A method for milling a keyway and a convex bump of a liquid rocket engine valve housing

Abstract

A kind of milling method of liquid rocket engine valve shell keyway and convex, adopt four-axis machining center machining process, and design machining keyway straight handle inverted cone end mill, machining convex milling cutter, determine the reasonable cutting parameters of keyway machining, while the keyway milling processing, while ensuring the size tolerance, shape tolerance and roughness requirement of keyway.Finally realize the processing of two side holes, one inclined side hole, keyway and convex, threaded hole, inner cavity, scribe, deburring, which needs thirteen processes to complete, now a tooling twice clamping high quality, high efficiency processing.

Description

Technical Field

[0001] This invention relates to a milling method for the keyway and convex hull of a valve housing in a liquid rocket engine, belonging to the field of liquid rocket engine manufacturing. Background Technology

[0002] The valve housing is a key component in the propellant storage and supply system of a liquid rocket engine. Assembled with related parts to form a valve, it isolates the propellant storage system from downstream valves before ignition. Upon ignition, it ensures the stable release of propellant downstream. Its quality directly impacts the success of rocket ignition and launch. With the increasing demands for high-quality development and the continuous advancement of research into new technologies and processes, the requirements for component quality stability and processing efficiency control are also growing. This necessitates a shift from manual processing using conventional equipment to high-quality, high-efficiency CNC integrated machining of valve housings.

[0003] The existing processing methods have four main problems:

[0004] 1. The thirteen processes are carried out separately, and the turnaround and waiting time for each batch of products is about 16 hours, which is relatively long;

[0005] 2. The clamping and alignment of each product in the thirteen processes takes about 20 minutes in total, resulting in low work efficiency and low equipment utilization.

[0006] 3. The workpiece is easily damaged by clamping and bumping during thirteen clamping operations, with a damage rate of 5%.

[0007] 4. For processing mainly using ordinary equipment and manual operation, the average product qualification rate is 96%, which is lower than the average qualification rate. Summary of the Invention

[0008] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies, improve the machining efficiency and yield rate of valve housings in liquid rocket engines, and realize the transformation of keyway machining (previously done on a slotting machine using a slotting cutter) to machining on a machining center, and the transformation of convex bulge machining (previously done on a conventional milling machine using a conventional end mill) to machining on a machining center. The two aforementioned areas are as follows: Figure 1 The shell diagram shows the area with thickened lines in the BB rotation and E direction.

[0009] The objective of this invention is achieved through the following technical solutions:

[0010] A milling method for the keyway and bulge of a liquid rocket engine valve housing is disclosed. This method employs a four-axis machining center process and designs a straight shank tapered end mill for keyway machining and a bulge milling cutter. Reasonable cutting parameters for keyway machining are determined, and the keyway is milled while maintaining dimensional tolerances, form and position tolerances, and surface roughness requirements. Ultimately, the machining of the housing's two side holes, one oblique side hole, keyway and bulge, threaded hole, internal cavity, scribing, and deburring—previously requiring thirteen steps—can now be completed with a single fixture and two clamping operations, achieving high-quality and high-efficiency machining.

[0011] The milling process for keyways, convex bulges, and other parts on a four-axis machining center is as follows: Figure 5 As shown, the process involves the following steps: clamping the housing, establishing a coordinate system, compiling a machining program, machining the inner hole and four threaded holes on the E-side, rough milling the keyway, finish milling the keyway, machining the inner hole on the other side, machining the petal-shaped parts and 12 holes on the upper end face of the housing, removing the housing, deburring, turning the housing around and clamping it again, machining the petal-shaped parts and 12 holes on the other end face, milling the convex bulge, removing the housing again, deburring, and inspection.

[0012] Design and machine a Φ2 straight shank tapered end mill with a keyway, such as... Figure 3 As shown, the milling cutter is made of cemented carbide. The diameter of the cutting edge at the tip is 0.04-0.06 mm larger than the diameter of the cutting edge near the shank. It is used to machine a 23×15 mm keyway inside a Φ21 side hole of a housing. Figure 1 The thickened lines in direction E represent the work that traditionally requires manual tasks such as marking, keyway insertion, and filing.

[0013] Design and manufacture convex hull milling cutters, such as Figure 4 As shown, the milling cutter's base material is 45# steel with a hardness of HRC32-38. The cutting edge is welded with four carbide cutting edges: two long and two short. The short edges are half the length of the long edges (for vibration reduction). The symmetrical cutting edges have an included angle of 120°, enabling machining of the convex portion of the shell while maintaining a 30° angle with the existing hole (e.g., ...). Figure 1 The surface of the area shown (thickened lines during BB rotation) is aligned, replacing the traditional two-step process on a conventional milling machine where the spindle rotates 30° along the B-axis. It also eliminates the need to place the product in the center of the worktable and use a CNC program to make it move a partial arc around the product's central axis to complete the machining.

