CN116442000A - Calibration device and calibration method for probe pre-travel of in-situ detection system of CNC machine tool - Google Patents

Abstract

The invention discloses a calibration device for the pre-travel of the measuring head of the in-situ detection system of a numerically controlled machine tool, which comprises a triggering measuring head, a probe is arranged at the end of the triggering measuring head, and an equilateral triangular pyramid is arranged at the vertically corresponding position at the bottom of the probe. , the top of the extension rod is in contact with the bottom of the regular triangular prism and fixed to each other, the bottom end of the extension rod is fixed with the magnetic table base, and the side of the magnetic table base is also provided with a limit structure. The invention also discloses a method for calibrating the pre-travel of the measuring head of the in-situ detection system of the numerical control machine tool. The invention solves the problem of low pre-stroke detection accuracy existing in the prior art.

Description

Calibration device and calibration method for probe pre-travel of in-situ detection system of CNC machine tool

technical field

The invention belongs to the technical field of in-situ detection of numerical control machining accuracy in the part manufacturing process, and in particular relates to a calibration device for the pre-stroke of a probe in an in-situ detection system of a numerically controlled machine tool. calibration method.

Background technique

The in-situ detection technology of the CNC machining accuracy of the workpiece saves the transfer of the workpiece between the machine tool and the testing equipment, avoids the manufacturing error caused by the misalignment of the process benchmarks, reduces unnecessary time and material consumption, reduces labor intensity, and improves the production efficiency. Productivity is of great significance to realize the intelligentization, high efficiency and high precision of the product manufacturing process.

The trigger probe is the key component of the in-situ detection system. The typical structure of a certain type of probe is shown in Figure 1. During in-situ detection, when the probe 1 touches the workpiece, a trigger signal is generated, and the numerical control system responds to the signal and records the coordinate value of the point. Measure multiple measuring points as required, and generate a test report through data processing.

Probe measurement work sequence shown in Figure 2 . The time when the probe probe contacts the workpiece is T ₁ , the time when the probe sends out the trigger signal is T ₂ , and the time when the numerical control system responds to the trigger signal is T ₃ ; the pre-travel of the probe is the period from T ₁ to T ₃ The relative displacement between the measuring head and the measured workpiece. Relevant studies have shown that the detection error is caused by the deviation between the position of the measuring point recorded by the numerical control system and the actual contact position between the probe and the measured workpiece (that is, the pre-travel), which accounts for more than 60% of the overall error of in-situ detection. Compensation is an effective means to reduce the impact of the probe pre-travel on the in-situ detection accuracy, and whether the measurement calibration value of the probe pre-travel is accurate is the decisive factor for the compensation accuracy.

Generally, the directions in which the three-dimensional touch probe can be triggered include any direction in the XY plane (radial direction) and the +Z direction (axial direction). Affected by the structural characteristics of the trigger mechanism of the probe, the pre-travel of the probe is not consistent in different trigger directions. Therefore accurate compensation should be done specifically along different directions. The axial pre-travel of the probe is very different from the pre-travel in other directions. As shown in Figure 3, the measurement along the Z direction (axial direction) of the probe is mostly used to determine the machining allowance and cutting depth of the workpiece. The measurement results It directly determines the selection of cutting process parameters and the final machining accuracy of the workpiece. Therefore, the axial pre-travel of the probe must be accurately measured before measurement.

