A numerical control welding workbench for automobile sheet metal parts and a welding method thereof

Abstract

The application discloses a numerical control welding workbench for automobile sheet metal parts, which comprises a workbench body, a servo motor fixedly installed on the workbench body, a driving shaft rotatably inserted into the workbench body, an output end of the servo motor fixedly connected with the driving shaft, a first synchronous wheel fixedly sleeved with an end of the driving shaft away from the servo motor, a first supporting plate fixedly installed on the workbench body, a second supporting plate slidably arranged on the workbench body, and rotating tooling discs rotatably arranged on the first supporting plate and the second supporting plate. The second supporting plate is driven by the pneumatic guide rail to slide, the interval between the two rotating tooling discs can be flexibly adjusted, the automobile sheet metal parts with different lengths and sizes can be adapted, meanwhile, the workpiece clamping plate is driven by the telescopic rod to cooperate with the workpiece supporting plate, the precise clamping of the sheet metal part is realized, the operation is convenient, and the universality and the use convenience of the device are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of welding equipment technology, specifically relating to a CNC welding workbench for automotive sheet metal parts and its welding method. Background Technology

[0002] In the automotive manufacturing industry, the welding quality of sheet metal parts is directly related to the strength and precision of the car body.

[0003] Traditional welding methods are mainly divided into manual welding and semi-automatic tooling welding.

[0004] Manual welding relies on operators manually flipping the workpiece, which is labor-intensive, inefficient, and difficult to guarantee consistency.

[0005] While semi-automatic tooling welding has shown some improvement, it still has significant shortcomings: the spacing between tooling discs is mostly fixed or can only be adjusted manually, making it time-consuming and labor-intensive to adapt to workpieces of different sizes, resulting in poor versatility; clamping often relies on manual bolt tightening, which is inconvenient to operate and prone to positioning misalignment; most of these toolings do not have automatic synchronous rotation functions, requiring repeated machine stops and manual flipping during welding, significantly increasing auxiliary time, and re-clamping can easily introduce deviations, affecting weld accuracy and forming quality; at the same time, some tooling structures are thin and lack rigidity during continuous operation, easily generating vibration, affecting welding stability and shortening equipment life. Summary of the Invention

[0006] The purpose of this invention is to provide a CNC welding worktable for automotive sheet metal parts to solve the problems mentioned in the background art.

[0007] In a first aspect, the present invention provides a CNC welding worktable for automotive sheet metal parts, comprising: The worktable body has a servo motor fixedly mounted on it, a drive shaft rotatably inserted into it, the output end of the servo motor fixedly connected to the drive shaft, a first synchronous wheel fixedly sleeved on the end of the drive shaft away from the servo motor, a first support plate fixedly mounted on it, a second support plate slidably mounted on it, a rotating tooling disk rotatably mounted on both the first and second support plates, a driven shaft fixedly mounted on the rotating tooling disk of the first support plate, a second synchronous wheel fixedly sleeved on the driven shaft, a workpiece support plate fixedly mounted on the rotating tooling disk, and a workpiece clamping plate slidably mounted on the rotating tooling disk.

[0008] In one possible implementation of the first aspect, the rotating tooling disk is provided with a telescopic rod, the output end of which is fixedly connected to the workpiece clamping plate.

[0009] In one possible implementation of the first aspect, the workpiece clamping plate is located directly above the workpiece support plate.

[0010] In one possible implementation of the first aspect, a timing belt is fitted onto the outer surfaces of the first and second timing pulleys.

[0011] In one possible implementation of the first aspect, a pneumatic guide rail is fixedly installed on the workbench body, and a guide seat is provided on the second support plate, the guide seat being slidably engaged inside the pneumatic guide rail.

[0012] In one possible implementation of the first aspect, the drive end of the pneumatic guide rail is fixedly connected to the guide seat.

[0013] Compared with the prior art, the present invention provides a CNC welding worktable for automotive sheet metal parts, which has the following advantages: I. This invention uses a pneumatic guide rail to drive the guide seat and drive the second support plate to slide, which can flexibly adjust the distance between the two rotating tooling discs to adapt to automotive sheet metal parts of different lengths and sizes. At the same time, the telescopic rod drives the workpiece clamping plate to cooperate with the workpiece support plate to achieve precise clamping of sheet metal parts. The operation is convenient and greatly improves the versatility and ease of use of the device. Second, this invention provides power through a servo motor, which smoothly transmits power via a drive shaft, a first synchronous pulley, a synchronous belt, a second synchronous pulley, and a driven shaft, driving the rotating tooling disc and sheet metal parts to rotate synchronously, achieving all-around automatic welding without the need for manual workpiece flipping. This avoids deviations caused by manual operation, ensures welding accuracy, and improves welding efficiency. At the same time, the coordinated arrangement of the worktable body, the first support plate, and the second support plate ensures the stability of the device's operation and extends its service life.

