Machining method for vertically milling large-diameter inner hole

Abstract

A machining system for vertically milling a large-diameter inner hole comprises a cutter bar, a bolt type coupler, a sleeve type cutter tower and a special milling cutter. The machining method for vertically milling the large-diameter inner hole by using the machining system comprises the following steps of: clamping a blank; the axis of the special milling cutter is on the H surface; during machining, the special milling cutter moves in the radial direction of the H face, when special conditions are met, the special milling cutter clockwise deflects by a given angle theta around the axis of an inner hole of the workpiece to be machined, and then the special milling cutter horizontally moves by a distance ld along the diameter of the workpiece according to the given cutting depth ap; and the special milling cutter is axially fed towards the direction of the chuck, and the linkage of the axial movement of the special milling cutter and the rotation of the workpiece to be machined is realized. According to the special milling cutter, the angle deflection of the cutter can be flexibly realized, and the machined surface is easily protected; according to the machining method, milling machining is adopted, the chip shape is good, the tool durability is high, the size precision and shape precision are high, the machining efficiency is high, and the comprehensive technical effect is good.

Description

Technical Field

[0001] The invention relates to a method for milling an inner hole, in particular to a method for milling the inner hole of a large-diameter pipe fitting by using a vertical special milling cutter system, and belongs to the technical field of mechanical processing. Background Art

[0002] The cutting process of the inner hole of large diameter pipe fittings (inner hole diameter greater than 500mm) is currently mainly realized by the trajectory method, usually on a large horizontal lathe or boring machine, using turning or boring methods to complete the inner hole processing. When using this method to process large diameter inner holes, the chip shape is difficult to control, and it is easy to produce continuous strip chips, making it difficult to achieve automatic chip removal; the radial cutting force is large, and the tool and workpiece will produce large radial cutting deformation, which increases the difficulty of ensuring the radial dimensional accuracy of the inner hole.

[0003] At present, the announcement numbers of the patents in the existing related technologies are Chinese invention patents such as CN118123056A, CN103949851A, CN208696405U, CN205660208U, CN217964813U, CN113290262A, and CN108994352B.

[0004] The above patents introduce that the tools for machining large diameter inner holes are turning tools and boring tools, but both turning tools and boring tools are single-edged tools with short tool life, and often require tool change midway, which reduces cutting efficiency. In summary, turning or boring the inner holes of large diameter pipe fittings has low cutting efficiency and is difficult to guarantee quality, which greatly increases the proportion of processing costs in the manufacturing cost of such large pipe fittings. Summary of the invention

[0005] In view of the problems that existing traditional processing technologies are difficult to automatically remove chips, the radial size accuracy of the inner hole is difficult to achieve, and the cutting efficiency is low, the present invention proposes a processing system for vertical milling of large-diameter inner holes with excellent technical effects, and a processing method for vertical milling of large-diameter inner holes using the processing system for vertical milling of large-diameter inner holes.

[0006] The vertical milling large diameter inner hole processing system meets the following requirements:

[0007] The special milling cutter 1 and the processing system used in the vertical milling method of large-diameter inner holes meet the following requirements:

[0008] The special milling cutter system used in the vertical milling method for large-diameter inner holes specifically comprises a cutter bar 4, a bolt-type connector 3, a sleeve-type turret 2, and a special milling cutter 1; wherein:

[0009] The special milling cutter 1 is composed of a square shoulder milling cutter 1a and a sleeve-type special milling cutter handle 1b; the rotation axis of the square shoulder milling cutter 1a is perpendicular to the rotation axis of the workpiece; the rear part of the sleeve-type special milling cutter handle 1b is a hollow tubular structure;

[0010] The sleeve-type turret 2 is a cubic structure, and the sleeve-type turret 2 can be arranged in a rectangular parallelepiped cavity in the bolt-type coupler 3 through the front side of the bolt-type coupler 3; a groove 22 is provided on at least one of the four side surfaces of the sleeve-type turret 2 that are perpendicular to the front side surface thereof; a boss 21 is provided on the front side surface of the sleeve-type turret 2; the boss 21 is fixedly assembled with the hollow tubular structure at the rear of the sleeve-type special milling cutter handle 1b as a whole;

[0011] The bolt-type connector 3 is in the shape of a rectangular parallelepiped, and a rectangular parallelepiped cavity is provided therein. A square hole 31 is provided on the front side thereof, which is convenient for inserting the sleeve-type turret 2 and communicating with the rectangular parallelepiped cavity inside the bolt-type connector 3; at least one protrusion 311 perpendicular to the axis of the square shoulder milling cutter 1a is provided in the rectangular parallelepiped cavity inside the bolt-type connector 3; the protrusion 311 cooperates with the sleeve-type turret groove 22 to facilitate fixing the sleeve-type turret 2;

[0012] A threaded protrusion 32 is provided on one of the side surfaces of the bolt-type connector 3 parallel to the axis of the square shoulder milling cutter 1a. The threaded protrusion 32 is coaxial with the cutter bar 4 and the two are fixedly connected as one body.

