Spot-facing Accuracy Measurement Method

Abstract

The present invention discloses a countersink accuracy measurement method in the field of hole-making detection. A measuring head with a taper angle at the front end and a detector capable of accurately measuring the height position of the measuring head are used as measuring tools. The taper angle of the measuring head needs to be greater than the chamfer angle of the countersink to be measured. The measurement process includes the following steps: First, place the measuring head directly above the countersink, and determine a zero position of the measuring head through the detector. Then, select a standard countersink as the measurement reference, move the measuring head downward from the zero position so that the conical surface of the bottom taper angle of the measuring head contacts the outer edge of the hole diameter of the countersink, and record the height H0 of the measuring head's descent through the detector. Finally, use the above method to detect the countersink to be measured, and record the height H1 of the measuring head's descent from the zero position. This measurement method can convert the deviation of the countersink hole diameter into the change of the height position of the measuring head, and can quickly judge whether the countersink is qualified by detecting the position of the measuring head, which is convenient and fast, and can also avoid the interference of material powder on the measurement.

Description

Technical Field

[0001] The present invention relates to the field of hole-making detection, and particularly to a method for measuring countersink accuracy. Background Art

[0002] Usually when manufacturing aircraft aerodynamic parts, it is often necessary to make countersunk holes on the part surface, and there are very high requirements for the chamfer depth (i.e., countersink depth) of the countersunk holes. If the countersink depth is too shallow, it may cause poor fitting of the fastener head, affecting the mechanical strength of the fastener (excessive extrusion stress on the surface and creep of the part material resulting in a decrease in the pre-tightening force of the fastener), and also affecting the anti-corrosion performance of the assembled part; if the countersink depth is too deep, it reduces the bearing depth of the hole and also affects the mechanical strength. In addition to detecting the countersink depth, in the actual production process, sometimes tolerance requirements are also put forward for the countersink diameter. The countersink diameter refers to the diameter of the outer circle at the top of the countersunk hole, which is used to replace the tolerance requirement of the countersink depth. These two values can be converted into each other through calculation, and the actual purpose is the same.

[0003] For the detection of countersink accuracy, currently it mainly relies on manually holding a countersink depth detection device for detection. To meet the detection accuracy, very high requirements are put forward for the operator's operation method. Usually, most of these countersunk holes are on the curved surface of large parts, and the accessibility is relatively poor. Sometimes the operator needs to measure in a non-ergonomic position; the surface of the countersunk hole is usually a curved surface, and it is very difficult to accurately position the normal direction of the hole with a handheld device. The deviation of the normal direction will have a greater impact on the accuracy of the measurement result. Therefore, when measuring a hole with a handheld device, it often takes multiple measurements to confirm the detection result.

[0004] Generally speaking, in the mass production stage, after the hole-making of the parts is completed, a certain proportion of the countersunk holes will be randomly selected for measuring the countersink depth; but in the research and development production stage, it is required to increase the random selection proportion, or even all of them are inspected. And a large part often has thousands of countersunk holes, and manual operation takes a lot of time and energy.

[0005] In addition, due to its excellent strength and low density, the use proportion of composite materials in aircraft parts shows an obvious upward trend. One characteristic of composite materials is that when making holes, fine composite powder will be generated, and these powders are very easy to adhere to the countersink surface (i.e., the chamfered inclined surface) with cutting fluid and are difficult to completely remove. When measuring the countersink depth with a traditional handheld countersink depth detection device, the countersink surface is used as the measurement target, which is easily affected by the composite powder, and the accuracy is greatly reduced. Summary of the Invention

[0006] To overcome the above deficiencies existing in the existing process of measuring countersink accuracy, the technical problem to be solved by the present invention is: to provide a method for measuring countersink accuracy that can improve the measurement accuracy and efficiency and reduce the influence of material factors.

[0007] The technical solution adopted by the present invention to solve its technical problems is as follows:

[0008] A method for measuring countersink accuracy, using a measuring head with a conical angle at the front end and a detector that can accurately detect the height position of the measuring head as measuring tools. The conical angle α of the measuring head needs to be greater than the chamfer angle β of the measured countersink;

[0009] The measuring process includes the following steps:

[0010] S1. Place the measuring head directly above the countersink, ensure that their axes are aligned, and determine a zero position of the measuring head through the detector;

[0011] S2. Select a standard countersink as the measuring reference, with its hole diameter defined as D0. Move the measuring head downward from the zero position until the conical surface of its bottom conical angle contacts the outer edge of the hole diameter of the countersink, and record the height H0 of the measuring head's descent through the detector;

[0012] S3. Use the method of S2 to detect the measured countersink, record the height H1 of the measuring head's descent from the zero position, and assume the hole diameter of this countersink is D1;

[0013] S4. Calculate the measurement parameters according to the following process:

[0014] ΔH = H0 - H1,

[0015] ΔD = D1 - D0,

[0016] tan(α / 2) = (D0 / 2) / (t - H0) = (D1 / 2) / (t - H1),

[0017] In the formula, ΔH is the height difference of the measuring head in the two measurements, ΔD is the actual deviation value of the countersink hole diameter, and t is the distance from the zero position to the vertex of the conical angle of the measuring head, which will be canceled out during the calculation process. After converting the above formula, we get:

[0018] ΔD = 2tan(α / 2) * ΔH;

[0019] S5. Compare the value of ΔD with the tolerance requirement of the countersink hole diameter to determine whether the countersink is qualified.

