Automobile rear floor punch forming die and process thereof

Abstract

The invention discloses an automobile rear floor punch forming die and a process thereof, and relates to the technical field of punch forming. The die is composed of flexible stamping assemblies which are symmetrically arranged, a matrix type servo driving ball punch is arranged in each assembly, the end of each punch is covered with three polyurethane composite buffer layers, a force sensitive resistor is integrated, and displacement-pressure closed-loop control is achieved; the upper die moves downwards through a lower punching motor, a crankset wheel, a connecting rod and a balance weight mechanism and is pulled to return through a return stroke reset motor, and a speed-adjustable and pause forming curve is formed. The technology sequentially comprises the six steps of blank positioning, material pre-pressing, low-speed preforming, high-speed final forming, bottom dead point pressure maintaining compensation and mold opening and part taking, and a local heating and pause stress relaxation strategy is provided. The system can complete punch curved surface reconstruction in a short time so as to adapt to different materials or vehicle types, the forming quality, the rebound control precision and the remodeling efficiency are remarkably improved, and the system is suitable for flexible mass production of high-strength steel and aluminum alloy automobile rear floors.

Description

Technical Field

[0001] The present invention relates to the technical field of stamping forming, and specifically relates to an automobile rear floor stamping forming die and its process. Background Art

[0002] Conventionally, the stamping of automobile rear floors generally uses a whole-piece rigid upper and lower die in cooperation with a hydraulic press to complete the forming. In order to achieve the local pressing effect, the existing process can only paste gaskets on the die surface or change the local gap through mechanical wedges; its defects are mainly reflected in: Rigid load distribution: The surface pressure of the die cannot be adjusted in real time, and uneven thinning and cracks are likely to occur when the sheet thickness or strength fluctuates. Passive springback compensation: It relies on repeated grinding during trial molding or leaving a reverse interference amount on the die surface, with a long development cycle and poor springback control accuracy. Poor adaptability to high-strength steel: The sheet with a yield strength ≥ 600 MPa has a low elongation rate, and traditional single high-speed forming is likely to cause cracked edges. Low die change efficiency: When changing to a different vehicle model, the entire die needs to be replaced, and hoisting, leveling, and trial molding take at least several hours, unable to meet the requirements of flexible production. Lack of safety monitoring: Operators can only judge abnormalities based on the stamping sound or the press curve, and it is difficult to detect dangerous conditions such as suspension and off-loading in a timely manner, posing safety hazards. Summary of the Invention

[0003] To overcome the defects of the above-mentioned prior art, the present invention provides the following technical solution: An automobile rear floor stamping forming die, including a bottom plate, on which two parallel and symmetrically arranged upper die movement support guide rods are slidably installed along the gravity direction. An upper die mounting plate is fixedly installed between the tops of the two upper die movement support guide rods. Flexible stamping components are fixedly installed on the opposite surfaces of the upper die mounting plate and the bottom plate, and the two flexible stamping components are symmetrically arranged; the flexible stamping component includes a die housing, on which an edge limiting frame is fixedly installed. Inside the die housing, a plurality of servo motors arranged in a rectangular array are fixedly installed. Each servo motor is controlled by an independent servo driver. A punch adjusting lead screw is fixedly installed on the output shaft of each servo motor. A punch is threadedly sleeved on each punch adjusting lead screw. The end of each punch is spherical. Adjacent punches are slidably matched through spline grooves and splines that mesh with each other. All punches at the edge position of the rectangular array are slidably matched with the inner wall of the die housing by splines to prevent the punches from rotating.

