1. Professional features of automobile dashboards, interior and exterior trims
China's automobile industry started in the 1950s, while the automobile decoration industry started in the 1980s. It started with the introduction of localization by Shanghai Santana, FAW-Volkswagen JETTA, and Wuhan Citroën Beverly. The localization projects for the decorative parts of these imported models are also mainly for civilian and general industrial plastic plants, carpet factories, textile factories, adhesive chemical plants, coating chemical plants, and some predecessor factories such as: Shanghai Yanfeng Machine Mould Factory (now Yanfeng Visteon), Shanghai Automobile Carpet Factory, Shandong Wendeng Automobile Carpet Factory, SAIC Motor, Changchun FAW Interior Parts Factory (now Fawer Johnson), Yangzhou Second Plastic Factory, etc. However, this industry developed very rapidly. From 1990 to 2000, the automotive decoration industry blossomed all over the country. A large number of state-owned backbone enterprises and a larger number of small and medium private enterprises have emerged. For example: Shanghai Yanfeng Visteon, Ningbo Huaxiang, Johnson/Lear everywhere, Taiwan Quanxing Sub-factory, Wuhan Yunhe, Changshu Automotive Interior Material Factory, Yantai China Resources, FAW Fawer Johnson, etc.
Technology development status
(1) Key, high-quality raw materials need to be imported. For example, the slush-molded PVC powder used in the production of high-end instrument panel skins is about 30 yuan/kg in France. The HMHDPE used to produce plastic fuel tanks must also be imported from Europe, America and Japan. The quality of domestic raw materials is not good enough. For example, Qilu Petrochemical imported 11,581,700 yuan per ton of HDPE technology produced by U.S. Union Carbon, which is very cheap.
(2) Key, high-quality equipment needs to be imported, such as: large high-pressure water cutting machine, high-end PU foaming assembly line, instrument panel skin slush molding equipment, etc.
(3) The larger the enterprise, the higher the dependence on foreign technology, equipment, molds, and tooling. On the contrary, those small and medium-sized enterprises are forced to do something in order to survive because their financial strength is not that great.
Talent development status
(1) I haven't heard of any university offering a course in automotive "decoration parts".
(2) Automotive decoration parts are a new and interdisciplinary subject, requiring technical personnel to understand the knowledge of automobiles, machinery, paint, adhesives, plastics, rubber, leather, textiles, and clothing.
(3) Technicians in this industry are generally "studied halfway". Many learn cars and machinery to make decorative parts and learn more by themselves. It's hard to go to school, but it's harder to learn by yourself.
(4) More engineers jumped from parts factory to main engine factory than from main engine factory to parts factory。
Two, car dashboard introduction
(1) Product structure, materials, standards, and equipment of the dashboard
ABS/PVC composite skin + PU foam + skeleton
●The skin is a plastic alloy, and the thickness is about 1.0-1.5mm, generally 1.2mm. Changchun Yisu production, about 18 yuan/kg. Popular standards: cold resistance -40°C, heat resistance 120°C; breaking elongation 150-240%; tensile strength 18-20N/mm2; Shore hardness 52-58. Rebound rate 30-35%; compression set rate (70 ℃, 50% compression, 22h) 12-15%
●PU foam (polyurethane semi-rigid foam), density 120 ± 30kg/m3
●Frame material: ABS injection molding, metal stamping and welding, or paper pulp. Heat distortion temperature ≥90 ℃
Professional features of automobile dashboards, interior and exterior trims, dashboard production process:
Skin heating→Skin molding→The skin is put into the lower foaming mold and the skeleton is placed on the upper foaming mold→Pour the PU mixture in proportion and quantitatively (100:42-50)→Clamping and foaming (mold temperature 25-45 ℃)→ After about 7-10 minutes, the mold is opened and the parts are taken, and then the auxiliary work is to cut the edges, make holes, and install some accessories.
Technical requirements for dashboard assembly:
●The appearance of the dashboard (including the skeleton) meets the requirements of drawings and digital models to meet assembly requirements.
●All raw materials must meet the corresponding requirements.
●The skin is uniform in color, non-dazzling, and free of impurities. Local skin lines are allowed to become lighter, but no light is allowed.
●Clear contour lines, smooth edge trimming, no damage on the surface, good adhesion of each layer, no peeling.
●Foam voids that affect the appearance are not allowed on the contour line, and foam voids not larger than Φ8 are allowed in the rest. Repairing is allowed if it does not affect the appearance.
