JP2015039732A - Machine tool and work machining portion measuring method using machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely measure a machining portion of work due to a machining center by an inline, and prevent the deterioration of measurement precision.SOLUTION: After centering a contact piece 42 of a touch probe 40 installed to a main shaft 14 by using a master ring 33 of a jig 18, the contact piece 42 is contacted on an inner peripheral surface of the master ring 33, thereby measuring a coordinate position. On the basis of the coordinate position and a coordinate position at the time of centering, a distance from a center of the master ring 33 to the contact point is calculated, and measurement precision by the touch probe 40 is determined on the basis of the distance. When the measurement precision is in a predetermined level or more, the measurement of a machining portion of work W by the touch probe 40 is carried out.

Description

  The present invention relates to a machine tool and a workpiece machining unit measurement method using the machine tool.

  For example, a cylinder block of an engine is machined from multiple directions by a machine tool. As a machine tool for machining such a workpiece, for example, a machining center is known. The machining center includes a machining table that rotates a jig for holding a workpiece around a vertical axis, and a horizontal spindle on which a machining tool is mounted, and performs predetermined machining on the workpiece while automatically changing the tool according to a predetermined program. Do. The workpiece is arranged at a predetermined machining position in the machine coordinate system of the machining center for the machining, and is held by a jig so as not to move from the position. The machining center has an XYZ coordinate system in which the main axis direction is the Z-axis direction, the vertical direction is the Y-axis direction, and the direction perpendicular to the Z-axis and the Y-axis is the X-axis direction.

  In machining a workpiece by a machining center, in order to increase the machining accuracy, the coordinate position of the jig is measured with a touch probe, and the machining data is corrected according to the measured value. In that case, the reliability of the measurement value by the touch probe becomes a problem. For example, when the touch probe is bent, the obtained jig coordinate position cannot be measured with high accuracy, resulting in low workpiece machining accuracy.

  On the other hand, Patent Document 1 describes that measurement accuracy of a jig coordinate position by a touch probe is improved using a master ring and a tester (dial gauge) provided on a jig. It measures the coordinate position of the master ring by attaching a tester to the spindle, and then measures the coordinate position of the master ring by attaching a touch probe to the spindle. The position measurement value is corrected.

JP 2010-64181 A

  By the way, after processing a workpiece by a machine tool, in order to determine whether or not the processing is performed with a predetermined accuracy, the processing portion is measured with a touch probe. The reliability of the measurement value of the touch probe is important in the measurement using the touch probe.

  On the other hand, in the method of centering the touch probe with the tester described above, if the tester is misaligned with respect to the spindle center when the tester is mounted on the spindle, the measurement value of the touch probe is corrected. Becomes inaccurate. For example, when the tester is mounted on the main shaft with a collet chuck, the shaft centers are displaced due to a difference in the amount of movement of each collet claw. Further, the contact of the touch probe is generally spherical, but it gradually wears due to contact with the workpiece. When the contact is worn, for example, the hole diameter is measured when the hole diameter is larger than the actual diameter. As described above, when the contact of the touch probe has undergone aged deformation such as wear, the measurement accuracy of the processed portion is lowered.

  Therefore, the present invention makes it possible to accurately measure the dimensions of the workpiece processing part in-line, and prevents a decrease in the measurement accuracy.

  In order to solve the above problems, the present invention determines the measurement accuracy by a touch probe using a master ring provided on a jig, and measures the workpiece processing part when the measurement accuracy is a predetermined level or more. To do. This will be specifically described below.

The workpiece machining part measurement method presented here is a method of measuring the dimensions of a workpiece machining part held by a jig and machined by a machine tool with a touch probe attached to the spindle of the machine tool,
Movement of the main shaft when the axis of the main shaft is positioned at the center of the master ring provided in the jig and the main shaft is moved to bring the contact of the touch probe into contact with the inner peripheral surface of the master ring Calculating a displacement amount of the contact with respect to the axis of the spindle based on the distance;
A centering step of positioning the contact of the touch probe at the center of the master ring based on the displacement amount;
The contact point of the touch probe is brought into contact with the inner peripheral surface of the master ring to measure the coordinate position of the spindle, and based on the coordinate position and the coordinate position of the spindle when the centering is performed, Calculating the distance from the center of the master ring to the contact point, and determining the measurement accuracy by the touch probe based on the distance,
When the measurement accuracy is equal to or higher than a predetermined level, the contact of the touch probe is brought into contact with the processed part of the workpiece, and the dimension of the processed part is calculated.

