Method for compensating machining precision of five-axis machine tool

Abstract

The invention discloses a method for compensating the machining precision of a five-axis machine tool. The method comprises the steps that firstly, two datum planes of a test block are defined; step 2, the cutter moves along a cutter path track generated by the first driving line, and an actual gap between the process ball-end cutter and the reference surface is measured; step 3, moving the cutter along a cutter path track generated by the second driving line, and measuring an actual gap between the maximum ball head part of the side edge of the process ball head cutter and the reference surface; fourthly, according to the actual gap, the compensation value of the cutter length of the cutter in the cutter axis direction and the compensation value of the Z-axis machining original point of the part in the Z-axis direction are calculated; 5, cutter length compensation is conducted in the machine tool cutter parameter table according to the compensation value of the cutter length of the cutter in the cutter axis direction, and the Z-axis machining original point of the part is compensated according to the compensation value of the Z-axis machining original point of the part in the Z-axis direction. The problem that a conventional five-axis machine tool error correction method cannot meet the part machining requirement with the high machining precision requirement is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of numerical control machining of aero-engine, and particularly relates to a method for compensating machining precision of a five-axis machine tool. BACKGROUND

[0002] In theory, the precision of a five-axis machine tool in its stroke range should meet the manufacturing requirements. However, in actual production, most five-axis machine tools are affected by environmental temperature, collision deformation, use wear, and manufacturing precision of the machine tool, resulting in a large error between the actual position and the theoretical position of the five-axis machine tool. Usually, machine repair personnel measures the five-axis machine tool by using a high-precision process ball device, and compensates and corrects the error of the five-axis machine tool by changing the parameters of the machine tool. In actual production, due to the influence of the service life of the machine tool and the manufacturing precision of the machine tool, it is difficult to completely compensate and correct the error of the five-axis machine tool by changing the parameters of the machine tool, and only the precision of each direction of the machine tool can be compensated.

[0003] For some parts with extremely high machining precision requirements, the conventional method for correcting the error of the five-axis machine tool cannot meet the machining requirements. For example, the integral blade ring is a core component of an aero-engine, and the machining precision of the integral blade ring directly affects the overall performance of the aero-engine. With the increasing requirements for the performance of the aero-engine, the design precision of the integral blade ring is continuously improved, and the manufacturing requirements are becoming more and more stringent. The machining precision of the edge head part of the integral blade ring is the most stringent, and the machining tolerance requirement of the front edge part is ±0.03mm, which undoubtedly puts forward higher requirements for the precision and stability of the five-axis machine tool. SUMMARY

[0004] The purpose of the present application is to provide a method for compensating machining precision of a five-axis machine tool, so as to solve the problem that the conventional method for correcting the error of the five-axis machine tool cannot meet the machining requirements of parts with high machining precision requirements.

[0005] The present application adopts the following technical scheme: a method for compensating machining precision of a five-axis machine tool, comprising the following steps: Step one, select an L-shaped trial block blank with the same material as the part to be machined, and place it near the machining position of the machine tool part machining program to be machined, so as to obtain two reference surfaces M1 plane and M2 plane, the reference surface M1 is parallel to the XY plane of the machine tool coordinate system, and the reference surface M2 is parallel to the YZ plane of the machine tool coordinate system; Step two, offset the reference surface M1 and the reference surface M2 by a distance P1 to obtain two offset surfaces, the distance P1 is the radius of the process ball head cutter plus the theoretical gap, then move the intersection line of the two offset surfaces along the 0° direction of the main shaft A by a distance of the radius of the process ball head cutter, to obtain a first driving line; The theoretical gap is the theoretical gap a1 between the process ball head cutter and the reference surface M2, or the theoretical gap a2 between the process ball head cutter and the reference surface M1. The process ball end mill is moved along the tool path generated by the first drive line, and the actual gap c1 between the process ball end mill and the reference surface M1, and the actual gap c2 between the process ball end mill and the reference surface M2 are measured. Determine whether the actual gaps c1 and c2 correspond to and are equal to a2 and a1 respectively. If they are not equal, repeat the processing steps in step one until they are equal, and then proceed to step three. Step 3: Move the intersection line of the two bias surfaces from Step 2 along the direction of the main shaft A swing angle a° by a distance equal to the radius of the process ball end mill, and you will get the second drive line; The process ball end mill is moved along the tool path generated by the second drive line. The actual gap b1 between the maximum ball end portion of the process ball end mill's side edge and the reference surface M2, and the actual gap b2 between the tip of the process ball end mill's bottom edge and the reference surface M1 are obtained with the help of a feeler gauge. Step 4: Based on the actual clearances b1 and b2 obtained in Step 3, calculate the compensation value of the tool length along the tool axis and the compensation value of the workpiece's Z-axis machining origin along the Z-axis during the machine tool machining process. Step 5: Based on the tool length compensation value along the tool axis obtained in Step 4, perform tool length compensation in the machine tool parameter table. Based on the compensation value along the Z-axis direction of the part's Z-axis machining origin obtained in Step 4, compensate the part's Z-axis machining origin. Furthermore, let A(ɑ1, ɑ2) be the theoretical position of the ball end mill in step three, and let B(b1, b2) be the actual test position of the ball end mill in step three. (1) The compensation value L1 for the length of the ball end mill along the cutter axis is: L1 = |ɑ1-b1| / cos a, (2) The compensation value L2 of the part's Z-axis machining origin along the Z-axis direction is: 1) When α1 > b1, α2 < b2 or α1 < b1, α2 > b2, L2 = |b2 - α2| + |α1 - b1| tan a, 2) When a1 > b1 and a2 > b2, L2 = |b2 - a2| - |a1 - b1| tan a, 3) When a1 < b1 and a2 < b2, L2 = |a1-b1|tan a - |b2-a2|.