●After the instrument panel is placed for 4 hours at a temperature of (100±3) ℃, there should be no abnormal phenomena such as damage, decrease in installation performance, decrease in strength, stickiness and peculiar smell, and the deformation of each part should not be greater than that before the test 3.0 mm. After 5 heat-resistant cycles, the instrument panel shall not be damaged, installation performance degradation, strength degradation, sticky parts and peculiar smells. Note: 100 ℃×1 h→room temperature×30 min→-30 ℃×1 h→room temperature×30 min is a cycle.
●Mechanical vibration resistance requirements: the instrument panel is at room temperature (20 ℃±2 ℃), high temperature (60 ℃±2 ℃), low temperature (-20 ℃±2 ℃), and the frequency conversion range is (8～50) Hz, acceleration is 35 m/s2, sweep time is 10 min up and down vibration, the resonance point is required to be above 35 Hz, and no resonance occurs in other frequency ranges.
Instrument panel slush plastic skin + PU foam + skeleton
Similar to a type structure, the difference is that the skin is made of PVC powder and slush molding machine. Higher cost, generally used in high-end cars, such as Audi A6.
Modified PP injection molding for dashboard
General modifications include E/P (EPDM ethylene propylene rubber), heat distortion temperature> 85 ℃ (4.64kg/cm2); tensile yield strength> 110 kg/cm2 glass fiber reinforced, inorganic (talc) filling. The glass fiber content is 20-30%, which improves the strength, heat resistance, weather resistance and impact resistance.
The equipment used is a large injection molding machine. The injection capacity is generally more than 10,000g depending on the size of the dashboard, and the clamping force is more than 1,800 tons.
Advantages: stable products, high efficiency, suitable for mass production.
Disadvantages: ◆ One-time mold and equipment investment is large. In case of product modification, the mold is likely to be scrapped at one time. ◆It is costly to realize product surface softening, and it needs to spray PP primer + PU elastic paint. The price of this kind of elastic paint is about 400 yuan/kg, and each instrument panel needs about 0.6kg, not counting the primer and thinner. Therefore, it is generally used in economical passenger cars, trucks, and special vehicles. Even the "Jetta" softened the dashboard.
Production process: Ingredients-heating-mold clamping-injection molding-pressure holding-cooling-mold opening-part picking-trimming
Other types of dashboard structure:
FRP (including hand lay-up, SMC, long glass fiber casting and molding), ABS plastic + spray paint, sheet metal stamping, etc., are not mainstream or low-grade, and tend to be eliminated. I won't talk about it here.
3. Structure design of automobile dashboard
a. Air volume distribution
Generally, the minimum air inlet area of the blowing face duct is 16,000 square millimeters, and each tuyere is 4,000 on average. The air intake area of the defrosting duct is 8000 square millimeters. The two side defrosts account for 2000 each, and the front windshield defrost port accounts for 4000. The opening position of the defrost port also has an experience value. The distance between the center line of the defrost port and the front edge of the dashboard in the X direction is determined by the angle between the windshield and the surface of the dashboard.
When the front windshield is at a 25-degree angle with the dashboard, the center of the front defrost port is 40~70mm away from the front edge of the dashboard. 45~60mm at 30°; 50~90mm at 35°; 60~100mm at 40°; 80~120mm at 45°; 110~140mm at 50°; 130~170mm at 55°; 170~225mm at 60°; 65 230~280mm in degrees.
The positions of the two side defrost openings are usually used to calculate the area on the side windows that needs to be defrosted by using the eye ellipse and the position of the rearview mirror during the general layout. Then roughly calculate the location of the defrost port based on this area and the direction of the wind.
After the above is determined, CFD analysis must be performed, and then the position and blade angle of each tuyere should be fine-tuned according to the analysis results. This is a repeated process. Until the initially determined target value is met. Then according to the recommendations of the CFD results, the final structural design was started.
Of course, all computer simulations are only a reference, and the final result depends on experimentation. After the development of general air conditioners is completed, bench tests are required to determine the defrosting effect. Of course this is also simulated. The most real thing is to do a ring mold test after the whole vehicle comes out.
(1) Product structure, materials, standards and equipment of steering wheel
a. PU self-skin foaming + skeleton molding
This is the current mainstream production process. After the foaming is completed, there is a dense skin on the surface. The skin thickness is 2-3mm, the density is 600-1200kg/m3; the elongation at break is 100-120%; the tearing strength is 4-8.5N/m2;
●The density of the core layer is 150-430kg/m3; the elongation at break is 80-90%.
●Frame: aluminum-magnesium alloy die-casting or welding of steel plate and steel bar.
●Forming equipment: PU foaming machine
●The production process is similar to the dashboard, so I won’t talk more about it. The most important thing is to pay attention to the temperature of the raw materials, the ratio, the uniform mixing, the uniform mold temperature, the selection of the release agent, the quality and variety of the mold skin.
