High-precision bushing processing method based on sheet processing

Abstract

The present application belongs to the field of sheet metal forming processing and manufacturing, and relates to a high-precision bushing processing method based on sheet processing. According to the size of the bushing and the plasticity of different materials, a suitable sheet thickness is selected, and the sheet unfolding size is calculated. The preformed expanded raw material is formed into a bushing blank by roll forming. The bushing blank is positioned in a correction die, and effective lubrication is assisted. The hydraulic machine is started, and the part is pushed by the upper die, sequentially passes through the correction rings with multiple accurate sizes embedded in the correction die, and realizes progressive extrusion correction of the part, until the part passes through all the correction rings and falls off from the bottom of the lower die to complete the correction. The present application can replace the machining of bushings. The bushings processed by this method not only have high quality, but also have a material utilization rate of almost 100%. The production efficiency is tens of times that of machining, and the constraints of raw material specifications are completely eliminated.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of sheet metal forming manufacturing, and relates to a high-precision bushing processing method based on sheet processing. BACKGROUND

[0002] Because the bushing has the effects of buffering, supporting, sealing, etc., it can achieve the effects of reducing wear, reducing vibration, reducing noise, and corrosion prevention. At the same time, the bushing itself is convenient to replace after damage, low in cost, and good in economy, and is widely used in various industries. According to different application occasions of the bushing, the types of the bushing materials are also different, and the commonly used materials are soft metals, rubber, nylon, and non-metallic polymers, etc. However, because of the demand for high-precision assembly, the metal bushing has high precision size requirements for the bushing wall thickness, especially the bushing diameter, and usually adopts mechanical processing to ensure the precision. The mechanical processing usually takes a bar as a raw material, and guarantees the precision of the bushing through drilling, turning, grinding, polishing, and heat treatment processes. Obviously, the material utilization rate of the bushing parts is extremely low, and the material utilization rate is further reduced with the increase of the bushing diameter. Moreover, the diameter of the existing bar limits the processing of the large-diameter bushing. If the pipe blank is used to improve the material utilization rate or reduce the processing amount, the performance of part of the pipe blank material cannot meet the use requirements. At the same time, because the bushing wall thickness is relatively thin, the insufficient rigidity of the part itself often causes product deformation and causes over-difference in the processing and heat treatment process. In order to solve the above problems in the machining process of the metal thin-wall bushing, such as low material utilization rate, long processing cycle, unstable quality, and to get rid of the shortage of raw materials caused by the large size of the bushing diameter, a high-precision bushing processing method based on sheet processing is proposed. SUMMARY

[0003] According to the above-mentioned problems in the machining process of the metal thin-wall bushing, such as low material utilization rate, long processing cycle, unstable quality, and to get rid of the shortage of raw materials caused by the large size of the bushing diameter, a high-precision bushing processing method based on sheet processing is proposed to enhance the processing capacity of the thin-wall high-precision bushing, make up for the shortage of raw materials, and provide a new method for processing the thin-wall bushing parts.

[0004] The present application takes a metal sheet as a raw material, calculates the unfolded size according to the part size and the plasticity of different materials, adopts different preforming methods to form the bushing blank by rolling, positions the bushing blank in the correction die, and assists with effective lubrication. In the one-time forming process, the part is pushed by the upper die, sequentially passes through the correction rings with multiple accurate sizes, realizes the progressive extrusion of the part, makes the sheet material gradually produce a small amount of deformation, until the required final size, the part passes through all the correction rings and falls off from the bottom of the lower die. And assisted with turning processing, the trimming of the end face of the bushing is completed.

