At present, most bottle blow molding machine are still […]
At present, most bottle blow molding machine are still two-step blow molding machines, that is, the plastic raw materials must be made into preforms and then blown. Now commonly used is PET material of environmentally friendly plastic. Collectively referred to as PET bottle blowing machine. Bottle blowing machine blowing process is divided into two parts. The preform (embryo) by infrared high-temperature lamp irradiation, the preform (embryo) bad (embryo) body heating softening, in order to maintain the shape of the bottle, preform (embryo) mouth is not heated, and therefore need a certain The cooling device to its cooling operation. Blow molding is to preheat the preform has been good preform (blow mold) is placed in blow mold has been done, its high-pressure inflatable. The preform (embryo) blowing into the desired bottle. Automatic bottle blowing machine by manipulator operation will be blowing the two operations together to complete, eliminating the need for manual pre-heating the preform into the blowing process. Greatly speed up the production rate.
Blow molding machine blow molding process is a two-way stretch process, in the process, PET chain was bidirectional extension, orientation and arrangement, thereby increasing the mechanical properties of the bottle wall, improve the tensile, tensile, impact strength, And has a very good air tightness. Although stretching helps to increase the strength, it can not be over-stretched. To control the stretch-blow ratio, do not exceed 3.5 to 4.2 in the radial direction and 2.8 to 3.1 in the axial direction. Preform wall thickness not more than 4.5mm.
Bottle blowing is carried out between the glass transition temperature and the crystallization temperature, the general control at 90 ~ 120 degrees. In this interval, PET showed high elasticity, rapid blow molding, and became a transparent bottle after cooling and setting. In a one-step process, the temperature is determined by the length of cooling in the injection molding process, so there is a good relationship between injection and blow. Blow molding process are: stretch - a blow - the second blow, the three moves in a very short time, but must be good, especially the first two steps determine the overall distribution of the material, blowing the bottle of good or bad quality. Therefore, to be adjusted: stretching start timing, stretching speed, pre-blowing start and end timing, pre-blowing pressure, pre-blowing flow, etc., if possible, can control the overall preform temperature distribution, preform Outer wall temperature gradient.
In the rapid blow molding, cooling process, the bottle wall induced stress. For inflatable bottles, it is good for resistance to internal pressure, but for hot filling bottles, it must be guaranteed that it is fully released above the glass transition temperature.
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