[0004] Preferably, the surfaces of all punch ball heads on each flexible stamping component are covered with a polyurethane casting composite layer, and the polyurethane casting composite layer has three layers in total: The upper micro-hard wear-resistant layer of the polyurethane casting composite layer: thickness 0.8 mm, polyurethane Shore A95, crosslinking density 7.5×10⁻ 4mol cm⁻³, 2 wt% of Si3N4 microbeads (average particle size 0.8 µm) is blended to improve surface wear resistance; Middle functional buffer layer in the polyurethane casting composite layer: thickness 1.4–4.4 mm, the matrix is Shore A85 polyurethane with microcellular foaming (closed cell rate 92%), pore diameter 120–200 µm; Two microstructures are embedded in the matrix: honeycomb unit and negative Poisson's ratio trapezoidal unit; Energy-absorbing cushion layer in the lower layer of the polyurethane casting composite layer: thickness 1.0–2.0 mm, polyurethane Shore A75, adding 5 phr of high resilience SBR rubber powder.

[0005] Preferably, an intermediate reinforcing plate is provided below the bottom plate. The intermediate reinforcing plate and the bottom plate are both fixedly installed on the inner wall of the moisture-proof housing. A limiting plate is fixedly installed on the intermediate reinforcing plate. Both ends of the limiting plate are slidably matched with two upper die movement support guide rods. The two upper die movement support guide rods are also slidably matched with the intermediate reinforcing plate; At the position of each upper die movement support guide rod below the bottom plate, a spline sleeve is slidably and rotatably sleeved. A rotary insertion disk is fixed on the top of the spline sleeve. A rotary insertion groove for rotary cooperation with the rotary insertion disk is provided on the circumferential surface of the upper die movement support guide rod.

[0006] Preferably, a sprocket wheel is sleeved on the bottom end of the spline sleeve in a spline sliding manner. The sprocket wheel is arranged between the limiting plate and the intermediate reinforcing plate, and the sprocket wheel is rotatably matched with the limiting plate and the intermediate reinforcing plate. A lower punch motor is also fixedly installed on the intermediate reinforcing plate. The output shaft of the lower punch motor is connected to the two sprocket wheels through a transmission chain.

[0007] Preferably, the same number of upper connecting rods and lower connecting rods are movably installed in a circular array on the rotary insertion disk and the sprocket wheel respectively. The upper connecting rods and the lower connecting rods are movably connected to each other. A counterweight is movably connected to the movable connection of each upper connecting rod and lower connecting rod.

[0008] Preferably, a return reset motor and a resistance wheel bracket are fixedly installed on the bottom plate. A resistance wheel is rotatably installed at the top of the resistance wheel bracket. A winding disk is fixedly installed on the output shaft of the return reset motor. A lifting rope is wound around the winding disk. The lifting rope passes through the resistance wheel and is fixed to the upper die mounting plate. The lifting rope is lapped on the circumferential surface of the resistance wheel.

[0009] The process of forming the automotive rear floor using the automotive rear floor stamping die includes the following steps: It includes six steps: blank positioning, pre-pressing, low-speed pre-forming, high-speed final forming, bottom dead center pressure holding compensation, and mold opening and part taking.

[0010] Preferably, a pause time of 0.1 s to 0.5 s is provided between pre-forming and final forming for stress relaxation.

[0011] Preferably, when the sheet material is high-strength steel with a yield strength ≥ 600 MPa, local heating of the crack-prone area is carried out at 200 °C to 300 °C during the preforming stage.

[0012] Preferably, the dwell time at bottom dead center is 0.3 s to 1.0 s, and the compensation amount accuracy is ±0.05 mm to offset material springback.

