CN112247670B - Single-axis measurement type measuring head and measurement method thereof - Google Patents
Single-axis measurement type measuring head and measurement method thereof Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
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Abstract
The invention relates to a single-axis measurement type measuring head and a method thereof, wherein the measuring head comprises a shell, a sensor, a measuring rod, a deflection measuring mechanism and a laser line indicating device; the upper end of the shell is provided with a mounting handle; the sensor and the deflection measuring mechanism are positioned in the shell, the upper end of the measuring rod is positioned in the shell, the lower end of the measuring rod downwards extends out of the shell and is provided with a measuring ball which is in contact with a workpiece, and the upper end of the measuring rod is connected with the movable grid of the sensor through the deflection measuring mechanism and drives the movable grid of the sensor to synchronously swing left and right relative to the static grid of the sensor; the laser line indicating device is fixed on the shell, the direction of the downward emitted laser line is consistent with the measurement deflection direction of the measuring rod, and the laser line indicating device is used for correcting the measurement direction when the shell is mounted on a machine tool and indicating the measurement direction when in measurement. The deflection measurement of the original measuring rod in two-dimensional and three-dimensional directions is limited to the unidirectional deflection measurement of the center position of the main shaft of the machine tool, and the deflection measurement is ensured by a laser guiding technology, so that the measurement precision can meet the requirement.
Description
Technical Field
The invention relates to the technical field of advanced measurement and detection, in particular to a single-axis measurement type measuring head and a measurement method thereof.
Background
Currently, two main techniques exist in the measurement technology of machine tool machining production, namely offline measurement, such as measurement of machined parts by a universal measuring tool or a three-coordinate measuring machine; such conventional manual and off-line measurements cannot effectively combine machining and inspection due to the problems of long time consumption, need for secondary positioning, etc., and have failed to meet the increasing inspection requirements. And secondly, on-machine detection, namely, on-machine detection, which means that a measuring head and a special software module are integrated on a numerical control machine tool to realize the functions of automatic positioning, quality evaluation and the like of a workpiece. The measuring mode can greatly save processing auxiliary time, reduce the rejection rate of workpieces and has important significance for enterprise production.
The machine tool measuring head is a key component of the whole on-machine detection system, and the precision of the machine tool measuring head greatly influences the precision of the whole measurement system. Internationally, represented by Renishaw, england, which developed the first machine tool probe at the hannover european machine tool exhibition in 1977, had profound effects. The company applies for patent name "contact sensing head" in China, patent application number is: CN86105617. The institute of japan corporation's Sanfeng also filed a patent in china, entitled "contact signal probe", wherein the national patent application number is CN85107033. Other metering companies have been made available, such as MIDA series probes from Marpos, italy, and related companies such as m & h, blum, germany. In China, the Harbin pioneer mechanical and electrical limited company applies for a patent for the measuring head of the company, and the patent name is a trigger type three-dimensional measuring head, and the application number is 201020044796.8; the patent application number of the numerical control machine tool on-machine detection head and detection system is 201110303424.1.
For the measuring head of the machine tool, the main function is to accurately judge the contact time of the measuring needle and the surface of the workpiece to be measured, and inform the numerical control machine tool to latch the coordinates of the spindle at the moment in time. Through the analysis to the contact gauge head product of current lathe, its theory of operation is as follows: a closed active circuit is arranged in the measuring head and is connected with a trigger mechanism, so that the trigger mechanism can cause the state change of the circuit and send out a signal to indicate the working state of the measuring head as long as the trigger mechanism generates trigger action; the only condition of the trigger mechanism for generating the trigger action is that the probe of the probe generates tiny swing or moves towards the inside of the probe, when the probe is connected to the main shaft of the machine tool and moves along with the main shaft, the probe on the probe only contacts with the surface of the workpiece in any direction, so that the probe generates tiny swing or moves, the trigger is formed, and the trigger signal is a switch signal.
In the actual use process, the trigger type measuring head has certain defects. Firstly, the measurement efficiency is low, in the machine detection process, when the top end of the measuring head sends out a trigger signal to be transmitted to the numerical control system, the numerical control system processes the trigger signal as an interrupt with higher priority, the time from the scanning of the numerical control system to the complete stopping of the movement of the main shaft of the machine tool is assumed to be t, at the moment, the main shaft feeding speed of the machine tool is v, and the movement stroke L=v×t. L is also the error that needs to be compensated for in post-processing. For the current trigger type measuring head, in order to ensure accuracy, the reserved safety travel in the middle is often smaller, and when L reaches a certain value, the measuring head is crashed. Therefore, the feeding speed of the trigger type measuring head used in the machine detection at present is often lower in the measuring process. The measurement efficiency is seriously affected. Second, measurement errors are difficult to compensate. The pre-stroke error of the contact type measuring head is unavoidable, and the error is the displacement from the contact of the measuring ball to the surface of the workpiece to the moment when the measuring head sends a trigger signal, and can also be expressed as the sum of elastic deformation generated by the measuring rod for overcoming the pre-tightening force of the existing spring and each part of the measuring head, and due to different materials and different structures, the error irregularity can be caused. It is currently common practice to calibrate it using standard ball tests. Only this error can be reduced but cannot be eliminated.
