Method for processing a cylindrical thin-walled part and processing die

Abstract

The present application relates to the technical field of light alloy manufacturing, and particularly relates to a machining method and machining die for a cylindrical thin-wall part, comprising: fixing and connecting a milling machining die with two end surfaces of a thin-wall part blank which has completed reference positioning line scribing, fixing a guard plate with the outer side of the side surface of the thin-wall part blank; setting two reference holes on the reference positioning line; stabilizing the thin-wall part blank; adopting the milling machining die to perform second and third milling machine processing; the milling machining die for milling machine processing is provided with a guard plate which is fixed with the outer side of the side surface of the thin-wall part blank. The present application adopts a special milling machining die to process the end surface of the thin-wall part, adopts a processing mode of "rough machining-semi-finish machining-finish machining", reduces deformation and mechanical damage caused by accumulated stress of the thin-wall material, improves processing precision, and reduces radial vibration and deformation of the cylindrical part in two directions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of light alloy manufacturing, and particularly relates to a machining method and machining die for a cylindrical thin-wall part. BACKGROUND

[0002] Large cylindrical thin-wall parts are widely needed in the field of aviation. Since welding processing or welding process and casting process cannot meet the precision requirements, the production of light alloy hollow parts mainly adopts machine tool processing (turning, milling, etc.).

[0003] For high-precision large cylindrical thin-wall parts, a common machining method is to machine a large magnesium alloy blank formed by casting to obtain more accurate internal structure and size. Since the thin-wall part is easily clamped from the outer wall and deformed, the fixing die for machine tool processing of the thin-wall part is usually supported and fixed inside the cavity of the part. On the one hand, such a die fixedly occupies the inner cavity space of the part, especially affecting the fine processing of the inner wall of the part, such as milling. On the other hand, the thin-wall part is prone to vibration during radial machining. The defects of the existing die determine that it can only be fixed at one end of the part to be machined, and the other end is left for the opening end of the main shaft of the lathe. Since the opening end lacks die fixing, the vibration is particularly serious, which seriously affects the machining precision of the equipment. At the same time, for large magnesium alloy thin-wall parts, the vibration of the side wall of the part is more serious due to the decrease of the radial cross-sectional curvature.

[0004] At present, there is an urgent need for a machining equipment and machining method for large cylindrical thin-wall parts to solve the problems of fixing and reducing the machining precision caused by vibration during machining of large cylindrical thin-wall parts. In addition, during the fine machining of cylindrical thin-wall parts, especially magnesium alloy materials, the slow tool feed speed and high local temperature cause the magnesium alloy to easily react with nitrogen and oxygen in the air or even burn, and there is always a serious safety hazard in magnesium alloy machining. If the tool feed speed is too fast, the instability of the contact between the tool and the magnesium alloy is increased, which further aggravates the vibration. Therefore, it is necessary to improve the machining process of the existing cylindrical thin-wall parts. SUMMARY

[0005] In view of the above analysis, the present application aims to provide a machining method and machining die for a cylindrical thin-wall part to solve at least one of the problems of poor die fixing stability, easy vibration and poor magnesium alloy machining safety in the prior art.

[0006] The main purpose of the present application is achieved by the following technical solutions:

[0007] A machining method for a cylindrical thin-wall part, comprising:

[0008] The milling tool is fixedly connected with the two end faces of the thin-walled part blank which is drawn with the reference positioning line, and the side of the thin-walled part blank is fixedly connected with the outer side of the baffle in the milling tool; and the milling tool is left with a margin;

[0009] Two reference holes are arranged on the outer edge of the free end face of the thin-walled part blank which is milled, and the center points of the reference holes are collinear with the reference positioning line of the thin-walled part blank;

[0010] The thin-walled part blank which is milled is stabilized;

[0011] Based on the reference holes, the thin-walled part blank which is stabilized is milled for the second time by using the milling tool; the second milling is left with a margin;

[0012] Based on the reference holes, the thin-walled part blank which is milled for the second time is milled for the third time by using the milling tool; the third milling processes the window on the side of the thin-walled part blank to the target size.

[0013] Preferably, the milling tool is provided with a first pressing plate at one end which is press-fit connected with the first end face of the cylindrical thin-walled part, and a first bottom fixing member at the other end which is press-fit connected with the second end face of the cylindrical thin-walled part; the milling tool is further provided with a first pull rod which connects the first pressing plate and the first bottom fixing member.

[0014] Preferably, the first pull rod is provided with a plurality of first pull rods along the side circumferential direction, and the milling tool is provided with a baffle on the side of the thin-walled part which limits the radial shaking of the thin-walled part; the baffle circumferentially surrounds the side and is provided with a first through hole which is arranged in the axial direction; the first through hole corresponds to the first pull rod one by one; the first pull rod passes through the first through hole so that the baffle is fixed in the radial direction; at the same time, the baffle and the side are circumferentially attached to generate a large enough static friction force, so that the baffle is fixed in the axial direction; the circumferential attachment of the baffle to the side can limit the deformation or shaking of the thin-walled part to the outside in the radial direction.

[0015] Preferably, the reference holes are obtained by using a machine tool hole forming device, and a positioning pin is inserted to correct the position of the reference hole.

[0016] Preferably, the positioning pin is inserted to correct the position of the reference hole, including:

[0017] S401: a first coordinate axis is arranged in the vertical horizontal plane direction, a second coordinate axis is taken as the rotation axis of the machine tool rotating platform, a third coordinate axis is arranged in the horizontal plane and perpendicular to the first coordinate axis and the second coordinate axis, and a space coordinate system is constructed;

[0018] S402: Select one of the positioning pin of the reference hole as the first positioning pin, set the dial gauge on the machine spindle to contact the highest side of the first positioning pin, and record the dial gauge reading;

[0019] S403: Select another positioning pin of the reference hole as the second positioning pin, rotate the machine tool rotary platform by 180° using its own scale, keep the machine spindle coordinates on the first and second coordinate axes unchanged, contact the highest side of the second positioning pin, and record the dial gauge reading;

[0020] S404: Correct the reference hole based on the two dial gauge readings;

[0021] If the difference between the two dial gauge readings is less than the third threshold δ3, it is determined that the reference hole setting meets the requirements;

[0022] If the difference between the two dial gauge readings is greater than the third threshold δ3, based on the corrected reference positioning line, ream the original reference hole, select a matching positioning pin, and repeat S402-S403 until the difference between the two dial gauge readings is less than the third threshold δ3.

[0023] Preferably, the determination of the highest side of the pin in S402 and S403 includes:

[0024] S411: Set the first coordinate axis in the vertical horizontal plane direction, take the rotation axis of the machine tool rotary platform as the second coordinate axis, set the third coordinate axis perpendicular to the first and second coordinate axes in the horizontal plane, and construct a space coordinate system with the center of the machine tool rotary platform as the origin;

[0025] S412: Select the positioning pin of one of the reference holes and insert the matching positioning pin, set the dial gauge on the machine spindle to contact the top area of one end of the positioning pin side and show the number, keep the first and second coordinate axes of the machine spindle unchanged, move the machine spindle parallel to the third coordinate axis, and keep the dial gauge number zero; Record the space coordinates when the dial gauge number is the smallest as the highest point coordinates of one end of the positioning pin side;

[0026] S413: Obtain the highest point coordinates of the other end of the positioning pin side in the same way, compare the highest point coordinates of the two ends, and take the larger value of the first coordinate axis as the highest point coordinates of the pin side.

[0027] Preferably, S401 and S402 further include correction of the opening flatness of the reference hole:

[0028] Compare the coordinates (x1, y1, z1) and (x2, y2, z2) of the highest points at both ends obtained in steps S412 and S413, and obtain the coordinate differences △x, △y, △z for each coordinate axis; where △x = |x1-x2|, △y = |y1-y2|, △z = |z1-z2|.

[0029] If Δx, Δy, and Δz are all less than the fourth threshold δ4, then the flatness of the opening of the reference hole is deemed to meet the requirements.

[0030] If any of the values ​​of △x, △y, and △z is greater than the fourth threshold δ4, then based on the corrected reference positioning line, the original reference hole is enlarged, and a matching positioning pin is selected for positioning and installation. Then, S322-S323 is repeated until △x, △y, and △z are all less than the fourth threshold δ4.

[0031] Preferably, the third milling process, which processes the window on the side of the thin-walled part blank to the target size, includes:

[0032] S701: Using the milling die for machining the inner side wall of a thin-walled part, the hollow annular end face of the thin-walled part blank is fixed on the rotary table, with the free end face positioned close to the end of the machining tool.

[0033] S702: Connect the center of the window to the axis of the workpiece blank in its radial plane. Obtain the angle α between this line and the machining datum line using an angle measuring device. Based on the adjacent order of the windows, number them sequentially as the first window, ..., the nth window, and the corresponding angle α is numbered α1, ..., α2. n ;

[0034] S703: Calculate the difference Δα between any two adjacent windows and the machining datum line, which serves as the rotation angle of the part blank and its connected rotary platform during machining of adjacent windows; where Δα satisfies: Δα=α k -α k-1 , k≤n; k represents the window number, α k Let be the angle between the center of the k-th window and the line connecting the center of the part blank to the machining datum line in its radial plane.

