for solving the problem]

[0006] One aspect of the present invention is a contact dynamic stiffness calculation system that calculates contact dynamic stiffness at a contact portion between a workpiece and a workpiece support member when the workpiece supported by the workpiece support member is machined by a tool, the system comprising: The workpiece support member comprises a tailstock center, the workpiece has a center hole into which the tailstock center is inserted, the contact portion is a portion where the tailstock center and the center hole come into contact with each other, the contact dynamic stiffness is dynamic stiffness between the workpiece and the tailstock center exerted by contact between the workpiece and the tailstock center, and is defined by a damping coefficient and a spring constant; at least Information on the machining position of the workpiece and the maximum support diameter of the center hole a basic information acquisition unit that acquires basic information about the workpiece, including An initial state in which no force is applied from the tool to the workpiece supported by the workpiece support member. The axis of the workpiece at A force is applied from the tool to the workpiece. The angle between the center hole and the axis of the workpiece at the position where the center hole is located in the working state. Workpiece bending angle and , the angle between the axis of the workpiece in the initial state and the axis of the tailstock center in the operating state. a differential bending angle calculation unit that calculates a differential bending angle that is a difference between the bending angle of the support member; a contact dynamic stiffness calculation unit that calculates a spring constant and a damping coefficient at a contact portion between the workpiece and the workpiece support member based on the basic information acquired by the basic information acquisition unit and the differential bending angle calculated by the differential bending angle calculation unit, and calculates contact dynamic stiffness of the workpiece based on the spring constant and the damping coefficient; The present invention relates to a contact dynamic stiffness calculation system comprising: [Effects of the Invention]

[0007] According to the above aspect, the contact dynamic stiffness calculation unit calculates a spring constant and a damping coefficient at the contact portion between the workpiece and the workpiece support member based on basic information including information on the machining position and the differential bend angle calculated by the differential bend angle calculation unit, and calculates the contact dynamic stiffness, which is the dynamic stiffness at the contact portion, based on the spring constant and the damping coefficient. This allows the contact dynamic stiffness to be calculated taking into account the discrepancy that occurs between the workpiece bend angle, which is the bend angle of the workpiece, and the support member bend angle, which is the bend angle of the workpiece support member. As a result, the contact dynamic stiffness can be calculated with high accuracy, taking into account the contact state between the workpiece and the workpiece support member.

[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 high accuracy, taking into account the contact state between the workpiece and the workpiece support member. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a processing system according to a first embodiment. [Figure 2] FIG. 2 is a functional block diagram of a processing estimation device including a contact dynamic stiffness calculation system according to the first embodiment. [Figure 3] Schematic diagram showing interference between a workpiece and a grinding wheel during grinding. [Figure 4] FIG. 10 is a diagram showing the shape of a workpiece in a grinding simulation using a group of radial line segments, illustrating how the workpiece, represented by the radial line segments, interferes with the outer circumferential line of the grinding wheel during grinding. [Figure 5] FIG. 4 is a diagram showing the correspondence relationship between the processing position and the differential bending angle in the contact dynamic stiffness calculation system according to the first embodiment. [Figure 6] FIG. 1( a ) is a cross-sectional view showing the initial state of a workpiece supported by a workpiece support member, and FIG. 1( b ) is a cross-sectional view showing the state in which a force is applied to the workpiece from a grinding wheel. [Figure 7] 3 is a schematic diagram showing the dynamic stiffness of a workpiece and the dynamic stiffness of a tool during grinding in the first embodiment. FIG. [Figure 8] FIG. 10 is a diagram showing a processing system according to a second embodiment. [Figure 9] FIG. 2 is a functional block diagram of a dynamic stiffness determination unit including a contact dynamic stiffness calculation system according to the first embodiment. [Figure 10] FIG. 10 is a diagram showing a processing system according to a third embodiment. [Figure 11] 11 is a schematic diagram showing the dynamic stiffness of a workpiece and the dynamic stiffness of a tool during cutting in the third embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Embodiment 1) 1. Configuration of Processing System 1 A 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, the workpiece W is, for example, a member formed in a shaft shape, as shown in Fig. 1. However, the shape of the workpiece W is not limited to a shaft shape and can be any shape.

[0013] In this embodiment, the workpiece W is generally rod-shaped and includes supported portions WR and WL located at both ends. However, the workpiece W shown in Fig. 1 is merely an example, and the grinding machine 2 can grind workpieces having various shapes. In this embodiment, one of the supported portions WL is located at one axial end face and forms a center hole into which a spindle center 34, which serves as a workpiece support member described below, is inserted. The center hole that forms the supported portion WL is conical in shape to match the shape of the tip of the spindle center 34.

[0014] The other supported part WR is located on the other axial end face and forms a center hole into which a spindle center 34, which serves as a workpiece support member and will be described later, is inserted. The center hole formed by the supported part WR is conical in shape to match the shape of the tip of the spindle center 34. The position on the workpiece W where the grinding wheel T comes into contact is the machining position I.

[0015] 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 has a contact dynamic stiffness calculation system 130, which will be described later, and performs a process of estimating the processing result of the workpiece W by simulating the grinding process using the workpiece-side dynamic stiffness (Cw, Kw) including the contact dynamic stiffness (Cwc, Kwc) calculated by the contact dynamic stiffness calculation system 130.

[0016] The processing estimation device 3b can function as a simulation device independent of the grinding machine 2 and the control device 3a, or as a simulation device that operates in conjunction with the grinding machine 2 and the control device 3a. In the former case, the processing estimation device 3b can, for example, determine optimal grinding conditions 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.

[0017] 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 by 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 this embodiment, the grinding machine 2 is exemplified by a case in which the grinding wheel T grinds the cylindrical outer peripheral surface of the workpiece W.