In general, in the contact signal probe technique, a contact device is installed at three points of a contact probe supporting portion, so that measurement depends on the direction of an axis, and thus, stable measurement cannot be performed in all directions, and such directional errors cannot be corrected in the prior art. Unlike the contact probes described above, there has been a probe that can electrically measure the angular position or displacement of a contact pin using a differential transformer. Of course, such differential transformer type probes do not have good detection sensitivity. In particular, the detection sensitivity of the probe has directivity to the movement of the contact probe.
According to the description, two measurement types are known for the machine tool measuring head, one measurement type is a trigger type measuring head, the main function of the measurement head is to accurately judge the contact time of a measuring needle and the surface of a workpiece to be measured, inform a numerical control machine tool to latch the coordinate of a main shaft at the moment in time, support of a numerical control system is needed, and the defects of low measurement efficiency, difficulty in compensation of measurement errors and the like are overcome. The other is a measuring type measuring head, which is used for measuring the angular position or displacement of a contact measuring needle through a sensing measurement technology, so as to obtain the deflection angle quantity or the moving distance quantity of the measuring needle, and the measuring head can be separated from a machine tool operating system to independently finish the measurement, and the measuring head has the defect of being lack of an electric measuring head which can perform omnidirectional detection and has high resolution and high precision, and a sensing method and technology.
Disclosure of Invention
In summary, in order to solve the defects of the prior art, the technical problem to be solved by the present invention is to provide a single-axis measurement type measuring head and a measurement method thereof, which adopts the measurement type measuring head technology to get rid of the dependence of the trigger type measuring head on a numerical control system, reduce the cost barrier of popularization and use, and simultaneously avoid the inherent technical defects of the trigger type measuring head. As shown in fig. 7 and 8, the measuring point of the measuring ball is marked as a zero point position when being positioned on the central line of the main shaft of the machine tool, and the deviation distance between the measuring point of the measuring ball and the central line of the main shaft of the machine tool is measured through the angle value of the sensor when the measuring point of the measuring ball is measured on the measuring rod, so that the actual distance data from the measuring point of the measuring ball to the central line of the main shaft of the machine tool is obtained. And combining the test use scene, converting the machine tool machining correction parameters, such as the machine tool shafting gap deviation value or the cutter radial deviation value, workpiece positioning position information and other parameters related to machine tool control and correction, correcting the program end before machining, so that the machined part can meet the requirements.
The technical scheme for solving the technical problems is as follows: a single-axis measurement type measuring head comprises a shell, a sensor, a deflection measurement mechanism, a measuring rod and a laser line indicating device; the shell is arranged on the machine tool; the sensor is positioned in the shell, and the deflection measuring mechanism is positioned in the shell and corresponds to a position below the sensor; the upper end of the measuring rod is positioned in the shell, the lower end of the measuring rod extends downwards to the outside of the shell and is provided with a measuring ball which is in contact with a workpiece, and the upper end of the measuring rod is connected with the movable grid of the sensor through the deflection measuring mechanism and drives the movable grid of the sensor to synchronously swing left and right relative to the static grid of the sensor so as to realize measurement; the laser line indicating device is fixed on the shell, the direction of the downward emitted laser line is consistent with the deflection measuring direction of the measuring rod, and the laser line indicating device is used for correcting the measuring direction when the shell is mounted on a machine tool and indicating the measuring direction when in measurement.
The beneficial effects of the invention are as follows: the deflection measurement of the original measuring rod in two-dimensional and three-dimensional directions is limited to single-direction deflection measurement relative to the central position of the main shaft of the machine tool by adopting a dimension reduction processing mode, and the measurement precision can be ensured by adopting a laser guiding technology. In the measuring process, the laser can also be used for indicating the advancing measuring direction of the machine tool spindle, so that the phenomenon that the advancing direction of the machine tool spindle is inconsistent with the deflection direction of the measuring rod to cause firing pins is avoided.
