Common problems during the bottle stretch blowing process. Part 4
Problem No. 7: Bottom wrinkle, also called by “Vocano mouth”
Symptom: Winkles happens in both internal or external of the bottle bottom. Possibbilities are equal. This kind of bottles are easy to be damaged or exploded .
Causes:
l .External wrinkles. This is often caused by the not enough pre blow pressure. If that pressure is not enough then the PET plastic will be more pushed to the bottom of the bottom during the stretching process.
l .Temperature for the preforms end/bottom is not enough, then the stretching process can not be done perfecty, then the PET plastic will be push to the end/bottom too.
l .Internal wrinkles. The temperature for the preforms bottom parts is too high. Or the pre blow is delayed in the beginning of stretching process.
Solutions:
l . Adjust the pressure for the pre blowing process, to make sure the pressure will be right and correct for each cavity.
l .The temperature for the bottom parts can not be too high or too low. You must get the correct temperature.
l .Make sure you get the correct blowing time is right between stretching and blowing.
Problem No. 8: Internal neck wrinkles, also callsed by “internal rings”
Symptom: It happens often around 5-8mm place below the neck ring part. And a clear and outstanding ring can be seen and felt.
Causes:
l . It is about the week part below the ring part. If that part is too thin, then it will get cold faster and other part during the stretching process. (the stetching stick is going down normally). When it get cold too fast, it get wrinkles.
Solutions:
l .Adjust the hearing light location if it is possible. To make it a little bit far away from the thin part on the preform.
l .Adjust the air inlet time for pre-blowing. It can not be too late, must be in right time.
l .Check if the solenoid for pre-blowing is working well.
l .Reduce the temperature for the thin part on the preform.
l .Increase the temperature for the thicker part on the preform. Just to make the stretching for the both part will be right, and they can get to the same step. Something like giving the poor more and the richer less. That means, we will need to find the balance point for for heating temperature.
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