[0018] The grinding machine 2 includes a bed 10, a table 20, a spindle unit 30, a tailstock unit 40, and a wheel head 50. The spindle unit 30 and the tailstock unit 40, which are mounted on the table 20, function as workpiece support members that support the workpiece W. The wheel head 50 functions as a tool support member that supports the grinding wheel T. In other words, the grinding machine 2 grinds the workpiece W supported on the workpiece support member with the grinding wheel T supported on the tool support member. The grinding machine 2 may further include a sizing device (not shown) that acquires the outer dimensions of the workpiece W. The components of the grinding machine 2 are described in detail below.

[0019] The bed 10 is placed 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.

[0020] 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.

[0021] 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 embodiment, Z-axis detector 12c is 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 use a linear motor instead of the ball screw mechanism 12a.

[0022] Bed 10 also has a guide surface 13 on its upper surface on the rear side in the X-axis direction, which extends in a direction intersecting the Z-axis direction. In this embodiment, 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, 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.

[0023] 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 rotation 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.

[0024] 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.

[0025] The spindle unit 30 supports the workpiece W and drives it to rotate. The spindle unit 30 is disposed on one end side in the Z-axis direction on the table 20. The spindle unit 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).

[0026] The spindle housing 31 is fixed onto the table 20. The spindle 32 is rotatably supported by the spindle housing 31 via a bearing. The spindle motor 33 drives the spindle 32 to rotate.

[0027] The spindle center 34 (corresponding to the support center) constitutes a workpiece support member that supports the end face of one axial end (the left end in FIG. 1) of the workpiece W. In detail, the spindle center 34 supports the workpiece W while being pressed in the axial direction against a spindle-side center hole (hereinafter also referred to as "center hole WR") that constitutes a supported portion WR formed in the end face of one axial end of the workpiece W.

[0028] The spindle center 34 is fixed to the spindle 32 and is provided rotatably relative to the spindle housing 31. However, if the spindle device 30 is provided with a turning member such as a cage (not shown), the spindle center 34 may be fixed to the spindle housing 31 and provided so as to be non-rotatable relative to the spindle housing 31. Furthermore, the spindle device 30 may be provided with a chuck that grips the workpiece W as a workpiece support member, instead of the spindle center 34. The chuck is connected to the spindle 32 and is driven to rotate.

[0029] 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 rotation angle of the rotation shaft of the spindle motor 33. The spindle drive circuit includes an amplifier circuit and drives the spindle motor 33.

[0030] The tailstock device 40 supports the workpiece W together with the spindle device 30. The tailstock device 40 is disposed on the other end 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 includes a tailstock center 41 and an adjustment mechanism 42. Note that when the grinding machine 2 grinds the inner peripheral surface of the workpiece W, the tailstock device 40 is not necessary.

[0031] The tailstock center 41 (corresponding to the support center) constitutes a workpiece support member that supports the end face of the other axial end (the right end in FIG. 1) of the workpiece W. In detail, the tailstock center 41 supports the workpiece W while being pressed in the axial direction against a tailstock-side center hole (hereinafter also referred to as "center hole WL") that constitutes a supported portion WL formed on 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 rotatable.

[0032] 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.

[0033] In the first embodiment, the tailstock device 40 is equipped with an adjustment mechanism 42, which is formed of, for example, a spring, and is configured so that the tailstock center 41 exerts a pressing force. Here, when the tailstock center 41 generates a pressing force against the workpiece W, the spindle center 34 also exerts a pressing force against the workpiece W as a reaction. In detail, the adjustment mechanism 42 is configured so that the tailstock center 41 and the spindle center 34 can adjust the pressing force against the workpiece W in the axial direction of the workpiece W. In other words, the adjustment mechanism 42 is configured so that the tailstock center 41 and the spindle center 34 can adjust the supporting force of the workpiece W. Here, the pressing force against the workpiece W by the tailstock center 41 and the spindle center 34 can be adjusted by an actuator, or can be adjusted by an operator.

[0034] The wheel head 50 is provided with a grinding wheel T 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).

[0035] 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.

[0036] 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.

[0037] 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 member that supports the grinding wheel T.

[0038] 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.

[0039] 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.

[0040] 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 a grinding program 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.

[0041] In addition, if the axial pressing force applied to the workpiece W by the tailstock center 41 and the spindle center 34 can be adjusted by an actuator, the control device 3a can adjust the axial pressing force by controlling the actuator.

[0042] 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 workpiece side dynamic stiffness table storage unit 103, a tool side dynamic stiffness table storage unit 104, a dynamic stiffness determination condition acquisition unit 105, a dynamic stiffness determination unit 106, a correction amount calculation unit 107, and an output unit 108.

[0043] 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 and the control device 3a, 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 performed by the grinding machine 2 and the control device 3a, the command value acquisition unit 101 can acquire command values ​​directly from the control device 3a.

[0044] 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.

[0045] 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.

[0046] In this embodiment, 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. In this embodiment, 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 circumferential surface of the grinding wheel T, in addition to the above estimation targets.

[0047] 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 .

[0048] 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).

[0049] 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 (p) 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.

[0050] 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.

[0051] 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.

[0052] 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, 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 quadrangle a1-a2-b1-b2.

[0053] 2 calculates the grinding efficiency Z' based on the amount of interference calculated by the interference amount calculation unit 111. The grinding efficiency Z' calculates the amount of interference per unit time, that is, the volume of the workpiece W ground by the grinding wheel T in unit time.

[0054] 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.

[0055] 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').

[0056] 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'.

[0057] The workpiece-side dynamic stiffness table storage unit 103 stores dynamic stiffness data Cw, Kw (hereinafter referred to as workpiece-side dynamic stiffness data) related to the workpiece W side when the workpiece W side and the grinding wheel T side are separated by the machining portion as a boundary. The workpiece-side dynamic stiffness table storage unit 103 includes a dynamic stiffness table storage unit 103a related to the workpiece W, a dynamic stiffness table storage unit 103b related to each device 20, 30, 40 constituting the workpiece support member, and a correspondence relationship storage unit 103c for calculating contact dynamic stiffness, which is the dynamic stiffness of the contact portion between the workpiece W and the workpiece support member (spindle center 34, tailstock center 41).