[0013] The tool bar 4 is arranged on the X-axial support 6 through the spindle motor 5, the X-axial support 6 is arranged above the Z-axial support 7, and the Z-axial support 7 is arranged above the processing table 8; the X-axial support 6 can drive the tool bar 4 together with the special milling cutter 1 to adjust the position in the X-axial direction; the Z-axial support 7 can drive the X-axial support 6 arranged thereon to adjust the position in the Z-axial direction;

[0014] The tool bar 4 is a cylindrical structural member, and its external dimensions are adapted to the inner hole 51 of the spindle motor 5; the axis of the workpiece 9 to be processed with a large diameter inner hole is parallel to the upper side of the processing table 8;

[0015] One end of the workpiece 9 is fixed on the chuck 10 and locked by the claw 11, and the chuck 10 is arranged on the processing table 8 through the base 12;

[0016] The threaded protrusion 32 of the bolt-type connector is assembled into a whole with the hollow tubular structure at the rear end of the tool bar 4. The rotating tool bar 4 can realize the rotation adjustment of the sleeve-type tool turret 2 around the Z axis; thereby realizing the adjustment of the deflection angle θ of the axis of the square shoulder milling cutter 1a relative to the axis of the inner hole of the workpiece 9 to be processed;

[0017] The present invention also claims protection for a method for vertically milling a large-diameter inner hole using the aforementioned vertical milling large-diameter inner hole processing system, wherein the "large-diameter inner hole" refers to an inner hole with a diameter greater than 500 mm; the key technology is that it meets the following requirements:

[0018] The vertical milling method for large-diameter inner holes uses the following steps to perform milling on the large-diameter inner holes:

[0019] Step 1, the axis of the special milling cutter 1 is arranged perpendicularly to the axis of the inner hole of the large diameter tube of the workpiece 9 to be processed, and the rotation axis of the special milling cutter 1 is ensured to be perpendicular to the rotation axis of the workpiece 9 to be processed. During processing, the tool first cuts in from a position away from the chuck 10, and then moves along the axial direction of the inner hole of the workpiece 9 to be processed toward the chuck 10, gradually approaching the end face of the large diameter tube away from the chuck 10, and stops axial movement when the axis of the special milling cutter 1 reaches the parallel plane H with a distance L from the end face, and the distance from the H plane to the end face of the workpiece 9 to be processed is L=2r; here r is the radius of the special milling cutter;

[0020] Step 2, the special milling cutter 1 first moves radially along the projection circle of the inner hole surface of the large diameter blank of the workpiece 9 to be processed on the H surface, and stops moving when the upper and lower tool tips of the special milling cutter 1 intersect the projection circle, and then the special milling cutter 1 is swung clockwise around the axis of the inner hole of the workpiece 9 to be processed by a given angle θ, and the spindle driving the special milling cutter 1 to rotate is started, and the spindle driving the workpiece 9 to rotate is started;

[0021] Step 3: The special milling cutter 1 moves horizontally along the inner hole radial direction of the workpiece 9 by a given distance l. d , so that the cutting depth of the special milling cutter 1 on the inner hole surface reaches the given cutting depth a p , the position of the special milling cutter 1 is set as the starting point P, and the cutting depth a is considered in the rough machining process for machining efficiency. p >1.5mm, and considering the stability of the machine tool, the cutting depth a is required p <5mm;

[0022] Step 4: The special milling cutter 1 performs axial feed motion toward the chuck 10. When the workpiece 9 rotates one circle, the special milling cutter 1 moves a specified distance f in the axial direction of the workpiece 9 according to a given feed amount. a , realizing the linkage between the axial movement of the special milling cutter 1 and the rotation of the workpiece 9 to be processed;

[0023] Step 5, according to the requirements of the above step 4, the workpiece 9 rotates continuously, and the special milling cutter 1 continuously performs axial feed motion until the inner hole surface processing length reaches the axial size requirement, the special milling cutter 1 withdraws and returns to the starting point P to complete the processing of a complete inner hole surface.

[0024] The processing method for vertical milling of a large diameter inner hole of the present invention preferably claims the following technical contents:

[0025] Step 1 of the vertical milling large diameter inner hole processing process meets the following requirements or combinations:

[0026] In step 1, the following expression requirements are met:

[0027] L=2r

[0028] Where: r is the radius of the special milling cutter;

[0029] First, the distance L between the end face of the workpiece 9 away from the chuck 10 and the H surface where the rotation axis of the special milling cutter 1 is located should not be set too small. If it is too small, tool striking will occur, resulting in damage to the tool and the workpiece. It is required to be at least the radius r of the special milling cutter 1, so that the plane where the end face of the workpiece 9 is located and the blade of the special milling cutter 1 close to this end face just touch; secondly, it should not be set too large, otherwise it will cause low processing efficiency, so 2r is the best choice to ensure the above requirements.

[0030] Step 2 of the vertical milling large diameter inner hole processing process satisfies θ>θ min , and θ max ≤50°;

[0031] Minimum deflection angle θ of the special milling cutter 1 min The following expression requirements are met:

[0032]

[0033] in: This d is the distance before deflection; θ is the swing angle of the special milling cutter; l s l is the length of the shank; c is the thickness of the cutter head; l b is the circumferential cutting edge length of the blade; l d is the distance from the end face of the tool handle to the center of the inner hole; R is the radius of the inner hole; a p is the cutting depth; f is the distance from the center of the tool handle to the tool tip;

[0034] If the angle is too small, serious tool hitting will occur, especially in the rough machining process, the surface roughness is poor, and the surface flatness of the workpiece 9 is poor. At this time, the tool deflection angle is less than θ min This will cause the upper and lower blades of the special milling cutter 1 to contact the inner surface of the workpiece 9 at the same time, which may cause damage to the workpiece and the tool in severe cases.