[0005] Technical solutions of the present application:

[0006] According to the bushing size and the plasticity of different materials, a suitable sheet thickness is selected, and the sheet unfolding size is calculated, and the preforming of the unfolded blank is rolled to form a bushing blank. The bushing blank is positioned in the correction die, and effective lubrication is assisted. The hydraulic machine is started, and the part is pushed by the upper die, sequentially passes through the correction rings with multiple accurate sizes embedded in the correction die, and realizes the progressive extrusion correction of the part, until the part passes through all the correction rings and falls off from the bottom of the lower die to complete the correction. And assisted turning processing is completed to finish the end face of the bushing. Specifically as follows;

[0007] First step: preparation of unfolded blank

[0008] The unfolded blank is the shape and size of the sheet in flat plate state before bending forming. According to the theoretical wall thickness of the bushing part, the thickness of the blank sheet is selected, and according to the different types of materials, the thickness of the blank sheet is 0.1-0.2mm larger than the theoretical wall thickness of the bushing.

[0009] According to the height of the bushing and the diameter of the neutral layer, the unfolded theoretical shape of the bushing is calculated. Considering that the thickness of the sheet blank is larger than the theoretical wall thickness of the bushing, the material is extruded and flows during the forming process, the wall thickness is thinned and the volume is unchanged, which will inevitably produce excess material and increase the surface area. Part of the extruded material flows to the two ends of the open part, and the other part flows along the circumference. If there is no space for material flow along the circumference, it will cause serious extrusion of the material inside, increase the probability of wrinkles and damage. Therefore, when calculating the unfolded length, a certain reduction is needed based on the theoretical unfolded length to leave space for material flow along the circumference, and the end face of the corrected material should be gapless.

[0010] At this point, based on the theoretical bushing wall thickness and the type of material, the thickness of the sheet is determined. Based on the determination of the sheet thickness, according to the principle of constant volume during forming and the proportion of material flow along the longitudinal and circumferential directions, the unfolded size of the sheet blank is determined.

[0011] Second step: preforming rolling

[0012] The preforming rolling is a bridge connecting the unfolded blank and the correction, and good rolling quality is the key to guarantee the correction quality. The rolling method can adopt roll bending, bending, stretch bending, etc., but in order to meet the subsequent correction needs, it is necessary to ensure that the blank does not stretch during rolling, and the upper and lower end faces of the ring are parallel to the axis and perpendicular to the axis.

[0013] The application recommends using winding mode, which can be realized through simple coiling tool. The coiling tool includes die holder, die core, coiling roller and connecting rod. The die holder is located at the lowermost end of the tool and serves to support the entire die. Its shape is a round cake concentric with the circular die core, and its minimum outer diameter needs to be greater than the theoretical outer diameter of the bushing. The die core is seated on the die holder and concentric with the die holder, with a diameter equal to the theoretical inner diameter of the bushing and a height not less than the theoretical height of the bushing. The connecting rod is in the shape of "7", with the short side connected to the center of the die core, the crossbeam connected to the short side and the long side, and the long side connected to the coiling roller at the other end. The coiling roller rolls around the long side, and the gap between the outer surface of the coiling roller and the outer surface of the die core is the thickness of the material. Under the driving of the connecting rod, the coiling roller can rotate around the die core.

[0014] One end of the unfolded raw material is attached to the outer surface of the die core, the end surface of the raw material is tightly attached to the upper surface of the die holder, the coiling roller presses the raw material, and the connecting rod is pushed. The coiling roller revolves around the center of the die under the driving of the connecting rod, and at the same time, the coiling roller rotates around the long side of the connecting rod. While forming extrusion force with the raw material, it rolls relative to the surface of the raw material, minimizing friction and preventing extension along the length of the raw material. Repeated rolling completes the coiling of the unfolded raw material.

[0015] Step 3: Correction

[0016] The correction is the process of correcting the pre-formed coiled circle into a bushing with required wall thickness and diameter through a correction die.

[0017] The correction die is used for hydraulic machine equipment and is divided into upper die and lower die.

[0018] The upper die is divided into upper die plate and convex die. The upper die plate is connected to the platform of the hydraulic machine, and the convex die is installed on the upper die plate. The convex die is in the shape of a stepped cylinder, with a thin lower part and a thick upper part. The lower diameter is equal to the inner diameter of the bushing, and the length is greater than the height of the bushing. The upper diameter of the convex die is slightly smaller than the sum of the lower diameter and twice the material thickness, i.e. the part can be completely fitted into the lower part of the convex die, so that the inner surface of the part is fully supported during the correction process. The upper end of the part is on the stepped end face, and the outer diameter of the part is greater than the upper diameter of the convex die, so that the stepped end face of the upper die can stably push the part downward during the correction process, and the part is sufficiently extruded and corrected without interference from the upper part of the convex die.