[0058] The dynamic stiffness table storage unit 103a for the workpiece W stores dynamic stiffness data Cwa, Kwa of the workpiece W (hereinafter referred to as workpiece dynamic stiffness data). The workpiece dynamic stiffness data Cwa, Kwa can be acquired, for example, by known hammering or FEM analysis of the workpiece W. When there are multiple types of workpieces W to be ground, the dynamic stiffness table storage unit 103a stores the workpiece dynamic stiffness data Cwa, Kwa for each of the multiple types of workpieces W.

[0059] The dynamic stiffness table storage unit 103b for each of the devices 20, 30, 40 constituting the work support member stores dynamic stiffness data Cwb, Kwb (hereinafter referred to as support member dynamic stiffness data) for each of the devices 20, 30, 40 constituting the work support member. The support member dynamic stiffness data Cwb, Kwb can be obtained by hammering or FEM analysis for each of the devices 20, 30, 40 constituting the work support member.

[0060] When the grinding machine 2 is capable of changing the setup of each of the devices 20, 30, 40 constituting the multiple types of workpiece support members, the dynamic stiffness table storage unit 103b stores support member dynamic stiffness data Cwb, Kwb for each of the devices 20, 30, 40 constituting the multiple types of workpiece support members. In addition, when the support member dynamic stiffness data Cwb, Kwb changes depending on the machining conditions, etc., the dynamic stiffness table storage unit 103b stores the correspondence between the machining conditions, etc. and the support member dynamic stiffness data Cwb, Kwb.

[0061] The correspondence relationship storage unit 103c stores correspondence relationships for calculating dynamic stiffness data Cwc, Kwc (hereinafter referred to as contact dynamic stiffness data) at the contact portion between the workpiece W and the workpiece support members (spindle center 34, tailstock center 41). In the first embodiment, the correspondence relationship storage unit 103c stores correspondence relationships between the machining position I shown in Fig. 5 and differential bending angles ΔθL, ΔθR, which will be described later.

[0062] 3-1. Correspondence between processing position I and differential bending angles ΔθL and ΔθR The correspondence between the processing position I shown in FIG. 5 and the differential bending angles ΔθL and ΔθR, which will be described later, will be explained below with reference to FIGS. 6(a) and 6(b).

[0063] First, the initial state shown in FIG. 6(a) is the state before the workpiece W is subjected to a force from the grinding wheel T. When the workpiece W is ground by the grinding wheel T, a force is applied from the grinding wheel T to the processing position I of the workpiece W, as shown in FIG. 6(b), causing the workpiece W to bend toward the side opposite the grinding wheel T. The end portions of the workpiece W, where the center holes WR and WL are located, which are the supported portions of the workpiece W, each change so as to tilt relative to the axis SO of the workpiece W in the initial state. The amount of change in one center hole WR of the workpiece W from the initial state can be expressed as the angle θWR between the axis SO of the workpiece W in the initial state and the axis SWR at the end where the center hole WR is located. Similarly, the amount of change in the other center hole WL of the workpiece W from the initial state can be expressed as the angle θWL between the axis SO of the workpiece W in the initial state and the axis SWL at the end where the center hole WL is located.

[0064] 6(b), when the workpiece W is ground by the grinding wheel T, the workpiece W bends, and the spindle center 34 and tailstock center 41, which serve as workpiece support members, also bend. As a result, the spindle center 34 and tailstock center 41 also change so as to become inclined relative to the axis S0 of the workpiece W in its initial state. The amount of change in the tailstock center 41 from its initial state can be expressed as the angle θCR between the axis S0 of the workpiece W in the initial state and the axis SCR of the tailstock center 41 after the change. Similarly, the amount of change in the spindle center 34 from its initial state can be expressed as the angle θCL between the axis S0 of the workpiece W in the initial state and the axis SCL of the spindle center 34 after the change.

[0065] 6(b), there is a discrepancy between the amount of change θWR of the center hole WR of the workpiece W and the amount of change θCR of the tailstock center 41. The absolute value of this discrepancy in amount of change is defined as the differential bending angle ΔθR. Similarly, there is a discrepancy between the amount of change θWL of the center hole WL of the workpiece W and the amount of change θCL of the spindle center 34. The absolute value of this discrepancy in amount of change is defined as the differential bending angle ΔθL.

[0066] The differential bending angles ΔθR and ΔθL each change based on the machining position I. In this embodiment, the position where a pressure F of 1 N is applied to the workpiece W is defined as a virtual machining position, and the virtual machining position is moved axially from the position of one center hole WR to the position of the other center hole WL. Actual measured values ​​of the differential bending angles ΔθR and ΔθL are then acquired, and a correspondence relationship between the machining position I and the differential bending angle Δθ shown in FIG. 5 is created. Then, as described above, the correspondence relationship is stored in the correspondence relationship storage unit 103c. Note that, instead of creating the correspondence relationship by acquiring the actual measured values ​​of the differential bending angles ΔθR and ΔθL, the correspondence relationship between the machining position I and the variations θWR, θWL, θCR, and θCL may be created by theoretically calculating the relationship between the machining position I and the differential bending angles ΔθR and ΔθL.

[0067] 2 stores dynamic stiffness data Ct, Kt (hereinafter referred to as tool side dynamic stiffness data) relating to the grinding wheel T side when the workpiece W side and the grinding wheel T side are separated by the machining portion. In other words, the tool side dynamic stiffness table storage unit 104 stores tool side dynamic stiffness data Ct, Kt for the grinding wheel head 50 including the grinding wheel T. The tool side dynamic stiffness table storage unit 104 stores tool side dynamic stiffness data Ct, Kt for each type of grinding wheel T, for example.

