Method for measuring the diameter of a workpiece and machine tool

Abstract

A workpiece diameter measurement method includes: measuring a coordinate of a point P at which a coordinate in a first direction orthogonal to a rotation axis of a main shaft of a machine tool is maximum or minimum on an outer peripheral surface of a cylindrical workpiece supported in a manner that the center axis coincides with the rotation axis of the main shaft; calculating a distance D2 in the first direction of the point P from a reference point Q at which a distance D1 in the first direction from the rotation axis is known; and calculating a workpiece diameter of the cylindrical workpiece based on the distance D1 and the distance D2.

Description

Technical Field

[0001] This invention relates to a method for measuring the diameter of a workpiece and a machine tool thereof. Background Technology

[0002] In machine tools such as multi-tasking machines and turret lathes, for example, a cutting tool mounted on the lower tool post is used to cut a cylindrical workpiece mounted on the spindle. In the case of a cylindrical workpiece, the outer diameter of the workpiece is measured continuously to determine the grinding status. The diameter of the cylindrical workpiece mounted on the spindle can be calculated by measuring the coordinates of three points along the outer circumference of the workpiece using a contact-type position detection sensor.

[0003] For example, Patent Document 1 proposes a method for measuring the inner and outer diameters of a circular workpiece, characterized in that, with two probes in a reference position, a third probe is moved from a predetermined position until it and the two probes abut against the inner or outer circumferential surface of the workpiece, and the inner or outer diameter of the circular workpiece is calculated by multiplying the measured value by a correction value obtained based on the moving distance of the third probe.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2000-117629 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, using two or even a third probe results in a large number of probes and increased operational complexity. Alternatively, contact sensors can be mounted on the tool spindle (first tool post) or tool post (second tool post) to measure the coordinates of three points along the outer circumference of the workpiece. However, to ensure measurement accuracy, the distances between the three points must not be too close. Measuring the coordinates of such three points is inefficient because the travel distance of the tool spindle or lower tool post increases, leading to longer measurement time. Furthermore, the limited travel length of the tool spindle and, especially, the lower tool post, restricts the types of workpieces whose diameter can be measured with good accuracy.

[0009] Methods used to solve problems

[0010] In view of the above, a method for measuring the diameter of a workpiece according to the present invention comprises: a step of measuring the coordinates of a point P, whose coordinates in a first direction orthogonal to the rotation axis are at a maximum or minimum, on the outer circumferential surface of a cylindrical workpiece supported in a manner where its central axis coincides with the rotation axis of the spindle of a machine tool; a step of calculating a reference point Q, whose distance D1 from the rotation axis in the first direction is known, and a distance D2 from the point P in the first direction; and a step of calculating the diameter of the cylindrical workpiece based on the distances D1 and D2.

[0011] Another technical solution of the present invention relates to a machine tool, comprising: a spindle having a rotary axis; a sensor that calculates the coordinates of a point P, whose coordinates in a first direction orthogonal to the rotary axis are a maximum or minimum, and the coordinates of a reference point Q, whose distance D1 in the first direction from the rotary axis is known, on the outer circumferential surface of a cylindrical workpiece supported in a manner where its central axis coincides with the rotary axis; and a calculation unit that calculates the distance D2 between the point P and the reference point Q in the first direction based on the coordinates of the point P and the reference point Q, and calculates the workpiece diameter of the cylindrical workpiece based on the distances D1 and D2.

[0012] Invention Effects

[0013] According to the above-described technical solution of the present invention, the diameter of a workpiece can be measured quickly and with good accuracy. Attached Figure Description

[0014] Figure 1 This is a front view showing an example of the structure of the machine tool according to this embodiment.

[0015] Figure 2 It is Figure 1 A conceptual diagram of the machine tool's workpiece, spindle, and first and second tool holders as viewed from the Z-direction.

[0016] Figure 3 This is a diagram showing the process of measuring the coordinates of a point P on the outer circumference of a cylindrical workpiece, where the coordinates in the X direction, which is orthogonal to the axis of rotation, are minimal.

[0017] Figure 4 This is a diagram showing the process of measuring the coordinates of a point P, whose coordinates in the X direction orthogonal to the axis of rotation are minimal, on the outer circumferential surface of another cylindrical workpiece.