[0019] The lower die is divided into a lower die plate, an outer sleeve and a plurality of correction rings. The lower die plate is connected with the platform of the hydraulic machine and supports the outer sleeve and the plurality of correction rings, and a through hole is arranged at the bottom of the lower die plate for leaking out the part after the completion of the overall correction. The outer sleeve is arranged on the lower die plate and has a columnar ring shape, the wall thickness is 15-30 mm, the height can accommodate all the correction rings, the inner diameter is equal to the outer diameter of the correction ring and is in close fit. The outer sleeve has sufficient rigidity and can ensure that the plurality of correction rings are placed in the outer sleeve in the center line coincidence. The plurality of correction rings are annular correction profiles with different inner diameters, and are stacked and placed in the outer sleeve from bottom to top according to the inner diameters from small to large, the outer diameter is in close fit with the inner diameter of the outer sleeve, and the center line is in coincidence with the center lines of the outer sleeve and the punch. The difference between the inner diameters of two adjacent correction rings and the number of the correction rings are determined according to the material type of the part to be corrected and the total correction amount, and the average value of the difference between the inner diameters of two adjacent correction rings is 0.02 mm. The height of the correction ring is generally 20-30 mm, the wall thickness is generally 15-20 mm, the upper and lower end surfaces of each correction ring are chamfered at 45° with the inner diameter, the remaining inner diameter effective correction profile is 2 / 3 of the height of the correction ring, and the chamfered surface is rounded at R3-R5 with the inner diameter. The effective profile roughness of the correction ring is not less than Ra1.6, so as to avoid excessive friction to damage the part.

[0020] The roll circle is completely sleeved into the lower half of the correction die punch, the stepped end surface of the punch abuts against the circumferential surface of the upper end surface of the roll circle, with the downward movement of the upper die, the punch pushes the roll circle into the chamfered surface of the first correction ring, and then into the rounded surface, and further into the second correction ring, and so on, until the last correction ring is corrected and completely separated from the correction ring and leaks out from the through hole of the lower die plate. During the whole processing process, it is necessary to ensure that the part and the die are clean and free of impurities, and sufficient lubrication is provided.

[0021] Step 4: correction

[0022] After the correction is completed, the surface of the bushing is cleaned, and the excess material extruded from both ends of the part is removed by turning. Thus, a high-precision bushing based on sheet metal processing is completed.

[0023] Advantages of the present application:

[0024] The present application can replace the machining of the bushing to a certain extent. The bushing processed by the method has high quality and almost 100% material utilization rate, the production efficiency is dozens of times of the machining, and the original material specifications are completely eliminated. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The figure shows the bushing and the expanded material;

[0026] Figure 2 The schematic view of the coiling tool;

[0027] Figure 3 The schematic view of the correction die.

[0028] Wherein: 1 unwound blank, 2 bushing part, 3 die holder, 4 die core, 5 coiling roller, 6 connecting rod, 7 upper die plate, 8 punch, 9 lower die plate, 10 outer sleeve, 11 multi-stage correction ring, 12 through hole. DETAILED DESCRIPTION

[0029] The present application will be explained below in connection with the drawings and examples so as to be more easily understood.

[0030] The high-precision bushing processing method based on sheet processing has the following steps:

[0031] First step: preparation of unwound blank

[0032] The unwound blank 1 is the shape and size of the plate material before the bushing part 2 is bent and formed into a flat plate. According to the theoretical wall thickness of the bushing part 2, the thickness of the blank sheet is selected, and in this paper, the theoretical thickness of the bushing 2 is selected as 2.5 mm, and the thickness of the blank sheet is selected as 2.6 mm.

