High-precision lining machining method based on thin plate machining

Abstract

The invention belongs to the field of sheet metal forming, machining and manufacturing, and relates to a high-precision lining machining method based on sheet machining. According to the size of the lining and the plasticity of different materials, the appropriate thickness of a thin plate is selected, the unfolding size of the plate is calculated, and the unfolded blank is pre-formed and rolled to form a lining blank. And the lining blank is positioned in a correcting die, and meanwhile effective lubrication is supplemented. The hydraulic machine is started, the part is pushed by the upper die to sequentially pass through the correction rings which are embedded in the correction die and have a plurality of accurate sizes, progressive extrusion correction of the part is achieved till the part penetrates through all the correction rings and falls off from the bottom of the lower die, and correction is completed. The method can replace a machined bush, the bush machined through the method is too hard, the material utilization rate is almost 100%, the production efficiency is tens of times that of machining, and the constraint of the specification of raw materials is completely eliminated.

Description

Technical Field

[0001] The invention belongs to the field of sheet metal forming processing and manufacturing, and relates to a high-precision bushing processing method based on thin plate processing. Background Art

[0002] Because the bushing has the functions of buffering, supporting, sealing, etc., it can reduce wear, slow down vibration, reduce noise and prevent corrosion. At the same time, the bushing itself is easy to replace after damage, low cost and good economy, and is widely used in various industries. According to the different occasions of bushing application, the types of bushing materials are also different. Commonly used materials are soft metals, rubber, nylon and non-metallic polymers. Metal bushings require high-precision assembly, so high-precision dimensions are required for bushing wall thickness, especially bushing diameter, which are often guaranteed by mechanical processing. Machining usually uses rods as raw materials, and the accuracy of bushings is guaranteed through drilling, turning, grinding, polishing, heat treatment and other processes. Obviously, the material utilization rate of bushing parts is extremely low, and as the diameter of the bushing increases, the material utilization rate further decreases. Moreover, the diameter of the existing rods limits the processing of large-diameter bushings. If pipe blanks are used to improve material utilization or reduce processing volume, the material performance of some pipe blanks cannot meet the use requirements. At the same time, because the bushing wall thickness is relatively thin, the lack of rigidity of the parts themselves during processing and heat treatment often causes product deformation and out-of-tolerance. In order to solve the problems of low material utilization, long processing cycle and unstable quality in the machining process of the above-mentioned metal thin-walled bushings, and to get rid of the current situation of raw material shortage due to the excessive diameter of the bushing, a high-precision bushing processing method based on thin plate processing is proposed. Summary of the invention

[0003] According to the above-mentioned metal thin-walled bushing machining process with low material utilization rate, long processing cycle and unstable quality, and at the same time getting rid of the current situation of raw material shortage due to the large bushing diameter, a high-precision bushing processing method based on thin plate processing is proposed to enhance the processing capability of thin-walled high-precision bushings, make up for the shortage of raw materials, and provide a new method for the processing of thin-walled bushing parts.

[0004] The present invention uses a metal sheet as raw material, calculates the unfolded size according to the size of the part and the plasticity of different materials, and uses different preforming methods to roll it into a bushing blank. The bushing blank is positioned in the correction die, and effective lubrication is provided. In the one-time forming process, the part is pushed by the upper die and sequentially passes through correction rings with multiple precise sizes to achieve progressive extrusion of the part, so that the sheet material gradually produces a slight deformation until the required final size, the part passes through all correction rings and falls off from the bottom of the lower die. And turning is used to complete the trimming of the bushing end face.

[0005] The technical solution of the present invention:

[0006] According to the bushing size and the plasticity of different materials, select the appropriate sheet thickness, calculate the unfolded size of the sheet, preform the unfolded raw material and roll it into a bushing blank. Position the bushing blank in the correction die and provide effective lubrication. Start the hydraulic press, and the part, pushed by the upper die, passes through the correction rings with multiple precise sizes embedded in the correction die in turn, to achieve 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 with the assistance of turning, complete the trimming of the bushing end face. The details are as follows;

[0007] Step 1: Preparation of wool material

[0008] The unfolded rough material is the shape and size of the plate material in a flat state before bending. The rough material sheet thickness is selected according to the theoretical wall thickness of the bushing part. According to different material types, the rough material sheet thickness is 0.1 to 0.2 mm greater than the theoretical wall thickness of the bushing.