[0068] Furthermore, in a configuration in which the grinding wheel T is supported by a hydrostatic bearing and the pressure of the hydrostatic bearing is controllable, the tool-side dynamic stiffness data Ct, Kt may be data that changes depending on the pressure of the hydrostatic bearing. Therefore, the tool-side dynamic stiffness table storage unit 104 may store the damping coefficient Ct and the spring constant Kt depending on the pressure of the hydrostatic bearing as a machining condition. In cases in which the tool-side dynamic stiffness data Ct, Kt change depending on the machining conditions, etc., the tool-side dynamic stiffness table storage unit 104 stores the correspondence between the machining conditions, etc. and the tool-side dynamic stiffness data Ct, Kt.

[0069] 4. Obtaining dynamic stiffness determination conditions 2, the dynamic stiffness determination condition acquisition unit 105 acquires the dynamic stiffness determination conditions when grinding is performed by the grinding machine 2. In detail, the dynamic stiffness determination condition acquisition unit 105 acquires the dynamic stiffness determination conditions at the time of estimation (time to be processed) by the estimation unit 102. The dynamic stiffness determination conditions acquired by the dynamic stiffness determination condition acquisition unit 105 are information used by the dynamic stiffness determination unit 106 to calculate each dynamic stiffness. The acquired dynamic stiffness determination 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.

[0070] When the processing estimation device 3b is a simulation device independent of the grinding machine 2, the dynamic stiffness determination condition acquisition unit 105 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 dynamic stiffness determination condition acquisition unit 105 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 regarding the conditions directly from the control device 3a of the grinding machine 2.

[0071] 5. Configuration of dynamic stiffness determination unit 106 The dynamic stiffness determiner 106 determines dynamic stiffness data that affect the grinding process. The dynamic stiffness determiner 106 separately determines the workpiece side dynamic stiffness data Cw, Kw and the tool side dynamic stiffness data Ct, Kt shown in Fig. 7. That is, the dynamic stiffness determiner 106 includes a workpiece side dynamic stiffness determiner 121 and a tool side dynamic stiffness determiner 125.

[0072] The workpiece-side dynamic stiffness (Cw, Kw) and the tool-side dynamic stiffness (Ct, Kt) will be explained with reference to Fig. 7. The workpiece-side 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 unit 40. On the other hand, the tool-side 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 explained in detail below.

[0073] 5-1. Workpiece side dynamic stiffness (Cw, Kw) The workpiece-side dynamic stiffness (Cw, Kw) is the dynamic stiffness exhibited when the workpiece W is supported by the spindle unit 30 and the unit 40, which serve as workpiece support members constituting the grinding machine 2. The workpiece-side dynamic stiffness (Cw, Kw) is defined by the damping coefficient Cw and the 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 position of the grinding machine 2 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 position of the grinding machine 2 and the external force that the workpiece W receives. Note that each dynamic stiffness may include a mass term Mw in addition to the damping coefficient and spring constant.

[0074] As shown in FIG. 7, the workpiece-side dynamic stiffness (Cw, Kw) can be decomposed into the workpiece dynamic stiffness (Cwa, Kwa), the support member dynamic stiffness (Cwb, Kwb), and the contact dynamic stiffness (Cwc, Kwc) between the workpiece W and the workpiece support member (spindle center 34, tailstock center 41).

[0075] The workpiece dynamic stiffness determination unit 121 has a workpiece dynamic stiffness calculation unit 122, a support member dynamic stiffness calculation unit 123, and a contact dynamic stiffness calculation unit 133. The workpiece dynamic stiffness calculation unit 122 calculates workpiece dynamic stiffness data Cwa, Kwa corresponding to the type of workpiece W acquired by the dynamic stiffness determination condition acquisition unit 105 from the dynamic stiffness table stored in the dynamic stiffness table storage unit 103a related to the workpiece W. Furthermore, the support member dynamic stiffness calculation unit 123 calculates support member dynamic stiffness data Cwb, Kwb corresponding to the type of workpiece support member acquired by the dynamic stiffness determination condition acquisition unit 105 from the dynamic stiffness tables stored in the dynamic stiffness table storage unit 103b related to each of the devices 20, 30, 40 constituting the workpiece support member.

[0076] The contact dynamic stiffness (Cwc, Kwc) is the dynamic stiffness between the workpiece W and the workpiece support member (spindle center 34, tailstock center 41), and is the dynamic stiffness exerted by contact between the workpiece W and the workpiece support member (spindle center 34, tailstock center 41). As described above, the contact dynamic stiffness (Cwc, Kwc) changes depending on the machining position I. The contact dynamic stiffness (Cwc, Kwc) is defined by the damping coefficient Cwc and the spring constant Kwc. The damping coefficient Cwc is a value that represents the relationship between the relative speed between the workpiece W and the workpiece support member (spindle center 34, tailstock center 41) and the external force that the workpiece W receives. The spring constant Kwc is a value that represents the relationship between the relative position between the workpiece W and the workpiece support member (spindle center 34, tailstock center 41) and the external force that the workpiece W receives. The contact dynamic stiffness (Cwc, Kwc) is calculated by a contact dynamic stiffness calculation system 130 shown in FIG.

[0077] 5-1-1. Configuration of contact dynamic stiffness calculation system 130 The configuration of the contact dynamic stiffness calculation system 130 shown in Fig. 7 will be described. The contact dynamic stiffness calculation system 130 is made up of a basic information acquisition unit 131, a differential bending angle calculation unit 132, and a contact dynamic stiffness calculation unit 133, all included in the workpiece-side dynamic stiffness determination unit 121, and a correspondence relationship storage unit 103c included in the workpiece-side dynamic stiffness table storage unit 103.

[0078] The basic information acquisition unit 131 acquires basic information related to the workpiece W. The basic information includes at least position information of a machining position I on the workpiece W. Furthermore, the basic information may include maximum support diameters dR and dL of the center holes WR and WL on the workpiece W shown in FIG. 6(a). The basic information may also include information related to the shape of the workpiece W. In this embodiment, the basic information includes information related to the machining position I, the maximum support diameters dR and dL, and the shape of the workpiece W.

