The working principle of Pp film blowing machine can be summarized as the following steps:
First, raw material preparation and melting
Raw material addition: First, polypropylene (PP) pellet raw material is added to the hopper of the extruder. These particles are the basic material for the production of thin films.
Melt plasticization: In the extruder, the polypropylene particles gradually melt under the action of high temperature and shear force of the screw, and plasticize into a molten plastic melt. This process requires strict control of temperature and screw speed to ensure the quality and uniformity of the melt.
Second, extrusion molding
Melt extrusion: The molten plastic melt is pushed by the screw and is extruded through the die part of the extruder. There is a precise flow channel design inside the die head, which can make the melt evenly distributed and form a tubular film blank.
Preliminary forming: After the melt is extruded from the die head, a continuous tubular film blank is formed. At this time, the temperature of the film billet is high, it is in a molten state, and further processing is required to form a stable film.
Three, blow and stretch
Blowing device: the film blank enters the blowing device immediately after extrusion. By blowing compressed air into the blowing device, the film billet is rapidly expanded and stretched in the circumferential direction to form a bubble tubular film. This step is key to forming the shape and size of the film.
Stretch ratio control: During the blow and stretch process, the stretch ratio (that is, the diameter ratio before and after the expansion of the film) needs to be controlled to obtain the desired film thickness and performance. The tensile ratio will affect the mechanical and optical properties of the film.
4. Cooling and shaping
Cooling device: After blowing and stretching the bubble tube film into the cooling device. The cooling device is usually cooled by cold air or cold water, so that the film is quickly cooled and shaped. This step ensures that the film maintains a stable shape and size during subsequent processing.
Temperature control: Temperature control is very important during the cooling process. If the cooling speed is too fast, the internal stress of the film may be too large and rupture; If the cooling rate is too slow, the film may not be fully set.
Five, traction winding
Traction device: The cooled and shaped film is pulled out through the traction device. A traction device usually consists of one or more pairs of traction rollers that rotate and clamp the film at a constant speed, allowing it to maintain a steady tension and speed.
Winding device: After the film is pulled out through the guide roller and the press roller, the winding device is wound into a roll. The winding device can automatically adjust the winding speed and tension to ensure the flatness and tightness of the film.
6. Post-processing
Trimming and trimming: As needed, the wound film can be trimmed and trimmed to remove irregular edges and impurities.
Quality inspection: Finally, the quality inspection of the finished film, including checking whether its thickness, width, strength, transparency and other performance indicators meet the requirements.
