Method for machining power turbine stator blade by adopting six-point positioning numerical control milling machine

Abstract

The invention relates to a six-point positioning numerical control milling machine machining method for a power turbine stator blade, and aims at solving the problems that when the six-point positioning power turbine stator blade is machined, compression deformation needs to be prevented, the pressing force is not large, and an outer arc is prone to looseness in machining. The method comprises the following steps: respectively marking two points on the top of a blade root ring and the top of a blade crown ring of a to-be-processed end face of a blade blank, measuring the height positions of the four points to determine the fall of the four points, measuring the allowance of an air outlet side arc, moving the blade blank to a clamp, measuring the gap between the blade blank and a plurality of positioning points by using a feeler gauge, and aligning the fall of the four points, the method comprises the steps that a blade blank is machined, a heightening auxiliary part is inserted into a gap in the bottom of the blade blank, the original point of cutting of a tool is aligned according to the highest blank measuring point, other three points are machined according to the fall, a circular arc meeting the requirement is machined according to the measured allowance of the circular arc of the blade blank, and the circular arc meeting the technical requirement of the process size can be machined through one-time clamping.

Description

Technical Field

[0001] The present invention relates to the technical field of machining, and particularly relates to a machining method for a power turbine stationary blade by using six-point positioning on a numerically controlled milling machine. Background Art

[0002] Since the power turbine stationary blade is precision cast, with three precision casting points on the bottom surface, one point at the blade top, and two points in the air passage, six points are used to position the blade for machining the height difference and arc process on the outlet side. The position relative to the air passage and subsequent machining are all based on this positioning, and the machining accuracy has a certain impact on subsequent positioning and machining. Therefore, after machining, it is necessary to ensure the technical requirements, ensure the accuracy of the height difference and arc, so as to ensure the consistency of the machined air passage, improve efficiency, and reduce costs, etc.

[0003] For six-point positioning, the three points on the bottom surface are for positioning and also support points, with poor strength and stability. Vibration occurs during machining, and the flatness and parallelism of the two machined planes are unstable, resulting in low efficiency; the requirement is <0.10; there is one point for positioning under the blade top, with factors such as weakness and instability; moreover, it is difficult to machine thin parts with various tooth profiles. Therefore, when machining the power turbine stationary blade with six-point positioning, it is necessary to prevent pressing deformation, the clamping force is not very large, and the outer arc machining is prone to looseness. Summary of the Invention

[0004] The purpose of the present invention: The present invention is to solve the problems that when machining the power turbine stationary blade with six-point positioning, it is necessary to prevent pressing deformation, the clamping force is not very large, and the outer arc machining is prone to looseness. The present invention provides a machining method for a power turbine stationary blade by using six-point positioning on a numerically controlled milling machine.

[0005] The purpose of the present invention is achieved as follows: A machining method for a power turbine stationary blade by using six-point positioning on a numerically controlled milling machine, characterized in that it includes the following steps:

[0006] Step 1: Install the fixture on the numerically controlled milling machine while ensuring its levelness and height.

[0007] Step 2: Detect the heights of the three positioning points on the fixture, and ensure that the heights of the two left positioning points are the same and higher than the right positioning point.

[0008] Step 3: Place the blade blank on the measuring platform, mark two points respectively at the top of the blade root ring and the top of the blade crown ring on the end face of the blade blank to be machined, measure the height positions of the four points to determine the height difference of the four points, and determine the machining allowance at the positions of the four points by referring to the blade drawing.

[0009] Step 4: Measure the size of the allowance of the outlet side arc.

[0010] Step 5: Move the blade blank to the fixture and clamp it. Use a feeler gauge to measure the gaps between the blade blank and the three positioning points, between the highest point of the back arc of the blade blank and the cylindrical positioning pin, and between the blade root ring of the blade blank and the conical surface positioning, ensuring that a 0.03 mm feeler gauge cannot be inserted.

[0011] Step 6: Align the height difference based on the four points marked in Step 3, and insert a heightening auxiliary part at the bottom gap of the blade blank.

[0012] Step 7: During machining, based on the highest measured point of the blank, align the origin of the tool cutting, and then machine the other three points according to the height difference until the required dimensions and height difference are achieved, ensuring the parallelism requirement.

[0013] Step 8: Machine a conforming arc according to the size of the remaining arc of the measured blade blank, ensuring that the arc of the machined blade blank fits the measuring tool.

