A machining method for high-precision thin-walled aluminum cylinder parts

Abstract

This invention relates to a method for machining high-precision thin-walled aluminum cylindrical parts. The method employs a strong-spinning technique to spin-form the aluminum cylindrical part, followed by CNC turning using various specialized fixtures to precision machine the toleranced outer diameter, inner hole size, and threads. This method solves the problem of deformation caused by radial clamping force, addressing the machining challenges of high-precision thin-walled aluminum cylindrical parts. It ensures the accuracy of the high-precision thin-walled aluminum cylindrical part after strong spinning. At different machining stages, various specialized fixtures are creatively designed. By employing these fixtures, the machining of high-precision thin-walled aluminum cylindrical parts after strong spinning is achieved, solving the problem of deformation during machining. The designed specialized fixtures feature high positioning accuracy, simple operation, and convenient workpiece loading and unloading. The method has a wide processing range and strong applicability.

Description

Technical Field

[0001] This invention belongs to the field of machining technology, specifically relating to a method for machining high-precision thin-walled aluminum cylinders. Background Technology

[0002] Currently, for the processing of thin-walled aluminum cylinder parts, single-piece and small-batch processing all adopt turning to the finished size. However, under the influence of cutting force, clamping force, internal stress and other factors, deformation is easily generated, which fails to meet the requirements of the drawings and ultimately leads to the workpiece being scrapped due to exceeding tolerances and becoming unusable. Summary of the Invention

[0003] This invention provides a high-precision processing method for thin-walled aluminum cylindrical parts. The technical problem to be solved is to address the issue of excessive deformation during the processing of thin-walled aluminum cylindrical parts, which leads to the scrapping of the parts.

[0004] To address the above technical problems, this invention provides a method for processing high-precision thin-walled aluminum cylindrical parts, characterized by comprising the following steps:

[0005] S1. Material feeding;

[0006] S2. Roughly machine the outer diameter, end face and inner hole of the blank to obtain a cylindrical part with a stepped hole at one end;

[0007] S3. Heat treatment is performed on the processed blank (2);

[0008] S4. Use a powerful spinning tool to machine the outer diameter of the blank in a positive spinning motion;

[0009] The high-power spinning fixture consists of a connecting body (3), a mandrel (4), a material ejector sleeve (5), three spinning wheels (6), and a locking screw (7). The connecting body (3) is connected to the spindle centering shaft and flange of the high-power spinning equipment. One end of the mandrel (4) is fixedly connected to the connecting body, and the other end passes through the blank and is fastened to the locking screw (7). The end of the mandrel is matched with the stepped hole of the blank for limiting position.

[0010] The blank outer diameter is machined by rotating three spinning wheels that are staggered back and forth on the outside of the blank in a forward rotation; annealing is required between spinning passes during the spinning process;

[0011] S5. Use a special lifting fixture to perform solution aging on the aluminum cylinder (8) after strong rotation;

[0012] S6. Machining of the internal thread and full length of the workpiece (13) after solid-state aging;

[0013] S7. Tighten the workpiece (19) onto a special fixture equipped with a serrated polyurethane elastomer damping ring, and finish machine the outer diameter of the workpiece.

[0014] The special fixture consists of a flange (20), a body (21), an expansion bearing (23), a pull core (24), a sawtooth polyurethane elastomer vibration damping ring (25), a threaded support ring (26), and a live center (27);

[0015] The flange (20) is fixed on the machine tool, the body (21) is fixed on the flange (20), the expansion bearing (23) is placed on the conical surface of the body (21), the pull core (24) is inserted into the inner hole of the body and connected to the cylinder, the end face of the pull core (24) is pressed against the end face of the conical surface of the body (21), the polyurethane elastomer sealing ring (22) is fitted in the groove of the outer circle of the expansion bearing (23), the serrated polyurethane elastomer damping ring (25) has a serrated structure on its outer circumference and inner hole, and is inserted on the pull core (24), the workpiece (19) is fitted on the serrated polyurethane elastomer damping ring (25) and the expansion bearing (23), the threaded support ring (26) is threadedly connected to the end of the workpiece (19), and the live center (27) is axially pressed against the threaded support ring (26);

[0016] S8. Use a micro-force clamping fixture with an upper tension floating cylinder to precision machine the inner hole of the workpiece;

[0017] The upper tensioning type floating support cylinder micro-force clamping fixture is composed of a flange (29), a clamping sleeve (30), a pull core shaft (33), a movable pressure plate (34), a body (36), a floating support cylinder (37), a positioning sleeve (38), a cylinder body sleeve (40), a pressure cover (42), and an air inlet valve (44);

