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CN-121973464-A - Forming method of three-dimensional complex curved surface skin structure

CN121973464ACN 121973464 ACN121973464 ACN 121973464ACN-121973464-A

Abstract

The invention discloses a three-dimensional complex curved surface skin structure forming method, which relates to the technical field of skin forming and comprises the following specific steps of selecting a plastic blank, quickly transferring the preheated blank to a forming press, realizing the initial forming of a curved surface by pressing a die cavity and a target curved surface under high pressure, arranging a semi-finished product on a working platform for shaping, performing plasma activation on a prefabricated insert, performing mechanical embedding and hot melt adhesive auxiliary bonding, performing pressure strengthening on a skin abnormal-shaped corner, performing nano coating spraying and curing, and naturally cooling a post-treated product to room temperature. According to the invention, the shearing strength is improved by the arrangement mode of matching the mechanical jogged and bonded composite structure, the mechanical jogged and chemically bonded composite connection structure is formed, the special-shaped corner is pressurized and strengthened by adopting a temperature-control hot pressing process, the cooling rate is controlled, the local shearing strength is improved, and the stability of the skin structure molding structure is improved.

Inventors

  • ZHANG DASHENG

Assignees

  • 长春城际轨道客车配件有限公司

Dates

Publication Date
20260505
Application Date
20260320

Claims (10)