[0018] Figure 5 This is a front view showing the structure of an example of a machine tool with respect to other embodiments. Detailed Implementation

[0019] The following examples of machine tools include, but are not limited to, lathes, multi-axis machining centers with turning functions using fixed tools and milling functions using rotary tools, 5-axis machining centers controlled by two or more rotary axes in addition to the X, Y, and Z axes, and additive manufacturing (AM) machines capable of performing additional machining.

[0020] The machine tool's spindle is equipped with clamps such as chucks to hold the workpiece. The spindle rotates the workpiece about a rotation axis corresponding to the Z-direction. The machine tool can have one spindle and tailstock, or it can have two spindles, a first spindle and a second spindle. The rotation axes of the first spindle and the second spindle are aligned.

[0021] A spindle is a structure that includes a rotating shaft Cc that imparts rotation to the workpiece, a motor, a speed changer, etc.

[0022] A tool post is a general term encompassing the tool spindle (first tool post) for mounting rotary tools and the lower tool post (second tool post) for mounting stationary tools. The tool post is the structure for mounting cutting tools (tools), and there are flat, comb-type, and turret-type types, among others. The tool spindle, on the other hand, is a different structure from the "spindle" and has a rotation axis corresponding to the Z-direction.

[0023] The workpiece is the object to be machined. The workpiece diameter refers to the diameter (or radius) of the cross section perpendicular to the central axis of the cylindrical workpiece.

[0024] The workpiece diameter R measurement method (hereinafter also referred to as the "workpiece diameter measurement method") according to the embodiments of the present invention includes (i) a step (hereinafter also referred to as the "coordinate measurement step") on the outer circumferential surface of a cylindrical workpiece supported in a manner in which the central axis coincides with the rotation axis Cc of the spindle of the machine tool, measuring the coordinates of a point P that is a maximum or minimum in a first direction orthogonal to the rotation axis.

[0025] Point P is a point on the outer circumferential surface of the portion of the workpiece whose diameter R is to be measured. It is a point on the circle (hereinafter referred to as "circle Cw") drawn by the intersection of a plane perpendicular to the central axis of the workpiece and the outer circumferential surface of the workpiece. Furthermore, point P corresponds to the intersection of a straight line passing through the first direction of the central axis of the workpiece and circle Cw. The coordinate measurement process can, for example, involve continuously calculating the coordinates of the vicinity of point P along circle Cw on the outer circumferential surface of the workpiece using contact or non-contact sensors.

[0026] The central angle θ of the arc of the circle Cw for continuously calculating coordinates only needs to be large enough to detect a point P where the coordinates in the first direction are at their maximum or minimum; for example, it can be less than 50 degrees or less than 30 degrees. If it is a contact sensor, point P can be detected by continuously calculating coordinates while moving the sensor's terminals along such an arc. The coordinate calculation can be performed by a processing unit that is associated with both the sensor and the machine tool.

[0027] The first direction orthogonal to the axis of rotation Cc can be any direction, but it can be either the vertical direction (i.e., the X direction) or the horizontal direction (i.e., the Y direction) in terms of ease of determination.

[0028] For example, the coordinates of point P can also be coordinates with a minimum value in the X direction. In this case, point P coincides with the lowest point of the part of the workpiece whose diameter you want to measure. The lowest point can be measured quickly and easily using a sensor located below the workpiece. An arc is selected to continuously calculate the coordinates, passing over point P from below the workpiece.

[0029] Alternatively, the coordinates of point P can be coordinates with the maximum value in the X direction. In this case, point P coincides with the uppermost point of the part of the workpiece whose diameter you want to measure. The uppermost point can be measured, for example, using a sensor mounted on the tool spindle. The coordinates are calculated continuously by selecting an arc that crosses point P from above the workpiece.

[0030] Alternatively, the coordinates of point P can be either minimal or maximal in the Y direction. In this case, point P corresponds to the point at the very front or rear end of the part of the workpiece whose diameter you want to measure when viewed from the front.

[0031] Next, the workpiece diameter measurement method includes a step of calculating the distance D2 in the first direction between reference point Q and point P. Reference point Q only needs to be a point whose distance D1 in the first direction from the rotation axis Cc of the spindle is known. For example, the sensor used in the calculation of point P is moved, the coordinates of reference point Q are calculated, and the distance D2 is calculated based on the coordinates of point P and reference point Q.

