PET Preform Blowing Machine Trouble Shooting

Fault 1: Poor transparency 

Reasons:

1. Heating temperature is too high

2. Heating time is too long

3. Compressed air contains moisture

4. Preform with poor transparency

5. preform design problem

6. The inflation ratio is too small

Methods:

1. Cool down

2. Shorten the heating time

3. Use a dryer to remove water

4. Improve preform quality. Select dry raw materials

5. Improve preform size design

6. Reduce preform diameter

Fault 2: Pearly whitening appears in PET bottles

Reasons:

1. The heating temperature is too low

2. Preform wall thickness is uneven

3. Preform wall is too thick.  Insufficient heating.

Methods:

1. Warm up or slow down the revolution speed

2. Improve preform quality

3. Reduce the preform thickness

Fault 3: Bottom center offset

Reasons:

1. Start blowing too early

2. The stretch rod did not go down to the bottom

3. Stretching rod and bottle shaft center are not in the same line

4. Uneven wall thickness of preform or uneven injection density

5. Uneven heating

Methods:

1. Delay the blowing time/ increase the descending speed of the stretching rod

2. Adjust the position of the magnetic switch

3. Adjust the position of the stretching rod

4. Improve preform quality

5. Improve heating conditions/check if there is any problem with preform rotation

Fault 4: Uneven wall thickness of PET bottles

Reasons:

1. The position of the stretching rod is not in the preform center

2. The blowing holes are asymmetrical and have different apertures

3. The stretching ratio is too low /the inflation ratio is too small

4. The preform does not rotate in heater

5. Uneven wall thickness of preform/uneven injection density

Methods:

1. Adjust the position of the stretch rod

2. Adjust the position and diameter of the blowing hole

3. Increase the stretching ratio/inflation ratio

4. Check the rotation device

5. Improve preform quality

Fault 5: The upper part of the bottle is too thick

Reason:

1. The upper temperature is too low

2. The position of the mold exhaust hole is too far from the upper part

3. The stretching ratio is too low

4. The upper part inflation ratio is too low

5. The speed of the stretching rod is too slow

Methods:

1. Upper heating

2. Adjust the position of the exhaust hole

3. Increase the stretching ratio

4. Change bottle shape

5. Adjust stretch rod speed

Fault 6: The bottle bottom is too thin

Reasons:

1. Start blowing too early

2. The bottom temperature is too high

3. The preform bottom is too thin

Methods:

1. Delay the start of the blowing time

2. Lower the bottom temperature

3. Increase preform bottom thickness

Fault 7: The bottle moulding line is obvious

Reasons:

1. The clamping pressure is not enough

2. The sealing time is too early

3. Mold problem

4. The preform neck size does not match with the mold

Methods:

1. Increase the clamping pressure and adjust the angle of the clamping struts (<5 degrees)

2. Move back the position of the mold clamping travel switch

3. Repair the mold or check the assembly position of the mold, such as whether the guide pillar is loose, or whether the mold is not pressed tightly

4. Revise the mould neck