  1. 1. The method for forming the three-dimensional complex curved surface skin structure is characterized by comprising the following specific steps of: Step S1, selecting a plastic blank, uniformly preheating the blank by adopting an infrared heating furnace, and adjusting the heating temperature according to the material; s2, rapidly transferring the preheated blank to a forming press, realizing the downward pressing preliminary forming of the curved surface by the die cavity and the target curved surface through high-pressure die pressing, and performing preliminary cooling; Step 3, arranging the semi-finished product on a working platform for shaping, performing plasma activation on the prefabricated insert, performing mechanical embedding and hot melt adhesive auxiliary bonding, performing pressure application and reinforcement on the special-shaped corner of the skin, performing plasma treatment on the side connecting surface and the outer surface of the skin, and performing nano coating spraying and curing; and S4, naturally cooling the post-treated product to room temperature, adopting a measuring instrument to detect the size, and carrying out secondary correction until the deviation outside the required range exists, so as to meet the requirements.
  2. 2. The method for forming a three-dimensional complex curved skin structure according to claim 1, wherein in the step S2, the fitting error between the mold cavity and the target curve is less than 0.05mm, and the forming pressure is applied for 8-10MPa, and the pressure is maintained for 10-15S, so that the material is stretched and the mold details are fitted.
  3. 3. The method for forming a three-dimensional complex curved skin structure according to claim 1, wherein the step of shaping the semi-finished product in the step S3 is as follows: S311, arranging a semi-finished product on a working platform through a sucker type mechanical arm, performing full-size scanning on the semi-finished product through a laser scanner to generate a deviation analysis report, performing dynamic balance correction and precision correction on a shape correction tool, then performing shape correction in stages, selecting a 800-mesh diamond grinding wheel in a rough correction stage, replacing a 1200-mesh cubic boron nitride grinding wheel in a fine correction stage, feeding back side profile deviation in real time through a laser range finder, automatically adjusting the feeding amount of the grinding wheel according to deviation data by a controller, and adopting high-pressure air cooling to remove cutting scraps in the shape correction process; S312, controlling the perpendicularity tolerance of the trimmed flanging structure of the semi-finished product to be +/-0.03 mm, removing burrs of the special-shaped corner structure by adopting deburring equipment, and polishing until the roughness Ra is less than or equal to 0.8 mu m, wherein the structural profile tolerance error of the arc-shaped edge is less than or equal to 0.04mm; S313, chamfering and additionally arranging transition chamfer at the special-shaped corner by adopting a numerical control chamfering machine at the top end of the flanging of the semi-finished product, and reinforcing the edges.
  4. 4. The method for forming a three-dimensional complex curved skin structure according to claim 1, wherein the steps of performing plasma activation and mechanical embedding and hot melt adhesive assisted bonding of the prefabricated insert in the step S3 are as follows: s321, selecting a plastic insert or a surface galvanized metal insert with good compatibility with a skin material for the prefabricated insert, placing the insert into plasma treatment equipment, adopting mixed gas of argon and oxygen, treating for 30-120S under the radio frequency power of 50-200W, and performing plasma activation on the prefabricated insert; s322, recognizing a positioning reference of a skin preset combination structure through a CCD camera, and pressing an insert into the preset repair skin structure through a servo press-fit device, wherein the fitting depth is equal to a preset assembly reference surface; S323, injecting EVA modified hot melt adhesive along a preset adhesive injection channel of the skin structure through a small adhesive injector, heating to 150-200 ℃ to enable the EVA modified hot melt adhesive to melt and fill gaps, and cooling to form a mechanical jogged and bonded composite connection structure.
  5. 5. The method for forming the three-dimensional complex curved surface skin structure according to claim 1, wherein the step S3 of pressurizing and strengthening the special-shaped corner of the skin comprises the steps of scanning the sharp corners and bending stress concentration areas of the curved surface of the skin through a stress detector, identifying the stress concentration areas, selecting a hot-pressing head with a polytetrafluoroethylene coating on the surface, arranging a heating element and a temperature sensor in the hot-pressing head, controlling the temperature to be +/-2 ℃, heating the hot-pressing head to 80-100 ℃, laminating the special-shaped corner of the skin, preheating for 2-3min, applying the pressure maintaining pressure of 2-3MPa, and ensuring the shearing strength at the corner of the skin to be more than or equal to 12MPa after heat preservation and pressure maintaining.
  6. 6. The method for forming the three-dimensional complex curved surface skin structure according to claim 1, wherein the step S3 of performing plasma treatment on the skin edge-side connecting surface and the outer surface, and performing nano-coating spraying and curing comprises the following steps: S331, removing greasy dirt and an oxidation layer on the surface of the skin by adopting a plasma processor aiming at the side connecting surface and the outer surface of the skin; S332, spraying a nano protective coating on the surface of the skin, wherein the thickness of the coating is 5-10 mu m by adopting an electrostatic spraying process; S333, baking the skin sprayed with the coating in a 120 ℃ baking oven for 20min, wherein the adhesive force of the coating is more than or equal to 5B grade, and the wear resistance is improved.
  7. 7. The method for forming the three-dimensional complex curved surface skin structure according to claim 6, wherein in the step S331, a plasma processor is used, the mixed gas of argon and oxygen with the volume ratio of 7:3 is selected, the power is controlled within the range of 300-600W, the treatment time is 90-120S, the treatment speed is 2-3mm/S, the content of detected oxygen elements after treatment is improved by more than or equal to 15%, the removal rate of oil stains and oxide layers on the surface is more than or equal to 99%, the surface roughness Ra is controlled within the range of 0.2-0.4 mu m, anhydrous ethanol is dipped in the mixed gas, and the surface is cleaned by using dust-free cloth, and the mixed gas is dried by hot air.
  8. 8. The method for forming the three-dimensional complex curved surface skin structure according to claim 6, wherein in the step S332, an Al 2 O 3 -TiO 2 composite nano coating is selected, 0.5-1% of graphene powder is added, the particle size of the coating slurry is less than or equal to 50nm through ball milling treatment, the surface of the skin is subjected to cross spraying through an electrostatic spraying machine, the spraying voltage is 30-50kV, the atomization pressure is 0.3-0.5MPa, the spraying distance is controlled within the range of 20-30cm, the spraying speed is controlled within the range of 5-8cm/S, the thickness deviation is less than or equal to +/-0.5 mu m, and the thickness detection is carried out every 2 mu m of spraying thickness in the spraying process.
  9. 9. The method for forming the three-dimensional complex curved surface skin structure according to claim 6, wherein in the step S333, the skin is preheated in an oven for 10min at 80 ℃ and then heated to 120 ℃ for baking for 20min, nitrogen atmosphere in the oven is kept in the curing process, after the curing is completed, the air is naturally cooled to room temperature along with the oven, the cooling time is more than or equal to 30min, 1500 mesh sand paper is adopted for slightly polishing the surface of the coating, the adhesion of the coating is more than or equal to 5B level, the abrasion loss through a Taber abrasion tester is less than or equal to 0.01g/1000 times, and the phenomena of peeling and falling off are avoided after 48h of salt spray test.
  10. 10. The method for forming the three-dimensional complex curved surface skin structure according to claim 1, wherein in the step S4, the skin product after finishing the post-treatment is placed in a constant temperature and humidity workshop for natural cooling to room temperature for 15-20min, key parameters of the dimensional accuracy and the connection position deviation of the complex side are detected by installing preset detection points through a three-coordinate measuring instrument, mechanical property detection and appearance detection are carried out by randomly extracting the product, if the dimensional deviation of the side is more than 0.04mm or the connection strength is less than 12MPa, the method returns to the step S3 for secondary correction, the technological parameters are adjusted according to the deviation type during correction until all indexes meet the requirements, and the qualified product is marked, packaged and put in storage.