[0018] The flange (29) is fixed on the centering shaft of the lathe spindle. Three support plates (32) are fixed on the flange (29) at 120° intervals. One end of the movable pressure plate (34) is hinged to the support plate (32); the other end of the movable pressure plate (34) is hinged to the pull shaft (33). The reciprocating motion of the pull shaft (33) pushing forward and pulling backward drives the movable pressure plate (34) to loosen and tighten the clamping sleeve (30). The clamping sleeve (30) is screwed into the internal thread at the front end of the workpiece (28) and fits against the end face of the workpiece (28). The front end of the body (36) is fixed to the flange. The outer ring of the disc (29) is fixed to the rear end of the body (36), the positioning sleeve (38) is fixed inside the positioning sleeve (38), the floating support cylinder (37) is fixed inside the equally spaced threaded holes in the center hole of the cylinder sleeve (40), the air intake valve (44) is set inside the positioning sleeve (38) and cooperates with the end face of the cylinder sleeve (40), the air intake valve (44) is a rotating part; the cylinder sleeve (40) has an annular groove that communicates with the air intake hole of the air intake valve (44), the pressure cap (42) is fixed to the rear end of the positioning sleeve (38); the floating support cylinder (37) clamps and straightens the workpiece with a small force.

[0019] Beneficial Effects: This invention employs a strong-spinning technique to spin-form aluminum cylindrical parts, followed by CNC turning using various specialized fixtures to precision machine the tolerances for outer diameter, inner hole size, and threads. This solves the problem of deformation caused by radial clamping force, addressing the machining challenges of high-precision thin-walled aluminum cylindrical parts. It ensures the accuracy of the high-precision thin-walled aluminum cylindrical parts after strong spinning. At different machining stages, a variety of specialized fixtures are creatively designed. By utilizing these fixtures, the machining of high-precision thin-walled aluminum cylindrical parts after strong spinning is achieved, solving the problem of deformation during machining. The designed specialized fixtures feature high positioning accuracy, simple operation, and convenient workpiece loading and unloading. It has a wide processing range and strong applicability. Attached Figure Description

[0020] Figure 1 Blank cutting diagram

[0021] Figure 2 roughing drawing diagram

[0022] Figure 3 Spinning diagram

[0023] Figure 4 Schematic diagram of the workpiece after spinning

[0024] Figure 5 Lifting clamp diagram

[0025] Figure 6 Schematic diagram of folding hoisting tools

[0026] Figure 7 Workpiece hoisting diagram

[0027] Figure 8 Schematic diagram of the part after solution aging

[0028] Figure 9 Stepped bench thread and full-length machining diagram

[0029] Figure 10 Schematic diagram of a workpiece after threading and full-length machining.

[0030] Figure 11 Schematic diagram of a fixture for finishing outer diameter

[0031] Figure 12 Enlarged schematic diagram of a fixture for finishing outer diameter

[0032] Figure 13 Schematic diagram of a workpiece after finishing of its outer diameter

[0033] Figure 14 Schematic diagram of tension-type floating support cylinder micro-force clamping fixture

[0034] Figure 15 A partially enlarged schematic diagram of the micro-force clamping fixture for the tensioning type floating support cylinder. Detailed Implementation

[0035] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below.

[0036] The present invention proposes a method for processing high-precision thin-walled aluminum cylindrical parts, which specifically includes the following processing steps:

[0037] S1. Blanking: Based on the dimensions of the spinning blank, select 2A12 aluminum alloy (GB / T4437.1-2015), grade 2A12-T4, with supply and testing status O. Complete the blanking (1). Figure 1 As shown.

[0038] S2. Use a double-top roughing machine to machine the outer diameter and end face until the outer diameter is smooth. The outer diameter tolerance is controlled within 0.05mm. Use a 90° front and back flaring tool body with a 55° diamond-shaped CNC insert to machine both ends of the spinning blank in double-top mode and control the entire length.

[0039] The inner hole is machined by using a clamping method with one clamp and one frame to complete the rough machining of the blank (2), and a cylindrical part with a stepped hole at one end is obtained, which is convenient for installation on the spinning mandrel.

[0040] S3. The processed blank (2) is subjected to heat treatment. The heat treatment state of the blank (2) is: H112 state annealing, heating to 380 degrees with the furnace, holding for 45 minutes, furnace cooling to 260 degrees, and air cooling. Adjust the holding time according to the wall thickness of the spun blank.

