Turning method for special-shaped annular cavity of piston rod of large marine diesel engine

Abstract

The invention belongs to the field of marine diesel engine piston rod manufacturing, and particularly relates to a turning machining method for a special-shaped annular cavity of a large marine diesel engine piston rod. A left-hand turning tool body and a tool nose arc turning tool are self-made, and a clamping mode adopts a one-clamping and one-jacking mode or a central frame near-end supporting mode, so that rigidity is enhanced, and deformation is avoided; a hypothetical tool nose point programming method is adopted for numerical control programming, a main shaft reverse rotation dry cutting technology is combined, cooling liquid is omitted, through numerical programming, radial and radial composite feeding paths are achieved, allowance is removed through rough machining and finish machining, tool changing is not needed, a finished product is obtained through one tool, and the environment-friendly requirement is met. Cutter vibration is effectively restrained, and the service life of the cutter is prolonged by multiple times. The method is environment-friendly and safe while ensuring the precision of the workpiece, greatly improves the product percent of pass, reduces the processing cost, and improves the processing efficiency and precision.

Description

Technical Field

[0001] The invention belongs to the field of manufacturing marine diesel engine piston rods, and particularly relates to a turning processing method for a special-shaped ring cavity of a large marine diesel engine piston rod. Background Art

[0002] The piston rod of a large marine main engine is a core component of a marine diesel engine. The special-shaped ring cavity at the piston head end is formed by connecting a 45° conical surface with two arcs. The end arc is recessed 6 - 12 mm from the end face, and has extremely high requirements for shape and position accuracy (tolerance ±0.1 mm) and surface roughness (Ra 1.6).

[0003] The existing turning processing method for the special-shaped ring cavity of a large marine diesel engine piston rod requires manually reinstalling an arc turning tool for rough turning the contour. During finish turning, it relies on manually grinding a high-speed steel forming tool and pouring optical finishing oil for low-speed cutting. This processing method has significant defects: it has extremely high requirements for the operator's skills, and it is easy to cause contour out-of-tolerance or quality accidents due to mistakes; repeated manual measurement leads to low efficiency; optical finishing oil pollutes the environment and endangers health. In addition, existing standard tools cannot complete the processing in one clamping, and have short tool life and high costs. Therefore, there is an urgent need for a turning processing method with high precision, high efficiency, environmental protection and high automation to solve the above technical bottlenecks. Summary of the Invention

[0004] In order to solve the problems of the existing turning processing method for the special-shaped ring cavity of a large marine diesel engine piston rod, which has high requirements for the operator's skills, resulting in unstable product quality and low efficiency; the use of optical finishing oil during processing pollutes the environment and endangers health, cannot complete the processing in one clamping, has short tool life and high costs, etc., the invention provides a turning processing method for the special-shaped ring cavity of a large marine diesel engine piston rod, which is characterized by including the following steps:

[0005] S1: Make a left-handed tool body by oneself;

[0006] S2: Clamp the workpiece:

[0007] Clamp the workpiece by using the one-clamp-one-center method or the center rest support method;

[0008] S3: Install the turning tool:

[0009] Reverse the rotation of the machine tool spindle, install the turning tool with the tip downward in the reverse way, and dry-cut the workpiece;

[0010] S4: Compile a rough machining numerical control program:

[0011] Based on the mathematical formulas x = a + r×sin(θ) and z = b + r×cos(θ), compile a rough machining numerical control program, and the rough machining numerical control program is used for rough turning the surface;

[0012] Where: x is the coordinate value of the machine tool X-axis at the tip point of the turning tool, z is the coordinate value of the machine tool Z-axis at the tip point of the turning tool, a is the abscissa of the center O of the first arc SH, b is the ordinate of the center O of the first arc SH, r is the arc radius of the first arc SH, and θ is the angle between the line connecting the tip point of the turning tool on the first arc SH and the center O of the first arc SH and the negative direction of the machine tool X-axis;

[0013] S5: Rough machining of the special-shaped ring cavity:

[0014] The rough machining feed path is to first turn the 45° cone surface ZM, and then successively machine the first arc SH and the end arc ZH; the distance that the end arc ZH is concave from the end face DM of the special-shaped ring cavity is 6 - 12 mm, and the feed and retract use a composite path of radial and radial radiation;

[0015] S6: Finish machining of the special-shaped ring cavity:

[0016] Program using the imaginary tip point method to finish turn the special-shaped ring cavity.

