CBM-OS packing scale imposes the screw to feed and weigh the material, it has two ways to ration the material, one is the net weight, and the other is gross weight. This device rations the material through adjusting the screw diameter. The drive of the slim screw is the frequency conversion motor. The output of the motor is controlled by the weight signal from the load cell. The feeding can be controlled separately by two or three steps. When feeding with high speed, the both thick and slim screw rotates quickly to feed. When feeding with low speed, the slim screw rotates slowly to feed accurately, stop feeding and to weigh and ration the material when beyond the preseted accuracy range