[0041] S4. Since the rough-machined blank (2) is a cylindrical part with a stepped hole at one end and a small inner diameter of the bottom thread, a special high-power spinning tool must be used to spin-machine the outer diameter of the blank. This high-power spinning tool consists of a connecting body (3), a mandrel (4), a ejector sleeve (5), three spinning wheels (6), and a locking screw (7). Figure 3 As shown.

[0042] like Figure 2 As shown. The wall thickness of the spun blank is relatively thin. The outer diameter of the spun blank is precision machined by placing the blank with the machined inner hole and chamfered on the mandrel and pressing the locking screw on the tail end of the blank. The outer diameter of the mandrel should take into account the effect of the diameter expansion after strong spinning. By adjusting the spinning parameters, the inner hole diameter expansion of the 2A12T4 aluminum cylinder workpiece after spinning can be controlled between 0.05mm and 0.2mm.

[0043] During processing, the connecting body (3) is connected to the spindle centering diameter and flange of the high-power spinning equipment. One end of the mandrel (4) is fixedly connected to the connecting body, and the other end is inserted into the blank and fitted with the inner stepped hole of the blank. The end of the locking screw is threadedly connected to the threaded hole at the end of the mandrel, and the stepped surface of the locking screw rests on the end face of the blank.

[0044] Before spinning, the outer diameter hardness of the mandrel (4) is 60HRC. The radial runout at both ends of the mandrel is checked and ensured to be within 0.05mm.

[0045] The three rotating wheels (6) have a diameter of φ280 and are designated as the front rotating wheel, middle rotating wheel, and rear rotating wheel. The cone angles of the front rotating wheel, middle rotating wheel, and rear rotating wheel are R8×20° and R6×20°×3°, respectively. The hardness of the front, middle, and rear rotating wheels is 60HRC, the misalignment is 4.12 / 3.52 / 0, and the runout is less than 0.03.

[0046] Three rotating wheels are equally spaced and staggered around the blank, and the outer diameter of the blank is machined by rotating in the forward direction.

[0047] During the spinning process, the hardness of the blank (2) changes. After spinning, the surface of the blank hardens. If spinning deformation continues, defects such as cracks are likely to occur. Therefore, it is necessary to perform inter-spinning annealing to restore the material's plasticity for the next spinning deformation. The inter-spinning heat treatment method of this invention is to raise the temperature to 330°C in the furnace, hold it for 1 hour, cool it in the furnace to 260°C, and then air cool it.

[0048] The effects of spinning, heat treatment, and other processes on hardness are shown in Table 1. The table shows that the hardness of the H112 state blank is 325–334 HL, decreasing to 313–320 HL after annealing at 380 degrees Celsius, although the decrease is not significant. After spinning, the workpiece wall thickness is reduced from 8.1 mm to 4.65 mm, resulting in surface hardening and an increase in hardness to 347–360 HL. Subsequent annealing at 330 degrees Celsius reduces the hardness to 293–300 HL, a substantial decrease, even lower than the hardness of the annealed H112 state blank, thus providing a foundation for the next deformation step.

[0049] Table 1. Effects of spinning deformation and heat treatment on hardness.

[0050]

[0051]

[0052] The effect of thinning rate on inner diameter accuracy

[0053] Table 2 shows the effect of different thinning rates on the inner diameter. As can be seen from the table, with the feed ratio remaining constant, as the thinning rate increases from 18.5% to 24.4% and 28.4%, the inner diameter increases from 128.00 to 127.80 and 127.75, respectively. That is, as the thinning rate increases, the inner diameter gradually decreases. The inner diameter of the blank before spinning is 127.8, and the expansion amounts are 0.20, 0, and -0.05, respectively. That is, the expansion amount gradually decreases, which is more conducive to mold application.

[0054] Table 2. Effect of thinning rate on inner diameter

[0055]

[0056] Table 3 shows the effect of different feed ratios on the inner diameter. As can be seen from the table, with the thinning rate remaining constant, as the feed ratio increases from 0.8 mm / r to 1.0 mm / r and 1.2 mm / r, the inner diameter increases from 127.77 to 127.710 and 127.60, respectively. That is, as the feed ratio increases, the inner diameter gradually decreases. The outer diameter of the mandrel is 127.52, and the expansion amounts are 0.25, 0.19 and 0.08, respectively. In other words, the gradual increase of the feed ratio is more conducive to mold bonding.

[0057] Table 3. Effect of feed ratio on inner diameter

[0058]

[0059] Table 4 shows the effect of different spinning passes on the inner diameter accuracy. As can be seen from the table, when the feed ratio for the first pass is 0.8 mm / r, the blank diameter is 127.8 mm, and the inner diameter after spinning is 128.0 mm, an increase of 0.2 mm. When the feed ratio for the second pass increases to 1 mm / r, the inner diameter after spinning is 127.9 mm, a decrease of 0.1 mm compared to the original inner diameter, showing a shrinking trend. After the second spinning pass, intermediate annealing is performed, reducing the hardness. The third passing pass, with a feed ratio of 1 mm / r, results in a shrinkage of 0.1 mm after spinning, also showing a shrinking trend.

