Hot air expansion pipe cutting and positioning method

Abstract

The invention discloses a hot air expansion pipe cutting and positioning method, and belongs to the field of automobile stamping part manufacturing. The method comprises the following steps: arranging a notch as a positioning reference at the end of the hot-gas expansion pipe; the pipe is placed in the clamp and aligned with the notch; the slide rail is pushed by the cylinder, so that the notch props against the positioning point to realize length compensation; an adjustable salient point type supporting point is arranged on the edge of the split chuck or the V-shaped block to support the molded surface of the pipe; magnets are additionally arranged near the salient points for fixing, so that swinging during rotation is prevented; a sensor is installed on the plane of the pipe, and cutting is started after the placing state is detected. According to the method, the problems of thermal deformation, length difference and inconsistent molded surfaces are solved through a cooperative mechanism of notch positioning, salient point supporting and sensor detection, high-precision positioning is achieved, the method is suitable for cutting of A-column, B-column and other thin-wall pipes, the reject ratio is remarkably reduced, and the automation degree and the production efficiency are improved.

Description

Technical Field

[0001] This invention relates to the field of automotive stamping parts manufacturing, specifically to a hot gas expansion tube cutting and positioning method. Background Technology

[0002] Hot gas forming is an advanced metal forming process that uses induction heating to raise the temperature of tubing to over 900°C, then uses high-pressure gas to plastically deform the tubing blank. Finally, cooling and quenching result in ultra-high-strength parts. This technology offers significant advantages in material utilization, springback control, and forming complex closed cross-sections. Compared to traditional cold or hot stamping processes, hot gas forming achieves higher material utilization, typically exceeding 85%, while reducing springback and making dimensional accuracy easier to control. Furthermore, it is particularly suitable for forming parts with complex geometries, such as closed or variable cross-section structures, which are often difficult to achieve or require multiple steps in traditional processes.

[0003] In recent years, with the increasing demand for lightweight vehicles, thermoforming technology has been widely used in the field of automotive safety structural components. For example, it has been adopted by many automakers in key components such as anti-collision beams, A-pillars, and B-pillars. The A-pillar of the Xiaomi YU7 model uses thermoforming technology, achieving higher strength and lighter weight; the pillarless body design of the JiKr MIX model also relies on this technology to ensure the overall rigidity of the body structure and collision safety. These applications not only improve vehicle safety performance but also reduce production costs and energy consumption, driving the automotive manufacturing industry towards intelligent and green development. However, despite significant progress in the forming stage of thermoforming, its subsequent processing steps, especially the cutting and positioning stages, still face several technical challenges. These challenges mainly stem from the thermal deformation behavior of materials at high temperatures and the release of residual stress during the cooling process.

[0004] Specifically, hot gas expansion tubes present challenges in controlling thermal deformation during the cutting process: the radial expansion rate of the tube after heating can reach 0.5%-1.2%, which can cause the preset positioning benchmark to fail, resulting in a deviation in the cutting position. Furthermore, the cooling process after cutting generates a roundness deviation of 0.1-0.5mm, further amplifying dimensional errors. For thin-walled tubes, traditional mechanical clamping methods are prone to indentation or cracking, affecting the surface quality and structural integrity of the parts. These problems not only reduce production efficiency but also increase the scrap rate, hindering the further promotion of hot gas expansion forming technology.

[0005] There are three main types of positioning methods for tubular parts cutting. First, there's the ruler and marking method: a ruler is installed on the feed rack or machine bed, and the operator manually pushes the tube to the predetermined position, possibly with a marker. This is the simplest and most primitive method, suitable for simple parts with low precision requirements, but its error is relatively large, usually above 1-2mm, and significantly affected by human factors. Second, there's the mechanical stop positioning method: an adjustable physical stop is set in the feeding direction. When the end face of the tube abuts the stop, it is considered to have reached the reference position. This method is slightly more accurate than purely manual marking, controlling the error to 0.5-1mm, but the stop needs to be manually adjusted every time the processing length is changed, resulting in low efficiency and inability to adapt to the thermal deformation of the tube. Finally, there's the cylinder combined with mechanical stop positioning method: similar to mechanical stops, but with the addition of a cylinder drive to solve the problem of manual pushing not reaching the correct position, reducing human error. This method has higher precision and is suitable for secondary laser cutting, but it still relies on rigid stops and cannot effectively cope with dynamic changes caused by thermal expansion.