[0009] The theoretical shape of the bushing is calculated based on the height of the bushing and the diameter of the neutral layer. Considering that the thickness of the thin plate is greater than the theoretical wall thickness of the bushing, the material is squeezed and flows during the forming process, and 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 open ends of the part, and the other part flows along the circumference. If there is no flow space in the circumference direction, the material will be severely squeezed inside, and the probability of wrinkling and breakage will increase. Therefore, when calculating the unfolded length, it is necessary to make a certain reduction on the basis of the theoretical unfolded length to leave space for the material flow along the circumference direction, and the end faces of the corrected material must be aligned without gaps.

[0010] At this point, the determination of the sheet thickness is completed based on the theoretical bushing wall thickness and material type. On the basis of determining the sheet thickness, the sheet rough material development size is determined based on the principle of constant volume during the forming process and the proportion of material flow in the longitudinal and circumferential directions.

[0011] Step 2: Pre-forming and rolling

[0012] The preformed curling is a bridge between the unfolding of the raw material and the correction. Good curling quality is the key to ensuring the correction quality. The curling method can be rolling, bending, stretching, etc., but in order to meet the needs of subsequent correction, it is necessary to ensure that the raw material does not extend during the curling process, and the upper and lower end surfaces of the ring are parallel and perpendicular to the axis.

[0013] The present invention recommends the use of a bending method, which can be achieved through a simple rolling tool. The rolling tool includes a mold base, a mold core, a rolling roller and a connecting rod. The mold base is located at the bottom of the tooling, and plays a role in supporting the entire mold. Its appearance is a round pancake concentric with the circular mold core, and the minimum outer diameter must be larger than the theoretical outer diameter of the bushing. The mold core is located on the mold base and is concentric with the mold base. The diameter is equal to the theoretical inner diameter of the bushing, and the height is not less than the theoretical height of the bushing. The connecting rod is in the shape of a "7" as a whole, with the short side connected to the center of the mold core, the crossbeam connecting the short side and the long side, and the other end of the long side is connected to the rolling roller. The rolling roller rolls around the long side as the center, and the gap between the outer surface of the rolling roller and the outer surface of the mold core is the material thickness. Driven by the connecting rod, the rolling roller can rotate around the mold core.

[0014] One end of the unfolded material is attached to the outer surface of the mold core, the end face of the material is in close contact with the upper surface of the mold base, the rolling roller presses the material and pushes the connecting rod. The roller rotates around the center of the mold driven by the connecting rod. At the same time, the rolling roller rotates around the long side of the connecting rod, while forming an extrusion force with the material and rolling relative to the surface of the material to reduce friction as much as possible and prevent the extension along the length direction of the material. Repeated rolling completes the curling of the unfolded material.

[0015] Step 3: Calibration

[0016] The correction is a process of correcting the preformed curl into a bushing with a wall thickness and a diameter that meet the requirements through a correction die.

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

[0018] The upper die is divided into an upper die plate and a punch. The upper die plate is connected to the hydraulic press platform, and the punch is installed on the upper die plate. The punch is a stepped cylindrical shape, thin at the bottom and thick at the top. 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 punch is slightly smaller than the sum of the lower diameter and 2 times the material thickness, that is, the part can be completely inserted into the lower part of the punch, so that the inner surface of the part is fully supported during the correction process. The upper end of the part is against the end face of the step, and the outer diameter of the part is greater than the upper diameter of the punch, so that during the correction process, the stepped end face of the upper die can stably push the part down, and the part is fully extruded and corrected without interference from the upper part of the punch.

[0019] The lower die is divided into a lower die plate, an outer sleeve and a multi-stage correction ring. The lower die plate is connected to the hydraulic press platform and supports the outer sleeve and the multi-stage correction ring. A through hole is provided at the bottom, through which the parts can be leaked after all corrections are completed. The outer sleeve is located on the lower die plate. It is in the shape of a cylindrical ring with a wall thickness of 15 to 30 mm. The height can fit all the correction rings. The inner diameter is equal to the outer diameter of the correction ring and fits tightly. It has sufficient rigidity and ensures that the center lines of multiple correction rings placed in the outer sleeve coincide. The multi-stage correction ring is a plurality of annular correction surfaces with different inner diameters. From bottom to top, they are stacked one by one in the outer sleeve according to the inner diameter of the correction ring from small to large. Its outer diameter is closely matched with the inner diameter of the outer sleeve, and its center line coincides with the center line of the outer sleeve and the punch. The difference between the inner diameters of two adjacent correction rings and the number of correction rings are determined according to the type of material of the corrected part and the total correction amount. The average difference between the inner diameters of two adjacent correction rings of general materials is 0.02 mm. The height of the correction ring is generally 20-30mm, and the wall thickness is generally 15-20mm. The edges where the upper and lower end faces of each level of correction ring intersect with the inner diameter must be chamfered 45°. The remaining inner diameter effective correction profile is 2 / 3 of the correction ring height. The chamfered surface and the inner diameter intersection edges must be rounded R3-R5, which is conducive to the smooth entry of the raw material into the next correction ring for correction. The roughness of the effective profile of the correction ring should not be less than Ra1.6 to avoid excessive friction and damage to the parts.