[0014] The cutting parameters for machining the keyway involve roughing and semi-finishing with 6mm and 3mm diameter ordinary end mills, leaving a allowance of 0.02-0.05mm. During finishing, the machining center spindle speed is 1900-2100r / min, the feed rate F is 200-240mm, and the depth of cut is ≤0.03mm. At the same time, the dimensional tolerances, form and position tolerances, and surface roughness requirements of the keyway must be guaranteed.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] (1) The present invention adopts an integrated processing method, which can improve the degree of automation and stabilize product quality. The existing thirteen processes are processed by clamping and processing in one tool twice, and the turnover and waiting time of each batch of products is about 6 hours, reducing the time by more than 50%.

[0017] (2) This invention avoids manual operations such as scribing, drilling, milling, and filing, and realizes CNC machining, which reduces labor intensity. The time for clamping and aligning each product in the existing thirteen processes is reduced from 20 minutes to 6 minutes, the processing efficiency of a single shell is increased by at least 50%, and the equipment utilization rate is increased by 30%.

[0018] (3) The present invention changes the clamping process of thirteen steps to two clamping processes, and the workpiece clamping damage and scratch rate is zero.

[0019] (4) This invention adopts integrated processing to replace the previous processing which was mainly manual operation with ordinary equipment, and the product qualification rate is increased from the current 96% to 99.5%.

[0020] (5) The keyway Φ2 straight shank inverted tapered end mill of the present invention has a front end cutting diameter that is different from the diameter of the cutting edge near the shank, and the cutting parameters during machining are matched with each other, so that the keyway can be machined in one go, providing a reference for the machining of similar high-precision keyways.

[0021] (6) The design scheme of the milling cutter for machining convex hulls of the present invention uses 45# steel welded with carbide cutting edge, which achieves the lowest cost. The four cutting edges, two long and two short, avoid vibration caused by excessive cutting surface during use. It can be promoted and applied to similar cutting tools. Attached Figure Description

[0022] Figure 1 For part drawings;

[0023] Figure 2 Diagram showing the casing clamping process;

[0024] Figure 3 Drawing of a Φ2 straight shank inverted tapered end mill;

[0025] Figure 4 Diagram of a convex hull milling cutter;

[0026] Figure 5 This is a flowchart of the milling process for the keyway and convex hull of the housing. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0028] Liquid rocket engine valve housing (e.g.) Figure 1 The blank (shown) is a casting made of aluminum alloy, with an overall cylindrical shape, approximately 200mm in both diameter and length, and an average wall thickness of 6mm. Both the top and bottom ends have flange faces with 12 petal-shaped sections. One end face has 12 evenly distributed smooth holes, and the other end face has 12 evenly distributed threaded holes. Near one end face, perpendicular to the shell axis and parallel to the end face, are two side inner holes distributed at 180°. One of these side inner holes contains a rectangular keyway. A side spout connects the inside and outside of the shell at a 30° angle to the shell axis. The side spout has a cast protrusion within the shell cavity. The shell must be machined, except for the inner and outer surfaces which retain their cast surfaces. The top and bottom end faces, the petal-shaped sections, the two side inner holes and keyway, the 30° side spout's inner shape, and the cast protrusion within the shell cavity all require machining. Areas with high dimensional tolerances include the two side inner holes, one of which has a rectangular keyway, and the 30° side spout's inner shape, with a tolerance of less than 0.03mm. The parts with high geometrical and positional tolerance requirements include the coaxiality of two side inner holes, the positional accuracy of their common axis relative to the housing axis, the symmetry of both sides of the keyway, and the positional accuracy of the 30° side nozzle axis relative to the housing axis, with tolerances less than 0.02mm. The machining difficulty lies in the rectangular keyway within one side inner hole. Due to the limitation of the root radius (R value), only tools with a diameter of Φ2 or less can be used to machine a keyway profile with a length of 20mm. Another difficulty is that without a five-axis machining center, the 30° side nozzle needs to be cast into the housing cavity and machined to meet the existing hole (e.g., ...). Figure 1 (As shown) Connect them.

[0029] A milling method for the keyway and bulge of a liquid rocket engine valve housing, comprising:

[0030] Step 1: Clamp and align the product. Clamp the part onto the dedicated clamping fixture of the four-axis machining center housing (e.g., ...). Figure 2 (as shown);

[0031] Step 2, establish the part coordinate system. Establish the coordinate system at the part's axis.