[0035] S704: With the vertical state of the machining datum line as the initial position, set the machining area of ​​the milling tool to be in the horizontal plane below the axis, rotate the rotary platform by α1 degrees so that the line connecting the first window and the axis is in the initial position, the machining plane of the first window is in the machining area of ​​the milling tool, and mill the first window to the target size;

[0036] S705: Rotate the rotary platform by α2-α1 degrees so that the machining plane of the second window is in the machining area of ​​the milling tool, and mill the second window to the target size;

[0037] S706: Rotate the rotating platform by α3-α2, ..., α n -α n-1 The degree is adjusted so that the machining plane of the third window, ..., the nth window is in the machining area of ​​the milling cutter, and the third window, ..., the nth window is milled to the target size; the third milling machining of the thin-walled part blank is completed.

[0038] Preferably, the stabilization process further reduces residual stress from the pre-processing stage, including the following steps:

[0039] S501: Heat treatment at 120±10℃ for 2h~6h, then air-cooled down to room temperature;

[0040] S502: Heat-treat at 120±10℃ for 2h~6h, then cool to room temperature with the furnace.

[0041] A machining mold for a cylindrical thin-walled part includes a milling mold, wherein a protective plate is circumferentially fitted on the outer side of the thin-walled part blank for use in the above-mentioned machining method.

[0042] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0043] (1) The present invention uses a specially made milling die to process thin-walled parts with window structures. The processing method of "roughing-semi-finishing-finishing" reduces the deformation and mechanical damage caused by the accumulated stress of thin-walled materials and improves the processing accuracy. Each processing includes a milling operation. In the subsequent milling operation, the present invention improves the rigidity of the side of the thin-walled part blank by setting a guard plate on the milling die. When the thin-walled part blank is milled, the guard plate can provide support force in both radial directions from the inside to the outside and from the outside to the inside, thereby reducing vibration and deformation in both radial directions and ensuring the dimensional accuracy of the side milling of window structures.

[0044] (2) The present invention fixes the guard plate radially by the first tie rod and presses it circumferentially around the side, which improves the rigidity of the side of the thin-walled part blank. When the milling cutter processes the first groove, the guard plate provides circumferential support force to the side. This support force is opposite to the force applied by the milling cutter, thus making the thin-walled part blank stable and less prone to vibration or deformation from the outside to the inside. On the one hand, the side of the guard plate and the arched structure of the guard plate can effectively disperse the force applied by the milling cutter. On the other hand, the circumferential support force provided by the guard plate to the side means that the guard plate applies force evenly at each point of contact with the side, thus preventing deformation of the side of the thin-walled part blank caused by local stress concentration. Therefore, when the thin-walled part blank is milled, the guard plate can provide support force in both radial directions, thereby reducing vibration and deformation in both radial directions.

[0045] (3) By setting the bottom of the guard plate to be fixedly connected to the first bottom fixing member, and the side of the guard plate to be attached to the side of the thin-walled part blank, the noise of the processing area during milling can be transmitted to the machine tool through the first bottom fixing member, reducing the noise from spreading into the air and reducing environmental noise.

[0046] (4) By setting through holes in the protective plate, the present invention facilitates the monitoring of the wall thickness of each area during milling; at the same time, the through holes improve ventilation and heat dissipation during side processing, which helps to prevent the blank processing surface from overheating, causing deformation or even damage and burning of the blank.

[0047] (5) By providing a positioning block on the inner side of the cast thin-walled part blank, and using the line connecting the center of the positioning block in the radial plane as the reference in the first vertical lathe process, the present invention can greatly reduce the workload of machine tool alignment and zeroing in subsequent processes while meeting the accuracy requirements; and further utilizes the positioning block and the rotation axis to correct the position and determine the machining reference positioning line; and further utilizes the reference hole on the end face of the machining reference positioning line as the transmission medium of the original reference, ensuring the continuity of the reference and improving the machining accuracy.

[0048] (6) The present invention uses laser scanning imaging technology to preliminarily determine the wall thickness of each section of the casting, determine the correction position of the rotation axis centerline, and adjust and coordinate the wall thickness of each processing part based on the correction axis centerline to make the wall thickness of the part as uniform as possible before processing, so as to ensure that the processing allowance of each surface is uniform and the wall thickness is uniform and meets the requirements. While ensuring the accuracy of the reference scribing, it greatly reduces the workload of machine tool alignment and zeroing in subsequent processes.

[0049] (7) In this invention, after the blank is corrected by positioning reference line and axis, the deformation and precision error of the casting process are removed by vertical lathe machining, so that the rotation axis of the blank coincides with the geometric center of its end face, and the positioning reference line provides a reference for the next step of machining.

[0050] (8) According to the different processing parts, the present invention adopts the method of processing in different areas, dividing the arc surface, and then planning the processing trajectory in each segmented area to process window by window, instead of fixing the thin-walled part blank, controlling the movement of the tool, reducing the displacement of the tool movement, avoiding the processing vibration caused by the excessive overhang of the tool, thereby ensuring the processing accuracy and improving the processing efficiency.

[0051] (9) By setting a first pressure plate, a first bottom fixing member, a first tie rod and a guard plate in the milling mold, the present invention can achieve pressing and fixing of thin-walled parts, while greatly reducing the adverse effects of vibration on machining accuracy during side machining; it improves the defects of easy vibration and poor machining accuracy when machining the side of thin-walled parts from the inside to the outside in the prior art.

[0052] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained through the embodiments described and the accompanying drawings, which are particularly pointed out. Attached Figure Description

[0053] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0054] Figure 1 This is a schematic diagram of a thin-walled part viewed from a 45° angle in one embodiment of the present invention;

[0055] Figure 2 This is a 45° top view of a milling die for thin-walled parts according to one embodiment of the present invention;

[0056] Figure 3 This is a view of the installation method of a milling mold for thin-walled parts according to one embodiment of the present invention;

[0057] Figure 4 This is a cross-sectional view of plane AA of a view of the installation method of a milling mold for thin-walled parts in one embodiment of the present invention;

[0058] Figure 5 This is a schematic diagram of a milling process for thin-walled parts according to one embodiment of the present invention;

[0059] Figure 6 This is a flowchart of a milling method for a thin-walled part according to one embodiment of the present invention;

[0060] Figure 7 This is a schematic diagram of a vertical lathe machining method for thin-walled parts in one embodiment of the present invention.

[0061] Figure label:

[0062] Thin-walled part blank 1; side 101; first end face 102; second end face 103; window 1011; positioning block 1012; first groove 1013; milling mold 2; first pressure plate 201; guard plate 202; first bottom fixing part 203; first pull rod 204; connecting structure 205; second through hole 2021; first through hole 2022; external support structure 301; second bottom fixing part 303; internal support structure 305; second pressure plate 307; connecting pressure plate 3011; external support rod 3012; second pull rod 3013; inner support plate 3051; inner support rod 3052; on rotary worktable 4; three-jaw chuck 5; machine tool work platform 6; machining tool 7. Detailed Implementation

[0063] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0064] It should be noted that in this invention, the axial direction is perpendicular to the two end faces of the thin-walled part, and the radial direction is parallel to the two end faces of the thin-walled part.

[0065] This invention discloses a cylindrical thin-walled part, such as Figure 1 As shown, it includes: a first end face 102, a second end face 103, and a side surface 101 connecting the first end face 102 and the second end face 103; the first end face 102 and the second end face 103 are unobstructed free end faces.

[0066] like Figure 1 As shown, the side 101 is provided with multiple windows 1011, and at least one set of windows 1011 is symmetrically arranged relative to the axis center of the thin-walled part. After the thin-walled part blank 1 is fixed by the milling mold, the milling cutter penetrates the thin-walled part blank through the first end face 102 to process the windows 1011 in the side 101 to obtain windows 1011 that meet the target size.

[0067] It should be noted that the blank of the thin-walled part is obtained by casting. The dimensional accuracy of the window 1011 and other dimensions in the blank obtained by casting cannot meet the requirements. Therefore, it is necessary to further process it with milling tools to obtain the specified shape and accuracy.

[0068] The side 101 of the thin-walled part is provided with a plurality of positioning blocks 1012, and at least one set of positioning blocks 1012 is symmetrically arranged relative to the axial center of the thin-walled part.

[0069] It should be noted that the side 101 of the part blank has multiple windows 1011, and the windows 1011 need to be machined one by one by rotating the part blank using milling. Therefore, it is necessary to determine the rotation angle of the part blank and the rotating platform connected to it in order to match the machining of the next window 1011 after the machining of adjacent windows 1011 is completed.