[0020] The rolled circle is completely inserted into the lower half of the correction die punch, so that the stepped end face of the punch bears against the circumference of the upper end face of the rolled circle. As the upper die moves downward, the punch pushes the rolled circle into the chamfered slope of the first correction ring, and then into the chamfered surface, and further corrected by the first correction ring, and then enters the chamfered slope of the second correction ring, and so on, until the last correction ring is corrected, and completely separated from the correction ring, leaking out from the through hole of the lower die plate. During the entire processing process, it is necessary to ensure that the parts and the mold are clean and free of impurities, and supplemented with sufficient lubrication.

[0021] Step 4: Correction

[0022] After the correction is completed, the surface of the bushing is cleaned and the excess material squeezed out at both ends of the part is removed by turning. At this point, a high-precision bushing processing based on thin plate processing is completed.

[0023] Beneficial effects of the present invention:

[0024] The present invention can replace the machined bushing to a certain extent. The bushing processed by this method is not only of high quality, but also has a material utilization rate of almost 100%, a production efficiency that is dozens of times that of machining, and is completely free from the constraints of raw material specifications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the bushing and the unfolded wool;

[0026] Figure 2 It is a schematic diagram of the rolling tooling;

[0027] Figure 3 Schematic diagram of the calibration model.

[0028] Among them: 1 unfolded raw material, 2 bushing parts, 3 die base, 4 die core, 5 roll, 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 invention is explained below with reference to figures and examples for easier understanding.

[0030] High-precision bushing processing method based on thin plate processing, the steps are as follows:

[0031] Step 1: Preparation of wool material

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

[0033] The theoretical shape of the bushing is calculated based on the height of the bushing and the diameter of the neutral layer. Considering that the thickness of the thin plate is greater than the theoretical wall thickness of the bushing, the material is squeezed and flows during the forming process, and 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 open ends of the part, and the other part flows along the circumference. If there is no flow space in the circumference direction, the material will be severely squeezed inside, and the probability of wrinkling and breakage will increase. Therefore, when calculating the unfolded length, it is necessary to make a certain reduction on the basis of the theoretical unfolded length to leave space for the material flow along the circumference direction, and the end faces of the corrected material must be aligned without gaps.

[0034] Step 2: Pre-forming and rolling

[0035] The rolling tooling consists of a die base 3, a mold core 4, a rolling roller 5 and a connecting rod 6. The die base 3 is located at the bottom of the tooling and plays a role in supporting the entire mold. Its shape is a round pancake concentric with the circular mold core 4, and the minimum outer diameter must be larger than the theoretical outer diameter of the bushing. The mold core 4 is located on the die base 3 and is concentric with the die base 3. The diameter is equal to the theoretical inner diameter of the bushing, and the height is not less than the theoretical height of the bushing. The connecting rod 6 is in the shape of a "7" as a whole, with the short side connected to the center of the mold core 4, the crossbeam connecting the short side and the long side, and the other end of the long side connected to the rolling roller 5. The rolling roller 5 rolls around the long side, and the gap between the outer surface of the rolling roller 5 and the outer surface of the mold core 4 is the material thickness. Driven by the connecting rod 6, the rolling roller 5 can rotate around the mold core 4.

[0036] One end of the unfolded material 1 is attached to the outer surface of the mold core 4, the end surface of the material is in close contact with the upper surface of the mold base 3, the rolling roller 5 presses the material and pushes the connecting rod 6, the roller rotates around the center of the mold driven by the connecting rod 6, and the rolling roller 5 rotates around the long side of the connecting rod 6, while forming an extrusion force with the material and rolling relative to the surface of the material. Repeated rolling completes the rolling of the unfolded material 1.

[0037] Step 3: Calibration

[0038] The correction die is used in hydraulic press equipment and is divided into an upper die and a lower die.