[0014] Further, in Step 2, a height gauge is used to measure the heights of the three positioning points.

[0015] Still further, in Step 3, a height gauge is used to measure the height positions of the four points.

[0016] Further, the heightening auxiliary part in Step 6 is made of iron sheet.

[0017] Still further, the bottom gap of the blade blank in Step 6 is located below the right positioning point.

[0018] Further, when aligning the height difference in Step 6, it is carried out by reading the dial indicator on the CNC milling machine.

[0019] Still further, when aligning the height difference in Step 6, it is carried out by reading the CNC Z-axis coordinate on the CNC milling machine.

[0020] Beneficial effects:

[0021] This method is a method for a CNC milling machine for machining the outlet side machining plane and outer arc processes of the static blades of a power turbine using six-point positioning, reducing multiple clamping and ensuring quality and improving processing efficiency.

[0022] The innovation of this method is applicable to the static blades of precision casting of power turbines. It mainly finds four points on the surface of the blank by measuring with measuring tools to find the height difference of the arc allowance, and on the CNC machine, uses a dial indicator to align the accurate position with the measuring tool through the four points, adjusts the shim, avoiding non-parallelism due to the clamping force when clamping the workpiece. According to the height difference of the four points and the actual dimension value of the measuring tool, machining is carried out to ensure the height difference and arc, and the blade that meets the process dimension technical requirements can be machined in one clamping. This method has high efficiency, avoids the errors caused by multiple clamping of workpieces, saves time and effort. It is convenient and fast to operate, has strong practicability, low cost, and high efficiency.

[0023] The innovation of this method is based on the characteristics of this fixture, which is applicable to the static blades of power turbine combustion pressure precision casting. According to the drop of four points, the actual size value of the measuring tool, and the accurate positioning and support after clamping at three points on the bottom surface, and ensure the accurate positioning of the other three points. Then carry out machining to ensure the drop and arc, and the process dimensions and technical requirements can be machined in one clamping. Brief Description of the Drawings

[0024] Figure 1 is the schematic clamping diagram of the blade blank of the present invention on the fixture;

[0025] Figure 2 is the top view of the blade blank of the present invention (the points in the figure are the positions for drawing points in step three);

[0026] Figure 3 is the bottom view of the blade blank of the present invention (the points in the figure are the positions to be supported by the positioning points in step two). Detailed Description of the Invention

[0027] Detailed Description of the Invention One: A method for machining a static blade of a power turbine by six-point positioning numerical control milling machine, which includes the following steps:

[0028] Step One: Install the fixture on the numerical control milling machine while ensuring its levelness and height;

[0029] Step Two: Detect the heights of the three positioning points 1 on the fixture, and ensure that the heights of the two left positioning points 1 are the same and higher than the right positioning point 1;

[0030] Step Three: Place the blade blank on the measuring platform, respectively take two points on the top of the blade root ring and the top of the blade crown ring on the end face to be machined of the blade blank, draw point marks, and measure the height positions of the four points to determine the drop of the four points, and determine the machining allowance at the positions of the four points by referring to the blade drawing;

[0031] Step Four: Measure the size of the allowance of the arc on the air outlet side;

[0032] Step Five: Move the blade blank to the fixture and clamp the blade blank. Use a feeler gauge to measure the gaps between the blade blank and the three positioning points 1, between the highest point of the back arc of the blade blank and the cylindrical positioning pin 2, and between the blade root ring of the blade blank and the conical surface positioning 3, and ensure that a 0.03 mm feeler gauge cannot enter.

[0033] Step Six: Align the drop based on the four points where the points are drawn in Step Three, and insert a padding auxiliary part at the gap at the bottom of the blade blank;

[0034] Step Seven: During machining, according to the highest measured point of the blank, align the origin of the tool cutting, and then according to the drop, machine the other three points until the required size and drop are achieved, and ensure the parallelism requirement;

[0035] Step Eight: Machine an arc that meets the requirements based on the measured surplus of the arc of the blade blank, ensuring that the arc of the blade blank after machining fits the measuring tool.

[0036] Specific Embodiment Two: A method for machining a power turbine stationary blade using a six-point positioning CNC milling machine. In Step Two, a height gauge is used to measure the heights of three positioning points 1.

[0037] Other embodiments are the same as Specific Embodiment One.

[0038] Specific Embodiment Three: A method for machining a power turbine stationary blade using a six-point positioning CNC milling machine. In Step Three, a height gauge is used to measure the height positions of four points.