Based on the technical scheme, the invention can also be improved as follows:
Further, the deflection measuring mechanism comprises a reset sleeve, a reset spring, a swing rod and a reset cylinder; the reset sleeve is fixed in the shell and corresponds to a position below the sensor, and the reset spring is positioned at the top in the reset sleeve; the swing rod is arranged in the reset sleeve in a swinging way towards the left side and the right side of the shell, the upper end of the swing rod freely penetrates through the reset spring and then extends out of the upper part of the reset sleeve, the swing rod is finally fixedly connected with the movable gate of the sensor, and the lower end of the swing rod extends out of the lower part of the reset sleeve and is fixedly connected with the upper end of the measuring rod; the middle part of pendulum rod is equipped with a shoulder structure, the section of thick bamboo suit that resets is in outside the pendulum rod and correspond shoulder structure with return spring is between, and return spring's upper and lower both ends are supported respectively reset cover top inner wall with the upper end of section of thick bamboo resets, and then make the lower extreme of section of thick bamboo resets is in shoulder structure's up end is in order to guarantee return spring is in the measuring staff provides reset force when the yaw measurement left or right.
Further, the deflection measuring mechanism also comprises a rotary cylinder and two bearings; the front and rear ends of the rotary cylinder extend out of the front and rear sides of the swing rod respectively; the inner rings of the two bearings are respectively fixed on the front end and the rear end of the rotary cylinder, and the outer rings of the two bearings are respectively fixed on the corresponding positions on the inner wall of the front side or the rear side of the reset sleeve.
The beneficial effects of adopting the further technical scheme are as follows: two-way measurement of left swing or right swing is considered; the hysteresis error of swing is effectively reduced, friction is reduced, sensitivity is improved, a rotation gap is eliminated, and measurement precision and reliability are improved.
Further, a mounting handle is fixed on the top of the housing and is used for connecting with a spindle of a machine tool, and the axis line of the mounting handle passes through the center of the rotary cylinder.
Further, the wireless transmitter is also included; the wireless transmitter is arranged in the shell and is electrically connected with the sensor, measurement data of the sensor are transmitted to the external terminal display unit in a wireless mode, and the terminal display unit runs corresponding application programs and processes and displays the measurement data according to requirements.
The measuring method of the single-axis measuring type measuring head comprises the following steps:
The sensor is an absolute angle sensor, an absolute angle position value A corresponding to the measurement contact point of the measuring ball when the measurement contact point of the measuring ball is positioned on the central line of the main shaft of the machine tool is calibrated to be a zero reference value, and the relative zero deflection angle of the center of the measuring ball is alpha; and during measurement, calculating the offset L between a measurement contact and the center of the main shaft of the machine tool according to the position of the spherical measuring point of the measuring ball and a trigonometric function relation through the swing radius H of the measuring ball, the zero reference value A and the relative zero deflection angle alpha of the center of the measuring ball.
Further, the swing radius H of the ball is calibrated by:
Under the drive of machine tool feeding, the measuring ball of the measuring rod contacts with the corresponding position of the reference block, the measuring rod swings leftwards or rightwards along the direction of the laser line emitted by the laser line indicating device, after the measuring rod swings, the movable grid of the sensor is driven by the swing measuring mechanism to swing synchronously relative to the static grid so as to measure the swing angle alpha, the travelling path S relative to the machine tool spindle is read by the machine tool measuring system, and finally the swing radius H of the measuring ball is calibrated according to the following formula through the alpha and the S: h=s/α/pi.
Further, calibrating a zero reference value when a measuring contact of the measuring ball is positioned on the center line of a main shaft of the machine tool by the following method:
Under the drive of machine tool feeding, the measuring ball of the measuring rod firstly contacts one side of the calibration point, the measuring rod swings leftwards or rightwards along the direction of the laser line emitted by the laser line indicating device, and after the measuring rod swings, the movable grid of the sensor is driven by the swing measuring mechanism to swing synchronously relative to the static grid, and the absolute value of the swing angle is A; then controlling a main shaft of a machine tool to rotate, driving a measuring ball of the measuring rod to contact the other side of the calibration point, enabling the measuring rod to swing leftwards or rightwards along the direction of the laser line emitted by the laser line indicating device, and after the measuring rod swings, driving a movable grid of the sensor to synchronously swing relative to a static grid through the deflection measuring mechanism, and outputting the absolute value of the deflection angle to be A 1'; and calculating a zero reference value A 0：A0=（A1+A1 ')/2 when the measuring contact point of the measuring ball is positioned on the center line of the main shaft of the machine tool according to A 1 and A 1'.