[0070] Specifically, a baseline for the thin-walled part is constructed using two symmetrically positioned locating blocks: the center line connecting the centers of a set of symmetrically positioned locating blocks 1012 is used as the machining baseline, with the initial position being when the machining baseline is placed vertically; by determining the angle between the line connecting the center of window 1011 and the part's axis and the machining baseline, the angle α required for the part blank and its connected rotating platform to rotate to the machining baseline position is determined; based on the α of adjacent windows 1011, the rotation angle of the part blank and its connected rotating platform relative to the initial position is determined when machining adjacent windows 1011.

[0071] like Figure 1 As shown, a plurality of spaced first grooves 1013 are provided on the side surface 101 near the first end face 102.

[0072] In practice, the first groove 1013 is obtained by a milling cutter machining from the outside to the inside on the side 101.

[0073] The thin-walled part has thin-walled characteristics. Specifically, the ratio of the wall thickness of the first end face 102, the second end face 103, and the side face 101 to the outer diameter of the thin-walled part is 1:200 to 1000.

[0074] It should be noted that vibration and deformation are mainly affected by the relative values ​​of wall thickness and part diameter. The smaller the relative ratio of wall thickness to part diameter, the more obvious the thin-walled characteristics of the part are, and the machining accuracy will be significantly reduced due to machining vibration and deformation.

[0075] Specifically, in addition to magnesium alloys, thin-walled parts can also be made of carbon steel, stainless steel, titanium alloys, or aluminum alloys.

[0076] On the one hand, the present invention provides a method for processing cylindrical thin-walled parts, such as... Figure 6 As shown, it includes the following steps:

[0077] Step 3: Simultaneously fix the milling die to both ends of the thin-walled part blank after the reference positioning line is marked, and fix the guard plate in the milling die to the outer circumferential side of the thin-walled part blank; the milling machine processing leaves a margin;

[0078] Specifically, the milling mold used for machining the inner side of thin-walled parts is fixed to the outside of the thin-walled part blank, with the hollow annular end face of the thin-walled part blank fixed to the rotary table, and the free end face set near the end of the milling tool; the milling tool performs milling on the side of the thin-walled part blank from the inner side to the outer side.

[0079] When implementing, such as Figure 5 As shown, a milling die is used to fix the part blank on the rotary table 4, so that it can rotate radially around the machine tool working platform 6. One end of the milling die is provided with a first pressure plate 201 that is pressed and connected to the first end face 102, and the other end is provided with a first bottom fixing member 203 that is pressed and connected to the second end face 103. The machining tool 7 penetrates into the interior of the thin-walled part to complete the side 101 from the inside out, and removes the excess material from the window 1011. At this time, the machine tool working platform 6 is a milling machine working platform, and the machining tool 7 is a milling tool.

[0080] It should be noted that the side of the part blank has multiple windows, and the part blank needs to be rotated to process each window one by one. Therefore, it is necessary to determine the rotation angle of the part blank and the rotating platform connected to it when processing adjacent windows.

[0081] Specifically, obtain the line connecting the center of the side window and the axis of the part blank, and further obtain the angle between the line connecting the window center and the axis and the corrected reference positioning line; use this angle to calculate the rotation angle of the part blank and its connected rotary platform when machining adjacent windows.

[0082] During implementation, the initial position is taken as when the machining datum line is placed vertically; by determining the angle between the line connecting the center of the window and the axis of the workpiece blank and the machining datum line, the angle α that the workpiece blank and its connected rotating platform need to rotate to the position of the machining datum line is determined; based on the α of the adjacent windows, the rotation angle of the workpiece blank and its connected rotating platform relative to the initial position is determined when machining the adjacent windows.

[0083] Specifically, on the corrected reference positioning line, two reference holes (not shown in the figure) are distributed relatively from the axis line in the unmachined area of ​​the outer edge of the hollow annular end face of the thin-walled part blank.

[0084] It should be noted that the milling allowance mentioned in this article refers to the fact that the milling process has not reached the size of the formed component, and there is still room for further milling.

[0085] It should be noted that the positioning block is removed after milling, and the corrected datum positioning line needs to be continued to be transferred. Therefore, a datum hole is set as the transfer medium for the datum positioning line.

[0086] Step 4: Two reference holes are set in the unmachined area of ​​the outer edge of the free end face of the milled thin-walled part blank, with respect to the axis; the center point of the reference hole is collinear with the corrected reference positioning line.

[0087] Specifically, the reference hole is the target machining hole for the shaped thin-walled part, and the hole is drilled vertically on the free end face using a machine tool drilling tool.

[0088] Step 5: Stabilize the blank of the thin-walled part after milling.

[0089] Specifically, the thin-walled part blanks that have been milled are subjected to a heating-air cooling-reheating-furnace cooling process to remove residual stress from the turning and milling processes.

[0090] Step 6: Based on the reference hole, perform a second milling process on the thin-walled part blank that has undergone stabilization treatment; the milling die for the second milling process is equipped with a protective plate that is circumferentially fitted and fixed to the outer side of the thin-walled part blank; the second milling process leaves a margin.

[0091] Specifically, the milling mold used for machining the inner side of thin-walled parts is fixed to the outside of the thin-walled part blank, with the hollow annular end face of the thin-walled part blank fixed to the rotary table, and the free end face set near the end of the milling tool; the milling tool performs milling on the side of the thin-walled part blank from the inner side to the outer side.

[0092] When implementing, such as Figure 5 As shown, a milling die is used to fix the part blank on the rotary table 4, so that it can rotate radially around the machine tool working platform 6. One end of the milling die is provided with a first pressure plate 201 that is pressed and connected to the first end face 102, and the other end is provided with a first bottom fixing member 203 that is pressed and connected to the second end face 103. The machining tool 7 penetrates into the interior of the thin-walled part to complete the side 101 from the inside out, and removes the excess material from the window 1011. At this time, the machine tool working platform 6 is a milling machine working platform, and the machining tool 7 is a milling tool.

[0093] Specifically, the straight line connecting the center points of the reference holes is used as the reference positioning line for the second milling machining.

[0094] During implementation, the line connecting the center points of the reference holes is marked with a scribing device and used as the reference positioning line for the second milling machine machining; the line connecting the center of the side window and the axis of the part blank is obtained, and the angle between the line connecting the center of the window and the axis and the reference positioning line for the second milling machine machining is further obtained; the initial position is taken when the reference positioning line is placed vertically; by determining the angle between the line connecting the center of the window and the axis of the part and the machining reference line, the angle α that the part blank and its connected rotary platform need to rotate to the position of the machining reference line is determined; based on α of the adjacent windows, the rotation angle of the part blank and its connected rotary platform relative to the initial position is determined when machining the adjacent windows.

[0095] Step 7: Based on the reference hole, perform a third milling operation on the thin-walled part blank that has completed the second milling operation; the milling die for the third milling operation is equipped with a protective plate that is circumferentially fitted and fixed to the outer side of the side of the thin-walled part blank; the milling operation leaves a margin; the third milling operation processes the window on the side of the thin-walled part blank to the target size.

[0096] Specifically, the milling mold used for machining the inner side of thin-walled parts is fixed to the outside of the thin-walled part blank, with the hollow annular end face of the thin-walled part blank fixed to the rotary table, and the free end face set near the end of the milling tool; the milling tool performs milling on the side of the thin-walled part blank from the inner side to the outer side.

[0097] When implementing, such as Figure 5As shown, a milling die is used to fix the part blank on the rotary table 4, so that it can rotate radially around the machine tool working platform 6. One end of the milling die is provided with a first pressure plate 201 that is pressed and connected to the first end face 102 of the part blank, and the other end is provided with a first bottom fixing member 203 that is pressed and connected to the second end face 103 of the part blank. The machining tool 7 penetrates into the interior of the thin-walled part to complete the side 101 from the inside out, and removes the excess material from the window 1011. At this time, the machine tool working platform 6 is a milling machine working platform, and the machining tool 7 is a milling tool.

[0098] Specifically, the straight line connecting the center points of the reference holes is used as the reference positioning line for the third milling operation.

[0099] During implementation, the line connecting the center points of the reference holes is marked with a scribing device and used as the reference positioning line for the third milling machine machining; the line connecting the center of the side window and the axis of the part blank is obtained, and the angle between the line connecting the center of the window and the axis and the reference positioning line for the third milling machine machining is further obtained; the initial position is taken when the reference positioning line is placed vertically; by determining the angle between the line connecting the center of the window and the axis of the part and the machining reference line, the angle α that the part blank and its connected rotary platform need to rotate to the position of the machining reference line is determined; based on α of the adjacent windows, the rotation angle of the part blank and its connected rotary platform relative to the initial position is determined when machining the adjacent windows.

