Paint repair process:
(1) Determine the maintenance scope:
Examine the damaged parts carefully. If the damaged parts exceed one third of the parts, they should be repaired by over-repair. Over-repair is to spray a part of the varnish on it, and then paint it from the damaged part to the original part, so as to keep the original car color paint to the maximum extent and avoid the color difference problem. Because one-third of the damage has been polished, primed, painted, painted and lapped, more than two-thirds of the damage, and the rest is few, it loses the significance of repair.
(2) Determine the degree of injury:
If it is a shallow scratch, you don't need to be putty. It can be polished directly until there is no trace, and then the next step can be carried out. If it is a deep scratch or a small pit, it needs to be putty. If it is deformed, you need to do sheet metal processing. Putty can be dried in one minute with imported quick-drying putty.
(3) Construction protection:
Prepare relevant materials and tools, and stick the parts other than the damaged parts with adhesive tape, especially the corner parts, to prevent unnecessary damage during grinding.
(4) the underlying processing:
Clean up the silt around the damaged part. If the scratch is deep, putty is needed. When using putty, the damaged part should be roughened with P240 sandpaper to improve the adhesion of putty. According to the damage situation, take a proper amount of putty and curing agent and mix them evenly (ratio: putty 100: curing agent 2-4 can be determined according to the temperature at that time). When scraping ash, squeeze out the pits or scars first, and then scrape the parts at 45 degrees, slightly higher than the surface of the parts. After drying, smooth it with P320 sandpaper, then smooth it with P800 sandpaper, and then spray primer. If it is a shallow scratch, you can directly polish the damaged area with P320 sandpaper (it is best to use dust-free dry grinding equipment to improve the speed and reduce the problem of dirty water in the workshop), and the radius from the damaged center to the feathered edge is 60- 100MM (the herringbone does not feel concave and convex), and then polish it with P800 sandpaper (to improve the adhesion of primer and the quality of spraying). Use * * * * to clean the Shui Ze and dust between the surface and the gap, cover the damaged parts with textured paper with a radius of 80CM, and spray primer. When spraying the primer, pay attention to the fact that the air pressure should not be too high, and it should be controlled within 2KPa and half wet (the putty must be dried thoroughly, otherwise it will bite the paint). After the primer is dried (it can be baked with iodine tungsten lamp to speed up the drying), carefully check whether there are any small trachoma. If there is, it should be treated with caulking ash, and then the primer and the area to be sprayed should be polished smoothly with 1000# sandpaper, and the interface should be carefully polished with P2000# sandpaper to make the interface better integrated. (The interface should be selected in a narrow place next to the damaged part to reduce the time for processing the interface, and the interface should be 300MM away from the edge of the primer to extend the polishing range as much as possible and reserve enough extra space).
(5) Shading and degreasing:
Blow the Shui Ze and dust in the gaps of the parts with a pneumatic gun first, then carefully cover the parts except the spraying parts with masking paper (covering all parts except the construction parts to prevent paint mist from falling on other parts, which will bring unnecessary cleaning work), then wipe the spraying parts with a paper towel dipped with a little degreasing agent (it needs to be wiped on a large area to remove surface oil stains), and then carefully wipe the spraying parts with a dusting cloth and a pneumatic grab to spray colored paint.
(6) painting:
Dilute the prepared colored paint, fully stir (the ratio of colored paint to diluent is 1: 1), and filter. Pay attention to the control range when spraying. Adjust the air pressure to 2 KPa, dry spray, and wipe it with a special dust removal cloth (wipe the silver powder suspended on the surface and the silver powder accumulated at the corners). Cover the primer first, and gradually transition outward (iodine tungsten lamp can be used to observe whether it is completely covered when spraying) until there is no color difference. Pure black paint can be simply transitioned).
(7) Spraying varnish:
Confirm that the paint has no color difference, and after it is completely dried, you can spray varnish. According to the size of the spraying area, pour a proper amount of bright oil and add an initiator (bright oil 10: initiator 1) to spray at a pressure of 2-2.5KPa, lightly spray for the first time, and let it stand for 1-2 minutes according to the temperature (short standing time at high temperature and long standing time at the bottom of temperature), and then spray for the second time. When spraying for the second time, the gun should be compacted slowly, and the gun should be sprayed with two molecules overlapping (the gun speed depends on the amount of paint, 40-60CM per second). After spraying, check whether there is any missing spraying place, especially the corner parts, and then refute it. (varnish should not be sprayed too thick, otherwise it will affect the drying speed and cause waste. )
(8) Refueling treatment:
After painting varnish, it should be treated as butt joint. Mix bright oil mixed with initiator with butt joint in proportion (mixed bright oil 1: butt joint 10) and spray it at the joint. When spraying, the air pressure should be slightly higher, and the transition between the new paint and the original paint should be uniform, and it should not be sprayed too thick.
