A method and device for on-line measurement of geometric parameters of a circular cross-section shaft part

Abstract

The application discloses a kind of circular cross section shaft parts geometric parameter on-line measurement method and device, belong to geometric quantity precision measurement technical field.The device includes pedestal, part conveying mechanism, length measurement and support mechanism, rotary drive mechanism, gantry support frame, multiple displacement sensors, multiple motors, data acquisition and processing system.Rotary drive mechanism driving support wheel has high friction coefficient to provide stable driving force, driven support wheel has low friction coefficient to reduce rotation resistance.When measuring, part rotates at constant speed, realizes spiral scanning sampling;Sensor can be contact or non-contact, to adapt to different material and surface state parts;Data processing stage is preprocessed to the data collected, digital filtering, gravity compensation, calculates the diameter, length, straightness and coaxiality of part.The application can measure multiple geometric parameters synchronously, suitable for machine tool spindle, stepped shaft, crankshaft, boring bar, transmission shaft and other various circular cross section shaft parts, with the advantages of high measurement efficiency, good precision, high degree of automation, strong adaptability etc.

Description

Technical Field

[0001] This invention belongs to the field of precision geometric measurement technology, specifically relating to an online measurement method and device for geometric parameters (such as diameter, length, straightness, cylindricity, taper, coaxiality, etc.) of circular cross-section shaft parts, which has wide applications in industrial production lines. Background Technology

[0002] In fields such as machinery manufacturing, automotive industry, aerospace, and heavy machinery, circular cross-section shaft parts are widely used as key transmission and support components. For example, machine tool spindles are core components of precision machining equipment, and their geometric accuracy directly affects the quality of machining and application; boring bars, as key components of boring machines, have extremely strict requirements for straightness error; the coaxiality accuracy of each section of a stepped shaft has a significant impact on assembly quality and service life; crankshafts, as core components of engines, have parameters such as journal roundness and coaxiality between main journals and connecting rod journals that directly affect engine performance and reliability. The diameter, length, straightness, coaxiality, and roundness of these shaft parts are key indicators for evaluating product quality, requiring rigorous factory quality inspection and process quality control.

[0003] Various methods exist for measuring geometric parameters, each with its own advantages and disadvantages. For example, using a single laser diameter gauge in conjunction with workpiece rotation can measure the diameter and ellipticity of a cross-section, but it is difficult to simultaneously and efficiently obtain straightness information along the entire length. Another approach is to use multiple diameter gauges in a fixed arrangement. While this can measure the diameter of moving bars, it is difficult to accurately assess straightness errors for slender bars due to changes in their axis caused by their own weight or bending. We propose an integrated solution that balances measurement efficiency and accuracy, enabling online, synchronous, and high-precision measurement of the diameter, length, and straightness of circular cross-section shaft parts, while effectively eliminating the influence of gravity and mechanical errors. Summary of the Invention

[0004] Based on a comprehensive consideration of factors such as measurement efficiency and measurement accuracy, the technical solution provided by this invention is as follows:

[0005] An online measurement device for geometric parameters of circular cross-section shaft parts includes a base, a part conveying mechanism, a length measuring and support mechanism, a rotary drive mechanism, a gantry support frame, a moving measuring mechanism, multiple displacement sensors, multiple motors, and a data acquisition and processing system.

[0006] in,

[0007] The base is used to provide a stable installation foundation and is made of materials with good rigidity and stability, such as granite and cast iron.

[0008] The parts conveying mechanism is mounted on the base and is used to convey shaft-type parts with circular cross-sections to be tested;

[0009] The length measurement and support mechanism includes a length measurement support groove, multiple sensors, and multiple adjustable sensor support frames. Sensor 1 and Sensor 2 are respectively arranged on the sensor support frames on both sides of the length measurement support groove, and are used to measure the length of the circular cross-section shaft part to be measured. The position of the sensor support frames is adjustable to accommodate shaft parts of different lengths. After sensors 1 and 2 detect the positions of the two end faces of the part, the data acquisition system records the axial position coordinates x1 and x2 corresponding to the two end faces. The total length L of the part is then calculated by the following formula:

[0010] L = |x2 - x1|

[0011] The rotary drive mechanism is positioned above the part conveying mechanism and is used to drive the shaft-like part to be tested to rotate around its axis. This rotary drive mechanism can be fixedly installed or position-adjustable installed to accommodate shaft-like parts of different diameters and lengths. Position-adjustable installation means that the relative positions of the driving and driven ends can be adjusted to change the shaft spacing between the support wheels, thereby accommodating shaft-like parts of different diameters and ensuring good contact between the drive wheels and the part surface. The overall height of the rotary drive mechanism relative to the base is adjustable to adjust the height position of the part's axis. The installation angle of the support wheels is adjustable to change the included angle of the V-groove or the tilt angle of the support wheels, thereby accommodating parts of different diameters and optimizing the contact state. This can be achieved through a lead screw and nut mechanism, a guide rail and slider mechanism, or a manual or automatic adjustment device.

[0012] The rotary drive mechanism includes an active end and a driven end. The active end includes an active support wheel and a driven support wheel. The active support wheel is connected to a motor and driven to rotate. The motor and the active support wheel can be connected by a coupling, a key, or via a synchronous belt, a belt, or a chain drive. The active support wheel is a roller with a surface coated with elastic materials such as rubber or polyurethane. Its material differs from that of the driven support wheel, absorbing vibration and improving rotational stability. The driven support wheel is made of ceramic bearings, metal bearings, or low-friction polymer materials, or its surface is coated with a material that reduces friction to reduce rotational resistance. The active and driven ends have a double-roller support structure, mounted on roller support frames on both sides, including one or more sets of roller pairs. The axial or radial spacing between the two rollers in each set of roller pairs is adjustable, ensuring that the axes of all support wheels included in the active and driven ends are at the same height and in the same plane.

[0013] The rotary drive mechanism is driven by an electric motor or other power source. When the driving support wheel is driven, it contacts the surface of the part and transmits torque through friction. The driving and driven ends can employ various types of roller pairs, such as V-shaped roller pairs or parallel roller pairs, to accommodate shaft parts of different shapes.

[0014] The bottom of the gantry support frame is bolted to the base. It can be a gantry structure, cantilever structure, or bridge structure, depending on the measurement range and spatial layout. A reciprocating sliding component is placed on the crossbeam of the gantry support frame.

[0015] The mobile detection mechanism is mounted on the sliding component and consists of one or more sensors, used to collect and measure the position data of the surface contour during the rotation of the part to be tested;

[0016] The data acquisition and processing system is connected to multiple sensors to synchronously acquire sensor signals, calculate geometric parameters such as diameter, length, and straightness of the part under test based on the acquired data, and perform a series of data processing steps.

[0017] The data processing includes data trimming, horizontal correction, digital filtering, straightness calculation, diameter calculation, coaxiality calculation, and length calculation. Data trimming involves cutting out the data of the effective measurement area from the original data based on the actual measurement range of the part, removing irrelevant information such as the support mechanisms at both ends; linear correction is performed on the trimmed data to make the values ​​at both ends equal, eliminating baseline tilt caused by installation errors; a finite impulse response or infinite impulse response digital bandpass filter is used to extract signal components near the rotation frequency of the part, filtering out low-frequency deflection signals caused by gravity, low-frequency error signals caused by the rotation of the drive mechanism, and high-frequency noise. The output of the filter can be expressed as:

[0018]

[0019] For each measurement cross-section, the cross-section diameter is calculated based on the surface distance or position data measured by the sensor, combined with calibration parameters. If multiple sensors are used, the average diameter can be calculated. Let r be a set of radii measured at a certain cross-section. i (θ), then the diameter D of the cross section is:

[0020] Extract the coordinates of the center points of all measured sections, and fit the ideal axis using the two endpoints method, the least squares method, or the minimum bounding region method. Let the fitted ideal axis be a straight line L in space, then the distance from the center of each section to L is d. i The straightness error f is twice the maximum distance:

[0021]

[0022] For stepped or multi-step shaft parts, the coordinates of the center point of each shaft segment's cross-section are extracted, and the ideal axis of each shaft segment is fitted. Let the reference axis be L, and the distance from the center of each shaft segment to L be e. j Then the coaxiality error φ is twice the maximum deviation distance:

[0023]

[0024] Finally, based on the measurement results, the parts to be measured are divided into qualified and unqualified parts. Let the measurement error of a certain parameter be δ, and the tolerance zone be T, then the following grade classification can be defined:

[0025]

[0026] Beneficial effects

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention achieves scanning measurement by combining rotational drive and axial movement with a sensor. Multiple geometric parameters such as diameter, length, straightness, and coaxiality can be acquired simultaneously in a single scan, resulting in high measurement efficiency.