PP or ABS injection molding rigid steering wheel
This kind of steering wheel feels bad and has poor vibration damping effect. Currently, it is only used on very low-end models, such as a 19,000 yuan Changan pickup truck.
Technical requirements for steering wheel assembly: (TL-VW 52045)
●Surface Shore Hardness: 75±10
●Temperature resistance resistance: 80 ℃ 168 hours 23 ℃, 2 hours-40 ℃, 168 hours. No cracks on the surface.
●Aging resistance: 480 hours of xenon lamp
●Strength requirements: torsion, compression, different types have different requirements.
●Steering wheels with airbags also have special requirements, such as blasting lines.
Seat structure: surface skin, foam cushion, frame assembly, angle adjuster, slide rail, spring...
Seat classification:
Single seat (headrest, backrest angle, seat cushion lifting, sliding back and forth...)
Double seat (headrest, backrest angle, backrest folding, overall flip...)
Three-person seat (headrest, recliner, 3/7 or 4/6 backrest split, flip...)
Skin: genuine leather, imitation leather, fabric, artificial leather (PU or PVC), flame retardant GB8410-2006 required
Foam pad: PU includes cold-cured high-resilience and hot-cured ordinary foam.
The former has a rebound rate of 70-80%, residual deformation after repeated compression (50%, 70 ℃, 22 hours): <8%, density 42-45kg/m3. Elongation at break: 100-130%. The latter's rebound rate and tear strength are very poor, and some add a lot of talc in order to reduce costs and increase hardness. Pu foam is basically used in low-end cars.
Special seat
●Child seat
●Disabled seat
●Multifunctional seat
Seat assembly
The skeleton assembly, angle adjuster, slide rail, and spring requirements meet the requirements of national standards
Seat inspection standards
Exterior
●Flat, no wrinkles, open lines, or damage. (The leather seat has no obvious wrinkles)
The whole seam should be relatively straight, no distortion, offset, straight stitches, no leaks, thread ends, and burrs. The seat, backrest, and pillow are all upright without distortion.
●Packing specification, uniform flanging.
Adjustment mechanism
●The angle adjuster is flexible, reliable in return, and there is no obvious movement after locking.
●The slideway can be adjusted freely, the limit is reliable, and there is no abnormal noise, jamming and obvious openness.
●The lock is reliable.
●Reliable waist limit.
●The headrest is flexible and securely locked.
3. Seat assembly
Production process: cutting-sewing-packaging-finished product-inspection-stamping-bending-welding-painting
a. Economical door trim panel: PVC artificial leather + fiberboard
This kind of door panel is still widely used in cheap cars. A set of 4 door inner panels for a pickup truck costs 130 yuan. Adopt high frequency heat sealing machine to compound. Fiberboard requires waterproofing. Water absorption: ≤ 30%
Design attention points:
●The matching gap between the periphery and the instrument panel, A-pillar decorative board, B-pillar decorative board (adhesive strip), threshold, inner triangle, etc., is generally 5-8mm, not too small. Interference easily occurs after assembly errors or deformation of hinges and car bodies occur.
Points to note in door panel design:
●Matching deviation between inner unlocking panel and interior trim panel (height, horizontal direction)
●The position of the inner lock lifting button is off.
●Good coordination in design, cracks after shrinking at low temperature. Keep a good fit clearance of 0.3-0.5mm and connect with elastic elements.
●Pay attention to the convenience of the space behind the door light and the installation direction of the plug.
● It is absolutely necessary to design the matching relationship between the nylon buckle and the door trim panel and sheet metal. Once the injection mold of the interior panel substrate is opened, the height and position of the buckle seat are difficult to change. The problem of over-tightening and over-loose buckle is most likely to occur. Too loose, there will be gaps; too tight, easy to snap when opening and closing the door.
Even Changan Ford's FOX door panel is not doing well, everyone has the opportunity to observe FOX.
ABS injection molding substrate + special adhesive + PVC skin production process:
ABS substrate (with a lot of small holes of Φ1.2 on it)-glue spray-PVC artificial leather heating (140 ℃, 30s)-vacuum adsorption skin-cooling-edging-assembly accessories-inspection-packaging
Main technical requirements:
●-40 －90℃ for 6 hours without opening the glue.
●－40 ℃, no cracking in 24 hours.
In addition to paying attention to the problem of clearance with surrounding parts, the following issues should also be noted:
●No dead ends, R must not be less than 10
●Molding substrate + adhesive + fabric, and sound-absorbing and heat-insulating materials can be attached to the back.