[0020] This measuring method can convert the deviation of the countersink diameter into the change of the height position of the measuring head, and the qualification of the countersink can be quickly judged by detecting the position of the measuring head. Moreover, the material powder generated by drilling mainly covers the surface of the countersink and less covers the edge of the countersink. Therefore, by measuring the countersink diameter, the interference of material factors on the measurement can be effectively avoided. As for how the measuring tool moves the measuring head and detects its position, there are currently many linear feed mechanisms with position sensors that can achieve this function. According to this detection principle, a small manual measuring instrument can be made, or it can be integrated into the commonly used automatic hole-making equipment at present. The spindle of the automatic hole-making equipment itself has the functions of linear feed and position detection.

[0021] If the qualification criterion for the countersink is the countersink depth, the calculation process in S4 can be changed to:

[0022] Δh = h1 - h0,

[0023] tan(β / 2) = (D1 / 2) / (h1 + T) = (D0 / 2) / (h0 + T) = (d1 / 2) / T,

[0024] h0 = 0.5*(D0 - d1) / tan(β / 2),

[0025] h1 = 0.5*(D1 - d1) / tan(β / 2),

[0026] In the formula, h0 is the standard countersink depth, h1 is the actual countersink depth, Δh is the actual deviation value of the countersink depth, and T is the distance from the lower edge of the countersink to the vertex of the countersink cone surface, which will be offset in the calculation process. After conversion of the above formula, we get:

[0027] Δh = 0.5*(D1 - D0) / tan(β / 2) = 0.5*ΔD / tan(β / 2)

[0028] = tan(α / 2) *ΔH / tan(β / 2),

[0029] Compare the value of Δh with the tolerance requirement of the countersink depth to judge whether the countersink is qualified. Similarly, by detecting the position of the measuring head, the countersink depth can be obtained, and then it can be judged whether the countersink is qualified.

[0030] For the specific measuring tool, the present invention provides a solution. The measuring tool includes a detection module, a metering module and a feed module;

[0031] The detection module includes a detection rod, a measuring rod, a bushing and a connecting shaft. A conical head is provided at the lower end of the detection rod. The measuring rod is slidably installed inside the detection rod. The bushing is slidably sleeved outside the lower half of the detection rod. A long hole is provided in the lower half of the detection rod along its length direction. Through holes are provided on both the measuring rod and the bushing. The connecting shaft sequentially passes through one side of the bushing, the detection rod, the measuring rod and the other side of the bushing, and both ends are fixed on the through holes of the bushing. A first compression spring is provided between the upper end of the bushing and the upper end of the measuring rod. Under the action of elastic force, the connecting shaft contacts the lower end of the long hole on the detection rod, and the lower end of the bushing extends beyond the lower end of the detection rod;

[0032] The metering module is arranged at the upper end of the detection rod and includes a sleeve coaxial with the detection rod, a driving rod slidable along the axis of the sleeve, and a position sensor installed on the sleeve for detecting the position of the driving rod. The upper end of the measuring rod contacts or is connected to the lower end of the driving rod;

[0033] The feeding module includes a linear feeding mechanism that can drive the detection module and the metering module to move linearly.

[0034] The measuring process of this measuring tool is as follows: First, make the lower end of the bushing contact the surface of the workpiece, and the axis of the detection rod is coaxial with the axis of the countersink. Then move the detection rod downward. During this process, the sleeve and the position sensor will move downward together with the detection rod. Since the bushing contacts the surface of the workpiece and the measuring rod is connected to the bushing through the connecting shaft, the measuring rod and the driving rod are fixed. This continues until the conical surface of the conical head at the lower end of the detection rod contacts the outer edge of the countersink, at which point the detection rod stops moving. The position sensor will record the distance it moves relative to the measuring rod along with the detection rod. By detecting the standard countersink and the actual countersink, the values of H0 and H1 mentioned above can be obtained respectively, so as to obtain ΔH and ΔD, and then determine whether the countersink is qualified.

[0035] This measuring tool can be used alone or in combination with automatic hole-making equipment. To ensure the measuring accuracy, it is necessary to control the normal state, that is, to ensure that the axis of the detection rod is as coaxial as possible with the axis of the countersink. For countersinks on a plane, it is easy to control the normal state when using this measuring tool alone. If it is a curved surface, it is best to use the normal function of the spindle of the automatic hole-making equipment to determine the normal state of the detection rod.

[0036] For parts with curved surfaces, if a bushing is directly in contact with the curved surface part, it may lead to instability of the bushing or changes in the normal direction. Therefore, in a further solution, the detection module further includes a measuring indenter. The measuring indenter is connected to the lower end of the bushing through a bushing sleeve. The upper end of the measuring indenter is in spherical contact with the lower end of the bushing. At least three feet are provided at the lower end of the measuring indenter and are rotationally symmetric about the axis of the measuring indenter. The feet extend beyond the lower end of the detection rod. Since the measuring indenter is in spherical contact with the bushing, when the measuring indenter is pressed against the surface of the part, the measuring indenter can rotate under the action of the curved surface, enabling the feet to stably contact the curved surface, thereby ensuring the stability of the bushing during the measurement process and the accuracy of the measurement.