[0006] Existing positioning methods generally employ segmented chucks or V-blocks as clamping devices. This design clashes with thermal expansion forces during part cutting: when parts vary significantly in length and shape, uneven clamping force distribution leads to amplified dimensional deviations and high defect rates. Specific shortcomings include: first, weak length compensation capability, failing to address inconsistent raw material lengths and resulting in inconsistent positioning between preceding and following processes; second, poor cutting adaptability, with V-blocks struggling to provide uniform support for complex parts, easily causing localized deformation; and third, insufficient part placement inspection, preventing operators from visually assessing part placement and increasing the risk of human error. These shortcomings directly lead to low production precision and poor repeatability, amplifying cumulative errors caused by initial tube bending or clamping errors, ultimately affecting the overall quality and reliability of automotive stamping parts. Summary of the Invention

[0007] In view of this, the purpose of this invention is to overcome the shortcomings of the prior art and provide a hot gas expansion tube cutting and positioning method. By introducing a collaborative mechanism of notch-assisted positioning, convex support point positioning, and sensor detection, the functions of length compensation, cutting adaptation, and placement confirmation are achieved.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for cutting and positioning hot gas expansion tubes includes the following steps:

[0010] A notch is set at the end of the hot gas expansion tube as a positioning reference; the hot gas expansion tube is placed in the fixture and aligned with the notch position; the slide rail is pushed by the cylinder so that the notch of the hot gas expansion tube presses against the positioning point to achieve length compensation;

[0011] Protruding support points are set on the side of the split chuck or V-block to support the hot air expansion tube. Magnets are added near the protruding support points to fix the hot air expansion tube and prevent it from swinging during rotation.

[0012] A sensor is installed at the plane of the hot gas expansion tube to detect the placement status, and cutting is started when the sensor indicates that it is in place.

[0013] Furthermore, the notch positioning module works in conjunction with the cylinder to achieve dynamic length compensation by driving the slide rail through the cylinder. The compensation range is 0.5-5mm, the notch depth is 0.5-1.5 times the pipe wall thickness, the width is 2-5mm, the positioning point is set at the end of the slide rail, and adopts a conical or hemispherical structure with a contact surface hardness of HRC50 or higher.

[0014] Furthermore, the convex support point is an adjustable structure, including a threaded adjustment rod and a convex head, with an adjustment accuracy of 0.1mm. It is distributed at key curvature change points on the surface, with at least 3-5 on each side and a spacing of 10-50mm. The height can be adjusted vertically by the threaded rod by 0-10mm.

[0015] Furthermore, the magnet is an adjustable-height electromagnet or permanent magnet with a fixing force range of 5-50N, installed 5-10mm below the convex support point, and the magnetic force direction is perpendicular to the surface of the pipe.

[0016] Furthermore, the sensor is a photoelectric sensor or a proximity sensor with a sensing distance of 1-10mm, located on the planar support platform of the fixture, 1-5mm away from the plane of the pipe, and provides visual or audio-visual feedback.

[0017] Furthermore, during the initial cutting, the position of the protrusions, the height of the magnets, and the sensor sensing distance are adjusted to suit different batches of parts. The adjustment process includes measuring the surface height difference, testing the magnetic strength, and calibrating the sensor threshold.

[0018] Furthermore, the positioning groove of the fixture is located on the horizontal reference plane at the feed end, parallel to the axis of the pipe, and the groove width is 0.1-0.2 mm greater than the pipe diameter to allow for thermal expansion and ensure that the notch is aligned to avoid lateral displacement.

[0019] Furthermore, the method is applied to the field of automotive stamping parts manufacturing, including the cutting of A-pillars, B-pillars or anti-collision beams, and is suitable for thin-walled tubes with a wall thickness range of 0.5-3mm.

[0020] The core technology of this method lies in the coordination between the notch-assisted positioning module and the cylinder, the combination of the convex support point positioning and the magnet, and the placement and detection of the sensor. The connection relationship between the modules is as follows: the notch module achieves dynamic positioning through cylinder drive, the cylinder rod and the slide rail are connected by a pin, and the slide rail moves along the fixture guide rail; the convex support module and the magnet fixing module are integrated on the fixture, and the convex base and the magnet bracket are bolted to provide surface adaptation and stability; the sensor module is independently installed on the plane and connected to the control system through a cable to provide feedback signals and ensure the accuracy and coordination of all positioning positions.