[0032] Even with the same machine tool, the position of the rotary axis Cc changes over time due to various factors such as temperature and humidity. On the other hand, the change in the position of the rotary axis Cc is linked to the movement of the spindle, so points on the components constituting the spindle itself remain almost unchanged relative to the rotary axis Cc. If such a point whose position remains almost unchanged relative to the rotary axis Cc is set as a reference point Q, then the distance D1 between the rotary axis Cc in the first direction and the reference point Q is always constant. By pre-measuring the distance D1 and storing it in a storage unit associated with the machine tool, D1 becomes a known value. The reference point Q can, for example, be a point on the chuck of the spindle that holds the workpiece. For example, point Q is a point on the circle (hereinafter referred to as "circle Cz") drawn by the intersection of a plane perpendicular to the rotary axis Cc and the outer circumference of the chuck.

[0033] The calculation of the coordinates of reference point Q can be performed either before or after the calculation of the coordinates of point P. For example, if the coordinates of reference point Q are measured initially, the coordinates of point P and the distance D2 can be calculated quickly. Furthermore, once the coordinates of reference point Q are measured, the same coordinates can be used in multiple workpiece diameter measurements. That is, as long as the initial calibration of the coordinates of reference point Q using the sensor is performed, multiple workpiece diameter measurements can be performed simply by calculating the coordinates of point P.

[0034] Furthermore, when viewed from the Z-direction, the reference point Q may not be collinear with point P and the rotation axis. However, by ensuring that point P, reference point Q, and the rotation axis are on the same straight line, the sensor's travel distance can be shortened, allowing for more efficient measurement of the workpiece diameter. Specifically, when point P is a point with a minimum X-direction coordinate, point Q is preferably a point on circle Cz with a minimum X-direction coordinate (e.g., the lowest point of the chuck). When point P is a point with a maximum X-direction coordinate, point Q is preferably a point on circle Cz with a maximum X-direction coordinate (e.g., the highest point of the chuck).

[0035] Next, the workpiece diameter measurement method includes a step of calculating the diameter of the cylindrical workpiece based on distances D1 and D2. This calculation can be performed by a computation unit that is linked to the machine tool.

[0036] The sensors for detecting the coordinates of point P and the reference point Q can be installed anywhere inside or outside the machine tool. The sensors for detecting the coordinates of point P and the reference point Q can also be the same. For example, the sensors can be mounted on a structure that can move in a plane orthogonal to the axis of rotation. Such a structure can be, for example, the first or second tool post of a machining center, lathe, or other machine tool. The first tool post can be a tool spindle, and the second tool post can be a lower tool post such as a turret. The structure can also be a center rest, tailstock, etc.

[0037] A center rest is a structure that supports a workpiece fixed on a grinding machine, lathe, etc., in the radial direction. A tailstock is a structure with components that press against the workpiece to stabilize it.

[0038] When the sensor is mounted on the tool spindle, the tool and sensor can be changed simply by performing an ATC (Automatic Tool Changer). However, this changeover takes some time. On the other hand, when the sensor is mounted on the lower post of a turret or similar device, the ATC-based changeover is unnecessary. If the tool and sensor are pre-mounted on the turret, they can be changed simply by rotating the turret.

[0039] Typically, the lower tool post has a small travel distance in both the X-direction (vertical) and Y-direction (horizontal forward / backward direction). However, the central angle θ of the arc of the circle Cw, which is continuously calculated to determine the coordinates of point P, is sufficiently small. Therefore, even if the travel distance of the lower tool post is small, it is not a problem at all.

[0040] The machine tool described in this invention is suitable for implementing the above-described workpiece diameter measurement method and includes a spindle with a rotation axis, a sensor, and a processing unit. The sensor can be either a contact type or a non-contact type. On the outer circumferential surface of a cylindrical workpiece supported with its central axis aligned with the rotation axis Cc corresponding to the Z-direction, the sensor calculates the coordinates of a point P whose coordinates in a first direction orthogonal to the rotation axis Cc are either maximum or minimum. Furthermore, the sensor calculates the coordinates of a reference point Q, whose coordinates in the first direction D1 are known. The processing unit calculates the distance D2 between point P and reference point Q in the first direction based on the coordinates of point P and reference point Q. The processing unit also calculates the workpiece diameter R of the cylindrical workpiece based on the distances D1 and D2.

[0041] The following is a reference to the appendix. Figure 1 The embodiments of the workpiece diameter measurement method and machine tool according to the present invention will be described in more detail below. Furthermore, in each figure, to clarify the shape or features of each component of the machine tool, these dimensions are shown as relative dimensions, but are not necessarily represented at a physical scale. Additionally, the same reference numerals are used for the same component in each figure.

