A machining method for a precise hole of a casing mounting edge and a casing mounting edge

Abstract

A kind of processing method of precision hole of housing mounting edge and housing mounting edge, comprising the following steps: making drill jig, by centering and angular positioning, the drill jig made is installed to housing mounting edge;According to the fixed angular position of drill jig, using center drill to punch center hole, drill bottom hole in the position of center drill hole of mounting edge;Using different precision tapper to carry out rough tapper hole and fine tapper hole;After disassembling drill jig, the part is clamped on numerical control machining center and is reamed by reamer;Measure aperture and position degree.The present application first rough machining is cooperated with drill jig by rocker arm drill, guarantees the position degree and perpendicularity of hole by drilling and tappering, and the aperture size is guaranteed by fine reaming of machining center, finally realizes the stable machining of precision hole, improves processing efficiency and qualified rate.

Description

Technical Field

[0001] This invention belongs to the technical field of casing mounting edge, and specifically relates to a method for processing precision holes in casing mounting edge and a casing mounting edge. Background Technology

[0002] In the structure of modern gas turbine casings and ring-shaped parts, intermediate mounting edges are often designed. Due to the structural limitations and interference of the end mounting edges, slender cutting tools must be selected when machining the intermediate mounting edges. These tools have poor rigidity and machining stability, often resulting in out-of-tolerance precision hole diameters and difficulty in ensuring positional accuracy. A certain gas turbine high-pressure compressor casing has a large external dimension, with the main material being 1Cr12Ni3MoVN. Its structure is a conical split casing, with mounting edges at both ends and in the middle. The intermediate mounting edge has 42 ф12+0.018 0 mm and 8 ф11 mm+0.018 0 precision holes. The tool length-to-diameter ratio is approximately 30, which is considered long overhanging hole machining.

[0003] In the early stages, two common methods were used to machine the precision holes in the middle mounting edge of this type of casing:

[0004] First, radial drilling machines are used in conjunction with drill jigs for machining. The drill jig and its associated cutting tools are used on the radial drilling machine for drilling, countersinking, and turning. During machining, the cutting tool needs to be struck each time it is removed from the tool holder, causing a circumferential runout of 0.2–0.4 mm. Furthermore, there is a gap after the radial drilling spindle is locked, resulting in poor tool stability and a high risk of runout. Second, there is a gap between the part's positioning surface and the drill jig's contact surface, which easily traps metal chips during machining, causing scratches and grooves on the hole wall. This machining method also makes it difficult to observe the tool's entry and exit points. Due to the presence of the drill jig, it is difficult to observe the machining process inside the hole, leading to easily out-of-tolerance hole diameters and poor surface finish.

[0005] Secondly, special tools are used for machining in CNC machining centers. Due to the limitations of the part structure and the large diameter-to-length ratio of the selected tool, this machining method often results in problems such as vibration and runout, which can easily cause the hole diameter to exceed the tolerance and the positional accuracy to be unqualified. Furthermore, when machining a large number of precision holes, the machining stability is poor, and individual hole diameters often exceed the tolerance.

[0006] Both of the above methods will result in varying degrees of quality problems when machining precision holes for intermediate mounting edges. In particular, the remedial measures after the positioning precision holes exceed the tolerance are complicated and special connecting bolts must be used. Otherwise, the assembly accuracy will be affected, and in more serious cases, the parts will be scrapped. Therefore, the hole diameter and positional dimensions must be qualified. Summary of the Invention

[0007] The purpose of this invention is to provide a method for machining precision holes on the mounting edge of a casing and the mounting edge itself, in order to solve the problem that remedial measures for precision holes that are out of tolerance are complicated and require specially made connecting bolts, otherwise the assembly accuracy will be affected, and in more serious cases, the parts will be scrapped.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for machining precision holes on the mounting edge of a casing includes the following steps:

[0010] Fabricate a drill jig, and install the fabricated drill jig onto the mounting edge of the housing by centering and angular positioning;

[0011] Drill a center hole using a center drill according to the fixed angular position of the drill jig, and drill a bottom hole at the position where the center hole was drilled on the installation side.