[0037] The specific structural form of the spherical contact between the bushing and the measuring indenter is that the inner side of the lower end of the bushing and the outer side of the upper end of the measuring indenter are provided with matching arc chamfers. The center of the arc chamfer is the intersection point of the axis of the measuring indenter and the plane where the bottom of the feet is located. This structural form makes it easier for the bushing and the measuring indenter to rotate, thereby better compensating for the normal deviation of the countersink and the measuring tool.

[0038] The position sensor in the metering module can have various forms, such as a capacitive sensor, a photoelectric sensor, or a pressure sensor, etc. To simplify the structure and ensure high precision at the same time, the position sensor of the present invention is preferably an encoder. A measurement target is provided on the drive rod, and a mounting plate for installing the encoder is provided on the sleeve. An encoder reading head for detecting the position of the measurement target is provided on the inner side of the mounting plate. By utilizing the relative movement between the measurement target and the encoder reading head, the displacement of the drive rod relative to the sleeve can be obtained.

[0039] For countersinks of different sizes and depths, different measuring heads are usually required for measurement. Therefore, to facilitate the replacement of different detection rods, the lower end of the sleeve is detachably connected to the detection rod through an adapter. A second compression spring is provided between the upper end of the drive rod and the upper end of the sleeve, and under the action of the elastic force, the lower end of the drive rod is in contact with the upper end of the measuring rod. The second compression spring can ensure that the drive rod is always in stable contact with the measuring rod, avoiding gaps between the two and causing measurement errors.

[0040] For the feeding module, its main function is to control the lifting of the detection rod and the moving distance is very short. Therefore, the linear feeding mechanism of the feeding module can preferably be a lead screw and nut transmission mechanism, which can achieve precise control of the feeding amount.

[0041] During the automatic hole-making process, it is sometimes also required to detect the hole diameter. Therefore, in order to improve the detection efficiency, the present invention integrates the hole diameter measurement and countersink measurement together, and can simultaneously perform the accuracy detection of the countersink and hole diameter at one time. The specific structure is as follows: a thimble passing through the lower end of the detection rod is provided at the lower end of the measuring rod, and a hole diameter detection head is provided at the lower end of the detection rod. The hole diameter detection head includes a guide post and two probe heads located at the end of the guide post. The probe heads can slide radially along the guide post, and their inner ends are respectively connected to a petal-shaped probe. A measuring needle that can move up and down as the petal-shaped probe is squeezed and relaxed is provided in the middle of the two petal-shaped probes. The upper end of the measuring needle is connected to the thimble at the lower end of the measuring rod; the through hole for the communication shaft to pass through in the middle of the measuring rod is a strip-shaped hole arranged along the length direction of the measuring rod, and in the natural state, the communication shaft is located in the middle and lower part of the strip-shaped hole.

[0042] The measurement process of the hole diameter and countersink diameter is as follows: during the process of the feeding module driving the detection module to move downward, when the pressing foot of the measuring indenter just contacts the surface of the part, it is used as the initial state, and all other parts are in a free state without any external stress applied. At this time, the communication shaft is located in the middle and lower part of the strip-shaped hole on the measuring rod; then the detection module continues to move downward, and all parts except the bushing and the measuring indenter move downward synchronously until the communication shaft contacts the upper end of the strip-shaped hole. During this process, the hole diameter detection head has extended into the drilled hole, and the measuring needle moves upward under the extrusion of the probe head, and at the same time, the measuring rod is jacked upward through the thimble, and the encoder head can read the precise position of the measurement target, so as to judge whether the hole diameter is qualified; finally, the detection module continues to move downward. Since the communication shaft has already contacted the upper end of the strip-shaped hole of the measuring rod, during the subsequent movement process, the measuring rod, the drive shaft and the measurement target will remain stationary together with the communication shaft and the bushing, while the detection rod and the sleeve will continue to move downward until the conical head at the lower end of the detection rod contacts the edge of the countersink diameter. The encoder reads the position of the measurement target again, and the system calculates the difference from the reference value and converts the diameter or depth of the entire countersink. This process needs to consider compensating for the displacement of the measurement target during the previous hole diameter measurement. Therefore, by one feeding, the measurement of the hole diameter and countersink diameter can be realized successively, greatly improving the detection efficiency.

[0043] The reason for setting the strip-shaped hole on the measuring rod and making the communication shaft located in the middle and lower part of the strip-shaped hole is mainly to reserve more space during the hole diameter measurement process so that the hole diameter detection head can extend into the hole.

[0044] During the aperture measurement process, generally two aperture measurements are required. After the initial measurement, the aperture detection head needs to be rotated by 90° and then the second measurement is carried out to ensure that no elliptical hole is formed. Therefore, it also includes a rotation module. The rotating shaft of the rotation module is connected to the upper end of the sleeve of the metering module through two flange plates, and a plurality of shear columns are connected between the two flange plates. The shear columns have a large axial stiffness and a small radial stiffness. Therefore, the mechanism can achieve a certain amount of deformation compensation for concentricity in the radial direction of the shear columns, while the deformation in the axial direction and the influence on the normal direction of the overall mechanism can be ignored. By setting the shear columns, a certain amount of movement can be achieved in the radial direction for the entire detection module and the metering module, which plays a certain compensation role for the conical head and the aperture detection head, ensuring the concentricity of the two with the countersunk hole to be measured, thereby ensuring the measurement accuracy.