[0014] Secondly, the present invention provides a welding method for a CNC welding worktable for automotive sheet metal parts, comprising: Obtain the dimensional specifications and tooling spacing data of the automotive sheet metal part to be welded, and calculate the spacing adjustment amount between the two rotating tooling discs based on the dimensional specifications data, so as to determine the adjustment displacement of the pneumatic guide rail on the second support plate; The microscopic flatness of the interface between the end of the automotive sheet metal part and the contact surface of the workpiece support plate is detected. The friction test is performed on the automotive sheet metal part and the workpiece support plate to obtain the interface slip friction factor. The clamping pressure value of the automotive sheet metal part on the workpiece support plate is calculated by combining the interface slip friction factor and the interface microscopic flatness. Based on the clamping pressure value, the downward displacement of the workpiece clamping plate during the clamping action is determined. The welding flip angle and welding time in the preset welding task are obtained. Based on the welding flip angle and welding time, the rotational angular velocity of the servo motor during the synchronous belt drive process is determined. Based on the adjustment displacement, the second support plate is adjusted to a suitable position. Then, based on the downward displacement and the rotational angular velocity, the workpiece clamping plate and the workpiece support plate are used to clamp and fix the automotive sheet metal part. After welding is completed, the welding completed sheet metal part is released and unloaded based on the telescopic rod to obtain the welding result.

[0015] In one possible implementation of the second aspect, calculating the spacing adjustment between the two rotating tooling discs based on the dimensional specification data includes: Based on the aforementioned dimensional specifications, the span data of the two end supports of the automotive sheet metal part is determined. Obtain the current tooling spacing between the rotating tooling disk on the first support plate and the rotating tooling disk on the second support plate; Based on the span data of the two supports and the current tooling spacing, the initial spacing adjustment between the two rotating tooling disks is calculated; Obtain the overlap allowance between the end of the automotive sheet metal part and the workpiece support plate. Based on the overlap allowance, correct the initial spacing adjustment amount to obtain the spacing adjustment amount.

[0016] In one possible implementation of the second aspect, the friction test treatment of the automotive sheet metal part and the workpiece support plate to obtain the interface slip friction factor includes: Prepare test specimens and test substrates made of the same material as the automotive sheet metal part and the workpiece support plate; The test specimen is placed on the upper surface of the test substrate, and a set normal clamping force is applied to the test specimen. The test specimen is horizontally pulled using a dedicated tensile force measuring device, and the initial sliding resistance when the test specimen begins to slip and the continuous sliding resistance when the test specimen is in stable slip are recorded. Combining the initial sliding resistance, the continuous sliding resistance, and the normal clamping force, the interface sliding friction factor is calculated using the following formula: in, Indicates the interfacial slip friction factor. Indicates the initial slip resistance. Indicates continuous slip resistance. Indicates the normal compressive force.

[0017] In one possible implementation of the second aspect, calculating the clamping pressure value of the automotive sheet metal part on the workpiece support plate by combining the interface slip friction factor and the interface micro-flatness includes: Obtain the maximum cutting force experienced by the automotive sheet metal part during processing; Measure the microscopic flatness and effective contact area of ​​the side surface of the contact surface between the automotive sheet metal part and the clamping block; Combining the maximum cutting force, the effective contact area, and the micro-flatness of the side surface, the side sliding resistance of the automotive sheet metal part is calculated using the following formula: in, Indicates lateral slip resistance. Indicates the lateral slip coefficient. Indicates the maximum cutting force. Indicates the microscopic smoothness of the side surface. Indicates reference flatness; Weigh the workpiece corresponding to the automotive sheet metal part, and determine the self-weight load of the automotive sheet metal part based on the workpiece weight. Combining the interface slip friction factor, the maximum cutting force, the self-weight load, and the lateral slip resistance, the clamping pressure value of the automotive sheet metal part on the workpiece support plate is calculated using the following formula: in, This represents the clamping pressure value, and η represents the interfacial slip friction factor. Indicates the maximum cutting force. Indicates self-weight load. This indicates lateral slip resistance.