[0060] Table 4. Influence of spinning passes on inner diameter

[0061]

[0062] Through process optimization, serrated grooves are machined on the end faces of the mandrel and the locking screw, increasing the friction between the mandrel and the spinning blank. Under the axial force of the locking screw, the spinning blank is prevented from rotating. This is suitable for heavy-duty spinning of blanks with small internal steps. Dovetail grooves are machined on the connecting body and the ejector sleeve. When the mandrel rotates forward and backward, the ejector sleeve self-locks onto the dovetail groove of the connecting body. Furthermore, the problem of uneven inner diameter transition at the workpiece opening has been resolved through optimization of spinning technology parameters.

[0063] The problem of uneven inner diameter transition at the mouth transition point was solved. The inner diameter of the aluminum cylinder (8) after strong turning was machined according to the drawing (the stop and thread for the inner diameter fit were machined on a lathe), and the outer diameter was left with a 1mm allowance according to the drawing and then precision machined on a CNC lathe, such as Figure 4 As shown.

[0064] S5. To prevent deformation of the aluminum cylinder (8) after strong rotation during the solution treatment, the aluminum cylinder (8) after strong rotation is subjected to solution treatment aging using a special lifting fixture. The lifting fixture consists of a folding lifting tool (9), a top cover (10), a material frame (11), and a base (12) with a column. Figure 5 As shown. In use, first place the material frame (11) on the base (12) with the column, and connect it to the base (12) with the column using a pin; then place the strongly spun aluminum cylinder (8) inside the material frame (11), insert the top cover (10) into the upper part of the base (12) with the column, and connect it to the material frame (11) with a pin; insert the folding lifting tool (9) into the strongly spun aluminum cylinder (8), as shown. Figure 6 As shown, the folding hoisting tool (9) mainly consists of a threaded center rod (9-1), a threaded sleeve (9-2), an outer sleeve (9-3), a fixing pin (9-4), a base plate (9-5), a support plate (9-6), and a folding rod (9-7).

[0065] The bottom of the threaded center rod (9-1) is fixedly connected to the support plate (9-6). Multiple sets of folding rods (9-7) are evenly distributed on the outer circumference of the support plate (9-6). Each set of folding rods (9-7) is formed by two connecting rods hinged together. One end of the folding rod (9-7) is hinged to the support plate, and the other end is hinged to the outer sleeve (9-3). The threaded sleeve (9-2) is threadedly connected to the center rod (9-1). The outer sleeve (9-3) is fitted over the threaded sleeve (9-2). The threaded sleeve (9-2) drives the outer sleeve (9-3) to move up and down. The upper end of the center rod (9-1) is connected to the upper cover (10).

[0066] In use, rotating the screw sleeve (9-2) causes the outer sleeve (9-3) to move up and down along the central rod (9-1). The outer sleeve (9-3) drives the folding rod (9-7) to open or retract via the fixed pin (9-4). When the folding rod (9-7) retracts, it is convenient to remove the screwed aluminum cylinder (8). When the folding rod (9-7) opens, it serves to fix and hoist the screwed aluminum cylinder (8). When hoisting is required, first insert the retracted folding hoisting tool (9) into the screwed aluminum cylinder (8), then open the folding hoisting tool (9) so that the folding rod (9-7) supports the inner wall of the screwed aluminum cylinder (8) and is locked at the threaded step, such as... Figure 7As shown, the folding lifting tool (9) with the strongly rotated aluminum cylinder (8) is finally fixed on the top cover (10). Finally, the assembled lifting fixture with the workpiece is subjected to heat treatment.

[0067] This lifting fixture has a simple and compact structure, and allows for quick and convenient loading and unloading of workpieces.

[0068] The aluminum cylinder (8) after strong rotation is made of 2A12H112. The specific solid-state aging process is as follows: Heating: Heating is carried out in a solid-state furnace. The workpiece is suspended in the material frame and subjected to a vertical downward force, which effectively prevents the workpiece from deforming due to external forces during the heating process. The heating temperature is 495~503℃ and the holding time is 40min~50min. Cooling: After the workpiece is taken out of the furnace, a 5%~10% sodium chloride aqueous solution is used as the cooling medium. The medium temperature is 20℃~40℃ and the cooling time is 5min. Artificial aging: Heating is carried out in an aging furnace. The heating temperature is 185℃~195℃ and the holding time is 8h~12h. Natural aging: After the workpiece is taken out of the furnace, it is placed in a workshop with a room temperature of 10℃~15℃ for 96h. The solid-state aging workpiece (13) is obtained.