[0033] According to the height of the bushing and the diameter of the neutral layer, the unwound theoretical shape of the bushing is calculated. Considering that the thickness of the blank sheet is larger than the theoretical wall thickness of the bushing, and that the material is extruded and flows during the forming process, the wall thickness becomes thinner while the volume remains unchanged, which will inevitably produce excess material and increase the surface area. Part of the extruded material flows to the two ends of the open part, and the other part flows along the circumference. If there is no space for the material to flow along the circumference, the material inside will be severely extruded, increasing the probability of wrinkles and damage. Therefore, when calculating the unwound length, the theoretical unwound length needs to be reduced to some extent to provide space for the material to flow along the circumference, and the corrected material end face needs to be tightly closed without gaps.

[0034] Second step: preforming coiling

[0035] The coiling tool includes a die holder 3, a die core 4, a coiling roller 5, and a connecting rod 6. The die holder 3 is located at the lowermost end of the tool and serves as a support for the entire die. Its shape is a circular cake concentric with the circular die core 4, and its minimum outer diameter needs to be larger than the theoretical outer diameter of the bushing. The die core 4 is seated on the die holder 3 and is concentric with it, with a diameter equal to the theoretical inner diameter of the bushing and a height not less than the theoretical height of the bushing. The connecting rod 6 is in the shape of a "7", with the short side connected to the center of the die core 4, the crossbeam connecting the short side and the long side, and the long side connected to the coiling roller 5 at the other end. The coiling roller 5 revolves around the die core 4 under the drive of the connecting rod 6, with the gap between the outer surface of the coiling roller 5 and the outer surface of the die core 4 being the thickness of the material.

[0036] One end of the spreaded raw material 1 is attached to the outer surface of the mold core 4, the end surface of the raw material is tightly attached to the upper surface of the mold base 3, the round roller 5 presses the raw material, and the connecting rod 6 is pushed. The round roller rotates around the center of the mold under the driving of the connecting rod 6, and at the same time, the round roller 5 rotates around the long edge of the connecting rod 6. At the same time, the round roller 5 forms an extrusion force with the raw material and rolls relative to the surface of the raw material. Repeated rolling completes the rounding of the spreaded raw material 1.

[0037] Step 3: Correction

[0038] The correction mold is used for hydraulic equipment and is divided into an upper mold and a lower mold.

[0039] The upper mold is divided into an upper mold plate 7 and a convex mold 8. The upper mold plate 7 is connected to the platform of the hydraulic machine, and the convex mold 8 is installed on the upper mold plate 7. The convex mold 8 is in the shape of a stepped cylinder as a whole, with a thin lower part and a thick upper part. The diameter of the lower part is equal to the inner diameter of the bushing, and the length is greater than the height of the bushing. The diameter of the upper part of the convex mold 8 is slightly smaller than the sum of the diameter of the lower part and twice the thickness of the material, that is, the part can be completely fitted into the lower part of the convex mold 8, so that the inner surface of the part is fully supported during the correction process. The upper end of the part is in contact with the end surface of the step, and the outer diameter of the part is greater than the diameter of the upper part of the convex mold 8, so that the step end surface of the upper mold can stably push the part downward during the correction process, and the part is sufficiently extruded and corrected without being interfered by the upper part of the convex mold 8.