Further, the deflection angle alpha 0 of the spherical center of the measuring sphere relative to the zero reference is calculated according to the following formula:
α 0 =asin (d/2/H), d being the diameter of the sphere.
Further, during measurement, the offset L between the measuring contact and the center of the spindle of the machine tool is calculated according to the trigonometric function relation between H, A 0 and alpha 0 and according to the spherical contact position of the measuring ball in the following way:
Under the drive of machine tool feeding, the measuring ball of the measuring rod contacts with a workpiece, and the measuring rod deflects leftwards or rightwards along the laser line direction emitted by the laser line indicating device, after the measuring rod deflects, the movable grid of the sensor is driven by the deflection measuring mechanism to synchronously swing relative to the static grid, and the absolute value of the deflection angle is A 3; according to A 3 and A 0, calculating an angle offset alpha=A 3-A0 between the measuring contact and the center of the main shaft of the machine tool, and finally calculating the offset between the measuring contact and the center of the main shaft of the machine tool through H, alpha and alpha 0: l=h (SIN (α+α 0)-sinα0).
The measuring method has the beneficial effects that: in the existing measurement, the sphere center of the measuring sphere is generally used as a reference, and as more deviation values between a measuring contact and the center of the main shaft are obtained in the measurement, calculation for detecting the radius of the measuring sphere is needed, so that the radius precision error and the measuring precision error of the sensor are introduced. According to the measuring method, the sphere of the measuring ball/the measuring contact point is used as a reference to calibrate the zero point for calculation and measurement, the accuracy of the radius of the measuring ball and the influence of the accuracy of the sensor are reduced, and the measuring accuracy is further improved.
Drawings
FIG. 1 is a block diagram of the present invention in a free state;
FIG. 2 is a block diagram of the present invention in the zero position;
FIG. 3 is a schematic illustration of a measurement when the swing direction of the stylus is not parallel to the x-axis or y-axis direction in the machine tool measurement system;
FIG. 4 is a first block diagram of a yaw measurement mechanism;
FIG. 5 is a second block diagram of a yaw measurement mechanism;
FIG. 6 is a schematic illustration of a staff calibration;
FIG. 7 is a schematic illustration of a nominal zero position;
FIG. 8 is a schematic diagram of measurement of the left deflection of the stylus;
fig. 9 is a schematic diagram of measurement when the measuring staff swings right.
In the drawings, the list of components represented by the various numbers is as follows:
1. The device comprises a shell, 2, a measuring rod, 3, a laser line indicating device, 4, a measuring ball, 5, a movable grid, 6, a static grid, 7, a laser line, 8, a reset sleeve, 9, a reset spring, 10, a swing rod, 11, a reset cylinder, 12, a bearing, 13, a mounting handle, 14, a calibration point, 15, a workpiece, 16 and a wireless transmitter.
Detailed Description
The principles and features of the present invention are described below with reference to the drawings, the examples are illustrated for the purpose of illustrating the invention and are not to be construed as limiting the scope of the invention.
As shown in fig. 1 and 2, a single axis measuring probe includes a housing 1, a sensor, a stylus 2, and a laser line indicating device 3. The housing 1 is mounted on a spindle of a machine tool or other parts of the machine tool, specifically as follows: the probe further comprises a mounting shank 13, said mounting shank 13 being fixed vertically upwards on top of said housing 1 and being intended for connection to a spindle of a machine tool or other component of the machine tool. The sensor is positioned in the shell 1, and the deflection measuring mechanism is positioned in the shell 1 and corresponds to a position below the sensor. The upper end of the measuring rod 2 is positioned in the shell 1, the lower end of the measuring rod extends downwards to the outside of the shell 1 and is provided with a measuring ball 4 which is in contact with a workpiece, the upper end of the measuring rod 2 is connected with a movable grid 5 of the sensor through a deflection measuring mechanism, and the movable grid 5 of the sensor is driven to synchronously swing left and right relative to a static grid 6 of the sensor so as to realize measurement. The laser line indicating device 3 is fixed on the housing 1, and the direction of the downward-emitted laser line 7 is consistent with the measurement deflection direction of the measuring rod 2, and is used for correcting the measurement direction when the housing 1 is mounted on a machine tool and indicating the measurement direction when in measurement. The yaw direction of the stylus 2 is indicated by a laser line 7 during the mounting of the housing 1 on the spindle of a machine tool to be parallel to the x-axis or y-axis direction in the machine tool measurement system. The laser line indicating device 3 is arranged on the shell 1, and the product ensures that the laser line 7 emitted by the laser line indicating device 3 is parallel to the deflection direction of the measuring rod 2 before leaving the factory, so that when the measuring head is arranged on a main shaft of a machine tool, the swinging direction of the measuring rod 2 can be parallel to the direction of the x axis or the y axis in the measuring system of the machine tool as long as the laser line 7 emitted by the laser line indicating device 3 is parallel to the direction of the x axis or the y axis in the measuring system of the machine tool. As shown in fig. 3, if the swing direction of the measuring rod 2 forms an angle θ with the direction of the x axis or the y axis in the machine tool measurement system, the actual distance l=l 0 ×cos θ, where L 0 is the detection distance of the measuring rod 2, by adopting the dimension-reducing processing method in the above manner, the deflection measurement of the original measuring rod in the two-dimensional and three-dimensional directions is limited to the single-direction deflection measurement relative to the center position of the spindle of the machine tool, that is, the swing direction of the measuring rod 2 is limited to be parallel to the direction of the x axis or the y axis in the machine tool measurement system, and the laser guiding technology is used to ensure that the actual distance l=the detection distance L 0, so that the measurement accuracy can meet the requirement. The measuring head further comprises a wireless transmitter 16, wherein the wireless transmitter 16 is arranged in the shell 1 and is electrically connected with the sensor, measurement data of the sensor are transmitted to an external terminal display unit, and the terminal display unit runs corresponding application programs and processes and displays the measurement data as required.
