Chipper is a kind of machine that cuts logs needed to produce wood pulp into wood chips of certain specifications, which can be divided into disc type and drum type. Cooker is a kind of equipment that dissolves lignin in paper-making raw materials into cooking liquor and separates paper-making raw materials into fibers, which can be divided into intermittent type and continuous type. Wood mill is a kind of equipment for producing wood pulp, according to the producer. It can be divided into intermittent type and continuous type. According to the way of log compression, it can be divided into hydraulic pressure type and mechanical pressure type.