At present, for the axial pre-travel of the probe, there are two methods that can realize the fixed value measurement: one is to use independent measuring equipment (hereinafter referred to as the independent method). Install the probe on the equipment with motion control, contact state monitoring, trigger signal recognition and displacement measurement, simulate the trigger measurement process of the trigger probe, and measure its pre-travel. Considering that the pre-travel of the probe will be affected by the measurement conditions, the measurement should not be independent of the machine tool operating environment. The measurement results of the independent method cannot accurately reflect the pre-travel when the probe is measured; in addition, this method uses the moment when the probe sends a trigger signal instead of the time when the actual measurement records the position coordinates of the numerical control as the calculation basis for the pre-travel, which makes the method exist Error; third, the cost of independent measuring equipment is high, the operation is cumbersome, and the engineering adaptability is poor. The second is the radius of action method. During data processing of measurement results, it is usually necessary to compensate the radius of the probe. Due to the pre-travel of the probe, it is inaccurate to compensate with the nominal radius of the probe ball during actual measurement. Touch and measure several measuring points on the surface of the standard sphere, calculate the measurement radius of the standard sphere, and the difference between it and the nominal radius of the standard sphere is the radius of action of the probe ball including the pre-travel of the probe, which can be used for compensation. To a certain extent, the influence of the pre-travel on the measurement results is reduced. The radius of action method replaces the actual pre-travel with the equivalent mean value of the pre-travel in each direction, which averages the error. However, the pre-travel of the touch-trigger probe in each direction is not the same, or even has a large difference. This idea of compensation based on the average error is not applicable to the occasion of measuring along the axial direction, and it is difficult to effectively improve the measurement accuracy. It should be pointed out that, with the standard ball as the calibration body, the probe is in contact with the standard ball during measurement and calibration. Affected by the friction angle between the two, there will inevitably be slippage between the two, which will lead to errors in the measurement point data, and affect the Calibration measurement accuracy. At the same time, the more the number of measurement points, the more random error components in the measurement data, and the greater the data fitting error, so the number of measurement points should be reduced as much as possible.

Contents of the invention

The object of the present invention is to provide a calibration device for the pre-travel of the measuring head of the in-situ detection system of the numerical control machine tool, which solves the problem of low pre-travel detection accuracy existing in the prior art.

Another object of the present invention is to provide a method for calibrating the pre-travel of the measuring head of the in-situ detection system of the numerical control machine tool.

The first technical solution adopted by the present invention is that the calibration device for the probe pre-travel of the in-situ detection system of the CNC machine tool includes a trigger probe, the end of the trigger probe is provided with a probe, and the vertical corresponding position at the bottom of the probe is A regular triangular prism is provided, the top of the extension rod is in contact with the bottom of the regular triangular prism and fixed to each other, the bottom of the extension rod is fixed to the magnetic table base, and the side of the magnetic table is also provided with a limit structure.

The feature of the first technical solution of the present invention is also that,

There is a waist-shaped through-slot parallel to the length of the rod on the extension rod, and the set screw passes through the waist-shaped through-slot and is tightened into the screw hole on the magnetic table base, so as to realize the connection and fixation of the regular triangular pyramid and the magnetic table base.

The specific structure of the limit structure is as follows: an upright block and a lying block are fixed on the edge of the facade on which the set screw is installed on the magnetic meter base.

Both the upright block and the lying block are in the shape of a long cube and have the same orientation, and the upright block and the lying block are parallel to each other and perpendicular to the magnetic meter base.

The second technical solution adopted by the present invention is a method for calibrating the pre-travel of the measuring head of the in-situ detection system of the CNC machine tool, which is specifically implemented according to the following steps:

Step 1. Adsorb the regular triangular pyramid platform on the CNC machine tool workbench through the magnetic table base;

Step 2, adjust the position of the X-axis, Y-axis and Z-axis of the machine tool, position the probe on the trigger probe at a certain section of the regular triangular pyramid, and record the Z-axis coordinate _Z1 at this time;

Step 3. Keep the Z-axis still, and the X-axis and Y-axis are linked. Touch and measure 6 points evenly distributed on the three sides on the section to be tested of the regular triangular prism, that is, 2 points on each side, and record it. The position coordinates (X _i , Y _i ) of each measuring point, i=a, b, c, d, e, f, where a, b, c, d, e, f represent the three sides on the measured section The name of each measuring point;

Step 4. Calculate the straight line equations of the three sides of the measured section for the series of coordinate values obtained in step 3, respectively, to obtain the straight line equations of the three sides of the equilateral triangle of the measured section and the coordinates of the three vertices, and then obtain the side length L of the measured section ,details as follows:

Let the equation of the straight line DF be

y _DF =K·x+B

Among them, K is the slope of the straight line, B is the intercept of the straight line,

Bring the coordinates (X _a , Y _a ) of measuring point a and the coordinates (X _b , Y _b ) of measuring point b into the above formula to obtain the equation of straight line DF; similarly, the coordinates of measuring point f (X _f , Y _f ) and the coordinates of measuring point e (X _e , Y _e ) to get the equation of straight line DE; the coordinates of measuring point d (X _d , Y _d ) and the coordinates of measuring point c (X _c , Y _c ) Get the equation of the straight line EF;

