Large-sized gear machining accuracy measurement method

Abstract

A large-sized gear machining accuracy measurement method. The method comprises: measuring, by using a flexible articulated arm, the accuracy of a gear machined by means of a large-sized gear manufacturing machine tool; securing a standard spherical ball on a rotary table or a machine tool spindle headstock, and rotating the rotary table to a plurality of positions; then, measuring the centers of the standard spherical ball at different positions by using the flexible articulated arm, and fitting the coordinates of these centers to establish a workpiece coordinate system; and finally, on the basis of the established coordinate system, extracting points on a tooth surface, and evaluating the tooth profile, tooth lead and tooth pitch accuracy of the gear. By using the method, the machining accuracy of large-sized gears with diameters of 3,000 mm or above can be accurately evaluated in a workshop environment, thereby providing data support for the accuracy evaluation, installation and commissioning, error compensation, etc., of a large-sized gear manufacturing machine tool.

Description

A method for detecting machining accuracy of large-sized gears Technical Field

[0001] The present invention relates to a method for inspecting the machining accuracy of a gear-making machine tool, and more particularly to a method for inspecting the machining accuracy of large-size gears, and belongs to the field of high-end numerically controlled machine tools. Background Art

[0002] Currently, the market for precision testing of large-scale gears with diameters over 3000mm primarily relies on imported large-scale CMMs and gear gauges. These devices are expensive and require long procurement cycles, resulting in a severe shortage of large-scale gear precision testing equipment. This equipment is unable to meet the precision testing needs of large gears in industries such as wind power and construction machinery. The same problem also exists for the accuracy acceptance and error compensation of large-scale gear-making machine tools. Many large gear manufacturers rely solely on specialized manual measuring tools to measure parameters such as the normal, span, radial runout, tooth thickness, and pitch variation. This allows them to assess whether certain precision indicators, such as tooth thickness and pitch, meet requirements, but they are unable to accurately measure tooth profile and tooth guide deviations.

[0003] The finishing equipment for large-sized gears mainly includes CNC profile milling machines, CNC profile grinding machines, and gear hobbing machines. Profile milling machines are high-power cutting machines with large vibrations during cutting. They are generally not integrated into the machine measurement system. In the absence of large-scale three-coordinate measuring machines and gear inspection instruments, gear accuracy cannot be accurately measured. Profile grinding machines are generally integrated into the machine measurement system and mainly rely on the machine tool's own movement and high-precision probes to complete the measurement of tooth shape, tooth direction, tooth pitch, and tooth thickness. Their measurement accuracy also requires other testing methods to verify. Large profile grinding machines are generally used for high-precision hardened gear processing. They are also expensive and have relatively few testing resources.

[0004] Currently, the market lacks mature solutions for measuring large-scale gears with medium precision (GB 5-8). Some researchers have proposed using laser trackers for measurement, but this approach has not been widely adopted. In recent years, some manufacturers have begun using flexible articulated arms to measure local features of slewing ring gears in their workshops to evaluate gear accuracy. However, due to limitations such as the low datum accuracy of large gears and the effects of error amplification, the measurement results are inaccurate and lack repeatability.

[0005] Summary of the Invention

[0006] The purpose of the present invention is to provide a more accurate machining accuracy measurement solution for large-sized gears with a diameter of more than 3000mm and gear-making machines, which can measure the gear tooth shape, tooth direction and tooth pitch errors, and solve the serious shortage of large-sized gear machining accuracy measurement instruments.

[0007] The technical solutions of the present invention are as follows:

[0008] A method for detecting the machining accuracy of large-sized gears comprises the following steps:

[0009] Step 1 includes the establishment of the workpiece coordinate system Sg:

[0010] Step 1.1 Secure the flexible articulated arm to the spindle box of the gear-making machine (for a gear grinder or hobber, use the grinding head or roller head), and secure a standard ball to the workpiece, workpiece fixture, or turntable. Alternatively, secure the flexible articulated arm to the workpiece, workpiece fixture, or turntable, and secure the standard ball to the spindle box of the gear-making machine (for a gear grinder or hobber, use the grinding head or roller head).