[0018] As can be seen, by calculating the spacing adjustment between the two rotating tooling discs based on the aforementioned size specifications, this invention can obtain the required distance the second support plate needs to move, providing a basis for the subsequent positioning of the second support plate by the pneumatic guide rail. By conducting friction tests on the automotive sheet metal part and the workpiece support plate, this invention obtains the interface slip friction factor, which allows for understanding the slip characteristics between the automotive sheet metal part and the workpiece support plate, thus providing a quantitative basis for the subsequent calculation of the clamping pressure value. By combining the clamping pressure value, this invention determines the downward displacement of the workpiece clamping plate during the clamping action, thereby obtaining the precise distance the workpiece clamping plate needs to move downward each time it is clamped, ensuring that the clamping force is completely matched with the preset clamping pressure value. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a three-dimensional structural diagram of a CNC welding workbench for automotive sheet metal parts according to an embodiment of the present invention; Figure 2 This is a cross-sectional schematic diagram of the workbench body structure according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a rotating tooling disk structure according to an embodiment of the present invention; Figure 4 This is a flowchart of a welding method for a CNC welding workbench for automotive sheet metal parts, according to an embodiment of the present invention. In the diagram: 1. Workbench body; 11. Servo motor; 12. Drive shaft; 13. First synchronous pulley; 14. First support plate; 15. Second support plate; 16. Rotary tooling disc; 17. Driven shaft; 18. Second synchronous pulley; 19. Synchronous belt; 20. Pneumatic guide rail; 21. Guide seat; 22. Workpiece support plate; 23. Workpiece clamping plate; 24. Telescopic rod. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see Figure 1-3 It includes the workbench body 1, which serves as the mounting base for the entire device and supports the stable operation of all components.

[0023] A servo motor 11 is fixedly mounted on the worktable body 1, providing the power source for the device's operation. A drive shaft 12 is rotatably inserted into the worktable body 1. The output end of the servo motor 11 is fixedly connected to the drive shaft 12, enabling the drive shaft 12 to rotate synchronously. A first synchronous wheel 13 is fixedly sleeved on the end of the drive shaft 12 away from the servo motor 11 for transmitting power. A first support plate 14 is fixedly mounted on the worktable body 1, and a second support plate 15 is slidably mounted on the worktable body 1. The two cooperate to support the rotating tooling disc 16. Both the first support plate 14 and the second support plate 15 are rotatably equipped with rotating tooling discs 16 for placing and rotating automotive sheet metal parts to facilitate omnidirectional welding. A driven shaft 17 is fixedly installed on the rotating tooling disc 16 of the first support plate 14. A second synchronous wheel 18 is fixedly sleeved on the driven shaft 17 to transmit power in conjunction with the first synchronous wheel 13. A workpiece support plate 22 is fixedly installed on the rotating tooling disc 16 to support the automotive sheet metal parts. A workpiece clamping plate 23 is slidably provided on the rotating tooling disc 16 to clamp and fix the sheet metal parts to prevent displacement during welding.

[0024] The rotating tooling plate 16 is provided with a telescopic rod 24. The output end of the telescopic rod 24 is fixedly connected to the workpiece clamping plate 23, which can drive the workpiece clamping plate 23 to slide up and down to adjust the clamping tightness. The workpiece clamping plate 23 is located directly above the workpiece support plate 22 to ensure accurate clamping and positioning of the sheet metal parts and guarantee welding accuracy.

[0025] The outer surfaces of the first synchronous pulley 13 and the second synchronous pulley 18 are fitted with a synchronous belt 19, so that the first synchronous pulley 13 drives the second synchronous pulley 18 to rotate synchronously, thereby achieving smooth power transmission.

[0026] A pneumatic guide rail 20 is fixedly installed on the workbench body 1. A guide seat 21 is provided on the second support plate 15. The guide seat 21 is slidably locked inside the pneumatic guide rail 20, which facilitates the adjustment of the position of the second support plate 15 and adapts to sheet metal parts of different sizes. The driving end of the pneumatic guide rail 20 is fixedly connected to the guide seat 21, which can drive the guide seat 21 to slide along the pneumatic guide rail 20, thereby realizing the smooth movement of the second support plate 15.

[0027] The working principle and usage process of the CNC welding workbench for automotive sheet metal parts of the present invention are as follows: In subsequent use, according to the length of the automotive sheet metal part to be welded, the pneumatic guide rail 20 is activated, and the pneumatic guide rail 20 drives the guide seat 21 to drive the second support plate 15 to slide smoothly. The distance between the two rotating tooling discs 16 is adjusted to adapt to the sheet metal part, thereby improving the versatility of the device. The two ends of the sheet metal part are placed on the workpiece support plate 22, and then the telescopic rod 24 drives the workpiece clamping plate 23 to press down, which cooperates with the workpiece support plate 22 to stably clamp the sheet metal part and prevent displacement during welding.

[0028] After the servo motor 11 is started, the drive shaft 12 drives the first synchronous wheel 13 to rotate, and the second synchronous wheel 18 and the driven shaft 17 are driven by the synchronous belt 19, so that the rotating tooling disk 16 on the first support plate 14 drives the sheet metal part to rotate as a whole, realizing all-round automatic flip welding without manual intervention, effectively improving welding accuracy and production efficiency.

[0029] See Figure 4 The image shows a welding method for a CNC welding workbench for automotive sheet metal parts according to an embodiment of the present invention, comprising: S1. Obtain the dimensional specifications and tooling spacing data of the automotive sheet metal parts to be welded. Based on the dimensional specifications data, calculate the spacing adjustment amount between the two rotating tooling discs to determine the adjustment displacement of the pneumatic guide rail on the second support plate.

