A method for processing a short section body of a difficult-to-machine material for a logging-while-drilling

Abstract

The application provides a machining method for a short section body of a difficult-to-machine material for logging while drilling, and belongs to the field of machining manufacturing. According to the material performance and the structural characteristics of the workpiece, the tool path trajectory is optimized, the tool and the process parameters are optimized for different machining processes, and the machining of the short section body of the difficult-to-machine material for logging while drilling is realized. After the application is used, the production and machining efficiency is improved by 20%, and the tool cost is reduced by 15%. Moreover, the high-pressure sealing capacity of the product machined by the application reaches 140Mpa, the annual service footage of the near-bit gamma imaging system iSPEED reaches 10141m, the total service time reaches 1820h, and the well condition demand is met.

Description

Technical Field

[0001] This invention belongs to the field of mechanical processing and manufacturing, specifically relating to a processing method for a short section body made of difficult-to-machine materials for logging while drilling, used to process a complex structure short section body made of high-nitrogen chromium manganese nickel austenitic stainless steel for well tools used in the petroleum machinery engineering industry for logging while drilling. Background Technology

[0002] With the deepening of oil and gas exploration and development, directional and horizontal well technologies have been widely used in the efficient development of unconventional oil and gas resources such as shale gas and tight oil. Logging while drilling (MWD / LWD) is the main means of exploration and development for extended-range directional wells, horizontal wells, and other special-process wells, and has developed into a core technology of drilling operations. As the core functional carriers of logging while drilling instruments, such as the near-bit sub body and resistivity sub body, which are developed using integrated mechanical, electrical, hydraulic, and control technologies, these components must meet the mechanical performance and structural characteristics requirements of downhole instruments.

[0003] High-nitrogen, chromium-manganese-nickel austenitic stainless steel P550 is a commonly used material in logging-while-drilling (LWD) instruments. It possesses high wear resistance and toughness, as well as high corrosion resistance in drilling environments. It is frequently used to manufacture non-magnetic drill collars, LWD instruments, rotary steerable drilling tools, stabilizers, and other products. The excellent mechanical properties of P550 not only protect the electronic components in the equipment but also significantly reduce the frequency of equipment maintenance and maintenance costs. However, due to its low thermal conductivity, high high-temperature chemical activity, and high hardness, P550 is a typical difficult-to-machine material. Its high hardness and viscosity lead to easy chip adhesion and a strong tendency for work hardening.

[0004] The main body of the series of logging-while-drilling instruments is the core functional carrier of the logging-while-drilling instruments. Its structure is complex and requires the assembly of electronic chips, micro motors, motors, cables, wires, etc. for the collection of data from downhole oil drilling and production equipment. It has high requirements for sealing and corrosion resistance, is difficult to CNC machine, and lacks optimal cutting parameters and machining process experience, resulting in low machining efficiency and unstable quality. Multi-dimensional irregular curved surface cavities and arc grooves experience significant impact and vibration during milling, and chips easily adhere to the milling cutter teeth, making cutting conditions extremely harsh. Due to the large amount of material removed and the poor thermal conductivity of the material, a large amount of cutting heat accumulates inside the workpiece, and stress release can easily lead to part deformation, poor sealing performance, and even part scrap. "V"-shaped butt joints with "straw diameter" sizes of inclined deep holes, ultra-fine long deep holes (depth-to-diameter ratio ≥25) with a diameter of 5mm and a depth of 225-400mm, are difficult to machine, have problems with chip breaking and removal, and are prone to diameter deviation, making it impossible to meet the assembly requirements of cables and wires. Small diameter blind hole threads with M≤6 have problems such as not being able to be tapped, tap seizing, and easy breakage, resulting in high tool wear.

[0005] Chinese patent publication CN102921985A discloses a method for machining deep small holes with large angles in difficult-to-machine materials. This method involves adding a cutting force balancing guide plate with appropriate thickness, excellent cutting performance, good positioning fit, and tight contact with the workpiece to the workpiece. A large-diameter milling cutter is then used to mill an inclined surface perpendicular to the hole's central axis on the guide plate, transforming the machining of deep small inclined holes into ordinary deep small hole machining. This solves the problems of chip breaking, chip removal, chip evacuation, tool deflection, tool vibration, tool breakage, and rough entry surface and non-compliance with length dimensions during the machining of large angles and deep small holes in difficult-to-machine materials. It provides reliable technical support for surface integrity machining and fatigue-resistant manufacturing, and provides a prerequisite guarantee for improving the service life and safety of parts.

[0006] Chinese patent publication CN106826463B discloses a method for processing complex curved surfaces, comprising: 1. Removing material from the complex curved surface using a stress disk until the peak-to-valley value of the surface shape error is better than 30 μm; 2. Performing error analysis on the surface shape of the complex curved surface, processing low-order errors of the entire surface shape better than 30 μm using a stress disk, and processing mid-to-high frequency errors of the entire surface shape better than 30 μm using a small grinding head, until the RMS value of the surface shape error is better than 100 nm; 3. Performing error analysis on the surface shape error of the complex curved surface, processing low-order errors with an RMS value better than 100 nm using a stress disk, processing local mid-to-high frequency errors or annular errors at this precision using a small grinding head, and processing mid-to-high frequency errors of the entire surface shape at this precision using magnetorheological methods; until the RMS of the surface shape error of the complex curved surface is better than 30 nm; 4. Processing the complex curved surface using ion beam processing technology until the requirements are met, achieving high surface shape convergence efficiency.