[0013] The present invention has the following beneficial effects compared with the prior art: (1) The present invention uses a flexible stamping assembly composed of ball-headed punches driven by a rectangular array of servo motors. Each punch is independently closed-loop controlled and senses the contact pressure in real time, and can adjust the displacement as needed within milliseconds, actively compensating for the local thickness difference and shape error of the sheet material to achieve progressive loading in zones; compared with traditional integral rigid dies, its local forming uniformity is improved, the maximum thinning rate is reduced, and cracking and orange peel defects are significantly inhibited; (2) The polyurethane casting composite layer 105 of the present invention adopts a three-layer design of "micro-hard wear-resistant layer + honeycomb / negative Poisson's ratio functional layer + energy-absorbing cushion layer". The friction coefficient of the upper TiN nano-coating is only 0.12, and the honeycomb-negative Poisson's ratio staggered structure in the middle layer diverts the peak load into a platform load, significantly reducing surface scratches and springback of the sheet material; (3) Positioning pins and depressions are provided at the four corners of the upper and lower flexible stamping components of the present invention, and the blank can be accurately positioned by a robot at one time; combined with rapid clamping within 0.1 s in the pre-pressing section, the positioning accuracy is improved, avoiding forming errors and additional trimming caused by initial offset, and the overall line rhythm is improved; (4) The present invention drives the upper die through the combination mechanism of the lower punch motor - sprocket wheel - connecting rod - counterweight block, realizing complete electrical separation of the lower punch and the return stroke; the return stroke reset motor provides a reverse constant torque, automatically offsetting gravity and freezing the position when entering the dwell stage at bottom dead center, and then the local punch is finely adjusted by ±0.05 mm for compensation, which can effectively control the springback of high-strength steel parts during forming; (5) The flexible stamping component of the present invention can change the stamping shape of the upper and lower dies. The system has a built-in multi-material process spectrum library. When changing the type, only the preset surface data of aluminum alloy or high-strength steel needs to be called, and the servo array is recalibrated; compared with traditional replacement of the entire die, the line change time is shortened to, and no large-scale hoisting operation is required, significantly improving the flexibility and safety of multi-variety and small-batch production; (6) The lower punch motor, sprocket wheel, connecting rod, and counterweight mechanism of the present invention are frequency-controlled and can continuously vary the speed among the four stages of pre-pressing - preforming - high-speed forming - dwell; the return stroke reset motor provides a programmable reverse constant torque and automatically holds the position at bottom dead center to achieve a micro-displacement of 0.05 mm level required for dwell compensation. Description of the Drawings

[0014] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is a schematic diagram of the structure at the transmission chain of the present invention; Figure 3 It is a schematic diagram of the structure at the sprocket wheel of the present invention; Figure 4 Schematic diagram of the spline sleeve structure of the present invention; Figure 5 For the present invention Figure 4 Schematic diagram of the structure at position A; Figure 6 Schematic diagram of the stamping die structure of the present invention; Figure 7 Schematic diagram of the punch structure of the present invention.

[0015] In the figure: 101 - Die housing; 102 - Servo motor; 103 - Edge limiting frame; 104 - Punch; 105 - Polyurethane casting composite layer; 106 - Punch adjusting screw rod; 107 - Upper die mounting plate; 108 - Upper die movement support guiding rod; 109 - Bottom plate; 110 - Lower middle reinforcing plate; 111 - Lower punch motor; 112 - Moisture-proof housing; 113 - Limiting plate; 114 - Transmission chain; 115 - Sprocket wheel; 116 - Upper connecting rod; 117 - Lower connecting rod; 118 - Counterweight block; 119 - Spline sleeve; 120 - Rotating embedding groove; 121 - Rotating embedding disc; 122 - Resistance wheel bracket; 123 - Return reset motor; 124 - Pulling rope; 125 - Reel; 126 - Resistance wheel. Specific embodiments

[0016] The following combines the attached Figures 1 - 7 and further illustrates the technical solution of the present invention through specific embodiments.