[0100] Specifically, such as Figure 2 , Figure 3 and Figure 4 As shown: the milling die is fixedly connected to the first end face 102 and the second end face 103 of the thin-walled part; one end of the milling die is provided with a first pressure plate 201 that is pressed and connected to the first end face 102, and the other end is provided with a first bottom fixing member 203 that is pressed and connected to the second end face 103; at the same time, the outer circumferential edge of the first pressure plate 201 and the outer circumferential edge of the first bottom fixing member 203 are fixedly connected by a first tie rod 204 at corresponding positions, and the first bottom fixing member 203 is fixedly connected to the machine tool platform; the first tie rod 204 provides a clamping force along the direction of the first tie rod 204 to realize the pressing and fixing of the thin-walled part on the machine tool platform.

[0101] The milling die 2 has a guard plate 202 on the side 101 of the thin-walled part to limit the radial vibration of the thin-walled part; the guard plate 202 surrounds the side 101 circumferentially and has a first through hole 2022; a first pull rod 204 passes through the first through hole 2022, and the first pull rod 204, which is arranged circumferentially along the side 101, enables the guard plate 202 to surround and fit the side 101 circumferentially, thus limiting the radial outward deformation or vibration of the thin-walled part when the milling cutter processes the inner wall of the side 101.

[0102] It should be noted that the milling cutter processes the side 101 of the thin-walled part from the inside out, applying a radially outward force to the side 101, which can easily cause deformation or chattering of the side 101. When the wall thickness of the blank becomes thinner, the adverse effects of deformation or chattering on machining accuracy will further increase.

[0103] Compared with existing technologies, this invention uses a specially designed milling die to process thin-walled parts and adopts a "roughing-semi-finishing-finishing" processing method, which reduces deformation and mechanical damage caused by accumulated stress in thin-walled materials and improves processing accuracy. Each processing step includes a milling operation. By setting a guard plate on the milling die, this invention improves the rigidity of the side of the thin-walled part blank. The guard plate can provide support in both radial directions during the milling of the thin-walled part blank, thereby reducing vibration and deformation in both radial directions.

[0104] On the other hand, by setting a first pressure plate, a first bottom fixing member, a first tie rod, and a guard plate in the milling mold, the present invention can not only press and fix thin-walled parts, but also greatly reduce the adverse effects of vibration on machining accuracy during side milling; it improves the defects of easy vibration and poor machining accuracy when milling the side of thin-walled parts from the inside to the outside in the prior art.

[0105] In addition, this invention uses laser scanning imaging technology to preliminarily determine the wall thickness of each section of the casting, determine the correction position of the rotation axis centerline, and adjust and coordinate the wall thickness of each processing part based on the correction axis centerline to the machining datum line, so as to make the wall thickness of the part as uniform as possible before processing, so as to ensure that the machining allowance of each surface is uniform and the wall thickness meets the requirements. While ensuring the accuracy of the datum scribing, it greatly reduces the workload of machine tool alignment and zeroing in subsequent processes.

[0106] In addition, by providing a positioning block on the inner side of the cast thin-walled part blank, and using the line connecting the center of the positioning block in the radial plane as a reference, the present invention can greatly reduce the workload of subsequent machine tool alignment and zeroing while meeting the accuracy requirements; furthermore, the positioning block and the rotation axis centerline are used to correct the position and determine the machining reference positioning line; furthermore, a reference hole is set on the machining reference positioning line as the transmission medium of the original reference, which ensures the continuity of the reference and improves the machining accuracy.

[0107] In addition, after the blank is corrected by positioning reference line and axis, the present invention removes the deformation and precision error of the casting process by vertical lathe machining, so that the rotation axis of the blank coincides with the geometric center of its end face, and provides a reference for the next step of machining in combination with the positioning reference line.

[0108] Specifically, step 3 involves milling, obtaining the angle between the line connecting the center of the side window of the part blank and the axis and the corrected reference positioning line, and using this angle to calculate the rotation angle of the part blank and its connected rotary platform when machining adjacent windows. This specifically includes:

[0109] S301: Connect the center of the window to the axis of the workpiece blank in its radial plane. Obtain the angle α between this line and the machining datum line using an angle measuring device. Based on the adjacent order of the windows, number them sequentially as the first window, ..., the nth window, and the corresponding angle α is numbered α1, ..., α2. n ;

[0110] S302: Calculate the difference Δα between any two adjacent windows and the machining baseline, which serves as the rotation angle of the part blank and its connected rotary platform during machining of adjacent windows; where Δα satisfies: Δα=α k -α k-1 , k≤n; k represents the window number, α k Let be the angle between the center of the k-th window and the line connecting the center of the part blank to the machining datum line in its radial plane.

[0111] Specifically, during the processing of adjacent windows, the rotation angle of the part blank and the rotating platform connected to it is adjusted by means of the angle scale on the rotating platform itself.

[0112] Specifically, the milling amount in step 3 is 1mm to 5mm.

[0113] Preferably, the milling amount in step 3 is 2mm to 3mm.

[0114] Specifically, step 4 involves obtaining the reference hole using a machine tool drilling equipment, and inserting a locating pin to correct the position of the reference hole, including:

[0115] S401: A first coordinate axis is set in the vertical horizontal plane, the rotation axis of the machine tool rotary platform is used as the second coordinate axis, and a third coordinate axis is set in the horizontal plane in a direction perpendicular to the first and second coordinate axes to construct a spatial coordinate system;

[0116] S402: Select one of the locating pins of the reference hole as the first locating pin, set a dial indicator on the machine tool spindle to contact the highest point of the side of the first locating pin, and record the dial indicator reading.

[0117] S403: Select the locating pin of another reference hole as the second locating pin, rotate the machine tool rotary platform 180° using its own scale, keep the coordinates of the machine tool spindle on the first and second coordinate axes unchanged, and make contact at the highest point on the side of the second locating pin. Record the dial indicator reading.

[0118] S404: Calibrate the reference hole based on two dial indicator readings;

[0119] If the difference between two dial gauge readings is less than the third threshold δ3, then the reference hole setting is deemed to meet the requirements.

[0120] If the difference between two dial indicator readings is greater than the third threshold δ3, then the original reference hole is enlarged based on the corrected reference positioning line, and matching positioning pins are used to repeat S402-S403 until the difference between two dial indicator readings is less than the third threshold δ3.

[0121] Specifically, the accuracy of the reference hole setting is evaluated by the change in the dial indicator reading η, and η satisfies: η = S max -S min , among which, S max S represents the maximum dial indicator reading from two separate dial indicator readings. min This represents the minimum dial indicator reading between two dial indicator readings.

[0122] Optionally, the third threshold δ3 is set to 0.02 mm.

[0123] It should be noted that the determination of the third threshold δ3 is related to the accuracy of the dial indicator itself. The third threshold δ3 < 0.02 mm, which is outside the accuracy range of the dial indicator.

[0124] Specifically, enlarging the original reference hole based on the corrected reference positioning line includes: repositioning the center of the enlarged reference hole on the corrected reference positioning line and then enlarging the hole; the enlarged diameter of the reference hole should be larger than the original reference hole, and the enlarged reference hole should completely cover the area of ​​the original reference hole, thereby eliminating the error caused by the deviation in the position setting of the original reference hole.

[0125] It should be noted that the distance between the center of the reference hole and the calibrated reference positioning line can be adjusted according to actual needs. Therefore, when taking the dial indicator reading in steps S402-S403, it is not necessary to take the coordinate reading of the third coordinate axis in the direction of the calibrated reference positioning line.

[0126] Specifically, the determination of the highest point on the side of the pin in S402 and S403 includes:

[0127] S411: Set a first coordinate axis in the vertical horizontal plane, take the rotation axis of the machine tool rotary platform as the second coordinate axis, set a third coordinate axis in the horizontal plane in the direction perpendicular to the first and second coordinate axes, and construct a spatial coordinate system with the center of the machine tool rotary platform as the origin;

[0128] S412: Select one of the reference holes and insert a matching locating pin. Set a dial indicator on the machine tool spindle to contact the top area of ​​one side of the locating pin and show a reading. Keep the coordinates of the first and second axes of the machine tool spindle unchanged. Move the machine tool spindle parallel to the third axis while keeping the dial indicator reading non-zero. Record the spatial coordinates when the dial indicator reading is at its minimum as the coordinates of the highest point on one side of the locating pin.

[0129] S413: Using the same method, obtain the coordinates of the highest point on the other end of the positioning pin. Compare the coordinates of the highest points at both ends, and take the larger value of the first coordinate axis as the coordinate of the highest point on the side of the pin.

[0130] It should be noted that the pins are generally selected from smooth and flat cylinders. Due to the limited accuracy of drilling the reference hole, the flatness of the hole is poor, and the positioning pin may not be horizontal after installation, so it cannot be used to further correct the reference hole.

[0131] Furthermore, in order to correct the longitudinal flatness of the reference hole opening, S401 and S402 also include a flatness correction for the reference hole opening:

[0132] S414: Compare the coordinates (x1, y1, z1) and (x2, y2, z2) of the highest points at both ends obtained in steps S412 and S413, and obtain the coordinate differences △x, △y, △z for each coordinate axis; where △x = |x1-x2|, △y = |y1-y2|, △z = |z1-z2|;

[0133] If Δx, Δy, and Δz are all less than the fourth threshold δ4, then the flatness of the opening of the reference hole is deemed to meet the requirements.