[0007] Chinese patent publication CN111413923B discloses a high-speed precision machining method for complex curved surfaces. The method first acquires the geometric model of the workpiece, the tool profile image, and initial cutting parameters. Based on the characteristics of the surface to be machined, a surface machining tool path is generated, and this path is optimized to obtain the final optimized toolpath. A dual neural network optimization algorithm for complex surface cutting parameters is used, with cutting time, energy consumption, and the surface roughness of the workpiece as optimization objectives, to establish an optimal model for high-speed machining cutting parameters of complex curved surfaces. This model optimizes the initial cutting parameters to obtain the optimal cutting parameters. Finally, the optimized toolpath and optimized cutting parameters are post-processed to generate CNC code.

[0008] However, the patents mentioned above are not applicable to the high-hardness, high-viscosity, and difficult-to-machine material P550, as well as complex structural features. Currently, logging-while-drilling instruments face the dual challenges posed by difficult-to-machine structures and materials. They cannot meet industrialization requirements in terms of product quality control, processing methods, equipment, and personnel, resulting in low efficiency, high costs, and hindering market response speed.

[0009] Therefore, there is an urgent need to study an efficient cutting method for complex structural features of non-magnetic stainless steel P550, such as complex curved surfaces, deep hole drilling, and small-diameter thread tapping. Summary of the Invention

[0010] The purpose of this invention is to solve the problems existing in the prior art and provide a processing method for a short section body made of difficult-to-machine material for logging while drilling. This method enables the optimization of different structural equipment and process tools, improves the clamping, positioning and processing methods of parts, optimizes the process flow, adopts the principle of decreasing allowances in roughing, semi-finishing and finishing, and rationally arranges aging treatment methods to prevent deformation of parts during processing.

[0011] This invention is achieved through the following technical solution:

[0012] This invention provides a method for machining a short section body made of difficult-to-machine material for logging while drilling. The method optimizes the tool path trajectory, selects the best tools and process parameters for different machining processes based on the material properties and workpiece structural characteristics, thereby realizing the machining of the short section body made of difficult-to-machine material for logging while drilling.

[0013] A further improvement of the present invention is that:

[0014] The method includes:

[0015] (1) Feeding;

[0016] (2) Drilling and boring holes;

[0017] (3) Milling complex cavities;

[0018] (4) Tap small-diameter threads;

[0019] (5) Machining a 60° angled high-pressure sealing step hole;

[0020] (6) Machining radial high-pressure sealing holes;

[0021] (7) Machining ultra-fine long deep holes.

[0022] A further improvement of the present invention is that:

[0023] The operation of step (1) includes:

[0024] Keep the material perpendicular to the saw blade, and use a stainless steel saw blade;

[0025] The cutting parameters are 40 m / min.

[0026] A further improvement of the present invention is that:

[0027] The operation of step (2) includes:

[0028] (21) After clamping the workpiece on a conventional lathe, drill the inner hole;

[0029] (22) Rough boring and fine boring of the inner hole: rough boring of the inner hole using an integral carbide boring tool; semi-finish turning of the outer circle with the inner hole as the reference, then fine boring of the inner hole with the outer circle as the reference, and finally fine turning of the outer circle with the finely bored inner hole as the reference, so that the inner hole and the outer circle are references to each other, and the deviation of the hole axis is controlled within 0.5mm / 1000mm.

[0030] Preferably, the cutting parameters for rough boring are as follows: spindle drilling speed is 50 r / min, and feed rate is 12 mm / min;

[0031] The cutting parameters for precision boring are as follows: spindle speed is 42 r / min, and feed rate is 10 mm / min.

[0032] A further improvement of the present invention is that:

[0033] The operation of step (3) includes:

[0034] (31) Rough milling: Use a fast feed ball end mill to rough mill the cavity;

[0035] (32), Aging: Natural static aging for 4 to 5 hours to relieve stress;

[0036] (33) Semi-finish milling: Use a contour ball end mill to semi-finish mill each semi-circular arc cavity;

[0037] (34) Finish-machined sealing surface: Finish-machine the IT7 grade sealing surface at the mating point with the Inconel 718 alloy sleeve;

[0038] (35) Finish milling: Use a φ6 milling cutter to finish mill each semi-circular arc cavity.

[0039] Preferably, step (35) includes the following operations:

[0040] After replacing the tool holder and collet, perform finish milling. During finish milling, ensure that only the bottom edge makes contact with the material and check the runout of the cutting teeth.

[0041] Preferably, when performing rough milling in step (31), the machine tool speed is 38 m / min, the milling feed rate is 0.3 mm / r, and the depth of cut is 1.5 mm; the rough milling leaves a machining allowance of 1 to 2 mm for the semi-finish milling.

[0042] When performing semi-finish milling in step (33), the machine tool speed is 45 m / min, the milling feed rate is 0.25 mm / r, the depth of cut is 0.15 mm, and the semi-finish milling leaves a machining allowance of 0.1 to 0.25 mm for finish milling;

[0043] When performing fine milling in step (35), the machine tool speed is 60 m / min, the milling feed rate is 0.01 mm / r, and the depth of cut is 1 mm.

[0044] A further improvement of the present invention is that:

[0045] The operation of step (4) includes:

[0046] (41) Clamp the workpiece on the milling and turning machining center and perform point hole positioning;

[0047] (42) Drilling the bottom hole with a motor;

[0048] The operation of step (42) includes:

[0049] (421) Drill the bottom hole;

[0050] (422), tap 2-3 turns with motorized tapping, then remove the tool;

[0051] (423) After unloading the workpiece from the machine tool, transfer it to the fitter's workshop. After clamping and aligning the workpiece, correct the geometry of the tap and then use the corrected tap to pass through the head tap to ensure that the head tap removes 1 / 2 to 1 / 3 of the total machining amount.

