Plastic Bottle Manufacturing Process
2. Production conditions (process parameters) 2.1. Bottle Injection Blow Molding 2.1.1. Injection Blowing Equipment: SZC Plastic Injection Blowing Hollow Molding Machine 2.1.2. Injection and blowing process conditions 184.108.40.206. Heating temperature: 185~245°C 220.127.116.11. Heating time: 30 minutes 18.104.22.168. Blowing pressure: 0.9~1.25MPa 22.214.171.124. Pre-molding time: 1~3 S 126.96.36.199. mold closing time: 1~2 S 188.8.131.52. Blowing time: 1~2 S 184.108.40.206. Holding time: 2~4 S 220.127.116.11. Cooling time: 1~2 S 2.2. Bottle cap injection molding 2.2.1. Injection Molding Equipment: FT-1307 Plastic Injection Molding Machine Process conditions 18.104.22.168. Temperature of Injection Molding Sections Barrel temperature: 180-240°C 22.214.171.124. Pre-plastic pressure: 6.0~7.5MPa 126.96.36.199. Injection pressure: 4~6MPa 188.8.131.52. Holding time: 1~2 S 184.108.40.206. Injection time: 2 ~ 4 s.
220.127.116.11. Cooling time: 2~4 S 3. Operating Steps 3.1. Bottle Making Operation Steps 3.1.1 batch: accurately weigh the raw materials according to the formula, add the weighed high density polyethylene and polyethylene color masterbatch into the mixer in turn, and complete the mixing within a certain time.
3.1.2. Feeding and plasticizing: The prepared materials are added into the hopper of the injection and blowing machine, and plasticizing is completed through multi-stage heating, screw rotation, conveying and stirring.
3.1.3. Injection: molten plasticized material is injected into the aggregate pipe through a large nozzle, and then injected into the core rod in the injection model through a small nozzle of the aggregate branch pipe to form a parison, and the parison surface is solidified through moderate cooling, so that the bottleneck has been formed.
3.1.4. Blow molding: Open the press, lift the central tower and the connected core rod. The core rod holds the parison and transfers it to the blow molding die, and then close the blow molding die. Clean compressed air is introduced from the core rod to blow up the parison and close to the inner wall of the blow molding cavity, and the parison is temporarily cooled and shaped into a plastic bottle.
3.1.5. Bottle removal: After blowing is finished, the tower is lifted, and the tower and the connected mandrel hold the bottle and transfer it to the bottle removal station. A group of corresponding bottle removal boards are used to clamp the bottle neck and separate the bottle from the mandrel and transfer it to the conveyor belt.
3.1.6. Packaging: Plastic bottles that pass visual inspection on the conveyor belt, after being properly cooled, pass through the automatic counter one by one, and fall into clean, dry, pollution-free, plastic bags with specified thickness and sufficient strength for packaging. The plastic bag is put into the certificate of approval, tied at the mouth, and then sent out to the clean workshop through the material channel. The outer package of the woven bag is clean, dry, free from pollution and woven with certain strength.
3.2. Operation Steps of Cover Making 3.2.1. Matching materials: The processing requirements and process of raw and auxiliary materials for plastic bottle caps are consistent with the bottle body.
3.2.2. Feeding and plasticizing: The prepared materials are added to the hopper at the top of the injection molding machine. After the machine is started, the materials in the hopper will continuously enter the barrel along with the screw in the barrel of the plasticizing machine. The plastic batch entering the barrel will reach a flowing state when heated in the barrel and has good plasticity. The requirement is that the plastic should reach the specified molding temperature before entering the mold cavity and provide a sufficient amount of molten plastic (plasticizing amount) within the specified time. The temperature at each point of the melt should be uniform and consistent without thermal decomposition to ensure the physical properties of the plastic cover and the need for continuous production.
3.2.3. Injection: firstly, the plasticized melt is injected into the die under the push of the screw. The process requires sufficient injection pressure to ensure the die is complete. Then it enters the molding stage and goes through four steps of stamping die, compaction, backflow and gate solidification. Then the plastic melt in the mold cavity is cooled and shaped into a plastic cover.
3.2.4. Cooling and demoulding Packaging 4. Main Physical and Chemical Properties of Polyethylene Polyethylene resin is nontoxic, colorless, odorless and tasteless. It has good chemical stability and is not affected by strong acid, strong alkali and most solvents. It has good cold resistance, wear resistance and moisture resistance, but poor taste resistance and oil resistance. High density polyethylene has slightly better oil resistance and other properties.
5. Main Defects and Solutions 5.1 Bottle Size Exceeds Tolerance 5.1.1 Main Causes of Defects 18.104.22.168. Plastic raw materials have moisture, causing shrinkage to increase.
22.214.171.124. Molding process conditions have changed.
126.96.36.199. Error between measured temperature and actual temperature.
Resolution When the bottle body is out of tolerance, the plastic raw materials shall be dried, and the drying temperature and drying time shall be determined through experiments. The injection pressure shall be increased and the holding time shall be prolonged for the values of molding process parameters. Appropriate extension of cooling time is beneficial to obtain smaller shrinkage rate of the bottle body, eliminate deformation during storage at room temperature, and improve dimensional accuracy of various parts of the bottle body, thus ensuring that the size of the bottle body conforms to regulations.
5.2. Impurities on the surface of the bottle body 5.2.1 Main Causes of Defects 188.8.131.52. Melt temperature is too high, raw materials decompose due to overheating.
184.108.40.206. The plastic at the nozzle is mixed into the mold.
220.127.116.11. Foreign matter mixed in raw material mixing process.
18.104.22.168. Raw material itself is not clean or has foreign matter.
Resolution Reasonable barrel temperature is selected to form a certain temperature gradient to avoid decomposition of materials due to excessive temperature. Clean the nozzle frequently, strengthen the quality control of mixing process, and strengthen the inspection of raw and auxiliary materials to ensure the appearance quality of the bottle.
5.3. Fringe and Impression 5.3.1. Main Causes of Defects 22.214.171.124. Injection pressure is too high.
126.96.36.199. The mold clamping force is insufficient.
188.8.131.52. Mold has impurities.
Resolution It is mainly to control the injection pressure, melt temperature, mold temperature and nozzle temperature.
5.4. Insufficient injection quantity of parison 5.4.1. Main Causes of Defects 184.108.40.206. Improper selection of molding process conditions (insufficient injection pressure).
220.127.116.11. Insufficient plasticizing capacity.
18.104.22.168. Plastic has poor fluidity.
Resolution The temperature of melt and mold can be appropriately increased, the injection pressure can be increased, and the injection time can be prolonged. In the process of mixing raw materials, the mixing uniformity of plastic particles and compounding agents should be improved to ensure good fluidity of the materials.
5.5. Plastic bottle shoulder deformation 5.5.1. Main Causes of Defects 22.214.171.124. Blow molding pressure is not enough.
126.96.36.199. Blow mold has poor exhaust.
188.8.131.52. The parison mold temperature is not enough.
184.108.40.206. Improper demoulding operation.
Resolution Raise the air pressure and prolong the working time, clean up the exhaust slot, raise the parison mold temperature, and operate strictly according to the mold standard operation method.