[0045] The beneficial effects of the present invention are:

[0046] 1. By adopting the measurement method of the present invention, the deviation of the countersunk hole diameter can be converted into the change of the height position of the measurement head. By detecting the position of the measurement head, it can be quickly judged whether the countersunk hole is qualified. Moreover, the material powder generated by drilling mainly covers the surface of the countersunk hole and covers less at the edge of the countersunk hole. Therefore, by measuring the diameter of the countersunk hole, the interference of material factors on the measurement can be effectively avoided, and the measurement accuracy is improved;

[0047] 2. For the measuring tool, the present invention uses a bushing as a support member, limits the positions of the measuring rod and the driving rod through a connecting shaft and uses this as a measurement reference, and then moves the detection rod downward to make the detection rod have a relative displacement with the measuring rod, so as to accurately measure the position change of the detection rod relative to the measuring rod when it contacts the edge of the countersunk hole, and then deduce the deviation amount of the countersunk hole diameter; the overall structure is ingeniously designed, and the connection between components is compact and reliable, which is conducive to the miniaturization of the equipment; the fine moving components are all protected inside the structure, which can reduce the influence of the external environment and ensure the stability and accuracy of the long-term operation of the measuring tool;

[0048] 3. A measurement pressure head that contacts the bushing through a spherical surface is arranged at the lower end of the bushing. When the measurement pressure head is pressed on the surface of the part, the measurement pressure head can rotate under the action of the curved surface, which plays a compensation role for the normal deviation between the countersunk hole and the measuring tool, so that the pressure foot can stably contact the curved surface part, thereby ensuring the stability of the bushing during the measurement process and the accuracy of the measurement;

[0049] 4. By arranging an aperture detection head below the conical head of the detection rod and cooperating with a strip hole arranged on the measuring rod, the aperture measurement process and the hole diameter measurement process do not interfere with each other, and the detection of the aperture and the hole diameter can be successively realized in one feeding process, greatly improving the detection efficiency. Description of the Drawings

[0050] Figure 1It is the schematic diagram of the measurement principle of the present invention;

[0051] Figure 2 It is the overall structural schematic diagram of the measuring tool of the present invention;

[0052] Figure 3 It is the sectional view of the measuring tool of the present invention;

[0053] Figure 4 It is the schematic diagram of the measurement process of the present invention;

[0054] Figure 5 It is the structural schematic diagram of the aperture detection head of the present invention;

[0055] In the figure, the markings are: 1 - detection module, 2 - metering module, 3 - feeding module, 4 - rotating module, 5 - flange, 6 - shear column, 11 - detection rod, 12 - measuring rod, 13 - bushing, 14 - connecting shaft, 15 - first compression spring, 16 - measuring indenter, 17 - sleeve, 18 - aperture detection head, 21 - sleeve, 22 - driving rod, 23 - measurement target, 24 - mounting plate, 25 - encoder head, 26 - adapter, 27 - second compression spring, 111 - conical head, 112 - long slot, 121 - strip hole, 161 - pressing foot, 181 - guiding column, 182 - probe head, 183 - petal probe, 184 - probe needle. Specific embodiments

[0056] The present invention will be further described below with reference to the accompanying drawings.

[0057] As Figure 1 shown, for the countersink accuracy measurement method of the present invention, a measuring head with a conical angle at the front end and a detector that can accurately detect the height position of the measuring head are used as the measuring tool. The conical angle α of the measuring head needs to be greater than the chamfer angle β of the countersink to be measured;

[0058] The measurement process includes the following steps:

[0059] S1. Place the measuring head directly above the countersink, ensure that their axes are aligned, and determine a zero position of the measuring head through the detector;

[0060] S2. Select a standard countersink as the measurement reference, with its hole diameter defined as D0. Move the measuring head downward from the zero position until the conical surface of the bottom conical angle contacts the outer edge of the hole diameter of the countersink, and record the height H0 of the measuring head's descent through the detector;

[0061] S3. Use the method of S2 to detect the countersink to be measured, record the height H1 of the measuring head's descent from the zero position, and assume that the hole diameter of this countersink is D1;

[0062] S4. Calculate the measurement parameters according to the following process:

[0063] ΔH = H0 - H1,

[0064] ΔD = D1 - D0,

[0065] tan(α / 2) = (D0 / 2) / (t - H0) = (D1 / 2) / (t - H1),

[0066] In the formula, t is the distance from the zero position to the vertex of the measuring head cone angle, which will be cancelled out during the calculation process. After converting the above formula, we get:

[0067] ΔD = 2tan(α / 2) * ΔH;

[0068] S5. ΔD is the actual deviation value of the countersink diameter. Compare it with the tolerance requirement of the countersink diameter to determine whether the countersink is qualified.

[0069] This measurement method can convert the deviation of the countersink diameter into the change of the height position of the measuring head. By detecting the position of the measuring head, it can quickly determine whether the countersink is qualified. And the material powder generated by drilling mainly covers the surface of the countersink and covers less at the edge of the countersink. Therefore, by measuring the countersink diameter, the interference of material factors on the measurement can be effectively avoided. As for how the measuring tool moves the measuring head and detects the position, there are currently many linear feed mechanisms with position sensors that can achieve this function. According to this detection principle, a small manual measuring instrument can be made, or it can be integrated into the currently commonly used automatic hole-making equipment. The spindle of the automatic hole-making equipment itself has the functions of linear feed and position detection.