[0052] (424) Use a normal tap to pass through two taps, remove the remaining machining allowance, and machine a complete thread;

[0053] (425) Use standard, unused taps for calibration to ensure that all tap processing is standardized.

[0054] A further improvement of the present invention is that:

[0055] The operation of step (5) includes:

[0056] (51) The workpiece is aligned by using the slope of the two coordinate positioning holes on the inclined surface to mill a plane on the inclined surface with an end mill.

[0057] (52) First, use solid carbide drill bit to drill holes of φ4.5mm and φ9mm respectively. Then, use a coarse reamer to coarsely ream the holes and then use a fine reamer to finely ream the holes to obtain holes of φ6mm and 10mm.

[0058] The dimensions of the reamers on the coarse reamer step reamer are φ5.8mm and φ9.8mm respectively;

[0059] The dimensions of the reamers on the precision step reamer are φ6mm and φ10mm, respectively.

[0060] A further improvement of the present invention is that:

[0061] The operation of step (6) includes:

[0062] (61) Drilling the bottom hole: Drill to a depth of 38mm with a φ20mm drill bit and to a depth of 15mm with a φ10mm drill bit to obtain two kinds of bottom holes;

[0063] (62) Rough milling and enlarging: Rough mill the bottom holes to φ25.5mm and φ15mm respectively, with a depth of 53mm;

[0064] (63) Finish milling holes: finish mill the bottom holes after rough milling to φ25.65mm and φ15.08mm respectively;

[0065] (64) Thread milling: Threads are produced by rough milling, semi-finish milling and finish milling processes;

[0066] (65) Boring: The φ280 hole is machined using rough boring, semi-finish boring, and finish boring processes. +0.05 A hole of mm;

[0067] (66) Milling annular groove: Use a T-shaped annular forming cutter to mill an annular groove with a width of 1.3mm.

[0068] A further improvement of the present invention is that:

[0069] The equipment used in step (7) is a three-coordinate deep hole gun drill, and the end face of the guide sleeve on the three-coordinate deep hole gun drill is ground and a sealing groove is set on the end face. A sealing ring is installed in the sealing groove, and the number of support frames on the drill rod of the three-coordinate deep hole gun drill is increased.

[0070] The blade body is made of YG8 series material, and the surface coating is Al2O3+TiNAl.

[0071] A further improvement of the present invention is that:

[0072] The operation of step (7) includes:

[0073] (71) Rough turn the end face and outer circle, pre-drill the center hole to keep the end face and outer circle of the workpiece coaxial;

[0074] (72) The wall thickness of the hole is measured by an ultrasonic wall thickness gauge every 180mm of drilling, and the straightness deviation of the hole is calculated based on the measured wall thickness value.

[0075] (73) If the straightness deviation is greater than the set threshold, it is determined that the axis of the deep hole is deviated. At this time, the workpiece is corrected by external force, and the chip breaker or chip breaker is ground to make the rotation center of the drill bit and the workpiece coincide again.

[0076] Preferably, the process parameters in step (7) are as follows: spindle speed is 900 r / min, feed rate is 0.8 mm / min, oil pressure is 1.5 MPa, and cutting oil is used.

[0077] Compared with the prior art, the beneficial effects of the present invention are: production and processing efficiency is increased by 20% and tooling costs are reduced by 15% after using the present invention. Moreover, the high-pressure sealing capability of the products processed using the present invention reaches 140 MPa, and the annual service footage of the near-bit gamma imaging system iSPEED reaches 10,141 m, with a total service time of 1,820 hours, meeting the well condition requirements. Attached Figure Description

[0078] Figure 1-1 This is a schematic diagram of the complex cavity structure in the near-bit short-circuit body of the logging-while-drilling downhole instrument;

[0079] Figure 1-2 yes Figure 1-1 A schematic diagram of the cross-sectional structure;

[0080] Figure 2 This is a schematic diagram of the radial high-pressure sealing hole structure in the near-bit short-circuit body of the logging-while-drilling downhole instrument;

[0081] Figure 3 This is a schematic diagram of the 60° inclined high-pressure sealing stepped hole structure in the near-bit short-circuit body of the logging-while-drilling downhole instrument;

[0082] Figure 4 This is a schematic diagram of the small-diameter blind hole thread (M6, M3) in the near-bit short-circuit body of the logging-while-drilling downhole instrument.

[0083] Figure 5 This is a schematic diagram of the ultra-slender deep hole structure in the near-bit short-circuit body of the logging-while-drilling downhole instrument;

[0084] Figure 6 This is a flowchart of the steps of the method of the present invention. Detailed Implementation

[0085] The present invention will now be described in further detail with reference to the accompanying drawings:

[0086] Currently, the materials used for the short sections used in logging while drilling are all non-magnetic stainless steel. Since all short sections must meet the requirements for the assembly, sealing, and wiring of electronic components, the structural characteristics of various short sections are roughly the same, and the processing methods are also basically the same. The general overall processing flow is as follows:

[0087] Blanking—Drilling and boring—Semi-finish turning—Finish turning (to the mating surface with the Inconel 718 alloy bushing) Figure 1-1The double arrows in the diagram represent the Inconel 718 alloy sleeve (with a allowance of 1-1.5mm) — rough milling of the cavity (with a allowance of 3-4mm) — natural static aging to relieve stress (4-5 hours) — semi-finish milling of the cavity (with a allowance of 0.2mm) — finish turning of the IT6 grade sealing surface — finish milling of the cavity — corner clearing — drilling — tapping — laser cladding welding — shot peening.