Further, the machine tool presented here is used directly for carrying out the workpiece machining part measuring method,
A spindle for selectively mounting a touch probe having a contact at the tip and a processing tool;
A jig for holding the workpiece to be machined,
A master ring provided in the jig;
The spindle is positioned based on the moving distance of the spindle when the spindle is positioned at the center of the master ring, and the spindle is moved to bring the touch probe contact with the inner peripheral surface of the master ring. A positional deviation amount calculating means for calculating the positional deviation amount of the contact with respect to the axis of
Centering means for positioning the contact of the touch probe at the center of the master ring based on the displacement amount;
The contact point of the touch probe is brought into contact with the inner peripheral surface of the master ring to measure the coordinate position of the spindle, and based on the coordinate position and the coordinate position of the spindle when the centering is performed, A measurement accuracy determining means for calculating a distance from the center of the master ring to the contact point and determining a measurement accuracy by the touch probe based on the distance;
When the measurement accuracy is equal to or higher than a predetermined level, the contact portion of the touch probe is brought into contact with the processing portion of the workpiece, and processing portion measuring means for calculating the size of the processing portion is provided. To do.

  Hereinafter, more specifically, if the positional deviation of the contact of the touch probe with respect to the axis of the main shaft is corrected, the measurement accuracy of the workpiece processing portion by the touch probe is increased accordingly. However, when an aged deformation such as wear occurs in the contact itself of the touch probe, the amount of deformation is directly reflected in the measurement result, resulting in a measurement error.

  Therefore, in the present invention, after correcting (centering) the positional deviation of the contact of the touch probe with respect to the axis of the main shaft, the contact of the touch probe is brought into contact with the inner peripheral surface of the master ring, and the center of the master ring is removed. The distance to the contact point was calculated, and the measurement accuracy of the touch probe was determined based on this distance. That is, when the contact of the touch probe is deformed, the degree of deterioration of the touch probe is so-called self-diagnosis by utilizing the amount of deformation reflected in the distance.

  Then, when the measurement accuracy by the touch probe is equal to or higher than a predetermined level, the workpiece processing part is measured by the touch probe, so that the measurement accuracy can be kept high.

  In the workpiece machining portion measuring method, in the step of calculating the positional deviation amount, the axis of the main shaft is positioned at the center of the master ring, and the contact is orthogonal to the main shaft direction of the inner peripheral surface of the master ring. A displacement amount of the contact in the first direction is calculated based on a movement distance of the main shaft when contacting each of two points opposed to one direction, and the contact is moved to the position on the inner peripheral surface of the master ring. Calculating the amount of displacement of the contact in the second direction based on the distance traveled by the main shaft when contacting each of two points opposite to the main axis direction and the second direction orthogonal to the first direction. preferable. Thereby, it is possible to reliably calculate the amount of displacement of the contact of the touch probe with respect to the axis of the main shaft.

  According to the present invention, the displacement of the contact with respect to the spindle center is calculated by bringing the contact of the touch probe into contact with the inner peripheral surface of the master ring, and the touch with respect to the spindle axis is calculated based on the displacement. In addition to correcting the displacement of the probe contact, the touch probe contact is brought into contact with the inner peripheral surface of the master ring to calculate the distance from the center of the master ring to the contact point, and the touch based on this distance. After measuring the measurement accuracy with the probe, the workpiece processing part was measured with the touch probe, that is, the measurement was performed after diagnosing the degree of deterioration due to secular deformation of the contact. It is possible to accurately measure the dimensions of the workpiece processing part in-line, and to prevent the measurement accuracy from being lowered.