[0070] If the qualified judgment standard of the countersink is the countersink depth, the calculation process in S4 is as follows:

[0071] Δh = h1 - h0,

[0072] tan(β / 2) = (D1 / 2) / (h1 + T) = (D0 / 2) / (h0 + T) = (d1 / 2) / T,

[0073] h0 = 0.5 * (D0 - d1) / tan(β / 2),

[0074] h1 = 0.5 * (D1 - d1) / tan(β / 2),

[0075] In the formula, h0 is the standard countersink depth, h1 is the actual countersink depth, Δh is the actual deviation value of the countersink depth, and T is the distance from the lower edge of the countersink to the vertex of the countersink cone surface, which will be cancelled out during the calculation process. After converting the above formula, we get:

[0076] Δh = 0.5*(D1 - D0) / tan(β / 2) = 0.5*ΔD / tan(β / 2)

[0077] = tan(α / 2) *ΔH / tan(β / 2),

[0078] Δh is the actual deviation value of the countersink depth, which can be directly compared with the tolerance requirement of the countersink depth to judge whether the countersink is qualified. Similarly, by detecting the position of the measuring head, the countersink depth can be obtained, and then it can be judged whether the countersink is qualified.

[0079] For measuring tools, such as Figure 2 、 Figure 3 As shown, the solution adopted by the present invention is that the measuring tool includes a detection module 1, a metering module 2 and a feeding module 3;

[0080] The detection module 1 includes a detection rod 11, a measuring rod 12, a bushing 13 and a connecting shaft 14. The lower end of the detection rod 11 is provided with a conical head 111, the cone angle of which should be greater than the chamfer angle of the measured countersink, and the outer diameter of its large end should be greater than the countersink diameter. The measuring rod 12 is slidably installed in the detection rod 11. The bushing 13 is slidably sleeved outside the lower half of the detection rod 11. The lower half of the detection rod 11 is provided with a long hole 112 arranged along its length direction, and the length of the long hole 112 should meet the detection range of the detection rod 11. Through holes are provided on both the measuring rod 12 and the bushing 13. The connecting shaft 14 sequentially passes through one side of the bushing 13, the detection rod 11, the measuring rod 12 and the other side of the bushing 13, and both ends are fixed on the through holes of the bushing 13. A first compression spring 15 is provided between the upper end of the bushing 13 and the upper end of the measuring rod 12. Under the action of the elastic force, the connecting shaft 14 contacts the lower end of the long hole 112 on the detection rod 11, and the lower end of the bushing 13 exceeds the lower end of the detection rod 11;

[0081] The metering module 2 is arranged at the upper end of the detection rod 11, and includes a sleeve 21 coaxial with the detection rod 11 and a driving rod 22 slidable along the axis of the sleeve 21, and a position sensor installed on the sleeve 21 for detecting the position of the driving rod 22. The upper end of the measuring rod 12 contacts or connects with the lower end of the driving rod 22;

[0082] The feeding module 3 includes a linear feeding mechanism that can drive the detection module 1 and the metering module 2 to move linearly.

[0083] The measuring process of this measuring tool is as follows: First, make the lower end of the bushing 13 contact with the workpiece surface, and ensure that the axis of the detecting rod 11 is coaxial with the axis of the countersink. Then, move the detecting rod 11 downward. Due to the existence of the long slot 112, the detecting rod 11 can move downward relative to the bushing 13. The length of the long slot 112 should be such that until the tapered head 111 of the detecting rod contacts the outer edge of the countersink, the connecting shaft 14 does not contact the upper end of the long slot 112. During this process, the sleeve 21 and the position sensor will move downward together with the detecting rod 12. Since the bushing 13 is in contact with the workpiece surface and the measuring rod 12 is connected to the bushing 13 through the connecting shaft 14, the measuring rod 12 and the driving rod 22 are fixed. Until the tapered surface of the tapered head 111 at the lower end of the detecting rod 11 contacts the outer edge of the countersink, the detecting rod 11 stops moving, and the position sensor will record the distance it moves relative to the measuring rod 12 along with the detecting rod 11. By detecting the standard countersink and the actual countersink, the values of H0 and H1 mentioned above can be obtained respectively, so as to obtain ΔH and ΔD, and then judge whether the countersink is qualified. The value of H0 has been recorded during the system calibration stage, and the system can directly compare with it during subsequent detection, so as to directly judge whether the actual countersink is qualified.

[0084] This measuring tool can be used alone or in combination with an automatic hole-making device. To ensure the measuring accuracy, it is necessary to control the normal state, that is, to ensure that the axis of the detecting rod 11 is as coaxial as possible with the axis of the countersink. For the countersink on a plane, it is easy to control the normal state when using this measuring tool alone. If it is a curved surface, it is best to install it on the spindle of the automatic hole-making device and use the normal function of the spindle of the automatic hole-making device to determine the normal state of the detecting rod, so as to improve the measuring accuracy. Integrating this measuring tool into the automatic hole-making device can also automatically and real-time measure the depth of the countersink after hole-making, and perform recording, storage or transmission, etc., which is convenient for collection and traceability.