[0040] The lower mold is divided into a lower mold plate 9, an outer sleeve 10, and a multi-stage correction ring 11. The lower mold plate 9 is connected to the platform of the hydraulic machine and supports the outer sleeve 10 and the multi-stage correction ring 11. The bottom is provided with a through hole 12 through which the part is leaked after being completely corrected. The outer sleeve 10 is seated on the lower mold plate 9 and is in the shape of a cylindrical ring with a wall thickness of 20 mm and a height that can accommodate all the multi-stage correction rings 11. The inner diameter is equal to the outer diameter of the multi-stage correction ring 11. At the same time, it ensures that multiple multi-stage correction rings 11 are placed in the outer sleeve 10 with the center lines coinciding. The multi-stage correction ring 11 is a plurality of annular correction profiles with different inner diameters, stacked from bottom to top according to the inner diameter of the multi-stage correction ring 11 from small to large in the outer sleeve 10. The outer diameter is tightly matched with the inner diameter of the outer sleeve 10, and the center line is coincided with the center line of the outer sleeve 10 and the convex mold 8. The difference between the inner diameters of the adjacent two multi-stage correction rings 11 and the number are determined according to the material type of the corrected part and the total correction amount. Generally, the average difference between the inner diameters of the adjacent two correction rings is 0.02 mm. The height of the multi-stage correction ring 11 is 25 mm, and the wall thickness is 20 mm. The intersection edges of the upper and lower end surfaces and the inner diameter of each multi-stage correction ring 11 need to be chamfered at 45°, and the chamfered surface and the intersection edge of the inner diameter are rounded with a radius of R5, which is beneficial to the smooth entry of the raw material into the next multi-stage correction ring 11 for correction. The effective profile roughness of the multi-stage correction ring 11 is not less than Ra1.6, so as not to damage the part due to excessive friction.

[0041] The lower half of the correction die punch 8 is completely fitted into the roll, and the stepped end face of the punch 8 is in contact with the circumferential surface of the upper end face of the roll. As the upper die moves downward, the punch 8 pushes the roll into the chamfered bevel of the first multi-stage correction ring 11, and then into the rounded surface, and further corrected by the first multi-stage correction ring 11, and then into the chamfered bevel of the second multi-stage correction ring 11, and so on, until the last multi-stage correction ring 11 is corrected, and completely separated from the multi-stage correction ring 11, and leaks out from the lower die plate through hole 12.

[0042] Fourth step: correction

[0043] After the correction is completed, the surface of the bushing is scrubbed clean, and the excess material extruded from both ends of the part is removed by turning.

Claims

1. A high-precision bushing machining method based on sheet machining, characterized by, The steps are as follows: First step: preparation of the spreaded blank The spreaded blank (1) is the shape and size of the bushing part (2) before bending forming, which is in the form of a flat plate; Second step: preforming and coiling The coiling tooling includes a die holder (3), a die core (4), a coiling roller (5) and a connecting rod (6); the die holder (3) is located at the lowermost end of the tooling and serves to support the entire die, and has a shape of a circular cake concentric with the circular die core (4), with the minimum outer diameter being greater than the theoretical outer diameter of the bushing; the die core (4) is seated on the die holder (3) and concentric with the die holder (3), with the diameter being equal to the theoretical inner diameter of the bushing and the height being not less than the theoretical height of the bushing; the connecting rod (6) is in the shape of a "7", with the short side connected to the center of the die core (4), the crossbeam connecting the short side and the long side, and the long side connected to the coiling roller (5) at the other end; the coiling roller (5) rolls around the long side, and the gap between the outer surface of the coiling roller (5) and the outer surface of the die core (4) is the thickness of the material; under the driving of the connecting rod (6), the coiling roller (5) can rotate around the die core (4); One end of the spreaded blank (1) is attached to the outer surface of the die core (4), with the end face of the blank tightly attached to the upper surface of the die holder (3), the coiling roller (5) pressing the blank and pushing the connecting rod (6); the coiling roller rotates around the center of the die under the driving of the connecting rod (6), while the coiling roller (5) rotates around the long side of the connecting rod (6); the blank is extruded by the coiling roller (5) and rolled relative to the surface of the blank; repeated rolling completes the coiling of the spreaded blank (1); Third step: correction The correction die is used for hydraulic machine equipment and is divided into an upper die and a lower die; The upper die is divided into an upper die plate (7) and a male die (8); the upper die plate (7) is connected to the platform of the hydraulic machine, and the male die (8) is installed on the upper die plate (7); the male die (8) is in the shape of a stepped cylinder, with the lower part thin and the upper part thick; the diameter of the lower part is equal to the inner diameter of the bushing, and the length is greater than the height of the bushing; the diameter of the upper part of the male die (8) is slightly smaller than the sum of the diameter of the lower part and twice the thickness of the material, i.e. the part can be completely fitted into the lower part of the male die (8), so that the inner surface of the part is completely supported during the correction process; the upper end of the part is in contact with the end face of the step, and the outer diameter of the part is greater than the diameter of the upper part of the male die (8), so that the step end face of the upper die can stably push the part downward during the correction process, and the part is sufficiently extruded and corrected without being interfered by the upper part of the male die (8); The lower die is divided into a lower die plate (9), an outer sleeve (10) and a multi-stage correction ring (11); the lower die plate (9) is connected to the platform of the hydraulic machine and supports the outer sleeve (10) and the multi-stage correction ring (11), and is provided with a through hole (12) at the bottom for the part to leak out after the correction is completed; The first step: the first step is to put the roll into the lower half of the correction die punch (8), and the step end face of the punch (8) is in contact with the circumference of the upper end face of the roll. As the upper die moves down, the punch (8) pushes the roll into the chamfered slope of the first multi-stage correction ring (11), and then into the rounded surface, and further into the first multi-stage correction ring (11) for correction, and then into the chamfered slope of the second multi-stage correction ring (11), and so on, until the last multi-stage correction ring (11) is corrected and completely separated from the multi-stage correction ring (11), and leaks out from the lower die plate through hole (12); The fourth step: correction After the correction is completed, the surface of the bushing is cleaned by scrubbing, and the excess material extruded from both ends of the part is removed by turning.

