The last process of producing high-quality electrophoretic paint film, the workpiece after E-coating in a dust-free environment and the specified process temperature and insulation time, so that the coating film can curing. According to the heat transfer mode, it can be divided into conduction convection drying and radiation drying.
Conduction convection drying: Force convection circulating air to be delivered to the drying chamber at high speed through a heating source in order to quickly transfer heat to the workpiece and raise the metal to the temperature at which the coating film is effectively cured. However, in the initial stages of curing, the paint film is sticky and adheres to dust particles that come into contact with it. Therefore, the addition of air filtration helps to maintain the cleanliness of the drying chamber and to clean the drying chamber regularly to remove sedimentary dust that may be blown up by convective air.
Radiation heating is a special radiation heating element, up to a temperature several hundred degrees above the coating curing temperature, heat is conducted by light waves, and is absorbed by coated film and workpiece. The advantage of this technique is that the dust adhesive to the paint film is greatly reduced.
The better design is to combine radiation with conduction convection, i.e. an area with an inlet length of 30-40% of the total length of the drying chamber is designed as a radiant heating area with weak air convection, and the rest is a convection drying section. All drying chamber openings must have a mandatory hot air curtain to prevent heat loss and dust entering. Second, hot air should have multiple filtration systems before entering the drying chamber in order to reduce dust.
In addition, the temperature shown by the drying system is the oven air temperature, not the surface temperature of the workpiece, in order to make the workpiece curing completely, the furnace temperature tracking system should be used to measure the furnace temperature, the surface temperature of the workpiece to determine the oven air temperature that can make the workpiece completely cured.
The cleanliness of the drying chamber, the uniformity of the temperature, the accuracy of the temperature control and the drying time should meet the requirements of the process.
To determine whether the paint film is completely cured, using skimmed mian or gauze soaked with acetone or MIBK on the paint film with force (about 1 kg of force) to rub back and forth 30 times, and then observe the surface status of the paint film and if gauze is glued to the paint film. Paint film surface unchanged color, no loss of light, skimmed cotton or gauze non-stick color for qualified, curing incomplete coating film performance will be poor on hardness, adhesion, impact, and hinder the coating and curing of the following coating.
Finally, the drying workpiece should be forced to cool down to prevent smoke from affecting the environment. Generally speaking, as far as electrophoresis coating characteristics are concerned, cooling segments must not be designed, but only according to the time interval from the drying chamber to another station, depending on the plant site.