Method for improving on-machine measurement precision in self-adaptive milling of linear welding blade disc

Abstract

The invention relates to a method for improving on-machine measurement precision in self-adaptive milling of a linear welding blade disc, belongs to the technical field of precision manufacturing of aero-engines, and aims to solve the problems that existing probe calibration needs cold machine operation, time consumption is long, and precision is affected by thermal deformation of a machine tool. According to the method, a standard ball is fixedly installed on an A-axis base of equipment to establish a constant space reference, firstly, initial calibration of a cold machine is conducted, then the actual position of the center of the standard ball is measured in the thermal stability state of the equipment, and the obtained deviation value is dynamically compensated to internal parameters of a measuring head, so that online precision correction in the heat engine state is achieved. According to the method, the workpiece does not need to be disassembled, the calibration time is shortened from more than 12 hours to less than 30 minutes, the thermal deformation error is effectively controlled, the measurement deviation is controlled within 0.005 mm, and the cutter connecting precision and the machining quality of the linear welding blade disc are remarkably improved.

Description

TECHNICAL FIELD

[0003] The present application relates to the field of mechanical manufacturing, in particular to a method for improving the measurement accuracy of precision parts. BACKGROUND

[0005] As the core load-bearing component of the fan system of an aero-engine, the linear welded blade disc has a special machining requirement that the "2 / 3 area is the final surface (cannot be machined twice), and the 1 / 3 unprocessed area needs to be milled into shape". The unprocessed area needs to be machined with high precision with the formed surface through self-adaptive milling. If the tool joint error exceeds ±0.03mm, it will directly lead to the decline of the aerodynamic performance of the blade disc, the shortening of the fatigue life, and even the occurrence of operation safety hazards.

[0006] In the existing machining technology, the measuring head is the core component of the in-machine measurement, and there are two key problems: first, the traditional calibration needs to be carried out under the cold state (the equipment is stopped for more than 8 hours, and the temperature is stabilized to room temperature), and the blade workpiece needs to be disassembled. The length and radius calibration takes more than 4 hours, and the cumulative downtime is more than 12 hours, which seriously reduces the production efficiency; second, the machine tool zero reference has a deviation introduced by the thermal deformation of the machine tool (the Y / Z direction deviation is ±0.008-0.052mm), which cannot meet the precision requirements of self-adaptive machining. SUMMARY

[0008] To solve the above problems, the present application discloses a method for improving the in-machine measurement accuracy in the self-adaptive milling of a linear welded blade disc.

[0009] The specific technical solution is as follows:

[0010] A method for improving the in-machine measurement accuracy in the self-adaptive milling of a linear welded blade disc, comprising the following steps:

[0011] Step S1: equipment modification and reference establishment

[0012] On the rotating shaft A shaft base of the machining equipment, a standard ball with a roundness error of less than 0.001mm is rigidly installed through an installation base with a heat insulation element, so that a fixed space reference is formed between the ball center of the standard ball and the machine tool zero point;

[0013] Step S2: initial calibration of the measuring head under the cold state

[0014] Under the cold state of the machine tool, the following sub-steps are performed:

[0015] S2.1: make the positioning end surface of the machine tool spindle contact the top end of the standard ball, and record the Z axis mechanical coordinate value MZ1 under the machine tool coordinate system at this time;

[0016] S2.2: install the probe on the spindle, run the probe calibration program, input parameters MZ1 and standard ball diameter D1, obtain the initial trigger radius R1 and trigger length L1 of the probe;

[0017] Step S3: equipment warm-up and state stabilization

[0018] Remove the probe on the equipment spindle, install a standard tool with a theoretical size, perform a step-by-step warm-up process to make the machine tool spindle and each X, Y, Z linear axis temperature uniformly rise and reach a thermal stable state, the warm-up process at least includes segmented operation at different spindle speeds and coordinated reciprocating motion of each axis; the equipment standard measurement program measures the diameter and length of the standard tool, the measurement parameters select continuous measurement for 3 times to ensure the accuracy of the standard tool measurement, and the measured length of the standard tool is checked, if the standard tool length is within L2±0.005mm, the warm-up is ended, if it exceeds L2±0.005mm, return to step 3 and repeat the execution;

[0019] Step S4: reference re-measurement and deviation acquisition under the warm-up state

[0020] After the warm-up is stabilized, the probe calibrated in step S2 is used to automatically measure the center position of the standard ball in the machine tool coordinate system, and the actual coordinate value (X0, Y0, Z0) of the ball center position is set as the zero point of the standard ball coordinate system G509;