[0021] The beneficial effects of this invention are as follows:

[0022] The hot gas expansion tube cutting and positioning method provided by this invention significantly improves the cutting accuracy and efficiency in automotive stamping parts manufacturing by introducing innovative mechanisms such as notch-assisted positioning, convex support point positioning, and sensor detection. Compared with existing technologies, this method first solves the length compensation problem: traditional methods rely on rigid blocks or manual markings, which cannot adapt to differences in raw material length. In contrast, the notch positioning of this invention, combined with a cylinder-driven slide rail, can dynamically adjust the positioning reference, with a compensation range of 0.5-5mm, ensuring consistency between preceding and following processes and controlling the length error within ±0.1mm. This not only reduces the scrap rate but also improves the flexibility of the production line, making it suitable for the production of multi-variety, small-batch automotive parts.

[0023] Secondly, in terms of cutting adaptation, this invention uses adjustable convex support points instead of traditional V-blocks, avoiding the conflict between clamping force and thermal expansion force. The convex design includes a threaded adjustment rod and a convex head, with an adjustment accuracy of 0.1mm. These are distributed at key curvature change points on the profile, with at least 3-5 on each side and a spacing of 10-50mm. Uniform support is achieved by adjusting the vertical height by 0-10mm, reducing roundness deviation to below 0.05mm. Simultaneously, adjustable-height magnets are added for fixing, with a fixing force range of 5-50N. These magnets are installed 5-10mm below the convex points, with the magnetic force direction perpendicular to the tube surface, further enhancing stability, preventing swaying during rotary table cutting, and ensuring profile consistency. This design improves repeatability, eliminates the influence of initial tube bending or accumulated clamping errors, and reduces the dimensional deviation rate of parts in the same batch to below 1%, far superior to the 5%-10% defect rate of existing technologies.

[0024] Furthermore, the sensor module for part placement detection overcomes the limitations of human vision. Traditional methods rely on operator subjective judgment, which easily leads to placement errors. The sensor in this invention is a photoelectric or proximity sensor with a sensing distance of 1-10mm, located on the clamping support platform, 1-5mm from the tube plane, providing visual or audible feedback to achieve real-time automated confirmation of part placement, reducing human intervention and improving overall automation. Simultaneously, the clamping positioning groove is located on the horizontal reference plane at the feed end, parallel to the tube axis, with a groove width greater than the tube diameter by 0.1-0.2mm to allow for thermal expansion and ensure notch alignment, preventing lateral offset. This method also has universality: through the adjustment process during the initial cutting, including measuring the profile height difference, testing magnetic strength, and calibrating the sensor threshold, it can adapt to different batches of parts, including thin-walled tubes (wall thickness ranging from 0.5-3mm), avoiding the risk of indentation or breakage. This is particularly beneficial in the production of automotive safety structural components such as A-pillars, B-pillars, or crash beams, improving part strength and reliability, and indirectly enhancing vehicle collision safety.

[0025] Overall, this invention achieves improved precision (±0.2mm or higher), good repeatability, and increased automation, reducing production costs (estimated to save 10%-15% in material and labor costs) and broadening the application scope of thermoforming technology. Compared to the limitations of existing technologies, this method innovatively integrates mechanical, magnetic, and sensing technologies to create a synergistic effect, promoting the intelligent transformation of the automotive manufacturing industry and yielding significant economic and social benefits.

[0026] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0028] Figure 1 This is a schematic diagram illustrating the implementation of the hot gas expansion tube cutting and positioning method in this invention.

[0029] Figure 2 for Figure 1 Sectional view of AA.

[0030] Figure 3 for Figure 1 BB section view.

[0031] Figure 4 for Figure 1CC section view.

[0032] Figure 5 for Figure 1 DD section view.

[0033] Figure 6 for Figure 1 EE section view.

[0034] Figure 7 for Figure 1 FF sectional view.

[0035] Reference numerals: 1-pipe; 2-cylinder; 3-sensor display screen; 4-protruding support point; 5-magnet; 6-V-block; 7-notch positioning block; 8-sensor. Detailed Implementation

[0036] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0037] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0038] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0039] Example 1: Cutting the hot air expansion tube of the A-pillar for a certain car model

[0040] Please see Figures 1-7This embodiment provides a hot gas expansion tube cutting and positioning method, including the following arrangement:

[0041] First, a notch is set at the end of the hot gas expansion tube (pipe 1) as a positioning reference. The notch is located on the axial center line of the end face of the pipe, with a depth of 1 times the pipe wall thickness and a width of 3mm, to ensure precise matching with the notch positioning block 7 and avoid lateral displacement.