Simultaneously solve the equation of straight line DF and straight line DE to obtain the coordinates (X _D , Y _D ) of point D; similarly, solve the equation of straight line DE and straight line EF simultaneously to obtain the coordinates of point E (X _E , Y _E ); solve the equation of the straight line DF and the equation of the straight line EF simultaneously, and obtain the coordinates (X _F , Y _F ) of the point F, which can be obtained according to the distance formula between two points

Step 5, combining the side length l of the top surface of the regular triangular prism and the dihedral angle α between the sides and the bottom of the regular triangular prism, the theoretical distance Δh between the measured section and the top surface of the truncated cone is obtained:

Step 6. Move the trigger probe upward along the Z axis, so that the probe of the trigger probe is higher than the regular triangular pyramid;

Step 7, X-axis, Y-axis interpolation linkage, position the probe of the trigger probe directly above the top surface of the regular triangular pyramid;

Step 8, the CNC machine tool drives the trigger probe to move downward along the Z axis to touch any point on the top surface of the regular triangular pyramid, and record the Z axis coordinate Z ₂ when triggered;

Step 9, combining the theoretical distance Δh between the measured section and the top surface of the cone frustum obtained in step 5, and the Z-axis coordinate Z ₁ of the cone surface obtained in step 2, to obtain the axial pre-travel τ of the trigger probe,

τ＝△h-[(z ₂ -r)-(z ₁ +r·cosα)]

In the formula, r is the radius of the probe measuring ball, and α is the dihedral angle between the side and the bottom of the regular triangular pyramid;

After the measurement, remove the measuring device.

The beneficial effects of the present invention are: 1. The present invention calculates the side length of the measured section by touching 6 measuring points evenly distributed on three sides on any section parallel to the bottom surface on the regular triangular pyramid truncated, and then obtains the measured section and Theoretical distance between the top surfaces of the regular triangular prism truss; the difference between it and the actual measured value between the top surface of the regular triangular prism truncated and the measured section is the axial pre-travel of the probe, which can be used to compensate and correct the in-situ measurement results. Reduce the impact of pre-travel on measurement accuracy and improve the measurement accuracy of integrated in-situ detection. 2. The present invention corrects the in-situ detection results based on the measurement and calibration results, avoiding the measurement error caused by the difference between the measuring point position touched by the probe and the measuring point position recorded by the numerical control system; avoiding the existing method The error generated by the actual axial pre-travel is replaced by the average value of the pre-travel in each direction of the probe, which improves the measurement accuracy. 3. The method of the present invention measures the pre-travel of the trigger probe under the actual in-situ detection working condition of the CNC machine tool, and the result truly reflects the pre-travel characteristics of the probe during the measurement process, which can effectively improve the measurement accuracy. And the regular triangular pyramid is used as the measuring tool, no other equipment is needed, the use cost is low, and the operation is simple and convenient. 4. The trigger probe is used for point-by-point measurement, and the measurement point data is used as the basis for calculating the measurement results. The accuracy of the measurement point data determines the accuracy of the measurement results. On the one hand, the number of measuring points affects the measurement efficiency, and on the other hand, it also affects the final measurement accuracy. It can be seen from the above analysis that due to the pre-travel characteristics of the trigger probe, the measurement point data contains random errors, the more the number of measurement points, the greater the random error, and the lower the final measurement accuracy; at the same time, if the standard ball is used to calibrate the probe, the probe It is in point contact with the standard ball, affected by the friction angle, the two are prone to slippage, resulting in a deviation between the actual measurement point data and the theoretical data, which in turn causes a decrease in measurement accuracy. The invention only needs to collect two measuring points on each side of the triangular pyramid truncated section, and the number of measuring points is greatly reduced. At the same time, the contact of the pre-calibration body of the probe is point-to-line contact, and the measurement path and the position of the measurement point are designed with the friction angle as the constraint, which greatly avoids the occurrence of measurement point errors caused by the phenomenon of measurement point slippage, and can effectively ensure the accuracy of the prediction. The stroke calibrates the accuracy of the measurement process.