[0006] Furthermore, the flatness of both datum plane M1 and datum plane M2 is ≤0.005mm.

[0007] Furthermore, the diameter of the ball end mill is φ6-φ12, and the runout of the ball end mill is within 0.005mm.

[0008] Furthermore, the A-axis swing angle α is 25°~45°.

[0009] The beneficial effects of this invention are as follows: This invention proposes a method for compensating for the machining accuracy of a five-axis machine tool. By machining a test block made of the same material as the part to be machined (tested near the programmed machining position), the error to be compensated is measured and calculated. This error is the most realistic comprehensive error of the machine tool machining the part under the current working conditions. Therefore, this method of compensating for machine tool accuracy can maximize the machining accuracy of the part to be machined. The method of this invention is low-cost, highly efficient, simple to operate, and highly versatile. It can achieve batch machining with zero tolerance, which is of great significance for achieving efficient mass production. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the two reference planes of the L-shaped test block; Figure 2 This is a schematic diagram of the test of the machine tool spindle A swing angle at 0°. Figure 3 This is a schematic diagram of the test of the swing angle a° of the machine tool spindle A; Figure 4 A schematic diagram for calculating compensation for machine tool errors; Figure 5 This is a schematic diagram of the machining of the leading edge of the integral blade ring using a five-axis machine tool in the embodiment. Detailed Implementation

[0011] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0012] This invention provides a method for compensating for machining accuracy on a five-axis machine tool, applicable to the machining of integral blade rings or other high-precision parts. The machine tool used in this invention is a five-axis machine tool. The specific method includes the following steps: Step 1: As Figure 1 As shown, an L-shaped test block blank made of the same material as the part to be processed is placed near the processing position in the machine tool part processing program for processing, resulting in two reference planes, M1 plane and M2 plane. Reference plane M1 is parallel to the XY plane of the machine tool coordinate system, and reference plane M2 is parallel to the YZ plane of the machine tool coordinate system. Step 2: After offsetting reference planes M1 and M2 by a distance P1, two offset surfaces are obtained. The distance P1 is the radius of the ball end mill plus the theoretical clearance. Then, the intersection line of the two offset surfaces is moved along the direction of the spindle A swing angle 0° by the radius of the ball end mill, thus obtaining the first drive line; the schematic diagram of the machine tool spindle A swing angle 0° state test is shown below. Figure 2 As shown; The theoretical clearance is either the theoretical clearance α1 between the process ball end mill and the reference surface M2, or the theoretical clearance α2 between the process ball end mill and the reference surface M1; the distance P1 can be calculated by arbitrarily choosing any theoretical clearance, and usually the theoretical clearances α2 and α1 can be set to equal values.