Preferably, as shown in fig. 4 and 5, the deflection measuring mechanism comprises a reset sleeve 8, a reset spring 9, a swing rod 10 and a reset cylinder 11. The reset sleeve 8 is fixed in the shell 1 at a position corresponding to the position below the sensor, and the reset spring 9 is arranged at the top of the reset sleeve 8. The swing rod 10 is installed in the reset sleeve 8 towards the left side and the right side of the shell 1 in a swinging way, the upper end of the swing rod 10 freely penetrates through the reset spring 9 and then extends out of the upper portion of the reset sleeve 8, the swing rod is finally fixedly connected with the movable grid 5 of the sensor, and the lower end of the swing rod 10 extends out of the lower portion of the reset sleeve 8 and is fixedly connected with the upper end of the measuring rod 2. The middle part of pendulum rod 10 is equipped with a shoulder structure, reset cylinder 11 suit is in outside pendulum rod 10 and correspond shoulder structure with between reset spring 9, and reset spring 9's upper and lower both ends are supported respectively reset sleeve 8 top inner wall with reset cylinder 11's upper end, reset spring 9 is compressed state promptly, and then makes under reset spring 9's effect reset cylinder 11's lower extreme is pressed on the shoulder structure, guarantee reset spring 9 is in measuring staff 2 left or right deflection all provides the restoring force. The deflection measuring mechanism further comprises a rotating cylinder and two bearings 12. The rotary cylinder is horizontally fixed in the middle of the swing rod 10, the front end and the rear end of the rotary cylinder extend out of the front side and the rear side of the swing rod 10 respectively, and the axial lead line of the mounting handle 13 passes through the center of the rotary cylinder. The inner rings of the two bearings 12 are respectively fixed on the front end and the rear end of the rotary cylinder, and the outer rings of the two bearings are respectively fixed on the corresponding positions on the inner wall of the front side or the rear side of the reset sleeve 8. The swing support of the measuring rod 2 is a structure of a bearing 12 and a rotary cylinder, so that the swing hysteresis error can be effectively reduced, friction is reduced, the sensitivity is improved, and the reset spring 9 which is axially arranged can still keep reset force when not measuring the left and right deflection function of the measuring rod 2, eliminate the rotary gap and improve the measurement precision and reliability.
The measuring method of the measuring head comprises the following steps:
The sensor is an absolute angle sensor, an absolute angle position value A 0 corresponding to the measurement contact point of the measuring ball 4 when the measurement contact point is positioned on the central line of the main shaft of the machine tool is calibrated to be a zero reference value, and the relative zero deflection angle of the spherical center of the measuring ball 4 is alpha 0. During measurement, the measurement contact and the central offset L of the machine tool spindle are calculated according to the position of the spherical measuring point of the measuring ball 4 and the trigonometric function relation through the swing radius H of the measuring ball 4, the zero reference value A 0 and the relative zero deflection angle alpha 0 of the spherical center of the measuring ball 4. The method comprises the following steps:
The swing radius H of the ball 4 is calibrated by: as shown in fig. 6, under the drive of the feeding of the machine tool, the ball 4 of the measuring rod 2 contacts the corresponding position of the reference block, and deflects the measuring rod 2 leftwards or rightwards along the direction of the laser line indicating device 3 emitting the laser line 7, after the deflection of the measuring rod 2, the movable grid 5 of the sensor is driven by the deflection measuring mechanism to synchronously swing relative to the static grid 6 so as to measure the deflection angle alpha 1, the travelling path S relative to the main shaft of the machine tool is read by the measuring system of the machine tool, and finally the swinging radius H of the ball 4 is calibrated according to the following formula through alpha 1 and S: h=s/α 1 x 180/pi.
