Views: 0 Author: Site Editor Publish Time: 2022-04-19 Origin: Site
What are the important factors that affect the PET bottle blow molding process through blow mold design?
PET blowing bottles can be divided into two categories, one is pressure bottles, such as bottles for carbonated beverages; the other is non-pressure bottles, such as bottles for water, tea, edible oil, etc. What are the important factors that affect the PET bottle blow molding process through blow mold design?
When PET bottle blowing manufacturers prepare PET blowing, they first inject PET chips into the preform. It is required that the proportion of secondary recycled materials should not be too high (less than 5%), the number of recycling should not exceed twice, and the molecular weight and viscosity should not be too low (molecular weight 31000-50000, intrinsic viscosity 0.78-0.85cm3/g).
According to the National Food Safety Law, secondary recycled materials shall not be used for food and drug packaging. Injection preforms should be stored for more than 24 hours before they can be used. Unused preforms can be stored for more than 48 hours before reheating. The storage time of preforms should not exceed 6 months.
The quality of the preform largely depends on the quality of the PET material. PET bottle blowing machine manufacturers should choose materials that are easy to inflate and form, and formulate a reasonable preform forming process. Experiments in PET blow molding plants show that imported raw materials are easier to blow out of PET preforms with the same viscosity than domestic raw materials. However, the production date of the same batch of preforms is different, and the blow molding process may be quite different. The quality of the preform determines the difficulty of the blow molding process. The requirements for the preform are pure, transparent, free of impurities, no color, suitable length of the injection point and a halo around it.
The heating of the preform is completed by the heating furnace, the temperature of which is manually set and automatically adjusted. In the oven, the far-infrared tube emits far-infrared radiation to heat the preform, and a fan at the bottom of the oven circulates the heat to make the temperature inside the oven even. The preforms are rotated while advancing in the oven so that the walls of the preforms are heated evenly.
The arrangement of tubes in the oven is generally "ribbon", from top to bottom, with more at both ends and less in the middle. PET bottle blowing manufacturers suggest that the heat of the oven should be controlled by the number of lamps, the overall temperature setting, the power of the oven, and the heating ratio of each section, and the opening of the lamps should be adjusted in conjunction with pre-blowing. In order for the oven to work better, it is very important for the PET blow molding machine manufacturer to adjust its height and cooling plate. Improper adjustment can easily lead to defects such as swelling of the bottle mouth (the bottle mouth becomes larger), stiffness of the head and neck (the neck material cannot be pulled open) and other defects.
Pre-blowing is a very important step in the two-step blowing method, that is, during the blowing process, the pre-blowing starts when the stretch rod is lowered, so that the preform is formed. In this process, pre-blowing position, pre-blowing pressure and blowing flow rate are three important process factors.
The shape of the pre-blown bottle determines the difficulty of the blow molding process and the performance of the bottle. The normal shape of the pre-blown bottle is a spindle shape, and the abnormal shape is a bell shape and a handle shape. Reasons for abnormal shape include improper local heating, insufficient pre-blowing pressure or blowing flow.
The size of the pre-blow bottle depends on the pre-blow pressure and pre-blow position. In production, the PET blower should maintain the size and shape of all pre-blown bottles throughout the facility. If there is a difference, find out why. Or the heating pre-blowing process can be adjusted according to the pre-blowing situation.