(9) baking:
Turn on the power supply of UV baking lamp before spraying, and place the baking lamp according to the spraying position for easy operation. Turn on the baking lamp 3 minutes after spraying varnish, because it takes 5 minutes for the varnish to settle down and 1-2 minutes for the baking lamp to warm up. It can be baked after preheating. Wear special goggles or glasses when baking, bake the edges first and then the middle to improve the speed, and bake at a distance for the first time to prevent it from drying too fast. When the baking lamp moves to 20-25CM away from the parts evenly, don't stop at the baking place to prevent the temperature from being too high. A small area can be done in 7-9 seconds, and a large area will take a long time. You can feel whether the varnish is dry on the textured paper by hand, and then touch it on the paint surface by hand. If it feels smooth, it means dry, otherwise it needs to be done again.
(10) grinding and polishing:
Start-up and quick repair process: quick drying and polishing.
After baking and drying, remove the masking paper and polish the paint surface with 2000# beauty sandpaper to remove dirt and tear marks. When grinding, gently grind the joint (pay attention to prevent unnecessary rework caused by grinding new scratches with gravel). After polishing, use high-speed polishing machine and special abrasive to polish. After polishing, first use medium-coarse abrasive to polish, and then use microcrystalline abrasive to polish until it reaches full luster. The interface should be polished properly, and it will be exposed after passing the interface. Clean up the side seams between the parts and the body and you can deliver the car.
Matters needing attention in quick repair:
(1) Primer: Before painting varnish, the substrate must be thoroughly dried before painting varnish, otherwise the paint surface will lose luster easily.
(2) Color paint: One-component color paint must be used for quick repair.
(3) varnish: the spraying air pressure should not be too high (2-2.5KPa), and the standing time should be 1-2 minutes each time, depending on the spraying environment temperature. The lower the temperature, the longer the standing time and the shorter the standing time. Spraying thickness 1.5-2 times should not be too thick, otherwise it is not easy to dry. After the varnish is sprayed, it must stand for 5 minutes before baking.
(4) Baking: the distance between the ultraviolet lamp and the parts should be 20-25cm. Too far away, curing is too slow, too close, curing is fast, but shrinking is fast, which is prone to orange lines and loss of light. For the convex and concave parts and bending parts of the parts, the baking angle should be changed according to the shape and cannot be omitted. When the UV lamp is cut off or turned off during baking, it cannot be turned on immediately. It takes a few minutes to open the lamp, because the temperature of the lamp is very high, and it can't be opened until the temperature drops. When ultraviolet rays are harmful to eyes, please wear special protective masks or glasses.
(5) Polishing: When polishing, use P 1500-P2000 beauty sandpaper to polish the dust spots completely until they are dull (it is recommended to use dry grinding equipment, if it is water mill, use more water to prevent sand and gravel from scratching), and lightly grind the joints.
(6) Polishing: The newly sprayed paint surface cannot be cured to 100% after drying, so it is not advisable to polish a single area for too long, and the surface cannot be overheated by touching it with hands. If the polishing time is too long, the paint surface will overheat, which may lead to the loss of luster.
(7) Abrasive: Abrasive containing no silicon or wax should be used, otherwise there will be pits and pits on the surface when spraying varnish, which may be polished lightly or cause rework.
Solutions to common problems:
(1) gloss loss: it can be recovered by high-speed polishing machine and special abrasive polishing, and there will be no gloss loss in the future.
(2) Reaction (paint biting): Because the substrate is not dry, it is wet sprayed when spraying, or the original spraying is self-painted with inferior paint, and the chemical reaction during spraying will cause paint biting. In case of paint biting, iodine tungsten lamp should be used to dry this part first, and then P 1500-P2000 water mill sandpaper should be used to smooth the bitten part. After drying, you can continue to spray paint. If there is a reaction, you can spray the paint again.
(3) Too big orange stripes: Too big air pressure or too fast gun running will lead to too big orange stripes, so the air pressure should be adjusted slowly when 2KPa gun is running, and only one-half of it can be pressed for overlapping spraying. If the orange lines are found to be large after baking, they should be solved by grinding and polishing.
(4) Color difference: For some special colors, try spraying first and then spraying. When repairing, try to keep the primary color paint under the condition of ensuring the spraying requirements, and the color difference problem can be solved by excessive repair.
(5) Tearing and dirty spots: the dirty spots and tears after spraying can be polished, and the hard surface of the mat can be polished with P 1500 water sandpaper, then the soft surface can be polished, and then it can be polished after leveling.