[0032] Step 3, machine the inner hole on the E-direction side (e.g.) Figure 1 (As shown). Machining 4 internal holes and 4 threaded holes;

[0033] Step 4, rough mill the keyway (the thickened line in the E direction). When machining the 23×15mm keyway, first use 6mm and 3mm diameter ordinary end mills for roughing and semi-finishing, leaving a allowance of 0.03mm;

[0034] Step 5, finish mill the keyway. Use a Φ2 straight shank tapered end mill (e.g., ...) for finish milling. Figure 3As shown), the diameter of the cutting edge at the front end of the milling cutter is 0.05 mm larger than the diameter of the cutting edge near the shank. The spindle speed of the machining center is 2000 r / min, the feed rate F is 200 mm / min, and the depth of cut is 0.015 mm. At the same time, the dimensional tolerance, form and position tolerance and surface roughness requirements of the keyway are guaranteed.

[0035] Step 6, process other parts. Process the inner hole on the other side, the plum blossom petal shape on the upper end face of the shell, and the 12 holes, etc.

[0036] Step 7: Remove the housing, deburr, turn it around and clamp it.

[0037] Step 8: Process the plum blossom petals and 12 holes on the other end face.

[0038] Step 9, Mill the convex hull. Use a milling cutter for machining convex hulls (e.g., ...). Figure 4 As shown), use a CNC program to make it move a partial arc around the product's central axis, while ensuring a 30° angle and flush with the original inner hole surface (as shown). Figure 1 (The bolded lines in the BB rotation shown);

[0039] Step 10, remove the casing;

[0040] Step 11, deburr;

[0041] Step 12: Measure the dimensions of each part of the shell to meet the design requirements.

[0042] The contents not described in detail in this specification are common knowledge to those skilled in the art.

[0043] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A milling method for the keyway and bulge of a valve housing in a liquid rocket engine, characterized in that, include: Step 1: Clamp the part onto the clamping fixture of the four-axis machining center housing; the part refers to the valve housing of a liquid rocket engine. Step 2: Establish the coordinate system at the center of the part; Step 3: Machining the inner side hole; Step 4: First, use end mills of different diameters to rough and semi-finish the keyway of the part, leaving a margin. Step 5: Finish the keyway of the part. Use a straight shank tapered end mill during machining. The diameter of the cutting edge at the front end of the end mill is larger than the diameter of the cutting edge near the shank. Determine the spindle speed, feed rate F, and depth of cut of the machining center to ensure that the dimensional tolerances, form and position tolerances, and surface roughness of the keyway meet the requirements. Step 6: Machin the inner hole on the other side, the plum blossom petal shape on the upper end face of the part, and the 12 holes; Step 7: Remove the parts, deburr them, turn them around and clamp them. Step 8: Machin the plum blossom petals and 12 holes on the lower end face of the part; Step 9: Using a milling cutter for machining convex hulls, use a CNC program to make the milling cutter travel a partial arc around the product's central axis; Step 10: Remove the parts; Step 11: Deburr; Step 12: Measure the dimensions of each part to ensure they meet the design requirements.

2. The milling method according to claim 1, characterized in that, The liquid rocket engine valve housing is cylindrical in shape with 12 petal-shaped flanges at both ends. One end face has 12 smooth holes evenly distributed, and the other end face has 12 threaded holes evenly distributed. Near one end face, two side inner holes are distributed along a 180° angle, perpendicular to the housing axis and parallel to the end face. One of the side inner holes has a rectangular keyway, which is at a 30° angle to the housing axis and connects the inside and outside of the housing. There is a side spout, and the side spout has a cast bulge in the inner cavity of the housing.

3. The milling method according to claim 1, characterized in that, The blank part is a casting, and the material is aluminum alloy.

4. The milling method according to claim 1, characterized in that, The diameter of a straight shank tapered end mill should not exceed Φ2mm.

5. The milling method according to claim 1, characterized in that, When machining the keyway, roughing and semi-finishing were performed using ordinary end mills with diameters of 6mm and 3mm, respectively.

6. The milling method according to claim 1, characterized in that, The machining center spindle speed is 2000 r / min, the feed rate F is 200 mm / min, and the depth of cut is 0.015 mm.

7. The milling method according to claim 1, characterized in that, The straight shank inverted taper end mill is made of cemented carbide.

8. The milling method according to claim 1, characterized in that, The diameter of the cutting edge at the front end of a straight shank inverted taper end mill is 0.04-0.06 mm larger than the diameter of the cutting edge near the shank.

9. The milling method according to claim 1, characterized in that, The straight shank tapered end mill is made of 45# steel with a hardness of HRC32-38. The cutting edge is welded with four carbide cutting edges, two long and two short. The short cutting edge is half the length of the long cutting edge, and the symmetrical cutting edge angle is 120°.

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