It is a perspective view which shows the outline of the machining center as a machine tool. It is a side view which shows the relationship between a touch probe and a master ring. It is a block diagram which shows the control system of a machining center. It is a control flow figure of measurement accuracy judgment of a touch probe, and work processing part measurement. It is an XY plan view showing the relationship between the axis Cs of the main shaft and the center Ct of the contact of the touch probe. It is XY top view explaining the centering of the X-axis direction of the contact of a touch probe. It is XY top view explaining the centering of the Y-axis direction of the contact of a touch probe. It is XY top view explaining the measurement of the distance from the center Cm of a master ring to the internal peripheral surface. It is sectional drawing explaining centering of the contact of a touch probe when measuring the internal diameter of a process hole. It is XY top view explaining the movement of the contact of a touch probe when measuring the internal diameter of a processing hole.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its application, or its use.

  FIG. 1 shows a machining center 10 as a machine tool according to the present invention. The machining center 10 has an XYZ coordinate system composed of X, Y, and Z axes as a machine coordinate system. The X axis and Z axis are in the horizontal direction, and the Y axis is in the vertical direction.

  The machining center 10 is mounted with a machining tool 12 such as a drill, an end mill, a milling cutter, etc., and is rotated around an axis Cs parallel to the Z axis, and the spindle 14 is moved in each direction of the X axis and the Y axis. A column 16 provided with a driving mechanism (each servo motor) to be driven, a processing table 20 on which a jig 18 that holds the workpiece W is placed, a rotating mechanism 22 that rotates the processing table 20 around an axis parallel to the Y axis, And a feed mechanism 24 that moves the rotation mechanism 22 in the Z-axis direction.

  The machining center 10 is a so-called numerically controlled machine tool, and is applied to the workpiece W according to machining program data (NC program data that defines the workpiece type, machining shape, machining center coordinates, tool selection, machining conditions, etc.) created in advance. Various processings are performed on it. Although not shown in FIG. 1, the machining center 10 includes an automatic tool changer (ATC) 58 as shown in FIG. The ATC 58 replaces the machining tool 12 mounted on the spindle 14 with a machining tool mounted on a tool magazine (not shown) or a touch probe described later according to the machining program data (according to the tool number of the machining program). Do.

  The jig 18 is an equaling jig in which a jig main body 31 stands upright on a base 30, and an opening 32 is formed in the jig main body 31. The jig 18 is provided with a plurality of clamping devices (not shown) that clamp the work on the jig body 31 and hold the position thereof. The jig main body 31 is provided with a cylindrical master ring 33. The base 30 of the jig 18 is fixed to the processing table 20 so that the center Cm of the master ring 33 is parallel to the Z-axis direction.

  Here, in the machining center 10, after the workpiece W is machined by the machining tool 12, the dimensions of the machined portion are measured to determine whether or not the intended machining has been performed.

  A touch probe 40 shown in FIG. 2 is used for measurement of the workpiece processing portion. The touch probe 40 includes a spherical contact 42 at the tip of the stylus 41, and transmits a trigger signal when the contact 42 contacts the master ring 33, the workpiece W, or the like to the controller 51 of the machining center 10. Upon receipt of the trigger signal, the controller 51 receives the coordinate position of the contact point (“coordinate position of the main shaft”) based on the position data measured by the drive mechanism of the main shaft 14 and the detection unit of each servo motor of the table feed mechanism 24. The same shall apply hereinafter).

  FIG. 3 shows a control system of the machining center 10. The controller 51 is constituted by a microcomputer, and includes a CPU 53, a ROM 53 for storing machining programs, control programs, etc., a RAM 54 for temporarily storing various data, an interface 55 for communication with the operation panel 56, and the like. Yes. The controller 51 receives an operation signal generated in response to an operation of the operation panel 56, a position signal from each of the servo motors of the drive mechanism 57 for moving the spindle, the rotation mechanism 22 and the feed mechanism 24 of the machining table 20, and the touch probe 40. The trigger signal is input to the spindle drive motor, the servo motors, the ATC 58, and the like.

  The control program is a program that realizes operations to be performed by various means for measuring the workpiece processing part by being read from the ROM 53 into the RAM 54 by the CPU 52 and executed. And, as means for measuring the dimensions of the workpiece machining part, the positional deviation amount calculating means for the contact 42 of the touch probe 40, the centering means for the contact 42, the measurement accuracy determining means by the touch probe 40, the workpiece machining Part measuring means and machining quality judgment means for the workpiece W are provided.