Description of drawings

Figure 1 is a schematic diagram of the basic structure of a trigger probe;

Fig. 2 is a timing diagram of the touch detection work of the trigger probe;

Fig. 3 is a schematic structural diagram of a CNC machine tool equipped with a trigger probe;

Fig. 4 is a schematic diagram of the measurement principle of the method for measuring the axial pre-travel of the touch probe of the present invention;

Fig. 5 (a) is a schematic diagram of the measurement device of the axial pre-travel measurement method of the trigger probe of the present invention;

Fig. 5(b) is a schematic diagram of another angle of view of the measuring device for the axial pre-travel measurement method of the trigger probe of the present invention, and Fig. 5(b) is a left view of Fig. 5(a);

Fig. 6 is an enlarged view of the details of the neutral stopper 7 and the horizontal stopper 9 of the calibration device of the in-situ detection system of the CNC machine tool of the present invention;

Fig. 7 is a measurement schematic diagram of embodiment 2 of the present invention.

In the figure, 1. Probe; 2. Trigger probe; 3. Triangular pyramid platform; 4. CNC machine table; 5. Extension rod; 6. Magnetic table base; Screw; 9. Recumbent stopper.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Referring to Fig. 1, Fig. 3 and Fig. 5 (a) and Fig. 5 (b), the calibration device of the in-situ detection system of the numerical control machine tool of the present invention includes a trigger probe 2, and the end of the trigger probe 2 is provided with There is a probe 1, a regular triangular pyramid 3 is arranged at the vertical corresponding position at the bottom of the probe 1, the top of the extension rod 5 is in contact with the bottom of the regular triangular pyramid 3 and fixed to each other, the bottom of the extension rod 5 is fixed to the magnetic base 6, and the magnetic force The side of table seat 6 is also provided with a position-limiting structure.

There is a waist-shaped through groove parallel to the length direction of the rod on the extension rod 5, and the set screw 8 passes through the waist-shaped through groove and is tightened in the screw hole on the magnetic gauge base 6, thereby realizing the regular triangular pyramid 3 and the magnetic gauge The connection of seat 6 is fixed.

The specific structure of the position-limiting structure is as follows: the edge of the facade on which the set screw 8 is installed on the magnetic gauge base 6 is fixed with an upright block 7 and a lying block 9 .

Upright block 7 and recumbent block 9 are long cuboid shapes and towards the same direction, and upright block 7 and recumbent block 9 are parallel to each other and perpendicular to magnetic table base 6. As shown in FIG. 6 , the plane ghij on the standing block 7 and the plane klmn on the lying block 9 are perpendicular to each other. With the help of this structure, the positioning of the vertical and lying postures of the regular triangular prism can be realized; when adjusting the attitude of the regular triangular prism 3, the set nut 8 is loosened, and the regular triangular prism 3 and the lengthened joint are rotated around the axis of the set nut 8. Rod 5, when the side wall of the extension rod 5 is in contact with the plane ghij on the upright block 7, tighten the set nut 8, which is a vertical installation posture; if the extension rod 5 is rotated around the axis of the set nut 8 When its side wall is in contact with the plane klmn on the recumbent position block 9, the fastening nut 8 is tightened, which is now a horizontal installation posture. Fig. 6 is a measurement schematic diagram of Embodiment 2 of the present invention, wherein the thin dotted line represents the section and path measured by the probe, and the dotted line represents the path of the probe when the top surface of the regular triangular pyramid is touched after the cross section is measured. When measuring and calibrating, first install the regular triangular pyramid on the top of the extension rod 5 reliably, and ensure that the bottom surface of the regular triangular pyramid is perpendicular to the axis of the extension rod; loosen the set screw 8, and adjust the extension rod according to the attitude of the probe to be calibrated 5, after the positioning is accurate, tighten the set screw 8; finally, attach the whole device to a suitable position on the workbench 4 of the CNC machine tool to start measurement and calibration.

The calibration method of the probe pre-travel of the in-situ detection system of the CNC machine tool is implemented according to the following steps:

Step 1, the regular triangular pyramid table 3 is adsorbed on the CNC machine tool workbench 4 through the magnetic table base 6;

Step 2, adjust the position of the X-axis, Y-axis and Z-axis of the machine tool, position the probe 1 on the trigger probe 2 at a certain section of the regular triangular pyramid 3, and record the Z-axis coordinate _Z1 at this time;