[0039] The upper die is divided into an upper die plate 7 and a punch 8. The upper die plate 7 is connected to the hydraulic press platform, and the punch 8 is installed on the upper die plate 7. The punch 8 is a stepped cylindrical shape as a whole, 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 punch 8 is slightly smaller than the sum of the lower diameter and twice the material thickness, that is, the part can be completely inserted into the lower part of the punch 8, so that the inner surface of the part is fully supported during the correction process. The upper end of the part is against the end face of the step, and at the same time, the outer diameter of the part is greater than the upper diameter of the punch 8, so that during the correction process, the stepped end face of the upper die can stably push the part downward, and the part is fully extruded and corrected without interference from the upper part of the punch 8.

[0040] 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 hydraulic press platform and supports the outer sleeve 10 and the multi-stage correction ring 11. A through hole 12 is provided at the bottom, through which the parts can be leaked after all corrections are completed. The outer sleeve 10 is located on the lower die plate 9. It is in the shape of a cylindrical ring with a wall thickness of 20 mm. The height can fit 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 is ensured that the center lines of multiple multi-stage correction rings 11 placed in the outer sleeve 10 coincide. The multi-stage correction ring 11 is a plurality of annular correction surfaces with different inner diameters. From bottom to top, they are stacked one by one according to the inner diameter of the multi-stage correction ring 11 from small to large and placed in the outer sleeve 10. Its outer diameter is closely matched with the inner diameter of the outer sleeve 10, and its center line coincides with the center line of the outer sleeve 10 and the punch 8. The difference and number of inner diameters of two adjacent multi-stage correction rings 11 are determined according to the material type of the corrected parts and the total correction amount. The average difference of the inner diameters of two adjacent correction rings of general materials is 0.02mm. The height of the multi-stage correction ring 11 is 25mm, and the wall thickness is 20mm. The edges where the upper and lower end faces of each multi-stage correction ring 11 intersect with the inner diameter must be chamfered 45°, and the edges where the chamfered surface intersects with the inner diameter must be rounded R5, which is conducive to the smooth entry of the raw material into the next multi-stage correction ring 11 for correction. The effective surface roughness of the multi-stage correction ring 11 is not less than Ra1.6 to avoid excessive friction and damage to the parts.

[0041] The rolled circle is completely inserted into the lower half of the correction die punch 8, so that the stepped end face of the punch 8 presses against the circumference of the upper end face of the rolled circle. As the upper die moves downward, the punch 8 pushes the rolled circle into the chamfered surface of the first multi-stage correction ring 11, and then into the chamfered surface, and is further corrected by the first multi-stage correction ring 11, and then enters the chamfered surface of the second multi-stage correction ring 11, and progresses in sequence until the correction of the last multi-stage correction ring 11 is completed, and it is completely separated from the multi-stage correction ring 11 and leaks out from the through hole 12 of the lower template.

[0042] Step 4: Correction

[0043] After the correction is completed, the bushing surface is cleaned and the excess material squeezed out at both ends of the part is removed by turning.