Calibrating a zero reference value when a measuring contact of the measuring ball 4 is positioned on the center line of a main shaft of a machine tool by the following method: as shown in fig. 7, under the drive of the machine tool, the ball 4 of the measuring rod 2 contacts one side of the calibration point 14 (the calibration point 14 is located on the reference block/standard block), the measuring rod 2 swings leftwards or rightwards along the direction of the laser line indicating device 3 emitting the laser line 7, and after the measuring rod 2 swings, the swing measuring mechanism drives the movable grid 5 of the sensor to swing synchronously relative to the static grid 6, and the absolute value of the swing angle is a 1 or a 2. Then the main shaft of the machine tool is controlled to rotate 180 degrees, and then the measuring ball 4 of the measuring rod 2 is driven to contact the other side of the calibration point 14, so that the measuring rod 2 swings leftwards or rightwards along the direction of the laser line indicating device 3 emitting the laser line 7, and after the measuring rod 2 swings, the movable grid 5 of the sensor is driven to synchronously swing relative to the static grid 6 through the swing measuring mechanism, and the absolute value of the swing angle is A 1' or A 2′. The zero reference value A 0：A0=（A1+A1 ')/2 when the measuring contact point of the measuring ball 4 is positioned on the center line of the main shaft of the machine tool is calculated according to A 1 and A 1' or A 2 and A 2′. And calculating the deflection angle alpha 0 of the sphere center of the measuring sphere 4 relative to a zero reference according to the following formula:
α 0 =asin (d/2/H), d being the diameter of the ball 4. In the conventional measurement, the center of the ball 4 is generally used as a reference, and the deviation value between the spherical surface and the center of the spindle is sometimes used in the measurement, so that the calculation for detecting the radius of the ball 4 is needed, and the radius precision error is introduced. According to the invention, the sphere/measuring contact of the measuring ball 4 is used as a reference to calibrate the zero point for calculation and measurement, so that the influence of the radius of the measuring ball 4 is reduced, and the measurement accuracy is further improved.
During measurement, the offset L of the measuring contact point and the center of the machine tool spindle is calculated according to the trigonometric function relation between H, A 0 and alpha 0 and according to the spherical contact point position of the measuring ball 4 in the following way: as shown in fig. 8 and 9, under the drive of the feeding of the machine tool, the measuring ball 4 of the measuring rod 2 contacts the workpiece 15, and makes the measuring rod 2 swing leftwards or rightwards along the direction of the laser line 7 emitted by the laser line indicating device 3, after the measuring rod 2 swings, the movable grid 5 of the sensor is driven by the swing measuring mechanism to swing synchronously relative to the static grid 6, and the absolute value of the swing angle is a 3; according to A 3 and A 0, calculating an angle offset alpha=A 3-A0 between the measuring contact and the center of the main shaft of the machine tool, and finally calculating the offset between the measuring contact and the center of the main shaft of the machine tool through H, alpha and alpha 0: L=H (SIN (alpha+alpha 0)-sinα0)) can be measured in a smaller range (for example, the swing included angle of the diameter d of the measuring ball 4 is smaller than + -half), the diameter deviation of the measuring ball 4 and the deviation of the rotation center of the measuring rod 2 and the center line of the main shaft have little influence on the measurement precision, and the influence of principle errors of the lever type instrument calculated by arc length approximation can be avoided, the measurement range is greatly increased compared with that of the lever type instrument, and the accuracy of the lever type instrument can reach + -3.0 mm.