Step 3. Keep the Z-axis still, and the X-axis and Y-axis are linked, touch and measure 6 points evenly distributed on the three sides on the section to be tested of the regular triangular pyramid 3, that is, 2 points on each side, and record The position coordinates (X _i , Y _i ) of each measuring point below, i=a, b, c, d, e, f, where a, b, c, d, e, f represent the three sides on the measured section The name of each measuring point;

Step 4. Calculate the linear equations of the three sides of the measured section for the series of coordinate values obtained in the step 3, respectively, to obtain the linear equations of the three sides of the equilateral triangle of the measured section and the coordinates of the three vertices, and then obtain the sides of the measured section Long L, as follows:

Let the equation of the straight line DF be

y _DF =K·x+B

Among them, K is the slope of the straight line, B is the intercept of the straight line,

Bring the coordinates (X _a , Y _a ) of measuring point a and the coordinates (X _b , Y _b ) of measuring point b into the above formula to obtain the equation of straight line DF; similarly, the coordinates of measuring point f (X _f , Y _f ) and the coordinates of measuring point e (X _e , Y _e ) to get the equation of straight line DE; the coordinates of measuring point d (X _d , Y _d ) and the coordinates of measuring point c (X _c , Y _c ) Get the equation of the straight line EF;

Simultaneously solve the equation of straight line DF and straight line DE to obtain the coordinates (X _D , Y _D ) of point D; similarly, solve the equation of straight line DE and straight line EF simultaneously to obtain the coordinates of point E (X _E , Y _E ); solve the equation of the straight line DF and the equation of the straight line EF simultaneously, and obtain the coordinates (X _F , Y _F ) of the point F, which can be obtained according to the distance formula between two points

Step 5, combining the side length l of the top surface of the regular triangular prism and the dihedral angle α between the sides and the bottom of the regular triangular prism, the theoretical distance Δh between the measured section and the top surface of the truncated cone is obtained:

Step 6. Move the trigger probe upward along the Z axis, so that the probe of the trigger probe is higher than the regular triangular pyramid;

Step 7, X-axis, Y-axis interpolation linkage, position the probe 1 of the trigger probe 2 directly above the top surface of the regular triangular pyramid;

Step 8, the CNC machine tool drives the trigger probe 2 to move downward along the Z axis to touch any point on the top surface of the regular triangular pyramid, and record the Z axis coordinate Z ₂ when triggered;

Step 9, combining the theoretical distance Δh between the measured section and the top surface of the cone frustum obtained in step 5, and the Z-axis coordinate Z ₁ of the cone surface obtained in step 2, to obtain the axial pre-travel τ of the trigger probe,

τ＝△h-[(z ₂ -r)-(z ₁ +r·cosα)]

In the formula, r is the radius of the probe measuring ball, and α is the dihedral angle between the side and the bottom of the regular triangular pyramid;

After the measurement, remove the measuring device.

The pre-travel (axial) measurement method of the trigger probe uses a regular triangular pyramid as the measuring tool, see Figure 3, Figure 4, Figure 5, and Figure 6. The principle is that the distance Δh between any section and the top surface of the regular triangular prism truncated can be determined by the side length of the section, the side length of the top surface and the dihedral angle between the side and the bottom surface of the regular triangular prism truncated. Touch and measure 6 points evenly distributed along the circumference on a certain section of the regular triangular prism, and perform a straight line fitting operation on the coordinates of each measuring point to obtain the side length of the tested section; then measure the measured section and the top surface of the regular triangular prism The distance between; Finally, considering the influence of the probe probe radius on the measurement results, the pre-travel (axial) of the trigger probe is:

τ＝△h-[(z ₂ -r)-(z ₁ +r·cosα)]

In the formula, r is the radius of the probe measuring ball, α is the dihedral angle between the side and the bottom of the regular triangular pyramid, Z ₂ is the Z-axis position coordinate corresponding to the top surface of the regular triangular pyramid; Z ₁ is the Z-axis position coordinate corresponding to the measured section , Δh is the theoretical distance between the measured section and the top surface of the frustum.

After the measurement, remove the measuring device.

Example 1

This embodiment measures the axial pre-travel of the Renishaw LP2 touch probe. Install it on the CNC machine tool shown in Figure 3 in a vertical posture, and the axis of the probe is the Z direction of the CNC machine tool.