[0030] This invention calculates the spacing adjustment between the two rotating tooling discs based on the aforementioned dimensional specifications, thereby obtaining the required distance the second support plate needs to move. This provides a basis for the subsequent positioning of the second support plate by the pneumatic guide rail.

[0031] The dimensional specifications data refer to the length, width, thickness, and other external dimensions of the automotive sheet metal part. The tooling spacing data refers to the current distance between the two rotating tooling discs on the first and second support plates. The spacing adjustment amount is the distance the second support plate needs to move to adapt the two rotating tooling discs to the ends of the sheet metal part. Furthermore, the dimensional specifications data can be obtained by measuring with calipers, consulting the sheet metal part's factory parameters, or scanning the sheet metal part's identification code. The tooling spacing data can be obtained by measuring the distance between the opposite end faces of the two rotating tooling discs using a laser rangefinder or a grating ruler.

[0032] As an embodiment of the present invention, the step of calculating the spacing adjustment amount between the two rotating tooling disks based on the dimensional specification data includes: Based on the aforementioned dimensional specifications, the span data of the two end supports of the automotive sheet metal part is determined. Obtain the current tooling spacing between the rotating tooling disk on the first support plate and the rotating tooling disk on the second support plate; Based on the span data of the two supports and the current tooling spacing, the initial spacing adjustment between the two rotating tooling disks is calculated; Obtain the overlap allowance between the end of the automotive sheet metal part and the workpiece support plate. Based on the overlap allowance, correct the initial spacing adjustment amount to obtain the spacing adjustment amount.

[0033] Wherein, the span data of the two end supports is the effective length of the automotive sheet metal part that needs to be supported by two rotating tooling discs along its length direction; the current tooling spacing is the actual distance between the rotating tooling discs on the first support plate and the rotating tooling discs on the second support plate; the initial spacing adjustment amount is the difference between the current tooling spacing and the span data of the two end supports; and the overlap allowance is the overlap length between the end of the sheet metal part and the workpiece support plate in the support direction when the end of the sheet metal part is placed on the workpiece support plate.

[0034] Optionally, based on the dimensional specifications, the span data of the two ends of the automotive sheet metal part can be obtained by reading the length dimension of the sheet metal part; the current tooling distance between the opposite end faces of the two rotating tooling disks can be measured using a laser rangefinder; combining the span data of the two ends of the support and the current tooling distance, the initial distance adjustment amount is obtained by subtraction calculation, where the initial distance adjustment amount = current tooling distance - span data of the two ends of the support; the overlap allowance between the end of the sheet metal part and the workpiece support plate can be obtained by a displacement sensor, and the initial distance adjustment amount is corrected by addition based on the overlap allowance to obtain the corrected distance adjustment amount, and finally, this distance adjustment amount is used as the adjustment displacement of the second support plate.

[0035] S2. Detect the microscopic flatness of the interface between the end of the automotive sheet metal part and the contact surface of the workpiece support plate, perform a friction test on the automotive sheet metal part and the workpiece support plate to obtain the interface slip friction factor, and calculate the clamping pressure value of the automotive sheet metal part on the workpiece support plate by combining the interface slip friction factor and the interface microscopic flatness.

[0036] This invention obtains the interface slip friction factor by conducting friction tests on the automotive sheet metal part and the workpiece support plate, which can help to understand the slip characteristics between the automotive sheet metal part and the workpiece support plate, and thus provide a quantitative basis for the subsequent calculation of clamping pressure value.

[0037] The interface micro-flatness refers to the degree of micro-geometric undulation between the end of the automotive sheet metal part and the support surface of the workpiece support plate in the contact area, reflecting the flatness of the contact surface. The interface sliding friction factor is the ratio of the sliding resistance generated between the contact surfaces of the automotive sheet metal part and the workpiece support plate when relative sliding occurs to the normal clamping force. Furthermore, the interface micro-flatness can be detected by scanning multiple detection points on the end of the sheet metal part and the support surface of the support plate using an optical profilometer.

[0038] As an embodiment of the present invention, the friction test treatment of the automotive sheet metal part and the workpiece support plate to obtain the interface slip friction factor includes: Prepare test specimens and test substrates made of the same material as the automotive sheet metal part and the workpiece support plate; The test specimen is placed on the upper surface of the test substrate, and a set normal clamping force is applied to the test specimen. The test specimen is horizontally pulled using a dedicated tensile force measuring device, and the initial sliding resistance when the test specimen begins to slip and the continuous sliding resistance when the test specimen is in stable slip are recorded. Combining the initial sliding resistance, the continuous sliding resistance, and the normal clamping force, the interface sliding friction factor is calculated using the following formula: in, Indicates the interfacial slip friction factor. Indicates the initial slip resistance. Indicates continuous slip resistance. Indicates the normal compressive force.