[0017] According to the turning machining method of the special-shaped ring cavity of a large marine diesel engine piston rod described above, in step S1: the radius of the tip arc of the left turning tool body is 5 mm - 10 mm, the angle Ф between the flank of the turning tool and the tool body is 35° - 40°, the back angle of the turning tool is 11°, the distance JT from the highest point of the tip of the turning tool along the axis to the inner side of the turning tool body is > 12 mm, and the turning tool is made of cemented carbide.

[0018] According to the turning machining method of the special-shaped ring cavity of a large marine diesel engine piston rod described above, in step S2: when the steady rest supports the workpiece, the distance from the support point of the steady rest to the machining surface of the special-shaped ring cavity is ≤ 50 mm.

[0019] According to the turning machining method of the special-shaped ring cavity of a large marine diesel engine piston rod described above, in step S3: when installing the turning tool, the tip position of the turning tool is 0 - 1 mm higher than the axis of the workpiece.

[0020] According to the turning machining method of the special-shaped ring cavity of a large marine diesel engine piston rod described above, in step S4: the radial zero point of the rough machining NC program is the center of the machine tool spindle, and the axial zero point is the end face DM of the special-shaped ring cavity. Remove the workpiece allowance through a composite path of radial and radial radiation, and leave a finish turning allowance of Ф1 mm.

[0021] According to the turning machining method of the special-shaped ring cavity of a large marine diesel engine piston rod described above, in step S4, in the mathematical formula, the θ angle increment is assigned in segments at 0.5° - 2° per cut. The angle range for machining the first arc SH is 0° - 180°, and the angle range for machining the end arc ZH is 180° - 270°.

[0022] According to the turning machining method of the special-shaped ring cavity of the piston rod of a large marine diesel engine described above, in step S4, the rough machining numerical control program is a layer machining, with a radial step of 1.5 - 2.5 mm for each layer and an axial step of 0.5 - 1.0 mm.

[0023] According to the turning machining method of the special-shaped ring cavity of the piston rod of a large marine diesel engine described above, in step S5: The tool path is in sequence: first turn the 45° conical surface ZM, then turn the first arc SH, and finally machine the end arc ZH. The included angle between the feed and retract path and the workpiece axis GZ is 30° - 60°.

[0024] According to the turning machining method of the special-shaped ring cavity of the piston rod of a large marine diesel engine described above, in the feed and retract path, the feed speed is 200 - 300 mm / min and the retract speed is 500 - 800 mm / min.

[0025] According to the turning machining method of the special-shaped ring cavity of the piston rod of a large marine diesel engine described above, in step S6: The cutting linear speed for finish turning is 150 - 200 m / min, the surface roughness of the special-shaped ring cavity after workpiece machining is Ra1.6, and the geometric tolerance is ±0.05 mm.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1. By optimizing the tool structure, clamping method and numerical control programming, the present invention significantly improves the machining efficiency and accuracy. Using a self-made turning tool with a tip radius of R5 - R10 mm and combining with the dry cutting technology of spindle reverse rotation can effectively suppress chatter and extend the tool life by several times.

[0028] 2. By programming with the mathematical formulas X = a + r×sin(θ) and Z = b + r×cos(θ), the present invention realizes a combined feed path of radial and radial radiation. Combining rough turning and finish turning to remove the surplus, the allowance for finish turning is only Ф1 mm, and it can be finished in one cut, with the efficiency increased by more than 10 times.

[0029] 3. The present invention cancels the use of coolant, meeting the environmental protection requirements. The clamping method adopts one chuck and one center support or the near-end support of the steady rest to enhance rigidity and avoid deformation.