[0013] The process ball end mill is moved along the tool path generated by the first drive line, and the actual gap c1 between the process ball end mill and the reference surface M1 and the actual gap c2 between the process ball end mill and the reference surface M2 are measured with a feeler gauge. Determine whether the actual gaps c1 and c2 correspond to the preset theoretical gaps a2 and a1 respectively. If they are not equal, repeat the processing in step one to adjust the values ​​of c1 and c2 until they are equal before proceeding to step three. Step 3: Move the intersection line of the two offset surfaces from Step 2 along the direction of the spindle A swing angle a° by a distance equal to the radius of the ball end mill, and you will obtain the second drive line; the schematic diagram of the spindle A swing angle a° state test is shown below. Figure 3 As shown; The ball end mill is moved along the tool path generated by the second drive line. The actual gap b1 between the maximum ball end portion of the side edge of the ball end mill and the reference surface M2, and the actual gap b2 between the tip of the bottom edge of the ball end mill and the reference surface M1 are obtained with the help of a feeler gauge. Step 4: Based on the actual clearances b1 and b2 obtained in Step 3, calculate the compensation value of the tool length along the tool axis and the compensation value of the workpiece's Z-axis machining origin along the Z-axis during the machine tool machining process. Step 5: Based on the tool length compensation value along the tool axis obtained in Step 4, perform tool length compensation in the machine tool parameter table. Based on the compensation value along the Z-axis direction of the part's Z-axis machining origin obtained in Step 4, compensate the part's Z-axis machining origin, thereby achieving comprehensive error compensation for the overall CNC machining process of the part to be machined. In some embodiments, let A(ɑ1, ɑ2) be the theoretical position of the ball end mill in step three, and let B(b1, b2) be the actual test position of the ball end mill in step three; (1) The compensation value L1 for the length of the ball end mill along the cutter axis is: L1 = |ɑ1-b1| / cos a, (2) The compensation value L2 of the part's Z-axis machining origin along the Z-axis direction is: 4) When α1 > b1, α2 < b2 or α1 < b1, α2 > b2, L2 = |b2 - α2| + |α1 - b1| tan a, 5) When a1 > b1 and a2 > b2, L2 = |b2 - a2| - |a1 - b1| tan a, 6) When a1 < b1 and a2 < b2, L2 = |a1-b1|tan a - |b2-a2|; In some embodiments, the flatness of both reference surface M1 and reference surface M2 is ≤0.005mm.

[0014] In some embodiments, the diameter of the ball end mill is φ6-φ12, and the runout of the ball end mill is within 0.005mm.

[0015] In some embodiments, when the part to be processed is an integral blade ring, the A-axis swing angle a° is generally 25°~45°. Example

[0016] Reference Figure 5 A schematic diagram of the machining of the leading edge of the integral blade ring on a five-axis machine tool is shown. First, error compensation is performed on the five-axis machine tool, and then this is used to achieve comprehensive error compensation for the CNC machining process of the integral blade ring.

[0017] Step 1: Select an L-shaped test block blank made of the same material as the part to be processed and place it near the processing position in the machine tool part processing program for processing. Two reference surfaces are obtained, namely plane M1 and plane M2. The flatness of reference surface M1 and reference surface M2 must be ≤0.005mm. Reference surface M1 is parallel to the XY plane of the machine tool coordinate system, and reference surface M2 is parallel to the YZ plane of the machine tool coordinate system. Step 2: Using a φ7 ball end mill, the radius of the ball end mill is 3.5mm. Assuming the theoretical clearances α2 and α1 are both 0.15mm, offset the reference surfaces M1 and M2 by 3.65mm to find their intersection line. Then, move this intersection line 3.5mm along the spindle A at a 0° swing angle to obtain the first drive line. The operator uses the φ7 ball end mill to move along the toolpath generated by the first drive line, using a feeler gauge to measure the actual clearance c1 between the ball end mill and reference surface M1, and the actual clearance c2 between the ball end mill and reference surface M2. Start by inserting the smallest gauge until it can be inserted without any noticeable looseness. Repeat the measurement three times and take the average value as the actual gap. This verifies whether the actual gap between the ball end mill and the reference surface M1, and the actual gap between the ball end mill and the reference surface M2, are consistent with the theoretical gap of 0.15mm. If they are inconsistent, the processing step one needs to be repeated to ensure that the actual gap is consistent with the theoretical gap. After they are consistent, proceed to the next step. Step 3: Then, the intersection line of the two offset surfaces from Step 2 is moved 3.5mm along the 35° swing angle direction of the main shaft A to obtain the second drive line. The operator uses a φ7 process ball end mill to move along the toolpath generated by the second drive line, and uses a feeler gauge to obtain the actual gap b1 between the maximum ball end portion of the process ball end mill's side edge and the reference surface M2 as 0.12mm, and the actual gap b2 between the tip of the process ball end mill's bottom edge and the reference surface M1 as 0.18mm; Step Four: As Figure 4 As shown, calculate the compensation value of the tool length along the tool axis and the compensation value of the workpiece's Z-axis machining origin along the Z-axis. (1) The compensation value of the tool length along the tool axis is L1 = |ɑ1-b1| / cos a = 0.036623mm ≈ 0.036mm; (2) Compensation value L2 of the part's Z-axis machining origin along the Z-axis direction L2=︱b2-ɑ2︱+︱ɑ1-b1︱tan a=0.051006mm≈0.051mm; Where a = 35°.

