Cutting tools and machining methods for machining the inner bore of MAN marine diesel engine cylinder liners

Abstract

This invention provides a cutting tool and machining method for machining the inner bore corrugations of MAN marine diesel engine cylinder liners. The cutting tool includes a tool body with a mounting surface on the upper side of one end. A positioning groove is provided on the mounting surface, and an insert is positioned within the positioning groove. The cutting edge of the insert has an arc-shaped structure, and the surface of the cutting edge is not coplanar with the positioning surface on the side of the insert. Corresponding mounting holes are provided on the positioning groove and the insert. The insert is clamped by a clamping screw, and the mounting holes are compatible with the clamping screw. The cutting edge at the tip of the insert protrudes from the end of the tool body. This cutting tool and machining method can improve and stabilize machining quality, replace traditional welded cutting tools, reduce production costs, and improve machining efficiency.

Description

Technical Field

[0001] This invention relates to the field of mechanical engineering, and in particular to a cutting tool and machining method for machining the inner bore of a MAN marine diesel engine cylinder liner. Background Technology

[0002] MAN low-speed, high-power diesel engines are primarily used in marine shipping and land-based power plants. They are characterized by high power, low fuel consumption, high reliability, and low cost. Cylinder liners are consumable parts of high-power diesel engines. Their inner bore, as a key component in piston movement, is typically made of alloy cast iron, and its dimensional accuracy, contour shape, and surface roughness are subject to specific requirements from the patented company. The corrugated machining of the inner bore is unique to MAN B&W. The corrugation process before honing requires high precision, and its quality not only affects the quality of the cylinder liner itself but also influences the lifespan of the piston rings, directly impacting the performance and economic efficiency of the diesel engine.

[0003] Machining the inner bore of cylinder liners requires specialized tools on a dedicated lathe or boring machine, posing a significant challenge in the manufacturing process. Previously, welded lathe tools were ground into shaped cutting tools for final finishing, carrying the risk of "one cut determining success or failure"—when dimensional deviations or surface roughness issues necessitate rework, tool replacement requires disassembling the entire tooling unit and mounting a new one. Precise control of the new cutting edge's alignment with the previous one is difficult, frequently resulting in misaligned or disordered corrugations, posing a substantial quality risk.

[0004] To address the long-standing reliance on welded, dedicated R-cut forming tools for machining corrugations, SANDVIK developed a non-standard indexable tool in the 1990s. However, this tool was never widely adopted or entered the market, and its whereabouts are now unknown. The main reasons for this were: firstly, the cylinder liners for MAN low-speed, high-power diesel engines are mostly made of alloy cast iron, requiring high-quality cutting tools; secondly, the annual production (or market) was limited, and the consumption of tools for each engine model was relatively low compared to other commonly used tools. Dedicated indexable tools required significant investment for manufacturers with low returns; therefore, tool suppliers were unwilling to develop new dedicated corrugation machining tools. Even now, domestic cylinder liner manufacturers still use welded, formed R-cut turning tools for corrugation machining. However, with MAN B&W's improvement of the performance indicators of marine diesel engines, the requirements for machining the cylinder liner inner hole have become increasingly higher after the drawing was upgraded. Welded forming R-type turning tools are no longer suitable for machining the cylinder liner inner hole corrugations (such as G60 and G80 types) in terms of machining quality. In addition, the cylinder liner market has been booming in recent years, and welded tools are at a disadvantage compared with indexable tool holders in terms of processing costs such as production preparation time and production preparation quantity (inventory). Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a cutting tool and a machining method for machining the inner hole corrugations of MAN marine diesel engine cylinder liners, thereby improving and stabilizing machining quality, replacing traditional welded cutting tools, reducing production costs and improving machining efficiency.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a tool for machining the inner hole corrugations of MAN marine diesel engine cylinder liners, comprising a tool body, a mounting surface on the upper side of one end of the tool body, a positioning groove on the mounting surface, an insert being positioned in the positioning groove, the cutting edge of the insert having an arc structure, the surface where the cutting edge of the insert is located not being coplanar with the positioning surface on the side of the insert, the positioning groove and the insert having corresponding mounting holes, the insert being clamped by a clamping screw, the mounting hole being adapted to the clamping screw, and the cutting edge at the front end of the insert protruding from the end of the tool body.