[0012] Use countersinks of different precision for rough countersinking and fine countersinking;

[0013] After disassembling the drill jig, the part is clamped on a CNC machining center and the hole is reamed using a reamer;

[0014] Measure the aperture and position.

[0015] Furthermore, centering relies on the outer circle of the mounting edge in the middle of the casing, while angular positioning relies on the characteristic position of the casing or the angular hole reserved by the drill jig.

[0016] Furthermore, when drilling the center hole using a radial drill, use a center drill to drill the center hole to a depth of 0.5-1mm, according to the fixed angular position of the drill jig.

[0017] Furthermore, when drilling the pilot hole with a radial drilling machine, a drill bit 1.4-1.6mm smaller than the diameter of the machining hole is used to drill the pilot hole at the position of the center drill hole on the mounting edge.

[0018] Furthermore, rough countersinking using a radial drilling machine: use a countersink cutter with a diameter 0.7-0.9 mm smaller than the diameter of the hole to be machined;

[0019] Radial arm drilling for precision counterboring: using a counterboring cutter 0.1-0.2mm smaller than the diameter of the hole to be machined for precision counterboring.

[0020] Furthermore, when disassembling the drill jig, clean up the metal filings; use the hole machined by the radial drilling machine to find the angular direction, ensuring the consistency of the angular direction of the two machining operations, and clamp the part on the CNC machining center.

[0021] Furthermore, before reaming the hole with a reamer:

[0022] The tool holder diameter is designed to have a clearance of 1-2mm between it and the outer circle of the workpiece; the tool's runout on the machining center after clamping is no more than 0.03mm; a left-handed carbide reamer is selected.

[0023] Furthermore, before reaming, perform trial cutting on a test piece of the same material or at a location with a large hole diameter on the part, select a reamer that meets the hole diameter requirements, and test to obtain stable cutting parameters.

[0024] Furthermore, when reaming, a reamer that has already undergone trial cutting is used.

[0025] Furthermore, a casing mounting edge includes a casing mounting edge with precision holes obtained by a method for machining precision holes in a casing mounting edge.

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] This invention first uses a radial drilling machine with a drill jig for rough machining, and then uses drilling and counterboring to ensure the position and perpendicularity of the hole. Finally, a machining center performs precision reaming to ensure the hole diameter, thereby achieving stable machining of precision holes and improving machining efficiency and yield.

[0028] This process, employing a radial drilling machine for rough drilling and countersinking to ensure the positional and perpendicularity of the holes, followed by precision reaming in a machining center to guarantee the hole diameter, ultimately achieved stable machining of the long overhanging precision holes on the mounting side of the casing, meeting the part's machining requirements. This method solves the machining problem of low yield rates for precision holes with large length-to-diameter ratios on the mounting side of the casing, avoiding previously common issues with hole diameter and positional tolerances, and significantly improving part yield and machining efficiency. This method can be applied to the machining of long overhanging precision holes in various models. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the high-pressure casing structure of a gas turbine.

[0030] Figure 2 Schematic diagram of high-pressure casing drilling jig. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings:

[0032] Please see Figures 1 to 2 The purpose of this invention is to provide a machining method that combines radial drilling for roughing and machining center for long overhanging holes with large length-to-diameter ratios on the mounting side of the casing. First, the radial drilling is used in conjunction with the drill jig for roughing. The position and perpendicularity of the hole are ensured by drilling and counterboring. The hole is then precision reamed by the machining center to ensure the hole diameter. Finally, the stable machining of the precision hole is achieved, improving the machining efficiency and yield.

[0033] This method is implemented through the following steps:

[0034] (1) Making a drilling jig: Design a drilling jig for the middle mounting edge according to the structural characteristics and processing characteristics of the workpiece. The drilling jig should be easy to disassemble and assemble.