[0042] Figure 1 This is a front view showing an example of the structure of the machine tool according to this embodiment. Figure 2 It is Figure 1 A conceptual diagram of the machine tool's workpiece, spindle, and first and second tool holders as viewed from the Z-direction.

[0043] like Figure 1 , Figure 2As shown, the machine tool 100 includes a first spindle 110, each having a rotary axis, and a second spindle 120 positioned opposite the first spindle 110. The first spindle 110 and the second spindle 120 each have a chuck that holds one end and the other end of a cylindrical workpiece W along its central axis. Figure 2 In the diagram, the positions of the chucks on the first spindle 110 or the second spindle 120 are indicated by dashed lines. Each spindle rotates the workpiece W about its axis of rotation. This diagram shows a machine tool 100 equipped with a second spindle 120, but the machine tool may also have a tailstock instead of a second spindle. Above the workpiece W, a tool spindle 130 (first tool post) capable of three-dimensional movement in the XYZ directions is provided. Furthermore, below the workpiece W, a turret 140 (second tool post) is provided. That is, the machine tool 100 is a composite machining center having a turning function performed by a tool fixed to the turret 140 and a milling function performed by a rotating tool mounted on the tool spindle 130. A contact sensor 200 is mounted on the turret 140. The first spindle 110, the second spindle 120, the tool spindle 130, and the turret 140 are each mounted on a bed (not shown) on the floor.

[0044] The machine bed is equipped with a moving mechanism (guide rail, ball screw, etc.) for moving the turret 140 in the three directions of X, Y, and Z. The terminal 210 of the contact sensor 200 moves along the circumferential surface of the workpiece W by moving the turret 140 in the X and Y directions.

[0045] Figure 3 , Figure 4 This is a diagram showing the process of measuring the coordinates of a point P, whose coordinates are minimal in the X direction orthogonal to the axis of rotation Cc, on the outer circumference of a cylindrical workpiece W. Figure 3 In this context, the workpiece W has a smaller diameter than the circular chucks used to hold the workpiece, which are located on the first and second spindles 110 and 120. Figure 4 In the diagram, workpiece W is the larger diameter than the chuck.

[0046] The rotation axes of the first and second main spindles 110 and 120 are aligned with the central axis of the cylindrical workpiece W. Circle Cw is the circle drawn by the intersection of a plane perpendicular to the central axis of workpiece W and the outer circumferential surface of the workpiece. Circle Cz, represented by a dashed line, is the circle drawn by the intersection of a plane perpendicular to the rotation axis Cc and the outer circumferential surface of the chuck. Point P is a point on circle Cw, representing the lowest point of the workpiece with the smallest coordinate in the X direction. The contact sensor 200 moves along an arc with a central angle θ, passing over point P, and continuously detects the coordinates near point P. The detected coordinates are calculated as parameters by a predetermined arithmetic unit.

[0047] Reference points Q1 and Q2 are points on circle Cz. The distances D1 from the axis of rotation Cc to reference points Q1 and Q2 in the X and Y directions are known. Distances D1 remain almost unchanged under varying temperature and humidity conditions. The clamp diameter may vary slightly with temperature, but this variation is negligible. Furthermore, even if the clamp diameter changes significantly, the distance in the X direction between reference point Q2 and point P remains unchanged. When viewed from the Z direction, reference point Q1, point P, and the axis of rotation Cc are all on the same straight line.

[0048] First, the coordinates of reference point Q are detected by sensor 200, and the calculation unit calculates the parameters of the detected coordinates. Then, the coordinates of point P are detected, and the calculation unit calculates the parameters of the coordinates. Based on the calculated parameters, the calculation unit calculates the distance D2.

[0049] In addition, if the rotation axes of the first and second spindles 110 and 120 are not aligned with the Z direction due to the assembly precision of the machine tool, the deviation can be measured and reflected in the calculation of each distance in the calculation unit.

[0050] Next, in Figure 3 In this case, the workpiece diameter R1 of the cylindrical workpiece W is calculated by subtracting the distance D2 from the distance D1 using the calculation unit. Figure 4 In this case, the workpiece diameter R2 is calculated by adding distance D1 and distance D2 by the calculation unit.