[0021] Step S5: dynamic compensation of probe parameters

[0022] Based on the actual coordinate value (X1, Y1, Z1) obtained in step S4, the following sub-steps are executed:

[0023] S5.1: measure the center position of the standard ball in the G509 coordinate system using the adaptive machining software for the blade disc, respectively X1, Y1, Z1;

[0024] S5.2: determine whether the absolute values of X1, Y1, Z1 are all less than the first threshold value 0.01mm; if any axis deviation exceeds the first threshold value, return to step S3 to re-warm up;

[0025] S5.3: obtain the internal compensation parameters ΔL3, ΔL2, ΔL1 by subtracting (X1, Y1, Z1) from (X0, Y0, Z0) respectively;

[0026] S5.4: repeat step S4 to measure the center position of the standard ball again, if the absolute values of X1, Y1, Z1 measured at this time and X0, Y0, Z0 are all less than or equal to the second threshold value 0.005mm, the compensation is completed; otherwise, repeat this step S5;

[0027] Step S6: Fine measurement and adaptive machining

[0028] The linear welding vane disc part clamped on the workbench is measured in-situ using the probe compensated in step S5, and an adaptive milling machining path is generated according to the measurement result, and the final milling machining of the vane disc is completed.

[0029] In the step S1, the mounting base (2) is connected with the A-axis base (1) through the combination structure of the positioning pin and the screw.

[0030] The stepped thermal machine process in the step S3 is specifically that the spindle is operated at the rotation speeds of 3000 rpm, 8000 rpm and 12000 rpm in sequence, each rotation speed gear is operated for at least 3 minutes, and the reciprocating motion is performed on the X, Y and Z axes at the same time.

[0031] After the rotation speed of the spindle reaches 12000 rpm, the rotation speed is reduced to 3000 rpm and continues to operate for not less than 30 minutes, and the reciprocating motion is performed on the straight axes during the period.

[0032] The standard ball (3) is of ceramic material.

[0033] The advantages of the present application are that: through the innovative integration of the fixed standard ball on the machine tool A-axis base and the combination of the dynamic calibration compensation algorithm, the fast and high-precision online calibration of the probe in the thermal machine state is realized, the problems of low efficiency and unstable precision caused by the traditional method of cold machine shutdown and disassembly of the workpiece are completely solved, the single calibration time is shortened from more than 4 hours to 30 minutes, and the measurement precision is stably controlled within ±0.005 mm, the equipment utilization rate and production efficiency are greatly improved while ensuring the high-precision tool engagement quality of the linear welding vane disc. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a schematic view of the installation position of the standard ball.

[0036] Figure 2 It is a relationship diagram of the tool setting gauge and the Y and Z axes about perpendicularity in the case of using the standard tool. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0039] A method for improving on-machine measurement accuracy in adaptive milling of linear welded impeller disks includes the following steps:

[0040] Step S1: Equipment Modification and Benchmark Establishment

[0041] On the base of the rotating A-axis of the processing equipment, a standard ball 3 with a roundness error of less than 0.001mm is rigidly installed on the mounting base 2 with heat insulation element 4, so that the center of the standard ball and the zero point of the machine tool form a fixed spatial reference.

[0042] Step S2: Initial calibration of the probe in cold state

[0043] When the machine tool is cold, perform the following sub-steps:

[0044] S2.1: Make the positioning end face of the machine tool spindle contact the top of the standard ball, and record the Z-axis mechanical coordinate value MZ1 in the machine tool coordinate system at this time;

[0045] S2.2: Install the probe on the spindle, run the probe calibration program, input the parameter MZ1 and the standard ball diameter D1, and obtain the initial trigger radius R1 and trigger length L1 of the probe;