[0017] The present invention provides a stamping die for an automotive rear floor, which includes a bottom plate 109. Two parallel and symmetrically arranged upper die movement support guide rods 108 are slidably installed on the bottom plate 109 along the direction of gravity. An upper die mounting plate 107 is fixedly installed between the tops of the two upper die movement support guide rods 108. Flexible stamping components are fixedly installed on the opposite surfaces of the upper die mounting plate 107 and the bottom plate 109, and the two flexible stamping components are symmetrically arranged; the flexible stamping component includes a die housing 101, an edge limiting frame 103 is fixedly installed on the die housing 101, a plurality of servo motors 102 arranged in a rectangular array are fixedly installed inside the die housing 101, each servo motor 102 is controlled by an independent servo driver, a punch adjusting screw rod 106 is fixedly installed on the output shaft of each servo motor 102, a punch 104 is threadedly sleeved on each punch adjusting screw rod 106, the end of each punch 104 is spherical, the radius of the sphere is between 25 mm and 35 mm, and a force-sensitive resistor is attached to the surface of the end of each punch 104 for monitoring the contact pressure with the workpiece to be stamped (judging whether there is effective contact). Adjacent punches 104 are slidably matched through spline grooves and splines that mesh with each other. All punches 104 at the edge position of the rectangular array are slidably matched with the inner wall of the die housing 101 by splines to prevent the punches 104 from rotating on their own.

[0018] A polyurethane casting composite layer 105 covers the surfaces of all the spherical heads of the punches 104 on each flexible stamping component. The polyurethane casting composite layer 105 has three layers in total: the upper slightly hard and wear-resistant layer of the polyurethane casting composite layer 105: the thickness is 0.8 mm, polyurethane Shore A95, crosslinking density 7.5×10⁻ 4mol cm⁻³, 2 wt% Si3N4 microbeads (average particle size 0.8 µm) are admixed to improve surface wear resistance; this layer is in direct contact with the sheet metal. After 0.6 µm TiN physical vapor deposition, the friction coefficient is reduced to 0.12 and the nanohardness is 23 GPa, capable of withstanding an instantaneous contact pressure of 350 MPa. Polyurethane casting composite layer 105 Middle functional buffer layer: thickness 1.4–4.4 mm, the matrix is Shore A85 polyurethane with microporous foaming (closed cell rate 92%), pore size 120–200 µm; two microstructures are embedded in the matrix: honeycomb cells and auxetic trapezoidal cells; among them, honeycomb cells: regular hexagonal column shells, side length 6 mm, wall thickness 2 mm, longitudinal porosity 58%, honeycomb axial stiffness 38 MPa, evenly diverting local peak loads; auxetic trapezoidal cells: side length 15 mm, rotation angle 35°, inner wall thickness of the cell 1.2 mm; the measured Poisson's ratio is -0.23, which can expand laterally during compression to fit the punch gap and eliminate the step. The two types of cells are arranged alternately in a 2:1 order, ensuring both elastic recovery and providing progressive buffering. The experimental compression curve shows that the compressive stress plateau at 35% strain is only 4.3 MPa. Polyurethane casting composite layer 105 Lower energy-absorbing cushion layer: thickness 1.0–2.0 mm, polyurethane Shore A75, adding 5 phr of high resilience SBR rubber powder; dynamic loss factor tanδ = 0.19, capable of absorbing 18% of the impact energy and damping vibration under 10 Hz impact. This layer uses 35° dovetail grooves to interlock with the conical wedge on the top surface of the punch to prevent slipping.