[0035] Maximum deflection angle θ of special milling cutter 1 max≤50°; when it is greater than 50°, the tool tip strength tends to weaken significantly, and the vibration stability of the machining process decreases significantly, resulting in poor surface quality of the workpiece after machining; when machining the inner hole of a large-diameter round tube, when the special milling cutter 1 is deflected 90° and then radially fed along the end face of the workpiece 9 to be machined, the effect is the same as that of non-deflected machining, in that the upper and lower blades of the tool are in contact with the inner surface of the workpiece at the same time, and the process of milling with a single blade of the tool cannot be realized.

[0036] Step 3 of the vertical milling large diameter inner hole processing process needs to meet the following requirements or combinations:

[0037] In step 3, according to the required cutting depth, the tool is deflected at an appropriate angle and the tool is retracted so that the distance from the center of the workpiece to the center of the tool holder after retraction is l d The following expression requirements are met:

[0038]

[0039] in: α is the angle between the line from the center point of the tool holder to the tool tip after the tool is deflected and retracted and the tool rotation axis when the tool is not deflected.

[0040] In step 4, the maximum axial feed f is obtained by drawing amax And the axial feed rate f selected according to the processing requirements a <f amax , use the following steps in order:

[0041] Step A, draw a semicircle of the surface contour of the large diameter inner hole to be processed, and offset the inner cylindrical surface of the large diameter inner hole in the horizontal plane from the center of the inner hole in the radial direction to the given distance l d Get the base point A of the special milling cutter 1, and select this view as the front view;

[0042] Step B, taking point A as the center point of the end face of the special milling cutter handle, draw a front view of the yaw special milling cutter 1 with the rotation axis forming an angle θ with the horizontal line, and the length of the special milling cutter handle is l s The handle has a length of d and a thickness of l c , the radius of the cutter disc is r, and the length of the blade cutting edge is l b ;

[0043] Step C, the vertical distance D from the tip point B of the upper blade of the special milling cutter 1 to the tip point C of the lower blade e As the minor axis, with twice the radius r of the special milling cutter 1 as the major axis, and the extension line of the major axis passes through the center of the special milling cutter 1, draw the side projection ellipse of the rotating tool tip trajectory of the special milling cutter 1 on the inner hole surface (see Fig.11 );

[0044] Step D, taking the intersection point H of the end face edge of the upper blade of the special milling cutter 1 and the semicircular contour of the surface to be machined of the large diameter inner hole as the starting point, draw a horizontal auxiliary line to the ellipse, and pass through the ellipse to form intersection points M and N;

[0045] Step E: Measure the distance between point M and point N on the horizontal auxiliary line to get f amax .

[0046] Step 5 of the vertical milling large diameter inner hole processing process meets the following requirements:

[0047] During processing, the workpiece 9 rotates continuously, and the special milling cutter 1 continuously performs axial feed motion along the axial direction of the workpiece 9. When one cutting is completed and the axial dimension requirement of the processing length of the inner hole surface of the workpiece is reached, in order to avoid the surface quality of the workpiece being damaged or the tool being hit due to the secondary contact between the tool and the workpiece after milling is completed, the special milling cutter 1 first withdraws and returns to the starting point P and then straightens it. At this time, a complete inner hole surface processing is completed.

[0048] In the processing method for vertical milling of a large diameter inner hole, the following requirements are added after step 5:

[0049] Step 6, repeat the above steps 3, 4, and 5; according to the rough and fine processing requirements, select the appropriate cutting depth, determine the number of cutting layers and cut layer by layer, and finally complete the entire processing of the large diameter inner hole according to the size requirements.

[0050] Step 6 of the vertical milling large diameter inner hole processing process meets the following requirements:

[0051] Regarding the selection principle of cutting depth mentioned in step 3, when the milling allowance is not large, all the machining allowance should be milled off in one feed as much as possible; when the machining accuracy of the milled workpiece is high and the machining surface roughness value Ra is less than 6.3μm, it should be processed multiple times by rough milling and fine milling; and during the machining process, when the cutting depth a p When the cutting depth is greater than 1.5 mm, the surface roughness value will increase rapidly (i.e., the surface roughness will deteriorate); when the milling depth is a p When the surface roughness is less than 1.5 mm, the surface roughness value will increase slowly with the increase of cutting depth. Therefore, when the cutting depth during rough machining is considered, the cutting depth a can be selected in consideration of machining efficiency. p >1.5mm, and the cutting depth a is selected in consideration of surface quality during finishing. p <1.5mm, the processing process of determining the number of cutting layers and cutting one by one and multiple cutting is consistent with the processing process described in claim 1.

[0052] Before step 1, a three-jaw chuck is used to clamp the outer circle of the large-diameter pipe workpiece on a four-axis milling machine, and a center stand 13 is used to support the blank. When the workpiece length is greater than 6000 mm, more than two center stands 13 can be selected to achieve stable support for the workpiece 9 to be processed, so as to ensure the stability of the processing process, and always ensure that the rotation axis of the workpiece 9 to be processed is perpendicular to the rotation axis of the tool, and the straightness of the axis of the inner hole of the workpiece is 0.2 mm.

