Metal sign making and coloring

Anyone who has made metal signs knows that metal signs are generally required to have a concave and convex effect. This is to make the sign have a certain three-dimensional and layered feel, and more importantly, to avoid frequent wiping that may cause the graphic content to blur or even fade. This concave-convex effect is generally achieved through etching methods (chemical etching, electrolytic etching, laser etching, etc.). Among various etching methods, chemical etching is the mainstream. So whether it is in this type of literature or According to the acronym of insiders, if there is no other explanation, the so-called “etching” refers to chemical etching.

The production process of metal signs consists of the following three main links, namely:

1. Graphic and text formation (also called graphic and text transfer);

2. Graphic and text etching;

3. Graphic and text coloring.
1. Formation of pictures and texts
To etch graphics and text content on a blank metal plate, there is no doubt that the graphics and text content must first be formed (or transferred to the metal plate) with a certain material and in a certain way. Generally, the graphics and text content is generally formed as follows: The following methods:
1. Computer engraving is to first design the required graphics or text on the computer, and then use a computer engraving machine (a cutting plotter) to engrave the graphics and text on the sticker, and then paste the engraved sticker onto the blank On the metal plate, remove the sticker on the part that needs to be etched to expose the metal texture, and then etch. This method is still widely used. Its advantages are simple process, low cost and easy operation. However, it suffers from certain limitations in terms of accuracy. Limitations: Because the smallest text that a general engraving machine can engrave is about 1CM, any smaller text will be deformed and out of shape, making it unusable. Therefore, this method is mainly used to make metal signs with larger graphics and text. For text that is too small, Metal signs with too detailed and complex graphics and text are useless.
2. Photosensitive method (divided into direct method and indirect method
①. Direct method: First make the graphic content into a piece of black and white film (film to be used later), then apply a layer of photosensitive resist ink on the blank metal plate, and then dry it. After drying, cover the film on the metal plate On the machine, it is exposed on a special exposure machine (printing machine), and then developed in a special developer. After development, the resist ink in the unexposed areas is dissolved and washed away, revealing the true face of the metal. The exposed areas Due to the photochemical reaction, the photoresist ink forms a film that firmly adheres to the metal plate, protecting this part of the metal surface from being etched.

②Indirect method: The indirect method is also called the silk screen method. It is to first make the graphic content into a silk screen printing plate, and then print a resist ink on the metal plate. In this way, a resist layer with graphics and text is formed on the metal plate, and then dried and etched… Direct method and Principles for selecting the indirect method: The direct method has high graphics and text accuracy and high quality.
Good, easy to operate, but the efficiency is lower when the batch size is large, and the cost is higher than the indirect method. The indirect method is relatively less accurate in graphics and text, but has low cost and high efficiency, and is suitable for use in large batches.
2. Graphic etching
The purpose of etching is to dent the area with graphics and text on the metal plate (or conversely, to make the sign appear concave and convex. One is for aesthetics, and the other is to make the pigment filled with graphics and text lower than the surface of the sign, so as to avoid frequent wiping and wiping the color. Erase. There are three main ways of etching: electrolytic etching, chemical etching, and laser etching.
3. Coloring of pictures and texts (coloring, painting
The purpose of coloring is to create a sharp contrast between the graphics and text of the sign and the layout, so as to enhance the eye-catching and aesthetic feeling. There are mainly the following methods for coloring:
1. Manual coloring (commonly known as dotting, brushing or tracing: using needles, brushes, brushes and other tools to fill in the dented areas with colored paint after etching. This method was used in badges and enamel crafts in the past. Features The process is primitive, inefficient, requires a lot of work, and requires skilled work experience. However, from the current point of view, this method still has a place in the signage process, especially those with trademarks, which tend to have more colors near the trademark. , and they are very close to each other. In this case, it is a good choice for hand coloring.
2. Spray painting: Use self-adhesive as a sign with a protective film. After the sign is etched, it is washed and dried, and then you can spray paint on the recessed graphics and text. The equipment used for spray painting is an air machine and a spray gun, but Self-spray paint can also be used. After the paint is dry, you can peel off the protective film of the sticker, so that the excess paint sprayed on the sticker will be removed naturally. Signs that use photosensitive resist ink or screen printing resist etching ink as a protective layer must first remove the protective ink before painting. This is because the ink protective layer cannot be removed like the self-adhesive protective layer, so the ink must be removed first. The specific method is: after the sign is etched, first use potion to remove the resist ink → wash → dry, and then use a spray gun to evenly spray the areas that need to be colored (that is, the areas with graphics and text, and of course the areas that do not need to be sprayed) Spray paint, which requires the next process: scraping and grinding.

Paint scraping is to use metal blades, hard plastics and other sharp objects against the surface of the sign to scrape off excess paint on the surface of the sign. To sand off the paint is to use sandpaper to remove the excess paint. Generally, scraping paint and grinding paint are often used together.
The spray painting method is much more efficient than manual painting, so it is still widely used and is the most commonly used method in the sign industry. However, since general paints use organic solvents to dilute,
The air pollution caused by spray painting is serious, and the workers are even more affected by it. What is even more annoying is that the scraping and grinding of the paint in the later period is very troublesome. If you are not careful, you will scratch the paint film, and then you have to repair it manually, and After scraping paint, the metal surface still needs to be polished, varnished, and baked, which makes people in the industry feel quite headache and helpless.
3. Electrophoresis coloring: Its working principle is that the charged paint particles swim toward the oppositely charged electrode under the action of electric current (quite like swimming, so it is called electrophoresis. The metal workpiece is immersed in the electrophoresis paint liquid, and after being energized, The cationic coating particles move toward the cathode workpiece, and the anionic coating particles move toward the anode, and then deposit on the workpiece, forming a uniform and continuous coating film on the surface of the workpiece. Electrophoretic coating is a special coating film formation method that uses environmentally friendly Electrophoretic paint is non-toxic and harmless. It uses water as a diluent. There is no need to spray, paint or brush. It also eliminates the headache of scraping, grinding and polishing processes. It is fully automatic and very easy to color. It is fast and efficient, and can load a batch (from a few pieces to dozens of pieces) every 1 to 3 minutes. After cleaning and baking, the paint film of the signs painted with electrophoretic paint is even and shiny, and is very strong and not easy to fade. Paint cost It is cheap and costs about 0.07 yuan per 100CM2. What is even more gratifying is that it easily solves the coloring problem after etching of mirror metal signs that has troubled the sign industry for decades! As mentioned before, making metal signs generally requires spray painting , and then scrape and polish the paint, but mirror metal materials (such as mirror stainless steel plates, mirror titanium plates, etc.) are as bright as mirrors and cannot be scraped or polished when spray-painted. This sets up a huge obstacle for people to make mirror metal signs! This It is also the main reason why high-end and bright mirror metal signs (with small pictures and text) have always been rare.

Post time: Jan-23-2024