A welding pre-assembly adjustment method for optimizing door sag

Abstract

The present application belongs to the technical field of welding pre-assembly, and particularly relates to a welding pre-assembly adjusting method for optimizing door sinking; the mass of each door accessory and the centroid coordinates of each door accessory in a theoretical position are collected, and the mass and centroid of all door accessories are loaded at the loading force point; the sinking amount of points A and B is measured, and the door hinge axis is extracted; the door adjusting axis reference is drafted, and the reference point is extracted; the adjusting rotation axis and the door position of the body in white are determined; the front and rear doors are rotated upward with the rotation axis as the reference until the displacement of points A and B reaches the sinking amount; the gap difference value between the outer surface of the measuring position and the internal gap value are measured; and it is determined whether the door adjusting position of the body in white is correct; after the door accessories are assembled, the door can be in a state extremely close to the theoretical position, and the requirements can be met without a large amount of adjustment, thereby improving the work efficiency of the adjusting personnel.

Description

Technical Field

[0001] This invention belongs to the field of welding and pre-assembly technology, specifically relating to a welding and pre-assembly adjustment method for optimizing door sag. Background Technology

[0002] After the body-in-white enters the final assembly workshop, corresponding accessories (such as door panels, rearview mirrors, etc.) are installed on the door sheet metal. After assembly, the door will sink to varying degrees due to gravity, and the amount of sinking will also be different for different types and sizes of doors. This will result in a large difference between the gap between the door and the side panel after final assembly and the standard, requiring a lot of effort to adjust the door to meet the design requirements.

[0003] The existing method is to first reserve an adjustment amount based on experience, and then adjust it according to the actual vehicle condition; or to simulate the adjustment amount by making a counterweight in the factory. The drawback of this approach is that neither experience nor counterweights can be precise, so a large number of adjustments are required depending on the degree of adjustment, which wastes a lot of manpower and resources and is inefficient. Summary of the Invention

[0004] To overcome the above problems, this invention provides a welding pre-assembly adjustment method for optimizing door sag. This method can accurately determine the sag amount after the door is equipped with accessories. Therefore, during the assembly of the body-in-white, the door can be adjusted in the opposite direction to achieve the design position after assembly, reducing the difficulty of later assembly and adjustment and improving work efficiency.

[0005] A pre-assembly and adjustment method for optimizing door sag welding includes the following:

[0006] Step 1, Mass and Center of Gravity Conversion: Sum the masses of each door accessory and the coordinates of the center of gravity of each door accessory in the vehicle coordinate system at its theoretical position. Add the masses of each door accessory to obtain the total mass of all door accessories, and obtain the coordinates (X, Y, Z) of the center of gravity of all door accessories in the vehicle coordinate system using the following formula. This point will be used as the location of the applied force in Step 2:

[0007] X=(X1*M1+X2*M2……Xn*Mn) / (M1+M2+……+Mn)

[0008] Y=(Y1*M1+Y2*M2……Yn*Mn) / (M1+M2+……+Mn)

[0009] Z=(Z1*M1+Z2*M2……Zn*Mn) / (M1+M2+……+Mn)

[0010] Where: Xn is the coordinate of the center of mass of the nth door accessory on the X-axis in the vehicle coordinate system, Yn is the coordinate of the center of mass of the nth door accessory on the Y-axis in the vehicle coordinate system, Zn is the coordinate of the center of mass of the nth door accessory on the Z-axis in the vehicle coordinate system, and Mn is the mass of the nth door accessory.

[0011] Step 2, Simulate Loading: Open the digital model data of the car door sheet metal, draw the mesh, and build the car door sheet metal model. Apply the result of the mass centroid summation and conversion to the car door sheet metal model. First, identify all the fixed points of the car door accessories on the car door sheet metal model, connect each fixed point with RBE2 to obtain the rigid elements of all the fixed points of the car door accessories, and then connect the rigid elements to the points where the loading force is located with RBE3. Finally, convert the mass of all the car door accessories into the corresponding gravity and apply it to the points where the loading force is located.

