A valve body machining process and machining program design method

Abstract

This invention discloses a valve body machining process and machining program design method. The valve body machining process includes: aligning the tooling on a machining center and clamping the valve body blank; semi-finishing the upper flange end face; semi-finishing and finishing the upper inner hole to form the upper end face stop hole; semi-finishing and finishing the end of the middle inner hole near the upper inner hole to form the threaded stop hole; semi-finishing and finishing the middle inner hole portion at the bottom of the threaded stop hole to form the threaded bottom hole; machining the threaded bottom hole to form the middle threaded hole; machining the flange threaded hole on the upper flange end face; inspection; rotating the tooling 180° and machining the bevel and bottom inner hole. The valve body machining can be completed by clamping the valve body once on the machining center and executing the corresponding machining process, enabling efficient and stable CNC machining of the valve body and achieving precise machining of the safety valve body.

Description

Technical Field

[0001] This invention relates to the field of machining technology, specifically to a valve body machining process and machining program design method. Background Technology

[0002] In the field of high-temperature and high-pressure valves, safety valves, as protective valves for equipment under internal pressure, are installed on boilers, pressure vessels, pressure pipelines, and other equipment, and are extremely important automatic protection devices. As global thermal power generating units develop towards ultra-high pressure, supercritical, and ultra-supercritical technologies, the requirements for the safety and economy of these units are becoming increasingly stringent. TSG 11-2020, the "Technical Regulations for Boiler Safety," stipulates that each boiler should be equipped with at least one or two safety valves (including boiler drum and superheater safety valves); safety valves in in-use boilers should be calibrated at least once a year, generally under boiler operating conditions; safety valves are not allowed to be disconnected during boiler operation, nor are their set pressures allowed to be increased or rendered ineffective. Therefore, as a crucial safety accessory, the performance of safety valves directly affects the safe operation of boilers and pressure vessels.

[0003] To ensure the stable performance of each safety valve and that acceptance monitoring meets standard requirements, quality control is necessary through precise manufacturing processes and rigorous process control. The valve body is a core component affecting the assembly and calibration quality of the safety valve. In production practice, if the valve body machining accuracy can meet design precision requirements while also achieving batch data consistency, a higher first-pass yield can be ensured, thereby achieving precise, stable, and controllable calibration indicators for the safety valve.

[0004] The valve body has a polyhedral structure, requiring high precision in dimensional accuracy at all levels, coaxiality or perpendicularity between holes and faces, and geometric tolerances between faces. The traditional machining process for the valve body is as follows: rough machining (lathe operator) – dimensional inspection (inspector) – finish machining one end (lathe operator) – turning and straightening, finish machining the other end (dimension consistency cannot be controlled, lathe operator) – finish machining inspection (inspector) – marking of holes (marking operator) – drilling and tapping (fitter) – deburring (fitter) – warehousing (requires separate dimensional records, warehouse manager). This involves four processes, three transfers, and multiple inspection stops. Machining is completed only after passing inspection, and dimensional records are required for warehousing, resulting in a lack of interchangeability. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a valve body machining process and machining program design method, which can perform valve body CNC machining efficiently and stably, and realize the precise machining of safety valve body.

[0006] To address the aforementioned technical problems, this invention provides a valve body machining process that utilizes a machining center for one-stop machining, comprising the following steps:

[0007] Step 1: Align the tooling on the machining center and clamp the valve body blank;

[0008] Step 2: Semi-finish machining of the upper flange end face;

[0009] Step 3: Perform semi-finishing and finishing on the upper inner hole to form the upper end face stop hole;

[0010] Step 4: Perform semi-finishing and finishing on the end of the middle inner hole near the upper inner hole to form the threaded stop hole;

[0011] Step 5: Perform semi-finishing and finishing on the middle inner hole at the bottom of the threaded stop hole to form the threaded bottom hole; then machine the threaded bottom hole to form the middle threaded hole.

[0012] Step 6: Machining the flange threaded holes on the upper flange end face;

[0013] Step 7: Check whether the dimensional tolerances, positional tolerances, and surface roughness of the upper flange end face, upper end face stop hole, threaded stop hole, middle threaded hole, and flange threaded hole meet the requirements.