Claims

1. A high-precision bushing processing method based on thin plate processing, characterized in that: Here are the steps: Step 1: Preparation of wool material The unfolded rough material (1) is the shape and size of the sheet material in a flat state before the bushing part (2) is bent and formed; Step 2: Pre-forming and rolling The rolling tooling comprises a die base (3), a die core (4), a rolling roller (5) and a connecting rod (6); the die base (3) is located at the bottom end of the tooling and plays a role in supporting the entire die. Its outer shape is a round cake shape concentric with the circular die core (4), and the minimum outer diameter dimension must be greater than the theoretical outer diameter of the bushing; the die core (4) is located on the die base (3) and is concentric with the die base (3), and its diameter is equal to the theoretical inner diameter of the bushing, and its height is not less than the theoretical height of the bushing; the connecting rod (6) is in the shape of a "7" as a whole, 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 other end of the long side connected to the rolling roller (5), the rolling roller (5) rolling around the long side as the center, and the gap between the outer surface of the rolling roller (5) and the outer surface of the die core (4) is the material thickness; driven by the connecting rod (6), the rolling roller (5) can rotate around the die core (4); One end of the unfolded raw material (1) is fitted to the outer surface of the mold core (4), the end face of the raw material is tightly attached to the upper surface of the mold base (3), the rolling roller (5) presses the raw material and pushes the connecting rod (6), the roller rotates around the center of the mold under the drive of the connecting rod (6), and at the same time, the rolling roller (5) rotates around the long side of the connecting rod (6), while forming an extrusion force with the raw material and rolling relative to the surface of the raw material; repeated rolling completes the rolling of the unfolded raw material (1); Step 3: Calibration The correction die is used for hydraulic press equipment and is divided into upper die and lower die; The upper die is divided into an upper die plate (7) and a punch (8); the upper die plate (7) is connected to the hydraulic press platform, and the punch (8) is installed on the upper die plate (7); the punch (8) is in the shape of a stepped cylinder, with a thin lower portion and a thick upper portion; the lower portion has a diameter equal to the inner diameter of the bushing, and a length greater than the height of the bushing; the upper portion diameter of the punch (8) is slightly smaller than the sum of the lower portion diameter and twice the material thickness, that is, the part can be completely inserted into the lower portion of the punch (8), so that the inner surface of the part is fully supported during the correction process; the upper end of the part is against the end face of the step, and the outer diameter of the part is greater than the upper diameter of the punch (8), so that during the correction process, the stepped end face of the upper die can stably push the part downward, and the part is fully extruded and corrected without being interfered by the upper portion of the punch (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 hydraulic press platform and supports the outer sleeve (10) and the multi-stage correction ring (11), and a through hole (12) is provided at the bottom, through which the parts can be leaked after all corrections are completed; The rolled circle is completely inserted into the lower half of the correction die punch (8), so that the stepped end face of the punch (8) bears against the circumference of the upper end face of the rolled circle. As the upper die moves downward, the punch (8) pushes the rolled circle into the chamfered slope of the first multi-stage correction ring (11), and then into the chamfered profile, and is further corrected by the first multi-stage correction ring (11), and then enters the chamfered slope of the second multi-stage correction ring (11), and so on, until the correction of the last multi-stage correction ring (11) is completed, and the rolled circle is completely separated from the multi-stage correction ring (11) and leaks out from the through hole (12) of the lower die plate; Step 4: Correction After the correction is completed, the bushing surface is cleaned and the excess material squeezed out at both ends of the part is removed by turning.

2. The high-precision bushing processing method based on thin plate processing according to claim 1 is characterized in that: The height of the multi-stage correction ring (11) is 25 mm, the wall thickness is 20 mm, the edges where the upper and lower end faces of each multi-stage correction ring (11) intersect with the inner diameter need to be chamfered by 45°, and the edges where the chamfered surface intersects with the inner diameter are rounded by R5, which is conducive to the smooth entry of the raw material into the next multi-stage correction ring (11) for correction.

3. The high-precision bushing processing method based on thin plate processing according to claim 1 or 2, characterized in that: The multi-stage correction ring (11) is a plurality of annular correction surfaces with different inner diameters, which are stacked one by one from bottom to top in accordance with the inner diameters of the multi-stage correction rings (11) from small to large and placed in the outer sleeve (10), and their outer diameters are closely matched with the inner diameters of the outer sleeve (10), and their center lines coincide with the center lines of the outer sleeve (10) and the punch (8).

4. The high-precision bushing processing method based on thin plate processing according to claim 1 or 2, characterized in that: The effective surface roughness of the multi-stage correction ring (11) is not less than Ra1.6 to prevent excessive friction from damaging parts.

5. The high-precision bushing processing method based on thin plate processing as claimed in claim 3, characterized in that: The effective surface roughness of the multi-stage correction ring (11) is not less than Ra1.6 to prevent excessive friction from damaging parts.

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

7. The high-precision bushing processing method based on thin plate processing as claimed in claim 3 is characterized in that: The outer sleeve (10) is located on the lower template (9) and is in the shape of a cylindrical ring with a wall thickness of 20 mm and a height capable of housing all the multi-stage correction rings (11). The inner diameter is equal to the outer diameter of the multi-stage correction rings (11); at the same time, it is ensured that the center lines of the multiple multi-stage correction rings (11) placed in the outer sleeve (10) coincide.

8. The high-precision bushing processing method based on thin plate processing according to claim 4 is characterized in that: The outer sleeve (10) is located on the lower template (9) and is in the shape of a cylindrical ring with a wall thickness of 20 mm and a height capable of housing all the multi-stage correction rings (11). The inner diameter is equal to the outer diameter of the multi-stage correction rings (11); at the same time, it is ensured that the center lines of the multiple multi-stage correction rings (11) placed in the outer sleeve (10) coincide.

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