[0079] The differential bending angle calculation unit 132 shown in FIG. 2 calculates differential bending angles ΔθR, ΔθL corresponding to the machining position I on the workpiece W based on the machining position I included in the basic information acquired by the basic information acquisition unit 131 and the above-mentioned correspondence relationship stored in the correspondence relationship storage unit 103c.

[0080] The contact dynamic stiffness calculation unit 133 calculates the contact dynamic stiffnesses Cwc and Kwc using the differential bending angles ΔθR and ΔθL. In this embodiment, the contact dynamic stiffnesses Cwc and Kwc are calculated using the center hole sizes of the center holes WR and WL, which are the supported portions of the workpiece W, acquired by the basic information acquisition unit 131, i.e., the maximum support diameters dR and dL, along with the differential bending angles ΔθR and ΔθL. The contact dynamic stiffnesses (Cwc, Kwc) include the contact dynamic stiffnesses (Cwcr, Kwcr) between one center hole WR of the workpiece W and the tailstock center 41, and the contact dynamic stiffnesses (Cwcl, Kwcl) between the other center hole WL of the workpiece W and the spindle center 34. The contact dynamic stiffness data Cwcr, Kwcr and the contact dynamic stiffness data Cwcl, Kwcl can be defined as follows:

[0081] First, as shown in Figure 6(b), as the differential bending angles ΔθR, ΔθL increase, bending increases at the contact area between the workpiece W and the workpiece support member (spindle center 34, tailstock center 41), and as the differential bending angles ΔθR, ΔθL decrease, bending decreases at the contact area between the workpiece W and the workpiece support member (spindle center 34, tailstock center 41). Furthermore, as the maximum support diameters dR, dL increase, the center holes WR, WL become deeper, and the spindle center 34 and tailstock center 41 penetrate deeper into the center holes WR, WL, so the contact area between the workpiece W and the workpiece support member (spindle center 34, tailstock center 41) becomes larger. Conversely, as the maximum support diameters dR and dL become smaller, the center holes WR and WL become shallower and the spindle center 34 and tailstock center 41 enter the center holes WR and WL more shallowly, thereby reducing the contact area between the workpiece W and the workpiece support members (spindle center 34 and tailstock center 41).As a result, the spring constants Kwcr and Kwcl in the contact dynamic stiffness are inversely proportional to the differential bending angles ΔθR and ΔθL, respectively, and proportional to the maximum support diameters dR and dL.

[0082] Therefore, the spring constants Kwcr and Kwcl in the contact dynamic stiffness can be defined as the following relational expressions (Equation 1 and Equation 2), respectively. Kwcr=α / ΔθR·dR (Equation 1) Kwcl=β / ΔθL·dL (Equation 2) Note that α and β are coefficients, and can be set to values ​​that make the measured spring constants Kwcr and Kwcl calculated from the predetermined differential bending angles ΔθR and ΔθL and the predetermined maximum support diameters dR and dL, which are obtained by actual measurement in advance, equal to the spring constants Kwcr and Kwcl calculated using the above equations 1 and 2.

[0083] On the other hand, since the damping coefficients Cwcr and Cwcl in the contact dynamic stiffness are mainly due to friction damping, if we focus only on friction damping, the differential bending angles ΔθR and ΔθL are proportional to the damping energy. In addition, as the maximum support diameters dR and dL increase, friction increases, and as the maximum support diameters dR and dL decrease, friction decreases.

[0084] Therefore, the damping coefficients Cwcr and Cwcl in the contact dynamic stiffness can be defined as the following relational expressions (Equation 3 and Equation 4), respectively. Cwcr=γ·ΔθR·dR (Equation 3) Cwcl=δ·ΔθL·dL (Equation 4) Note that γ and δ are coefficients and can be determined in the same manner as α and β.

[0085] As described above, the contact dynamic stiffness calculation section 133 can calculate the contact dynamic stiffnesses Cwc (Cwcr and Cwcl) and Kwc (Kwcr and Kwcl) from ΔθR, ΔθL and dR, dL based on the relational expressions (1) to (4) above.

[0086] 5-2. Tool side dynamic rigidity As shown in FIG. 7, the tool-side dynamic stiffness (Ct, Kt) is the dynamic stiffness related to the wheel head 50, including the grinding wheel T. The tool-side dynamic stiffness (Ct, Kt) 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 50 and the external force applied to the grinding wheel T. 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 50 and the external force applied to the grinding wheel T. The tool-side dynamic stiffness (Ct, Kt) includes the dynamic stiffness (Cta, Kta) of the grinding wheel T and the dynamic stiffness (Ctb, Ktb) that the wheel head body 51 exerts when supporting the grinding wheel T. Note that each dynamic stiffness may include a mass term in addition to the damping coefficient and spring constant.

[0087] The tool side dynamic stiffness (Ct, Kt) can be calculated by the tool side dynamic stiffness determination unit 125 shown in Figure 2 based on the dynamic stiffness determination conditions acquired by the dynamic stiffness determination condition acquisition unit 105 and the correspondence between the dynamic stiffness determination conditions stored in the tool side dynamic stiffness table memory unit 104 and the tool side dynamic stiffness data Ct, Kt.

[0088] 6. Correction amount calculation unit 107 The correction amount calculation unit 107 calculates the correction amount for the relative displacement of the grinding wheel T and workpiece W in the X-axis direction due to the grinding resistance based on each dynamic stiffness data determined by the dynamic stiffness determination unit 106. The correction amount for the displacement can be found from each dynamic stiffness data and the grinding resistance. In other words, the correction amount for the displacement can be calculated from the grinding resistance, the workpiece-side dynamic stiffness data Cw, Kw, and the tool-side dynamic stiffness data Ct, Kt.