[0014] Step 8: Rotate the fixture 180° and machine the bevel and bottom inner hole.

[0015] In the above valve body processing technology, the valve body only needs to be clamped on the machining center once, and then the corresponding processing technology can be executed to complete the processing of the valve body and sealing pair assembly structure. There is no need to transfer the process, reassemble, or stop the process for inspection. The product quality is stable, the dimensions are consistent, and the average processing time is short.

[0016] Furthermore, in step five, the machining diameter of the threaded bottom hole is taken from (m, n), where m is the median value of the tolerance zone of the minor diameter of the internal thread, and n is the maximum limit value of the minor diameter of the internal thread.

[0017] Because threaded holes are deep holes, even with a vibration-damping and extended tool holder, the bottom and entry ends of the thread will still taper due to the vibration cutter. Excessive taper will lead to thread defects. Therefore, by using the upper half of the tolerance zone for the diameter of the threaded hole, i.e., keeping the diameter of the threaded hole at a relatively large level, the total radial cutting depth is reduced, thereby reducing the total amount of material removed during thread machining. This decreases the contact between the tool and the workpiece, mitigating the impact of vibration.

[0018] Preferably, the machining diameter of the threaded bottom hole is taken as the maximum value within the acceptable range.

[0019] Furthermore, in step five, the threaded bottom hole is machined using a layered cutting method.

[0020] Due to the influence of the vibrating cutter, completing the entire thread machining in one go, especially for coarse threads where the smaller bottom hole and greater thread depth result in greater torque resistance, can lead to a defective size where the bottom is smaller than the end. By using a layered cutting method, multiple cutters can reduce cutting deformation and surface stress, compensating for the effect of the vibrating cutter.

[0021] Furthermore, in step five, the threaded bottom hole is machined using a three-layer cutting method, specifically including the following steps:

[0022] Step a1: Machin the first layer at the first feed rate, first depth of cut, and first spindle speed;

[0023] Step a2: Machin the second layer at the second feed rate, the second depth of feed, and the first spindle speed;

[0024] Step a3: Machin the third layer at the second feed rate, the third depth of cut, and the second spindle speed;

[0025] Among them, the first feed rate is greater than the second feed rate, the first depth of feed is greater than the second depth of feed, the third depth of feed is greater than the third depth of feed, and the first spindle speed is less than the second spindle speed.

[0026] Feed rate is the feed amount. By setting the feed rate, depth of cut, and spindle speed appropriately during three-layer machining, the taper caused by the thread bottom and entry end can be reduced.

[0027] Furthermore, the first depth of cut is 52.5% to 57.5% of the total radial depth of cut; the second depth of cut is 34.5% to 39.5% of the total radial depth of cut; and the third depth of cut is 5.5% to 10.5% of the total radial depth of cut. The depth of cut is gradually reduced in layers to reduce the generation of taper.

[0028] Furthermore, the first feed rate is 900 mm / min, the second feed rate is 700 mm / min; the first depth of cut is 55% of the total radial depth of cut; the second depth of cut is 37% of the total radial depth of cut; the third depth of cut is 8% of the total radial depth of cut; the first spindle speed is 700 r / min, and the second spindle speed is 1000 r / min.

[0029] Furthermore, in step five, the threaded bottom hole is machined using an extended, vibration-damping tool holder with a tapered shank structure. The tool holder must not only be strong but also meet spatial requirements. Selecting a tool holder with a tapered shank structure better suits the machining environment of deep threaded holes, ensuring stability, reducing the risk of vibration, and guaranteeing sufficient space for thread cutting.

[0030] Furthermore, in step five, a thread milling cutter disc with multiple single-edged adjustable inserts is used to machine the threaded bottom hole.

[0031] Furthermore, before step one, the process also includes: step c: rough machining the upper flange end face, upper inner hole, middle inner hole and bottom inner hole of the valve body.