[0007] In a preferred embodiment, the positioning surface of the blade is a trapezoidal surface, which is adapted to the positioning groove.

[0008] In a preferred embodiment, the upper cutting surface of the blade is inclined in both the front-to-back and left-to-right directions, and the height of the cutting edge at the front end of the blade is higher than that at the rear end.

[0009] In a preferred embodiment, the upper cutting surface of the blade has an inclination angle of 15±0.5° in the front-to-back direction and an inclination angle of 5±0.5° in the left-to-right direction.

[0010] In a preferred embodiment, a chip guide groove is provided on the side of the mounting surface away from the blade.

[0011] In a preferred embodiment, the radius of the cutting edge of the blade is 60mm to 100mm.

[0012] In a preferred embodiment, the upper cutting surface of the blade is provided with a chip-rolling groove near the cutting edge.

[0013] In a preferred embodiment, the blade is made of YG3X material.

[0014] In a preferred embodiment, the end of the blade body where the blade is mounted is inclined, and the end of the blade body is inclined backward from top to bottom.

[0015] The present invention also provides a method for machining the inner hole corrugation of the cylinder liner of a MAN marine diesel engine, comprising the following steps: Step 1: Place the cutting tool in the positioning groove, tighten it with a clamping screw, and install the entire cutting tool on the tool mounting seat of the machine tool;

[0016] Step 2: First, perform semi-finishing on the inner hole corrugations of the cylinder liner. After machining to the required dimensions, record the spindle starting angle a, the Z-axis starting position P, the spindle magnification and the feed magnification, and then retract the tool.

[0017] Step 3: Perform finishing. Change to the corresponding cutting tool, select the same machining program as the semi-finishing, then perform tool setting, spindle positioning angle setting, and Z-axis positioning. Start the program to perform finishing.

[0018] Step 4: After finishing, retract the tool, check the surface quality, and measure the dimensions.

[0019] The present invention provides a cutting tool and machining method for machining the inner hole corrugations of MAN marine diesel engine cylinder liners, which has the following beneficial effects:

[0020] 1. The tool uses a positioning groove and a positioning surface to facilitate accurate blade positioning. The positioning surface and the cutting edge surface do not interfere with each other. The radius of the cutting edge can be adjusted according to different product sizes without affecting the blade positioning and installation.

[0021] 2. The "multi-positioning" method is used for machining. Compared with traditional welding tools, it has the advantage of repeated positioning. Even when changing the cutting tool, it can easily prevent the inner hole ripples from being misaligned or disordered with the semi-finished ripples, ensuring uniform ripples.

[0022] 3. This tool can improve and stabilize machining quality, reduce the surface roughness value of the cylinder liner inner hole, improve the surface quality of the workpiece, and better meet the machining requirements of the corrugated inner hole in the MAN diesel engine cylinder liner upgrade drawing.

[0023] 4. This tool can achieve higher cutting speeds and shorter cutting times, significantly improving machining efficiency.

[0024] 5. Traditional welding tools require disassembling the entire tool and then clamping the new tool when changing them; however, this tool only requires replacing the insert, making it more convenient to use, shortening auxiliary time, and reducing production costs. Attached Figure Description

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0026] Figure 1 This is a top view of the present invention;

[0027] Figure 2 This is the left view of the present invention;

[0028] Figure 3 for Figure 1 A cross-sectional view along plane AA;

[0029] Figure 4 This is a schematic diagram of the blade's structure;

[0030] Figure 5 This is the right view of the blade;

[0031] Figure 6This is a schematic diagram of the clamping screw.