[0035] (2) Installing the drill jig: centering relies on the outer circle of the mounting edge in the middle of the casing, and angular positioning relies on the characteristic position of the casing or the reserved angular hole.

[0036] (3) Drill the center hole with a radial drilling machine: Drill the center hole with a depth of 0.5-1mm according to the fixed angular position of the drill jig.

[0037] (4) Drilling the pilot hole with a radial drilling machine: Use a drill bit that is 1.4-1.6mm smaller than the diameter of the machined hole to drill the pilot hole at the position of the center drill hole on the installation side.

[0038] (5) Radial drilling for rough counterboring: Use a counterboring cutter that is 0.7-0.9 mm smaller than the diameter of the hole to be machined for rough counterboring.

[0039] (6) Radial arm drilling for precision counterboring: using a counterboring cutter 0.1-0.2mm smaller than the diameter of the hole to be machined for precision counterboring.

[0040] (7) Disassemble the drill jig: Disassemble the drill jig and clean up the iron filings.

[0041] (8) Clamping and alignment of machining center: Use the hole machined by the radial drilling to find the angular direction, ensure the consistency of the angular direction of the two machining operations, and clamp the part on the CNC machining center.

[0042] (9) Design of precision reaming tools:

[0043] a. Considering the radius difference between the machining position of the hole and the interference position of the part, in order to avoid scratches caused by the runout of the outer circle of the mounting edge of the small end of the part during the machining process, and to increase the rigidity as much as possible, a thicker extension rod is selected. The diameter of the tool bar is designed to be 1-2mm away from the outer circle of the interference of the part.

[0044] b. Considering the impact of runout on the hole diameter during the precision hole machining process of the reamer, a powerful hydraulic tool holder is selected to ensure that the tool's runout on the machining center after clamping is no more than 0.03mm.

[0045] c. Considering the part structure and the location of the coolant outlet after the tool is clamped, the machined hole is a through hole structure. Therefore, a left-hand carbide reamer is selected to ensure timely removal of iron filings in the event of poor cooling effect.

[0046] (10) Trial reaming: On a test piece of the same material or at a location with a large hole diameter, perform trial cutting, select a reamer that meets the hole diameter requirements, and test stable cutting parameters.

[0047] (11) Reaming: Reaming is performed using a reamer that has been tested.

[0048] (12) Measure the aperture and position.

[0049] The above method first uses a radial drilling machine with a drill jig to remove excess material from the hole. Due to the slender shape and poor rigidity of the cutting tool, the drill jig ensures the positional and perpendicularity requirements of the bottom hole. There is sufficient margin between the drill bit diameter and the final hole diameter to eliminate the increase in hole diameter caused by drill bit wobbling. Counterboring is divided into rough counterboring and fine counterboring. The hole position is further corrected through two counterboring operations. After counterboring, there is still a margin of 0.1-0.2mm from the final hole diameter. Since the machining allowance of the counterboring tool is small, its wobbling will not cause the final hole diameter to exceed the tolerance. The excess material in the hole is removed within the maximum range, ensuring the hole positional requirements while meeting the hole diameter requirements, creating conditions for qualified reaming. After fine counterboring with the radial drilling machine, the part is machined using a CNC machining center after removing the drill jig. Finally, a reasonably designed fine reaming tool is used to ensure the final hole diameter.

[0050] Example:

[0051] Figure 1 This is a schematic diagram of the high-pressure casing structure of a gas turbine. 42 φ120 mm sections need to be machined along the middle mounting edge. +0.018 mm, 8 x 11mm0 +0.018 Precision hole.

[0052] Process 42 ф120 +0.018 The mm method is as follows:

[0053] 1. Making a drilling jig ( Figure 2 As shown): Based on the structure of the part and the workpiece processing content, a drill jig is designed with the outer circle and end face of the middle mounting edge of the high-pressure casing for positioning.