[0032] The present invention discloses a machining program design method, comprising the following steps:

[0033] Step b1: By analyzing the existing processing technology of the valve body, a one-stop processing solution using a CNC machining center is determined;

[0034] Step b2: Based on the structural characteristics of the valve body, determine the machining reference surface and establish a blank process design model;

[0035] Step b3: Design the clamping fixture based on the machining datum plane and the CNC machining center;

[0036] Step b4: Based on the CNC machining center, clamping fixture, and blank process design model, design the machining program for the valve body, wherein the machining program can realize the above-mentioned valve body machining process; preferably, the machining program includes tool selection and machining parameters;

[0037] Step b5: Verify the machining process by simulating it using simulation technology, and optimize the machining program and blank process design model;

[0038] Step b6: Import the machining program into the machining center and verify it by actually machining the valve body to further optimize the machining program.

[0039] Furthermore, after step b6, the following step is also included: Step b7: The final optimized result of the machining program is replaced and imported into the machining center for use during machining.

[0040] Furthermore, after step b7, the following step b8 is also included: Establishing a correspondence between the valve body and the corresponding machining program in the control system of the machining center, so that after the operator inputs the drawing number of the valve body, the corresponding machining program is automatically matched.

[0041] In summary, the above-mentioned valve body processing technology and processing procedure design method have the following beneficial effects:

[0042] 1. It solves the shortcomings of traditional valve body processing technology, such as unstable quality and low first-pass yield; moreover, it reduces the difficulty of process quality control and can achieve batch consistency of product processing.

[0043] 2. Reduces machining taper caused by the overhang of the threading tool holder, thus more stably and effectively ensuring the quality of form and position tolerances. Attached Figure Description

[0044] In the attached diagram:

[0045] Figure 1 This is a schematic diagram of the valve body after clamping, based on the valve body processing technology of the present invention.

[0046] Figure 2 This is a schematic diagram of the valve body after rough machining according to the valve body processing technology of the present invention.

[0047] Figure 3 This is a schematic diagram of the valve body after machining and forming according to the valve body processing technology of the present invention.

[0048] In the figure, 1 is the upper flange end face; 11 is the flange threaded hole; 2 is the upper inner hole; 21 is the upper end face stop hole; 3 is the middle inner hole; 31 is the threaded stop hole; 32 is the middle threaded hole; 4 is the bottom inner hole; and 5 is the bevel. Detailed Implementation

[0049] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions of the embodiments are for the purpose of helping to understand the present invention, but do not constitute a limitation thereof.

[0050] Example 1

[0051] The present invention discloses a valve body processing technology, which utilizes a machining center for one-stop processing and includes the following steps one through nine.

[0052] Step c: Rough machining of the upper flange end face 1, upper inner hole 2, middle inner hole 3, and bottom inner hole 4. The rough machining of the valve body is completed outside the machining center. The structural dimensions after rough machining are as follows: Figure 2 As shown, taking the example of the upper inner hole 2 with a diameter D1 of φ135 and the middle inner hole 3 with a diameter D2 of φ80, the diameter of the bottom inner hole 4 is smaller than that of the middle inner hole 3. Additionally, Figure 2 It also refers to the installation posture of the valve body.

[0053] Machining using general-purpose milling cutters Figure 2 The D1 hole is machined, and the D2 hole is machined using an extended tool holder and a square-shoulder end mill, ensuring that both holes are machined in one clamping operation, thus easily meeting the coaxiality requirements.

[0054] Step 1: Align the tooling on the machining center and clamp the valve body blank. The clamped position is as follows: Figure 1 As shown, the valve body side flange face is... Figure 1 The machining reference surface is used as the clamping surface, and a horizontal machining center is adopted.

[0055] Step 2: Semi-finish machining of the upper flange end face 1.

[0056] Step 3: Perform semi-finishing and finishing on the upper inner hole 2 to form the upper end face stop hole 21. (Example:) Figure 3As shown, the upper end face stop hole 21 is a stepped hole. After final machining, the D3 dimension is φ160H9 and the D4 dimension is φ140H9. In the specific machining process, a square shoulder end mill is first used to semi-finish mill the bottom of the upper inner hole 2 to φ159 and the bottom to φ139; then a straight shank end mill is used to finish mill to φ140H9 and φ160H9 to meet the surface roughness and accuracy requirements.