●Forming process: molding
●Production equipment: large-table press (100-200 tons), steel or aluminum alloy mold (with or without cutting edge), oven or mold heating.
●Raw materials: The fabric can be 180-210g/m2 non-woven fabric, weft-knitted or warp-knitted fabric, and breathable artificial leather. The substrate can be PU, PS, PP, PVC foam board, corrugated cardboard, etc. Sound-absorbing and heat-insulating materials are generally XPE foam, PU foam, waste spinning felt, etc., which are pasted in pieces, and the thickness is generally more than 10mm.
Attention in ceiling design
●The ceiling and the decorative panels of each column adopt a crimping structure, and the width of the overlapping side is 15-20mm.
●Handles, sun visors, and ceiling lights must have suitable hidden positions.
●Sufficient lifting points and reasonable shapes must be set up. The collapse and deformation of the ceiling are often encountered.
●The size of the ceiling is large, and it is easy to be inclined outward during installation. A positioning point (mounting hole) with a larger span should be set.
8. Car carpets, front wall insulation pads
The production process of carpets and front wall insulation pads is similar to that of ceilings, and they are also pressed by a press and mold. The carpets currently supplied generally have EVA and PE back coatings, which are melted during thermo-compression molding and bonded with the waste spinning felt. There is also a high-grade molded carpet, which is treated with "back foaming process"
Nine, car cover insulation pad
The structure of the cover insulation pad is relatively simple, generally a three-layer structure, with about 50-80g/m2 PET non-woven fabric on both sides, and resin glass wool in the middle layer.
The mold is heated to 180°C and held under the pressure of the press for approximately 10 minutes.
This resin cotton is a thermosetting material and can only be processed at one time.
When designing the product structure, the draft angle must also be considered, and there must be no dead ends. The round angle is generally greater than R10.
●The structure of the sun visor: skeleton + cushion material + skin + accessories
●Frame type: metal wire + cardboard; metal wire + PU foam; injection frame.
●Cushion material: PU foam, XPE foam, etc.
●Skin: Generally, it is PVC artificial leather and cloth, which must meet the flame retardant requirements of GB8410-2006.
●Accessories: vanity mirror, bracket, etc.
●Production process: high frequency heat sealing and in-mold foaming (self-skinning)
The coating system of the decorative anticorrosive coating of automobile exterior parts is: Cu≥30 μm, Ni≥15 μm, Cr≥0.8 μm; the chromium coating should be micro-cracked chromium, and the number of micro-cracks should be 250～800/cm . The coating should pass +100 ℃, 30 min-standard ambient temperature, 30 min→-40 ℃, 4 h thermal cycle test; corrosion resistance should pass the corrosion paste test (DIN 50958 standard) 5×16 cycles, moisture resistance should Pass DIN 50017KFW standard for 48 hours, the appearance of the coating should be uniform and high gloss.
Process flow: eliminate internal stress → degreasing → water washing → chemical roughening → water washing → reduction → water washing → colloidal palladium activation → water washing → degumming → water washing → pre-nickel plating → water washing → acid bright copper plating → water washing → film removal → bright Nickel → water washing → chrome plating → water washing → drying → partial black paint spraying → drying
The advantages and disadvantages of electroplating signs:
(1) The coating is bright and has excellent wear resistance. It adopts double nickel and microcrack chrome coating system, and the corrosion resistance of the coating can pass the TL-VW528/B standard. The surface can be chrome-plated or gold-plated with good decoration.
(2) Serious environmental pollution; complex process, low pass rate at one time, high production cost; relatively monotonous coating pattern, it is difficult to plate a matte coating with uniform silk patterns; poor adhesion of partial spray paint on the coating , The phenomenon of partial paint film peeling often occurs in use.
(3) Electroplating signs are generally used on the front signs of high-end cars. However, if the plating structure does not strictly implement the TL-VW528/B standard and adopts a single-layer nickel electroplating process of thick copper and thin nickel, the plating will often be skinned and blistered during long-term use, resulting in green rust, which will seriously damage the shape of the vehicle.
●Production process: multilayer blow molding, generally 5-6 layers.
●Material: high molecular weight high density polyethylene (HMHDPE), molecular weight 500,000-600000, density 0.945, cold resistance-40 ℃, heat resistance 130 ℃. Main raw material producers and grades: German BASF 4261A, American PHILLIPS HXM50100, Japan Tonen Petrochemical B5742, France SCLVAY ELTEXRSB71
●Technical requirements
Gasoline penetration: <20g / 24h
Drop test:-40 ℃, full load, 6m free fall without damage.
Flame retardant test: flame burns for 60s, evacuate the fire source is thick, no gasoline leaks.
