What is the reason for the pressure difference in the upper cylinder of aluminum foil rolling mill?

The piston moves back and forth. According to the inquiry of Bohai Aluminum Co., Ltd., it is known that the reason for the pressure difference of the oil cylinder of aluminum foil rolling mill is caused by the piston moving back and forth. After the cylinder pressure difference is repaired, the pressure difference needs to be adjusted, and the pressure needs to be adjusted from low to high to meet the work. Aluminum foil roughing mill is a set of mechanical equipment in aluminum industry, which is mainly used for aluminum foil rolling, processing and refining.