[0134] If any of the values ​​of △x, △y, and △z is greater than the fourth threshold δ4, then based on the corrected reference positioning line, the original reference hole is enlarged, and after positioning and installation with a matching positioning pin, S412-S413 is repeated until △x, △y, and △z are all less than the fourth threshold δ4.

[0135] Optionally, the fourth threshold δ4 is related to the machining accuracy of the machine tool.

[0136] Compared with existing technologies, this method uses segmented processing based on different processing areas. The arc surface is divided into sections, and then processing trajectories are planned in each section for processing window by window, instead of fixing the thin-walled part blank. This controls the movement of the tool, reduces tool displacement, and avoids processing vibration caused by excessive tool overhang, thereby ensuring processing accuracy and improving processing efficiency.

[0137] Specifically, the stabilization process described in step 5 further reduces residual stress from the pre-processing process, and includes the following steps:

[0138] S501: Heat treatment at 120±10℃ for 2h~6h, then air-cooled down to room temperature;

[0139] S502: Heat-treat at 120±10℃ for 2h~6h, then cool to room temperature with the furnace.

[0140] The thermal stress generated during the positive temperature-air cooling-positive temperature-furnace cooling process is superimposed on the original residual stress, exceeding the yield strength of the material and causing plastic deformation, thereby reducing the original residual stress and further improving the plasticity and machinability of the cylindrical part material.

[0141] Specifically, step S501 uses air cooling to quickly superimpose the external surface thermal stress with the original residual stress, resulting in plastic deformation; step S502 uses furnace cooling to slowly lower the temperature, which can reduce the thermal stress on the outer and inner surfaces of the part blank caused by air cooling; overall, it achieves the effect of reducing the stress caused by rough machining.

[0142] It should be noted that the first milling operation is a roughing process. Due to the large amount of material removed, the accumulated stress during the machining process is relatively large, so a stabilization treatment is required to remove the accumulated stress. The second and third milling operations have smaller material removal and the workpiece is thinner, so it is not easy for stress to accumulate.

[0143] Specifically, step 6 involves performing a second milling operation. This involves obtaining the angle between the line connecting the center of the side window of the workpiece blank and the axis, and the corrected reference positioning line. Using this angle, the rotation angle of the workpiece blank and its connected rotary platform during the machining of adjacent windows is calculated. This specifically includes:

[0144] S601: Connect the center of the window to the axis of the workpiece blank in its radial plane. Obtain the angle α between this line and the machining datum line using an angle measuring device. Based on the adjacent order of the windows, number them sequentially as the first window, ..., the nth window, and the corresponding angle α is numbered α1, ..., α2. n ;

[0145] S602: Calculate the difference Δα between any two adjacent windows and the machining baseline, which serves as the rotation angle of the part blank and its connected rotary platform during machining of adjacent windows; where Δα satisfies: Δα=α k -α k-1 , k≤n.

[0146] Specifically, during the processing of adjacent windows, the rotation angle of the part blank and the rotating platform connected to it is adjusted by means of the angle scale on the rotating platform itself.

[0147] During implementation, record the angle scale of the rotating platform when the previous window was being processed, and rotate the angle scale of the rotating platform by △α so that the window to be processed is in the processing position of the previous window.

[0148] To improve local heat dissipation, for example, when magnesium alloy is selected as the raw material, a cooling airflow of 0.7MPa to 0.8MPa is provided during the machining of the part blank.

[0149] It should be noted that water or oil-based cutting coolants will react with high-temperature magnesium alloys. Compared with the prior art, the present invention uses a 0.7MPa to 0.8MPa airflow for cooling, which solves the problem of local heat dissipation, and is conducive to further reducing the feed rate and improving machining accuracy and machining safety.

[0150] Step 7, the third milling process, machining the window on the side of the thin-walled part blank to the target size, includes:

[0151] S701: Using the milling die for machining the inner side wall of a thin-walled part, the hollow annular end face of the thin-walled part blank is fixed on the rotary table, with the free end face positioned close to the end of the machining tool.

[0152] S702: Connect the center of the window to the axis of the workpiece blank in its radial plane. Obtain the angle α between this line and the machining datum line using an angle measuring device. Based on the adjacent order of the windows, number them sequentially as the first window, ..., the nth window, and the corresponding angle α is numbered α1, ..., α2. n ;

[0153] S703: Calculate the difference Δα between any two adjacent windows and the machining datum line, which serves as the rotation angle of the part blank and its connected rotary platform during machining of adjacent windows; where Δα satisfies: Δα=α k -α k-1 , k≤n; k represents the window number, α k Let be the angle between the center of the k-th window and the line connecting the center of the part blank to the machining datum line in its radial plane.

[0154] S704: With the vertical state of the machining datum line as the initial position, set the machining area of ​​the milling tool to be in the horizontal plane below the axis, rotate the rotary platform by α1 degrees so that the line connecting the first window and the axis is in the initial position, the machining plane of the first window is in the machining area of ​​the milling tool, and mill the first window to the target size;

[0155] S705: Rotate the rotary platform by α2-α1 degrees so that the machining plane of the second window is in the machining area of ​​the milling tool, and mill the second window to the target size;

[0156] S706: Rotate the rotating platform by α3-α2, ..., αn -α n-1 The degree is adjusted so that the machining plane of the third window, ..., the nth window is in the machining area of ​​the milling cutter, and the third window, ..., the nth window is milled to the target size; the third milling machining of the thin-walled part blank is completed.

[0157] Specifically, S701, which describes fixing the free end face of the thin-walled part blank to the rotary table, includes:

[0158] S7011: The first pressure plate of the milling die is pressed and connected to the first end face, and the first bottom fixing part is pressed and connected to the second end face;

[0159] S7012: The outer circumferential edge of the first pressure plate is fixedly connected to the corresponding position of the outer circumferential edge of the first bottom fixing member by the first tie rod, and the first bottom fixing member is fixedly connected to the machine tool platform.

[0160] S7013: The first tie rod is passed through the first through hole provided around the side, and the first tie rod provided around the side achieves the circumferential wrapping of the guard plate to fit the side.

[0161] Compared with the prior art, the present invention, by setting a first pressure plate, a first bottom fixing member, a first tie rod, and a guard plate in the milling mold, can not only press and fix thin-walled parts, but also greatly reduce the adverse effects of vibration on machining accuracy during side machining; thus improving the defects of easy vibration and poor machining accuracy in the side machining of thin-walled parts in the prior art.

[0162] To improve local heat dissipation, for example, when magnesium alloy is selected as the raw material, a cooling airflow of 0.8MPa to 1.0MPa is provided during the machining of the part blank.

[0163] It should be noted that water or oil-based cutting coolants will react with high-temperature magnesium alloys. Compared with the prior art, the present invention uses a wind-cooled airflow of 0.8MPa to 1.0MPa for cooling, which increases the air pressure, helps to solve the problem of local heat dissipation, and can reduce the feed rate, improve machining accuracy and machining safety.

[0164] The third milling process also includes a step of using measuring equipment to check the wall thickness at various points on the side.

[0165] The second through hole is radially provided on the guard plate so that the side wall thickness can still be measured during milling. The through hole also enables ventilation and heat dissipation, which solves the problems of difficult thickness control and poor heat dissipation in the existing technology for machining the side walls of thin-walled parts.

[0166] Specifically, such as Figure 3 , Figure 4As shown, the side of the protective plate 202 is provided with multiple second through holes 2021. Through the second through holes 2021, external equipment can be connected to detect the wall thickness at various points on the side 101.

[0167] During implementation, ultrasonic, laser, or X-ray equipment is used to detect the wall thickness at each point on the side 101.

[0168] The processing method for the thin-walled magnesium alloy parts further includes a step of inspecting the cracks and damage of the thin-walled parts after step 8. Specifically, the inspection is carried out using the radiographic testing method of GJ / B 1187A-2001, and the acceptance standard is the requirements for Class I castings in QJ 20708, "Rare Earth Heat-Resistant Cast Magnesium Alloys and Casting Specifications". The selected method is X-ray fluorescence flaw detection.

[0169] The processing method for the thin-walled magnesium alloy parts includes a micro-arc oxidation treatment step on the surface of the thin-walled magnesium alloy parts after the step of inspecting the cracks and damage of the thin-walled parts. Specifically, a high-voltage electric arc is used to generate a magnesium oxide layer with good heat resistance and hardness on the surface of the magnesium alloy, thereby improving the oxidation resistance, surface hardness and wear resistance of the magnesium alloy.

[0170] On the other hand, in order to more conveniently obtain a more accurate machining reference, the machining method of the present invention further includes the following before step 3:

[0171] Step 1: Connect the center of the positioning blocks that are symmetrical about the axis as the reference positioning line of the hollow annular end face. Obtain the fitting image of the thin-walled part blank based on laser scanning fitting imaging. Correct the reference positioning line based on the fitting image of the thin-walled part blank. The thin-walled part blank has a side surface, an unobstructed free end face and a hollow annular end face. The inner surface of the side surface is provided with at least two positioning blocks that are symmetrical about the axis.