[0046] Step S3: Equipment Heat Up and Stabilization

[0047] Remove the probe from the machine spindle, install a standard cutting tool with theoretical dimensions, and execute a stepped heat-generating process to ensure a uniform temperature rise of the machine spindle and all X, Y, and Z linear axes until (e.g.) Figure 1 6-Equipment Z-axis, 7-Equipment Y-axis, X-axis is perpendicular to the plane formed by the YZ axes) Thermal stability state, the heat engine process includes at least segmented operation at different spindle speeds and coordinated reciprocating motion of each axis; Equipment standard measurement procedure, measuring the diameter and length of standard tools, the measurement parameters are selected to be measured continuously for 3 times to ensure the accuracy of standard tool measurement, such as Figure 2 As shown, 12 - a standard tool with theoretical dimensions, 13 - a tool setter, 14 - the Z-axis value when the tool setter is triggered when the Y / Z axis perpendicularity is out of tolerance, 15 - the Z-axis value when the tool setter is triggered when the Y / Z axis perpendicularity is normal, 16 - the Y-axis of the device when the Y / Z axis perpendicularity is normal, 17 - the Y-axis of the device when the Y / Z axis perpendicularity is out of tolerance. Check the measured length of the standard tool 12; if the length of the standard tool is within L2±0.005mm, the warm-up ends; if it exceeds L2±0.005mm, return to step 3 and repeat the execution.

[0048] Step S4: Benchmark retest and deviation acquisition under hot-engine conditions

[0049] After the thermal machine is stabilized, the center position of the standard ball is automatically measured in the machine coordinate system using the probe calibrated in step S2, and the actual coordinate values (X0, Y0, Z0) of the center position of the ball are set as the zero point of the standard ball coordinate system (G509);

[0050] Step S5: dynamic compensation of probe parameters

[0051] Based on the actual coordinate values (X1, Y1, Z1) obtained in step S4, the following sub-steps are performed:

[0052] S5.1: measure the center position of the standard ball in the G509 coordinate system using the adaptive machining software for the blade disc, respectively X1, Y1, Z1;

[0053] S5.2: determine whether the absolute values of X1, Y1, Z1 are all less than the first threshold value 0.01 mm; if the deviation in any axis exceeds the first threshold value, return to step S3 to re-heat the machine;

[0054] S5.3: obtain the internal compensation parameters ΔL3, ΔL2, ΔL1 by subtracting (X0, Y0, Z0) from (X1, Y1, Z1) obtained in S5.2;

[0055] S5.4: repeat step S4 to measure the center position of the standard ball again, if the absolute values of X1, Y1, Z1 measured at this time are all less than or equal to the second threshold value 0.005 mm, the compensation is completed; otherwise, repeat this step S5;

[0056] Step S6: precision measurement and adaptive machining

[0057] Using the probe compensated in step S5, the linearly welded blade disc part clamped on the workbench is measured in the machine, and adaptive milling machining paths are generated according to the measurement results, and the final milling machining of the blade disc is completed.

[0058] In step S1, the mounting base 2 is connected to the A-axis base 1 through the combination structure of the positioning pin and the screw.

[0059] The step S3 is a step-by-step thermal machine process, specifically: the spindle runs at 3000 rpm, 8000 rpm, and 12000 rpm in turn, and each speed gear runs for at least 3 minutes, while the X, Y, Z axes reciprocate;

[0060] After the spindle speed reaches 12000 rpm, the speed is reduced to 3000 rpm and continues to run for not less than 30 minutes, during which the linear axes reciprocate.

[0061] The standard ball 3 is made of ceramic material.

[0062] The working principle of the present application is:

[0063] By installing a high-precision ceramic standard ball on the rotating shaft A base of the machine tool using positioning pins and screws, the ball center of the standard ball installed on the A base forms a fixed and known spatial reference with the machine tool zero point in an ideal state. In the cold state of the machine tool, the probe is used to perform initial calibration on the reference ball to obtain the reference parameters of the probe in the cold state. Subsequently, a controlled "step" thermal machine program is executed to actively and uniformly induce the machine tool to generate typical thermal deformation that occurs in actual machining through spindle speed-up and reciprocating motion of each axis.

[0064] Then the probe is removed, a standard tool with precise theoretical dimensions (diameter D2, length L2) is installed, and the step thermal machine program is executed. The purpose of this stage is not only to heat the machine tool, but also to confirm the perpendicularity between the Y and Z axes when the machine tool enters the thermal steady state. At this time, due to the thermal deformation of the machine tool structure, especially the Y and Z axes, the size of the standard tool is measured to indirectly obtain the perpendicularity between the Y and Z axes. After confirming the thermal stability, the probe is reinstalled, and the ball center position of the same fixed standard ball is measured again. The coordinate values (X0, Y0, Z0) measured at this time are the actual coordinate values (X0, Y0, Z0) of the ball center position, which are set as the zero point of the standard ball coordinate system (G509). Then, the disk adaptive machining software measures the standard ball center position (X1, Y1, Z1) in the G509 coordinate system and obtains the probe compensation value by subtracting (X0, Y0, Z0). In continuous cycles, the difference value is ensured to be within the qualified range to complete the work. Finally, after compensation, the probe is used to measure the disk part, and the size data reflecting the actual position of the part can be obtained, thereby guiding the adaptive machining program to perform high-precision tool engagement milling.