[0011] Step 1.2: Rotate the turntable clockwise to three different angles θ1, θ2, and θ3. Use the flexible joint arm to measure the center of the standard sphere and record the coordinates of the three positions (x1, y1, z1), (x2, y2, z2), and (x3, y3, z3). The turntable should rotate as far as possible within the measurement range of the flexible joint arm.

[0012] Step 1.3: Fit the three center coordinates of the standard sphere measured in step 1.2 into a circle and obtain the center coordinate P o ; Fit a plane M with the center coordinates of the standard sphere to obtain the normal vector V of the plane M M；

[0013] Step 1.4 Use the circle center coordinates P o As the starting point, the flexible joint arm base origin as the end point, establish a vector V N ; Vector V N The projection on plane M is vector V X；

[0014] Step 1.5 Use coordinate P o As the origin of the coordinate system, use the vector V M As the Z axis of the coordinate system, use the vector V X As the X axis of the coordinate system, establish the workpiece coordinate system S g .

[0015] Step 2 includes the collection of gear data:

[0016] Step 2.1: In the workpiece coordinate system S g Within the measuring range of the flexible joint arm, operate the flexible joint arm to detect the tooth profile points, tooth direction profile points and tooth pitch position points.

[0017] Step 2.2: Rotate the turntable to other positions and measure the tooth profile points, tooth profile points and pitch position points of other gear teeth until all teeth are measured.

[0018] Step 2.3: If the workpiece temperature deviates from 20°C, perform thermal error compensation on the measurement data.

[0019] Step 2.4: Evaluate the tooth shape, tooth direction and tooth pitch, and combine the tooth pitch data results to form a complete accuracy report.

[0020] Step 2.5: Based on the measurement report, the source of the processing error can be analyzed and corresponding compensation can be made in subsequent processing.

[0021] Furthermore, the flexible articulated arm is connected to a specific position of the machine tool through a tooling.

[0022] Furthermore, in step 1.2, the angles θ1, θ2, and θ3 rotated by the turntable should be within the measurement range of the flexible joint arm.

[0023] Furthermore, when the turntable rotates in step 2.2, it should be ensured that after the rotation is completed, a certain number of gear teeth are still within the measurement range to facilitate subsequent data splicing.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention can make use of large-scale gear processing machine tools and flexible articulated arms, and only requires the development of corresponding software to achieve comprehensive measurement of large-scale gear tooth shape, tooth direction and tooth pitch. For machine tool manufacturers and large-scale gear manufacturers, the investment cost is low and the application value is high.

[0026] The present invention uses the turntable rotation motion to establish the workpiece coordinate system, which does not rely on the gear's own reference. The accuracy of the turntable rotation motion is much higher than the accuracy of the gear's own reference, which improves the accuracy of the workpiece coordinate system and makes the tooth profile measurement result more accurate.

[0027] The present invention can be applied when the gear is still on a machine tool after the gear is processed with allowance, and the processing program can be corrected in time according to the measurement result, and the gear can be reprocessed to achieve closed-loop manufacturing.

[0028] The invention can be applied to the machining accuracy measurement of internal, external, straight and helical teeth and has wide applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a flow chart of the accuracy detection method;

[0030] Figure 2 is a schematic diagram of establishing a coordinate system;

[0031] Figure 3 is a schematic diagram of the measurement method. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0033] Example

[0034] Take the measurement of a spur gear with a module of 20, 250 teeth, and a tooth width of 300 on a precision gear forming grinding machine as an example:

[0035] (a) Fix the flexible joint arm on the grinding head. In order to facilitate fixation and improve safety, install a special fixing bracket on the grinding head.

[0036] (b) Fix the standard ball on the workpiece with the help of a magnetic base.

[0037] (c) Rotate the turntable to rotate the standard ball to three different positions: left, center, and right within the measurement range of the articulated arm, and use the flexible articulated arm to measure the center coordinates of the standard ball: P1 (x1, y1, z1), P2 (x2, y2, z2), and P3 (x3, y3, z3).

[0038] (d) Fit a circle using the center coordinates of the standard sphere to obtain the center coordinates P o (x0,y0,z0),

[0039] in: z0=0

[0040] 1. Fit a plane M with the center coordinates of the standard sphere to obtain the normal vector V of the plane M M : (The Z of the normal vector m Set to 1).