[0053] In summary, the advantages of the processing system for vertical milling of large-diameter inner holes and the processing method for vertical milling of large-diameter inner holes using the system of the present invention compared with the prior art are:

[0054] 1. In the processing system for vertical milling of a large-diameter inner hole, the present invention uses a square shoulder milling cutter 1a and a sleeve-type special milling cutter handle 1b to form a special milling cutter 1, and creatively arranges it vertically on a cutter bar 4 that can move in an axial direction parallel to the workpiece 9 to be processed; and it can flexibly realize the angular swing when vertically milling a large-diameter inner hole;

[0055] 2. The vertical milling method of the present invention replaces the traditional boring, turning and other processing methods of large diameter inner holes with milling. This method of milling large diameter inner holes greatly improves the cutting efficiency.

[0056] 3. Small radial force during milling reduces workpiece deformation, improves machining accuracy of large-diameter inner holes, improves machining quality of large-diameter inner holes, and achieves higher fatigue resistance;

[0057] 4. By milling a large-diameter inner hole, intermittent cutting is achieved without forming large-scale chips; milling with a swing angle significantly improves the shape of the chips and effectively avoids the phenomenon of chips circling the tool during traditional turning, which is conducive to automatic chip removal and easy to realize automated production of unmanned production lines; it is easy to protect the quality of the processed surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The present invention is further described in detail below with reference to the accompanying drawings and embodiments:

[0059] Figure 1 This is a schematic diagram of the processing principle when milling a large diameter inner hole;

[0060] Figure 2 It is a partial schematic diagram of the assembly of the tool bar 4 and the special milling cutter 1;

[0061] Figure 3 It is a partial schematic diagram of the sleeve-type turret 2 and the bolt-type connector 3 after assembly;

[0062] Figure 4 It is a structural diagram of the sleeve type turret 2;

[0063] Figure 5 It is a structural diagram of the bolt type connector 3;

[0064] Figure 6 It is a three-dimensional diagram showing the principle of the entire processing system;

[0065] Figure 7 For the corresponding Figure 6 A schematic diagram showing the composition principle of the entire processing system along the Z-axis direction;

[0066] Figure 8 A schematic diagram showing the principle of assembling a main shaft motor 5, an X-axial support 6, and a Z-axial support 7 as one body;

[0067] Fig. 9 It is a schematic diagram showing the assembly relationship between the Z-axis support 7 and the processing table 8;

[0068] Fig.10 Schematic diagram of tool deflection;

[0069] Fig.11 It is a schematic diagram of the principle of the mapping method;

[0070] Fig.12 Schematic diagram of the mapping method in Example 1 (θ is 28°);

[0071] Fig.13 Schematic diagram of the mapping method in Implementation Case 2 (θ is 15°). DETAILED DESCRIPTION

[0072] The meanings of the markings in the accompanying drawings are as follows: special milling cutter 1, square shoulder milling cutter 1a, sleeve-type special milling cutter handle 1b, sleeve-type turret 2, turret boss 21, turret groove 22, bolt-type connector 3, square hole 31 of the connector, internal protrusion 311 of the square hole of the connector, threaded protrusion 32 of the connector, tool rod 4, spindle motor 5, inner hole 51 of the spindle motor, X-axial support 6, X-axial support end face key 61, Z-axial support 7, Z-axial support keyway 71, Z-axial support end face key 72, machining table 8, machining table slide rail 81, workpiece to be machined 9, chuck 10, claw 11, base 12, center frame 13.

[0073] Fig.11 The drawing method shown in the figure, according to the drawing steps described in claim 5, finally draws the side projection of the rotating tool tip trajectory of the special milling cutter on the inner hole surface as an ellipse.

[0074] In order to more clearly explain the invention and its advantages, the invention and its implementation methods are described below. This description is not restrictive, and the actual implementation methods are not limited to this. In short, if ordinary technicians in this field are inspired by it, without departing from the purpose of the invention, they can design structures and embodiments similar to the technical solution without creativity, which should all fall within the protection scope of the present invention.

[0075] Example 1

[0076] A processing system for vertical milling of large diameter internal holes. The special milling cutter used in this processing system is as follows: Figure 2-9 As shown; the inner diameter of the workpiece 9 to be processed is greater than 500mm, Figure 2 The special milling cutter shown in the figure is composed of a square shoulder milling cutter 1a and a sleeve-type special milling cutter shank 1b, wherein the rotation axis of the square shoulder milling cutter 1a is perpendicular to the Figure 6 The rotation axis of the workpiece 9 shown in the figure and the hollow tubular structure at the rear of the sleeve-type special milling cutter handle 1b are similar to the Figure 4 The boss 21 on the sleeve-type turret 2 is fixedly assembled as a whole;