[0012] Step 3, CAE Calculation: Import the data obtained in Step 2 into NASTRAN software, click Run to obtain the run model, and measure the subsidence of points A and B on the run model; where point A is the rear endpoint of the front door window sill line, and point B is the rear endpoint of the rear door window sill line; the subsidence of point A is the difference between the Z-axis coordinate of point A in the vehicle coordinate system of the model processed by NASTRAN software and the Z-axis coordinate of point A in the vehicle coordinate system of the model in Step 2; the subsidence of point B is the difference between the Z-axis coordinate of point B in the vehicle coordinate system of the model processed by NASTRAN software and the Z-axis coordinate of point B in the vehicle coordinate system of the model in Step 2.

[0013] Step 4, Pick the hinge axis: Open the door sheet metal model with the mass centroid result loaded in Step 2 in CATIA, then extract the door hinge axis, and cut the part between the lower end face of the upper hinge and the upper end face of the lower hinge on the hinge axis.

[0014] Step 5, determine the reference point for the door installation axis: extract the midpoint of the hinge axis extracted in Step 4, and translate it 200mm along the X-axis in the direction of the front of the vehicle in the absolute coordinate system to obtain the reference point.

[0015] Step 6, determine the rotation axis: using the reference point extracted in step 5 as the reference, draw an axis along the Y direction in the absolute coordinate system as the rotation axis;

[0016] Step 7, determine the position of the white body door: using the rotation axis determined in Step 6 as a reference, rotate the front and rear doors upwards respectively, so that points A and B move upwards, until the displacement of points A and B reaches the sinking value of points A and B calculated in Step 3 respectively.

[0017] Step 8, determine the measurement location: cut the cross section at the selected location on the door sheet metal model in Step 7, and select different measurement points at different selected locations to obtain the outer surface gap difference value DTS and the internal gap value corresponding to different measurement points;

[0018] Step 9: When assembling and adjusting the position of the body-in-white door, the welding workshop can determine whether the body-in-white door is correctly positioned based on whether the difference in the outer surface clearance segment (DTS) and the internal clearance value at the corresponding position meet the requirements.

[0019] Step two is implemented in the HYPERMESH software. After completing step two, the model is exported in a format that can be used by the NASTRAN software.

[0020] The selected locations for obtaining the external surface gap difference value (DTS) in step eight are: the upper frame of the front door, the upper frame of the rear door, the lower part of the A-pillar, the B-pillar, and the C-pillar of the door sheet metal; the selected locations for obtaining the internal gap value are: the upper frame of the front door, the upper frame of the rear door, the front and rear door sills, the A-pillar, the B-pillar, and the C-pillar of the door sheet metal.

[0021] When obtaining the outer surface clearance difference (DTS) value, select the measurement point at the selected location as follows:

[0022] Five measurement points are evenly distributed on the upper frame of the front door, including the front and rear endpoints; three measurement points are evenly distributed on the upper frame of the rear door, including the front and rear endpoints.

[0023] Three measurement points are evenly distributed at the top, middle and bottom of the lower part of the A-pillar, including the endpoints;

[0024] Three measuring points are arranged above the windowsill line of column B, and three measuring points are arranged below the windowsill line.

[0025] Three measuring points are arranged above the window sill line of the C-pillar, two measuring points are arranged below the window sill line and above the wheel opening, and two measuring points are arranged at the wheel opening.

[0026] When obtaining internal clearance values, select measurement points at the chosen locations as follows:

[0027] Three measurement points were evenly distributed on the upper frame of the front door;

[0028] Two measurement points are evenly distributed on the upper frame of the rear door;

[0029] A point is placed at the front and rear ends of the front and rear door thresholds respectively as a measurement point;

[0030] Two measuring points are arranged on the lower part of the A-pillar;

[0031] One measurement point is set up above the window sill line of the B-pillar at the front and rear doors, and three measurement points are set up below the window sill line at the front and rear doors.

[0032] One measurement point is placed above the window sill line of the C-pillar, one measurement point is placed below the window sill line and above the wheel opening, and two measurement points are placed at the wheel opening.

[0033] The internal gap value refers to the gap between the inner door panel and the outer side panel at the measurement point.

[0034] The beneficial effects of this invention are:

[0035] This invention can accurately determine the amount of sinking after the door is assembled with accessories. Based on the different cross-sections of the body-in-white, the door is adjusted in the opposite direction during the assembly of the body-in-white. In this way, the door can reach the design position after the assembly is completed. After the qualified body enters the final assembly workshop, the door can be in a state that is very close to the theoretical position after the door accessories are assembled. It can meet the requirements without a lot of adjustments, thus improving the work efficiency of the assembly personnel. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of the present invention and these drawings without creative effort.