[0089] In this embodiment, however, the workpiece dynamic stiffness data Cw, Kw include the workpiece dynamic stiffness data Cwa, Kwa, the support member dynamic stiffness data Cwb, Kwb, and the contact dynamic stiffness data Cwc, Kwc. In other words, the correction amount for displacement is calculated from the grinding force, the workpiece dynamic stiffness data Cwa, Kwa, Cwb, Kwb, Cwc, Kwc, and the tool dynamic stiffness data Ct, Kt.

[0090] The correction amount calculation unit 107 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.

[0091] 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 107 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.

[0092] In particular, in the first embodiment, the correction amount calculation unit 107 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.

[0093] 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 as the relative position obtained by the command value acquisition unit 101 plus the correction amount calculated by the correction amount calculation unit 107. In other words, the interference amount calculation unit 111 calculates the amount of interference based on the relative position obtained by the command value and the correction amount calculated using each dynamic stiffness data.

[0094] 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.

[0095] The output unit 108 outputs the estimation target estimated by the estimation unit 102. That is, the output unit 108 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 machine state of the processing system 1 (corresponding to the machine state of the grinding machine 2). The output unit 108 may, for example, teach the estimation result to a teaching device (not shown). The output unit 108 can also output the estimation result to the control device 3a of the grinding machine 2. In this case, the control device 3a can use the estimation result to correct, for example, the grinding conditions. That is, the control device 3a can control the grinding process using the estimation result.

[0096] Furthermore, the control device 3a can use the estimation results to control the adjustment mechanism 42 of the tailstock device 40 to adjust the pressing force of the spindle center 34 and the tailstock center 41. Furthermore, if the grinding machine 2 is equipped with a chuck, the control device 3a can also use the estimation results to adjust the gripping force of the chuck. The control device 3a can appropriately select the control target using the estimation results.

[0097] Furthermore, the control device 3a performs the various processes described above using the estimation results. In addition, the control device 3a can also control machining using various dynamic stiffnesses determined by the dynamic stiffness determination unit 106, regardless of the estimation results. For example, the control device 3a can adjust the pressing force of the spindle center 34 and tailstock center 41, adjust the gripping force of the chuck, etc., using various dynamic stiffnesses determined by the dynamic stiffness determination unit 106, regardless of the estimation results.

[0098] 7. Action and Effects According to this embodiment, the contact dynamic stiffness calculation unit 133 calculates the spring constant Kwc and damping coefficient Cwc at the contact portion between the workpiece W and the workpiece support member (spindle center 34, tailstock center 41) based on basic information including information on the machining position I and the differential bending angles ΔθR and ΔθL calculated by the differential bending angle calculation unit 132, and then calculates the contact dynamic stiffness (Kwc, Cwc), which is the dynamic stiffness at the contact portion, based on the spring constant Kwc and the damping coefficient Cwc. As a result, the contact dynamic stiffness (Kwc, Cwc) is calculated taking into account the deviation that occurs between the workpiece bending angles θWR, θWL, which are the bending angles of the workpiece W, and the support member bending angles θCR, θCL, which are the bending angles of the workpiece support member (spindle center 34, tailstock center 41). As a result, the contact dynamic stiffness can be calculated with high accuracy, taking into account the contact state between the workpiece W and the workpiece support member (spindle center 34, tailstock center 41).

[0099] Furthermore, in the first embodiment, a correspondence relationship storage unit 103c is provided that stores in advance the correspondence relationship between the processing position I and the differential bending angles ΔθR and ΔθL. The differential bending angle calculation unit 132 calculates the differential bending angles ΔθR and ΔθL based on the correspondence relationship stored in the correspondence relationship storage unit 103c and the processing position I included in the basic information. This makes it possible to easily obtain the differential bending angles ΔθR and ΔθL based on the processing position I, and enables high-speed calculation processing.

[0100] Furthermore, in the first embodiment, the basic information acquisition unit 131 further acquires, as the basic information, maximum support diameters dR, dL of the center holes WR, WL, which are supported portions of the workpiece W that are supported by the workpiece support members (spindle center 34, tailstock center 41). Then, in the contact dynamic stiffness calculation unit 133, the spring constants Kwcr, Kwcl and the damping coefficients Cwcr, Cwcl are calculated based on at least the maximum support diameters dR, dL acquired by the basic information acquisition unit 131 and the differential bending angles ΔθR, ΔθL calculated by the differential bending angle calculation unit 132. This makes it possible to more accurately consider the contact state between the workpiece W and the workpiece support members (spindle center 34, tailstock center 41), thereby enabling the dynamic stiffness to be calculated with even higher accuracy.

[0101] Moreover, the machining system 1 in the present embodiment 1 includes a contact dynamic stiffness calculation system 130, a machining device 2 that machines a workpiece W, a control device 3a that controls machining by the machining device 2, and an estimation unit 102 that estimates a machining result of the workpiece W by the machining device 2 based on workpiece-side dynamic stiffness (Cw, Kw) including contact dynamic stiffness (Cwc, Kwc) calculated by the contact dynamic stiffness calculation system 130. The control device 3a controls the machining by the machining device 2 based on the machining result estimated by the estimating unit 102. This allows the workpiece W to be machined while reflecting the machining result estimated based on the workpiece-side dynamic stiffness (Cw, Kw) including the contact dynamic stiffness (Cwc, Kwc), and therefore the workpiece W can be formed into a target shape with higher accuracy.

[0102] In the processing system 1 of the present embodiment 1, the tool in the processing device 2 is a grinding wheel T, and the processing device 2 is a grinding machine. This allows the workpiece W processed by the grinding machine to be formed into a target shape with higher precision.