[0057] Step 4: Perform semi-finishing and finishing on the end of the middle inner hole 3 near the upper inner hole 2 to form the threaded stop hole 31.

[0058] like Figure 3 As shown, the central inner hole 3 is divided into two sections: the top is a smooth hole, i.e., the threaded stop hole 31, and the bottom is the central threaded hole 32. After the threaded stop hole 31 is finally machined, the D5 dimension is φ90H9. The stop hole φ90 at the upper end of the threaded hole is milled in multiple steps of "roughing + finishing" using an extended vibration-damping tool holder and a square shoulder milling cutter head.

[0059] Step 5: Perform semi-finishing and finishing on the middle inner hole 3 at the bottom of the threaded stop hole 31 to form the threaded bottom hole; then process the threaded bottom hole to form the middle threaded hole 32.

[0060] After the final machining of the central threaded hole 32, the D6 dimension is M85×2-6H. The threaded hole is milled to the size in two steps, "semi-finish + finish", using an extended vibration-damping tool holder and a square shoulder milling cutter head. Then the thread is machined. The bottom of the central threaded hole 32 is a relief groove hole.

[0061] Optionally, the machining diameter of the threaded pilot hole can be ranged from (m, n), where m is the median value of the minor diameter tolerance zone of the internal thread, and n is the maximum limit value of the minor diameter of the internal thread, reducing the influence of the vibrating cutter. The optimal machining diameter of the threaded pilot hole is the maximum value within the acceptable range, which can be n.

[0062] Optionally, the threaded bottom hole can be machined using a layered cutting method.

[0063] Optionally, the threaded pilot hole can be machined using a three-layer cutting method, specifically including the following steps:

[0064] Step a1: Machin the first layer at the first feed rate, first depth of cut, and first spindle speed;

[0065] Step a2: Machin the second layer at the second feed rate, the second depth of feed, and the first spindle speed;

[0066] Step a3: Machin the third layer at the second feed rate, the third depth of cut, and the second spindle speed;

[0067] Among them, the first feed rate is greater than the second feed rate, the first depth of feed is greater than the second depth of feed, the third depth of feed is greater than the third depth of feed, and the first spindle speed is less than the second spindle speed.

[0068] By setting the feed rate, depth of cut, and spindle speed appropriately during three-layer machining, the taper caused by the vibrating cutter at the bottom and entry ends of the thread can be reduced.

[0069] Optionally, the first depth of cut is 52.5% to 57.5% of the total radial depth of cut; the second depth of cut is 34.5% to 39.5% of the total radial depth of cut; and the third depth of cut is 5.5% to 10.5% of the total radial depth of cut. The depth of cut is gradually reduced in layers to reduce the generation of taper.

[0070] Optionally, the first feed rate is 900 mm / min, the second feed rate is 700 mm / min; the first depth of cut is 55% of the total radial depth of cut; the second depth of cut is 37% of the total radial depth of cut; the third depth of cut is 8% of the total radial depth of cut; the first spindle speed is 700 r / min, and the second spindle speed is 1000 r / min.

[0071] The thread machining of this example product uses a gradient feed method. The minor diameter of the M85×2 internal thread is 82.835mm, therefore the total radial depth of cut is 2.165mm. Specifically, during the first pass: feed rate F900mm / min, depth of cut 1.2mm, spindle speed 700r / min; during the second pass: feed rate F700mm / min, depth of cut 0.8mm, spindle speed 700r / min; during the third pass: feed rate F700mm / min, depth of cut 0.165mm, spindle speed 1000r / min. The dimensional requirements are met after three passes. During the third pass, the increased spindle speed and smaller feed depth result in a high-quality thread surface and high dimensional accuracy.

[0072] Optionally, for machining the threaded bottom hole, an extended, vibration-damping tool holder with a tapered shank structure can be used, such as... Figure 1 As shown. The tool holder not only needs strength but also needs to meet the space requirements. The selection of a tool holder with a tapered shank structure is more suitable for the machining environment of deep threaded holes, which can ensure stability, reduce the risk of vibration, and ensure space for thread cutting.

