Common problems during the bottle stretch blowing process. Part 1

Problem No. 1 : The bottle bottom shaping is not complete

Symptom: bottom shaping is not complete & full. There are indentations on the petal-like bottle bottom. This kind of bottle is no problem for filling, but it will not be stable when is is standing on the conveyor and been transported to the filling machine.

Causes:

l The pressure from the high pressure part is not enough.

l Temperature for the bottom part is not high enough.

l Pre-blow (high pressure) time is too short.

l Pre-blow (high pressure) air inlet time is too late.

l Bottom air vent hole is not smooth.

Solutions:

l Check the inlet air pressure of the high pressure end, it should be at least 28bar or higher.

l Check if the air filter is smooth.

l Check all air valves, they should be all smooth and not-stocked.

l The air inlet time of the pre-blow (high pressure) should be in time, can not be too late. If not, the high pressure blow time will be too short and the cooling time inside the mold will not be enough.

l Make sure the bottom air vent hole is not stocked.

l Increase a little temperature for the bottle bottom part inside the heating oven.

l Reduce the temperature of the thinner part on the preforms.

Problem No. 2 : The bottle neck (screw) expanding

Symptom: The bottle neck/screw expanding. Especially when the outside air temperature is hot. It happens when the temperature for the neck part inside the heating oven is too high. The explosive sound of the high pressure air leaking can be heard during the blowing process.

Causes:

l The cooling water temperature is too high.

l The cooling water flow quantity is not enough.

l Cooling plate is not in good position.

l Air evacuation inside the heating oven is not good.

l The temperature close to the neck part inside the heating oven is too high.

Solutions:

l Check the temperature and flow quantity of the cooling water.  

l Adjust the cooling plate’s position, and make sure it protect the neck part.

l Increase the air evacuation inside the heating oven.

l Reduce the temperature of the heating lamp which is close to the neck part inside the heating oven.