[0069] S6. Use an internal support fixture to perform internal thread and full-length machining on the workpiece (13) after heat treatment aging.

[0070] The internal support clamp includes an open-type expansion tire (16), a tie rod (14), a three-jaw chuck (15), a polyurethane vibration damping sleeve (17), and a live center (18);

[0071] Insert the workpiece (13) after solid-state aging into the open-type expansion mold (16) and clamp it with a three-jaw chuck (15). One end of the open-type expansion mold passes through the three-jaw chuck and engages with the inner tapered hole of the spindle for positioning, and is secured with the pull rod (14) to prevent the open-type expansion mold (16) from loosening. The contact area of ​​the tapered surface is greater than 75%. Use a dial indicator to align the coaxiality of the open-type expansion mold (16) to less than 0.03 mm. Place a polyurethane vibration damping sleeve (17) at the stepped platform on the rear end face of the open-type expansion mold (16), and install a special live center (18) at the tailstock. The end of the live center has an outer tapered surface. By moving the special live center (18) forward, the three openings of the positioning open-type expansion mold (16) are radially opened, squeezing the solid-state aging workpiece (13) tightly. Figure 9 As shown.

[0072] Due to the expansion of the orifice, the actual length of the workpiece (13) after solid-state aging is approximately 60mm to 100mm. The workpiece (13) after solid-state aging is clamped on the open-type expansion mold (16) equipped with a polyurethane damping sleeve (17). The distance between the inner step surface of the internal thread and the end face of the open-type expansion mold (16) is 10mm to 15mm to prevent collision with the end face of the open-type expansion mold (16) during internal thread turning and to facilitate measurement of the length of the internal thread step. The workpiece (13) after solid-state aging is tightened by rotating the tailstock handle and moving the special live center (18). The length of the internal thread of the workpiece (13) after solid-state aging is turned, and the internal thread is checked with a go / no-go gauge. The workpiece (19) is obtained by turning the workpiece at the front groove of the open-type expansion mold (16) with the upper deviation control of the entire length of the workpiece and the inner hole chamfer, according to the control of the entire length. Figure 10 As shown.

[0073] S7. Finish turning the outer diameter of the workpiece. For example... Figure 11 , 12 As shown. The workpiece (19) is screwed into a special fixture (such as one equipped with a serrated polyurethane elastomer material and an annular ring). Figure 11 As shown, this special fixture consists of a flange (20), a body (21), a polyurethane elastomer sealing ring (22), an expansion bearing (23), a pull core (24), a serrated polyurethane elastomer vibration damping ring (25), a threaded support ring (26), and a live center (27). The flange (20) is fixed on the machine tool, the body (21) is fixed on the flange (20), the expansion bearing (23) is placed on the conical surface of the body (21), and the pull core (24) is inserted into the inner hole of the body and connected to the cylinder. The end face of 24) rests on the end face of the cone surface of the body (21). The polyurethane elastomer sealing ring (22) is fitted in the groove of the outer circle of the expansion pad (23). The outer circumference and inner hole of the sawtooth polyurethane elastomer damping ring (25) are provided with sawtooth structure and are inserted on the pull core (24). The workpiece (19) is fitted on the sawtooth polyurethane elastomer damping ring (25) and the expansion pad (23). The threaded support ring (26) is threadedly connected to the end of the workpiece (19). The live center (27) is axially pressed against the threaded support ring (26).

[0074] When using: First, fix the flange (20) on the machine tool, then fix the body (21) on the flange (20), place the expansion pad (23) on the conical surface of the body (21), then insert the pull core (24) into the inner hole of the body and connect it with the cylinder, and turn on the cylinder so that the end face of the pull core (24) is against the end face of the conical surface of the body (21). Then, precision machine the outer diameter of the expansion pad (23) so that the outer diameter of the expansion pad (23) is 0.03-0.05mm larger than the maximum limit size of the inner hole of the workpiece (19) to ensure that the workpiece (19) is in an elastic deformation state after expansion. At this point, the cylinder is closed, causing the core puller (24) to retract and the diameter of the expansion pad (23) to return to the loosened state; then, the polyurethane elastomer sealing ring (22) is placed in the groove of the expansion pad (23), the serrated polyurethane elastomer damping ring (25) is threaded onto the core puller (24), and the workpiece (19) is placed on the serrated polyurethane elastomer damping ring (25) and the expansion pad (23), as follows. Figure 12 As shown; tighten the threaded part of the workpiece (19) with a threaded support ring (26) and axially tighten it with a live center (27).