[0019] A middle reinforcing plate 110 is provided below the bottom plate 109. Both the middle reinforcing plate 110 and the bottom plate 109 are fixedly mounted on the inner wall of a moisture-proof shell 112 (when in use, the moisture-proof shell 112 is buried below the bottom plate of the workshop, for example, buried in the soil, so that the bottom plate 109 is flush with the ground). A limiting plate 113 is fixedly mounted on the middle reinforcing plate 110. Both ends of the limiting plate 113 are slidingly engaged with the two upper mold motion support guide rods 108, and the two upper mold motion support guide rods 108 are also slidingly engaged with the middle reinforcing plate 110; each upper mold motion support guide rod 108 is located below the bottom plate 109 and is slidingly and rotatably sleeved with a spline sleeve 119. A rotating embedded disk 121 is fixed to the top of the spline sleeve 119, and a rotating embedded groove 120 is provided on the circumferential surface of the upper mold motion support guide rod 108 for rotating engagement with the rotating embedded disk 121. The bottom end of the spline sleeve 119 is provided with a chainring 115 in a spline sliding manner. The chainring 115 is provided between the limiting plate 113 and the intermediate reinforcing plate 110, and the chainring 115 rotates in conjunction with the limiting plate 113 and the intermediate reinforcing plate 110. The intermediate reinforcing plate 110 is also fixedly mounted with a lower punch motor 111. The output shaft of the lower punch motor 111 is connected to the two chainrings 115 via a transmission chain 114. The same number of upper connecting rods 116 and lower connecting rods 117 are movably mounted in a circular array on the rotating embedded disk 121 and the chainring 115. The upper connecting rods 116 and the lower connecting rods 117 are movably connected to each other, and a counterweight 118 is movably connected to the movable connection between each upper connecting rod 116 and the lower connecting rod 117. A return reset motor 123 and a resistance wheel bracket 122 are fixedly installed on the base plate 109. A resistance wheel 126 is rotatably installed on the top of the resistance wheel bracket 122. A winding drum 125 is fixedly installed on the output shaft of the return reset motor 123. A lifting rope 124 is wound around the winding drum 125. The lifting rope 124 is fixed to the upper mold mounting plate 107 through the resistance wheel 126, and the lifting rope 124 is overlapped on the circumferential surface of the resistance wheel 126.

[0020] The stamping process for the rear floor of an automobile includes six steps: blank positioning, pre-pressing, low-speed preforming, high-speed final forming, bottom dead center pressure holding and compensation, and mold opening and part removal. A pause of 0.1s to 0.5s is set between preforming and final forming to allow for stress relaxation. When the sheet material is high-strength steel with a yield strength of 600MPa or higher, local heating of 200°C to 300°C is performed on the crack-prone areas during the preforming stage. The bottom dead center pressure holding time is 0.3s to 1.0s, with a compensation accuracy of ±0.05mm to offset material springback.

[0021] In the flexible stamping assembly (lower die) fixedly installed with the bottom plate 109, positioning pins are provided on the four punches 104 at the four corners. (Similarly, depressions are provided on the corresponding four punches 104 on the flexible stamping assembly (upper die) fixedly installed with the upper die mounting plate 107, so that the pins can be inserted into the depressions).

[0022] The forming process flow of the automotive rear floor is as follows (the following specific values are all examples, and the actual values depend on the shape of the automotive rear floor): Blank positioning: The robot grabs the steel plate and uses the positioning holes to cooperate with the positioning pins on the lower die punch 104. Pre-pressing: The upper die descends at a rate of 100 mm / s for 50 mm, and the partitioned blank holding section is clamped with an initial force value of 40 kN (the upper and lower punches 104 at the edge position come into contact first, and the clamping force is judged according to their own force-sensitive resistors). Pre-forming: The upper die changes to 60 mm / s and the stroke is 120 mm; all the punch arrays 104 move synchronously, and micro-stop for 50 ms every 25 mm stroke for stress balance. Final forming: The upper die accelerates to 200 mm / s to complete the remaining stroke of 80 mm. Pressure holding and shaping: Hold for 0.5 s, and the controller fine-tunes the displacement of the local punch 104 by ±0.05 mm according to the real-time data to offset the springback. Die opening and part taking: The upper die returns, the upper die rises to 150 mm, and the unloading push rod ejects (several individual punches 104 in the upper die or lower die extend (depending on the shape of the required formed rear floor): specifically controlling the corresponding servo motor 102 can control the extension of the punch 104, and then the formed part is ejected), and the manipulator removes the part (automotive rear floor); subsequently, the contour of the removed automotive rear floor is trimmed. Quick die change: If switching from steel to aluminum alloy, the system calls the preset surface and process spectrum to complete the re-setting of the upper and lower die punch arrays 104.

