A machining method for radial blade holes of a tubular turbine runner body

Abstract

The present invention relates to the technical field of machining of water turbine blade holes, and discloses a method for machining radial blade holes of a bulb turbine runner body, which includes the following steps: scribing, assembling, stretching, marking, re-scribing, and using numerical control program to control the movement of the table of a floor-type numerically controlled boring machine for fixed-point boring machining, successively performing fixed-point rough boring, semi-finish boring, and finish boring on each radial blade hole to the dimensions in the drawing, and inspecting. It meets the requirements of the machining dimensions, geometric tolerance precision, and roughness of the runner body blade holes.

Description

Technical Field

[0001] The present invention relates to the technical field of water turbine blade hole machining, and particularly relates to a method for machining radial blade holes of a bulb turbine runner body. Background Art

[0002] As the core component of a water turbine, the runner body of a bulb turbine is usually machined by a boring bar moving horizontally. Chinese patent document CN110125630B discloses a method for machining blade pivot holes of a runner body of a Kaplan turbine, including steps such as scribing, rough turning, finish turning, rough boring, finish boring each blade hole, performing Hawkener machining on an upright lathe, and grinding machining.

[0003] The existing technology has the following deficiencies: In this machining method, due to factors such as the deflection difference of the boring bar itself and the equipment accuracy during the machining cutting operation, there is a possibility that the boring hole is not stressed and the hole centers are not concentric. Therefore, the machining dimensions, geometric tolerance accuracy, and surface roughness of the blade holes of the runner body cannot meet the design requirements. Summary of the Invention

[0004] In order to solve the technical problem of poor machining accuracy of the boring bar, the present invention provides a method for machining radial blade holes of a bulb turbine runner body, which is characterized by including the following steps:

[0005] Step 1: Provide a semi-finished runner body with its upper plane, lower plane, outer circle of the stop, stop plane, and semi-finished spherical surface having been finish-machined.

[0006] Step 2: Scratch the central cross line, make ±X marks and ±Y marks, and scratch the machining lines of each semi-circular radial blade hole of the runner body.

[0007] Step 3: Assemble the piston rod, annular key, and runner body into one body with bolts and nuts.

[0008] Step 4: Stretch three times according to the pre-tightening torque value provided by the product.

[0009] Step 5: Make alignment marks for each radial blade hole of the runner body and the piston rod.

[0010] Step 6: Re-scratch the central cross line and scratch the machining lines of each radial blade hole.

[0011] Step 7: Place the entire runner body on the rotary worktable of the equipment, align it with the rotary worktable coaxially, align the center of the rough-machined hole and the plane of the runner body, and control the movement of the worktable of the floor-type CNC boring machine by a numerical control program to perform fixed-point boring machining. Sequentially perform fixed-point rough boring, semi-finish boring, and finish boring each radial blade hole to the drawing dimensions.

[0012] Step 8: Check the concentricity and flatness of each radial blade hole, and check the dimensions of each radial blade hole.

[0013] Step 9: Disassemble the bolts, nuts, ring keys and piston rods;

[0014] Step 10: Deburr, remove flash, and perform rust prevention treatment on the machined surface.

[0015] Preferably, in step 3.1, first clean the mating surfaces of the piston rod, bolts, nuts and ring keys.

[0016] Preferably, in step 3.2, after assembly, perform cold pre-tightening, heat stretching and re-tightening treatment on the bolts.

[0017] Preferably, in step 3.3, after the tightening treatment, apply grease to the threads of the bolts, heat them simultaneously with an electric heating rod, and tighten the runner body and the piston rod at the same time to eliminate the gap. Use a feeler gauge to check that the contact surface gap between the runner body and the piston rod does not exceed 0.02 mm.

[0018] Preferably, in step 7, align it with the rotary table coaxially, with the requirement that the error ≤ 0.03 mm.

[0019] Preferably, in step 8, mount a dial indicator on the boring bar and rotate it for one week to check the concentricity and flatness of each radial blade hole, including checking the size of each radial blade hole with an internal micrometer.

[0020] The present invention has the following beneficial effects:

[0021] 1. In the prior art, due to the fact that the boring bar extends too long and the moving boring bar has the possibility of uneven boring force and non-concentric hole centers due to factors such as the deflection difference of the boring bar itself and the equipment accuracy during its machining and cutting working state; while the runner body of the present application adopts a structural form of split radial blade holes, connects the runner body and the piston rod by positioning through a spigot and a precision mating hole, and controls the movement of the table of the floor-type CNC boring machine through a numerical control program for fixed-point boring machining, reducing the non-concentricity of each machined blade hole caused by the movement of the boring bar, and realizing rough and finish boring of each radial blade hole in sequence through the numerical control program controlling the center indexing of the boring machine table, meeting the requirements of the machining dimensions, geometric tolerance accuracy and roughness of the runner body blade holes. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of an embodiment of the method for machining the radial blade holes of the runner body of the tubular turbine of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The following is a further detailed description through specific embodiments:

[0024] 1. The reference numerals in the accompanying drawings of the specification include: piston rod 1, nut 2, bolt 3, ring key 4, runner body 5, rotary table 6.