[0073] Optionally, a thread milling cutter disc with multiple single-edged adjustable inserts can be used to machine the threaded bottom hole.

[0074] Step 6: Machining the flange threaded hole 11 on the upper flange end face 1. Machining the pilot hole first, then machining the thread.

[0075] Step 7: Check whether the dimensional tolerances, positional accuracy, and surface roughness of the upper flange end face 1, upper end face stop hole 21, threaded stop hole 31, central threaded hole 32, and flange threaded hole 11 meet the requirements. The final machined valve body structure dimensions are as follows: Figure 3 As shown.

[0076] Step 8: Rotate the fixture 180° and machine the bevel 5 and the bottom inner hole 4. Rotate the worktable 180° to align the bottom inner hole 4 with the tool, which makes it easy to machine the various parts of the bevel 5 to size, as well as the bottom inner hole 4. The bottom inner hole 4 is also semi-finished and then finished.

[0077] Furthermore, the processing quality of roughing, semi-finishing and finishing, as described in this invention, increases sequentially, and the corresponding processing methods include milling, drilling and milling, etc.

[0078] The present invention provides a machining program design method, comprising the following steps b1 to b8.

[0079] Step b1: By analyzing the existing machining process of the valve body, a one-stop machining solution using a CNC machining center is determined. After analyzing the process of the valve body series parts, suitable equipment is selected and the overall machining scheme is determined; the shortcomings of the traditional multi-process machining method are analyzed, the process design is optimized, and a new process scheme is determined.

[0080] Step b2: Based on the structural characteristics of the valve body, determine the machining reference surface, such as... Figure 2 As shown, a blank process design model is established. Based on equipment capabilities and product characteristics, the machining reference surface is determined, and a blank process design model is created.

[0081] Step b3: Design the clamping fixture based on the machining datum plane and the CNC machining center.

[0082] Optionally, after analyzing the characteristics of the machining datum surface, it can be determined that the machining datum surface has common characteristics in the series of products, and tooling design can be carried out to achieve convenient product clamping, guaranteed machining safety, and simple and easy positioning.

[0083] Step b4: Based on the CNC machining center, clamping fixture, and blank process design model, design the machining program for the valve body, wherein the machining program can realize the above-mentioned valve body machining process; preferably, the machining program includes tool selection and machining parameters.

[0084] Step b5: Verify the machining process by simulating it using simulation technology, and optimize the machining program and blank process design model.

[0085] The machining effect of the complete simulation program is analyzed, and process parameters and toolpaths are optimized, including blank allowance, tool type selection, machining speed and feed, and toolpath selection. Then, the program and blank drawing are continuously revised to form a more accurate program and blank drawing.

[0086] The revised program was repeatedly simulated to determine the rationality of each process parameter and to improve the CNC program for valve body machining.

[0087] Step b6: Import the machining program into the machining center and verify it by actually machining the valve body to further optimize the machining program.

[0088] Select a typical valve body for prototype testing. If problems such as machining position interference, complex toolpath, or tool damage occur, conduct process diagnosis at any time, including clamping and calibration convenience testing, tooling stability testing, process optimization, tool specification and parameter adjustment, program optimization, etc., until the prototype product sample is stable and the first-pass yield rate of the test batch reaches 100%, then the feasibility of one-stop machining of the prototype can be determined.

[0089] For typical parts, detailed optimizations are performed, such as rotational speed, feed rate, and tool compensation value. Combined with empirical database algorithms, process parameters are automatically optimized. At the same time, the estimated life cycle of various tools (based on conservative values) is analyzed based on experimental data to form a tool compensation value table for the corresponding product.

[0090] Step b7: Replace the final optimized result of the machining program with the import result into the machining center for use during machining.

[0091] After the typical product processing procedure is solidified and stabilized, the relevant characteristics of the valve body series are summarized and analyzed in batches to identify consistent and different items. The program is then analyzed and designed in a modular manner for easy reference.

[0092] Step b8: Establish the correspondence between the valve body and the corresponding machining program in the control system of the machining center, so that after the operator inputs the drawing number of the valve body, the corresponding machining program will be automatically matched.