[0172] Specifically, laser scanning fitting imaging analysis software is used to synthesize a fitted image of the thin-walled part blank from the information of the cast part blank obtained by laser scanning; based on the fitted image of the part blank and the theoretical image of the thin-walled part blank, the deviation between the fitted image and the theoretical image of the thin-walled part blank at each radial section is obtained; and the deviation of each radial section is judged.

[0173] If the deviation of each radial section is less than or equal to the first threshold δ1, no adjustment is made and the reference positioning line is corrected.

[0174] If the deviation of each radial section is greater than the first threshold δ1, adjust the position of the axis of the theoretical image of the thin-walled part blank until the deviation of each radial section is less than or equal to the first threshold δ1, and record the position change value Δ(x, y, z) of the axis of the axis in the spatial coordinate system; in the same spatial coordinate system, obtain the coordinates of the axis of the corrected part blank by changing the axis of the axis of the part blank according to Δ(x, y, z); connect the center of the positioning block and the axis of the corrected part blank in the radial plane, and use the line connecting the two as the corrected reference positioning line.

[0175] In practice, the thin-walled part blank is a hollow thin-walled part blank with two end faces obtained by casting. During processing, the end faces are fixed to the rotating platform and can rotate freely around the axis; the two end faces are set parallel to the radial plane.

[0176] During implementation, the positioning blocks are cast together with the thin-walled part blank in the mold. They can be regular in shape and easy to find the center, such as a cuboid. Multiple sets of positioning blocks can be set, with each pair symmetrical to the central axis.

[0177] It should be noted that the positioning block's setting accuracy on the thin-walled part blank meets the initial alignment requirements, allowing the machining personnel to roughly judge the baseline position and easily adjust the rotation angle of the thin-walled part blank, so that the starting machining position of the thin-walled part blank is close to the machining area.

[0178] It should be noted that the thin-walled part blanks obtained by casting have uneven side wall thickness, which is not an ideal state of uniform wall thickness. If the original design axis is used for machining, products with uneven wall thickness will inevitably be obtained. Therefore, it is necessary to correct the position of the axis so that the thin-walled part blank can be rotated and machined with this position as the axis to obtain products with uniform wall thickness.

[0179] In practice, the spatial coordinate system often uses the axial direction of the thin-walled part as one coordinate axis and the radial direction as the plane containing the other two coordinate axes. The laser scanning fitting imaging analysis software can simultaneously display the fitted image of the part blank and the theoretical image of the thin-walled part blank, calculate the non-overlapping areas of the two, and assign different color labels. Through the color labels, the deviation of each radial plane of the thin-walled part can be intuitively obtained. By adjusting the position of the axis centerline of the fitted image of the part blank, the color labels of each radial plane deviation change, and then the position with the smallest relative radial plane deviation can be selected. This position is used as the corrected position of the axis centerline of the part blank, and the position change value Δ(x, y, z) is calculated. In the spatial coordinate system where the part blank is fixed during processing, the axis centerline is changed according to Δ(x, y, z) to obtain the corrected position of the axis centerline of the part blank. Any positioning block in a set of positioning blocks that are symmetrical about the axis centerline is selected, and the center of the positioning block and the corrected axis centerline of the part blank are connected in the radial plane. The line connecting the two is used as the corrected reference positioning line, thus completing the correction of the reference positioning line.

[0180] Specifically, the method for obtaining the fitted image of the thin-walled part blank based on laser scanning fitting imaging in step 1 is as follows: using sensors densely distributed on the inner and outer surfaces of the thin-walled part blank as data sampling points, using laser scanning to obtain the coordinates of the sensors in the spatial coordinate system, and fitting a three-dimensional image of the thin-walled part blank based on the sensor spatial coordinate information.

[0181] Specifically, step 1, which involves correcting the reference positioning lines based on the fitted image of the thin-walled part blank, includes:

[0182] S101: Using laser scanning fitting imaging software, the centerline of the fitted image of the part blank and the theoretical image of the thin-walled part blank are coincident. The thickness of each region of the radial section of the part blank is compared, the deviation is automatically obtained, and the deviation is marked with color according to the size of the deviation.

[0183] S102: If the deviation of each radial section is less than or equal to 0.02mm, no adjustment is required, and the reference positioning line is calibrated.

[0184] If the deviation of each radial section is greater than the threshold of 0.02mm, adjust the position of the axis of the theoretical image of the thin-walled part blank until the deviation of each radial section is less than or equal to the first threshold δ1, and record the position change value of the axis of the axis in the spatial coordinate system Δ(x, y, z).

[0185] S103: Construct the same spatial coordinate system as the fitted image of the part blank and the theoretical image of the thin-walled part blank. In this coordinate system, obtain the coordinates of the corrected axis of the part blank by changing the axis of the part blank according to △(x, y, z).

[0186] S104: In the radial plane where the center of the positioning block of the part blank is located, connect the center of any positioning block and the axis of the corrected part blank, and use the line connecting the two as the corrected reference positioning line to complete the reference positioning line correction.

[0187] Preferably, the first threshold δ1 is 0.02 mm.

[0188] It should be noted that the determination of the first threshold δ1 is related to the accuracy of the dial indicator itself. The first threshold δ1 < 0.02 mm, which is outside the accuracy range of the dial indicator.

[0189] To improve the poor casting accuracy and susceptibility to eccentricity defects in thin-walled parts, the processing method of this invention further includes:

[0190] Step 2: Perform vertical machining on the outer side of the thin-walled part blank after the reference positioning line has been corrected to obtain a thin-walled part blank with uniform wall thickness; the vertical machining leaves a margin.

[0191] Specifically, a three-jaw chuck is used to fix the thin-walled part blank from inside, and the free end face of the thin-walled part blank is fixed to the rotary table. The hollow annular end face is set near the end of the machining tool. The machining tool performs machining on the two end faces and the outer circle of the side of the thin-walled part blank from the hollow annular end face to the free end face.

[0192] When implementing, such as Figure 7 As shown, the workpiece blank is fixed on the rotary table 4 using a three-jaw chuck 5, so that it can rotate radially around the machine tool work platform 6. The machining tool 7 completes the outer circle machining of the side 101, the second end face 103 and the first end face 102 of the thin-walled part. At this time, the machine tool work platform 6 is a vertical lathe work platform and the machining tool 7 is a vertical lathe machining tool.

[0193] It should be noted that the three-jaw chuck is a commonly used internal fixing fixture on lathes. It has three jaws, and the distance between the three jaws can be adjusted to clamp and fix hollow parts of different inner diameters from inside the hollow part.

[0194] It should be noted that the allowance for vertical machining mentioned in this article refers to the fact that the vertical machining has not been completed to the size of the formed component, and there is still room for further vertical machining.

[0195] It should be noted that the axis of rotation for machining thin-walled part blanks after completing the datum positioning line correction is the corrected position. Rotating the machining along this axis results in a more uniform wall thickness on the side of the thin-walled part blank. After vertical machining, the cross-sectional shape of the part blank changes compared to the original thin-walled part blank, the wall thickness is uniform, and the center of the part blank cross-section is located on the corrected axis.

[0196] Specifically, the vertical lathe machining described in step 2 includes the following steps:

[0197] S201: Select 1 / 4 to 1 / 2 of the machining amount of the fixed thin-walled part blank and perform trial machining to obtain a trial machining blank sample;

[0198] S202: Inspect the eccentricity of the machined blank sample rotating about the axis of the calibrated part blank;

[0199] S203: Determine the degree of eccentricity;

[0200] If the eccentricity is less than the second threshold δ2, then machining is performed;

[0201] If the eccentricity is greater than the second threshold δ2, repeat S101-S104 to correct the axis of the part blank again until the eccentricity is less than the second threshold δ2.

[0202] Specifically, the eccentricity described in S202 is checked by a dial indicator, including the following steps: fixing the fixed end of the dial indicator to the machine tool platform, and contacting the test end with the side of the part blank until a reading is obtained; recording the change of the dial indicator reading during the part blank's rotation of one revolution.

[0203] Specifically, the eccentricity is evaluated by the change η in the dial indicator reading, and η satisfies: η = S max -S min , among which, S max S represents the maximum value of the dial indicator pointer reading. min This represents the minimum reading of the dial indicator.

[0204] Optionally, the second threshold δ2 is set to 0.02 mm.

[0205] It should be noted that the determination of the second threshold δ2 is related to the accuracy of the dial indicator itself. The second threshold δ2 < 0.02 mm, which is outside the accuracy range of the dial indicator.