[0037] Figure 1 A schematic diagram showing the assembly and adjustment rotation axis for this invention.

[0038] Figure 2 This is a schematic diagram showing the selection of measurement points for this invention.

[0039] The numbers represent the external surface clearance and step difference values ​​at different locations; the letters represent the internal clearance at different locations. Detailed Implementation

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0041] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0042] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0043] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, 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, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0044] Example 1

[0045] A pre-assembly and adjustment method for optimizing door sag welding includes the following:

[0046] Step 1, Mass and Center of Gravity Conversion: Sum the masses of each door accessory and the coordinates of the center of gravity of each door accessory in the vehicle coordinate system at its theoretical position. Add the masses of each door accessory to obtain the total mass of all door accessories, and obtain the coordinates (X, Y, Z) of the center of gravity of all door accessories in the vehicle coordinate system using the following formula. This point will be used as the location of the applied force in Step 2:

[0047] X=(X1*M1+X2*M2……Xn*Mn) / (M1+M2+……+Mn)

[0048] Y=(Y1*M1+Y2*M2……Yn*Mn) / (M1+M2+……+Mn)

[0049] Z=(Z1*M1+Z2*M2……Zn*Mn) / (M1+M2+……+Mn)

[0050] Where: Xn is the coordinate of the center of mass of the nth door accessory on the X-axis in the vehicle coordinate system, Yn is the coordinate of the center of mass of the nth door accessory on the Y-axis in the vehicle coordinate system, Zn is the coordinate of the center of mass of the nth door accessory on the Z-axis in the vehicle coordinate system, and Mn is the mass of the nth door accessory.

[0051] Step 2, Simulate Loading: Open the digital model data of the car door sheet metal, draw the mesh, and build the car door sheet metal model. Apply the result of the mass centroid summation and conversion to the car door sheet metal model. First, identify all the fixed points of the car door accessories on the car door sheet metal model, connect each fixed point with RBE2 to obtain the rigid elements of all the fixed points of the car door accessories, and then connect the rigid elements to the points where the loading force is located with RBE3. Finally, convert the mass of all the car door accessories into the corresponding gravity and apply it to the points where the loading force is located.

[0052] Step 3, CAE Calculation: Import the data obtained in Step 2 into NASTRAN software, click Run to obtain the run model, and measure the sinking of points A and B on the run model; the difference in Z-axis coordinates is taken as the sinking; where point A is the rear endpoint of the front door window sill line, and point B is the rear endpoint of the rear door window sill line; the sinking of point A is the difference between the Z-axis coordinate of point A in the vehicle coordinate system of the model processed by NASTRAN software and the Z-axis coordinate of point A in the vehicle coordinate system of the door sheet metal model in Step 2; the sinking of point B is the difference between the Z-axis coordinate of point B in the vehicle coordinate system of the model processed by NASTRAN software and the Z-axis coordinate of point B in the vehicle coordinate system of the door sheet metal model in Step 2.

[0053] Step 4, Pick the hinge axis: In CATIA, open the door sheet metal model with the mass centroid result loaded in Step 2, and then extract the door hinge axis (the hinge is already in a fixed position; simply find the upper and lower endpoints of the hinge rotation axis, connect them with a straight line, and then extend it appropriately). Then, cut the portion between the lower end face of the upper hinge and the upper end face of the lower hinge along the hinge axis; for example... Figure 1 ;

[0054] Step 5, determine the reference point for the door installation axis: Extract the midpoint of the hinge axis extracted in Step 4, and translate it 200mm along the X-axis in the forward direction of the vehicle in the absolute coordinate system (where the parallel plane of the XY plane is the ground, and the vehicle is placed along the X-axis) to obtain the reference point; for example... Figure 1 ;

[0055] Step Six: Determine the rotation axis: Using the reference point extracted in Step Five as a reference, draw an axis along the Y direction in the absolute coordinate system as the rotation axis; for example... Figure 1 ;

[0056] Step 7, determine the position of the body-in-white doors: using the rotation axis determined in Step 6 as a reference, rotate the front and rear doors upward by X and Y angles respectively, so that points A and B move upward until the displacement of points A and B reaches the sinking values ​​of points A and B calculated in Step 3, which is used to guide the installation and adjustment of the body-in-white doors.