[0039] The test specimen is a sheet-like sample prepared using the same material, stamping process, and surface treatment as automotive sheet metal parts; the test substrate is a plate-like sample prepared using the same material, processing process, and surface flatness as the support surface of the workpiece support plate; the set normal clamping force is a vertical load set by applying a heavy object according to the actual clamping requirements of the automotive sheet metal parts; the tensile force measuring device is a digital display tensile gauge with real-time data acquisition function; the initial sliding resistance is the minimum horizontal tensile force required between the test specimen and the test substrate from a static state to the instant when relative sliding just occurs; the continuous sliding resistance is the stable horizontal tensile force required between the test specimen and the test substrate to maintain uniform relative sliding.

[0040] Furthermore, the prepared test specimen and test substrate are placed under standard environmental conditions for a set period of time to allow their surface states to stabilize. The test substrate is fixed on a horizontal test platform, and the test specimen is placed in the center area of ​​the upper surface of the test substrate. A normal clamping force similar to that under actual clamping conditions is applied to the top of the test specimen using a loading device. The tensile force measuring device is activated to pull the test specimen horizontally at a constant speed, with the pulling direction consistent with the long side direction of the test specimen. During the pulling process, the change curve of the tensile force value with displacement is continuously recorded. The peak tensile force value corresponding to the slip start point is read from the change curve as the initial slip resistance, and the average tensile force value corresponding to the stable section of the curve during the slip process is read as the continuous slip resistance.

[0041] In detail, the above formula uses the arithmetic mean of the initial sliding resistance and the continuous sliding resistance as the comprehensive sliding friction factor, which reflects the average sliding characteristics of the sheet metal part from rest to sliding. In actual production, it is necessary to prevent the sheet metal part from sliding when initially subjected to force during clamping, and to prevent the sheet metal part from sliding when continuously subjected to force during processing. Taking the average of the two can more comprehensively characterize the comprehensive sliding resistance during the clamping process.

[0042] This invention calculates the clamping pressure value of the automotive sheet metal part on the workpiece support plate by combining the interface sliding friction factor and the interface micro-flatness, thereby obtaining a reasonable range of minimum and maximum allowable clamping forces required for the automotive sheet metal part during processing. This provides a basis for subsequent adjustment of the working air pressure of the clamping cylinder and setting of the clamping stroke of the clamping block. The clamping pressure value is a quantitative value reflecting the required degree of clamping between the automotive sheet metal part and the workpiece support plate.

[0043] As an embodiment of the present invention, the step of calculating the clamping pressure value of the automotive sheet metal part on the workpiece support plate by combining the interface slip friction factor and the interface micro-flatness includes: Obtain the maximum cutting force experienced by the automotive sheet metal part during processing; Measure the microscopic flatness and effective contact area of ​​the side surface of the contact surface between the automotive sheet metal part and the clamping block; Combining the maximum cutting force, the effective contact area, and the micro-flatness of the side surface, the side sliding resistance of the automotive sheet metal part is calculated using the following formula: in, Indicates lateral slip resistance. Indicates the lateral slip coefficient. Indicates the maximum cutting force. Indicates the microscopic smoothness of the side surface. Indicates reference flatness; Weigh the workpiece corresponding to the automotive sheet metal part, and determine the self-weight load of the automotive sheet metal part based on the workpiece weight. Combining the interface slip friction factor, the maximum cutting force, the self-weight load, and the lateral slip resistance, the clamping pressure value of the automotive sheet metal part on the workpiece support plate is calculated using the following formula: in, This represents the clamping pressure value, and η represents the interfacial slip friction factor. Indicates the maximum cutting force. Indicates self-weight load. This indicates lateral slip resistance.

[0044] Wherein, the maximum cutting force is the maximum horizontal force exerted on the automotive sheet metal part by the cutting tool during the cutting process; the side micro-flatness is the degree of micro-geometric undulation of the contact surface between the side of the automotive sheet metal part and the clamping block, which is obtained by detection using an optical profilometer; the side slip coefficient is an empirical value predetermined based on the material properties of the side contact surface, used to characterize the influence of the material combination on the slip resistance; the reference flatness is a preset benchmark surface flatness value, which is usually set to 0.8μm according to industry standards or common machining accuracy; the self-weight load is the gravity generated by the mass of the automotive sheet metal part obtained by a weighing device; and the effective contact area is the actual contact area between the side of the automotive sheet metal part and the clamping block.

[0045] Furthermore, a three-dimensional force sensor is installed in the automotive sheet metal processing area. When the tool cuts the sheet metal, the maximum horizontal value displayed by the force sensor is read as the maximum cutting force. The processing is repeated no less than five times, and the arithmetic mean of the measurement results is taken as the final maximum cutting force.

