The important factors affecting the pet food bottle blow molding process----Preliminary blowing
The important factors affecting the pet food bottle blow molding process----Preliminary blowing
Preblowing is a very important step in the two-step bottle blowing method. It means that the preblowing begins when the stretching rod drops during the blowing process, so that the bottle preforms.In this process, preblowing position, preblowing pressure and blowing flow rate are three important technological factors.The shape of the preblown bottle determines the difficulty of blow molding and the performance of the bottle.
The normal pre-blown bottle is spindle-shaped, while the abnormal ones are subbell-shaped and handle shaped.The abnormal shape is caused by improper local heating, insufficient preblowing pressure or air flow, etc. The size of preblowing bottle depends on preblowing pressure and preblowing position.
In production, the size and shape of all pre-blown bottles of the whole equipment should be maintained consistent. If there is any difference, specific reasons should be found. Heating or pre-blown technology can be adjusted according to the pre-blown bottles.The size of preblowing pressure varies with bottle size and equipment capacity. The general capacity is large and the preblowing pressure is small.High production capacity, high pre - blowing pressure.Even if the same equipment is used to produce bottles of the same specification, the preblowing pressure required by PET materials is not the same due to the differences in the properties of PET materials.
Glass fiber reinforced PET material, small preblowing pressure can make the large molecules at the bottom of the bottle correct orientation;For other bottle preforms with improper materials or forming process, there is a large amount of stress concentration near the injection point and it is not easy to fade away. If blow molding is used, it will often burst at the injection point or burst and leak from the injection point in the stress test.According to the orientation condition, the lamp tube can be moved out of 2-3 tubes to open above the injection point as shown, and the injection point can be fully heated to provide enough heat to prompt its rapid orientation.
For the preforms that have been heated for a second time or that have been stored for longer than normal, due to the time-temperature differential effect, their forming processes are similar, requiring less heat than the normal preforms, and the preblowing pressure can be appropriately reduced.