2. The high-precision bushing machining method based on sheet machining according to claim 1, characterized by, The height of the multi-stage correction ring (11) is 25mm, and the wall thickness is 20mm. The upper and lower end faces of each multi-stage correction ring (11) and the inner diameter intersecting edge are chamfered at 45°, and the chamfered surface and the inner diameter intersecting edge are rounded R5, which is beneficial to the smooth entry of the raw material into the next multi-stage correction ring (11) for correction.

3. The high-precision bushing machining method based on sheet processing according to claim 1 or 2, characterized by, The multi-stage correction ring (11) is a plurality of annular correction surfaces with different inner diameters, which are stacked from bottom to top according to the size of the inner diameter of the multi-stage correction ring (11) from small to large in the outer sleeve (10), and the outer diameter is tightly matched with the inner diameter of the outer sleeve (10), and the center line is coincident with the center line of the outer sleeve (10) and the punch (8).

4. The high-precision bushing machining method based on sheet processing according to claim 1 or 2, characterized by, The effective surface roughness of the multi-stage correction ring (11) is not less than Ra1.6, so as not to damage the part due to excessive friction.

5. The high-precision bushing machining method based on sheet processing according to claim 3, characterized by, The effective surface roughness of the multi-stage correction ring (11) is not less than Ra1.6, so as not to damage the part due to excessive friction.

6. The high-precision bushing machining method based on sheet processing according to claim 1 or 2 or 5, characterized by, The outer sleeve (10) is located on the lower die plate (9), which is in the shape of a cylindrical ring with a wall thickness of 20mm and a height capable of accommodating all multi-stage correction rings (11). The inner diameter is equal to the outer diameter of the multi-stage correction ring (11); at the same time, it ensures that the center lines of the plurality of multi-stage correction rings (11) coincide when placed in the outer sleeve (10).

7. The high-precision bushing machining method based on sheet machining according to claim 3, characterized by, The outer sleeve (10) is located on the lower die plate (9), which is in the shape of a cylindrical ring with a wall thickness of 20mm and a height capable of accommodating all multi-stage correction rings (11). The inner diameter is equal to the outer diameter of the multi-stage correction ring (11); at the same time, it ensures that the center lines of the plurality of multi-stage correction rings (11) coincide when placed in the outer sleeve (10).

8. The high-precision bushing machining method based on sheet machining according to claim 4, characterized by, The outer sleeve (10) is located on the lower die plate (9), which is in the shape of a cylindrical ring with a wall thickness of 20mm and a height capable of accommodating all multi-stage correction rings (11). The inner diameter is equal to the outer diameter of the multi-stage correction ring (11); at the same time, it ensures that the center lines of the plurality of multi-stage correction rings (11) coincide when placed in the outer sleeve (10).

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