[0057] Step 8, determine the measurement location: such as Figure 2Extract the cross section at the selected position on the digital model of the car door sheet metal in step seven, and select multiple measurement points at different selected positions to obtain the outer surface gap difference value (DTS) and the internal gap value corresponding to the measurement points.

[0058] Step nine: When assembling and adjusting the position of the body-in-white doors, the welding workshop can determine whether the door assembly and adjustment position is correct by checking whether the surface clearance difference (DTS) and internal clearance values ​​at the corresponding positions meet the requirements. There are many ways to handle unqualified door assembly and adjustment positions. If the door is unqualified, replace the door; if the details are unqualified, rework the local surface; and check whether the precision of the parts is unqualified or the welding adjustment is not optimal, leading to the assembly being unqualified.

[0059] Step two is implemented in the HYPERMESH software. After completing step two, the model is exported in a format that can be used by the NASTRAN software.

[0060] The selected locations for obtaining the external surface gap difference value (DTS) in step eight are: the upper frame of the front door, the upper frame of the rear door, the lower part of the A-pillar, the B-pillar, and the C-pillar of the door sheet metal; the selected locations for obtaining the internal gap value are: the upper frame of the front door, the upper frame of the rear door, the front and rear door sills, the A-pillar, the B-pillar, and the C-pillar of the door sheet metal.

[0061] When obtaining the outer surface clearance difference (DTS) value, select the measurement point at the selected location as follows:

[0062] Five measurement points are evenly distributed on the upper frame of the front door, including the front and rear endpoints; three measurement points are evenly distributed on the upper frame of the rear door, including the front and rear endpoints.

[0063] Three measurement points are evenly distributed at the top, middle and bottom of the lower part of the A-pillar, including the endpoints;

[0064] Three measuring points are arranged above the windowsill line of column B, and three measuring points are arranged below the windowsill line.

[0065] Three measuring points are arranged above the window sill line of the C-pillar, two measuring points are arranged below the window sill line and above the wheel opening, and two measuring points are arranged at the wheel opening.

[0066] When obtaining internal clearance values, select measurement points at the chosen locations as follows:

[0067] Three measurement points were evenly distributed on the upper frame of the front door;

[0068] Two measurement points are evenly distributed on the upper frame of the rear door;

[0069] A point is placed at the front and rear ends of the front and rear door thresholds respectively as a measurement point;

[0070] Two measuring points are arranged on the lower part of the A-pillar;

[0071] One measurement point is set up above the window sill line of the B-pillar at the front and rear doors, and three measurement points are set up below the window sill line at the front and rear doors.

[0072] One measurement point is placed above the window sill line of the C-pillar, one measurement point is placed below the window sill line and above the wheel opening, and two measurement points are placed at the wheel opening.

[0073] The internal gap value refers to the gap between the inner door panel and the outer side panel at the measurement point.

[0074] Example 2

[0075] This method includes the following three steps: ① measuring the mass centroid of the accessory, ② summarizing and converting the mass centroid and applying it to the digital model, and ③ calculating the amount of door sag after accessory assembly using CAE.

[0076] 1. Mass centroid conversion: Summarize the mass centroids of each door accessory and convert all mass centroids into the overall mass centroid.

[0077] 2. Simulation loading: The mass centroid is calculated and then applied to the digital model.

[0078] 3. CAE Calculation: After loading the summarized mass centroid based on the CAE model, measure the subsidence of point A (front door) and point B (rear door).

[0079] 4. Pick the hinge axis: Extract the hinge axis from the data, and cut the hinge axis between the lower end face of the upper hinge and the upper end face of the lower hinge (e.g., Figure 1 ).

[0080] 5. Establish the door installation and adjustment axis reference: Extract the midpoint of the hinge axis from step four, and translate it 200mm along the X-axis in the forward direction of the vehicle (e.g., Figure 1 ).

[0081] 6. Determine the axis of rotation for the packing strip: Using the extraction point from step five as a reference, draw the axis of rotation along the Y direction (e.g., ...). Figure 1 ).

[0082] 7. Determine the position of the body-in-white doors: Based on the rotation axis determined in step six, rotate the front and rear doors by X and Y angles respectively (e.g., ...). Figure 1 The values ​​obtained from step three, which cause points A and B to shift upwards, are used to guide the installation and adjustment of the body-in-white doors.