[0023] The movement of the upper die is controlled by the lower punch motor 111 and the return reset motor 123. The lower punch motor 111 controls the downward punching of the upper die, and the return reset motor 123 controls the upward return of the upper die. At this time, the lower punch motor 111 stops, and the return reset motor 123 is controlled. The output shaft of the return reset motor 123 drives the wire reel 125 to rotate. The wire reel 125 winds the lifting rope 124 and then pulls the upper die on the upper die mounting plate 107 to return upward. During downward punching, the return reset motor 123 stops, and the lower punch motor 111 starts. The output shaft of the lower punch motor 111 drives two sprocket wheels 115 to rotate through the transmission chain 114. The sprocket wheel 115 drives the spline sleeve 119 to rotate. The spline sleeve 119 drives the upper connecting rod 116 on the rotary insertion disc 121. The sprocket wheel 115 drives the lower connecting rod 117 to rotate together. At the same time, the counterweight 118 at the connection of the upper connecting rod 116 and the lower connecting rod 117 will also rotate. The rotation of the counterweight 118 will move outward under the action of centrifugal force, thereby pulling the upper connecting rod 116 and the lower connecting rod 117, and gradually reducing the angle between the upper connecting rod 116 and the lower connecting rod 117. Since the sprocket wheel 115 is restricted between the limiting plate 113 and the lower intermediate reinforcing plate 110 (it cannot move axially), at this time, the rotary insertion disc 121 will pull the upper die movement support guide rod 108 to move downward (the spline sleeve 119 slides axially with the sprocket wheel 115). The upper die movement support guide rod 108 will drive the flexible stamping component (upper die) on the upper die mounting plate 107 to move downward. By changing the rotation speed of the output shaft of the lower punch motor 111, the descending speed of the upper die can be changed. This is because if the lower punch motor 111 is not started, the upper die will move downward uniformly under the action of gravity, overcoming the resistance of the resistance wheel 126, the wire reel 125, and the rotor of the return reset motor 123. The function of the lower punch motor 111 is to increase the descending speed of the upper die. The holding pressure moment is to energize the return reset motor 123 (to overcome the gravity of the upper die and the force acting on the upper die by the counterweight 118), so that the upper die stops descending.

Claims

1. An automotive rear floor stamping die, characterized in that: It includes a bottom plate (109). On the bottom plate (109), two parallel and symmetrically arranged upper die moving support guiding rods (108) are slidably installed along the direction of gravity. An upper die mounting plate (107) is fixedly installed between the tops of the two upper die moving support guiding rods (108). Flexible stamping components are fixedly installed on the opposite surfaces of the upper die mounting plate (107) and the bottom plate (109), and the two flexible stamping components are symmetrically arranged. The flexible stamping component includes a die housing (101). An edge limiting frame (103) is fixedly installed on the die housing (101). A plurality of servo motors (102) arranged in a rectangular array are fixedly installed inside the die housing (101). Each servo motor (102) is controlled by an independent servo driver. A punch adjusting screw rod (106) is fixedly installed on the output shaft of each servo motor (102). A punch (104) is threadedly sleeved on each punch adjusting screw rod (106). The end of each punch (104) is spherical. Adjacent punches (104) are slidably matched through mutually engaged spline grooves and splines. All punches (104) at the edge position of the rectangular array are slidably matched with the inner wall of the die housing (101) by splines to prevent the punches (104) from rotating.

2. The stamping and forming die for the rear floor of an automobile according to claim 1, wherein: A polyurethane casting composite layer (105) covers the surfaces of the ball heads of all punches (104) on each flexible stamping component. The polyurethane casting composite layer (105) has a total of three layers: Upper micro-hard wear-resistant layer of the polyurethane casting composite layer (105): thickness 0.8 mm, polyurethane Shore A95, crosslinking density 7.5×10⁻ 4 mol cm⁻³, blended with 2 wt% Si3N4 microbeads (average particle size 0.8 µm) to improve surface wear resistance; Middle functional buffer layer of the polyurethane casting composite layer (105): with a thickness of 1.4–4.4 mm, the matrix is ShoreA85 polyurethane with microporous foaming (closed cell rate 92%), pore diameter 120–200 µm; two microstructures are embedded in the matrix: honeycomb cells and negative Poisson's ratio trapezoidal cells. Lower energy absorption cushion layer of the polyurethane casting composite layer (105): with a thickness of 1.0–2.0 mm, polyurethane ShoreA75, adding 5 phr of high resilience SBR rubber powder.

