Open mill is the abbreviation of open plastic mill. In plastic products factories, people are used to calling it a two-roll mill. The open mill is a kind of plastic mixing equipment that has been used earlier in plastic products production plants. On the calender production line, the open mill is in front of the calender and after the mixer. Its function is to mix and plasticize the uniformly mixed raw materials, and to provide a more uniformly mixed and plasticized melt for the calendering of plastic products by the calender. When producing cable materials, the open mill can directly smelt and plasticize the powdery materials mixed according to the formula into molten materials, and then press and mold them into sheet-like tapes, so that the pelletizer can cut them into pellets. On the floor leather production line, it can directly provide a primer coating that is uniformly mixed and plasticized for cloth leather. The recycled waste plastic film (sheet) can also be re-plasticized on an open mill.

The open mill is simple in structure, easy to manufacture, easy to operate, easy to maintain and disassemble, so it is widely used in plastic products companies. The disadvantage is that the workers consume a lot of physical work, and need to use manual mixing to turn the mixed materials in a higher temperature environment, and the number of manual turning and mixing of plastic sheets has a greater impact on the quality of raw material mixing.