[0083] 8. Determine the measurement location: such as Figure 2 Take cross-sections at all positions shown in the figure and measure the corresponding gap difference values ​​based on the data from step seven. Based on this, the welding workshop can determine the assembly / adjustment position of the body-in-white door by checking whether the gap difference at the corresponding position meets the requirements when assembling and adjusting the body-in-white door position.

[0084] 49 inspection locations are planned for each vehicle model (locations are as follows) Figure 2 For each location, a cross-section is taken from the data obtained after completing the above eight steps. The corresponding dimensions are measured based on the cross-section to provide guidance for the assembly and adjustment of the body-in-white in the welding workshop. Welding workshop staff use feeler gauges and other tools to measure and record the values ​​at the corresponding locations to determine the positional accuracy of the body-in-white doors.

[0085] The cross-section location selection scheme:

[0086] 1. The cross-sectional section is divided into two parts:

[0087] (1) The outer surface gap value and step value are represented by numbers in the indicator diagram;

[0088] (2) Internal clearance: Measure the distance from the inner door panel to the outer side panel; indicated by letters in the instruction diagram;

[0089] 2. Selection of Section for Measuring the Gap Difference of Outer Surfaces:

[0090] (1) Five positions are evenly distributed on the upper frame of the front door, including the front and rear ends; three positions are evenly distributed on the upper frame of the rear door, including the front and rear ends.

[0091] (2) Lower part of A-pillar: 3 evenly distributed at the top, middle and bottom, including the endpoint.

[0092] (3) B-pillars: 3 above the window sill line and 3 below the window sill line;

[0093] (4) C-pillar: 3 above the window sill; 2 below the window sill and above the wheel arch; 2 at the wheel arch;

[0094] 3. Strategies for selecting the location of internal gaps:

[0095] (1) Three positions are evenly distributed on the upper frame of the front door; two positions are evenly distributed on the upper frame of the rear door.

[0096] (2) The front and rear door thresholds are selected only from the front and rear endpoints of straight line segments;

[0097] (3) Lower part of A-pillar: 2.

[0098] (4) B-pillar: There is one front and one back door above the window sill line, and three front and three back doors below the window sill line.

[0099] (5) C-pillar: 1 above the window sill; 1 below the window sill and above the wheel arch; 2 at the wheel arch;

[0100] The information expressed by each outer surface gap is: the gap difference value of each section in the body-in-white state (after turning upward), the body-in-white counterweight state (the state of being pressed down by the attachment), and the actual vehicle state (the state of the actual vehicle door after closing) (with or without attachments can be set as needed).

[0101] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the scope of protection of the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, any person skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present invention within the scope of the technology disclosed in the present invention. These simple modifications are all within the scope of protection of the present invention.