[0030] 4. The present invention uses the imaginary tip point method for programming to ensure that the geometric accuracy reaches ±0.05 mm, the surface roughness stably meets Ra1.6, and the one-time inspection pass rate is 100%. In addition, manual intervention is greatly reduced, and the processing cost is reduced by more than 30%. It is applicable to the batch production of large piston rods with a cylinder diameter ≥ 600 mm. Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the machining method steps of the turning machining method of the special-shaped ring cavity of the piston rod of a large marine diesel engine of the present invention.

[0032] Figure 2 It is a schematic structural diagram of a workpiece processed by a turning method for a special-shaped ring cavity of a large marine diesel engine piston rod according to the present invention.

[0033] Figure 3 It is a schematic structural diagram of the special-shaped ring cavity of a workpiece processed by a turning method for a special-shaped ring cavity of a large marine diesel engine piston rod according to the present invention.

[0034] Figure 4 It is a schematic diagram for calculating the tool coordinates of a turning method for a special-shaped ring cavity of a large marine diesel engine piston rod according to the present invention.

[0035] Figure 5 It is a top view of a schematic structural diagram of a turning tool body of a turning method for a special-shaped ring cavity of a large marine diesel engine piston rod according to the present invention.

[0036] Figure 6 It is a left view of a schematic structural diagram of a turning tool body of a turning method for a special-shaped ring cavity of a large marine diesel engine piston rod according to the present invention.

[0037] Figure 7 It is a front view of a clamping schematic diagram of a turning tool body of a turning method for a special-shaped ring cavity of a large marine diesel engine piston rod according to the present invention.

[0038] Figure 8 It is a top view of a clamping schematic diagram of a turning tool body of a turning method for a special-shaped ring cavity of a large marine diesel engine piston rod according to the present invention.

[0039] Figure 9 It is a left view of a clamping schematic diagram of a turning tool body of a turning method for a special-shaped ring cavity of a large marine diesel engine piston rod according to the present invention.

[0040] Figure 10 It is a schematic diagram of a turning path for machining a 45° conical surface machining area of a turning method for a special-shaped ring cavity of a large marine diesel engine piston rod according to the present invention.

[0041] Figure 11 It is a schematic diagram of a rough machining first-stage circular arc feed route of a turning method for a special-shaped ring cavity of a large marine diesel engine piston rod according to the present invention.

[0042] Figure 12 It is a schematic diagram of a rough machining end-stage circular arc feed route of a turning method for a special-shaped ring cavity of a large marine diesel engine piston rod according to the present invention.

[0043] Figure 13 It is a schematic diagram of a finish machining end-stage circular arc feed route of a turning method for a special-shaped ring cavity of a large marine diesel engine piston rod according to the present invention.

[0044] In the figure: 1 - turning tool body, 2 - turning tool, 100 - workpiece, 101 - special-shaped ring cavity, ZM - conical surface, SH - first arc, ZH - end arc, DM - end face DM of the special-shaped ring cavity, JT - distance from the axial highest point of the turning tool tip to the inner side of the turning tool body, Q - machine zero point, GZ - workpiece axis. Specific implementation mode

[0045] Preferred implementation mode

[0046] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0047] As Figures 1 to 13 shown: In this embodiment, a turning processing method for a special-shaped ring cavity of a large marine diesel engine piston rod includes the following steps:

[0048] S1: Self-manufacture a left-handed turning tool body 1;

[0049] S2: Clamp the workpiece 100:

[0050] Clamp the workpiece 100 by using the one-clamp-one-top method or the center support method;

[0051] S3: Install the turning tool 2:

[0052] The main shaft of the machine tool rotates in reverse, and the turning tool 2 is installed with the tip downwards, and the workpiece is dry-turned.

[0053] S4: Compile a rough machining numerical control program:

[0054] Based on the mathematical formulas x = a + r×sin(θ) and z = b + r×cos(θ), compile a rough machining numerical control program, and the rough machining numerical control program is used for rough turning the surface;

[0055] Among them: x is the machine tool X-axis coordinate value of the turning tool tip point of the turning tool 2, z is the machine tool Z-axis coordinate value of the turning tool tip point of the turning tool 2, a is the abscissa of the center O of the first arc SH, b is the ordinate of the center O of the first arc SH, r is the arc radius of the first arc SH, and θ is the included angle between the connection line from the turning tool tip point on the first arc SH to the center O of the first arc SH and the negative direction of the machine tool X-axis;

[0056] S5: Rough machine the special-shaped ring cavity:

[0057] The rough machining feed path is to first machine the 45° conical surface ZM, and then successively machine the first arc SH and the end arc ZH; the distance that the end arc ZH is concave from the end face DM of the special-shaped ring cavity is 6 - 12 mm, and the feed and retraction use a composite path of radial and radiation;

[0058] S6: Finish machining the special-shaped ring cavity:

[0059] Program using the imaginary tool tip point method to finish turning the special-shaped ring cavity.