[0075] After the above operations are completed, the cylinder is opened and the core puller (24) moves forward, so that the expansion bearing (23) is in an expanded state, and the outer diameter of the workpiece (19) is finished.

[0076] The inner diameter of the sawtooth polyurethane elastomer damping ring (25) and the outer diameter of the core (24) have a gap of 0.05mm to 0.07mm; the outer diameter of the sawtooth polyurethane elastomer damping ring (25) and the inner diameter of the high-strength thin-walled aluminum cylinder have a small over-exchange elastic fit of 0.01mm to 0.03mm. This serves to dampen vibrations during the turning of the high-strength thin-walled aluminum cylinder. After the outer diameter of the high-strength thin-walled aluminum cylinder is CNC turned, it is checked with a micrometer. If the roundness is less than 0.03mm, the workpiece (28) can be removed. Figure 13 As shown.

[0077] S8. Finish machining of the inner bore. Screw the clamping sleeve (30) into the internal thread end of the workpiece (28), and then clamp it into the upper tensioning floating cylinder micro-force clamping fixture, such as... Figure 14 , 15 The tensioning type floating support cylinder micro-force clamp consists of a flange (29), a clamping sleeve (30), fastening screws (31), a support plate (32), a pull core shaft (33), a movable pressure plate (34), a rotating pin (35), a body (36), a floating support cylinder (37), a positioning sleeve (38), two end face ball bearings (39), a cylinder body sleeve (40), two circumferential ball bearings (41), a pressure cap (42), two sealing rings (43), an air intake valve (44), and a support sleeve.

[0078] The flange (29) is fixed on the centering shaft of the lathe spindle. Three support plates (32) are fixed on the flange (29) at 120° intervals. One end of the movable pressure plate (34) is hinged to the support plate (32); the other end of the movable pressure plate (34) is hinged to the pull shaft (33). The reciprocating motion of the pull shaft (33) pushing forward and pulling backward drives the movable pressure plate (34) to loosen and tighten the clamping sleeve (30). The clamping sleeve (30) is screwed into the internal thread at the front end of the workpiece (28) and fits against the end face of the workpiece (28). The support sleeve (45) is fixed on the flange (29). The clamping sleeve (38) and the workpiece (28) are positioned; the front end of the body (36) is fixed to the outer ring of the flange (29), the positioning sleeve (38) is fixed to the rear end of the body (36), the cylinder sleeve (40) is fixed inside the positioning sleeve (38), the floating support cylinder (37) is fixed in the equally divided threaded holes in the center hole of the cylinder sleeve (40), the air intake valve (44) is set inside the positioning sleeve (38) and rolls in contact with the end face of the cylinder sleeve (40); the cylinder sleeve (40) has an annular groove that communicates with the air intake hole of the air intake valve (44), and the pressure cap (42) is fixed to the rear end of the positioning sleeve (38).

[0079] In use, first fix the flange (29) on the centering shaft of the lathe spindle. Then, fix the three support plates (32) at 120° intervals to the flange (29) with fastening screws. Connect the movable pressure plate (34) and the support plates (32) with a rotating pin (35). The other end of the movable pressure plate (34) is connected to the pull shaft (33) with a rotating pin (35). The reciprocating motion of the pull shaft (33) pushing forward and pulling backward drives the movable pressure plate (34) to loosen and tighten the clamping sleeve (30). The clamping sleeve (30) screws into the internal thread of the workpiece (28) and fits against the end face of the workpiece (28). Fix the support sleeve (45) to the flange (29) to position the clamping sleeve (38) and the workpiece (28). The main body (36) is fixed to the flange (29) with screws. The positioning sleeve (38) is fixed to the main body (36) with a stop and threads. The cylinder sleeve (40) is fixed to the positioning sleeve (38) with threads. Three floating support cylinders (37) are fixed in the equally spaced 120° threaded holes of the cylinder sleeve (40). The cylinder sleeve (40) has an annular groove that communicates with the air inlet of the intake valve (44). The intake valve (44) is fixed inside the positioning sleeve (38) on the inner ring of two circumferential ball bearings (41) and rolls with the end face bearing (39) on the cylinder sleeve (40). The cylinder sleeve (40) and the intake valve (44) are sealed with two sealing rings (43). The gland (42) is fixed to the positioning sleeve (38) with threads and the intake valve (44) is tightly fitted to the cylinder sleeve (40) through the end face bearing (39). The air inlet valve (44) is a rotating component. The air pipe is connected to the air inlet port of the air inlet valve (44). The floating support cylinder (37) clamps and straightens the workpiece with a small force. There is a small spring inside the floating support rod of the floating support cylinder (37). When it hits the workpiece, the piston inside automatically locks, realizing a small force clamping and ensuring the machining accuracy of the inner hole of the part.