[0103] In addition, in the first embodiment, the workpiece dynamic stiffness (Cw, Kw) is separated into the workpiece dynamic stiffness (Cwa, Kwa), the support member dynamic stiffness (Cwb, Kwb), and the contact dynamic stiffness (Cwc, Kwc). Separating each dynamic stiffness data in this manner facilitates the determination of each dynamic stiffness data. For example, even if the devices 20, 30, and 40 constituting the workpiece W and the workpiece support member are the same, adjusting only the pressing forces of the spindle center 34 and the tailstock center 41 changes only the contact dynamic stiffness data Cwc and Kwc. This simplifies the calculation process. For example, when the estimation process by the processing estimation device 3b and the control of the grinding process by the control device 3a are performed simultaneously, high-precision grinding can be achieved by performing the calculation process at high speed.

[0104] As described above, according to the first embodiment, it is possible to provide a contact dynamic stiffness calculation system 130 that can calculate the contact dynamic stiffness (Cwc, Kwc) with high accuracy, taking into account the contact state between the workpiece W and the workpiece support members (spindle center 34, tailstock center 41).

[0105] (Embodiment 2) In the above-described first embodiment, the processing unit 3 is provided with a control device 3a and a processing estimation device 3b as shown in Fig. 1, but in the second embodiment shown in Fig. 8, the processing unit 3 is provided with a control device 3a and a dynamic stiffness determination unit 106, but is not provided with a processing estimation device 3b. As shown in Fig. 9, the configuration of the dynamic stiffness determination unit 106 is the same as in the above-described first embodiment. Note that the same reference numerals are used to designate components equivalent to those in the first embodiment, and their description will be omitted.

[0106] 9, in the second embodiment, the workpiece-side dynamic stiffness (Cw, Kw) determined by the dynamic stiffness determination unit 106 is input to the control device 3a together with a command value. The workpiece-side dynamic stiffness (Cw, Kw) includes the contact dynamic stiffness (Cwc, Kwc) calculated by the contact dynamic stiffness calculation system 130. The control device 3a controls the machining by the machining device 2 based on these.

[0107] That is, the machining system 1 of the second embodiment includes a contact dynamic stiffness calculation system 130, a machining device 2 that machines a workpiece W, and a control device 3a that controls machining by the machining device 2. The control device 3a controls machining by the machining device 2 based on the workpiece-side dynamic stiffness (Cw, Kw) including the contact dynamic stiffness (Cwc, Kwc) calculated by the contact dynamic stiffness calculation system 130. This makes it possible to control machining by the machining device 2 without using the estimation result by the estimating unit 102 of the first embodiment, thereby enabling faster calculation processing and achieving high-precision grinding.

[0108] (Embodiment 3) A machining system 201 according to the third embodiment will be described with reference to Fig. 10. The machining system 201 is a machining system that performs cutting. The machining system 201 includes a lathe 202 as a machining device and a processing unit 203.

[0109] The lathe 202 turns the workpiece W by rotating the workpiece W and moving the cutting tool T2 relative to the workpiece W. The processing unit 203 includes a control device 203a that controls the lathe 202, and a processing estimation device 203b that estimates an estimation target related to processing. The control device 203a can control the cutting processing by controlling the lathe 202. The processing estimation device 203b estimates at least one of the state of the workpiece W or the cutting tool T2 during cutting processing on the lathe 202, the shape of the workpiece W, the shape of the cutting tool T2, and the machine state of the processing system 201 (corresponding to the machine state of the lathe 202). The processing estimation device 203b performs an estimation process of the above estimation target by inputting information used in cutting processing and performing a simulation.

[0110] The lathe 202 includes, for example, a bed 210, a spindle unit 220, a tailstock unit 230, and a tool table 250. The spindle unit 220 and the tailstock unit 230 function as workpiece support members. The spindle unit 220 is fixed to the upper surface of the bed 210, supports one end WL of the workpiece W, and drives the workpiece W to rotate. The spindle unit 220 includes a spindle housing 221, a spindle 222, a spindle motor 223, a chuck 224, a spindle detector 225, and a spindle drive circuit (not shown).

[0111] The spindle housing 221 is fixed onto the bed 210. The spindle 222 is rotatably supported by the spindle housing 221 via a bearing. The spindle motor 223 drives the spindle 222 to rotate. The chuck 224 is fixed to the spindle 222 and grips one end of the workpiece W. The spindle detector 225 and the spindle drive circuit are provided for driving the spindle motor 223. In more detail, the chuck 224 constitutes a workpiece support member, and one end of the workpiece W gripped by the chuck 224 constitutes a supported portion WL. The maximum support diameter dL of the supported portion WL corresponds to the diameter of the outer circumferential surface of the supported portion WL with which the jaws of the chuck 224 abut.

[0112] The tailstock device 230 is disposed on the bed 210 so as to face the spindle device 220 in the Z-axis direction. The tailstock device 230 is provided on the bed 210 so as to be movable in the Z-axis direction. The tailstock device 230 includes a tailstock center 231 that supports the other end of the workpiece W. In more detail, the tailstock center 231 fits into a center hole WR at the other end of the workpiece W to form a workpiece support member that supports the workpiece W.

[0113] The tool table 250 includes a Z-axis slide table 251, an X-axis slide table 252, a turret (a swivel-type tool rest) 253, and a plurality of cutting tools T2. The Z-axis slide table 251 is supported on a Z-axis guide surface 211 of the bed 210 so as to be movable in the Z-axis direction, and is moved in the Z-axis direction by a Z-axis drive mechanism 212 provided on the bed 210.

[0114] X-axis slide base 252 is supported on X-axis guide surface 251a on Z-axis slide base 251 so as to be movable in the X-axis direction, and is moved in the X-axis direction by X-axis drive mechanism 251b provided on Z-axis slide base 251. Turret 253 is provided on X-axis slide base 252 so as to be rotatable around an axis parallel to the Z-axis direction. Multiple cutting tools T2 are fixed to the outer peripheral surface of turret 253. The multiple cutting tools T2 may be different types of tools.