[0102] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0103] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A pre-assembly and adjustment method for optimizing door sag during welding, characterized in that, Includes the following: Step 1, Mass and Center of Gravity Conversion: Sum the masses of each door accessory and the coordinates of the center of gravity of each door accessory in the vehicle coordinate system at its theoretical position. Add the masses of each door accessory to obtain the total mass of all door accessories, and obtain the coordinates (X, Y, Z) of the center of gravity of all door accessories in the vehicle coordinate system using the following formula. This point will be used as the location of the applied force in Step 2: X=(X1*M1+X2*M2……Xn*Mn) / (M1+M2+……+Mn) Y=(Y1*M1+Y2*M2……Yn*Mn) / (M1+M2+……+Mn) Z=(Z1*M1+Z2*M2……Zn*Mn) / (M1+M2+……+Mn) Where: Xn is the coordinate of the center of mass of the nth door accessory on the X-axis in the vehicle coordinate system, Yn is the coordinate of the center of mass of the nth door accessory on the Y-axis in the vehicle coordinate system, Zn is the coordinate of the center of mass of the nth door accessory on the Z-axis in the vehicle coordinate system, and Mn is the mass of the nth door accessory. Step 2, Simulate Loading: Open the digital model data of the car door sheet metal, draw the mesh, and build the car door sheet metal model. Apply the result of the mass centroid summation and conversion to the car door sheet metal model. First, identify all the fixed points of the car door accessories on the car door sheet metal model, connect each fixed point with RBE2 to obtain the rigid elements of all the fixed points of the car door accessories, and then connect the rigid elements to the points where the loading force is located with RBE3. Finally, convert the mass of all the car door accessories into the corresponding gravity and apply it to the points where the loading force is located. Step 3, CAE Calculation: Import the data obtained in Step 2 into NASTRAN software, click Run to obtain the run model, and measure the subsidence of points A and B on the run model; where point A is the rear endpoint of the front door window sill line, and point B is the rear endpoint of the rear door window sill line; the subsidence of point A is the difference between the Z-axis coordinate of point A in the vehicle coordinate system of the model processed by NASTRAN software and the Z-axis coordinate of point A in the vehicle coordinate system of the model in Step 2; the subsidence of point B is the difference between the Z-axis coordinate of point B in the vehicle coordinate system of the model processed by NASTRAN software and the Z-axis coordinate of point B in the vehicle coordinate system of the model in Step 2. Step 4, Pick the hinge axis: Open the door sheet metal model with the mass centroid result loaded in Step 2 in CATIA, then extract the door hinge axis, and cut the part between the lower end face of the upper hinge and the upper end face of the lower hinge on the hinge axis. Step 5, determine the reference point for the door installation axis: extract the midpoint of the hinge axis extracted in Step 4, and translate it 200mm along the X-axis in the forward direction of the vehicle to obtain the reference point. Step 6, determine the rotation axis: using the reference point extracted in step 5 as the reference, draw an axis along the Y direction in the absolute coordinate system as the rotation axis; Step 7, determine the position of the white body door: using the rotation axis determined in Step 6 as a reference, rotate the front and rear doors upwards respectively, so that points A and B move upwards, until the displacement of points A and B reaches the sinking value of points A and B calculated in Step 3 respectively. Step 8, determine the measurement location: cut the cross section at the selected location on the door sheet metal model in Step 7, and select different measurement points at different selected locations to obtain the outer surface gap difference value DTS and the internal gap value corresponding to different measurement points; Step 9: When assembling and adjusting the position of the body-in-white door, the welding workshop can determine whether the body-in-white door is correctly positioned based on whether the difference in the outer surface clearance segment (DTS) and the internal clearance value at the corresponding position meet the requirements.

2. The pre-assembly and adjustment method for optimizing door recess welding according to claim 1, characterized in that, Step two is implemented in the HYPERMESH software. After completing step two, the model is exported in a format that can be used by the NASTRAN software.

3. The pre-assembly and adjustment method for optimizing door recess welding according to claim 1, characterized in that, The selected locations for obtaining the external surface gap difference value (DTS) in step eight are: the upper frame of the front door, the upper frame of the rear door, the lower part of the A-pillar, the B-pillar, and the C-pillar of the door sheet metal; the selected locations for obtaining the internal gap value are: the upper frame of the front door, the upper frame of the rear door, the front and rear door sills, the A-pillar, the B-pillar, and the C-pillar of the door sheet metal.

4. The pre-assembly and adjustment method for optimizing door recess welding according to claim 3, characterized in that, When obtaining the outer surface clearance difference (DTS) value, select the measurement point at the selected location as follows: Five measurement points are evenly distributed on the upper frame of the front door, including the front and rear endpoints; three measurement points are evenly distributed on the upper frame of the rear door, including the front and rear endpoints. Three measurement points are evenly distributed at the top, middle and bottom of the lower part of the A-pillar, including the endpoints; Three measuring points are arranged above the windowsill line of column B, and three measuring points are arranged below the windowsill line. Three measuring points are arranged above the window sill line of the C-pillar, two measuring points are arranged below the window sill line and above the wheel opening, and two measuring points are arranged at the wheel opening.

5. The pre-assembly and adjustment method for optimizing door recess welding according to claim 3, characterized in that, When obtaining internal clearance values, select measurement points at the chosen locations as follows: Three measurement points were evenly distributed on the upper frame of the front door; Two measurement points are evenly distributed on the upper frame of the rear door; A point is placed at the front and rear ends of the front and rear door thresholds respectively as a measurement point; Two measuring points are arranged on the lower part of the A-pillar; One measurement point is set up above the window sill line of the B-pillar at the front and rear doors, and three measurement points are set up below the window sill line at the front and rear doors. One measurement point is placed above the window sill line of the C-pillar, one measurement point is placed below the window sill line and above the wheel opening, and two measurement points are placed at the wheel opening.

6. The pre-assembly and adjustment method for optimizing door recess welding according to claim 1, characterized in that, The internal gap value refers to the gap between the inner door panel and the outer side panel at the measurement point.

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