[0088] The structure of the near-bit short-circuit body of the logging-while-drilling downhole instrument made of non-magnetic stainless steel P550 is as follows: Figures 1-1 to 5 As shown in the diagram, its structure indicates that in addition to conventional machining, complex cavities, radial high-pressure sealing holes, 60° inclined high-pressure sealing stepped holes, small-diameter blind hole threads, and ultra-fine long and deep holes need to be machined on the drill bit short section body.

[0089] This invention analyzes the machining mechanism of non-magnetic stainless steel P550, a difficult-to-machine material, to understand its material composition and characteristics. It scientifically selects cutting tools and appropriate cutting parameters for each process, and solves the problem of difficult machining of high-precision and complex features through process methods, cutting methods, process parameters, tool materials and tool types. It provides process parameters and experience for the machining of non-magnetic stainless steel logging-while-drilling instrument subs.

[0090] This invention provides a method for machining a short section body made of difficult-to-machine material for logging while drilling, such as... Figure 6 As shown, the method includes:

[0091] (1) Feeding;

[0092] (2) Drilling and boring holes;

[0093] (3) Milling complex cavities;

[0094] (4) Tap small-diameter threads;

[0095] (5) Machining a 60° angled high-pressure sealing stepped hole;

[0096] (6) Machining radial high-pressure sealing holes;

[0097] (7) Machining ultra-fine long deep holes.

[0098] An embodiment of the method is as follows:

[0099] Example 1

[0100] (1) Material feeding: When feeding, keep the material perpendicular to the saw blade of the saw machine. Use a special stainless steel saw blade. Cutting parameters: saw blade linear speed: 40m / min. Keep the chip form uniform powder. Appropriately reduce the cutting parameters (spindle speed and feed rate) to keep the cutting stable and prevent the saw blade from twisting.

[0101] When processing non-magnetic stainless steel P550 using traditional processing techniques, the saw blade will be damaged quickly. This invention changes the cutting parameters to complete the material cutting smoothly.

[0102]

Example 2

[0103] (2) Drilling and boring: Drilling is carried out using a TK2135 CNC deep hole drilling and boring machine with internal chip removal, and YG8 carbide coated cutting tools are selected as the cutting tool material.

[0104] The operation of step (2) includes:

[0105] (21) After clamping the workpiece on the CW6163 ordinary lathe, align, flatten the end face, scribing, and then pre-drill the center hole; chamfer the top plate angle to 4×30°, and position the frame 150mm away from both end faces; drill an inner hole with a diameter of φ45mm, a through hole, and a length of 1614mm. Pay attention to the color and shape of the chips, with pagoda-shaped chips being the best state (pagoda-shaped chips can be ensured by controlling the cutting parameters).

[0106] (22) The inner hole is rough bored and fine bored;

[0107] The inner hole is rough bored using an integral carbide boring tool mounted on a TK2135 CNC deep hole drilling and boring machine with internal chip removal. A 0.06mm allowance is left for fine boring. Fine boring can effectively reduce built-up edge and burrs, ensuring the surface roughness of the inner hole.

[0108] Specifically, the preferred cutting parameters for rough boring are: spindle speed of 50 r / min and feed rate of 12 mm / min; the preferred cutting parameters for finish boring are: spindle speed of 42 r / min and feed rate of 10 mm / min.

[0109] The fine boring process is as follows: After rough boring the inner hole, semi-finish turning the outer circle (close to the outer circle of the drill bit sub body) is performed with the inner hole as the reference. Then, fine boring the inner hole is performed with the outer circle as the reference. Finally, fine turning the outer circle is performed with the fine bored inner hole as the reference, so that the inner hole and the outer circle are mutually referenced, and the deviation of the hole axis is controlled within 0.5mm / 1000mm.

[0110] In traditional machining processes, the inner hole is bored in one pass, followed by finish turning the outer diameter. This easily leads to misalignment between the inner and outer diameters, resulting in severe machining deformation. This invention optimizes the process flow by using the principle of mutual reference between the inner and outer diameters, with the cutting allowance decreasing sequentially. This significantly reduces stress concentration, thereby ensuring machining accuracy.

[0111]

Example 3

[0112] (3) Milling complex cavities: Complex cavities of the short section body, such as... Figure 1-1 and Figure 1-2As shown, in order to fully consider the influence of residual stress on part deformation and tool wear, and to ensure that the machining accuracy meets the design requirements, this invention...

[0113] When milling the cavity, a process of rough milling, aging, semi-finish milling, finish milling, and corner clearing is used. UG5 is used to simulate and optimize the machining path trajectory to avoid tool idle travel and tool interference.

[0114] The preferred equipment and accessories for milling complex cavities are as follows:

[0115] A, E650 five-axis linkage CNC machining center;

[0116] B. Select high-strength, heat-resistant YG8 type cemented carbide coated cutting tools; due to the non-magnetic stainless steel plastic...

[0117] Due to its good properties and severe work hardening, climb milling is recommended. Larger tool rake and clearance angles should be selected to reduce plastic deformation of the workpiece during cutting, reduce cutting heat, and mitigate work hardening.

[0118] C. Select ball end mill as the tool type.

[0119] The operation of step (3) includes:

[0120] (31), rough milling:

[0121] The cavity is rough milled using a rapid feed ball end mill, preferably a φ20 rapid feed ball end mill; 5(32), aging:

[0122] To prevent workpiece deformation due to stress release, allow it to rest naturally for 4 to 5 hours to relieve stress.