For the original defects of the measuring type measuring head, such as the problem of insufficient measuring resolution, a high-resolution sensor is found, and the problem is solved by adopting the technology of patent application number 201810365459. X. The invention adopts dimension reduction processing mode to limit the original two-dimensional and three-dimensional measurement to unidirectional measurement, and ensures the measurement accuracy by laser guiding technology, thus meeting the requirement. The influence of the reduction of the use range caused by dimension reduction is replaced by developing a new use mode of the measuring head, and the method is concretely as follows:
(1) The function of the edge finder (middle rod) is realized, the original point position of the workpiece coordinate system is set by an operator, and the original point position is usually determined by tool setting after the workpiece is clamped, and reflects the distance position relationship between the workpiece and the zero point of the machine tool. The measurement result reflects the position difference between the measured surface and the center of the main shaft of the machine tool, if the measured surface is in the same line with the center of the main shaft, the difference is zero, and the coordinate value of the machine tool in the measurement direction is the coordinate value of the working coordinate in the direction and the zero point of the machine tool; and setting the position value to zero to calibrate the origin of the shafting working coordinate system. And reading the difference value of the coordinate values corresponding to the center line of the main shaft of the two measuring surfaces during measurement, and obtaining the position data in the measuring surface part by taking half of the difference value. Because the measuring head has a data measuring function, and is combined with the coordinate position moving data of the machine tool, the coordinate of the machine tool is not required to be strictly ensured to move to the target position in the measuring process, and only the overshoot or the difference value generated in the overshoot or the difference value is subtracted or added in the acquired data, so that the measuring head is more convenient to use in actual measuring operation.
(2) The radial offset value measuring function of the cutter is that the cutter is provided with a blade groove in the radial direction, and the cutter is in cutter yielding phenomenon in the cutting process, so that the radial offset value cannot be accurately set in a machining program due to the fact that the value is difficult to obtain by a common measuring method, and the machining precision of a final part is seriously affected. The measuring head can accurately acquire the radial offset parameter of the cutter by adopting the measuring method, the part to be processed is subjected to trial cutting after being offset according to the nominal radius offset, then the measuring head is called according to the radial zero offset to measure the cutting surface, the measuring result is the error value of the nominal offset, and the radial offset parameter of the cutter can be accurately acquired by subtracting the error from the nominal radius offset.
(3) The measuring head can be directly used for measuring the deviation of straightness, parallelism and repeated positions (points); the actual measurement of the dimensions can also be carried out in combination with standard blocks or machine tool coordinate parameters.
(4) The measuring range of the measuring head on the whole plane can be expanded by combining the rotary control system of the machine tool spindle or the rotary control system added by the measuring head and linking the measuring direction with the rotary control system, thereby being more beneficial to the on-line measurement of actual parts.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the invention are intended to be included within the scope of the invention.
Claims (5)
1. The single-axis measuring type measuring head is characterized by comprising a shell (1), a sensor, a deflection measuring mechanism, a measuring rod (2) and a laser line indicating device (3); the shell (1) is arranged on a machine tool; the sensor is positioned in the shell (1), and the deflection measuring mechanism is positioned in the shell (1) and corresponds to a position below the sensor; the upper end of the measuring rod (2) is positioned in the shell (1), the lower end of the measuring rod extends downwards to the outside of the shell (1) and is provided with a measuring ball (4) which is in contact with a workpiece, the upper end of the measuring rod (2) is connected with a movable grid (5) of the sensor through the deflection measuring mechanism, and the movable grid (5) of the sensor is driven to swing left and right synchronously relative to a static grid (6) of the sensor so as to realize measurement; the laser line indicating device (3) is fixed on the shell (1), the direction of a downward emitted laser line (7) is consistent with the measurement deflection direction of the measuring rod (2), and the laser line indicating device is used for correcting the measurement direction when the shell (1) is mounted on a machine tool and indicating the measurement direction when in measurement;
The measuring method of the single-axis measuring type measuring head comprises the following steps: the sensor is an absolute angle sensor, an absolute angle position value A 0 corresponding to the measurement contact point of the measuring ball (4) when the measurement contact point is positioned on the central line of a main shaft of a machine tool is calibrated to be a zero reference value, and the relative zero deflection angle of the spherical center of the measuring ball (4) is alpha 0; during measurement, calculating the offset L between a measurement contact and the center of a machine tool spindle according to the position of a spherical measuring point of the measuring ball (4) and a trigonometric function relation through the swing radius H of the measuring ball (4), a zero reference value A 0 and a relative zero deflection angle alpha 0 of the center of the measuring ball (4);
Calibrating the swing radius H of the ball (4) by:
Under the drive of machine tool feeding, a measuring ball (4) of a measuring rod (2) contacts with the corresponding position of a reference block, the measuring rod (2) swings leftwards or rightwards along the direction of a laser line (7) emitted by a laser line indicating device (3), after the measuring rod (2) swings, a movable grid (5) of a sensor is driven by a deflection measuring mechanism to synchronously swing relative to a static grid (6) so as to measure the deflection angle alpha 1, the travelling path S relative to a machine tool spindle is read by a machine tool measuring system, and finally the swinging radius H of the measuring ball (4) is calibrated according to the following formula through alpha 1 and S: h=s/α 1 x 180/pi;
calibrating a zero reference value when a measuring contact of the measuring ball (4) is positioned on the central line of a main shaft of a machine tool by the following method:
Under the drive of machine tool feeding, a measuring ball (4) of a measuring rod (2) firstly contacts one side of a calibration point (14), the measuring rod (2) swings leftwards or rightwards along the direction of a laser line (7) emitted by a laser line indicating device (3), and after the measuring rod (2) swings, a movable grid (5) of the sensor is driven by a swing measuring mechanism to swing synchronously relative to a static grid (6) and the absolute value of the swing angle is A 1; then the main shaft of the machine tool is controlled to rotate 180 degrees, and then the measuring ball (4) of the measuring rod (2) is driven to contact the other side of the calibration point (14), so that the measuring rod (2) swings leftwards or rightwards along the direction of the laser line (7) emitted by the laser line indicating device (3), and after the measuring rod (2) swings, the movable grid (5) of the sensor is driven to synchronously swing relative to the static grid (6) through the swinging measuring mechanism, and the absolute value of the swinging angle is A 1'; calculating a zero reference value A 0：A0=（A1+A1 ')/2 when the measuring contact point of the measuring ball (4) is positioned on the central line of the main shaft of the machine tool according to A 1 and A 1';
and calculating the deflection angle alpha 0 of the sphere center of the measuring sphere (4) relative to the zero reference according to the following formula:
α 0 =asin (d/2/H), d being the diameter of the sphere (4);
During measurement, the offset L of the measuring contact point and the center of the main shaft of the machine tool is calculated according to the trigonometric function relation of H, A 0 and alpha 0 and according to the spherical contact point position of the measuring ball (4) in the following way:
Under the drive of machine tool feeding, a measuring ball (4) of the measuring rod (2) contacts a workpiece (15), the measuring rod (2) swings leftwards or rightwards along the direction of a laser line (7) emitted by the laser line indicating device (3), and after the measuring rod (2) swings, the movable grid (5) of the sensor is driven by the deflection measuring mechanism to synchronously swing relative to the static grid (6) and the absolute value of the angle of the deflection is A 3; according to A 3 and A 0, calculating an angle offset alpha=A 3-A0 between the measuring contact and the center of the main shaft of the machine tool, and finally calculating the offset between the measuring contact and the center of the main shaft of the machine tool through H, alpha and alpha 0: l=h (SIN (α+α 0)-sinα0).
2. The single-axis measurement probe according to claim 1, wherein the runout measuring mechanism comprises a reset sleeve (8), a reset spring (9), a swing rod (10) and a reset cylinder (11); the reset sleeve (8) is fixed in the shell (1) and corresponds to a position below the sensor, and the reset spring (9) is positioned at the top in the reset sleeve (8); the swing rod (10) is arranged in the reset sleeve (8) towards the left side and the right side of the shell (1) in a swinging way, the upper end of the swing rod (10) freely penetrates through the reset spring (9) and then extends out of the upper part of the reset sleeve (8), the swing rod is finally fixedly connected with the movable grid (5) of the sensor, and the lower end of the swing rod (10) extends out of the lower part of the reset sleeve (8) and is then fixedly connected with the upper end of the measuring rod (2); the middle part of pendulum rod (10) is equipped with a circular bead structure, return tube (11) suit is in outside pendulum rod (10) and correspond circular bead structure with between reset spring (9), and the upper and lower both ends of reset spring (9) support respectively reset sleeve (8) top inner wall with the upper end of return tube (11), and then make the lower extreme pressure of return tube (11) is in circular bead structure's up end is in order to guarantee reset spring (9) are in measuring staff (2) all provide reset force when the beat left or right.
3. A single axis measurement probe according to claim 2, wherein the yaw measurement mechanism further comprises a rotating cylinder and two bearings (12); the front and rear ends of the rotary cylinder are respectively extended out of the front and rear sides of the swing rod (10); the inner rings of the two bearings (12) are respectively fixed on the front end and the rear end of the rotary cylinder, and the outer rings of the two bearings are respectively fixed on the corresponding positions on the inner wall of the front side or the rear side of the reset sleeve (8).
4. A single axis measurement probe according to claim 3, further comprising a mounting shank (13) fixed to the top of the housing (1) for connecting to a spindle of a machine tool, and the axis of the mounting shank (13) extends through the centre of the slewing cylinder.
5. The single axis measurement probe according to any one of claims 1 to 4, further comprising a wireless transmitter (16); the wireless transmitter (16) is arranged in the shell (1) and is electrically connected with the sensor, and wirelessly transmits the measurement data of the sensor to an external terminal display unit, and the terminal display unit runs corresponding application programs and processes and displays the measurement data according to the requirement.
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