[0046] Furthermore, multiple detection points are selected in the contact area between the side of the automotive sheet metal part and the clamping block. An optical profilometer is used to scan each detection point to obtain the arithmetic mean deviation value of the profile of each point. The arithmetic mean deviation value of the profile of each detection point is then processed by arithmetic averaging to obtain the micro-flatness of the side.

[0047] Furthermore, based on the combination type of the side material of the automotive sheet metal part and the clamping block material, a pre-established material slip characteristic data table is consulted to obtain the empirical value corresponding to the material combination as the side slip coefficient; or by preparing a sample with the same material combination, multiple slip tests are conducted using a friction testing machine, and the side slip coefficient is determined after statistical analysis of the test results.

[0048] Furthermore, an electronic balance is used to weigh individual automotive sheet metal parts to obtain the weight of a single workpiece; the weight of a single workpiece is multiplied by the acceleration due to gravity to obtain its self-weight load.

[0049] It should be understood that the formula for calculating the side slip resistance uses the side slip coefficient α, which is obtained by conducting slip tests on the same batch of automotive sheet metal parts and clamping blocks. The specific operation is as follows: a sample made of the same material as the automotive sheet metal part and a grinding part made of the same material as the clamping block are cut. A horizontal force of the same value as the measured maximum cutting force is applied on a universal friction testing machine. The side slip resistance is measured and then the value of α is calculated. The maximum cutting force is indirectly calculated by installing a torque sensor on the spindle of the machining tool. The measurement points are selected from the three locations with the largest cutting force during the machining process, and the average value is taken. The side micro-flatness is obtained by taking the arithmetic mean of multiple measurements in the contact area between the side of the automotive sheet metal part and the clamping block using a portable optical profilometer. The reference flatness value is 0.8 micrometers, which is used as the benchmark value for dimensionless processing.

[0050] Optionally, in the formula for calculating the side slip resistance, the dimension of the maximum cutting force is Newton, the dimension of the side micro-flatness is micrometer, and the dimension of the reference flatness is also micrometer. Therefore, the flatness ratio is dimensionless, and the side slip coefficient α is a dimensionless coefficient. Thus, the dimension of the calculation result remains Newton, which is consistent with the physical dimension of the side slip resistance, ensuring the rationality of the calculation formula in terms of dimension.

[0051] Furthermore, the above formula for calculating the lateral sliding resistance is based on classical friction theory. It expresses the lateral sliding resistance between the automotive sheet metal part and the clamping block as the product of the sliding coefficient and the cutting force. At the same time, a surface flatness correction term is introduced to reflect the influence of the micro-morphology of the contact surface on the sliding resistance.

[0052] When the micro-smoothness of the side increases, the actual contact area of ​​the contact surface decreases or the micro-interlocking effect weakens, and the sliding resistance decreases accordingly; when the surface smoothness decreases, the contact surface tends to be tighter, and the sliding resistance increases accordingly. This correction relationship conforms to the basic law of the influence of surface smoothness on sliding friction in tribology.

[0053] Optionally, in the formula for calculating the clamping pressure value, the interface slip friction factor is obtained by conducting a slip test on the contact surface between the workpiece support plate and the automotive sheet metal part. The specific operation is as follows: a sample of the same material as the automotive sheet metal part is cut and placed on a grinding surface of the same material as the support plate. A normal force similar to the calculated clamping pressure value is applied, and the slip friction factor is calculated after measuring the horizontal slip resistance. The maximum cutting force is calculated by cutting force simulation software and corrected by combining actual machining measurements. The side slip resistance is calculated using the formula in the previous embodiment. The self-weight load is obtained by direct weighing using a high-precision electronic scale.

[0054] Optionally, in the above formula for clamping pressure, the interfacial sliding friction factor is a dimensionless coefficient, the dimension of the maximum cutting force is Newton, the dimension of the self-weight load is Newton, and the dimension of the lateral sliding resistance is Newton. Therefore, the calculation result of the numerator is in Newton. After dividing by the dimensionless interfacial sliding friction factor, the dimension of the clamping pressure value is still Newton, which is consistent with the physical dimension.

[0055] Furthermore, the above formula is based on the principle of force balance during clamping. It decomposes the total sliding force that automotive sheet metal parts need to overcome during processing into three parts: cutting force, self-weight load, and lateral sliding resistance. The cutting force is the main external force applied to the sheet metal parts by the cutting tool during processing. The self-weight load is the sliding force generated by the weight of the sheet metal parts themselves. The lateral sliding resistance is the frictional resistance between the clamping block and the side of the sheet metal parts. The sum of the three is the minimum total frictional force required to prevent the sheet metal parts from slipping. Dividing the total frictional force by the interface sliding friction factor yields the required clamping pressure value. The larger this value, the greater the clamping force required for the sheet metal parts, providing a quantitative basis for the selection and debugging of subsequent clamping equipment.