[0042] Next, place the hot gas expansion tube in the fixture and align it with the notch position. The positioning groove of the fixture is located on the horizontal reference plane at the feed end, parallel to the axis of the tube. The groove width is 0.15mm greater than the tube diameter to allow for thermal expansion margin and ensure that the notch is aligned to avoid lateral displacement.

[0043] Then, cylinder 2 pushes the slide rail, causing the notch after the hot gas expansion tube to abut the positioning point, thus achieving length compensation. This notch positioning module works in conjunction with cylinder 2 to achieve dynamic length compensation by driving the slide rail through the cylinder. The compensation range is 2mm. The positioning point is set at the end of the slide rail and adopts a conical structure with a contact surface hardness of HRC55 to ensure wear resistance and precise engagement with the notch. The cylinder rod is connected to the slide rail by a pin, and the slide rail moves along the clamp guide rail.

[0044] Next, adjustable convex support points 4 are set on the sides of the split chuck or V-block 6 to support the hot gas expansion tube profile. These convex support points 4 are adjustable structures, including threaded adjustment rods and convex heads, with an adjustment accuracy of 0.1mm. They are distributed at key curvature change points of the profile, with 4 convex points on each side, spaced 20mm apart. The height is adjusted vertically by 5mm via the threaded rod to adapt to the profile contour.

[0045] Subsequently, a magnet 5 is added near the convex support point 4 to fix the hot gas expansion tube and prevent it from swaying during rotation. The magnet 5 is an adjustable-height electromagnet with a fixing force range of 20N. It is installed 7mm below the convex support point 4, with the magnetic force direction perpendicular to the surface of the tube 1, and the fixing range covers more than 80% of the profile. The convex support module and the magnet fixing module are integrated on the fixture, and the convex base is bolted to the magnet bracket, providing profile adaptation and stability.

[0046] Next, sensor 8 is installed on the plane of the hot gas expansion tube to detect its placement status. This sensor 8 is a photoelectric sensor with a sensing distance of 5mm. It is located on the flat support platform of the fixture, 3mm away from the plane of the tube, and provides visual feedback (such as a green light indicating to the sensor display screen 3). The sensor module is independently installed on the plane and connected to the control system via a cable to provide feedback signals.

[0047] Finally, during the initial cut, the position of the protrusions, the height of the magnets, and the sensor sensing distance are adjusted to accommodate different batches of parts. The adjustment process includes measuring the surface height difference, testing the magnetic strength, and calibrating the sensor threshold. When the sensor display screen 3 is in position, the rotary table is started for laser cutting.

[0048] This method was applied to the automotive stamping parts manufacturing industry and is suitable for thin-walled tubing with a wall thickness range of 0.5-3mm. Results: Positioning accuracy reached ±0.15mm, defect rate was less than 0.5%, and it is suitable for A-pillar production.

[0049] Example 2: For a certain brand of pipe without B-pillar (wall thickness 1.5mm)

[0050] Please see Figures 1-7 This embodiment provides a hot gas expansion tube cutting and positioning method, including the following steps:

[0051] First, a notch is set at the end of the hot gas expansion tube (pipe 1) as a positioning reference. The notch is located on the axial center line of the end face of the pipe, with a depth of 0.8 times the pipe wall thickness and a width of 4 mm, to ensure precise matching with the notch positioning block 7 and avoid lateral displacement.

[0052] Next, place the hot gas expansion tube in the fixture and align it with the notch position. The positioning groove of the fixture is located on the horizontal reference plane at the feed end, parallel to the tube axis. The groove width is 0.2mm wider than the tube diameter to allow for thermal expansion margin and ensure that the notch is aligned to avoid lateral displacement.

[0053] Then, cylinder 2 pushes the slide rail, causing the notch after the hot gas expansion tube to abut the positioning point, thus achieving length compensation. This notch positioning module works in conjunction with cylinder 2 to achieve dynamic length compensation by driving the slide rail through the cylinder. The compensation range is 3mm. The positioning point is set at the end of the slide rail and adopts a hemispherical structure with a contact surface hardness of HRC52 to ensure wear resistance and precise engagement with the notch. The cylinder rod is connected to the slide rail by a pin, and the slide rail moves along the clamp guide rail.

[0054] Next, adjustable convex support points 4 are set on the sides of the split chuck or V-block 6 to support the hot gas expansion tube profile. These convex support points 4 are adjustable structures, including threaded adjustment rods and convex heads, with an adjustment accuracy of 0.1mm. They are distributed at key curvature change points of the profile, with 5 convex points on each side and a spacing of 15mm. The height is adjusted vertically by 8mm via the threaded rod to adapt to the profile contour.