[0060] In step S1: The radius of the tool tip arc of the turning tool 2 on the left-hand tool body 1 is 5 mm to 10 mm, the angle Ф between the flank of the turning tool and the tool body is 35° to 40°, the back angle of the turning tool is 11°, the distance JT from the axial highest point of the tool tip to the inner side of the tool body is > 12 mm, and the turning tool is made of cemented carbide.

[0061] In step S2: When the steady rest supports the workpiece, the distance from the support point of the steady rest to the machining surface of the special-shaped ring cavity is ≤ 50 mm.

[0062] In step S3: When installing the turning tool 2, the position of the tool tip of the turning tool 2 is 0 to 1 mm higher than the axis GZ of the workpiece.

[0063] In step S4: The radial zero point of the rough machining NC program is the center of the machine tool spindle, and the axial zero point is the end face DM of the special-shaped ring cavity. Remove the workpiece allowance through a combined path of radial and radial radiation, and leave a finish turning allowance of Ф1 mm.

[0064] In step S4, the θ angle increment in the mathematical formula is assigned in segments at 0.5° to 2° per tool path. The angle range during the machining of the first arc SH is 0° to 180°, and the angle range during the machining of the end arc ZH is 180° to 270°.

[0065] In step S4, the rough machining NC program is a layer-by-layer machining. The radial step size for each layer is 1.5 to 2.5 mm, and the axial step size is 0.5 to 1.0 mm.

[0066] In step S5: The tool path is as follows: First, turn the 45° cone surface ZM, then turn the first arc SH, and finally machine the end arc ZH. The angle between the feed and retract path and the axis GZ of the workpiece is 30° to 60°.

[0067] In the feed and retract path, the feed speed is 200 to 300 mm / min, and the retract speed is 500 to 800 mm / min.

[0068] In step S6: The finish turning cutting linear speed is 150 to 200 m / min. The surface roughness of the special-shaped ring cavity after workpiece machining is Ra1.6, and the geometric tolerance is ±0.05 mm. Specific implementation method:

[0070] This embodiment is applicable to the turning machining of the special-shaped ring cavity of the piston rod of models with a cylinder diameter of 600 mm and above.

[0071] First, as Figures 5 - 6As shown: For tool preparation, a 40×40mm waste tool body is selected to transform and manufacture a self-made left-hand turning tool. The radius of the cutting edge arc of the turning tool 1 is R8mm. The angle Ф between the flank of the turning tool and the tool body is 38°. The distance JT from the highest point of the cutting edge in the axial direction to the inner side of the tool body is 15mm. The material is a cemented carbide insert with a back rake angle of 11°, and it is clamped by screws.

[0072] Secondly, for the clamping of workpiece 100, the rod diameter of the piston rod of workpiece 100 is clamped by one chuck and one center. The chuck clamps one end, and the tailstock center tightens the other end; if a steady rest is selected to support workpiece 100, the distance from the support point of the steady rest to the machining surface of the special-shaped ring cavity is 40mm to avoid chatter and ensure rigidity.

[0073] Next, install turning tool 2 with the cutting edge facing downwards, reverse the turning tool 2. When the CNC machine tool spindle rotates in reverse, it can press down on workpiece 100 during cutting to avoid chatter during turning; no coolant is poured, and dry cutting is performed.

