A machining method for ensuring shape and position tolerances of key assembly holes of long-axis parts

Abstract

The application relates to the field of machining of long-shaft parts in certain helicopters, in particular to a machining method for guaranteeing shape and position tolerances of key assembly holes of long-shaft parts. According to the machining method, after the part is clamped, the outer cylinder inclination error is measured on the machine tool, the measuring points should be close to the two ends of the outer cylinder, according to the measured value, the coordinate system is compensated after formula calculation, then the hole is bored to the final size, and the symmetry requirement is guaranteed. The symmetry requirement of the two groups of key assembly holes and the outer circle reference of the part can be effectively controlled, and the qualified rate of the part is improved. Meanwhile, the method can also be used for compensation machining calculation of related shape and position tolerances of shaft parts with similar structures.

Description

Technical Field

[0001] This invention relates to the field of machining long shaft parts in a certain type of helicopter, specifically a machining method for ensuring the form and position tolerances of key assembly holes in long shaft parts. Background Technology

[0002] Long shaft components mainly refer to the connecting parts of key moving components in the helicopter main rotor hub. These parts are made of titanium alloy and are critical load-bearing moving components of the main rotor hub for this type of helicopter. They are primarily used to connect the rotor blades and the central hub component. Helicopters must withstand high-cycle fatigue loads during flight, and the quality of their machining directly affects flight safety. Furthermore, a set of key mounting holes on this part has strict symmetry requirements. Due to the part's length and the significant distance between the key mounting holes and the reference datum, measurement extension errors during machining are substantial, making it difficult to ensure that this symmetry meets design requirements.

[0003] The difficulty in machining critical assembly holes for this type of part lies in the symmetry requirements between the critical assembly holes and the outer circle of the part. Figure 1a , Figure 1b As shown. The key assembly hole of the part is machined by boring at one end, and the clamping is as follows. Figure 2 As shown, to ensure this symmetry, the perpendicularity between the outer diameter datum and the machine tool table needs to be within 0.02mm when the part is clamped, and the outer diameter should have virtually no deformation after clamping. However, for this type of long shaft structure part, its length is relatively long and the straightened outer diameter datum is relatively short. It is impossible to ensure that the part is completely perpendicular to the machine tool table when clamping, and errors are inevitable. Therefore, it is difficult to guarantee the symmetry between the key assembly holes and the outer diameter of the part after machining. Summary of the Invention

[0004] To ensure the symmetry requirement between the key assembly holes and the outer circle of the part, a practical, effective, and efficient machining method is proposed to guarantee the high-precision form and position tolerances of the part.

[0005] Unlike conventional methods for machining critical assembly holes, which directly finish the workpiece after clamping, the machining method described in this invention first completes the clamping of the workpiece, then measures the tilt error of the outer cylinder on the machine tool. The measurement point should be close to both ends of the outer cylinder. Based on the measured value, the coordinate system is compensated after calculation using a formula, and then the hole is bored to the final size to ensure the symmetry requirements.

[0006] Technical solution

[0007] A machining method for ensuring the form and position tolerances of key assembly holes in long shaft parts includes the following steps: part clamping and alignment—on-machine measurement—calculation of compensation values ​​and compensation of coordinate system—boring to size;

[0008] 1. Part clamping and alignment

[0009] As required, install the parts onto the tooling and complete the alignment in the X, Y, and Z directions. Establish a machining coordinate system on the machine tool. The Y-axis is the direction of the cylindrical axis, and point Y0 is at one end of the cylindrical part. The X-axis is perpendicular to the axis of the two sets of assembly holes, and the Z-axis is parallel to the axis of the two sets of assembly holes. Points X0 and Z0 are set on the axis of the part.

[0010] 2. In-machine measurement

[0011] Manually measure using a lever indicator, taking the machining coordinate system of step 1 as the reference, measure the difference Δ between the values ​​of the two ends of the cylinder in the X direction of the outer circle of the part, which is the highest in the X direction of the machining coordinate system and in the Y direction, and the values ​​of points 3 and 4 in the X direction, in mm;

[0012] 3. Calculate the compensation value and compensate the coordinate system.