[0032] Figure 7 This is a top view of the preferred blade;

[0033] Figure 8 for Figure 7 A cross-sectional view along plane BB;

[0034] In the figure: 1. Tool body, 2. Blade, 3. Mounting hole, 4. Clamping screw, 101. Mounting surface, 102. Positioning groove, 103. Cutting edge, 201. Surface where the cutting edge is located, 202. Positioning surface, 203. Chip folding groove, 204. Detailed Implementation

[0035] like Figures 1-6 As shown, a cutting tool for machining the inner bore corrugations of MAN marine diesel engine cylinder liners includes a tool body 1 made of 45# steel with a heat treatment hardness of HRC36 or higher and external dimensions of 150mm × 32mm × 32mm. A mounting surface 101 is provided on the upper side of one end of the tool body 1. The mounting surface 101 is an inclined surface. By controlling the inclination angle of the mounting surface 101, combined with the structure of the insert 2, the angle of the cutting edge 201 is controlled. A positioning groove 102 is provided on the mounting surface 101, and the insert 2 is positioned in the positioning groove 102. The insert 2 is made of YG3X material and can be coated. The cutting edge 201 of the insert 2 has an arc structure, and the radius R of the arc of the cutting edge 201 is 60mm to 100mm. The specific arc size of the cutting edge 201 is determined according to the model of the diesel engine cylinder liner to be machined.

[0036] The cutting edge surface 202 of the blade 2 is not coplanar with the positioning surface 203 on the side of the blade 2. The positioning surface 203 is adapted to the positioning groove 102, thereby realizing the installation and positioning of the blade 2.

[0037] Preferably, the positioning surface 203 of the blade 2 is a trapezoidal surface, which is adapted to the positioning groove 102, and the included angle between the two opposing positioning surfaces 203 is 50°. The cross-section of the blade 2 is an isosceles trapezoidal structure, with a top plane of 19.05mm × 19.05mm and a bottom plane of 13.41mm × 13.41mm. The included angle between the two opposing cutting edge surfaces 202 is 50°, and the cutting edge surface 202 and the positioning surface 203 are not coplanar. The positioning of the blade 2 is achieved by the fit between the bottom of the blade 2 and the bottom plane of the positioning groove 102, and by the fit between the positioning surface 203 and the inner wall of the positioning groove 102.

[0038] The positioning groove 102 and the blade 2 are provided with corresponding mounting holes 3. The blade 2 is clamped by a clamping screw 4, and the mounting hole 3 is adapted to the clamping screw 4. The cutting edge 201 at the front end of the blade 2 protrudes from the end of the blade body 1. In this embodiment, the clamping screw 4 is as follows: Figure 6 As shown, the screw is a countersunk screw. The mounting hole 3 on the blade 2 is a countersunk hole that mates with the clamping screw 4. The mounting hole 3 in the positioning groove 102 mates with the screw of the clamping screw 4.

[0039] Because the cutting edge surface 202 and the positioning surface 203 on the side of the insert 2 are not coplanar, they do not interfere with each other. The radius of the cutting edge can be ground according to different product sizes without affecting the positioning and installation of the insert 2. This achieves two "one-piece multi-purpose" functions: the same insert 2 base can grind inserts with various radius R values; the same tool body 1 can be matched with inserts 2 with various R values ​​and applied to the production of cylinder liners of different specifications.

[0040] Preferably, the upper cutting face of the insert 2 is inclined in both the front-to-back and left-to-right directions, and the height of the cutting edge 201 at the front end of the insert 2 is higher than that at the rear end. The rake face of the insert 2 itself is a complete plane without the chip groove 204, i.e., the rake angle is 0°. The tool body is designed with a 15° rake angle, and after installing the insert 2, the rake angle is 15°, which can meet the general requirements for finishing. When the cutting edge 201 is generally worn, it can be reused simply by properly re-grinding the rake face (plane), which is both simple and convenient, ensures the quality of re-grinding, and thus reduces tool costs.