[0056] S3. Based on the clamping pressure value, determine the downward displacement of the workpiece clamping plate during the clamping action, obtain the welding flip angle and welding time in the preset welding task, determine the rotational angular velocity of the servo motor during the synchronous belt drive based on the welding flip angle and welding time, adjust the second support plate to a suitable position based on the adjustment displacement, and then use the workpiece clamping plate and the workpiece support plate to clamp and fix the automotive sheet metal part based on the downward displacement and the rotational angular velocity. After welding is completed, the welded sheet metal part is released and unloaded based on the telescopic rod to obtain the welding result.

[0057] This invention determines the downward displacement of the workpiece clamping plate during the clamping action by combining the clamping pressure value, thereby obtaining the precise downward movement distance required by the workpiece clamping plate each time it is clamped, to ensure that the clamping force is perfectly matched with the preset clamping pressure value. The downward displacement is the vertical distance between the workpiece clamping plate from its initial standby position to its final stopping position after the clamping action is completed. Furthermore, firstly, the required clamping degree of the automotive sheet metal part during clamping is evaluated based on the clamping pressure value. Then, the compression amount required to achieve this clamping degree is calculated based on the elastic deformation characteristics of the workpiece clamping plate. According to the installation height of the workpiece clamping plate and the actual thickness of the automotive sheet metal part, the compression amount is converted into the required downward movement distance of the workpiece clamping plate. Finally, the calculated movement distance is fine-tuned based on the surface flatness of the workpiece support plate and the warping deformation of the automotive sheet metal part, thus obtaining an accurate downward displacement.

[0058] This invention determines the rotational angular velocity of the servo motor during synchronous belt drive by obtaining the welding flip angle and welding time in a preset welding task. This ensures that the flip speed of the automotive sheet metal parts is completely synchronized with the welding rhythm during the welding process, avoiding the impact on welding quality due to excessively fast or slow flipping. The rotational angular velocity is the average rotational speed when the servo motor drives the synchronous belt to rotate the rotating fixture. Furthermore, based on the welding flip angle in the preset welding task, combined with the transmission ratio of the rotating fixture and the transmission efficiency of the synchronous belt, the total angle required for the servo motor to rotate is calculated. According to the time allocated to the flipping action in the welding time, the total angle is converted into the rotational angular velocity required by the servo motor. At the same time, considering the weight distribution of the automotive sheet metal parts and the inertial effect during the flipping process, the rotational angular velocity is smoothed to ensure a smooth and impact-free flipping process.

[0059] This invention, based on the adjusted displacement, adjusts the second support plate to a suitable position, and then, combined with the downward displacement and the rotational angular velocity, uses the workpiece clamping plate and the workpiece support plate to clamp and fix the automotive sheet metal part. This ensures that the automotive sheet metal part remains stable throughout the welding process, without displacement or deformation. Furthermore, firstly, the second support plate is driven to move to a designated position according to the adjusted displacement, forming a stable support plane with the workpiece support plate. Then, the workpiece clamping plate is driven to move downward according to the downward displacement, cooperating with the workpiece support plate to firmly clamp the automotive sheet metal part. Subsequently, the servo motor drives the synchronous belt to rotate the rotating fixture disk according to the rotational angular velocity, causing the automotive sheet metal part to reach the preset welding flip angle. All welding processes are completed within the welding time. After welding, the servo motor drives the rotating fixture disk to reset, and the telescopic rod moves the workpiece clamping plate upward to the initial position, completing the release and unloading of the welded sheet metal part, thus obtaining a welding result with accurate positioning and strong welding.

[0060] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A CNC welding worktable for automotive sheet metal parts, comprising a worktable body (1), characterized in that: A servo motor (11) is fixedly installed on the worktable body (1). A drive shaft (12) is rotatably inserted on the worktable body (1). The output end of the servo motor (11) is fixedly connected to the drive shaft (12). A first synchronous wheel (13) is fixedly sleeved on the end of the drive shaft (12) away from the servo motor (11). A first support plate (14) is fixedly installed on the worktable body (1). A second support plate (15) is slidably installed on the worktable body (1). A rotating tooling disk (16) is rotatably installed on both the first support plate (14) and the second support plate (15). A driven shaft (17) is fixedly installed on the rotating tooling disk (16) of the first support plate (14). A second synchronous wheel (18) is fixedly sleeved on the driven shaft (17). A workpiece support plate (22) is fixedly installed on the rotating tooling disk (16). A workpiece clamping plate (23) is slidably installed on the rotating tooling disk (16).

2. The CNC welding workbench for automotive sheet metal parts as described in claim 1, characterized in that, The rotating tooling plate (16) is provided with a telescopic rod (24), and the output end of the telescopic rod (24) is fixedly connected to the workpiece clamping plate (23).