[0080] The inner hole is precision machined to complete all machining processes of the workpiece.

[0081] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for machining high-precision thin-walled aluminum cylindrical parts, characterized in that, Includes the following steps: S1. Material feeding; S2. Roughly machine the outer diameter, end face and inner hole of the blank to obtain a cylindrical part with a stepped hole at one end; S3. Heat treatment is performed on the processed blank (2); S4. Use a powerful spinning tool to machine the outer diameter of the blank in a positive spinning motion; The high-power spinning fixture consists of a connecting body (3), a mandrel (4), a material ejector sleeve (5), three spinning wheels (6), and a locking screw (7). The connecting body (3) is connected to the spindle centering shaft and flange of the high-power spinning equipment. One end of the mandrel (4) is fixedly connected to the connecting body, and the other end is threaded onto the blank and fastened to the locking screw (7). The end of the mandrel is matched with the stepped hole of the blank for positioning. The blank outer diameter is machined by rotating three spinning wheels that are staggered back and forth on the outside of the blank in a forward rotation; annealing is required between spinning passes during the spinning process; S5. Use a special lifting fixture to perform solution aging on the aluminum cylinder (8) after strong rotation; The lifting clamp consists of a folding lifting tool (9), a top cover (10), a material frame (11), and a base (12) with columns. The material frame (11) is placed on the base (12) with columns and connected as a whole. The strongly spun aluminum cylinder (8) is placed inside the material frame (11), and the top cover (10) is inserted into the upper part of the base (12) with columns and connected as a whole with the material frame (11). The folding lifting tool (9) is inserted into the strongly spun aluminum cylinder (8) and clamped. The folding lifting tool (9) mainly consists of a threaded center rod (9-1), a threaded sleeve (9-2), an outer sleeve (9-3), a base plate (9-5), and a support. The system consists of a plate (9-6) and folding rods (9-7); the bottom of the threaded center rod (9-1) is fixedly connected to the support plate (9-6), and multiple sets of folding rods (9-7) are evenly distributed on the outer circumference of the support plate (9-6); each set of folding rods (9-7) is formed by two connecting rods hinged together, one end of the folding rod (9-7) is hinged to the support plate, and the other end is hinged to the outer sleeve (9-3); the threaded sleeve (9-2) is threadedly connected to the center rod (9-1), and the outer sleeve (9-3) is fitted over the threaded sleeve (9-2). The threaded sleeve (9-2) drives the outer sleeve (9-3) to move up and down, and the upper end of the center rod (9-1) is connected to the top cover (10); S6. Perform internal thread and full-length machining on the workpiece after heat treatment aging; S7. Tighten the workpiece on a special fixture equipped with a serrated polyurethane elastomer damping ring, and precision machine the outer diameter of the workpiece. The special fixture consists of a flange (20), a body (21), an expansion bearing (23), a pull core (24), a sawtooth polyurethane elastomer vibration damping ring (25), a threaded support ring (26), and a first live center (27); The flange (20) is fixed on the machine tool, the body (21) is fixed on the flange (20), the expansion bearing (23) is placed on the conical surface of the body (21), the pull core (24) is inserted into the inner hole of the body and connected to the cylinder, the end face of the pull core (24) is pressed against the end face of the conical surface of the body (21), the polyurethane elastomer sealing ring (22) is fitted in the groove of the outer circle of the expansion bearing (23), the serrated polyurethane elastomer damping ring (25) has a serrated structure on its outer circumference and inner hole, and is inserted on the pull core (24), the workpiece is fitted on the serrated polyurethane elastomer damping ring (25) and the expansion bearing (23), the threaded support ring (26) is threadedly connected to the end of the workpiece, and the first live center (27) is axially pressed against the threaded support ring (26); S8. Use a micro-force clamping fixture with an upper tension floating cylinder to precision machine the inner hole of the workpiece; The upper tensioning type floating support cylinder micro-force clamping fixture is composed of a flange (29), a clamping sleeve (30), a pull core shaft (33), a movable pressure plate (34), a body (36), a floating support cylinder (37), a positioning sleeve (38), a cylinder body sleeve (40), a pressure cap (42), and an air inlet valve (44); The flange (29) is fixed on the centering shaft of the lathe spindle. Three support plates (32) are fixed on the flange (29) at 120° intervals. One end of the movable pressure plate (34) is hinged to the support plate (32); the other end of the movable pressure plate (34) is hinged to the pull shaft (33). The reciprocating motion of the pull shaft (33) pushing forward and pulling backward drives the movable pressure plate (34) to release and press the clamping sleeve (30). The clamping sleeve (30) is screwed into the internal thread at the front end of the workpiece (28) and fits against the end face of the workpiece (28). The front end of the body (36) is fixed to the flange. The outer ring of the disc (29) is fixed to the rear end of the body (36), the positioning sleeve (38) is fixed inside the positioning sleeve (38), the floating support cylinder (37) is fixed inside the equally spaced threaded holes in the center hole of the cylinder sleeve (40), the air intake valve (44) is set inside the positioning sleeve (38) and cooperates with the end face of the cylinder sleeve (40), the air intake valve (44) is a rotating part; the cylinder sleeve (40) has an annular groove that communicates with the air intake hole of the air intake valve (44), the pressure cap (42) is fixed to the rear end of the positioning sleeve (38); the floating support cylinder (37) clamps and straightens the workpiece with a small force.