[0077] like Figure 4-5 The sleeve-type turret 2 shown in the figure is provided with grooves 22 on four sides perpendicular to its front side, and the grooves 22 cooperate with the protrusions 311 in the rectangular cavity inside the bolt-type connector 3 to facilitate fixing the sleeve-type turret 2, and the protrusions 311 are perpendicular to the axis of the shoulder milling cutter 1a, and the threaded protrusions 32 of the bolt-type connector are connected to the Figure 2 The hollow tubular structure at the rear end of the tool bar 4 is assembled as one body, and the rotating tool bar 4 can realize the rotation adjustment of the sleeve-type tool turret 2 around the Z axis, so as to realize the deflection angle θ of the axis of the square shoulder milling cutter 1a relative to the axis of the inner hole of the workpiece 9 to be processed;

[0078] Tool bar 4 Figure 7-9 The cylindrical structure is shown, and its external dimensions are adapted to the inner hole 51 of the spindle motor 5 and is arranged on the X-axial support 6 through the spindle motor 5. The X-axial support 6 can drive the tool bar 4 together with the special milling cutter 1 to adjust the position in the X-axis direction through the X-axial support end face key 61 and the Z-axial support keyway 71; and the X-axial support is arranged above the Z-axial support 7, and the Z-axial support 7 is arranged above the processing table 8. The Z-axial support 7 cooperates with the processing table slide rail 81 through the Z-axial support end face key 72 so that it can drive the X-axial support 6 arranged thereon to adjust the position along the Z-axis direction on the processing table 8;

[0079] like Figure 6 As shown, one end of the workpiece 9 is fixed by a three-jaw chuck 10 and supported by a center frame 13. The axis of the workpiece 9 is parallel to the axis of the tool bar 4 and is perpendicular to the rotation axis of the special milling cutter.

[0080] Example 2

[0081] One of the processing methods for vertical milling of a large diameter inner hole, the special milling cutter 1 and the processing system used therein are as described in Example 1, and will not be described in detail here;

[0082] The workpiece 9 to be processed is the inner surface of a TC4 large-diameter titanium alloy hot-rolled seamless pipe blank. The inner diameter of the blank is 535 mm, the inner diameter of the finished product is 545 mm, the wall thickness of the blank is 45 mm, and the maximum amount of processing on one side is 5 mm. Figure 6-7 As shown, the processing process of this embodiment is:

[0083] First, clamp the blank 9 with an outer diameter of 625mm and an inner diameter of 535mm on the three-claw chuck 10 of the four-axis horizontal CNC turning and milling machine tool; select the square shoulder milling cutter 1a with a diameter of 200mm and 12 teeth for milling. According to the standard cutting manual, the speed of the special milling cutter 1 during the milling process is 130r / min, the speed of the workpiece 9 to be processed is 0.186r / min, and the axial feed speed is 15.096mm / min. Then proceed according to the following sequence and requirements:

[0084] Step 1, the rotation axis of the special milling cutter 1 is arranged perpendicular to the rotation axis of the workpiece 9 to be processed. During processing, the tool first cuts in from a position away from the chuck 10, gradually approaches the end of the workpiece 9 to be processed away from the chuck, and stops axial movement when the axis of the special milling cutter 1 reaches the H surface.

[0085] Step 2: The special milling cutter 1 first moves radially along the projection circle of the large diameter inner hole surface of the workpiece 9 on the H surface, and stops moving when the upper and lower tool tips of the special milling cutter 1 intersect the projection circle. Then, according to formula (1): The special milling cutter 1 required should be around Fig.11 The clockwise rotation angle of point A is 2.246°, but considering the safety requirements of actual processing, the swing angle θ should be 28°, and the spindles driving the special milling cutter 1 and the workpiece 9 to be processed are started and rotated respectively.

[0086] Step 3: The cutting depth selected for the first roughing cut is 1.8 mm. According to formula (2): The special milling cutter handle point A is horizontally translated to a position 113.1 mm away from the center of the workpiece 9 to be processed and milling begins. At this time, the position of the special milling cutter 1 is the starting point P.

[0087] Step 4: According to the standard cutting manual and actual turning experience, this implementation case selects three rough milling cuts and one fine milling cut to complete the processing of 5mm margin. The specific milling parameters are shown in Table 1.

[0088] Table 1 Milling cutting parameters

[0089]

[0090]

[0091] The special milling cutter 1 performs axial feed motion toward the chuck 10, according to the following Fig.12 The drawing method shown in the figure obtains that the maximum axial feed rate is 81.16 mm / r when the special milling cutter is tilted 28° and the cutting depth is 1.8 mm, so the axial feed rate is selected as 80 mm / r.

[0092] Step 5, the workpiece 9 rotates continuously, and the special milling cutter 1 continuously performs axial feed motion until the inner hole surface processing length reaches the axial size requirement, the special milling cutter 1 withdraws, returns to the initial position and aligns the tool to complete a complete inner hole surface processing.

[0093] Step 6: According to the milling parameters described in Table 1, repeat the above steps 3, 4, and 5, complete the second and third rough turning and one fine turning layer by layer, and finally complete all the processing of the large diameter inner hole according to the size requirements.