3. The CNC welding workbench for automotive sheet metal parts as described in claim 1, characterized in that, The workpiece clamping plate (23) is located directly above the workpiece support plate (22).

4. The CNC welding workbench for automotive sheet metal parts as described in claim 1, characterized in that, The outer surfaces of the first synchronous pulley (13) and the second synchronous pulley (18) are fitted with synchronous belts (19).

5. The CNC welding workbench for automotive sheet metal parts as described in claim 1, characterized in that, A pneumatic guide rail (20) is fixedly installed on the workbench body (1), and a guide seat (21) is provided on the second support plate (15). The guide seat (21) is slidably locked inside the pneumatic guide rail (20).

6. The CNC welding workbench for automotive sheet metal parts as described in claim 5, characterized in that, The drive end of the pneumatic guide rail (20) is fixedly connected to the guide seat (21).

7. A CNC welding worktable for automotive sheet metal parts according to any one of claims 1 to 6, wherein the welding method is characterized in that, The method includes: Obtain the dimensional specifications and tooling spacing data of the automotive sheet metal part to be welded, and calculate the spacing adjustment amount between the two rotating tooling discs based on the dimensional specifications data, so as to determine the adjustment displacement of the pneumatic guide rail on the second support plate; The microscopic flatness of the interface between the end of the automotive sheet metal part and the contact surface of the workpiece support plate is detected. The friction test is performed on the automotive sheet metal part and the workpiece support plate to obtain the interface slip friction factor. The clamping pressure value of the automotive sheet metal part on the workpiece support plate is calculated by combining the interface slip friction factor and the interface microscopic flatness. Based on the clamping pressure value, the downward displacement of the workpiece clamping plate during the clamping action is determined. The welding flip angle and welding time in the preset welding task are obtained. Based on the welding flip angle and welding time, the rotational angular velocity of the servo motor during the synchronous belt drive process is determined. Based on the adjustment displacement, the second support plate is adjusted to a suitable position. Then, based on the downward displacement and the rotational angular velocity, the workpiece clamping plate and the workpiece support plate are used to clamp and fix the automotive sheet metal part. After welding is completed, the welding completed sheet metal part is released and unloaded based on the telescopic rod to obtain the welding result.

8. The method according to claim 7, characterized in that, The step of calculating the spacing adjustment between the two rotating tooling discs based on the dimensional specifications includes: Based on the aforementioned dimensional specifications, the span data of the two end supports of the automotive sheet metal part is determined. Obtain the current tooling spacing between the rotating tooling disk on the first support plate and the rotating tooling disk on the second support plate; Based on the span data of the two supports and the current tooling spacing, the initial spacing adjustment between the two rotating tooling disks is calculated; Obtain the overlap allowance between the end of the automotive sheet metal part and the workpiece support plate. Based on the overlap allowance, correct the initial spacing adjustment amount to obtain the spacing adjustment amount.

9. The method according to claim 7, characterized in that, The friction test treatment of the automotive sheet metal part and the workpiece support plate to obtain the interface slip friction factor includes: Prepare test specimens and test substrates made of the same material as the automotive sheet metal part and the workpiece support plate; The test specimen is placed on the upper surface of the test substrate, and a set normal clamping force is applied to the test specimen. The test specimen is horizontally pulled using a dedicated tensile force measuring device, and the initial sliding resistance when the test specimen begins to slip and the continuous sliding resistance when the test specimen is in stable slip are recorded. Combining the initial sliding resistance, the continuous sliding resistance, and the normal clamping force, the interface sliding friction factor is calculated using the following formula: in, Indicates the interfacial slip friction factor. Indicates the initial slip resistance. Indicates continuous slip resistance. Indicates the normal compressive force.

10. The method according to claim 7, characterized in that, The method of calculating the clamping pressure value of the automotive sheet metal part on the workpiece support plate by combining the interface slip friction factor and the interface micro-flatness includes: Obtain the maximum cutting force experienced by the automotive sheet metal part during processing; Measure the microscopic flatness and effective contact area of ​​the side surface of the contact surface between the automotive sheet metal part and the clamping block; Combining the maximum cutting force, the effective contact area, and the micro-flatness of the side surface, the side sliding resistance of the automotive sheet metal part is calculated using the following formula: in, Indicates lateral slip resistance. Indicates the lateral slip coefficient. Indicates the maximum cutting force. Indicates the microscopic smoothness of the side surface. Indicates reference flatness; Weigh the workpiece corresponding to the automotive sheet metal part, and determine the self-weight load of the automotive sheet metal part based on the workpiece weight. Combining the interface slip friction factor, the maximum cutting force, the self-weight load, and the lateral slip resistance, the clamping pressure value of the automotive sheet metal part on the workpiece support plate is calculated using the following formula: in, This represents the clamping pressure value, and η represents the interfacial slip friction factor. Indicates the maximum cutting force. Indicates self-weight load. This indicates lateral slip resistance.

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