[0013] Based on the measurement data, calculate the compensation value using the formula χ=Δ×(a / b), and then apply the calculated compensation value to the machine tool machining coordinate system. All units are in mm. When the compensation value is positive, compensate in the positive X direction; when the compensation value is negative, compensate in the negative X direction.

[0014] Where χ: machining coordinate system compensation value, Δ: clamping tilt error value of the outer cylinder of the part, a: length dimension of the outer cylinder of the part, b: distance dimension from the origin of the machining coordinate system to the axis of the key assembly hole of the part, wherein the origin of the machining coordinate system is at one end of the outer cylinder of the part.

[0015] 4 Boring holes to size

[0016] The key assembly holes are precision bored to the final dimensional requirements.

[0017] Further verification of the compensation direction is required. After coordinate system compensation is completed, the machining program is run to rough bore the two sets of key assembly holes to a smooth finish. After boring, a allowance of 0.3mm to 0.4mm is left on each side. The symmetry between the two sets of holes and the outer cylinder of the part is measured using a machine tool probe to check whether it is close to the theoretical value that should be achieved after calculating the compensation value and completing the compensation machining. This is used to check whether the coordinate system compensation direction is correct. If the difference is large, it can be determined that the compensation direction is reversed, and the above steps need to be repeated for verification.

[0018] Furthermore, in step 2, the on-machine measurement can be performed automatically using a machine tool probe.

[0019] Furthermore, the measurement error of the probe of the machine tool should be ≤0.015mm.

[0020] Furthermore, the specific operation of the coordinate system compensation is as follows: open the relevant interface for setting the machine tool coordinate system, input the calculated compensation value into the X coordinate system precision field, and complete the machine tool coordinate system compensation.

[0021] Furthermore, the boring tool feed direction should be as perpendicular as possible to the XY plane of the machining coordinate system.

[0022] Furthermore, during boring, it is necessary to ensure that holes on the same axis are completed in one machining operation to improve the coaxiality of holes on the same axis.

[0023] Furthermore, when clamping the part, the inclination of the outer cylinder in the X direction of the coordinate system should be less than 0.05mm.

[0024] Furthermore, when clamping the part, the inclination of the outer cylinder in the Z direction of the coordinate system should be less than 0.03mm.

[0025] Technical effect

[0026] Unlike conventional machining methods that directly finish-machine two sets of critical assembly holes, which can lead to symmetry issues between the holes and the outer diameter datum of the part, the machining method described in this invention effectively controls the symmetry requirements between the two sets of critical assembly holes and the outer diameter datum of the part, improving the part's pass rate. Furthermore, this method can also be used for compensating for form and position tolerances in other shaft-type parts with similar structures. Attached Figure Description

[0027] Figure 1a Schematic diagram of long shaft-type parts;

[0028] Figure 1b Side view of the structure of a long shaft-type part;

[0029] Figure 2 Schematic diagram of clamping the fork lug area. Detailed Implementation

[0030] The present invention will be further described below with reference to embodiments. The following description represents only a portion of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0031] Implementation Case 1

[0032] Implementation steps:

[0033] 1. Part clamping and alignment. Mount the part onto the fixture as required, and complete the alignment in the X, Y, and Z directions. Establish the machining coordinate system on the machine tool.

[0034] 2. In-machine measurement. Use the machine tool probe to measure the X values ​​at the two ends of the outer cylinder of the part, points 3 and 4, at their highest points in the X direction. The measured value of point 3 is 73.06 mm, and the measured value of point 4 is 73.03 mm. The tilt error of the outer cylinder is the measured value of point 3 minus the measured value of point 4, i.e., Δ is 0.03 mm.

[0035] 3. Calculate the compensation value and compensate the coordinate system. Given that the length b of the outer cylinder of the part is 146mm, and the distance a from the position of the coordinate system established on the end face of the outer cylinder to the axis of the key assembly hole of the part is 366mm, substituting into the formula χ=Δ×(a / b), we can calculate χ=0.03×(366 / 146)=0.075mm, that is, the X-coordinate compensation value is 0.075mm. Input the compensation value into the X-coordinate precision column of the machine tool to complete the compensation.