[0094] Example 3

[0095] The second method for vertical milling of a large diameter inner hole, this embodiment refers to the first embodiment and the second embodiment and their corresponding drawings, and processes the inner hole surface of a Q235B large diameter seamless pipe blank with an inner diameter of 585mm to an inner diameter of 595mm, the blank wall thickness is 22.5mm, and the maximum amount to be processed on one side is 5mm. The processing process of this embodiment is as follows:

[0096] First, clamp the workpiece 9 with an outer diameter of 630mm and an inner diameter of 585mm on the three-claw chuck 10 of the four-axis horizontal CNC turning and milling machine tool; select the square shoulder milling cutter 1a with a diameter of 200mm and 12 teeth for milling. According to the standard cutting manual, the speed of the special milling cutter 1 during the milling process is 130r / mm, the speed of the workpiece 9 is 0.186r / min, and the axial feed speed is 14.1mm / min. Then proceed in the following order and requirements:

[0097] Step 1, the rotation axis of the special milling cutter 1 and the rotation axis of the workpiece 9 to be processed are arranged perpendicularly. During processing, the tool first cuts in from a position away from the chuck 10, and gradually approaches the end of the workpiece 9 to be processed away from the chuck 10. When the axis of the special milling cutter 1 reaches the H surface, the axial movement stops.

[0098] Step 2: The special milling cutter 1 first moves radially along the projection circle of the large diameter inner hole surface of the workpiece 9 on the H surface, and stops moving when the upper and lower tool tips of the special milling cutter 1 intersect the projection circle. Then, according to formula (1): The special milling cutter 1 required should be around Fig.11The clockwise rotation angle of point A is 2.196°, but considering the safety requirements of actual processing, the swing angle θ should be 15°, and the spindles driving the special milling cutter 1 and the workpiece 9 to be processed are started and rotated respectively.

[0099] Step 3: Based on the selected cutting depth of 2 mm during the first roughing operation, according to formula (2): Point A of the special milling cutter handle should be horizontally moved to a position 144.7 mm away from the center of the workpiece 9 to start milling. At this time, the position of the special milling cutter 1 is the starting point P.

[0100] Step 4: According to the standard cutting manual and actual turning experience, this implementation case selects three rough milling cuts and one fine milling cut to complete the processing of 5mm margin. The specific milling parameters are shown in Table 2.

[0101] Table 2 Milling cutting parameters

[0102]

[0103] The special milling cutter 1 performs axial feed motion toward the chuck 10, according to the following Fig.13 The drawing method shown in the figure obtains that the maximum axial feed rate is 77.92 mm / r when the special milling cutter is tilted 15° and the cutting depth is 2 mm, so the axial feed rate is selected as 75 mm / r.

[0104] Step 5, the workpiece 9 rotates continuously, and the special milling cutter 1 continuously performs axial feed motion until the inner hole surface processing length reaches the axial size requirement, the special milling cutter 1 withdraws, returns to the initial position and aligns the tool to complete a complete inner hole surface processing.

[0105] Step 6, according to the milling parameters described in Table 1, repeat the above steps 3, 4, and 5, complete the second and third rough turning and one fine turning layer by layer, and finally complete all the processing of the large diameter inner hole according to the size requirements. Different from Example 2, the material of the workpiece is Q235B large diameter seamless pipe, and the swing angle is 15°.

[0106] The processing method described above in this embodiment has the advantages of milling processing, and the tool deflection during processing can effectively avoid damage to the tool and workpiece caused by tool collision accidents, ensure that the single-side cutter teeth touch the workpiece to achieve processing, thereby improving the processing surface quality, reducing the axial force on the special milling cutter, effectively reducing the cutting temperature, and improving the metal removal rate. This processing method can better control the tool to perform turning and milling and can avoid the vibration of the tool bar causing a decrease in processing accuracy and affecting the forming quality of the workpiece.

Claims

1. A processing system for vertical milling of large diameter inner holes, characterized in that: The vertical milling large diameter inner hole processing system meets the following requirements: The processing system for vertical milling of a large-diameter inner hole specifically comprises a tool bar (4), a bolt-type connector (3), a sleeve-type tool turret (2), and a special milling cutter (1); wherein: The special milling cutter (1) is composed of a square shoulder milling cutter (1a) and a sleeve-type special milling cutter handle (1b); the rotation axis of the square shoulder milling cutter (1a) is perpendicular to the rotation axis of the workpiece (9) to be processed; the rear part of the sleeve-type special milling cutter handle (1b) is a hollow tubular structure; The sleeve-type turret (2) is a cubic structure, and the sleeve-type turret (2) can be arranged in a rectangular parallelepiped cavity in the bolt-type connector (3) through the front side of the bolt-type connector (3); a groove (22) is provided on at least one of the four side surfaces of the sleeve-type turret (2) perpendicular to the front side surface thereof; a boss (21) is provided on the front side surface of the sleeve-type turret (2); the boss (21) is fixedly assembled with a hollow tubular structure at the rear of a sleeve-type special milling cutter handle (1b) as a whole; The bolt-type connector (3) is in the shape of a rectangular parallelepiped, and a rectangular parallelepiped cavity is arranged therein. A square hole (31) is arranged on the front side thereof, which is convenient for inserting the sleeve-type tool turret (2) and is connected to the rectangular parallelepiped cavity inside the bolt-type connector (3). At least one protrusion (311) perpendicular to the axis of the square shoulder milling cutter (1a) is arranged in the rectangular parallelepiped cavity inside the bolt-type connector (3). The protrusion (311) cooperates with the sleeve-type tool turret groove (22) to facilitate fixing the sleeve-type tool turret (2). A threaded protrusion (32) is provided on one of the side surfaces of the bolt-type connector (3) parallel to the axis of the square shoulder milling cutter (1a), the threaded protrusion (32) and the cutter bar (4) are coaxial and the two are fixedly connected as one body; The tool bar (4) is arranged on the X-axial support (6) through the spindle motor (5), the X-axial support (6) is arranged above the Z-axial support (7), and the Z-axial support (7) is arranged above the processing table (8); the X-axial support (6) can drive the tool bar (4) together with the special milling cutter (1) to adjust the position in the X-axial direction; the Z-axial support (7) can drive the X-axial support (6) arranged thereon to adjust the position in the Z-axial direction; The tool bar (4) is a cylindrical structural member, and its external dimensions are adapted to the inner hole (51) of the spindle motor (5); the axis of the workpiece to be processed (9) having a large-diameter inner hole is parallel to the upper side of the processing table (8); One end of the workpiece (9) to be processed is fixed to and locked on a chuck (10) through a clamping claw (11), and the chuck (10) is arranged on a processing table (8) through a base (12); The threaded protrusion (32) of the bolt-type connector is assembled into a whole with the hollow tubular structure at the rear end of the tool rod (4). The rotating tool rod (4) can realize the rotation adjustment of the sleeve-type tool turret (2) around the Z axis, thereby realizing the adjustment of the deflection angle θ of the axis of the square shoulder milling cutter (1a) relative to the axis of the inner hole of the workpiece (9) to be processed.

