Introduction of the components of the film blowing machine

    Blow Membrane is a plastic processing method, which refers to a plastic processing technology in which plastic particles are heated and melted and then blown into a film. Usually, the polymer is extruded to form a tubular film blank, which flows in a better melt flow. In the state, the tube film is blown to the required thickness by high-pressure air, and it becomes a film after being cooled and shaped. The quality of the film material blown by this process is related to the film blowing machine and plastic particles. Film blowing machine is a machine that heats and blows plastic particles into plastic film. The film blowing machine has the advantages of simple structure, low investment, and quick product effect; high mechanical properties of the film; no edge material and less waste; the film product is cylindrical and the bag-making process is simple; it can produce a wide film.

    The structure of a typical blown film machine

1. Introduction of extruder of film blowing machine

    The extruder of the film blowing machine consists of a screw, a barrel, a die, a feeding device, a transmission part, and a heating and cooling system.

Three sections of the screw

    The separation type screw divides the melting section into a solid bed and a melt bed. The width and depth of the solid bed gradually become smaller, and the width and depth of the melt bed gradually become larger, and finally become the width and depth of the metering section.
1. Feed zone.The volume of the screw groove in the feeding section remains unchanged. The material is in a solid state, and the main purpose is to transport the material forward as soon as possible.
2. Melting zone. The volume of the screw groove in the compression section gradually decreases. The material changes from solid to molten. The main purpose of the material is to change from solid to molten.
3. Melt pumping zone.The volume of the screw groove in the metering section remains unchanged. The material is completely in a molten state, and the main purpose is to make the material fully plasticized and send the material to the machine head at a fixed amount and pressure.

The die of extruder of film blowing machine.

    Common blown film machine die heads mainly include the following types.
a. Spiral die head ------ is a relatively common technology at present
b.Laminated die head----can do multi-layer co-extrusion without expanding the die diameter
c. Cone die head----similar to laminated die head
d. Rotating die head-----Improve the problem of winding ribs caused by uneven thickness
e. Non-rotating die
f. Co-extrusion die
g. Single layer die

Spiral die head

Spiral die head, large multi-layer blown film die head with star-shaped pre-splitter

Cone laminated die, used to produce multi-layer barrier composite film die

Automatic die head, there are dozens of heating rods around the die head, it will adjust the heating rod temperature according to the detected film thickness.

The cooling method of plastic film blowing machine can be divided into two types: external cooling and internal cooling.

    1. The external cooling method is the earliest application method. Under the action of the cooling ring, cooling air is released from a circular ring along the extrusion direction and the outer surface of the bubble to generate uniform cooling air around the ring. Inside the cooling ring, the air at the upper port is discharged at a faster average speed than that on the lower port. It is ensured that the shape of the film bubble is consistent with that of the air cooling ring, so that the average flow velocity of the air increases and thus the heat transfer is improved.

     2. The internal cooling directly dissipates heat through the film bubble for cooling purposes. Because the flow rate of the air in the bubble is relatively low and has no regularity, external cooling is more widely used in the market. In the blowing process of the film blowing machine, in order to ensure the quality of the film product, the stability of the film bubble before the film is formed must be considered in order to effectively control the product qualification rate. The output of blown film of the film blowing machine is not only restricted by the film bubble, but also the cooling system of the film blowing machine. A complete cooling system can help the film blowing machine work and run rationally.

Photo of film blowing machine air ring

3. Pulling part of film blowing machine
a. Bubble stabilizer

The bubble stabilizer of the blown film machine is also called the shaping ring. Used to stabilize the bubble, pay attention to the part of the bubble stabilizer that contacts the bubble to be able to rotate flexibly, and there should not be too good thermal conductivity.

b.Herringbone
The bubble is gradually changed from a round shape to a folded shape, ready to enter the traction mechanism.

c. Rotary traction
It has the same function as the rotary die head, dispersing the film with uneven thickness to avoid violent tendons. After adopting rotary traction, the die head no longer rotates. There are two advantages
1. Because there is no rotating mechanism, the machine structure becomes simple, and it is more suitable for multi-layer co-extrusion blown film machine
2. The distortion of the film has been reduced

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   Shanghai Duxia Industry and Trade Co, Ltd. is an enterprise focusing on manufacturing plastic packaging machinery.

The main products of Shanghai Duxia Industry and Trade Co., Ltd . is film blowing machine, stretch film blowing machine,  printing machine, plastic bag making machine, plastic recycling machine.

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