Film Blowing machine extrusion technology fault diagnosis: Uneven film thickness

  1. Uneven thickness blown film

Almost, the most important requirement for operators is to open thin film products that meet the thickness of uniformity. Many of the design and configuration of the blown film equipment are dedicated to producing films that meet the thickness of uniformity and consistent throughout the production process. The thickness of thickness can lead to the quality of the product, but the downstream equipment is poor and a large number of film waste. Of course, large thickness deviations significantly reduce film profits, because in order to ensure mechanical properties, they have to do a thicker film.

    “Tensile resonance” is manifested as a continuous change in the diameter of the membrane. As with other processing processes, such as sheet extrusion, the tensile resonance is because the melt is too fast, that is, the draft is too large. Solution is to reduce drafting ratio, such as increasing the screw speed.

    “Spiral Membrane” or a serpentine film bubble means that a protrusion has a protrusion from the wind ring as a drafted movement. This situation is that the cream is too low to cool the wind overflow. Improve the cream height, such as increasing the amount of extrusion can solve the problem.

    “Frost oscillating” refers to the phenomenon of film bubbles to reach the maximum positional movement of the maximum diameter. There are several reasons, such as extrudation fluctuations and ambient changes around the membrane, and the gas flow changes. Extrusion fluctuations, as described above, can be stabilized by improving the feeding system and the melting process.

    “Sitting under the membrane” refers to the maximum diameter in a short height range after the film is outlet. This is due to insufficient cooling or other reasons, the cream is too low.

    “Membrane fracture” means the elongation rate of elongation results in the case where the membrane bubble is fractured in the mouthpiece. When the film is traged too fast or when cooling is too fast, the tear phenomenon may occur. A preferred treatment includes increasing the mouth-mold temperature and reduces the drafting ratio.

    “Membrane vibration” is due to the low cream, causing severe turbulence in the wind rings. The solution is to increase the cream height, such as reducing the fan speed.

    “Membrane asthesia” is derived from the periodic increase or decrease in gas volume in the membrane. Mainly due to internal cooling system. Because the membrane bubble internal cooling system continuously exchanges the internal air in the film soil. The solution is to check the various valves, fans and sensors of the internal cooling system.

    In order to treat various instability of membranous bubbles, the company established a mathematical model described in the shape of a blown film. Their most interesting conclusion can be said to be “steady-state multiple”. Briefly introduction, it is a change in process parameters, such as blowing, which can make membrane bubbles from steady state to non-stability, and vice versa. They have done experiments, improved cooling efficiency in the case of instability of membranes. However, as the cooling efficiency increases more than a critical point, the film bubbles enter another unstable state.

    The thickness deviation of the position-dependent refers to the thickness of the film in the lateral layer of different positions. This situation may be caused by the instability of the membrane, but more is from a die of different hearts, uneven cooling, uneven port mold temperature and uneven outlet melt speed. Different heart die refers to a concentric difference between die-outer ring parts forming the surface of the membrane soil and the inner ring parts forming the surface of the membrane bubble. This means that the export gap is uneven, and the melt export is small. During a certain period of time, because the large export resistance has more melt out. Therefore, the final film volume is thicker at a position corresponding to the large opening, and is thinner at a position corresponding to the small opening.

    All die has a tuning device. Before boot debugging, you must adjust the die. However, there is still a fine adjustment during the boot process. A die that completely adjusts concentric can form a completely central symmetrical membrane. This situation will certainly also have other processes, such as cooling air velocity to be uniform around the membrane.

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