[0206] To meet the requirements of magnesium alloy machining, the feed rate of the workpiece blank during the first machining operation is 0.4 mm / r to 0.6 mm / r. If it is lower than 0.4 mm / r, local overheating is likely to occur, leading to deformation or even spontaneous combustion of the magnesium alloy; if it is higher than 0.6 mm / r, it is difficult to meet the accuracy requirements.

[0207] To improve local heat dissipation, a cooling airflow of 0.6MPa to 0.8MPa is provided during the machining of the part blank.

[0208] It should be noted that water or oil-based cutting coolants will react with high-temperature magnesium alloys. Compared with the prior art, this invention uses a 0.6MPa to 0.8MPa airflow for cooling, which solves the problem of local heat dissipation and is conducive to further reducing the feed rate and improving machining accuracy and machining safety.

[0209] To reduce deformation during machining, the cutting depth of the workpiece blank should be 0.5 to 2. If the cutting depth of the workpiece blank is greater than 2, deformation is likely to occur when it is fixed by a common three-jaw chuck.

[0210] Specifically, the machining amount of the vertical lathe in step 2 is 2-4 mm.

[0211] Preferably, the machining allowance for the vertical lathe machining in step 2 is 3mm.

[0212] On the other hand, the present invention discloses a machining mold for a cylindrical thin-walled part, including a milling mold for machining the side of the thin-walled part and a three-jaw chuck for vertical lathe machining. The milling mold is fixedly connected to the first end face 102 and the second end face 103 of the thin-walled part, so that the thin-walled part is fixed to the milling mold.

[0213] Specifically, a three-jaw chuck is used to fix the thin-walled part blank from inside, and the free end face of the thin-walled part blank is fixed to the rotary table. The hollow annular end face is set near the end of the machining tool. The machining tool performs machining on the two end faces and the outer circle of the side of the thin-walled part blank from the hollow annular end face to the free end face.

[0214] When implementing, such as Figure 7 As shown, the workpiece blank is fixed on the rotary table 4 using a three-jaw chuck 5, so that it can rotate radially around the machine tool work platform 6. The machining tool 7 completes the outer circle machining of the side 101, the second end face 103 and the first end face 102 of the thin-walled part. At this time, the machine tool work platform 6 is a vertical lathe work platform and the machining tool 7 is a vertical lathe machining tool.

[0215] It should be noted that the three-jaw chuck is a commonly used internal fixing fixture on lathes. It has three jaws, and the distance between the three jaws can be adjusted to clamp and fix hollow parts of different inner diameters from inside the hollow part.

[0216] Specifically, such as Figure 3 , Figure 4 and Figure 5 As shown: One end of the milling die is provided with a first pressure plate 201 that is pressed and connected to the first end face 102, and the other end is provided with a first bottom fixing member 203 that is pressed and connected to the second end face 103.

[0217] Specifically, the first pressure plate 201 is a hollow ring structure, and the milling cutter enters the thin-walled part from the first end face 102 to mill inside the thin-walled part or to mill the outside of the thin-walled part.

[0218] Meanwhile, the milling die is also provided with a first tie rod 204; the outer circumferential edge of the first pressure plate 201 and the outer circumferential edge of the first bottom fixing member 203 are fixedly connected by the first tie rod 204, and the first bottom fixing member 203 is fixedly connected to the machine tool platform; the first tie rod 204 provides a clamping force along the direction of the first tie rod 204 to realize the pressing and fixing of thin-walled parts on the machine tool platform.

[0219] Multiple first tie rods 204 are arranged circumferentially along the side 101. A milling die has a guard plate 202 on the side 101 of the thin-walled part to limit radial vibration of the part. The guard plate 202 circumferentially surrounds the side 101 and has multiple axially arranged first through holes 2022. Each first tie rod 204 corresponds to one of the first through holes 2022. The first tie rods 204 pass through the first through holes 2022. The first tie rods 204 arranged circumferentially along the side 101 radially fix the guard plate 202. Simultaneously, after the guard plate 202 circumferentially surrounds and adheres to the side 101, a sufficiently large static friction force is generated, achieving axial fixation of the guard plate 202, thus securing the guard plate 202. When the milling cutter processes the inner wall of the side 101, the guard plate 202 can limit the radial outward deformation or vibration of the thin-walled part.

[0220] It should be noted that the milling machine tool processes the side 101 of the thin-walled part step by step from the inside to the outside of the thin-walled part. Therefore, the radial outward force applied to the side 101 can easily cause deformation or chattering of the side 101. When the wall thickness of the blank is thinned, the adverse effects of deformation or chattering on the machining accuracy will be further increased.

[0221] Compared with the prior art, the present invention, by setting a first pressure plate 201, a first bottom fixing member 203, a first tie rod 204, and a guard plate 202 in the milling mold, can not only press and fix thin-walled parts, but also greatly reduce the adverse effects of vibration on machining accuracy during side machining; thus improving the defects of easy vibration and poor machining accuracy in the side machining of thin-walled parts in the prior art.

[0222] Specifically, such as Figure 4 , Figure 5 As shown, the first end face 102 of the thin-walled part is pressed and connected to the first pressure plate 201; the second end face 103 is pressed and connected to the first bottom fixing member 203; the two ends of the first pull rod 204 are respectively fixedly connected to the circumferential edges of the first pressure plate 201 and the first bottom fixing member 203; the first pull rod 204 is arranged along the circumferential edges of the first pressure plate 201 and the first bottom fixing member 203, and passes through the first through hole 2022, so that the guard plate 202 is radially fixed and is circumferentially pressed and connected to the side 101; the pressed guard plate 202 and the side 101 generate sufficient static friction force to achieve axial fixation of the guard plate 202 and the side 101.

[0223] Specifically, the side of the guard plate 202 is also provided with a plurality of radially arranged second through holes 2021. The outer side of the thin-walled part is connected to the outside through the second through holes. The second through holes are used for ventilation and heat dissipation of the side of the blank when the external equipment detects the wall thickness of the side 101 and processes it.

[0224] Compared with the prior art, the present invention enables the sidewall thickness to be measured during milling by setting a second through hole, and realizes ventilation and heat dissipation through the through hole, thus solving the problems of difficult thickness control and poor heat dissipation in the sidewall machining of thin-walled parts in the prior art.

[0225] It should be noted that heat dissipation is always a critical issue in the machining of thin-walled parts, especially magnesium alloy parts. Excessive heat accumulation can cause magnesium alloys to soften, deform, or even burn. Magnesium alloys are among the few metals that can react simultaneously with nitrogen and oxygen in the air, making temperature control particularly important during machining.

[0226] The guard plate consists of guard plate units spliced ​​along the axial direction of the thin-walled part.

[0227] Preferably, there are two guard plate units, which are spliced ​​together along the axial direction of the thin-walled part to form guard plate 202; the guard plate 202 has an adjustable connection structure 205 at the connection of the two guard plate units, so that the guard plate 202 can match the blanks of thin-walled parts with different outer diameters, and adjust the degree of pressing between the guard plate 202 and the side 101; when the pressing force is large enough, the guard plate 202 and the side 101 generate a sufficiently large static friction force to achieve axial fixation of the guard plate 202.

[0228] In order to process the first groove 1013 on the side 101, the height of the guard plate 202 is lower than the axial height of the thin-walled part blank, and an axial gap is provided between the guard plate 202 and the first pressure plate 201.

[0229] Specifically, the milling cutter processes the first groove 1013 from the outside to the inside through the gap between the guard plate 202 and the first pressure plate 201.

[0230] Preferably, the wall thickness of the guard plate 202 is greater than the wall thickness of the thin-walled part blank.

[0231] It should be noted that the guard plate 202 is radially fixed by the first tie rod 204 and is circumferentially pressed against the side 101. At the same time, the wall thickness of the guard plate 202 is much greater than that of the thin-walled part blank, which improves the rigidity of the side of the thin-walled part blank. When the milling cutter processes the first groove 1013, the guard plate 202 provides circumferential support force to the side 101. This support force is opposite to the direction of the force applied by the milling cutter, thus making the thin-walled part blank stable and less prone to vibration or deformation from the outside to the inside.

[0232] On the one hand, the side of the guard plate 202 and the arched structure of the guard plate 202 can effectively disperse the force applied by the milling tool; on the other hand, the guard plate 202 provides circumferential support to the side 101, so that the guard plate 202 applies force evenly at each point of contact with the side 101, thus preventing deformation of the side of the thin-walled part blank caused by local stress concentration.

[0233] Compared with existing technologies, the protective plate 202, which surrounds and fits the side of the thin-walled part blank, can provide support in both radial directions during the milling of the side of the thin-walled part blank, thereby reducing vibration and deformation in both radial directions.

[0234] Specifically, the first pull rod is detachably and fixedly connected to the first pressure plate and the first bottom fixing component.

[0235] Preferably, the connection area between the first pull rod and the first pressure plate and the first bottom fixing member is provided with threads, and the first pull rod is fixedly connected to the first pressure plate and the first bottom fixing member by means of a nut that matches the threads.