[0036] 4. Boring to Dimensions. First, bore the holes to a smooth surface. Measure the symmetry of the outer circle at one end of the coordinate system established between the two sets of key assembly holes and the part. The symmetry should be 2χ, i.e., 2 × 0.075 mm = 0.15 mm. The measured value is 0.14 mm, with an error of 0.01 mm from the theoretical value. This can be determined as a measurement error, indicating that the compensation direction is correct. Call the machining program to bore the two sets of key assembly holes to the final dimensions.

[0037] Implementation Conclusion:

[0038] After the part was machined, it was measured by a coordinate measuring machine. The measured value of the symmetry 0.1C was 0.025mm, which fully meets the design requirement of 0.1 tolerance. This shows that the machining method described in this invention can effectively control the symmetry requirements of the two sets of key assembly holes on this part and the outer circle datum of the part.

[0039] Example 2

[0040] The machining method for ensuring the form and position tolerances of critical assembly holes in long shaft-type parts includes the following steps: part clamping and alignment—on-machine measurement—calculation of compensation values ​​and compensation of the coordinate system—boring to dimension.

[0041] 1. Part clamping and alignment

[0042] Mount the parts onto the fixture as required, and align them in the X, Y, and Z directions. Establish a machining coordinate system on the machine tool; the Y-axis is the cylindrical axis, with point Y0 at one end of the part's cylinder; the X-axis is perpendicular to the axes of the two sets of assembly holes; the Z-axis is parallel to the axes of the two sets of assembly holes; points X0 and Z0 are located on the part's axis. 2. On-machine measurement.

[0043] Manually measure using a lever indicator, taking the machining coordinate system of step 1 as the reference, measure the difference Δ between the values ​​of the two ends of the cylinder in the X direction of the outer circle of the part, which is the highest in the X direction of the machining coordinate system and in the Y direction, and the values ​​of points 3 and 4 in the X direction, in mm;

[0044] 3. Calculate the compensation value and compensate the coordinate system.

[0045] Based on the measurement data, calculate the compensation value using the formula χ=Δ×(a / b), and then apply the calculated compensation value to the machine tool machining coordinate system. All units are in mm. When the compensation value is positive, compensate in the positive X direction; when the compensation value is negative, compensate in the negative X direction.

[0046] Where χ: machining coordinate system compensation value, Δ: clamping tilt error value of the outer cylinder of the part, a: length dimension of the outer cylinder of the part, b: distance dimension from the origin of the machining coordinate system to the axis of the key assembly hole of the part, wherein the origin of the machining coordinate system is at one end of the outer cylinder of the part.

[0047] 4 Boring holes to size

[0048] The key assembly holes are precision bored to the final dimensional requirements.

[0049] Further verification of the compensation direction is required. After coordinate system compensation is completed, the machining program is run to rough bore the two sets of key assembly holes to a smooth finish. After boring, a allowance of 0.3mm to 0.4mm is left on each side. The symmetry between the two sets of holes and the outer cylinder of the part is measured using a machine tool probe to check whether it is close to the theoretical value that should be achieved after calculating the compensation value and completing the compensation machining. This is mainly used to check whether the coordinate system compensation direction is correct. If the difference is large, it can be determined that the compensation direction is reversed, and the above steps need to be repeated for verification.

[0050] Furthermore, in step 2, the on-machine measurement can be performed automatically using a machine tool probe, reducing human error in dial indicator operation and improving the accuracy of the compensated machining.

[0051] Furthermore, the measurement error of the machine tool's probe should be ≤0.015mm. Improving measurement accuracy helps to improve the accuracy of compensated machining.

[0052] Furthermore, the specific operation of the coordinate system compensation is as follows: open the relevant interface for setting the machine tool coordinate system, input the calculated compensation value into the X coordinate system precision field, and complete the machine tool coordinate system compensation.

[0053] Furthermore, the boring tool feed direction should be as perpendicular as possible to the XY plane of the machining coordinate system, which helps to improve the accuracy of compensated machining.

[0054] Furthermore, during boring, it is necessary to ensure that holes on the same axis are completed in one machining operation. Improving the coaxiality of holes on the same axis helps to improve the accuracy of compensation machining.

