PC board hot bending, also called hot pressing, is a process in which PC board is heated to a certain temperature according to its thermoplastic properties, and plastic deformation occurs after softening.
PC board can be hot bending or cold bending, but because cold bending can only perform simple processing such as straight bending, it can do nothing for complex processing requirements such as arcs. However, if you don't pay attention during hot bending, blistering and whitening are easy to occur. How to avoid it?
The thermal deformation temperature of PC board is about 130°C (1.18MPa), and the glass transition temperature is about 150°C. Sheets can be thermoformed above this temperature.
Whether the PC board is processed with electric heating wire or oven, many times there will be blistering and whitening in the bending part, which will affect the appearance, and the whole will be scrapped, resulting in a high loss rate.
There are usually two reasons for blistering of boards
1. If the heating time of the PC board is too long/the temperature is too high, the board will foam (the temperature is too high, the inside starts to melt, and the outside air enters the inside of the board). Usually, the post-processing is not like the precise control of the temperature and heating time by the equipment when the plate is produced, and it can only be judged manually, so the bending generally needs to be completed by experienced professional workers.
2. PC sheet itself will absorb moisture, (under standard atmospheric pressure, 23℃, relative humidity 50%, the water absorption rate is 0.15%) Therefore, if the finished sheet has been stored for a long time, it will tend to absorb moisture in the air, if it is not before forming After removing the moisture, bubbles and misty micropores will appear in the product after molding, which will affect the appearance.
In order to avoid the abnormal situation caused by moisture, the sheet should be pre-dried at a lower temperature for a period of time before heating and forming. Usually, the moisture can be removed under the temperature setting of 110 ℃ ~ 120 ℃, and the water removal temperature should not be higher than 130°C to prevent the sheet from softening. The duration of moisture removal depends on the moisture content of the board, the thickness of the board and the drying temperature adopted. The dewatered sheet can be safely heated to 180~190℃ and can be easily deformed.
PC board bending is an indispensable process in PC board processing and production. As a production plant, it should comprehensively consider which process to choose according to the specific requirements of the product, and control the key points that are prone to problems. Bubble, standard size PC board products!