[0025] Example 1

[0026] As Figure 1 shown, a method for machining radial blade holes of a tubular turbine runner body includes the following steps:

[0027] Step 1: Provide a semi-finished runner body 5 with its upper plane, lower plane, outer circle of the spigot, spigot plane, and semi-finished spherical surface having been finely machined;

[0028] Step 2: Draw a central cross line, make ±X marks and ±Y marks, and draw the machining lines for each semi-circular radial blade hole of the runner body 5;

[0029] Step 3: Clean the mating surfaces of the piston rod 1, bolt 3, nut 2, and annular key 4. Assemble the piston rod 1, annular key 4, and runner body 5 into one body with bolts 3 and nuts 2, and perform cold pre-tightening, heating and stretching, and re-tightening treatments on the bolts 3. Apply molybdenum disulfide grease to the threads of the bolts 3. Heat them simultaneously with electric heating rods, and tighten the runner body 5 and the piston rod 1 at the same time to eliminate the clearance. Use a feeler gauge to check that the contact surface clearance between the runner body 5 and the piston rod 1 does not exceed 0.02 mm;

[0030] Step 4: Stretch in three times according to the pre-tightening torque value provided by the product. Since the bolts 3 have springback after stretching, for the last stretching, the stretching value can be appropriately processed to meet the total elongation value required to ensure the product design requirements;

[0031] Step 5: Make alignment marks for each radial blade hole between the runner body 5 and the piston rod 1;

[0032] Step 6: Re-draw the central cross line and draw the machining lines for each radial blade hole;

[0033] Step 7: Place the entire runner body 5 on the rotary table 6 of the equipment, align it with the rotary table 6 coaxially, with the requirement that the error ≤ 0.03 mm. Align the center and plane of the roughly machined holes of the runner body 5. Control the movement of the table of the floor-type CNC boring machine with the CNC program to perform fixed-point boring machining, and successively perform fixed-point rough boring, semi-finish boring, and finish boring on each radial blade hole to the dimensions shown in the drawing;

[0034] Step 8: Mount a dial indicator on the boring bar and rotate it one week to check the concentricity and flatness of each radial blade hole, including checking the dimensions of each radial blade hole with an internal micrometer;

[0035] Step 9: Disassemble the bolts 3, nuts 2, annular key 4, and piston rod 1;

[0036] Step 10: Remove burrs and flash, and perform rust prevention treatment on the machined surface;

[0037] The above are only embodiments of the present invention. Common knowledge such as specific structures and characteristics well-known in the art are not described in detail herein. Those of ordinary skill in the art know all the common general technical knowledge in the technical field to which the invention pertains before the filing date or the priority date, are able to learn all the prior art in this field, and have the ability to apply conventional experimental means before this date. Those of ordinary skill in the art can, under the inspiration given in this application and in combination with their own abilities, improve and implement this solution. Some typical well-known structures or well-known methods should not become an obstacle for those of ordinary skill in the art to implement this application. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can still be made, and these should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope claimed in this application shall be subject to the content of its claims, and the specific implementation manners and the like recorded in the specification can be used to interpret the content of the claims.

Claims

1. A method for machining radial blade holes of a bulb turbine runner body, characterized in that, It includes the following steps: Step 1: Provide a semi-finished runner body with its upper plane, lower plane, outer diameter of the rabbet, rabbet plane, and semi-finished spherical surface having been finely machined; Step 2: Draw a central cross line, make ±X marks and ±Y marks, and draw the processing lines for each semi-circular radial blade hole of the runner body; Step 3: Assemble the piston rod, annular key, and runner body into one body with bolts and nuts; Step 4: Stretch it three times according to the pre-tightening torque value provided by the product; Step 5: Make alignment marks for each radial blade hole between the runner body and the piston rod; Step 6: Re-draw the central cross line and draw the processing lines for each radial blade hole; Step 7: Place the whole runner body on the rotary worktable of the equipment, align it coaxially with the rotary worktable, align the center of the roughly machined hole and the plane of the runner body, control the movement of the worktable of the floor-type CNC boring machine by the CNC program for fixed-point boring, and successively perform fixed-point rough boring, semi-finish boring, and finish boring on each radial blade hole to the dimensions shown in the drawing; Step 8: Check the concentricity and flatness of each radial blade hole, and check the dimensions of each radial blade hole; Step 9: Disassemble the bolts, nuts, annular key, and piston rod; Step 10: Remove burrs and flash, and perform rust prevention treatment on the processed surface.

2. The machining method for the radial blade holes of a tubular turbine runner body according to claim 1, characterized in that: Step 3.1: First, clean the mating surfaces of the piston rod, bolts, nuts, and annular key.

3. The method for machining the radial blade holes of a tubular turbine runner body according to claim 2, characterized in that: Step 3.2: After assembly, perform cold pre-tightening, heating and stretching, and re-tightening on the bolts.

4. The method for machining radial blade holes of a tubular turbine runner body according to claim 3, characterized in that: Step 3.3: After the tightening treatment, apply grease to the threads of the bolts, heat them simultaneously with an electric heating rod, and tighten the runner body and the piston rod at the same time to eliminate the gap. Use a feeler gauge to check that the contact surface gap between the runner body and the piston rod does not exceed 0.02 mm.

5. The machining method for the radial blade holes of a tubular turbine runner body according to any one of claims 1-4, characterized in that: In Step 7, the coaxial alignment with the rotary worktable is required to have an error ≤ 0.03 mm.

6. The machining method for the radial blade holes of the bulb turbine runner body according to claim 5, characterized in that: In Step 8, mount a dial indicator on the boring bar and rotate it one week to check the concentricity and flatness of each radial blade hole, and use an internal micrometer to check the dimensions of each radial blade hole.

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