[0041] (e) Using the center coordinates P o As the starting point, the flexible joint arm base origin P1 (x1, y1, z1) as the end point, establish a vector V N ; Vector V N The projection on plane M is vector V X :

[0042] (f) Using coordinates P o (x0,y0,z0) is the origin of the coordinate system, using vector V M As the Z axis of the coordinate system, use the vector V X As the X axis of the coordinate system, establish the workpiece coordinate system S g .

[0043] (g) In the workpiece coordinate system S g Inside, tooth profile points, tooth direction profile points and tooth pitch position points are collected.

[0044] (h) The turntable rotates to other positions and measures the tooth profile points, tooth profile points and pitch position points of other gear teeth until all teeth are measured.

[0045] (i) If the workpiece temperature deviates from 20°C, thermal error compensation is performed on the measurement data.

[0046] (j) Evaluate tooth profile, tooth direction and tooth pitch, and combine the tooth pitch data results to form a complete accuracy report.

[0047] (k) Based on the measurement report, the source of the processing error can be analyzed and corresponding compensation can be made in subsequent processing.

[0048] The invention is not limited to applications in gear milling machines, gear grinding machines, gear hobbing machines, or large-scale gear measuring machines. The above examples are merely descriptions of preferred embodiments of the present invention and are not intended to limit the concept and scope of the invention. Any modifications and improvements to the technical solution of the invention made by ordinary engineers and technicians in this field without departing from the concept of the invention shall fall within the scope of protection of the invention. The technical content of the invention is fully described in the claims.

[0049] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for detecting the machining accuracy of large-sized gears, comprising the following steps: Step 1 includes the establishment of the workpiece coordinate system Sg: Step 1.1: Fix the flexible articulated arm on the spindle box of the gear manufacturing machine tool. If it is a gear grinding machine or a hobbing machine, it is the grinding head or the hobbing head. And fix a standard ball on the workpiece, or on the workpiece fixture or the turntable surface. It is also possible to fix the flexible articulated arm on the workpiece, or on the workpiece fixture or the turntable surface, and fix the standard ball on the spindle box of the gear manufacturing machine tool. If it is a gear grinding machine or a hobbing machine, it is the grinding head or the hobbing head; Step 1.2: Rotate the turntable clockwise to three different angles θ1, θ2, θ3, and use the flexible articulated arm to measure the center position of the standard ball, and record the coordinates (x1, y1, z1), (x2, y2, z2), (x3, y3) at the three positions; within the measurement range of the flexible articulated arm, the rotation range of the turntable should be as large as possible; Step 1.3: Fit a circle based on the three center coordinates of the standard sphere measured in Step 1.2 to obtain the center coordinate P o ; Fit a plane M using the center coordinates of the standard sphere to obtain the normal vector V of plane M M ; Step 1.4: Use the center coordinate P o as the starting point and the origin of the flexible joint arm base as the ending point to establish a vector V N ; The projection of the vector V N on the plane M is the vector V X ; Step 1.5: Use coordinate P o as the origin of the coordinate system, and use vector V M as the Z-axis of the coordinate system, and use vector V X as the X-axis of the coordinate system to establish the workpiece coordinate system S g .

2. A method for detecting the machining accuracy of large-sized gears according to claim 1, characterized in that: Step 2 includes the acquisition of gear data: Step 2.1: Within the workpiece coordinate system S g and within the measurement range of the flexible joint arm, operate the flexible joint arm to detect the tooth profile points, helix profile points and pitch position points. Step 2.2: Rotate the turntable to other positions, and measure the tooth profile points, helix profile points and pitch position points of other teeth of the gear until all teeth are measured; Step 2.3: If the workpiece temperature deviates from 20 °C, perform thermal error compensation on the measurement data; Step 2.4: Evaluate the tooth profile, helix and pitch, and splice the pitch data results to form a complete accuracy report; Step 2.5: Based on the measurement report, the source of the machining error can be analyzed, and corresponding compensation can be carried out in subsequent machining.

Images