6. The screw thread of the bottle mouth is damaged
Symptom:
Damage to the thread of the bottle finish or undue stretch in the vent groove in the thread area.
Factor:
1. Caused by mechanical reasons (the preform is sent into the mold cavity by the transfer arm manipulator. When the manipulator is gripping, the two sides of the preform thread area are under force. When the position of the manipulator is inaccurate, the manipulator will be pinched when it takes the embryo from the embryo guide rail. The thread of the bottle mouth. The bottle taking manipulator will also be pinched.).
2. The nozzle and the mold are not well aligned (the nozzle depends on the force of the spring to determine the position of the preform, and it is not enough to correct the gap between the two. When the blowing starts, there is a considerable impact force, This impact will cause the thread to be damaged.).
3. The temperature of the thread area of the bottle mouth is too high (when the temperature of the thread area is too high, the exhaust groove of the thread area is deformed by the tensile force.) In this case, the support ring is generally deformed and upturned.
Solution:
1. Ensure that the adjustment of the transfer arm manipulator is accurate (synchronous adjustment of the manipulator and the main turntable, synchronous adjustment of the manipulator and the furnace, adjustment of the gap between the manipulator and the upper plane of the mold [embedding: 1mm, bottle output: 0.7mm])
2. Use special tools to align the mouthpiece and mold.
3. Adjust the distance of the cooling plate to protect the thread well, or strengthen the ventilation. Decrease the percentage of one zone, reduce the number of lamps in one zone, and raise the oven rack. (See the thread expansion section for some solutions).
7. The liquid level drops too much after filling
Symptom:
Once the PET container is filled, the container itself should change as little as possible. And this change is called creep excess.
Factor:
Containers should use as low a temperature as possible during the blowing process. When the temperature is too high, there is no pearlescent phenomenon on the container at all, but the maximum bidirectional stretching is required, so that the container lacks sufficient strength to resist expansion after filling. Bottles made at high temperatures tend to burst when expanded.
Solution:
The bottle generally has some visible pearlescence at the end of the blowing. This should set the heating temperature correctly when starting the device to avoid overheating or undercooling.
8. Burst
Symptom:
Cracks at or near the bottom of the bottle, some in the transition from thick to thin at the bottom.
Factor:
There are the following possibilities.
1. The material fails to reach its natural stretch limit during the bottle blowing process, which will cause the container to undergo radial changes (creep) after filling, causing the bottom to crack.
2. The wrinkles generated at the bottom burst during filling or for a period of time after filling.
3. The bottom of the bottle is too thin or too thick.
4. The IV value is low, and the bottle expands after filling, resulting in rupture.
5. The bottom transition area should be damaged by external force after forming.
6. The lye concentration of the chain lubricant is too large.
Solution:
For the solutions to the above factors 1, see the previous 'Break in the bottom' section.
Factor 2 is described in the 'Bottom Wrinkle' section below.
Observe more when blowing the bottle. If it is a fixed embryo number, it is related to the quality of the bottle embryo.
9. Flattening of parting line (flat bottle)
Symptom:
The clamping line of the bottle in the vertical direction is flat, and there is a tendency to separate the mold under the blowing pressure.
Factor:
1. Since the bottle is blown in all directions, the applied air pressure will run out along the ventilation holes (exhaust holes) of the clamping line. When the excess gas cannot be discharged in time, the pressure gas will tend to separate the clamping. (The thin layer of material of the broken arm pushes into the exhaust hole during high pressure blowing, causing blockage.)
2. The mold compensation air pipe is blocked or leaked, or the mold shell rubber ring is worn and leaked. Resulting in the compensation pressure is too small.
3. The mold gap is too large
4. The mold clamping positioning short pins and bushings are worn.
Solution:
1. The high-pressure air supply is slower, and the high-pressure blowing time is adjusted, that is, the high-pressure blowing time is reduced, but this will reduce the effective cooling time of the mold.
2. Drill several ventilation holes (diameter: 0.5-0.7mm) along the parting line.
3. Check the size of the test mold compensation gas and whether there is leakage, and replace it if necessary.
4. Adjust the mold clamping gap (gap: 0.1-0.2mm). In the case of easy mold clamping, try to reduce the mold clamping gap as much as possible.
5. Check the wear of the mold clamping positioning short pins and bushings.
10. Bottom wrinkle (commonly known as 'crater')
Symptom:
The wrinkle is brought to the bottle by the embryo bottom, and the wrinkle may be inside the bottle or outside the bottle. This bottle can explode or burst.
Factor:
1. External wrinkles:
A: The formation of external wrinkles is usually due to insufficient pre-blowing pressure, which pushes too much material to the bottom during stretching.
B: The temperature of the bottom is too low, so that the material cannot be pulled apart during stretching and the material is pushed to the bottom.
2. The internal wrinkle is that the bottom of the preform is overheated or the pre-blowing is too late after the stretching starts.
Solution:
1. Adjust the pre-blowing pressure to ensure that the pre-blowing pressure is good at each blowing station.
2. The temperature at the bottom of the bottle embryo should not be too low.
3. The temperature at the bottom of the bottle embryo should not be too high.
4. Make sure that the delay from the start of stretching to the pre-blowing air intake is not too long.
