???????The uneven thickness of the stretched film is mainly caused by two conditions: the thickness of the film itself from the calender is uneven, resulting in different thickness of the stretched product; during the stretching process, due to air convection, the transverse temperature of the film is different. The film thickness after stretching is different, resulting in different thickness of the finished material roll in the lateral direction.
???????It can be solved by adjusting the four-roll calender. Specifically, the shaft crossing device of the middle roller and the reverse bending device of the lower wheel can be adjusted; in addition, the stock between the rollers must be controlled to avoid the cold material from entering and affecting the uniformity of the film stretching Sex. The diameter of the front wheel and upper wheel is not more than 250mm, the upper and middle wheels are 15 ~ 30mm, and the middle and lower wheels are 10 ~ 15mm. The situation is that due to the different air convection in the transverse direction, the temperature of each point of the film is different, so the thickness of the stretched film is not uniform in the transverse direction.
???????According to practical experience, the ends of the film are generally thicker, because the air convection on both sides is faster than the middle, so the temperature on both sides is lower. Therefore, the film can also be used to cover both sides of the widening machine. If the above methods cannot solve the problem, a jet tube can be installed to make up. It is placed in the horizontal direction at a distance of 150mm from the film, and the nozzle is required to be duck-billed. There is a micro-valve to adjust the exhaust volume, so that the air flow is relatively soft. Where the film is thin, the large exhaust valve can be opened appropriately, and in the other places, the exhaust valve should be closed.