[0123] (33), Semi-finish milling:

[0124] Semi-finish milling of each semi-circular arc cavity is performed using a contour ball end mill; preferably, a φ12 contour ball end mill is used.

[0125] End mill;

[0126] 0(34), precision machining of the sealing surface:

[0127] The IT7 grade sealing surface at the mating point between the precision-machined Inconel 718 alloy sleeve is used to prevent sealing surface failure caused by large deformation.

[0128] (35), finish milling:

[0129] Use a φ6 milling cutter to finish mill each semi-circular cavity:

[0130] 5. The flatness of the bottom surface of each semi-circular arc cavity needs to reach 0.02mm. This invention uses precision milling to mill each semi-circular arc.

[0131] The method for the bottom surface of the cavity is as follows:

[0132] When finishing the bottom surface of the cavity, replace the tool holder and collet with a new one to ensure the assembly accuracy and perpendicularity of the tool. Use a dial indicator to check the alignment during inspection. During the finish milling process, ensure that only the bottom edge makes contact with the material and strictly check the runout of the cutting teeth to ensure uniform milling and to ensure the flatness requirements of the cavity are met.

[0133] In conventional machining processes, milling cavities is done in one step, that is, directly milling the plane. Due to the large amount of milling, the workpiece is very prone to deformation and cannot meet the accuracy requirements. Research has found that the accuracy of tool clamping must be guaranteed to meet the accuracy requirements. Therefore, this invention meets the accuracy requirements by "replacing the tool holder and collet with a new one, ensuring the assembly accuracy and perpendicularity of the tool, using a dial indicator for alignment during inspection, ensuring that only the bottom edge makes contact during the finish milling process, and strictly checking the runout of the tool teeth".

[0134] The preferred cutting parameters in steps (31) to (35) above are as follows:

[0135] When performing rough milling in step (31), the machine tool speed is 38 m / min, the milling feed rate is 0.3 mm / r, and the depth of cut is 1.5 mm; the rough milling leaves a machining allowance of 1 to 2 mm for the semi-finish milling.

[0136] When performing semi-finish milling in step (33), the machine tool speed is 45 m / min, the milling feed rate is 0.25 mm / r, the depth of cut is 0.15 mm, and the semi-finish milling leaves a machining allowance of 0.1 to 0.25 mm for finish milling. This allowance ensures machining accuracy and reasonably avoids tool breakage.

[0137] When performing fine milling in step (35), the machine tool speed is 60 m / min, the milling feed rate is 0.01 mm / r, and the depth of cut is 1 mm.

[0138] This invention optimizes the process flow when milling complex cavities, employing layered machining of rough milling, semi-finish milling, and finish milling. By optimizing cutting parameters and selecting the best tool structure, it improves the efficiency of rough machining and the accuracy of finish machining, while ensuring the 0.02mm flatness requirement of the cavity bottom surface.

[0139]

Example 4

[0140] (4) Tap small-diameter threads:

[0141] The six outer surfaces of the drill bit sub section are designed with large-volume cavities for assembling electronic components. After assembly, a cover plate is used for sealing. The cover plate has sealing grooves for assembling sealing rings. The cover plate is then secured using M6 or M3 small-diameter blind hole threads and fastening screws. Figure 4As shown. Therefore, the perpendicularity of the M6 ​​and M3 small-diameter blind hole threads is required to be 0.03mm, and the number of M6 and M3 threads in each cavity should be 20 to 30. This can prevent uneven force on the cover plate clamping due to thread misalignment, which in turn affects the sealing performance of the cover plate and the body. However, the existing M6 and M3 taps have poor rigidity and strength, and the cutting material has high viscosity, making the tool very easy to break, and motorized tapping of small-diameter threads is impossible.

[0142] The operation of step (4) includes:

[0143] (41) Clamp the workpiece on the milling and turning machining center and perform point hole positioning (that is, print out the cover plate drawing at a 1:1 scale and check whether the hole position matches the cover plate).

[0144] (42) Drilling the pilot hole with a motor, as detailed below:

[0145] (421) Drill a 5.2mm diameter hole for the M6 ​​bottom hole and chamfer the inner hole. M6 is an internal thread, so first drill a hole with a diameter of 5.2mm.

[0146] (422) The machine taps 2 to 3 turns, which serves as a guide. The tool is then withdrawn. To ensure perpendicularity during tapping, pay attention to the assembly accuracy of the tool holder and collet, and use a dial indicator to check.

[0147] (423) After the workpiece is unloaded from the machine tool, it is transferred to the fitter's workshop. After the workpiece is clamped and aligned, the geometry of the tap is modified (that is, the outer diameter of the tap is ground down by a grinding machine). Then, the modified tap is used to pass through the head tap (that is, the profile of the thread is machined by the modified tap. Since the outer diameter of the head tap is reduced, the cutting amount of the workpiece is also reduced). This ensures that the head tap removes 1 / 2 to 1 / 3 of the total machining amount, that is, the cutting depth of each tooth is reduced. This results in a small amount of material removed and a small cutting resistance, which effectively prevents the tool from breaking.

[0148] (424) Use a normal tap to pass through two taps, remove the remaining machining allowance, and machine a complete thread;

[0149] (425) Standardization: Use standard, unused taps for calibration to ensure that all tap processing is standardized.

[0150] The machining method for M3 is the same as that for M6, and will not be repeated here.

[0151] Traditional small-diameter internal thread tapping uses solid carbide taps, which, due to their poor rigidity and strength, are prone to breakage within the short section, requiring electrical discharge machining (EDM) for removal, and resulting in poor machining accuracy. This invention optimizes the process flow and tool structure at each step, reducing the machining allowance during roughing. This effectively reduces the cutting resistance of the tool during the first cutting operation, preventing tool breakage. The second machining operation uses a standard tap, ensuring the machining accuracy of the internal thread, significantly improving efficiency, and reducing costs.