[0115] The control device 203a is a CNC (Computer Numerical Control) device and a PLC (Programmable Logic Controller) device that executes machining control. That is, the control device 203a drives the Z-axis drive mechanism 212 and the X-axis drive mechanism 251b as moving devices based on a cutting program to control the position of the cutting tool T2. That is, the control device 203a moves the workpiece W and the cutting tool T2 relative to each other by controlling the positions of the cutting tool T2 and the like. Furthermore, the control device 203a controls the rotation of the spindle 222 and the turret 253.

[0116] The processing estimation device 203b of this embodiment has the same configuration as the processing estimation device 3b of the first embodiment shown in Fig. 2. However, the grinding in the first embodiment is changed to cutting, and the grinding wheel T is changed to a cutting tool T2.

[0117] Next, the workpiece-side dynamic stiffness (Cw, Kw) and the tool-side dynamic stiffness (Ct, Kt) in this embodiment will be described with reference to FIG. 11 . The workpiece-side dynamic stiffness (Cw, Kw) is the dynamic stiffness exhibited when the workpiece W is supported by the chuck 224 and tailstock center 231 serving as workpiece support members constituting the lathe 202. The workpiece-side dynamic stiffness (Cw, Kw) is defined by a damping coefficient Cw and a spring constant Kw. 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 unit 220 and tailstock unit 230 and the external force applied to 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 unit 220 and tailstock unit 230 and the external force applied to the workpiece W.

[0118] As in embodiment 1, the workpiece side dynamic stiffness (Cw, Kw) can be decomposed into the workpiece dynamic stiffness (Cwa, Kwa), the support member dynamic stiffness (Cwb, Kwb), and the contact dynamic stiffness (Cwc, Kwc) between the workpiece W and the workpiece support member (chuck 224, tailstock center 231).

[0119] The tool-side dynamic stiffness (Ct, Kt) is the dynamic stiffness related to the tool table 250, including the cutting tool T2. The tool-side dynamic stiffness (Ct, Kt) 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 cutting tool T2 with respect to a reference position on the tool table 250 and the external force that the cutting tool T2 receives. The spring constant Kt is a value that represents the relationship between the relative position of the cutting tool T2 with respect to a reference position on the tool table 250 and the external force that the cutting tool T2 receives.

[0120] The processing system 201 in the third embodiment has the same effects as the processing system 1 in the first embodiment.

[0121] (others) In the above-mentioned first to third embodiments, examples have been described in which grinding is performed using the grinding machine 2 and cutting is performed using the lathe 202. In addition to these, cutting can also be performed using a machining center. [Explanation of symbols]

[0122] 1, 201 Processing System 130 Contact Dynamic Stiffness Calculation System 2 Grinding machine (processing equipment) 202 Lathe (processing equipment) 3a Control device 3b Processing estimation device 34 Spindle center (workpiece support member) 41, 231 Tailstock center (workpiece support member) 203a Control device 203b Processing estimation device 224 Chuck (workpiece support member)

Claims

1. A contact dynamic stiffness calculation system that calculates contact dynamic stiffness at a contact portion between a workpiece and a workpiece support member when the workpiece supported by the workpiece support member is machined by a tool, comprising: The workpiece support member is constituted by a tailstock center, the workpiece has a center hole into which the tailstock center is inserted, the contact portion is a portion where the tailstock center and the center hole come into contact with each other, the contact dynamic stiffness is dynamic stiffness between the workpiece and the tailstock center exerted by contact between the workpiece and the tailstock center, and is defined by a damping coefficient and a spring constant; a basic information acquiring unit that acquires basic information about the workpiece including at least information about the machining position on the workpiece and the maximum support diameter of the center hole; a differential bend angle calculation unit that calculates a differential bend angle that is the difference between a workpiece bend angle, which is the angle between the axis of the workpiece in an initial state where no acting force is applied from the tool to the workpiece supported by the workpiece support member and the axis of the workpiece at a portion of the workpiece where the center hole is located in an acting state where an acting force is applied from the tool to the workpiece, and a support member bend angle, which is the angle between the axis of the workpiece in the initial state and the axis of the tailstock center in the acting state; a contact dynamic stiffness calculation unit that calculates a spring constant and a damping coefficient at a contact portion between the workpiece and the workpiece support member based on the basic information acquired by the basic information acquisition unit and the differential bending angle calculated by the differential bending angle calculation unit, and calculates contact dynamic stiffness of the workpiece based on the spring constant and the damping coefficient; A contact dynamic stiffness calculation system comprising:

2. a correspondence relationship storage unit in which a correspondence relationship between the processing position and the differential bending angle is stored in advance; 2. The contact dynamic stiffness calculation system according to claim 1, wherein the differential bending angle calculation unit calculates the differential bending angle based on the correspondence stored in the correspondence storage unit and the processing position included in the basic information.

3. A contact dynamic stiffness calculation system as described in claim 1 or 2, wherein the contact dynamic stiffness calculation unit calculates the spring constant and the damping coefficient based on at least the maximum support diameter acquired by the basic information acquisition unit and the differential bending angle calculated by the differential bending angle calculation unit.

4. A machining system comprising the contact dynamic stiffness calculation system according to any one of claims 1 to 3, a machining device that machines the workpiece, and a control device that controls machining by the machining device, The control device controls machining by the machining device based on the dynamic stiffness of the workpiece, including the contact dynamic stiffness calculated by the contact dynamic stiffness calculation system.

5. A machining system comprising: the contact dynamic stiffness calculation system according to any one of claims 1 to 3; a machining device that machines the workpiece; a control device that controls machining by the machining device; and an estimation unit that estimates a machining result of the workpiece by the machining device based on a dynamic stiffness of the workpiece including the contact dynamic stiffness calculated by the contact dynamic stiffness calculation system, The control device controls the processing by the processing device based on the processing result estimated by the estimation unit.

6. 6. The processing system according to claim 4, wherein the tool is a grinding wheel and the processing device is a grinding machine.

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