[0051] Figure 5 This is a front view showing an example of the structure of a machine tool 100X according to another embodiment. In machine tool 100X, the sensor 200 is not mounted on the turret 140, but on the tool spindle 130. The sensor 200 is mounted on the tool spindle 130 by replacing the tool and sensor using an ATC (Automatic Tooling Control). Other structures are similar. Figure 1 The same applies to machine tool 100. In the case of machine tool 100X, point P can also be used to detect, for example, the point at the top of the workpiece where the coordinate in the X direction is extremely large.

[0052] The above description of the embodiments is illustrative in all respects and not restrictive. Those skilled in the art will be able to make appropriate modifications and alterations. The scope of the invention is defined not by the above-described embodiments but by the technical solutions. Furthermore, within the scope of the invention, modifications from the embodiments within the range equivalent to the technical solutions are included.

[0053] Industrial applicability

[0054] The workpiece diameter measurement method of the present invention is suitable for measuring the diameter or radius of cylindrical workpieces in machine tools such as lathes and multi-processing machines.

[0055] Label Explanation

[0056] 100, 100X: Machine tools

[0057] 110: First main shaft

[0058] 120: Second spindle

[0059] 130: Tool spindle

[0060] 140: Turning Tower

[0061] 200: Sensor

[0062] 210: Terminal

[0063] W: Workpiece

[0064] R1, R2: Workpiece diameter

[0065] P: Maximum or minimum point

[0066] Q: Benchmark point

[0067] Cc: Rotation shaft

[0068] Cw: The circle drawn by the intersection of the plane perpendicular to the central axis of the workpiece W and the outer circumference of the workpiece. Cz: The circle drawn by the intersection of the plane perpendicular to the axis of rotation Cc and the outer circumference of the clamp.

Claims

1. A method for measuring the diameter of a workpiece, characterized in that, have: In a process of measuring the coordinates of a point P on the outer circumference of a cylindrical workpiece supported in a manner where the central axis is aligned with the rotation axis of the machine tool spindle, a sensor is moved in a first direction and a second direction that are orthogonal to and mutually orthogonal to the aforementioned rotation axis, and the coordinates of the point P on which the change in the coordinates of the first direction relative to the coordinates of the second direction is extremely large or extremely small. The process of calculating the distance D1 from the aforementioned rotation axis in the first direction to a known reference point Q and the distance D2 from the aforementioned point P in the first direction; and The process of calculating the diameter of the cylindrical workpiece based on the distances D1 and D2 mentioned above.

2. The method for measuring the diameter of a workpiece as described in claim 1, characterized in that, When viewed from the Z direction corresponding to the aforementioned axis of rotation, the aforementioned reference point Q is on the same straight line as the aforementioned point P and the aforementioned axis of rotation.

3. The method for measuring the diameter of a workpiece as described in claim 1, characterized in that, The first direction mentioned above is either the vertical X direction or the horizontal Y direction.

4. The method for measuring the diameter of a workpiece as described in claim 3, characterized in that, The coordinates of point P are the minimum coordinates in the X direction.

5. The method for measuring the diameter of a workpiece as described in claim 3, characterized in that, The aforementioned sensor is mounted on a structure that is capable of moving in a plane orthogonal to the aforementioned axis of rotation.

6. The method for measuring the diameter of a workpiece as described in claim 5, characterized in that, The aforementioned structure is the first or second tool post of a multi-tool or lathe.

7. The method for measuring the diameter of a workpiece as described in any one of claims 1 to 6, characterized in that, The aforementioned reference point Q is located on the chuck of the aforementioned spindle that holds the aforementioned workpiece.

8. The method for measuring the diameter of a workpiece as described in any one of claims 1 to 6, characterized in that, The coordinates of point P are measured by moving the sensor along the intersection of a plane perpendicular to the central axis and the outer peripheral surface.

9. A machine tool, characterized in that, have: The main spindle has a rotating shaft; The sensor is capable of moving in a first direction and a second direction orthogonal to and mutually orthogonal to the aforementioned rotation axis. It calculates the coordinates of a point P on the outer circumferential surface of a cylindrical workpiece supported with its central axis aligned with the aforementioned rotation axis, where the change in coordinates in the first direction relative to the coordinates in the second direction is a maximum or minimum, and the coordinates of a reference point Q whose distance D1 in the first direction from the aforementioned rotation axis is known. The calculation unit calculates the distance D2 between point P and reference point Q in the first direction based on the coordinates of point P and reference point Q, and calculates the workpiece diameter of the cylindrical workpiece based on the distances D1 and D2.

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