2. A method for vertically milling a large-diameter inner hole using the processing system for vertically milling a large-diameter inner hole according to claim 1, wherein the "large-diameter inner hole" refers to an inner hole with a diameter greater than 500 mm; characterized in that: The vertical milling method for large-diameter inner holes uses the following steps to perform milling on the large-diameter inner holes: Step 1, the axis of the special milling cutter (1) is arranged perpendicularly to the axis of the inner hole of the large diameter tube of the workpiece (9) to be processed. During processing, the cutter first cuts in from a position away from the chuck (10), and then moves along the axial direction of the inner hole of the workpiece (9) to be processed toward the chuck, gradually approaching the end face of the large diameter tube away from the chuck (10). When the axis of the special milling cutter (1) reaches a parallel plane H at a distance L from the end face, the axial movement stops. The distance from the H plane to the end face of the workpiece (9) to be processed is L=2r; here r is the radius of the special milling cutter; Step 2, the special milling cutter (1) first moves radially along the projection circle of the large diameter inner hole surface of the workpiece (9) to be processed on the H surface, and stops moving when the upper and lower tool tips of the special milling cutter (1) intersect with the projection circle. Then, the special milling cutter (1) is swung clockwise around the inner hole axis of the workpiece (9) to be processed by a given angle θ, and the spindle driving the special milling cutter (1) to rotate is started, and the spindle driving the workpiece (9) to rotate is started; Step 3: The special milling cutter (1) moves horizontally along the radial direction of the inner hole of the workpiece (9) for a given distance l. d , so that the cutting depth of the special milling cutter (1) on the inner hole surface reaches a given cutting depth a p , the position of the special milling cutter (1) is set as the starting point P, and the cutting depth a is considered in the rough machining process in consideration of machining efficiency. p >1.5mm, and considering the stability requirement of the machine tool p <5mm; Step 4, the special milling cutter (1) performs axial feed motion in the direction of the chuck (10), and the special milling cutter (1) moves a specified distance f in the axial direction of the workpiece (9) at a given feed rate for each rotation of the workpiece (9). a , realizing the linkage between the axial movement of the special milling cutter (1) and the rotation of the workpiece to be processed (9); Step 5, in accordance with the requirements of the aforementioned step 4, the workpiece (9) is continuously rotated, and the special milling cutter (1) is continuously fed axially until the inner hole surface processing length reaches the axial dimension requirement, and the special milling cutter (1) is withdrawn and returns to the starting point P, completing a complete inner hole surface processing.

3. The method for vertically milling a large diameter inner hole according to claim 2, characterized in that: Step 1 of the vertical milling large diameter inner hole processing process meets the following requirements or combinations: In step 1, the following expression requirements are met: L＝2r Where: r is the radius of the special milling cutter; The distance L between the end face of the workpiece (9) away from the chuck (10) and the H plane where the axis of rotation of the special milling cutter (1) is located should not be set too small. If L is too small, the tool will be damaged and the workpiece will be damaged. It is required that L is at least the radius r of the special milling cutter (1), so that the plane where the end face of the workpiece (9) is located and the blade of the special milling cutter (1) close to this end face just touch each other; secondly, L should not be set too large. If L is too large, it will cause low processing efficiency. Therefore, 2r is the best choice to ensure the above requirements.