[0074] Again, for CNC programming, taking the center of the workpiece spindle GZ as the radial zero point and the end face DM of the special-shaped ring cavity as the axial zero point, draw a CAD coordinate diagram according to the finished product size. The rough turning program uses the formula X = 380 + 8×sin(θ), Z = 50 + 8×cos(θ), where θ increases by 1° from 0° to 180°, and the allowance is removed layer by layer, leaving a finishing allowance of Ф1mm. Compile the CNC program: According to the method of combining radial and radial, use the imaginary cutting edge point method to program and finish turn the finished product in one cut:

[0075] In this embodiment, the radius of the cutting edge arc of turning tool 2 == 8mm;

[0076] The CNC program is as follows:

[0077] R1 = a; Starting point X value

[0078] R2 = b; Each cutting step

[0079] R3 = c; Starting point Z value

[0080] R4 = d; Final value in the Z direction

[0081] YY1: R3 = R3 - R2; Move one step towards the Z-axis zero point

[0082] R1 = R1 - 2*R2; Decrease the diameter by one step

[0083] YY2: M4;

[0084] G0 Z = R3; Position in the Z direction

[0085] G1 X = R1; Feed in the X direction

[0086] Z1;

[0087] G0 X400;

[0088] Z32;

[0089] IF R3>R4 GOTOB YY1;

[0090] G0 Z=e, X=f;

[0091] R11 = e; X value of the center coordinate of the arc segment

[0092] R12 = f; Z value of the center coordinate of the arc segment

[0093] R13 = g; Profile arc radius - tip arc radius

[0094] R14 = h; Starting value of the angle

[0095] R15 = j; Increment value per cut

[0096] R16 = k; End value of the angle

[0097] YY3: G1 X = R11 + 2 * R13 * SIN(R14) Z = R12 + R13 * COS(R14);

[0098] G0 X = e Z = f; Rapid retraction to the center position of the first arc segment

[0099] R14 = R14 + R15; Angle self - increment

[0100] IF R4 <= k GOTOB YY3; Program jump

[0101] At this point, the remaining allowance of the first arc profile has been completely removed. From Figure 4 As shown, the remaining allowance of the end - segment arc ZH is not large. Here, the programming method of the first arc segment SH can be used to remove the remaining allowance, or 2 - 3 coordinate points can be captured through CAD for programming to remove the allowance at this place.

[0102] Without changing the turning tool, using the imaginary tip point method programming method to compile the finish - turning program, turning the finished product in one cut, the numerical control program for precision machining of the special - shaped ring cavity is as follows:

[0103] G0 X470;

[0104] Z37.786;

[0105] G1 X380;

[0106] M4;

[0107] G91 G2 X - 43.112Z - 21.556;

[0108] G2 X12.376 Z-27.989 CR=17; Finish turning arc (R value = arc radius - tip radius of the tool)

[0109] G2 X10.008 Z5.425 CR=4; Finish turning arc

[0110] G1 Z10;

[0111] M2;

[0112] Then, perform turning operations with the machining parameters set as follows: spindle speed 200 r / min, cutting speed 180 m / min, depth of cut 2 mm, radial step 1.5 mm, dry cutting.

[0113] Start the spindle of the CNC machine tool to rotate in reverse. The tip of tool 2 is 0.5 mm higher than the workpiece axis GZ. First, rough turn the 45° cone surface and the arc section according to the programmed path, and then finish turn the finished product in one pass. Monitor the tool wear in real time during machining and replace the insert every 5 parts processed.

[0114] Finally, conduct quality inspection. Use a coordinate measuring machine to measure the profile dimensions, control the geometric tolerance within ±0.05 mm, and use a surface roughness meter to measure Ra ≤ 1.6 μm.

[0115] This method realizes high-efficiency and high-precision machining by optimizing the tool and the process. The tool life is 4 times that of the traditional method, and the single-piece machining time is shortened from 8 hours to 45 minutes. It is suitable for mass production.