[0055] Subsequently, a magnet 5 is added near the convex support point 4 to fix the hot gas expansion tube and prevent it from swaying during rotation. The magnet 5 is an adjustable-height permanent magnet with a fixing force range of 30N. It is installed 8mm below the convex support point 4, with the magnetic force direction perpendicular to the surface of the tube 1, and the fixing range covers more than 80% of the profile. The convex support module and the magnet fixing module are integrated on the fixture, and the convex base is bolted to the magnet bracket, providing profile adaptation and stability.

[0056] Next, sensor 8 is installed on the plane of the hot gas expansion tube to detect its placement status. This sensor 8 is a proximity sensor with a sensing distance of 3mm. It is located on the flat support platform of the fixture, 2mm away from the plane of the tube, and provides audible and visual feedback (such as an indication to the sensor display screen 3). The sensor module is independently installed on the plane and connected to the control system via a cable to provide feedback signals.

[0057] Finally, during the initial cut, the position of the protrusions, the height of the magnets, and the sensor sensing distance are adjusted to accommodate different batches of parts. The adjustment process includes measuring the surface height difference, testing the magnetic strength, and calibrating the sensor threshold. When the sensor display screen 3 is in position, the rotary table is started for laser cutting.

[0058] This method is applied in the automotive stamping parts manufacturing industry and is suitable for thin-walled tubes with a wall thickness range of 0.5-3mm. Results: Repeatability error is less than 0.1mm, suitable for the production of tubes without B-pillars, with no indentations or cracks.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for cutting and positioning hot gas expansion tubes, characterized in that, Includes the following steps: A notch is set at the end of the hot gas expansion tube as a positioning reference; the hot gas expansion tube is placed in the fixture and aligned with the notch position; the slide rail is pushed by the cylinder so that the notch of the hot gas expansion tube presses against the positioning point to achieve length compensation; Protruding support points are set on the edge of the split chuck or V-block to support the hot gas expansion tube profile. Magnets are added near the convex support points to fix the hot air expansion tube and prevent it from swaying during rotation; A sensor is installed at the plane of the hot gas expansion tube to detect the placement status, and cutting is started when the sensor indicates that it is in place.

2. The method according to claim 1, characterized in that, The notch positioning module works in conjunction with the cylinder to achieve dynamic length compensation by driving the slide rail through the cylinder. The compensation range is 0.5-5mm, the notch depth is 0.5-1.5 times the pipe wall thickness, the width is 2-5mm, the positioning point is set at the end of the slide rail, and adopts a conical or hemispherical structure with a contact surface hardness of HRC50 or higher.

3. The method according to claim 1, characterized in that, The convex support points are adjustable structures, including threaded adjustment rods and convex heads, with an adjustment accuracy of 0.1mm. They are distributed at key curvature change points on the surface, with at least 3-5 on each side and a spacing of 10-50mm. The height can be adjusted vertically by 0-10mm via the threaded rod.

4. The method according to claim 1, characterized in that, The magnet is an adjustable-height electromagnet or permanent magnet with a fixing force range of 5-50N. It is installed 5-10mm below the convex support point, and the magnetic force direction is perpendicular to the surface of the pipe.

5. The method according to claim 1, characterized in that, The sensor is a photoelectric sensor or a proximity sensor with a sensing distance of 1-10mm. It is located on the flat support platform of the fixture, 1-5mm away from the plane of the pipe, and provides visual or audio-visual feedback.

6. The method according to claim 1, characterized in that, During the initial cutting, the position of the protrusions, the height of the magnets, and the sensing distance of the sensor are adjusted to accommodate different batches of parts. The adjustment process includes measuring the surface height difference, testing the magnetic strength, and calibrating the sensor threshold.

7. The method according to claim 1, characterized in that, The positioning groove of the clamp is located on the horizontal reference plane at the feed end, parallel to the axis of the pipe. The groove width is 0.1-0.2 mm wider than the pipe diameter to allow for thermal expansion and ensure that the notch is aligned to avoid lateral displacement.

8. The method according to claim 1, characterized in that, The method is applied in the field of automotive stamping parts manufacturing, including the cutting of A-pillars, B-pillars or anti-collision beams, and is suitable for thin-walled tubes with a wall thickness range of 0.5-3mm.

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