2. The processing method for a high-precision thin-walled aluminum cylinder according to claim 1, characterized in that: In S2, the outer diameter and end face are rough-turned using a double-top machining method, and the outer diameter is ready to be polished; the inner hole is machined using a clamping method with one clamp and one stand.

3. The processing method for a high-precision thin-walled aluminum cylinder according to claim 1, characterized in that: In S2, the outer diameter tolerance is controlled within 0.05mm.

4. The processing method for a high-precision thin-walled aluminum cylinder according to claim 1, characterized in that: In S3, the blank (2) heat treatment state: H112 state annealing, heating to 380 degrees with the furnace, holding for 45 minutes, furnace cooling to 260 degrees, air cooling; adjust the holding time according to the wall thickness of the spun blank.

5. The processing method for a high-precision thin-walled aluminum cylinder according to claim 1, characterized in that: The three wheels are the front wheel, the middle wheel, and the rear wheel. The cone angles of the front wheel and the middle wheel are the same, while the cone angle of the rear wheel is relatively smaller.

6. The processing method for a high-precision thin-walled aluminum cylinder according to claim 5, characterized in that: The cone angles of the front spinning wheel are R8×20°, the middle spinning wheel is R8×20°, and the rear spinning wheel is R6×20°×3°; the hardness of the front, middle, and rear spinning wheels is 60HRC, the misalignment is 4.12 / 3.52 / 0, and the runout is less than 0.

03.

7. The processing method for a high-precision thin-walled aluminum cylinder according to claim 1, characterized in that: The heat treatment method between spinning passes is to raise the temperature to 330°C in the furnace, hold it for 1 hour, cool it in the furnace to 260°C, and then air cool it.

8. The processing method for a high-precision thin-walled aluminum cylinder according to claim 1, characterized in that: The solid-state aging process is as follows: A solid-state furnace is used for heating, with the workpiece suspended in a material frame and subjected to a vertically downward force. The heating temperature is 495–503℃, and the holding time is 40–50 minutes. After the workpiece is removed from the furnace, a 5%–10% sodium chloride aqueous solution is used as the cooling medium, with a medium temperature of 20℃–40℃ and a cooling time of 5 minutes. Artificial aging: An aging furnace is used for heating, with a heating temperature of 185℃–195℃ and a holding time of 8–12 hours. Natural aging: After the workpiece is removed from the furnace, it is left to stand in a workshop at a room temperature of 10℃–15℃ for 96 hours.

9. The processing method for a high-precision thin-walled aluminum cylinder according to claim 1, characterized in that: The internal thread and full length machining of the workpiece after heat treatment and aging are performed using an internal support fixture. The internal support fixture includes an open-type expansion mold (16), a pull rod (14), a three-jaw chuck (15), a polyurethane damping sleeve (17), and a second live center (18). The heat-treated workpiece is inserted into the open-type expansion mold (16) and clamped by the three-jaw chuck (15). The front end of the open-type expansion mold passes through the three-jaw chuck and is positioned in conjunction with the inner tapered hole of the spindle and is fastened to the pull rod (14) to prevent the open-type expansion mold (16) from loosening. A polyurethane damping sleeve (17) is placed at the stepped platform on the rear end face of the open-type expansion mold (16), and a second live center (18) is installed at the tailstock. The end of the second live center has an outer tapered surface. By moving the second live center (18) forward, the three openings of the positioning open-type expansion mold (16) are radially opened to squeeze the heat-treated workpiece.

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