[0085] For parts with curved surfaces, if the bushing 13 is directly in contact with the curved surface part, it may cause instability of the bushing 13 or changes in the normal direction, affecting the subsequent measurement accuracy. Therefore, a further solution is that the detection module 1 further includes a measuring indenter 16. The measuring indenter 16 is connected to the lower end of the bushing 13 through a bushing 17. The upper end of the measuring indenter 16 is in spherical contact with the lower end of the bushing 13. At least three pressing feet 161 that are rotationally symmetric about the axis of the measuring indenter 16 are provided at the lower end of the measuring indenter 16, and the pressing feet 161 extend beyond the lower end of the detection rod 11. The bushing 17 can be made of plastic material and is not sealed, and is used to wrap the lower end of the bushing 13 and the spherical surface of the measuring indenter 16. Since the measuring indenter 16 is in spherical contact with the bushing 13, when the measuring indenter 16 is pressed on the surface of the part, the measuring indenter 16 can rotate under the action of the curved surface, compensating for the normal deviation between the countersunk hole and the measuring tool, so that the pressing feet 161 can stably contact the curved surface, thereby ensuring the stability of the bushing 13 during the measurement process and the accuracy of the measurement. In addition, the bottom of the pressing feet 161 can be designed to be arc-shaped, making line contact with the measured countersunk hole plane. During measurement, the composite material powder on the contact surface can be pushed away, reducing the influence of the composite material powder on the measurement error.

[0086] The specific structural form of the spherical contact between the bushing 13 and the measuring indenter 16 is that the inner side of the lower end of the bushing 13 and the outer side of the upper end of the measuring indenter 16 are provided with matching arc chamfers, and the center of the arc chamfer is the intersection point of the central axis of the measuring indenter 16 and the plane where the bottom of the pressing feet 161 is located. This structural form makes it easier for the bushing 13 and the measuring indenter 16 to rotate, thereby better compensating for the normal deviation between the countersunk hole and the measuring tool.

[0087] The position sensor in the metering module 2 can have various forms, such as a capacitive sensor, a photoelectric sensor, or a pressure sensor, etc. To simplify the structure and ensure high precision at the same time, the position sensor of the present invention preferably uses an encoder. A measurement target 23 is provided on the driving rod 22, and a mounting plate 24 for installing the encoder is provided on the sleeve 21. An encoder read head 25 for detecting the position of the measurement target 23 is provided on the inner side of the mounting plate 24. The measurement target 23 can be a strip-shaped magnetic grating, and the encoder read head 25 reads the magnetic grating data to obtain the relative displacement amount between the two, that is, the relative displacement amount between the driving rod 22 and the sleeve 21.

[0088] For countersinks of different sizes and depths, different measuring heads are usually required for measurement. Therefore, to facilitate the replacement of different detection rods 11, the lower end of the sleeve 21 is detachably connected to the detection rod 11 through an adapter 26. A second compression spring 27 is provided between the upper end of the drive rod 22 and the upper end of the sleeve 21, and under the action of elastic force, the lower end of the drive rod 22 contacts the upper end of the measuring rod 12. One end of the adapter 26 can be fixedly connected to the sleeve 21, and the other end is threadedly connected to the detection rod, which is convenient for replacement and ensures the reliability of the connection. The second compression spring 27 is mainly used to ensure that the drive rod 22 always stably contacts the measuring rod 12, avoiding gaps between the two and causing measurement errors.

[0089] For the feeding module 3, it is mainly used to control the lifting of the detection rod 11, and the moving distance is very short. Therefore, the linear feeding mechanism of the feeding module 3 preferably adopts a lead screw-nut transmission mechanism, and the precise movement of the detection rod 11 can be realized in cooperation with a linear guide rail and a stepping motor. In addition, the feeding module 3 usually knows in advance information such as the position and depth of the hole to be measured according to the workpiece digital model information and imports it into the hole-making / measurement program. During the measurement process, unless there is a collision or the measured value is too different from the theoretical value, the device will alarm. Generally, the feeding module 3 will work according to the pre-set process, which can ensure the precise movement of the feeding module 3, and generally does not require a feedback system.

[0090] During the automatic hole-making process, sometimes it is also required to detect the hole diameter. Therefore, to improve the detection efficiency, the present invention integrates the hole diameter measurement and the countersink measurement together, and can simultaneously perform the precision detection of the countersink and the hole diameter during detection. The specific structure is as Figure 3 、 Figure 5 shown: A thimble passing through the lower end of the detection rod 11 is provided at the lower end of the measuring rod 12. An aperture detection head 18 is provided at the lower end of the detection rod 11. The aperture detection head 18 includes a guide post 181 and two probe heads 182 located at the end of the guide post 181. The probe heads 182 can slide radially along the guide post 181, and their inner ends are respectively connected to a petal-shaped probe 183. A measuring needle 184 that can move up and down as the petal-shaped probes 183 are squeezed and expanded is provided in the middle of the two petal-shaped probes 183. The upper end of the measuring needle 184 is connected to the thimble at the lower end of the measuring rod 12; The through hole for the communication shaft 14 to pass through the middle of the measuring rod 12 is a strip-shaped hole 121 arranged along the length direction of the measuring rod 12, and in the natural state, the communication shaft 14 is located in the lower middle part of the strip-shaped hole 121.

