Common quality defects in bottle blowing packaging materials and solutions (II)
6、 The thread of the bottle mouth is damaged
Symptom: The thread of the bottle mouth is damaged or the exhaust slot in the thread area is stretched unnecessarily.
1. Mechanical reasons (the bottle embryo is sent into the mold cavity by the manipulator of the transfer arm. When the manipulator clamps, the two sides of the bottle embryo thread area are stressed. When the manipulator position is inaccurate, the bottle mouth thread will be pinched when the manipulator takes the embryo from the embryo entering guide rail. The bottle taking manipulator will also be pinched).
2. The blowing nozzle is not well aligned with the mold (the blowing nozzle allows the force of the spring to determine the position of the bottle embryo, which is not enough to correct the gap between the two. At the beginning of blowing, there is a considerable impact force, which will cause thread damage).
3. The temperature in the thread area of the bottle mouth is too high (when the temperature in the thread area is too high, the exhaust slot in the thread area is deformed due to the tensile force). This situation is generally caused by the deformation and upwarping of the support ring.
1. Ensure the adjustment of the manipulator of the transfer arm is accurate (synchronous adjustment of the manipulator and the main rotary table, synchronous adjustment of the manipulator and the furnace, and adjustment of the gap between the manipulator and the upper plane of the mold [embryo entry: 1mm, bottle exit: 0.7mm])
2. Use special tools to align the blowing nozzle and mold.
3. Adjust the distance of the cooling plate to protect the thread, or strengthen the ventilation. Reduce the percentage of zone 1, reduce the number of lamps in zone 1, and raise the furnace frame. (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 change of the container itself should be as small as possible. This change is called excessive creep.
Factors: The container shall be at a lower temperature as far as possible during bottle blowing. When the temperature is too high, there is no pearlescent phenomenon on the container, but it needs to be stretched in two directions, so that the container lacks sufficient strength to resist expansion after filling. Bottles made of high temperature are easy to burst after expansion.
Solution: The bottle usually has some visible pearlescence at the end of the bottle blowing. This means that the heating temperature should be set correctly when starting the equipment to avoid overheating or supercooling.
Symptoms: The bottom or near the bottom of the bottle breaks. Some of the cracks are in the transition zone where the bottom of the bottle becomes thinner from thick.
Factors: There are several possibilities.
1. The material fails to reach the limit of its natural stretching during bottle blowing, which will cause the container to change radially (creep) after filling, causing the bottom to crack.
2. The wrinkles generated at the bottom burst during or 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, leading to breakage.
5. The bottom transition zone will be damaged by external force after forming.
6. The alkali concentration of chain lubricant is too high.
Solution: For solutions to the above factors, see the previous section "Bottom damage". Factor 2 is described in the 'Bottom Fold' section below. Observe more when blowing bottles. If the embryo number is fixed, it is related to the quality of bottle embryo.
9、 Flat clamping line (flat bottle)
Symptom: The mold closing line of the bottle in the vertical direction is flat, and the mold tends to separate under the bottle blowing pressure.
1. As the bottle blows from all directions, the applied air pressure will run outward along the vent (vent) of the mold closing line. If the excess gas cannot be discharged in time, the pressure gas will tend to separate the mold closing. (The thin layer material of the broken arm is pushed into the exhaust hole during high-pressure blowing, causing blockage.)
2. The mold compensation air pipe is blocked or leaking, or the mold shell rubber ring is worn and leaking. The compensation pressure is too small.
3. Excessive die clearance
4. The short pin and bushing of the mold closing locating pin are worn.
1. The high-pressure air supply is slower, and the high-pressure bottle blowing time is adjusted to reduce the high-pressure blowing time, but this will reduce the effective cooling time of the mold.
2. Drill several ventilation holes along the mold closing line (aperture: 0.5-0.7mm).
3. Check the size of the compensating air of the test die and whether there is any leakage, and replace it if necessary.
4. Adjust the die closing clearance (the clearance is 0.1-0.2mm). When mold closing is easy, try to reduce the mold closing clearance.
5. Check the wear of the die closing locating short pin and bushing of the die.
10、 Bottom crease (commonly known as' crater ')
Symptoms: The wrinkles are brought to the bottle by the embryo bottom. The wrinkles may be inside or outside the bottle. This kind of bottle is explosive or cracked.
1. External wrinkles:
A: The formation of external wrinkles is usually due to insufficient pre blowing pressure, which pushes excessive material to the bottom during stretching.
B: The temperature at the bottom is too low, so that the material can not be pulled away and pushed to the bottom during stretching.
2. Internal wrinkles are caused by overheating at the bottom of the preform or too late pre blowing after stretching.
1. Adjust the pre blowing pressure to ensure that the pre blowing pressure at each bottle blowing station is good.
2. The temperature at the bottom of the preform should not be too low.
3. The temperature at the bottom of the preform should not be too high.
4. Ensure that the time delay from the beginning of stretching to the pre blowing air inlet is not too long.