At present, in the process of car repair, color change and refurbishment painting, most car owners require scraping putty . The quality of putty scraping has a great influence on the flatness of the coating, so it is necessary to scrape the putty well to lay a good foundation for improving the flatness of the coating film.
(1) Plane scraping method
When scraping flat surfaces such as the engine cover of a car, the door of a luxury bus, the rear cargo door, and the doors on both sides, you can use a relatively large copper scraper or steel scraper. Good putty is quickly scraped on the surface of the object, and after each side is full , the gray surface is recovered and scraped immediately. When scraping the gray surface, only gently scrape 1-2 back and forth at each place, and do not scrape too many times or use too much force, otherwise curling or delamination will easily occur. After scraping and smoothing each side, clean up the residual ash on the surrounding edges in time to prevent it from affecting the smoothing after drying. Carry out side by side in this way, and scrape each plane of the car in turn, scrape solid, scrape flat, and scrape neatly.
For surfaces with good flatness such as the exterior of luxury passenger car doors and the exterior of warehouse doors, after one side is fully scraped (full scrape), immediately switch to a special long aluminum scraper or long plywood scraper to evenly apply force to the gray surface. Scrape the ground (scrape up and down) evenly. When scraping, the force of both hands should be uniform. One hand should not use heavy force while the other hand should use light force. Otherwise, the dust layer after scraping will tend to be thick on one side and thin on the other. unpleasant sight. The front and back scraping time of each side should be controlled within (3-4) minutes, and the longest should not exceed 5 minutes, in case the gray layer solidifies (shows signs of drying) and causes curling or peeling off. This scraping method is mainly suitable for painters who are more skilled in scraping technology. For those who are not skilled in scraping, it is better to use copper or steel scraper to scrape in sections to prevent or waste of raw materials.
(2) Curved object surface scraping method
Arc-shaped surfaces such as the side surface of the car cover, the wheel cover, the arc-shaped door, etc.; the upper part and four corners of the front and rear walls of the passenger car, and the bumper; the arc-shaped parts of the truck cab, etc. Steel scraper (or copper scraper) can be used for scraping coating, or a combination of steel scraper and rubber scraper can be used scraping coating.
When scraping with a steel scraper, the first coat of putty can be scraped along the length of the arc-shaped surface, and the second coat of putty should be scraped along the transverse direction of the arc-shaped surface, so that it can be scraped alternately until the quality requirements are met Flatness. When scraping along the length, scrape all the way to the head of the 50-60 cm long surface at one time, and do not stay in the middle, so as not to leave an overlap. When scraping a surface about 1 meter long , it can be scraped in sections, and the overlapping parts should not be too obvious. In this way, the object surface of the arc-shaped part of the car is scraped and leveled in turn, and the residue on the edges can be collected. When scraping horizontally, it should be scraped from one side of the arc surface to the other side, so that the knife is pressed one by one for scraping. For the arc-shaped parts on both sides of the rear wall of a large bus, that is, the oval parts, due to the large arc, it can be scraped from both sides of the arc to the middle, and scraped from top to bottom in this way.
When using a combination of steel scraper and rubber scraper, it is better to scrape the first layer of putty with a steel (or copper) scraper, because the elasticity of the rubber scraper is too large, and it is not easy to spread the bottom ash ). After the first coat of putty is dry and polished, use a rubber scraper to scrape the second and third coats (usually the putty needs to be scraped three coats), so that the quality of scraping can be easily achieved.
(3) Scrape coating method on the surface of special-shaped objects
Special-shaped surfaces, such as the front and rear light frames of cars and buses, and the front cover of buses, etc., need to be scraped scraping. The shape of the object surface, the force of the hand should be light and heavy, that is, the force of the hand should be light when scraping uneven parts such as pits, and the force of the hand should be heavy when scraping the uneven parts, so that the flatness of the coating after scraping can be consistent . If the hand is too hard in the pit, there will only be a small amount of dust layer in the pit, which will not expected smoothing effect. When scraping the surface with light force, a thick layer of dust will be left on the surface, which not only wastes atomic ash , but also adds trouble to the polishing after the coating dries (difficult to polish). After scraping the surface of various shaped objects with a rubber scraper, use a gray knife or a steel scraper to clean up the residue on the surface and edges in time to prevent slag formation after drying and affect the polishing.
Putty putty usually needs to be scraped 2-3 times (the thickness of each layer of ash is preferably 0.5-1 mm), so as to smooth the defects on the surface of the base layer. For the parts with poor flatness of the base layer, sometimes 3- Only 4 or 5-6 coats of putty can fully smooth out the defects.