[0091] The measurement processes of the hole diameter and the countersink diameter are as Figure 4As shown: During the process of the feed module 3 driving the detection module 1 to move downward, when the pressing foot 161 of the measuring indenter 16 just contacts the surface of the part, it is taken as the initial state, and all other parts are in a free state without any external stress applied. At this time, the connecting shaft 14 is located in the middle and lower part of the strip-shaped hole 121 on the measuring rod 12; then the detection module 1 continues to move downward. Except for the bushing 13 and the measuring indenter 16, the rest of the components move downward synchronously until the connecting shaft 14 contacts the upper end of the strip-shaped hole 121. During this process, the hole diameter detection head 18 has extended into the drilled hole, and the probe 184 moves upward under the extrusion of the probe head 182. At the same time, the measuring rod 12 is pushed upward by the ejector rod, and the encoder head 25 can read the precise position of the measurement target 23, thereby judging whether the hole diameter is qualified; finally, the detection module 1 continues to move downward. Since the connecting shaft 14 has already contacted the upper end of the strip-shaped hole 121 of the measuring rod 12, during the subsequent movement process, the measuring rod 12, the drive shaft 22, and the measurement target 23 will remain stationary together with the connecting shaft 14 and the bushing 13, while the detection rod 11 and the sleeve 21 will continue to move downward until the conical head 111 at the lower end of the detection rod 11 contacts the edge of the counterbore diameter. The encoder head 25 reads the position of the measurement target 23 again, and the system calculates the difference from the reference value and converts it into the diameter or depth of the entire counterbore. This process needs to consider compensating for the displacement of the measurement target during the previous hole diameter measurement. Therefore, by one feed, the measurement of the hole diameter and the counterbore diameter can be achieved successively, greatly improving the detection efficiency.

[0092] The reason for setting the strip-shaped hole on the measuring rod 12 and making the connecting shaft 14 located in the middle and lower part of the strip-shaped hole 121 is mainly to reserve more space during the hole diameter measurement process so that the hole diameter detection head 18 can extend into the hole. Because usually the tolerance range of the hole diameter and the counterbore diameter is only about 0.03 mm. To ensure precise measurement, there are also length limitations for the overall mechanism. Usually, the range of the encoder is relatively small. The range currently used in the present invention is only 4 mm. If there is no strip-shaped hole 121, the displacement of the entire mechanism during the counterbore measurement is very likely to exceed the range of the encoder. Therefore, having a larger sliding distance at the upper end of the connecting shaft 14 can be used to reduce the movement amount of the measured target during the counterbore measurement.

[0093] During the aperture measurement process, generally two aperture measurements are required. After the initial measurement, the aperture detection head 18 needs to be rotated by 90° and then the second measurement is carried out to ensure that no elliptical hole is formed. Therefore, it also includes a rotation module 4. The rotating shaft of the rotation module 4 is connected to the upper end of the sleeve 21 of the metering module 2 through two flange plates 5, and the two flange plates 5 are connected by a plurality of shear columns 6. The rotation module 4 can be driven by a stepping motor or a rotary cylinder. The shear column 6 has a large axial stiffness and a small radial stiffness, so it can achieve a certain amount of deformation compensation for concentricity in the radial direction of the mechanism at the shear column 6, while the deformation in the axial direction and the influence on the normal direction of the overall mechanism can be ignored. By setting the shear column 6, a certain amount of movement can be provided in the radial direction for the entire detection module 1 and the metering module 2, which plays a certain compensation role for the conical head 111 and the aperture detection head 18, ensuring the concentricity between the two and the countersunk hole to be measured, thereby guaranteeing the measurement accuracy.

Claims

1. Countersinking accuracy measurement method, characterized by: It includes a measuring tool, and the measuring tool includes a detection module (1), a metering module (2) and a feeding module (3); the detection module (1) includes a detection rod (11), a measuring rod (12), a bushing (13) and a connecting shaft (14). A conical head (111) is provided at the lower end of the detection rod (11). The measuring rod (12) is slidably installed inside the detection rod (11). The bushing (13) is slidably sleeved outside the lower half of the detection rod (11). A long hole (112) arranged along its length direction is provided in the lower half of the detection rod (11). Through holes are provided on both the measuring rod (12) and the bushing (13). The connecting shaft (14) sequentially passes through one side of the bushing (13), the detection rod (11), the measuring rod (12) and the other side of the bushing (13), and both ends are fixed on the through holes of the bushing (13). A first compression spring (15) is provided between the upper end of the bushing (13) and the upper end of the measuring rod (12). Under the action of elastic force, the connecting shaft (14) contacts the lower end of the long hole (112) on the detection rod (11), and the lower end of the bushing (13) exceeds the lower end of the detection rod (11); the metering module (2) is arranged at the upper end of the detection rod (11), and includes a sleeve (21) coaxial with the detection rod (11) and a driving rod (22) slidable along the axis of the sleeve (21), and a position sensor installed on the sleeve (21) for detecting the position of the driving rod (22). The upper end of the measuring rod (12) contacts or is connected to the lower end of the driving rod (22); the feeding module (3) includes a linear feeding mechanism capable of driving the detection module (1) and the metering module (2) to move linearly. Using the conical head (111) as the measuring head, the cone angle α of which is greater than the chamfer angle β of the counterbored hole to be measured, and using the metering module (2) as the detector for detecting the height position of the measuring head, the measuring process includes the following steps: S1. Place the measuring head directly above the counterbored hole, ensure that their axes are aligned, and determine a zero position of the measuring head through the detector. S2. Select a standard counterbored hole as the measuring reference, with its hole diameter defined as D0. Move the measuring head downward from the zero position until the conical surface of its bottom cone angle contacts the outer edge of the hole diameter of the counterbored hole, and record the height H0 of the measuring head's descent through the detector. S3. Use the method of S2 to detect the counterbored hole to be measured, record the height H1 of the measuring head's descent from the zero position, and assume the hole diameter of this counterbored hole is D1. S4. Calculate the measurement parameters according to the following process: ΔH = H0 - H1, ΔD = D1 - D0, tan(α / 2) = (D0 / 2) / (t - H0) = (D1 / 2) / (t - H1), In the formula, ΔH is the height difference of the measuring head in the two measurements, ΔD is the actual deviation value of the counterbored hole diameter, and t is the distance from the zero position to the vertex of the measuring head's cone angle, which will be cancelled out during the calculation process. After converting the above formula, we get: ΔD = 2tan(α / 2) * ΔH; S5. Compare the value of ΔD with the tolerance requirement of the counterbored hole diameter to determine whether the counterbored hole is qualified.