[0029] By employing an adjustable rotary drive mechanism and support mechanism, it can adapt to shaft parts of different diameters, lengths and shapes, making it highly versatile;

[0030] By employing different active and driven support wheels, an optimized combination of stable drive and low-resistance rotation is achieved;

[0031] It is compatible with both contact and non-contact sensors, and can be flexibly selected according to the shape, surface condition and accuracy requirements of the measured part, making it highly adaptable;

[0032] It can achieve fully automatic online measurement, automatically store and analyze measurement data, and automatically sort and grade quality according to preset tolerances. It is suitable for automated production lines and can significantly improve quality control and production efficiency. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the online detection structure described in this invention.

[0034] In the diagram: 1-base, 2-part conveying mechanism, 3-part to be tested, 4-gantry support frame, 5-motor 1, 6-sliding component, 7-moving detection mechanism, 8-sensor 1, 9-sensor 2, 10-sensor support frame 1, 11-sensor support frame 2, roller support frame 2, 12-rotation drive mechanism, 13-roller support frame 1, 14-roller support frame 2, 15-motor 2.

[0035] Figure 2 This is a flowchart illustrating an online method for measuring the geometric parameters of a circular cross-section shaft part, as provided in an embodiment of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Example 1

[0039] like Figure 1 As shown in the figure, the online measurement device for the geometric parameters of slender bars provided in this embodiment includes a high-rigidity base 1, on which a bar conveying mechanism 2 is installed to support and axially convey the part 3 to be measured.

[0040] A gantry support frame 4 consists of a crossbeam and two columns, with its bottom fixed to the base 1 by bolts. A motor 5 and a sliding component 6 are mounted on the crossbeam of the gantry support frame 4, and a moving detection mechanism 7 is mounted on the sliding component. The motor 5 drives a ball screw to rotate, which in turn drives the sliding component 6 to move precisely along a linear guide rail via the screw nut. In this embodiment, a laser displacement sensor is used. The sensor's measuring beam is perpendicular to the bar's axis and is used to detect the offset of the bar's cross-section center from the sensor reference point.

[0041] Displacement sensors 8 and 9 are installed near the two sides of the length measuring support groove. The sensors are fixed on sensor support frames 10 and 11. The sensors are small through-beam photoelectric sensors used to detect the end face position of the bar and then calculate the bar length.

[0042] The rotary drive mechanism 12 includes a driving end and a driven end. The driving end comprises a driving support wheel and a driven support wheel forming a V-shaped roller pair. The surface of the driving support wheel is coated with polyurethane, which has a high coefficient of friction and can provide sufficient driving force. It is connected to a stepper motor 15 and driven to rotate by the stepper motor 15. The distance between the driven support wheel and the driving support wheel can be adjusted manually. The driven end includes two support wheels, which use smooth ceramic bearings, have a low coefficient of friction and good self-lubricating properties, and can reduce rotational resistance, forming a driven V-shaped roller pair. The main roller pair and the driven roller pair are mounted on the roller support frames 13 and 14 on both sides. The axes of the support wheels included in the driving end and the driven end should be at the same height and ensured to be in the same plane.

[0043] The data acquisition and processing system is electrically connected to drivers and encoders of multiple displacement sensors, stepper motors, servo motors, and other components for synchronous control and data acquisition.