[0055] Furthermore, when clamping the part, the inclination of the outer cylinder in the X direction of the coordinate system should be less than 0.05mm, which helps to improve the accuracy of the compensation value calculation.

[0056] Furthermore, when clamping the part, the inclination of the outer cylinder in the Z direction of the coordinate system should be less than 0.03mm, which helps to improve the accuracy of compensation machining.

[0057] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein. The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit 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. A machining method for ensuring the form and position tolerances of key assembly holes in long shaft-type parts, characterized in that, Includes the following steps: Step 1: Part clamping and alignment: As required, install the parts onto the tooling and complete the alignment in the X, Y, and Z directions. Establish a machining coordinate system on the machine tool. The Y-axis is the direction of the cylindrical axis, and point Y0 is at one end of the cylindrical part. The X-axis is perpendicular to the axis of the two sets of assembly holes, and the Z-axis is parallel to the axis of the two sets of assembly holes. Points X0 and Z0 are set on the axis of the part. Step 2: On-machine measurement: Manually measure using a lever indicator, taking the machining coordinate system of step 1 as the reference, measure the difference Δ between the values ​​of the two ends of the cylinder in the X direction of the outer circle of the part, which is the highest in the X direction of the machining coordinate system and in the Y direction, and the values ​​of points 3 and 4 in the X direction, in mm; Step 3: Calculate the compensation value and compensate the coordinate system. Based on the measurement data, the compensation value is calculated by substituting it into the following formula χ=Δ×(a / b), and the calculated compensation value is then applied to the machine tool machining coordinate system. The units are all mm. When the compensation value is positive, compensation is made in the positive X direction, and when the compensation value is negative, compensation is made in the negative X direction. Where χ: machining coordinate system compensation value, a: length of the outer cylinder of the part, b: distance from the origin of the machining coordinate system to the axis of the key assembly hole of the part, where the origin of the machining coordinate system is at one end of the outer cylinder of the part; Step 4: Boring to the required dimensions: The key assembly holes are precision bored to the final dimensional requirements; The specific verification of the compensation direction is as follows: After completing the coordinate system compensation, run the machining program to rough bore the two sets of key assembly holes to a light-reflected state. After boring, leave a margin of 0.3mm to 0.4mm on each side. Use a machine tool probe to measure the symmetry between the two sets of holes and the outer cylinder of the part. Check whether it is close to the theoretical value that should be achieved after calculating the compensation value and completing the compensation machining. This is used to check whether the coordinate system compensation direction is correct. If the difference is large, it can be judged that the compensation direction is opposite, and the above steps need to be repeated for verification.

2. The machining method for ensuring the form and position tolerances of key assembly holes in long shaft-type parts according to claim 1, characterized in that, Step 2 involves in-machine measurement, which can be performed automatically using a machine tool probe.

3. The machining method for ensuring the form and position tolerances of key assembly holes in long shaft-type parts according to claim 1, characterized in that, The measurement error of the probe of the machine tool should be ≤0.015mm.

4. The machining method for ensuring the form and position tolerances of key assembly holes in long shaft-type parts according to claim 1, characterized in that, The specific operation of coordinate system compensation is as follows: Open the relevant interface for machine tool coordinate system settings, input the calculated compensation value into the X coordinate system precision column, and complete the machine tool coordinate system compensation.

5. A machining method for ensuring the form and position tolerances of key assembly holes in long shaft-type parts according to claim 1, characterized in that, The boring tool feed direction should be as perpendicular as possible to the XY plane of the machining coordinate system.

6. A machining method for ensuring the form and position tolerances of key assembly holes in long shaft-type parts according to claim 1, characterized in that, When boring, it is necessary to ensure that holes on the same axis are completed in one machining operation to improve the coaxiality of holes on the same axis.

7. A machining method for ensuring the form and position tolerances of key assembly holes in long shaft-type parts according to claim 1, characterized in that, When clamping the part, the inclination of the outer cylinder in the X direction of the coordinate system should be less than 0.05mm.

8. A machining method for ensuring the form and position tolerances of key assembly holes in long shaft-type parts according to claim 1, characterized in that, When clamping the part, the inclination of the outer cylinder in the Z direction of the coordinate system should be less than 0.03mm.

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