[0152] Example 5

[0153] (5) Machining a 60° angled high-pressure sealing stepped hole:

[0154] The structure of the 60° inclined high-pressure sealing stepped hole on the short section body is as follows: Figure 3 As shown, the process flow for machining a 60° inclined high-pressure sealing step hole according to the present invention includes roughing, semi-finishing and finishing.

[0155] The operation of step (5) includes:

[0156] (51) The workpiece is aligned. The slope of the positioning holes is determined by the coordinates of two points (X1, Y1, Z1) and (X2, Y2, Z2) on the inclined surface. A flat surface is milled on the inclined surface using an end mill with the same hole diameter as the 60° high-pressure sealing hole. Preferably, when milling the flat surface, an extended tool holder, a thermal expansion joint, and a spring collet extension rod are used to prevent interference between the tool and the workpiece.

[0157] (52) First, drill holes of φ4.5mm and φ9mm respectively. Preferably, use a solid carbide drill bit to rough drill the holes of φ4.5mm and φ9mm respectively. Then, use a coarse reamer (with φ5.8mm and φ9.8mm reamers) to coarsely ream the holes, leaving a 0.1mm allowance on each side. Then, use a fine reamer (with φ6mm and φ10mm reamers) to finely ream the holes to obtain holes of φ6mm and 10mm.

[0158] This invention utilizes a stepped drill reamer to fully ensure the coaxiality requirements of the φ6mm and φ10mm sealing holes, completely meeting the high-pressure sealing assembly requirements of the sealing pin. The coarse and fine stepped drill reamers used in this invention have the same structure, both being existing reamer structures with a step and two coaxially aligned reamers, capable of simultaneously machining two holes, thus ensuring the coaxiality of the two holes. This invention designs the dimensions of the stepped drill reamer according to the required dimensions on the short section and uses carbide to make both the coarse and fine stepped drill reamers, thereby satisfying the coaxiality requirements of the two holes.

[0159] Preferably, the cutting speed for rough reaming is 40 r / min and the feed rate is 8 mm / min.

[0160] In existing processes for machining 60° angled high-pressure sealing stepped holes, the stepped holes are machined separately according to their respective process flows, which makes it difficult to ensure the coaxiality of the two holes. This invention, however, uses a stepped drill reamer for rough and fine reaming in layers, and rationally arranges the machining allowance, ensuring the high-pressure angled hole sealing assembly requirements are met.

[0161] Example 6

[0162] (6) Machining radial high-pressure sealing holes:

[0163] The structure of the radial high-pressure sealing hole on the short section body is as follows: Figure 2 As shown. The operation of step (6) includes:

[0164] (61) Drilling the pilot hole:

[0165] Two types of bottom holes were obtained by drilling to a depth of 38mm with a φ20mm drill bit and to a depth of 15mm with a φ10mm drill bit.

[0166] (62) Rough milling and enlarging: Use a φ10mm milling cutter to rough mill the bottom hole to φ25.5mm and φ15mm respectively, with a depth of 53mm. Leave a allowance of 0.5mm for finishing.

[0167] (63) Finish milling: Use standard, unworn tools to finish mill the bottom holes, finishing them to φ25.65mm and φ15.08mm respectively.

[0168] The standard diameter of the M27×1.5 threaded hole in the short section body is 25.5mm. This invention uses fine milling to make the milled bottom hole 0.15mm larger than the standard diameter. The standard diameter of the M16×1 threaded hole in the short section body is 15mm. This invention uses fine milling to make the milled bottom hole 0.08mm larger than the standard diameter. The enlarged 0.15mm and 0.08mm provide compensation for the plastic deformation of the material for the next step of thread milling. This does not affect the thread effect, but also reduces the amount of material removed during thread milling, thus making it less likely for the tool to break.

[0169] (64) Milling threads: Compile CNC programs for milling M27×1.5 and M16×1 threads. First, debug the program and perform a trial cut. Only after the thread pitch is qualified can the formal machining begin. The process flow is divided into rough milling, semi-finish milling, and finish milling. During the milling process, closely observe the tool vibration and chip removal to prevent cross-threading or tool breakage.

[0170] (65) Boring: The φ280 hole is machined using a rough boring-semi-finish boring-finish boring process. +0.05 A hole of mm;

[0171] (66) Milling annular groove: Use a T-shaped annular forming cutter to mill an annular groove with a width of 1.3mm.

[0172] In conventional processes, because the tap is too small, the tool easily gets stuck to the workpiece during insertion, leading to tool breakage. This invention improves the process flow by adding a precision milling step, making the bottom hole 0.15mm and 0.08mm larger than the standard diameter, respectively. By rationally arranging the machining allowance, the amount of material removed in the thread milling process is reduced, preventing tool breakage and ensuring the machining accuracy of the radial high-pressure sealing hole. The efficiency during the trial production stage is improved by 10%.

[0173] Example 7

[0174] (7) Machining ultra-fine long and deep holes:

[0175] The structure of the ultra-fine long deep hole on the short section body is as follows Figure 5 As shown, ultra-fine long deep holes are small-diameter inclined holes (diameter 5mm, depth 225~1000mm) with a depth-to-diameter ratio ≥25. Their machining and positioning are difficult, and the hole diameter is prone to deviation. Due to the high toughness of the material and severe work hardening, chip breaking and chip removal are difficult during the machining of ultra-fine long deep holes. The drill bit is prone to jamming, which causes the "V"-shaped wire groove of the drilling instrument to deviate or the sealing hole to be damaged, resulting in the scrapping of parts.