[0041] In this embodiment, the upper cutting surface of the blade 2 has an inclination angle of 15±0.5° in the front-to-back direction and an inclination angle of 5±0.5° in the left-to-right direction.

[0042] The rake angle is mainly to facilitate the rapid sliding of chips away from the rake face. If the angle is too large, it will affect the radius R of the cutting edge 201; if it is too small, it will have no effect.

[0043] Preferred, such as Figure 3 As shown, a chip guide groove 103 is provided on the side of the mounting surface 101 away from the blade 2, and the chip guide groove 103 is inclined towards the rear end of the tool body 1. The chip guide groove 103 is an arc-shaped mechanism. The arc-shaped chip guide groove 103 of the tool body 1 is inclined towards the rear end of the tool body 1, which is conducive to the rapid flow of chips (short chips in cylinder liner machining) away from the workpiece and the cutting edge 201.

[0044] like Figure 3 As shown, the end of the blade body 1 where the blade 2 is mounted is inclined, and the end of the blade body 1 is inclined backward from top to bottom.

[0045] By tilting the end of the cutter body 1, the interference of the blade 2 with the blade 2 during corrugation can be reduced.

[0046] Preferred, such as Figure 7 and 8As shown, the upper cutting face of the insert 2 has a chip groove 204 near the cutting edge 201. The main function of the chip groove 204 is to increase the rake angle, making the cutting edge 201 sharper and improving the surface finish. The disadvantage is reduced durability. Therefore, for machining with a surface roughness value equal to or greater than Ra6.3, the chip groove 204 is usually not provided; for machining with a surface roughness value equal to or less than Ra3.2, the chip groove 204 is used.

[0047] A method for machining the inner bore of a cylinder liner for a MAN marine diesel engine includes the following steps:

[0048] Step 1: Place the cutting tool 2 in the positioning groove 102 and tighten it with the clamping screw 4 to install the entire tool onto the tool mounting seat of the machine tool.

[0049] Step 2: First, perform semi-finishing on the inner hole corrugations of the cylinder liner. After machining to the required dimensions, record the spindle starting angle a, the Z-axis starting position P, the spindle ratio, and the feed ratio. Leave a cutting allowance of Φ0.10mm to Φ0.15mm and then retract the tool.

[0050] Step 3: Perform finishing. Replace with the corresponding insert 2, select the same machining program as the semi-finishing, then perform tool setting, spindle positioning angle setting, and Z-axis positioning. Control the cutting amount on the U-axis to 0.05mm~0.075mm. Set the spindle scaling knob and feed scaling knob to the set positions, keeping them the same as in the semi-finishing. The cutting speed is approximately 40m / min, and the feed rate F is the pitch / revolution. The pitch is adjusted according to the machining requirements of each machine model. Start the program for finishing.

[0051] Step 4: After finishing, retract the tool, check the surface quality, and measure the dimensions.

[0052] This machining method employs a "multi-positioning" approach. During both semi-finishing and finishing with the corrugated tool, the starting angle of the positioning spindle, the starting position of the positioning feed, the feed rate (mm / r), and the starting spindle magnification are all fixed. This ensures that the finishing process maintains the same state as the semi-finishing process, with identical cutting parameters and entry angles, resulting in completely overlapping contour shapes. Compared to traditional welding tools, this method offers the advantage of repeated positioning. Even with a change of insert 2, it easily prevents misalignment or disorder of the internal hole corrugations compared to the semi-finishing corrugations, ensuring uniform corrugation.

[0053] Machining tests were conducted to verify the effectiveness, convenience, stability, and versatility of the cutting tool in machining the inner hole corrugations of the cylinder liner, as well as its comparison with welded cutting tools. The comparison of the machining tests with ordinary welded cutting tools is shown in the table below.