[0116] As described above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A turning processing method for a special-shaped ring cavity of a piston rod of a large marine diesel engine, characterized in that Including the following steps: S1: Self - manufacture the left - hand tool body; S2: Clamp the workpiece: Clamp the workpiece by using the one - clamp - one - support method or the steady rest support method; S3: Install the tool: The spindle of the machine tool rotates in reverse, install the reverse - turned tool with the tool tip facing downwards, and dry - cut the workpiece; S4: Compile the rough - machining NC program: Based on the mathematical formulas x = a + r×sin(θ) and z = b + r×cos(θ), compile the rough - machining NC program, which is used for rough - turning the machining surface; Where: x is the coordinate value of the machine tool X - axis of the tool tip point, z is the coordinate value of the machine tool Z - axis of the tool tip point, a is the abscissa of the center O of the first - stage arc SH, b is the ordinate of the center O of the first - stage arc SH, r is the radius of the first - stage arc SH, and θ is the angle between the line connecting the tool tip point on the first - stage arc SH to the center O of the first - stage arc SH and the negative direction of the machine tool X - axis; S5: Rough - machine the special - shaped ring cavity: The rough - machining feed path is to first machine the 45° taper surface ZM, and then successively machine the first - stage arc SH and the end - stage arc ZH; the distance that the end - stage arc ZH is concave from the end face DM of the special - shaped ring cavity is 6 - 12 mm, and the approach and retraction of the tool use a composite path of radial and radial - like paths; S6: Finish - machine the special - shaped ring cavity: Program using the imaginary tool tip point method and finish - turn the special - shaped ring cavity.

2. The turning processing method of the special-shaped ring cavity of the piston rod of a large marine diesel engine according to claim 1, characterized in that, In step S1: The radius of the tool tip arc of the left - hand tool body is 5 mm - 10 mm, the angle Ф between the flank of the tool and the tool body is 35° - 40°, the clearance angle of the tool is 11°, the distance JT from the highest point of the tool tip in the axial direction to the inner side of the tool body is > 12 mm, and the tool is made of cemented carbide.

3. The turning machining method for the special-shaped ring cavity of the piston rod of a large marine diesel engine according to claim 2, characterized in that, In step S2: When the steady rest supports the workpiece, the distance from the steady rest support point to the machining surface of the special - shaped ring cavity is ≤ 50 mm.

4. A turning method for a special-shaped ring cavity of a piston rod of a large marine diesel engine according to claim 3, characterized in that, In step S3: When installing the tool, the position of the tool tip is 0 - 1 mm higher than the axis of the workpiece.

5. A turning method for a special-shaped ring cavity of a piston rod of a large marine diesel engine according to claim 4, characterized in that, In step S4: The radial zero point of the rough - machining NC program is the center of the machine tool spindle, and the axial zero point is the end face DM of the special - shaped ring cavity. Remove the workpiece allowance through a composite path of radial and radial - like paths, and leave a finish - turning allowance of Ф1 mm.

6. A turning machining method for a special-shaped ring cavity of a piston rod of a large marine diesel engine according to claim 5, characterized in that: In step S4, in the said mathematical formula, the θ - angle increment is assigned in segments at 0.5° - 2° per tool path, the angle range during the machining of the first - stage arc SH is 0° - 180°, and the angle range during the machining of the end - stage arc ZH is 180° - 270°.

7. A turning processing method for a special-shaped ring cavity of a piston rod of a large marine diesel engine according to claim 6, characterized in that: In step S4, the rough - machining NC program is a layer - by - layer machining, the radial step distance of each layer is 1.5 - 2.5 mm, and the axial step distance is 0.5 - 1.0 mm.

8. A turning method for a special-shaped ring cavity of a piston rod of a large marine diesel engine according to claim 7, characterized in that, In step S5: The feed path is successively: first machine the 45° taper surface ZM, then machine the first - stage arc SH, and finally machine the end - stage arc ZH. The angle between the approach and retraction path and the axis GZ of the workpiece is 30° - 60°.

9. A turning method for a special-shaped ring cavity of a piston rod of a large marine diesel engine according to claim 8, characterized in that: In the said approach and retraction path, the approach speed is 200 - 300 mm / min, and the retraction speed is 500 - 800 mm / min.

10. A turning method for a special-shaped ring cavity of a piston rod of a large marine diesel engine according to claim 9, characterized in that, In step S6: The finish - turning cutting linear speed is 150 - 200 m / min, the surface roughness of the special - shaped ring cavity after workpiece machining is Ra1.6, and the geometric tolerance is ±0.05 mm.

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