[0236] Preferably, the first tie rod is symmetrically arranged relative to the axial center of the thin-walled part, so as to provide uniform pressure to the thin-walled part in the radial direction.

[0237] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for machining cylindrical thin-walled parts, characterized in that, include: The center of the positioning blocks symmetrical about the axis is used as the reference positioning line of the hollow annular end face. The fitting image of the thin-walled part blank is obtained based on laser scanning fitting imaging, and the reference positioning line is corrected based on the fitting image of the thin-walled part blank. The thin-walled part blank has a side surface, an unobstructed free end face and a hollow annular end face. The inner surface of the side surface is provided with at least two positioning blocks symmetrical about the axis. Laser scanning fitting imaging analysis software is used to synthesize a fitted image of the thin-walled part blank from the information of the cast part blank obtained by laser scanning; based on the fitted image of the part blank and the theoretical image of the thin-walled part blank, the deviation between the fitted image and the theoretical image of the thin-walled part blank at each radial section is obtained; the deviation of each radial section is judged. If the deviation of each radial section is less than or equal to the first threshold δ1, no adjustment is made and the reference positioning line is corrected. If the deviation of each radial section is greater than the first threshold δ1, adjust the position of the axis of the theoretical image of the thin-walled part blank until the deviation of each radial section is less than or equal to the first threshold δ1, and record the position change value Δ(x, y, z) of the axis of the axis in the spatial coordinate system; in the same spatial coordinate system, obtain the coordinates of the axis of the corrected part blank by changing the axis of the axis of the part blank according to Δ(x, y, z); connect the center of the positioning block and the axis of the corrected part blank in the radial plane, and use the line connecting the two as the corrected reference positioning line; The outer side of the thin-walled part blank after the reference positioning line has been corrected is machined by a vertical lathe to obtain a thin-walled part blank with uniform wall thickness; the vertical lathe machining leaves a margin. The milling die is simultaneously fixedly connected to both ends of the thin-walled part blank after the reference positioning line is scribing, and the guard plate in the milling die is circumferentially attached to the outer side of the thin-walled part blank; milling is then performed, with the milling process leaving a margin. Two reference holes are set in the unmachined area of ​​the outer edge of the free end face of the milled thin-walled part blank, with respect to the axis; the center point of the reference hole is collinear with the reference positioning line of the corrected thin-walled part blank. The thin-walled part blank that has completed milling is stabilized; based on the reference hole, the stabilized thin-walled part blank is subjected to a second milling process using the milling die; the second milling process leaves a allowance; Based on the reference hole, the thin-walled part blank that has completed the second milling process is subjected to a third milling process using the milling die; the third milling process processes the window on the side of the thin-walled part blank to the target size; The stabilization process further reduces residual stress from the pre-processing stage, and includes the following steps: S501: Heat treatment at 120±10℃ for 2h~6h, then air-cooled down to room temperature; S502: Heat-treat at 120±10℃ for 2h~6h, then cool to room temperature with the furnace.

2. The processing method according to claim 1, characterized in that, The milling die has a first pressure plate at one end that is pressed and connected to the first end face of the cylindrical thin-walled part, and a first bottom fixing member at the other end that is pressed and connected to the second end face of the cylindrical thin-walled part; the milling die also has a first pull rod that connects the first pressure plate and the first bottom fixing member.

3. The processing method according to claim 2, characterized in that, Multiple first tie rods are arranged circumferentially along the side. The milling die has a guard plate on the side of the thin-walled part to limit the radial vibration of the thin-walled part. The guard plate surrounds the side circumferentially and has an axially arranged first through hole. The first through hole corresponds to the first tie rod. The first tie rod passes through the first through hole, so that the guard plate is radially fixed. At the same time, after the guard plate is circumferentially attached to the side, it generates a sufficiently large static friction force to achieve axial fixation of the guard plate. The guard plate is circumferentially attached to the side to limit the radial outward deformation or vibration of the thin-walled part.

4. The processing method according to claim 1, characterized in that, The reference hole is obtained using a machine tool drilling equipment, and the position of the reference hole is corrected by inserting a positioning pin.

5. The processing method according to claim 4, characterized in that, The insertion of the positioning pin to correct the position of the reference hole includes: S401: A first coordinate axis is set in the vertical horizontal plane, the rotation axis of the machine tool rotary platform is used as the second coordinate axis, and a third coordinate axis is set in the horizontal plane in a direction perpendicular to the first and second coordinate axes to construct a spatial coordinate system; S402: Select one of the locating pins of the reference hole as the first locating pin, set a dial indicator on the machine tool spindle to contact the highest point of the side of the first locating pin, and record the dial indicator reading. S403: Select another locating pin from the reference hole as the second locating pin, rotate the machine tool rotary platform 180° using its own scale, keep the coordinates of the machine tool spindle on the first and second coordinate axes unchanged, and make contact at the highest point on the side of the second locating pin. Record the dial indicator reading. S404: Calibrate the reference hole based on two dial indicator readings; If the difference between two dial gauge readings is less than the third threshold δ3, then the reference hole setting is deemed to meet the requirements. If the difference between two dial indicator readings is greater than the third threshold δ3, then the original reference hole is enlarged based on the corrected reference positioning line, and matching positioning pins are used to repeat S402-S403 until the difference between two dial indicator readings is less than the third threshold δ3.

6. The processing method according to claim 5, characterized in that, The determination of the highest point on the side of the pin in S402 and S403 includes: S411: Set a first coordinate axis in the vertical horizontal plane, take the rotation axis of the machine tool rotary platform as the second coordinate axis, set a third coordinate axis in the horizontal plane in the direction perpendicular to the first and second coordinate axes, and construct a spatial coordinate system with the center of the machine tool rotary platform as the origin; S412: Select one of the reference holes and insert a matching locating pin. Set a dial indicator on the machine tool spindle to contact the top area of ​​one side of the locating pin and show a reading. Keep the coordinates of the first and second axes of the machine tool spindle unchanged. Move the machine tool spindle parallel to the third axis while keeping the dial indicator reading non-zero. Record the spatial coordinates when the dial indicator reading is at its minimum as the coordinates of the highest point on one side of the locating pin. S413: Using the same method, obtain the coordinates of the highest point on the other end of the positioning pin. Compare the coordinates of the highest points at both ends, and take the larger value of the first coordinate axis as the coordinate of the highest point on the side of the pin.

7. The processing method according to claim 6, characterized in that, The process between S401 and S402 also includes correction for the flatness of the reference hole opening: Compare the coordinates (x1, y1, z1) and (x2, y2, z2) of the highest points at both ends obtained in steps S412 and S413, and obtain the coordinate differences △x, △y, △z for each axis; where △x = |x1 - x2|, △y = |y1 - y2|, △z = |z1 - z2|. If Δx, Δy, and Δz are all less than the fourth threshold δ4, then the flatness of the opening of the reference hole is deemed to meet the requirements. If any of the values ​​of △x, △y, and △z is greater than the fourth threshold δ4, then based on the corrected reference positioning line, the original reference hole is enlarged, and after positioning and installation with a matching positioning pin, S322-S323 is repeated until △x, △y, and △z are all less than the fourth threshold δ4.

8. The processing method according to claim 7, characterized in that, The third milling process machining the window on the side of the thin-walled part blank to the target size includes: S701: Using the milling die for machining the inner side wall of a thin-walled part, the hollow annular end face of the thin-walled part blank is fixed on the rotary table, with the free end face positioned close to the end of the machining tool. S702: Connect the center of the window to the axis of the workpiece blank in its radial plane. Obtain the angle α between this line and the machining datum line using an angle measuring device. Based on the adjacent order of the windows, number them sequentially as the first window, ..., the nth window, and the corresponding angle α is numbered α1, ..., α n ; S703: Calculate the difference Δα between any two adjacent windows and the machining datum line, which serves as the rotation angle of the part blank and its connected rotary platform during machining of adjacent windows; where Δα satisfies: Δα = α k -α k-1 k≤n; k represents the window number, α k The angle between the center of the kth window and the line connecting the center of the part blank axis in its radial plane and the machining datum line; S704: With the vertical state of the machining datum line as the initial position, set the machining area of ​​the milling tool to be in the horizontal plane below the axis, rotate the rotary platform by α1 degrees so that the line connecting the first window and the axis is in the initial position, the machining plane of the first window is in the machining area of ​​the milling tool, and mill the first window to the target size; S705: Rotate the rotary platform by α2-α1 degrees so that the machining plane of the second window is in the machining area of ​​the milling tool, and mill the second window to the target size; S706: Rotate the rotating platform by α3-α2, ..., α n -α n-1 The degree is adjusted so that the machining plane of the third window, ..., the nth window is in the machining area of ​​the milling cutter, and the third window, ..., the nth window is milled to the target size; the third milling machining of the thin-walled part blank is completed.

9. A machining mold for cylindrical thin-walled parts, characterized in that, The milling die includes a protective plate circumferentially fitted on the outer side of the thin-walled part blank, for use in the processing method according to any one of claims 1-8.

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