4. The method for milling a large diameter inner hole according to claim 2, characterized in that: Step 2 of the vertical milling large diameter inner hole processing process satisfies θ>θ min ; Minimum deflection angle θ of the special milling cutter (1) min The following expression requirements are met: in: This d is the distance before deflection; θ is the swing angle of the special milling cutter; l s l is the length of the shank; c is the thickness of the cutter head; l b is the circumferential cutting edge length of the blade; l d is the distance from the end face of the tool handle to the center of the inner hole; R is the radius of the inner hole; a p is the cutting depth; f is the distance from the center of the tool handle to the tool tip; If the angle is too small, serious tooling will occur, especially in the rough machining process, the surface roughness is poor, and the surface flatness of the workpiece (9) is poor. At this time, the tool deflection angle is less than θ min This will cause the upper and lower blades of the special milling cutter (1) to contact the workpiece (9) at the same time, causing damage to the workpiece and the cutter; Maximum deflection angle θ of special milling cutter max ≤50°.

5. The method for machining a large diameter inner hole according to claim 2, characterized in that: Step 3 of the vertical milling large diameter inner hole processing process needs to meet the following requirements or combinations: In step 3, according to the required cutting depth, the tool is deflected at an appropriate angle and the tool is retracted so that the distance from the center of the workpiece to the center point A of the tool holder after retraction is l d The following expression requirements are met: in: α is the angle between the line from the center point of the tool holder to the tool tip after the tool is deflected and retracted and the tool rotation axis when the tool is not deflected.

6. The method for vertically milling a large diameter inner hole according to claim 2, characterized in that: In step 4, the maximum axial feed f is obtained by drawing amax And the axial feed rate f selected according to the processing requirements a <f amax , use the following steps in order: Step A, draw a semicircle of the contour of the large diameter inner hole to be processed of the workpiece (9), and offset the inner cylindrical surface of the large diameter inner hole to be processed by a given distance l from the center of the inner hole in the radial direction d Get the special milling cutter (1) to draw the base point A, and select this view as the front view; Step B, taking point A as the center point of the end face of the special milling cutter handle, draw a front view of the sway special milling cutter (1) with the rotation axis forming an angle θ with the horizontal line, and the length of the special milling cutter handle is l s , the thickness of the cutter head is l c , the blade circumferential cutting edge length is l b , the distance from the end face of the tool handle to the center of the inner hole is l d , the radius of the cutter disc is r; Step C: The vertical distance D from the tip point B of the upper blade of the special milling cutter (1) to the tip point C of the lower blade is e As the minor axis, with twice the radius r of the special milling cutter (1) as the major axis, and the extension line of the major axis passing through the center of the special milling cutter (1), draw a side projection ellipse of the trajectory of the rotating tool tip of the special milling cutter (1) on the inner hole surface; Step D, taking the intersection point H between the end face edge of the upper blade of the special milling cutter (1) and the semicircular contour of the surface to be machined of the large diameter inner hole as the starting point, drawing a horizontal auxiliary line towards the ellipse, and passing through the ellipse to form intersection points M and N; Step E: Measure the distance between point M and point N on the horizontal auxiliary line to get f amax .

7. The method for vertically milling a large diameter inner hole according to claim 2, characterized in that: Step 5 of the vertical milling large diameter inner hole processing process meets the following requirements: During processing, the workpiece (9) to be processed rotates continuously, and at the same time, the special milling cutter (1) continuously performs axial feed motion along the axial direction of the workpiece (9) to be processed. When one cutting is completed and the axial dimension requirement of the processing length of the inner hole surface of the workpiece is reached, in order to avoid the surface quality of the workpiece being damaged or the cutting being beaten due to the secondary contact between the tool and the workpiece after the milling is completed, the special milling cutter (1) first withdraws and returns to the starting point P and then is straightened. At this time, a complete inner hole surface processing is completed.

8. The method for vertically milling a large diameter inner hole according to any one of claims 2 to 6, characterized in that: In the processing method for vertical milling of a large diameter inner hole, the following requirements are added after step 5: Step 6, repeat the above steps 3, 4, and 5; according to the rough and fine processing requirements, select the appropriate cutting depth, determine the number of cutting layers and cut layer by layer, and finally complete the entire processing of the large diameter inner hole according to the size requirements.

9. The method for vertically milling a large diameter inner hole according to claim 8, characterized in that: Step 6 of the vertical milling large diameter inner hole processing process meets the following requirements: Regarding the selection principle of cutting depth mentioned in step 3, when the milling allowance is not large, all the machining allowance should be milled off in one feed as much as possible; when the machining accuracy of the milled workpiece is high and the machining surface roughness value Ra is less than 6.3μm, it should be processed multiple times by rough milling and fine milling; and during the machining process, when the cutting depth a p >1.5mm, the surface roughness value will increase rapidly with the increase of cutting depth; when the milling depth a p When the surface roughness is less than 1.5 mm, the surface roughness value will increase slowly with the increase of cutting depth. Therefore, when the cutting depth during rough machining is considered, the cutting depth a can be selected in consideration of machining efficiency. p >1.5mm, and the cutting depth a is selected in consideration of surface quality during finishing. p <1.5mm, the processing process of determining the number of cutting layers and cutting one by one and multiple cutting is consistent with the processing process described in claim 2.

10. The method for vertically milling a large diameter inner hole according to claim 8, characterized in that: The vertical milling method for machining a large-diameter inner hole also meets the following requirements: before step 1, the outer circle of the large-diameter workpiece (9) to be machined is clamped by the jaws (11) of a three-jaw chuck (10) on a four-axis milling machine, and the workpiece (9) to be machined is supported by a center frame (13) to ensure the stability of the workpiece during machining.

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