  The positional deviation amount calculating means positions the axis Cs of the main shaft 14 at the master ring center Cm, and then moves the main shaft 14 so that the contact 42 of the touch probe 40 attached to the main shaft 14 is moved to the inner periphery of the master ring 33. Based on the movement distance of the main shaft 14 when it is brought into contact with the surface 33a, the amount of displacement of the center Ct of the contact 42 with respect to the axis of the main shaft 14 is calculated.

  The centering means positions the center Ct of the contact 42 of the touch probe 40 at the center Cm of the master ring 33 or at the center Ch of the machining hole described later by moving the main shaft 14 based on the amount of displacement.

  The measurement accuracy determination means moves the main shaft 14 and brings the contact 42 of the touch probe 40 attached to the main shaft 14 into contact with the inner peripheral surface 33a of the master ring 33, and from the master ring center Cm to the contact point. Calculate the distance. And based on this distance, the measurement precision by the touch probe 40 is determined.

  When the measurement accuracy is equal to or higher than a predetermined level, the processing unit measuring unit brings the contact 42 of the touch probe 40 into contact with the processing unit of the workpiece W and calculates the size of the processing unit.

  The workpiece W machining quality determination means determines whether or not the workpiece machining portion dimensions obtained by the machining portion measurement means are within a preset allowable range.

  FIG. 4 shows a flow of workpiece processing unit measurement. The contents of each means will be specifically described with reference to this flow.

  After machining the workpiece W by the machining tool 12, first, in step S1, the machining tool 12 mounted on the spindle 14 is replaced with the touch probe 40 by the ATC 58.

  In subsequent steps S2 to S5, using the master ring 33 of the jig holding the processed workpiece W, the contact of the touch probe 40 with respect to the axis Cs of the main shaft 14 by the misalignment amount calculating means and the centering means. 42 is calculated and centered.

  FIG. 5 is a view of the main shaft 14 as viewed from the front, and shows a state in which the position of the center Ct of the contact 42 of the touch probe 40 is deviated from the axis Cs of the main shaft 14. The displacement may occur due to a difference in the amount of movement of the collet claw when the touch probe 40 is attached to the main shaft 14 with a collet chuck or due to permanent distortion (bending) of the stylus 41. Hereinafter, the calculation and centering of the positional deviation amount by the positional deviation amount calculating means and the centering means will be specifically described.

  In step S2, the amount of positional deviation in the X-axis direction of the contact 42 of the touch probe 40 is calculated. First, the axis Cs of the main shaft 14 is positioned at the master ring center Cm. From this state, as shown in FIG. 6, the main shaft 14 is moved in one of the X-axis directions (first direction orthogonal to the main shaft direction) to bring the contact 42 into contact with the inner peripheral surface 33a of the master ring. Based on the X coordinate of the contact point and the X coordinate when the axis Cs of the main shaft 14 is first positioned at the master ring center Cm, the movement distance L1 of the main shaft 14 is obtained. Subsequently, the main shaft 14 is moved to the other side in the X-axis direction to bring the contact 42 into contact with the inner surface 33a of the master ring. Based on the X coordinate of the contact point and the X coordinate when the axis Cs of the main shaft 14 is first positioned at the master ring center Cm, the movement distance L2 of the main shaft 14 is obtained.

  Based on the obtained movement distances L1 and L2, a positional deviation amount a = (L1−L2) / 2 in the X-axis direction of the contact 42 is calculated. This misalignment amount a is a line segment connecting two points opposite to each other in the X-axis direction of the inner surface 33a of the master ring from the position of the contact 42 when the axis Cs of the main shaft 14 is positioned at the master ring center Cm. Corresponds to the distance to the midpoint.

  In step S3, the spindle 14 is moved in the X-axis direction so that the center Ct of the contact 42 of the touch probe 40 is positioned on the vertical line AB passing through the master ring center Cm based on the positional deviation amount a ( X-axis alignment).

  In subsequent step S4, the amount of positional deviation in the Y-axis direction of the contact 42 of the touch probe 40 is calculated. As shown in FIG. 7, the main shaft 14 is moved in one of the Y-axis directions (second direction orthogonal to the main-axis direction and the X-axis direction) to bring the contact 42 into contact with the master ring inner peripheral surface 33a on the straight line AB. . The movement distance L3 is obtained based on the Y coordinate of the contact point and the Y coordinate when the centering in the X-axis direction is performed first. Subsequently, the main shaft 14 is moved to the other side in the Y-axis direction to bring the contact 42 into contact with the inner surface 33a of the master ring. The movement distance L4 is obtained based on the Y coordinate of the contact point and the Y coordinate when the centering in the X-axis direction is performed first.