[0054] Table 1 Comparison of Test Processing

[0055]

[0056] As shown in Table 1, this tool can improve and stabilize machining quality, reducing the surface roughness value of the cylinder liner inner bore from Ra6.3 to Ra1.6, thus improving the surface quality of the workpiece and better meeting the machining requirements of the corrugated inner bore in the upgraded MAN diesel engine cylinder liner drawings. It not only fully meets the machining requirements of Ra6.3 for the corrugated groove in the old drawings but is also suitable for the production of the upgraded cylinder liner.

[0057] This tool can achieve higher cutting speeds, shorter cutting times, and significantly improved machining efficiency.

[0058] The blades have high durability, and compared with the original welded turning tools, tool consumption is reduced, which can reduce tool body inventory.

[0059] When changing welding tools, the entire tool needs to be disassembled and a new tool needs to be clamped; however, this tool only requires the replacement of the second insert, making it more convenient to use, shortening auxiliary time, and reducing production costs.

[0060] This cutting tool has successfully machined multiple batches of the new G60 and G80 cylinder liner corrugated inner bores, resulting in significant economic and social benefits.

Claims

1. A tool for honing the bore of a cylinder liner for a diesel engine of a MAN ship, characterized in that The utility model provides a kind of cutter, including tool body (1), the upper side of one end of tool body (1) is equipped with mounting surface (101), mounting surface (101) is equipped with positioning groove (102), blade (2) is positioned in positioning groove (102) and is positioned, the cutting edge (201) of blade (2) is circular arc structure, the plane (202) of the cutting edge of blade (2) is not coplanar with the positioning surface (203) of blade (2) side, positioning groove (102) and blade (2) are equipped with corresponding mounting hole (3), blade (2) is compressed by compression screw (4), mounting hole (3) is adapted with compression screw (4), the cutting edge (201) of the front end of blade (2) protrudes the end of tool body (1);The positioning surface (203) of the blade (2) is trapezoidal surface, trapezoidal surface is adapted with positioning groove (102), the upper tool face of the blade (2) is inclined along front-back direction and left-right direction, the height of the cutting edge (201) of the front end of blade (2) is higher than that of the rear end cutting edge (201); The inclination angle of the upper tool face of the blade (2) along front-back direction is 15±0.5 °, and the inclination angle along left-right direction is 5±0.5 °;The side of the mounting surface (101) away from the blade (2) is provided with a chip guide groove (103), and the chip guide groove (103) is an arc mechanism;The end of the tool body (1) is inclinedly arranged, and the end of the tool body (1) is inclinedly arranged from top to bottom.

2. The tool for honing the inner hole of the cylinder liner of the diesel engine of the MAN ship according to claim 1, characterized in that, The radius of the cutting edge (201) of the blade (2) is 60mm~100mm.

3. The tool for honing the inner hole of the cylinder liner of the diesel engine of the MAN ship according to claim 1, characterized in that, The upper tool face of the blade (2) is provided with a chip curling groove (204) near the cutting edge (201).

4. The tool for honing the inner hole of the cylinder liner of the diesel engine of the MAN ship according to claim 1, characterized in that, The material of the blade (2) is YG3X.

5. A method for processing a corrugation in a bore of a cylinder liner for a diesel engine of a MAN ship, characterized in that, The cutter of any one of claims 1~4 is used to process the inner hole corrugation of the cylinder sleeve of MAN marine diesel engine, comprising the following steps: Step one, place the blade (2) in the positioning groove (102), and compress it with the compression screw (4), then install the entire cutter on the cutter mounting seat of the machine tool; Step two, first semi-finish the inner hole corrugation of the cylinder sleeve, record the starting angle a of the main shaft, the starting position P of the Z-axis, the main shaft ratio and the feed ratio after processing to size, and retract the tool; Step three, finish machining, replace the corresponding blade (2), select the same machining program as semi-finish machining, then perform tool setting and main shaft positioning angle setting and Z-axis positioning, start the program to finish machining; Step four, after finish machining, retract the tool, and check the surface quality and measure the size.

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