[0176] The preferred equipment and tools for processing ultra-fine, long, deep holes according to this invention are as follows:

[0177] A. The equipment selected is a three-coordinate deep hole gun drill.

[0178] B. The tool body material is selected from the YG8 series, with a surface coating of Al2O3+TiNAl. The rake angle of the tool is appropriately increased to facilitate chip breaking.

[0179] C. Process Equipment: The end face of the guide sleeve is ground to ensure the flatness of the contact with the workpiece, and an end face sealing groove is designed. During processing, the sealing ring is assembled (i.e., the end face of the guide sleeve on the existing three-coordinate deep hole gun drill is ground and a sealing groove is opened, and a sealing ring is installed in the sealing groove), which ensures the hydraulic oil sealing performance and facilitates chip breaking; the fit clearance between the guide sleeve and the drill bit is increased from 0.02mm to 0.01mm, and the guide sleeve material is made of hard alloy with high hardness and good wear resistance; the number of support frames on the drill rod is improved from 2 to 3 to improve the stability of the drill rod.

[0180] The operation of step (7) includes:

[0181] (71) Rough turn the end face and outer circle, pre-drill the center hole to keep the end face and outer circle coaxial and ensure drilling accuracy.

[0182] (72) Use an ultrasonic wall thickness gauge to check the wall thickness of the hole every 180mm of drilling, and calculate the straightness deviation of the hole based on the measured wall thickness value. Observe the wear state of the tool and the vibration of the machine tool in real time. If any abnormality is found, stop the machine immediately for inspection.

[0183] (73) If the straightness deviation is greater than the set threshold, it is determined that the axis of the deep hole is deviated. At this time, a certain external force is applied to the workpiece to correct the deviation, and the chip groove or chip breaking table is ground to make the rotation center of the drill bit and the workpiece coincide again.

[0184] The preferred process parameters in the above steps are: spindle speed: 900 r / min, feed rate: 0.8 mm / min, oil pressure: 1.5 MPa, and cutting oil used.

[0185] This invention improves the material of the cutting tool and the guide sleeve, thereby increasing the clearance between the guide sleeve and the drill bit; it uses an ultrasonic wall thickness gauge to measure the wall thickness of the hole every 180mm of machining, and applies external force to correct any deviation, ensuring the accuracy of deep hole machining; it increases the number of support frames on the drill rod from 2 to 3, improving the stability of the drill rod; and it optimizes the spindle speed and feed rate to facilitate chip breaking and chip removal.

[0186] Based on material properties and workpiece structural characteristics, this invention designs a reasonable process scheme and equipment. For different machining processes, it optimizes tool path trajectories and scientifically selects the best tools and process parameters, achieving an optimal balance between personnel, machines, materials, methods, and environment. This has enabled the machining of φ172mm and φ190mm engineering parameter short sections, a φ172mm near-bit short section, and a φ180mm intelligent control suspension body. High-pressure sealing reached 140MPa. The iSPEED near-bit gamma imaging system achieved an annual service footage of 10,141m, breaking the 10,000-meter mark for the first time, with a total service time of 1,820 hours. The tools' field application meets well condition requirements. This invention solves the problem of efficient machining of complex, irregularly shaped, curved surface structures made of difficult-to-machine materials for downhole instruments, and masters methods for deformation control in ultra-deep hole machining. The production cycle is shortened by an average of approximately 20%, and machining costs are reduced by an average of approximately 15%, while achieving good machining accuracy and 100% compliance with design specifications.

[0187] Based on a thorough analysis of the machining performance of non-magnetic materials and the structure of parts, this invention achieves the machining of high-precision complex structural parts made of difficult-to-machine materials by selecting high-efficiency machining equipment and cutting tools, designing special tooling, and optimizing process flow and process parameters. This meets the assembly requirements of high-pressure sealed electronic components. This invention can achieve high material removal efficiency and effectively solve the machining of high-precision complex structural parts made of high-hardness, high-viscosity non-magnetic stainless steel. Therefore, this invention has broad application prospects.

[0188] The above technical solution is only one embodiment of the present invention. For those skilled in the art, based on the principles disclosed in the present invention, it is easy to make various types of improvements or modifications, and not limited to the technical solutions described in the specific embodiments of the present invention. Therefore, the foregoing description is only a preferred option and is not restrictive.

Claims

1. A method for machining a short section body made of difficult-to-machine material for logging while drilling, characterized in that: The method includes: Material feeding; Drilling and boring: After clamping the workpiece on a conventional lathe, drill the inner hole; rough boring and fine boring of the inner hole: rough boring of the inner hole using an integral carbide boring tool; semi-finish turning of the outer circle with the inner hole as the reference, then fine boring of the inner hole with the outer circle as the reference, and finally fine turning of the outer circle with the finely bored inner hole as the reference. Milling complex cavities: rough milling, aging, semi-finish milling of each semi-circular arc cavity using a contour ball end mill, finish turning of the sealing surface, and finish milling; For small-diameter thread tapping: Clamp the workpiece on a milling and turning machining center and perform spot hole positioning; drill the pilot hole; tap 2-3 turns with a motorized tapping machine, then retract the tool; after unloading the workpiece from the machine tool, transfer it to the fitter's workshop, clamp and align the workpiece, correct the geometry of the tap, and then use the corrected tap through the first tap to ensure that the first tap removes 1 / 2 to 1 / 3 of the total machining allowance; use a normal tap through the second tap to remove the remaining machining allowance and machine a complete thread; use a standard, unused tap for calibration to ensure that all tap machining is standardized; Machining a 60° inclined high-pressure sealing step hole: Align the workpiece, locate the inclination of the hole by two coordinates on the inclined surface, and mill a plane on the inclined surface with an end mill; first drill the hole, then use a rough reamer to rough ream the hole, and then use a fine reamer to fine ream the hole; Machining radial high-pressure sealing holes: drilling pilot holes, rough milling and reaming, finish milling, thread milling, boring, and milling annular grooves; Machining ultra-thin, long, and deep holes: Rough turn the end face and outer diameter, pre-drill the center hole to keep the workpiece end face and outer diameter coaxial; use an ultrasonic wall thickness gauge to detect the hole wall thickness, and calculate the straightness deviation of the hole based on the measured wall thickness value; if the straightness deviation is greater than the set threshold, it is determined that the axis of the deep hole is deviated. At this time, external force is applied to correct the deviation of the workpiece, and the chip breaker or chip breaker is ground to make the rotation center of the drill bit and the workpiece coincide again.

