Preforms are used widely to manufacture PET bottles and containers. These containers offer an affordable solution to manufacturers in the packaging industry to offer a high-quality source of packaging solutions to pack medicines, syrups, food items, beverages, chemicals, and many more. As the Preforms are manufactured to fulfill the requirement of packaging in various production houses, it is the duty of the perform manufacturers to test the quality of the preforms thoroughly. There are many defects that are encountered at the time of production and quality assurance process that need to be rectified efficiently to enhance the quality of production and to satisfy the demands and requirements of the customers in the best possible way.
The Defect generally occurs in the axis of the moulds of the preform which created a dim area of the feet that are opposite to the offset. The Gate runner offset leads to crack the thinnest area of the bottom of the Preforms. This defect in the axis of the molds usually occurs when the eccentricity of the Preform is too big or when one part of the Preform poorly cooled. The defect of gate runner offset also occurs when the air at the time of blow molding stretches the perform quicker than the rod or there is early or too high blowing pressure or there may be two big distance between the stretching rod and the moulds.
Solution to Rectify the Defect of Gate Runner Offset
To cure the defect of the Gate Runner Offset – diminish the percentage of heating and check the presence of different crystallinity in the preform, also check the bending structure of the perform appropriately and measure the efficiency of mould cooling circuit. To ensure the quality of the preform also adjust the gap between the bottom of the bottle and the rod. To produce high-quality of performs, decrease the pressure of air during pre-blowing or delay the process of pre-blowing, also measure the alignment of the preform with the help of “Preform Eccentricity Tester”.
The fold which is formed either on the shoulders or under the neck of the Preforms is considered as the compressed neck of the Preform. This defect in the Preforms are occurred when it is overstretched lengthwise before initiating the pre-blowing process, due to delay in the pre-blowing, too low pressure or low pressure, if the diameter of the Preform from the inner side decreases due to the effect of stretching rod or when the rod touches the wall of the Preform, the material quickly cools down and result in forming the ring in that place.
Solution to Rectify the Defect of Compressed Neck
If the defect of compression is observed in various section of the Preform, start the pre-blown in early stages and enhance the pressure of blowing, also enhance the total percentage of heating to strengthen the temperature of the preform body completely. If the defect is still left in one section of the Preform, carefully measure the supply of the pre-blown air and interchange the valves of the station when necessary.
Ring on the body is the defect which is similar to the defect of the compressed neck to some extent, but it is located on the body of the Preform. The defect appears as a bulge or ring and in worst situations; the diameter of the bottle diminishes where the rod touches the wall. This defect is caused due to the low pressure at the time of pre-blowing or no-pressure. The ring on the body of the Preform also occurs due to the insufficient supply of heating in the body of the defect.
If the defect appears on one part of the station, enhance the flow rate of the blowing and check the valve of blowing. On the other hand, if the imperfection occurs on all the section of the bottle, enhance the blowing pressure or enhance the heating in the cold areas.
Apart from these defect, other defects like neck curvature, the excessive material in the shoulder area, volume loss during filling, over-weighted bottom, etc. To know more about the Preform Defects Testing Measures, continue reading.
For more information check – Polariscope Strain Viewer