2. The countersinking accuracy measurement method according to claim 1, wherein: If the criterion for countersinking qualification is the countersinking depth, the calculation process in S4 is as follows: Δh = h1 - h0, tan(β / 2) = (D1 / 2) / (h1 + T) = (D0 / 2) / (h0 + T) = (d1 / 2) / T, h0 = 0.5*(D0 - d1) / tan(β / 2), h1 = 0.5*(D1 - d1) / tan(β / 2), In the formula, h0 is the standard countersinking depth, h1 is the actual countersinking depth, Δh is the actual deviation value of the countersinking depth, and T is the distance from the lower edge of the countersinking to the vertex of the countersinking cone surface, which will be offset during the calculation process. After converting the above formula, we get: Δh = 0.5*(D1 - D0) / tan(β / 2) = 0.5*ΔD / tan(β / 2) = tan(α / 2) *ΔH / tan(β / 2), Compare the value of Δh with the tolerance requirement of the countersinking depth to determine whether the countersinking is qualified.

3. The countersinking accuracy measurement method according to claim 1, characterized in that: The detection module (1) further includes a measuring indenter (16). The measuring indenter (16) is connected to the lower end of the bushing (13) through a bushing (17). The upper end of the measuring indenter (16) is in spherical contact with the lower end of the bushing (13). At least three feet (161) that are rotationally symmetric about the axis of the measuring indenter (16) are provided at the lower end of the measuring indenter (16), and the feet (161) extend beyond the lower end of the detection rod (11).

4. The countersinking accuracy measurement method according to claim 3, characterized in that: Matched arc chamfers are provided on the inner side of the lower end of the bushing (13) and the outer side of the upper end of the measuring indenter (16). The center of the arc chamfer is the intersection of the central axis of the measuring indenter (16) and the plane where the bottom of the feet (161) is located.

5. The countersinking accuracy measurement method according to claim 1, characterized in that: The position sensor in the metering module (2) is an encoder. A measuring target (23) is provided on the driving rod (22). A mounting plate (24) for installing the encoder is provided on the sleeve (21), and an encoder head (25) for detecting the position of the measuring target (23) is provided on the inner side of the mounting plate (24).

6. The counterboring accuracy measurement method according to claim 5, characterized in that: The lower end of the sleeve (21) is detachably connected to the detection rod (11) through a adapter (26). A second compression spring (27) is provided between the upper end of the driving rod (22) and the upper end of the sleeve (21), and under the action of the elastic force, the lower end of the driving rod (22) is in contact with the upper end of the measuring rod (12).

7. The method for measuring the accuracy of countersinking according to claim 1, characterized in that: The linear feed mechanism of the feed module (3) is a lead screw and nut drive mechanism.

8. The counterboring accuracy measurement method according to claim 6, characterized in that: A push rod passing through the lower end of the detection rod (11) is provided at the lower end of the measuring rod (12). An aperture detection head (18) is provided at the lower end of the detection rod (11). The aperture detection head (18) includes a guide post (181) and two probe heads (182) located at the end of the guide post (181). The probe heads (182) can slide radially along the guide post (181), and their inner ends are respectively connected to a flap probe (183). A measuring needle (184) that can move up and down as the flap probe (183) is squeezed and relaxed is provided in the middle of the two flap probes (183). The upper end of the measuring needle (184) is connected to the push rod at the lower end of the measuring rod (12). The through hole for the communication shaft (14) to pass through in the middle of the measuring rod (12) is a strip-shaped hole (121) arranged along the length direction of the measuring rod (12). In the natural state, the communication shaft (14) is located in the lower middle part of the strip-shaped hole (121).

9. The countersinking accuracy measurement method according to claim 8, characterized in that: It further includes a rotation module (4). The rotating shaft of the rotation module (4) is connected to the upper end of the sleeve (21) of the metering module (2) through two flange plates (5), and the two flange plates (5) are connected by a plurality of shear columns (6).

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