Wipe the surface of the regular triangular pyramid and the probe probe clean, and attach the measuring device to a suitable position on the CNC machine table 4 to ensure that it is within the working stroke of the trigger probe 2 in each direction; complete the alignment of a certain section of the regular triangular pyramid and record the position coordinates of each measuring point; calculate the length of the three sides of the measured section; under the control of the NC program, measure the distance between the measured section and the top surface of the regular triangular pyramid; finally calculate the axial direction of the probe Pre-trip.

Comparison of experimental results

Adopt the measurement result of the present invention's measurement calibration method and adopt the measurement result of radius of action method to see the following table 1,

Table 1 Axial pre-travel of different measurement methods

From the comparison, it can be found that the pre-travel obtained by the radius of action method is greater than the pre-travel obtained by the method of the present invention. Since the radial pre-travel of the probe is greater than the pre-travel when triggered along the axial direction, the method of action radius using the idea of averaging error will make the measured value of the axial pre-travel affected by the pre-travel in other directions, and the obtained results are quite different. big error. Experiments show that using this as the compensation value of the pre-travel will affect the accuracy of in-situ detection. According to the results in related literature, when using the independent equipment method to measure the same type of probe as this example, the axial pre-travel is about 0.002mm, which is much smaller than the result obtained by this method. This is because the independent equipment method makes the measurement of the probe It is independent of its measurement conditions, and it uses the moment when the probe sends out the trigger signal instead of the moment when the NC records the position coordinates during actual measurement as the calculation basis for the pre-travel, so that the measurement results cannot reflect the real situation of the probe pre-travel during measurement. Not suitable for on-site compensation of trigger probe pre-travel.

Example 2

Referring to Figure 7, the measuring head is installed horizontally, and the axial direction is the X direction of the CNC machine tool.

First loosen the set screw 8, rotate the regular triangular pyramid 90° around the axis of the set screw, and make the extension rod contact with the horizontal posture stopper 9, tighten the set screw 8 after it is in place, and absorb it to the machine table The appropriate position of the trigger probe 2 is guaranteed to be within the travel range of the trigger probe 2 in all directions;

Then control the movement of each axis of the machine tool, position the trigger probe probe on the cross-section of the regular triangular pyramid and perform a touch test, and record the X-axis coordinate X ₁ when triggering (the position shown by the thin dotted line in Figure 7);

Through the interpolation movement of the Z and Y axes, touch six points evenly distributed on the section to be measured (two measuring points on each side of the section), and record the position coordinates of each measuring point (Z _i , Y _i );

Perform fitting calculations on the obtained series of coordinate values to obtain the straight line equations and vertex coordinates of the three sides of the measured section, and finally calculate the side length L of the section;

Adjust each axis of the machine tool so that the probe probe is far away from the regular triangular pyramid in the X direction;

Position the probe within the range of the top surface of the cone by interpolating the Z and Y axes;

The X-axis touches the apex of the regular triangular prism, and records the coordinate X ₂ of the X-axis when the probe is triggered.

Data processing: According to the X-direction coordinate X ₁ of the measured section, the side length L of the measured section and the X-direction coordinate X ₂ of the top surface of the cone frustum, calculate the axial pre-travel of the trigger probe given by the method of the present invention The formula calculates the pre-travel (axial) of the probe;

After the measurement is completed, remove the measuring tools, and fill in the calculated pre-travel of the probe into the compensation table of the in-situ detection data processing software.

Claims (5)

1. The calibrating device of digit control machine tool normal position detecting system gauge head advance stroke, its characterized in that, including trigger gauge head (2), trigger gauge head (2) tip is equipped with probe (1), and vertical corresponding position department in probe (1) bottom is provided with regular triangular pyramid platform (3), and extension bar (5) top contacts and mutually fixes with regular triangular pyramid platform (3) bottom, and extension bar (5) bottom is fixed with magnetic gauge stand (6), and magnetic gauge stand (6) side still is provided with limit structure.

2. The calibrating device for the pre-stroke of the measuring head of the numerical control machine tool in-situ detection system according to claim 1, wherein the extension rod (5) is provided with a waist-shaped through groove parallel to the length direction of the rod, and the fastening screw (8) passes through the waist-shaped through groove and is screwed in a screw hole on the magnetic gauge stand (6), so that the regular triangular pyramid table (3) is fixedly connected with the magnetic gauge stand (6).