[0093] After forming a modular program, the program is controlled and designed. The operator does not need to program separately. After inputting the corresponding product drawing number, the corresponding program will be automatically selected. After measuring or observing whether the key tools are damaged, the operator can choose whether to input the tool compensation value. After a simple path simulation, the program can be started to complete the corresponding valve body machining.

[0094] 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 its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. A valve body processing technology, characterized in that, The machining of safety valve bodies is performed using a machining center in a single operation, including the following steps: Step 1: Align the tooling on the machining center and clamp the valve body blank, using the valve body side flange face as the clamping surface; Step 2: Semi-finish machining of the upper flange end face (1); Step 3: Perform semi-finishing and finishing on the upper inner hole (2) to form the upper end face stop hole (21). Step 4: Perform semi-finishing and finishing on the end of the middle inner hole (3) near the upper inner hole (2) to form the threaded stop hole (31). Step 5: Perform semi-finishing and finishing on the middle inner hole (3) at the bottom of the thread stop hole (31) to form the thread bottom hole; then process the thread bottom hole to form the middle thread hole (32). Step 6: Machining the flange threaded hole (11) on the upper flange end face (1); Step 7: Check whether the dimensional tolerances, positional tolerances and roughness of the upper flange end face (1), upper end face stop hole (21), threaded stop hole (31), middle threaded hole (32) and flange threaded hole (11) meet the requirements; Step 8: Rotate the fixture 180° and machine the bevel (5) and the bottom inner hole (4); In step five, the machining diameter of the threaded bottom hole is taken from (m, n), where m is the median value of the tolerance zone of the minor diameter of the internal thread, and n is the maximum limit value of the minor diameter of the internal thread. In step five, the threaded bottom hole is machined using a layered cutting method; When there are three layers, the layered cutting method includes the following steps: Step a1: Machin the first layer at the first feed rate, first depth of cut, and first spindle speed; Step a2: Machin the second layer at the second feed rate, the second depth of feed, and the first spindle speed; Step a3: Machin the third layer at the second feed rate, the third depth of cut, and the second spindle speed; Among them, the first feed rate is greater than the second feed rate, the first depth of cut is greater than the second depth of cut is greater than the third depth of cut, and the first spindle speed is less than the second spindle speed.

2. The valve body processing technology according to claim 1, characterized in that, The first depth of cut is 52.5% to 57.5% of the total radial depth of cut; the second depth of cut is 34.5% to 39.5% of the total radial depth of cut; and the third depth of cut is 5.5% to 10.5% of the total radial depth of cut.

3. The valve body processing technology according to claim 1, characterized in that, In step five, the threaded pilot hole is machined: ① An extended, shock-absorbing tool holder with a tapered shank structure; ② It adopts a thread milling cutter head, which has multiple single-edged adjustable inserts.

4. The valve body processing technology according to claim 1, characterized in that, The steps preceding step one also include: Step c: Roughly machine the upper flange end face (1), upper inner hole (2), middle inner hole (3) and bottom inner hole (4) of the valve body.

5. A machining program design method, characterized in that, Includes the following steps: Step b1: By analyzing the existing processing technology of the valve body, a one-stop processing solution using a CNC machining center is determined; Step b2: Based on the structural characteristics of the valve body, determine the machining reference surface and establish a blank process design model; Step b3: Design the clamping fixture based on the machining datum plane and the CNC machining center; Step b4: Based on the CNC machining center, clamping fixture and blank process design model, design the machining program for the valve body, wherein the machining program can realize the valve body machining process described in any one of claims 1-4 above; Step b5: Verify the machining process by simulating it using simulation technology, and optimize the machining program and blank process design model; Step b6: Import the machining program into the machining center and verify it by actually machining the valve body to further optimize the machining program.

6. The machining program design method according to claim 5, characterized in that, Step b6 is followed by: Step b7: Replace and import the final optimized result of the machining program into the machining center.

7. The machining program design method according to claim 6, characterized in that, Step b7 is followed by: Step b8: Establish the correspondence between the valve body and the corresponding machining program in the control system of the machining center, so that after the operator inputs the drawing number of the valve body, the corresponding machining program will be automatically matched.

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