3. The stamping and forming die for the rear floor of an automobile according to claim 2, characterized in that: A lower die intermediate reinforcing plate (110) is arranged below the bottom plate (109). The lower die intermediate reinforcing plate (110) and the bottom plate (109) are both fixedly installed on the inner wall of a moisture-proof housing (112). A limiting plate (113) is fixedly installed on the lower die intermediate reinforcing plate (110). The two ends of the limiting plate (113) are slidably matched with the two upper die moving support guiding rods (108). The two upper die moving support guiding rods (108) are also slidably matched with the lower die intermediate reinforcing plate (110). A spline sleeve (119) is slidably and rotatably sleeved at the position of each upper die moving support guiding rod (108) below the bottom plate (109). A rotary embedding disc (121) is fixed at the top of the spline sleeve (119). A rotary embedding groove (120) for rotary cooperation with the rotary embedding disc (121) is formed on the circumferential surface of the upper die moving support guiding rod (108).

4. A stamping and forming die for the rear floor of an automobile according to claim 3, characterized in that: The bottom end of the spline sleeve (119) is sleeved with a chainring (115) in a spline sliding manner. The chainring (115) is arranged between the limiting plate (113) and the following intermediate reinforcing plate (110), and the chainring (115) is rotationally matched with the limiting plate (113) and the following intermediate reinforcing plate (110). A lower punching motor (111) is fixedly installed on the following intermediate reinforcing plate (110), and the output shaft of the lower punching motor (111) is connected to the two chainrings (115) through a transmission chain (114).

5. The stamping and forming die for the rear floor of an automobile according to claim 4, wherein: The same number of upper connecting rods (116) and lower connecting rods (117) are movably installed in a circular array on the rotary insertion disc (121) and the chainring (115) respectively. The upper connecting rods (116) and the lower connecting rods (117) are movably connected, and a counterweight block (118) is movably connected to the movable connection part of each upper connecting rod (116) and lower connecting rod (117).

6. The automotive rear floor stamping die according to claim 5, characterized in that: A return reset motor (123) and a resistance wheel bracket (122) are fixedly installed on the bottom plate (109). The top end of the resistance wheel bracket (122) is rotatably installed with a resistance wheel (126). A wire reel (125) is fixedly installed on the output shaft of the return reset motor (123). A lifting rope (124) is wound around the wire reel (125). The lifting rope (124) passes through the resistance wheel (126) and is fixed to the upper die mounting plate (107). The lifting rope (124) is lapped on the circumferential surface of the resistance wheel (126).

7. A process for forming an automotive rear floor using the stamping and forming die for automotive rear floor according to any one of claims 1-6, characterized in that, It includes the following steps: It includes six steps: blank positioning, pre-pressing, low-speed pre-forming, high-speed final forming, bottom dead center pressure holding compensation, and mold opening and part taking.

8. The process according to claim 7, wherein: A pause time of 0.1 s to 0.5 s is provided between pre-forming and final forming for stress relaxation.

9. The process according to claim 7, characterized in that: When the sheet material is high-strength steel with a yield strength ≥ 600 MPa, local heating at 200 °C to 300 °C is performed on the crack-prone area in the pre-forming stage.

10. The process according to claim 7, characterized in that: The bottom dead center pressure holding time is 0.3 s to 1.0 s, and the compensation amount accuracy is ±0.05 mm to offset material springback.

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