[0044] The measurement method is as follows: First, the displacement sensor is calibrated for zero point and measurement relationship. Then, the shaft part to be measured is placed on the part conveying mechanism and conveyed to the length measurement support groove. Subsequently, sensor 1 and sensor 2 detect the position of the two end faces of the part. After the length of the part is measured, the part is conveyed to the rotary drive mechanism. The motor is started to make the rotary drive mechanism drive the part to rotate at a constant speed. At the same time, the sliding part moves at a constant speed along the axial direction. The moving detection mechanism on the sliding part collects surface contour data synchronously. The data acquisition and processing system preprocesses, digitally filters, and compensates for gravity on the collected data, calculates the diameter and center coordinates of each section, and then evaluates geometric parameters such as straightness and coaxiality. Finally, the quality of the part is judged according to the measurement results, and the sorting mechanism automatically sorts qualified and unqualified products to realize the fully online automated measurement.

[0045] Example 2

[0046] This embodiment uses a stepped shaft with 3-5 steps as the measurement object, requiring the measurement of the diameter of each step, the length of each step, and the coaxiality of each step relative to the common axis of the center holes at both ends.

[0047] The device structure in this embodiment is basically the same as that in Embodiment 1, with the main difference being that the displacement sensor 4 uses two orthogonally arranged laser displacement sensors to measure the contour data in the horizontal direction (X-axis) and the vertical direction (Y-axis) respectively, in order to obtain the precise coordinates of the center of the cross-section. In addition, high-precision center hole positioning devices are provided at both ends of the part to establish the reference axis.

[0048] The measurement method is as follows: First, calibration and material positioning are performed, similar to the steps in Example 1. Then, during the scanning process, two orthogonal sensors synchronously collect data to obtain the X and Y boundary coordinates of each cross-section. During data processing, data preprocessing is performed first to cut out the effective measurement data for each step and identify the step transition position. Then, the diameter is calculated based on the cross-sectional data: for each step, the average diameter and ellipticity are calculated based on the X and Y diameters of each cross-section within the step's range. The length of each step and the total length are calculated based on the identified step transition position. The center coordinates of the cross-section are calculated: for each measured cross-section, the center coordinates of the cross-section are calculated based on the X and Y boundary coordinates. Next, a reference axis is established, using the line connecting the center holes at both ends as the reference axis, or using the common axis fitted by the center of the cross-sections of the support shaft segments at both ends as the reference axis. During coaxiality calculation, the center coordinates of each cross-section of the intermediate step are extracted, the distance from these centers to the reference axis is calculated, and twice the maximum distance is taken as the coaxiality error of the step relative to the reference. For multiple steps, the coaxiality error of each step is calculated separately, and the maximum value is taken as the coaxiality error of the part. At the same time, the coordinates of the center of all cross sections are extracted, and the ideal axis is fitted using the least squares method. The maximum distance from each center to the ideal axis is calculated as twice the overall straightness error of the part.

[0049] The description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An online measurement device for the geometric parameters of a circular cross-section shaft part, characterized in that, The device includes: Base, parts conveying mechanism, length measuring and support mechanism, rotary drive mechanism, gantry support frame, multiple displacement sensors, multiple motors, and data acquisition and processing system; A parts conveying mechanism is mounted on the base to convey and support the circular cross-section shaft parts to be measured. A length measuring and support mechanism is also mounted on the base, including a length measuring support groove, multiple sensors, and multiple adjustable sensor support frames. Sensor 1 and Sensor 2 are respectively arranged on the support frames on both sides of the length measuring support groove, used to measure the length of the circular cross-section shaft parts to be measured. A rotary drive mechanism is mounted on the base near the parts conveying mechanism to receive the parts to be measured from the conveying mechanism and drive the shaft parts to be measured to rotate around their axis. The rotary drive mechanism includes an active end and a driven end; the active end includes an active support wheel and a driven support wheel. The system includes a support wheel, with multiple driven support wheels on the driven end; a gantry support frame is placed on a base, and a reciprocating sliding component is placed on the crossbeam of the gantry support frame; a motion detection mechanism consists of one or more sensors mounted on the sliding component to acquire surface contour data or position data of the shaft-like parts; a motor 1 is placed at one end of the crossbeam and drives the sliding component to reciprocate through a transmission device; a motor 2 is placed on one side of the active end of the rotary drive mechanism to drive the active support wheel of the rotary mechanism; and a data acquisition and processing system is connected to the multiple sensors to synchronously acquire sensor signals and calculate the geometric parameters of the shaft-like parts based on the acquired data.