2. The method for processing the short section body of difficult-to-machine material for logging while drilling according to claim 1, characterized in that: The material feeding operation includes: Keep the material perpendicular to the saw blade, and use a stainless steel saw blade; The cutting parameters are 40 m / min.

3. The method for processing the short section body of difficult-to-machine material for logging while drilling according to claim 1, characterized in that: The cutting parameters for rough boring are as follows: spindle speed is 50 r / min, and feed rate is 12 mm / min; The cutting parameters for precision boring are as follows: spindle speed is 42 r / min, and feed rate is 10 mm / min.

4. The method for processing the short section body of difficult-to-machine material for logging while drilling according to claim 1, characterized in that: The rough milling operation includes: rough milling the cavity using a fast feed ball end mill; The aging process includes: natural static aging for 4-5 hours to relieve stress; The operation of precision machining the sealing surface includes: precision machining the IT7 grade sealing surface at the mating point with the Inconel 718 alloy sleeve; The precision milling operation includes: using a φ6 milling cutter to precision mill each semi-circular arc cavity.

5. The method for processing the short section body of difficult-to-machine material for logging while drilling according to claim 4, characterized in that: The precision milling operation includes: After replacing the tool holder and collet, perform finish milling. During finish milling, ensure that only the bottom edge makes contact with the material and check the runout of the cutting teeth.

6. The method for processing the short section body of difficult-to-machine material for logging while drilling according to claim 1, characterized in that: During rough milling, the machine tool speed is 38 m / min, the milling feed rate is 0.3 mm / r, and the depth of cut is 1.5 mm; leave a machining allowance of 1 to 2 mm for rough milling and semi-finish milling. During semi-finish milling, the machine tool speed is 45 m / min, the milling feed rate is 0.25 mm / r, the depth of cut is 0.15 mm, and the machining allowance for finish milling is 0.1 to 0.25 mm. During finish milling, the machine tool speed is 60 m / min, the milling feed rate is 0.01 mm / r, and the depth of cut is 1 mm.

7. The method for processing the short section body of difficult-to-machine material for logging while drilling according to claim 1, characterized in that: The process of drilling holes, coarsely reaming the holes with a step reamer, and then finely reaming the holes with a step reamer includes: first drilling holes of φ4.5mm and φ9mm respectively with a solid carbide drill bit, then coarsely reaming the holes with a step reamer, and then finely reaming the holes with a step reamer to obtain holes of φ6mm and 10mm. The dimensions of the coarse-reaming stepped reamers are φ5.8mm and φ9.8mm respectively; The dimensions of the precision-reamed stepped reamers are φ6mm and φ10mm, respectively.

8. The method for processing the short section body of difficult-to-machine material for logging while drilling according to claim 1, characterized in that: The drilling operation includes: drilling to a depth of 38mm with a φ20mm drill bit and drilling to a depth of 15mm with a φ10mm drill bit to obtain two types of bottom holes; The rough milling and enlarging operation includes: rough milling the bottom hole to φ25.5mm and φ15mm respectively, with a depth of 53mm; The operation of finish milling the holes includes: finish milling the rough-milled bottom holes to φ25.65mm and φ15.08mm respectively; The thread milling operation includes: machining threads using rough milling, semi-finish milling, and finish milling processes; The boring operation includes: machining a φ280 hole using rough boring, semi-finish boring, and finish boring processes. +0.05 A hole of mm; The operation of milling the annular groove includes: using a T-shaped annular forming cutter to mill an annular groove with a width of 1.3 mm.

9. The method for processing the short section body of difficult-to-machine material for logging while drilling according to claim 1, characterized in that: The equipment used for processing ultra-fine long deep holes is a three-coordinate deep hole gun drill. The end face of the guide sleeve on the three-coordinate deep hole gun drill is ground and a sealing groove is set on the end face. A sealing ring is installed in the sealing groove. At the same time, the number of support frames on the drill rod of the three-coordinate deep hole gun drill is increased. The blade body is made of YG8 series material, and the surface coating is Al2O3+TiNAl.

10. The method for processing the short section body of difficult-to-machine material for logging while drilling according to claim 1, characterized in that: The wall thickness of the hole is measured using an ultrasonic wall thickness gauge every 180mm of drilling.

11. The method for processing the short section body of difficult-to-machine material for logging while drilling according to claim 1, characterized in that: The process parameters for machining ultra-fine long and deep holes are as follows: spindle speed is 900 r / min, feed rate is 0.8 mm / min, oil pressure is 1.5 MPa, and cutting oil is used.

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