Powder coating line matters MDF powder coating
Powder coating line have proven to be the most important factor in obtaining high quality MDF powder coatings. Unfortunately for small metal surface powder coating companies, it is not possible to get high quality MDF powder coatings in old metal powder coating lines
The most important part of the powder coating line is the oven technology oven paint melting. In case of thermal curing powder chemical curing. The thing to keep in mind is the low thermal conductivity of MDF. Therefore, ovens need to be designed so that their temperature can be distributed evenly; otherwise, the heat will not be distributed across the substrate surface like aluminum. However, when heating on MDF, a uniform surface temperature distribution must be ensured
We just took advantage of this due to the low thermal conductivity of MDF. As mentioned earlier, the powder melts and solidifies at the appropriate temperature. This temperature is more frequent than MDF can handle. However, when the powder is heated by infrared rays, the powder and the board surface quickly reach the temperature of melting and solidification. Due to the slow thermal conductivity of the board, the center temperature of the board is still relatively low, much lower than the temperature at which the entire powder is melted and solidified. Therefore, thermal stress in the MDF board is minimized without causing damage
We can see that the two ovens introduced above are thermal curing and UV curing melt curing, which are not suitable for MDF powder coating. Conventional all-powder thermal curing and MDF heating take a long time to reach 150-160 degrees due to the low thermal conductivity of MDF. As a result, the powder has not been fully cured and the MDF has been damaged. Other UV curing, so far in order to achieve a uniform distribution of UV intensity and dose, at the same time the degree of curing of different colors, different powder coating thickness. Therefore, UV curing has not yet successfully used the example of MDF powder coating. However, UV curing is used for MDF powder coating of transparent powder based optical layers (not detailed in this example).
A successful application for melting and curing of MDF powder coatings is an infrared oven. The challenge is to provide uniform IR exposure to the MDF surface, including the edges. Fortunately, modern infrared ovens have a high level of uniform radiation. Figure 6 is the surface temperature distribution map measured by the upper, middle and lower temperature sensors of the infrared oven MDF. The temperature distribution on the MDF surface varies very little, and the temperature range is less than 15°F
A well-designed IR curing oven showing temperature changes below 15°F from top to bottom of MDF substrate
In order to obtain a good powder coating, the temperature distribution in the oven must be measured before starting the powder coating. Measure and monitor not only at the surface location, but also around the MDF surface, including its edges. Oven temperatures should be adjusted to avoid temperature differences between locations exceeding limits, such as less than 15°F. Figure 7 is the two temperature distributions in panels a and b. Figure 7a is a conditioning well infrared oven; the sensor is fixed at various locations on the MDF surface, including the edges. We can see that the temperature distribution on the MDF surface is very uniform.
Obviously, MDF ovens with surface temperature set changes greater than 75°F will not achieve uniform powder coating performance. In some cases, even a uniform temperature distribution cannot be achieved due to technical deficiencies in the oven. In other cases, well-designed ovens are set at the right temperature. These situations lead to the fact that powder coatings should not be used in production and in many cases lead to the failure of MDF powder coatings.
On a given substrate size (including edges), melt – maximum temperature of the curing oven, good discussion, and strict rules before making any decisions with the manufacturer. Once the oven is installed, the setup of the production line must be optimized through temperature profile measurement and continuous temperature profile monitoring during production. This will ensure that the quality of the powder coating is within specification.
Powder coating line matters MDF powder coating