2. The measuring device according to claim 1, characterized in that, The sensors 1 and 2 used to measure the length of circular cross-section shaft parts can be arranged near the end face of the part to be measured, which can be the front, side, top, or bottom. The sensors are contact displacement sensors, non-contact displacement sensors, or image sensors, etc. The non-contact displacement sensors include one or more of the following: laser displacement sensors, ultrasonic sensors, capacitive sensors, photoelectric sensors, eddy current sensors, spectral confocal sensors, or vision sensors. The contact displacement sensors include one or more of the following: digital micrometer, inductive micrometer, grating micrometer, LVDT displacement sensor, or voltage transformer sensor.

3. The measuring device according to claim 1, characterized in that, The active support wheel at the driving end of the rotary drive mechanism has a higher coefficient of friction than the driven support wheel, and the active support wheel has a high coefficient of friction working surface, the surface material of which can be rubber or polyurethane, etc.; the driven support wheel at the driven end has a low coefficient of friction working surface, and is made of ceramic bearings, metal bearings or low coefficient of friction polymer materials; the rotary drive mechanism is fixed or position-adjustable to accommodate shaft parts of different diameters and lengths.

4. The measuring device according to claim 1, characterized in that, The transmission device can be a lead screw, synchronous belt, gear rack, linear motor, crank-slider mechanism, hydraulic cylinder, pneumatic cylinder, electromagnetic drive device, etc.

5. The measuring device according to claim 1, characterized in that, The connection methods of each mechanism are threaded connection, fixed by combination of locating pin and bolt, expansion sleeve connection, key connection, clamping and fixing connection, adhesive fixing connection, magnetic adsorption connection, etc.

6. The rotary drive mechanism according to claim 2, characterized in that, The active and driven ends are supported by a double roller type structure, including one or more sets of roller pairs. The axial or radial distance between the two rollers in each set of roller pairs can be adjusted by the distance adjustment mechanism.

7. The rotary drive mechanism according to claim 2, characterized in that, The rotary drive mechanism drives the part to rotate. There is a gap between the active support wheel and the driven support wheel at the active end, and the gap is adjustable. A motor or other power source drives the active support wheel to rotate, which in turn drives the part to rotate. The driven support wheel provides support. The motor and the active support wheel can be connected by a coupling, a key, or by a synchronous belt, a belt, or a chain drive.

8. An online measurement method for a device for online measurement of geometric parameters of circular cross-section shaft parts, characterized in that, Includes the following steps: S1 calibration steps: Within a certain period of time, the measuring device is calibrated for accuracy using standard parts. Specifically, the standard parts are placed on the length measuring support groove and the rotary drive mechanism, and the data is collected and standardized. S2 loading and length measurement steps: Place the circular cross-section shaft part to be measured on the part conveying mechanism and convey it to the length measurement support groove. Sensor 1 and sensor 2 start to detect the position of the two end faces of the part. S3 Length Data Acquisition and Processing Steps: The data acquisition and processing system acquires the readings of sensor 1 and sensor 2, processes the acquired data, and calculates the length of the part. After the length of the part is measured, the part is transported to the rotary drive mechanism. S4 Rotation and Movement Scanning Steps: When the part to be tested reaches the position of the rotation mechanism, start motor 2 to make the rotation drive mechanism drive the part to rotate. Then start motor 1 to drive the sliding component to move along the axis of the part, and the movement detection mechanism on the sliding component begins to detect. S5 mobile inspection mechanism data acquisition and processing steps: Process the acquired data to calculate parameters such as the diameter, straightness, or coaxiality of the parts.

9. The measurement method according to claim 8, characterized in that, The data processing in steps S3 and S5 includes: data cropping, horizontal correction, digital filtering, gravity compensation, straightness calculation, diameter calculation, coaxiality and length calculation, including extracting the center point coordinates of each measurement section, fitting the ideal axis of each axis segment, and calculating twice the maximum deviation distance of each axis segment axis from the reference axis as the coaxiality error.

10. The measurement method according to claim 8, characterized in that, Based on the measurement results, shaft parts are graded according to their quality to distinguish different levels of parts.

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