[0054] 2. Install the drill jig: Install the drill jig on the middle mounting side of the casing, and determine the assembly angle of the drill jig based on the joint seam of the split casing.

[0055] 3. Drill the center point with the radial drilling machine: Drill the center point according to the hole position on the drill jig, to a depth of 1mm.

[0056] 4. Drilling with a radial drilling machine: Use a φ10.4mm drill bit to drill holes.

[0057] 5. Radial drilling for rough countersinking: Use a φ11.2mm countersink to rough countersink.

[0058] 6. Radial arm drilling for precision countersinking: Use a ф11.85mm countersink for precision countersinking.

[0059] 7. Disassemble the drill jig: Remove the bolts, disassemble the drill jig, and clean up the metal filings.

[0060] 8. Clamping and alignment: Clamp and tighten the part in the CNC machining center, and check that the runout of the end face of the part is not greater than 0.03.

[0061] 9) Trial reaming: Perform trial cutting on a test piece of the same material and select a ф12 reamer that passed the test plate machining.

[0062] 10) Fine reaming: Reaming is performed in a machining center using a ф12 reamer that has already undergone trial cutting.

[0063] 11) Use an inside micrometer to measure the bore diameter and a position gauge to check the position.

[0064] This method combines radial drilling jig machining with CNC machining. The jig is used for rough machining to ensure positional and perpendicularity requirements, while a small allowance is left for CNC equipment to ultimately ensure the dimensions. This facilitates the observation and measurement of each hole and allows for the timely detection of tool wear and abnormalities.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for machining precision holes on the mounting edge of a casing, characterized in that, Includes the following steps: Fabricate a drill jig, and install the fabricated drill jig onto the mounting edge of the housing by centering and angular positioning; Drill a center hole using a center drill according to the fixed angular position of the drill jig, and drill a bottom hole at the position where the center hole was drilled on the installation side. Use countersinks of different precision for rough countersinking and fine countersinking; After disassembling the drill jig, the part is clamped on a CNC machining center and the hole is reamed using a reamer; Measuring aperture and position; Centering relies on the outer circle of the mounting edge in the middle of the casing, while angular positioning relies on the characteristic position of the casing or the angular hole reserved in the drill jig; When drilling the center hole using a radial drill, use a center drill to drill the center hole to a depth of 0.5-1mm, according to the fixed angular position of the drill jig. When drilling the pilot hole with a radial drilling machine, a drill bit 1.4-1.6mm smaller than the diameter of the machining hole is used to drill the pilot hole at the position of the center drill hole on the mounting edge; Radial drilling for rough countersinking: Use a countersink cutter 0.7-0.9mm smaller than the diameter of the hole to be machined for rough countersinking; Radial arm drilling for precision counterboring: using a counterboring cutter 0.1-0.2mm smaller than the diameter of the hole to be machined for precision counterboring; When disassembling the drill jig, clean up the metal filings; use the hole machined by the radial drilling machine to find the angular direction, ensuring the consistency of the angular direction between the two machining operations, and then clamp the part on the CNC machining center.

2. The method for machining precision holes on the mounting edge of a casing according to claim 1, characterized in that, Before reaming with a reamer: The tool holder diameter is designed to have a clearance of 1-2mm between it and the outer circle of the workpiece; the tool's runout on the machining center after clamping is no more than 0.03mm; a left-handed carbide reamer is selected.

3. The method for machining precision holes on the mounting edge of a casing according to claim 1, characterized in that, Before reaming, perform trial cutting on a test piece of the same material or at a location with a large hole diameter on the part, select a reamer that meets the hole diameter requirements, and test to obtain stable cutting parameters.

4. The method for machining precision holes on the mounting edge of a casing according to claim 3, characterized in that, When reaming, use a reamer that has already been test-cut.

5. A casing mounting edge, characterized in that, This includes a casing mounting edge with precision holes obtained by a machining method for precision holes in a casing mounting edge as described in any one of claims 1 to 4.

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