Bubble bag machine manufacturers believe that the traditional bubble film machine uses a fixed pump to supply oil, and the manufacturing process has different requirements for speed and pressure. It uses the proportional valve of the bubble film machine to bypass excess oil and flow back to the tank. During the whole process, the speed of the motor is constant, so the oil supply is also fixed. Because the execution is intermittent, it cannot be fully loaded.
Bubble bag machine manufacturers believe that the bubble film machine has a very important process, which is film blowing. During the film blowing process, the low density polyethylene is in a molten state when extruded from the die and has good transparency. After leaving the die, the expanded region of the bubble should be cooled by a ring of cooling air. When the cooling air blows to the plastic film bubble just extruded from the mold at a certain angle and speed, the high temperature film bubble will contact with the cooling air, the heat of the film bubble will be taken away by the cold air, and its temperature will obviously drop to a low density Polyethylene (LDPE) is below the viscous flow temperature, so that it cools, solidifies, and becomes cloudy.
Bubble bag machine manufacturers believe that on the blown film bubbles, we can see a transparent and fuzzy dividing line, which is the dew point (or frost line). During the film blowing process of the film blowing machine, the dew point has a certain influence on the film performance. If the dew point is high and above the air bubbles after inflation, the inflation of the membrane is in the liquid state. Swelling only thins the film, but the molecules are not stretched and oriented. At this time, the performance of the gas-filled film is close to that of the cast film. Conversely, if the dew point is relatively low, the expansion takes place in the solid state. At this time, the plastic is in a highly elastic state, and the expansion is like transverse stretching, orienting the molecules, so that the performance of the expanded film is close to that of the oriented film. Extruder temperature: When blowing low density polyethylene film, the extrusion temperature is generally controlled between 160-170, and the die temperature must be uniform. When the extrusion temperature is too high, the resin is easily decomposed, the film becomes brittle, and the longitudinal tensile strength is significantly reduced. If the temperature is too low, the plasticity of the resin is poor, and the expansion and stretching cannot be carried out smoothly, the tensile strength of the film is low, the gloss and transparency of the surface are poor, and even patterns similar to wooden circles and unmelted crystal cores (fish eyes) appear.
Bubble bag machine manufacturers believe that the inflation ratio is one of the control points of the blown film production process, which refers to the ratio of the diameter of the inflated bubble to the diameter of the uninflated tube ring. The blow-up ratio is the transverse expansion factor of the film, which is actually the transverse stretching of the film. Stretching will orient the plastic molecules to a certain extent, and the blow-up ratio will increase, thereby improving the transverse strength of the film. However, the inflation ratio should not be too large, otherwise it will easily cause the film bubble to be unstable and the film to warp easily. Therefore, the inflation ratio should be properly matched with the traction ratio. Generally speaking, the expansion ratio of low density polyethylene film should be controlled at 2.5~3.0.
Bubble bag machine manufacturers believe that the traction ratio refers to the ratio of the traction speed of the film to the extrusion speed of the tube ring. The draw ratio is the machine direction draw ratio, which orients the film in the direction of draw. As the draw ratio increases, the longitudinal strength also increases and the thickness of the film becomes thinner. However, if the traction ratio is too large, the thickness of the film will be difficult to control, and the film may even be broken, resulting in film breakage. In general, the stretch ratio of low density polyethylene (LDPE) film should be controlled between 4-6.