Claims

1. A method for improving in-process measurement accuracy in linear weld blisk adaptive milling, characterized by, Comprising the following steps: Step S1: Equipment modification and reference establishment On the rotating shaft A axis base of the machining equipment, a standard ball with a roundness error less than 0.001 mm is rigidly installed through an installation base with a heat insulation element, so that a fixed space reference is formed between the ball center of the standard ball and the machine tool zero point; Step S2: Initial calibration of the measuring head in the cold state of the machine tool In the cold state of the machine tool, the following sub-steps are performed: S2.1: The positioning end face of the machine tool spindle is brought into contact with the top end of the standard ball, and the Z-axis mechanical coordinate value MZ1 in the machine tool coordinate system at this time is recorded; S2.2: The measuring head is installed on the spindle, the measuring head calibration program is run, and the parameters MZ1 and the standard ball diameter D1 are input, so as to obtain the initial triggering radius R1 and the triggering length L1 of the measuring head; Step S3: Equipment warm-up and stable state The measuring head on the equipment spindle is removed, a standard tool with a theoretical size is installed, and a stepped warm-up process is performed to uniformly raise the temperature of the machine tool spindle and each X, Y, Z linear shaft and reach a thermal stable state, the warm-up process at least includes segmented operation at different spindle speeds and coordinated reciprocating motion of each shaft; the equipment standard measurement program measures the diameter and length of the standard tool, the measurement parameters are selected to be continuously measured for 3 times to ensure the accuracy of the standard tool measurement, and the measured length of the standard tool is checked, if the standard tool length is within L2±0.005 mm, the warm-up is ended, and if it exceeds L2±0.005 mm, step 3 is repeated; Step S4: Reference re-measurement and deviation acquisition in the warm-up state After the warm-up is stable, the measuring head calibrated in step S2 is used to automatically measure the ball center position of the standard ball in the machine tool coordinate system, and the actual coordinate value (X0, Y0, Z0) of the ball center position is set as the zero point of the standard ball coordinate system (G509); Step S5: Dynamic compensation of the measuring head parameters Based on the actual coordinate value (X1, Y1, Z1) obtained in step S4, dynamic compensation is performed, and the following sub-steps are performed: S5.1: The standard ball center position is measured in the G509 coordinate system using the adaptive machining software for the blade disc, and the measured values are X1, Y1, and Z1 respectively; S5.2: It is judged whether the absolute values of X1, Y1, and Z1 are all less than the first threshold value 0.01 mm; if any axial deviation exceeds the first threshold value, step S3 is returned to re-warm-up; S5.3: The difference between (X1, Y1, Z1) obtained in S5.2 and (X0, Y0, Z0) is obtained to obtain internal compensation parameters ΔL3, ΔL2, and ΔL1; S5.4: Step S4 is repeated to measure the standard ball center position again, if the absolute values of X1, Y1, and Z1 measured at this time and X0, Y0, and Z0 are all less than or equal to the second threshold value 0.005 mm, the compensation is completed; otherwise, this step S5 is repeatedly performed; Step S6: Precision measurement and adaptive machining The measuring head compensated in step S5 is used to measure the linearly welded blade disc part clamped on the worktable in the machine, and adaptive milling machining paths are generated according to the measurement results to complete the final milling machining of the blade disc.

2. The method of claim 1, wherein, In the step S1, the mounting base is connected with the A-axis base through a combination of a positioning pin and a screw.

3. The method of claim 1, wherein, The step S3 is a step of gradually increasing the speed of the spindle, and the step S3 comprises the following steps: the spindle is operated at a speed of 3000 rpm, 8000 rpm and 12000 rpm in sequence, and each speed is kept for at least 3 minutes, and the X-axis, the Y-axis and the Z-axis are reciprocated simultaneously. After the speed of the spindle reaches 12000 rpm, the speed of the spindle is decreased to 3000 rpm and the spindle is continuously operated for not less than 30 minutes, and the X-axis, the Y-axis and the Z-axis are reciprocated during the operation.

4. The method of claim 1, wherein, The standard ball is made of ceramic.

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