The first step in the powder coating process is to select the appropriate powder coating material. These materials should have good spraying performance, coverage, wear resistance, corrosion resistance and good environmental performance. Depending on the use of the product and the working environment, different types of powder coatings can be selected, such as cyclic resin powder, polyester powder, acrylic powder, etc.
Before carrying out powder spraying operations, it is necessary to ensure that the powder spraying equipment is in good working condition. Equipment settings include adjusting the angle, distance, powder spraying volume and other parameters of the spray gun to ensure that the powder can be sprayed evenly and stably on the surface of the workpiece. At the same time, the operating status of the equipment should be checked regularly to ensure the quality of spraying.
The pretreatment process is one of the most important parts of the powder spraying process. It will directly affect the quality of the powder coating. Poor pretreatment will cause the paint to easily fall off and bubble. Therefore, attention must be paid to preprocessing work. Before powder spraying, the surface of the workpiece needs to be treated to remove impurities such as oil, rust, dust, etc. Pre-treatment can use mechanical grinding, chemical cleaning and other methods. For product workpieces with rust/thick surfaces, use mechanical rust removal methods such as sandblasting and shot blasting. After mechanical rust removal, ensure that the surface of the workpiece is clean and free of scale. According to the degree of defects on the surface of the product workpiece, use conductive putty to scratch the defects, dry them thoroughly and smooth them with sandpaper before proceeding to the next process. If some parts of the workpiece do not require coating, they can be covered with protective glue before preheating to avoid spraying paint. Generally, no preheating is required. If a thicker coating is required, the workpiece can be preheated to 100~160℃, which can increase the coating thickness. The quality of surface pre-treatment directly affects the coating adhesion and appearance quality after powder spraying.
Powder spraying operation requires certain skills, including controlling the moving speed of the spray gun, spraying angle, spraying distance, etc. During operation, pay attention to maintaining a stable distance between the spray gun and the workpiece surface to avoid spraying too thick or too thin. At the same time, pay attention to the uniformity of spraying to avoid missing sprays or re-sprays.
The control of powder spraying thickness is an important part of the powder spraying process. The coating thickness can be controlled by adjusting the spray gun parameters, spraying times, spraying distance, etc. A coating that is too thick may cause problems such as cracking and blistering of the coating, while a coating that is too thin may affect the protective performance of the coating.
The sprayed workpiece is sent to a drying room at 180-200°C through a conveyor chain for heating, and is kept warm for a corresponding period of time (15-20 minutes) to melt, level and solidify, thereby obtaining the desired surface effect of the workpiece. Post-processing includes solidification treatment, cooling treatment, etc. Curing treatment can make the coating harder and more wear-resistant, while cooling treatment can prevent the coating from deforming or cracking during the curing process.
Quality inspection and evaluation are essential links in the powder spraying process. Check the appearance (whether it is smooth and bright, whether there are particles, shrinkage holes and other defects) and thickness (control between 55 and 90 μm). By testing the appearance quality, adhesion, hardness, wear resistance, etc. of the coating, the effect of the powder spraying process and product quality can be evaluated. At the same time, unqualified products must be reworked or scrapped in a timely manner.