  Based on the obtained moving distances L3 and L4, a positional deviation amount b = (L3−L4) / 2 in the Y-axis direction of the contact 42 is calculated. This positional deviation amount b corresponds to the distance from the centering position of the contactor 42 in the X-axis direction to the midpoint of the line segment connecting the two points facing the Y-axis direction of the master ring inner peripheral surface 33a.

  In subsequent step S5, based on the positional deviation amount b, the spindle 14 is positioned so that the center Ct of the contact 42 of the touch probe 40 is positioned on the horizontal line CD passing through the master ring center Cm, that is, the master ring center Cm. Is moved in the Y-axis direction (centering in the Y-axis direction).

  The centering in the X-axis direction may be performed after the centering in the Y-axis direction.

  Next, in step S6, using the contact 42 of the touch probe 40, the distance from the master ring center Cm to the master ring inner peripheral surface 33a is calculated.

As shown in FIG. 8, first, the coordinate position (X ₀ , Y ₀ ) when the centering of the contact 42 of the touch probe 40 is performed is obtained. Subsequently, the contactor 42 is moved away from the master ring center Cm in the X-axis direction and the Y-axis direction by moving the main shaft 14 in the X-axis direction and the Y-axis direction from the state where the contactor 42 is centered. The four contact points on the inner peripheral surface 33a of the master ring are brought into contact with each other, and the coordinate positions (X ₁ , Y ₁ ) to (X ₄ , Y ₄ ) of each contact point are obtained. Based on the coordinate position (X ₀ , Y ₀ ), the coordinate position (X ₁ , Y ₁ ) to (X ₄ , Y ₄ ) of each contact point, and the diameter of the contact 42, each contact point from the master ring center Cm. The distance to is calculated.

  The calculation of the distance from the center Cm to the four points is not limited to the X-axis direction and the Y-axis direction, and may be performed in other directions on the XY plane. It may be 3 points or 5 points or more.

  In step S6, based on the amount of displacement (a, b) of the contact 42 with respect to the axis Cs of the main shaft 14, the center Ct of the contact 42 is corrected to the master ring center Cm and positioned (centering). This corresponds to measuring the radius inside the master ring by moving the contact 42 from the state to contact the inner peripheral surface 33a of the master ring. Since the main shaft 14 is moved from the state where the contactor 42 is centered, the center Ct of the contactor 42 moves on a straight line passing through the master ring center Cm. Thereby, the distance from the master ring center Cm to the master ring inner peripheral surface 33a can be accurately measured.

  In subsequent step S7, the measurement accuracy by the touch probe 40 is determined based on the distance from the master ring center Cm to each contact point. Specifically, it is determined whether or not the difference between the maximum value and the minimum value of the distance from the master ring center Cm to each contact point is a predetermined value or less. When the difference in distance is not more than a predetermined value, the measurement accuracy by the touch probe 40 is not less than a predetermined level.

  Whether the distance from the master ring center Cm to each contact point is within a predetermined range by utilizing the fact that the inner radius of the master ring 33 is known instead of the difference between the maximum value and the minimum value. You may make it determine whether the said measurement precision is more than a predetermined level.

  If it is determined in step S7 that the measurement accuracy is equal to or higher than the predetermined level, the process proceeds to step S8, and the touch probe 40 calculates the dimensions of the processed portion of the workpiece W.

  When it is determined in step S7 that the measurement accuracy has not reached the predetermined level, the process proceeds to step S9, the touch probe 40 is replaced, the displacement amount is calculated and centered for the replaced touch probe 40, and the distance Calculation and determination of measurement accuracy (steps S2 to S7) are executed.