[0039] Other embodiments are the same as Specific Embodiment One.

[0040] Specific Embodiment Four: A method for machining a power turbine stationary blade using a six-point positioning CNC milling machine. In Step Six, the auxiliary padding part is made of iron sheet.

[0041] In this embodiment: In Step Six, the auxiliary padding part is made of iron sheet, which is easily obtainable and various thickness consumables can be easily obtained.

[0042] Other embodiments are the same as Specific Embodiment One.

[0043] Specific Embodiment Five: A method for machining a power turbine stationary blade using a six-point positioning CNC milling machine. In Step Six, the bottom clearance of the blade blank is located below the right-side positioning point 1.

[0044] In this embodiment: In Step Six, the bottom clearance of the blade blank is located below the right-side positioning point. Since this solution uses three positioning points and the right-side positioning point is relatively high, the bottom of the blade blank may be suspended and a support needs to be padded in.

[0045] Other embodiments are the same as Specific Embodiment One.

[0046] Specific Embodiment Six: A method for machining a power turbine stationary blade using a six-point positioning CNC milling machine. In Step Six, when aligning the elevation difference, it is carried out by reading the reading of a dial indicator on the CNC milling machine.

[0047] In this embodiment: In Step Six, when aligning the elevation difference, it is carried out by reading the reading of a dial indicator on the CNC milling machine.

[0048] Other embodiments are the same as Specific Embodiment One.

[0049] Specific Embodiment Seven: A method for machining a power turbine stationary blade using a six-point positioning CNC milling machine. In Step Six, when aligning the elevation difference, it is carried out by reading the CNC Z-axis coordinate on the CNC milling machine.

[0050] Other embodiments are the same as Embodiment 1.

Claims

1. A machining method for a power turbine stationary blade using a six-point positioning CNC milling machine, characterized in that: It includes the following steps: Step 1: Install the fixture on the CNC milling machine while ensuring its levelness and height. Step 2: Detect the heights of the three positioning points (1) on the fixture, and ensure that the heights of the two left positioning points (1) are the same and higher than that of the right positioning point (1). Step 3: Place the blade blank on the measuring platform, mark two points respectively at the top of the root ring and the top of the crown ring on the end face of the blade blank to be machined, measure the height positions of the four points to determine the height difference of the four points, and determine the machining allowance at the positions of the four points with reference to the blade drawing. Step 4: Measure the size of the allowance of the outlet side arc. Step 5: Move the blade blank to the fixture and clamp the blade blank. Use a feeler gauge to measure the gaps between the blade blank and the three positioning points (1), between the highest point of the back arc of the blade blank and the cylindrical positioning pin (2), and between the root ring of the blade blank and the conical positioning (3), and ensure that a 0.03 mm feeler gauge cannot be inserted. Step 6: Align the height difference based on the four points marked in Step 3, and insert a heightening auxiliary part at the bottom gap of the blade blank. Step 7: During machining, based on the highest measured point of the blank, align the origin of the tool cutting, and then machine the other three points according to the height difference until the required dimensions and height difference are achieved, ensuring the parallelism requirement. Step 8: Machine a conforming arc according to the measured size of the arc allowance of the blade blank to ensure that the arc of the machined blade blank coincides with the measuring tool.

2. A machining method for a power turbine stationary blade by using a six-point positioning CNC milling machine according to claim 1, characterized in that: In Step 2, a height gauge is used to measure the heights of the three positioning points (1).

3. A machining method for a power turbine stationary blade by using a six-point positioning CNC milling machine according to claim 1, characterized in that: In Step 3, a height gauge is used to measure the height positions of the four points.

4. A machining method for a power turbine stationary blade using a six-point positioning CNC milling machine according to claim 1, characterized in that: The heightening auxiliary part in Step 6 is made of iron sheet.

5. A machining method for a power turbine stationary blade using six-point positioning CNC milling machine according to claim 1, characterized in that: The bottom gap of the blade blank in Step 6 is located below the right positioning point (1).

6. A machining method for a power turbine stationary blade using a six-point positioning CNC milling machine according to claim 1, characterized in that: When aligning the height difference in Step 6, it is carried out by reading the dial indicator on the CNC milling machine.

7. A machining method for a power turbine stationary blade using a six-point positioning CNC milling machine according to claim 1, characterized in that: When aligning the height difference in Step 6, it is carried out by reading the CNC Z-axis coordinate on the CNC milling machine.

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