3. The calibrating device for the pre-stroke of the measuring head of the in-situ detection system of the numerical control machine tool according to claim 2, wherein the limiting structure is specifically structured as follows: the vertical surface edge of the magnetic meter seat (6) is provided with a set screw (8) and is fixedly provided with a vertical position stop block (7) and a horizontal position stop block (9).

4. The calibrating device for the pre-stroke of the measuring head of the numerical control machine tool in-situ detection system according to claim 3, wherein the vertical stop block (7) and the horizontal stop block (9) are long cubes and are consistent in orientation, and the vertical stop block (7) and the horizontal stop block (9) are parallel to each other and are perpendicular to the magnetic meter base (6).

5. The calibration method of the pre-stroke of the measuring head of the in-situ detection system of the numerical control machine tool is characterized by being based on the calibration device of the pre-stroke of the measuring head of the in-situ detection system of the numerical control machine tool, which is specifically implemented according to the following steps:

step 1, adsorbing a regular triangular pyramid table (3) on a workbench (4) of a numerical control machine tool through a magnetic meter seat (6);

step 2, adjusting the positions of an X axis, a Y axis and a Z axis of a machine tool, positioning a probe (1) on a trigger type measuring head (2) at a certain section of a regular triangular pyramid table (3), and recording a Z axis coordinate Z at the moment ₁ ；

Step 3, keeping the Z axis motionless, linking the X axis and the Y axis, touching 6 points uniformly distributed on three sides on the section to be measured of the regular triangular pyramid table (3), namely 2 points on each side, and recording the position coordinates (X _i 、Y _i ) I= a, b, c, d, e, f, wherein a, b, c, d, e, f represents the name of each measuring point on three sides of the measured section;

and 4, respectively calculating linear equations of three sides of the measured section on the series of coordinate values obtained in the step 3 to obtain linear equations of three sides of the measured section regular triangle and three vertex coordinates, and further obtaining the side length L of the measured section, wherein the method comprises the following steps of:

let equation of straight line DF be

y _DF ＝K·x+B

Wherein K is the slope of a straight line, B is the intercept of the straight line,

coordinates of the measurement point a (X _a 、Y _a ) Coordinates of the measurement point b (X _b 、Y _b ) Carrying out the equation, namely solving the equation of the straight line DF; similarly, the coordinates (X _f 、Y _f ) Measuring point eCoordinates (X) _e 、Y _e ) Obtaining an equation of a straight line DE; coordinates of the measurement point d (X _d 、Y _d ) Coordinates of the measurement point c (X) _c 、Y _c ) Obtaining an equation of a straight line EF;

the equation of the straight line DF is combined with the equation of the straight line DE and solved to obtain the coordinates (X _D 、Y _D ) The method comprises the steps of carrying out a first treatment on the surface of the Similarly, the equation of the straight line DE and the equation of the straight line EF are solved simultaneously to obtain the coordinates (X _E 、Y _E ) The method comprises the steps of carrying out a first treatment on the surface of the Solving the equation of the straight line DF and the equation of the straight line EF simultaneously to obtain the coordinates (X _F 、Y _F ) According to the formula between two points

Step 5, combining the side length l of the top surface of the regular triangular pyramid and the dihedral angle alpha of the side surface and the bottom surface of the regular triangular pyramid to obtain the theoretical distance delta h between the measured section and the top surface of the triangular pyramid:

step 6, moving the trigger type measuring head upwards along the Z axis so that the trigger type measuring head probe is higher than the regular triangular pyramid table;

step 7, the X-axis and Y-axis interpolation linkage is carried out, and a probe (1) of the trigger type measuring head (2) is positioned right above the top surface of the triangular pyramid table;

step 8, the numerical control machine drives the trigger type measuring head (2) to move downwards along the Z axis to touch and measure any point on the top surface of the regular triangular pyramid table, and the Z axis coordinate Z during triggering is recorded ₂ ；

Step 9, combining the theoretical distance delta h between the measured section obtained in the step 5 and the top surface of the frustum, and the Z-axis coordinate Z of the frustum surface obtained in the step 2 ₁ To obtain the axial pre-stroke tau of the trigger type measuring head,

τ＝△h-[(z ₂ -r)-(z ₁ +r·cosα)]

wherein r is the radius of the probe sphere, and alpha is the dihedral angle between the side surface and the bottom surface of the regular triangular pyramid;

and after the measurement is finished, taking down the measuring device.