  In step S8, for example, when calculating the inner diameter of the machining hole 61 of the workpiece W as shown in FIG. 9, first, the axis of the spindle is positioned at the center Ch of the machining hole 61. Then, the contact 42 of the touch probe 40 is centered by moving the main shaft 14 based on the positional deviation amounts a and b. That is, the center Ct of the contactor 42 is positioned at the center Ch of the processing hole 61. In this state, the main shaft 14 is advanced in the Z-axis direction so that the contact 42 of the touch probe 40 enters the machining hole 61. Next, by moving the main shaft 14 in the X-axis direction and the Y-axis direction, the contact 42 of the touch probe 40 is brought into contact with each of the four points A to D on the inner surface of the processing hole 61 as shown in FIG. Measure the coordinate position of the point. Based on the obtained coordinate position and the diameter of the contact 42, the inner diameters AB and CD of the processed hole 61 are calculated.

  Since the main shaft 14 is moved from the state where the contact 42 is centered, the center Ct of the contact 42 moves on a straight line passing through the center Ch of the machining hole 61. Thereby, the internal diameter of the processing hole 61 can be measured accurately.

  In step S10 following step S8, it is determined whether or not the dimension of the processed part calculated in step S8 is within an allowable range, that is, whether there is a processing defect. When there is a processing defect, the process proceeds to step S11 to perform additional machining of the processing part and other processing defect processing.

  In addition, regarding the measurement of the process part of the workpiece | work W, you may measure not only the measurement of the said hole diameter but the internal diameter and outer diameter of various recessed parts and convex parts, such as a boss | hub and a ring groove.

10 Machining center (machine tool)
12 Processing Tool 14 Spindle 18 Jig 33 Master Ring 40 Touch Probe 42 Contact 61 Processing Hole W Work Cs Spindle Center Cm Master Ring Center Ct Contact Center Ch Ch Center of Processing Hole

Claims (3)

A method of measuring a dimension of a workpiece processed by a machine tool held by a jig with a touch probe attached to a spindle of the machine tool,
Movement of the main shaft when the axis of the main shaft is positioned at the center of the master ring provided in the jig and the main shaft is moved to bring the contact of the touch probe into contact with the inner peripheral surface of the master ring Calculating a displacement amount of the contact with respect to the axis of the spindle based on the distance;
A centering step of positioning the contact of the touch probe at the center of the master ring based on the displacement amount;
The contact point of the touch probe is brought into contact with the inner peripheral surface of the master ring to measure the coordinate position of the spindle, and based on the coordinate position and the coordinate position of the spindle when the centering is performed, Calculating the distance from the center of the master ring to the contact point, and determining the measurement accuracy by the touch probe based on the distance,
A workpiece machining part measuring method, wherein when the measurement accuracy is equal to or higher than a predetermined level, the contact of the touch probe is brought into contact with the machining part of the workpiece and the dimension of the machining part is calculated. In claim 1,
In the step of calculating the positional deviation amount, the axis of the main shaft is positioned at the center of the master ring, and the contact is opposed to a first direction orthogonal to the main shaft direction of the inner surface of the master ring. The amount of displacement of the contact in the first direction is calculated based on the movement distance of the main shaft when it is brought into contact with the main shaft, and the contact direction of the main ring on the inner peripheral surface of the master ring and the first direction are calculated. A workpiece machining part measuring method, comprising: calculating a displacement amount of the contact in the second direction based on a moving distance of the main shaft when contacting each of two points opposed to a second direction orthogonal to each other . A spindle for selectively mounting a touch probe having a contact at the tip and a processing tool;
A jig for holding the workpiece to be machined,
A master ring provided in the jig;
The spindle is positioned based on the moving distance of the spindle when the spindle is positioned at the center of the master ring, and the spindle is moved to bring the touch probe contact with the inner peripheral surface of the master ring. A positional deviation amount calculating means for calculating the positional deviation amount of the contact with respect to the axis of
Centering means for positioning the contact of the touch probe at the center of the master ring based on the displacement amount;
The contact point of the touch probe is brought into contact with the inner peripheral surface of the master ring to measure the coordinate position of the spindle, and based on the coordinate position and the coordinate position of the spindle when the centering is performed, A measurement accuracy determining means for calculating a distance from the center of the master ring to the contact point and determining a measurement accuracy by the touch probe based on the distance;
When the measurement accuracy is equal to or higher than a predetermined level, the contact portion of the touch probe is brought into contact with the processing portion of the workpiece, and processing portion measuring means for calculating the size of the processing portion is provided. Machine tool to do.

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