Description

Forming method of three-dimensional complex curved surface skin structure Technical Field The invention relates to the technical field of skin forming, in particular to a three-dimensional complex curved surface skin structure forming method. Background The three-dimensional complex curved surface skin structure is widely applied to the fields of aerospace, automobile industry, high-end consumer electronics, medical appliances and the like, and not only needs to meet the structural requirements of light weight, high strength, high precision and the like, but also needs to have excellent appearance quality and environmental durability. The traditional skin forming process mainly depends on the hot press forming and vacuum plastic sucking technology, when facing three-dimensional complex curved surfaces with complex height and severe curvature change, such as automobile door skins and high-speed railway head skins, the traditional hot press or plastic sucking process is rough in material flow and pressure distribution uniformity control, is difficult to attach blanks to a die cavity, is easy to cause local thinning, wrinkling or detail characteristic loss, has large follow-up shaping allowance, affects final dimensional precision and assembly consistency, and is easy to generate stress concentration areas such as special-shaped corners, flanging and the like in the forming and cooling processes, micro cracks or strength weakening are easy to generate, the existing side-side connecting positions are weak, and the side-side connecting positions adopt a single bonding or button sewing structure, so that the falling phenomenon is easy to occur at the side-side connecting or flanging positions, and the stability of the skin structure forming structure is affected. Disclosure of Invention The invention aims to provide a three-dimensional complex curved surface skin structure forming method for solving the problems in the background technology. In order to achieve the purpose, the invention provides the following technical scheme that the method for forming the three-dimensional complex curved surface skin structure comprises the following specific steps: Step S1, selecting a plastic blank, uniformly preheating the blank by adopting an infrared heating furnace, and adjusting the heating temperature according to the material; s2, rapidly transferring the preheated blank to a forming press, realizing the downward pressing preliminary forming of the curved surface by the die cavity and the target curved surface through high-pressure die pressing, and performing preliminary cooling; Step 3, arranging the semi-finished product on a working platform for shaping, performing plasma activation on the prefabricated insert, performing mechanical embedding and hot melt adhesive auxiliary bonding, performing pressure application and reinforcement on the special-shaped corner of the skin, performing plasma treatment on the side connecting surface and the outer surface of the skin, and performing nano coating spraying and curing; and S4, naturally cooling the post-treated product to room temperature, adopting a measuring instrument to detect the size, and carrying out secondary correction until the deviation outside the required range exists, so as to meet the requirements. Preferably, in the step S2, the fit error between the mold cavity and the target curve is less than 0.05mm, the molding pressure of 8-10MPa is applied, and the pressure is maintained for 10-15S, so that the material is stretched and fit with the mold details. Preferably, the shaping step of the semi-finished product in the step S3 is as follows: S311, arranging a semi-finished product on a working platform through a sucker type mechanical arm, performing full-size scanning on the semi-finished product through a laser scanner to generate a deviation analysis report, performing dynamic balance correction and precision correction on a shape correction tool, then performing shape correction in stages, selecting a 800-mesh diamond grinding wheel in a rough correction stage, replacing a 1200-mesh cubic boron nitride grinding wheel in a fine correction stage, feeding back side profile deviation in real time through a laser range finder, automatically adjusting the feeding amount of the grinding wheel according to deviation data by a controller, and adopting high-pressure air cooling to remove cutting scraps in the shape correction process; S312, controlling the perpendicularity tolerance of the trimmed flanging structure of the semi-finished product to be +/-0.03 mm, removing burrs of the special-shaped corner structure by adopting deburring equipment, and polishing until the roughness Ra is less than or equal to 0.8 mu m, wherein the structural profile tolerance error of the arc-shaped edge is less than or equal to 0.04mm; S313, chamfering and additionally arranging transition chamfer at the special-shaped corner by adopting a numerical control chamfering machine at