[0018] Step 5: Based on the tool length compensation value along the tool axis obtained in Step 4, perform tool length compensation in the machine tool parameter table, i.e., tool length is raised by 0.036mm. Based on the compensation value along the Z-axis of the part's Z-axis machining origin obtained in Step 4, compensate the part's Z-axis machining origin in the machine tool's overall impeller origin setting, i.e., the part's Z-axis machining origin is lowered by 0.051mm. This achieves comprehensive error compensation for the overall impeller CNC program machining process.

[0019] In this embodiment, for five-axis machine tools with poor precision or long service life, if conventional methods for correcting five-axis machine tool errors are used, the overall error of the five-axis machine tool will result in obvious tool joints between the edge, blade back, and blade base during the integral blade ring milling process. The measurement data from the finish milling process will approach or even exceed the tolerance. The edge is the part with the most stringent tolerance requirements, and the subsequent polishing process, in order to remove the tool joint marks from the milling, will inevitably lead to the final blade ring data exceeding the tolerance. Therefore, the compensation method of this invention can better meet the precision requirements of integral blade ring machining.

Claims

1. A method for compensating machining accuracy of a five-axis machine tool, characterized in that, It comprises the following steps: Step one, select the L-shaped test block blank of the same material as the part to be processed, and place it in the five-axis machine tool to obtain two reference surfaces M1 and M2, wherein the reference surface M1 is parallel to the XY plane of the machine tool coordinate system, and the reference surface M2 is parallel to the YZ plane of the machine tool coordinate system; Step two, offset the reference surface M1 and the reference surface M2 by a distance P1 to obtain two offset surfaces, wherein the distance P1 is the radius of the process ball nose cutter plus the theoretical gap, and then move the intersection line of the two offset surfaces along the 0° direction of the main shaft A by a distance equal to the radius of the process ball nose cutter to obtain a first driving line; The theoretical gap is the theoretical gap ɑ1 between the process ball nose cutter and the reference surface M2, or the theoretical gap ɑ2 between the process ball nose cutter and the reference surface M1; Use the process ball nose cutter to move along the tool path generated by the first driving line, measure the actual gap c1 between the process ball nose cutter and the reference surface M1, and the actual gap c2 between the process ball nose cutter and the reference surface M2; Determine whether the actual gaps c1 and c2 are equal to ɑ2 and ɑ1 respectively, if not, repeat the processing process of step one until they are equal, and then proceed to step three; Step three, move the intersection line of the two offset surfaces in step two along the a° direction of the main shaft A by a distance equal to the radius of the process ball nose cutter to obtain a second driving line; Use the process ball nose cutter to move along the tool path generated by the second driving line, and use the feeler gauge to obtain the actual gap b1 between the maximum ball head part of the side edge of the process ball nose cutter and the reference surface M2, and the actual gap b2 between the tip part of the bottom edge of the process ball nose cutter and the reference surface M1; Step four, according to the actual gaps b1 and b2 obtained in step three, calculate the compensation value of the tool length along the tool axis direction during machine tool processing and the compensation value of the part Z-axis machining origin along the Z-axis direction; Step five, according to the compensation value of the tool length along the tool axis direction obtained in step four, perform tool length compensation in the tool parameter table of the machine tool, and according to the compensation value of the part Z-axis machining origin along the Z-axis direction obtained in step four, compensate the part Z-axis machining origin.

2. The method of claim 1, wherein the compensation of the machining accuracy of the five-axis machine tool is performed by a computer program. A(ɑ1, ɑ2) is the theoretical position of the process ball nose cutter in step three, and B(b1, b2) is the actual test position of the process ball nose cutter in step three; (1) The compensation value L1 of the tool length along the tool axis direction is: L1=︱ɑ1-b1︱ / cos a, (2) The compensation value L2 of the part Z-axis machining origin along the Z-axis direction is: 1) When ɑ1>b1, ɑ2<b2 or ɑ1<b1, ɑ2>b2, L2=︱b2-ɑ2︱+︱ɑ1-b1︱tan a, 2) When ɑ1>b1, ɑ2>b2, L2=︱b2-ɑ2︱-︱ɑ1-b1︱tan a, 3) When ɑ1<b1, ɑ2<b2, L2=︱ɑ1-b1︱tan a -︱b2-ɑ2︱.

3. The method of claim 1 or 2, wherein, The flatness of the reference surface M1 and the reference surface M2 is ≤0.005mm.

4. The method of claim 3, wherein, The process ball head cutter diameter is φ6-φ12, and the process ball head cutter runout is within 0.005mm.

5. The method of claim 3, wherein, The A-axis swing angle a° is 25°-45°.

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