PET plastic has the characteristics of light weight, high transparency, impact resistance and not easy to break. PET bottles are mainly used in the packaging of cosmetics, medicine, health care, beverages, mineral water, reagents and other packaging. PET bottle quality depends on the quality of the preform quality.
How to solve the PET Preform quality problems in the production? Here are some solutions for your reference. Hope can help you.
| Problems | Reason | Solutions |
| preform bottom is white | 1. hot runner temperature is not enough 2. material temperature is not enough | 1. enhance insulating steps 2. increase thermal couple temperature 3. increase little material temperature 4. increase injection speed 5. decrease pressure maintaining 6. slower cooling water flow rate |
| preform non-transparent | 1. insufficient drying of raw material 2. insufficient plastising of raw material 3. preform wall thicker or undercooling 4. mixed with other material 5. material temperature is too low | 1. drying lasts for 4 hours or above it 2. increase the material temperature 3. increase the screw speed 4. water content lower 0.02% under the 165 degree 5. enhance cooling |
| preform changes from transparent to non-transparent | 1. de-moulding temperature is too high | 1. enhance cooling water 2. extend cooling time 3. change injection time |
| fog in preform one side | 1. pressure too high 2. sprue off centre | 1. decrease pressure 2. modify mould |
| preform with crazing or yellowing | 1. plastic decomposition | 1. decrease drying temperature, extend drying time 2. adjust injection speed 3. lower material temperature 4. lower thermal couple temperature |
| preform with bubbles | 1. insufficient drying | 1. enhance drying 2. increase material temperature 3. decrease screw speed |
| Preform with irregular ring slot | 1. water vapour condensates in cavity and core | 1. enhance factory drying 2. increase cooling temperature 3. wipe dry mould |
| Sprue part cracks | 1. hot runner mouth and sprue are not in centre 2. sprue upside down 3. sprue is too hot | 1. modify mould 2. modify sprue 3. extend cooling time 4. increase injection speed or time 5. enhance sprue insulating |
| Neck not full or with welding traces | 1. exhasut bad 2. injection not in centre | 1. enlarge exhausting hole 2. clean die lip 3. decrease injection speed 4. modify sprue hole |
| preform wall thinkness is not evenly | 1. low quality of preform mould 2. spure hole is not in position 3. injection pressure too high 4. core position changes | 1. modify mould 2. increase material temperature 3. decrease pressure 4. use high precision and core adjustable mould |
| preform surface sinking | 1. material temperature too high 2. injection speed too short 3. pressure maintaining too short 4. injection time too short 5. insufficient cooling | 1. decrease material temperature 2. decrease injection speed 3. increase pressure maintaining 4. increase injection time 5. increase water pressure |
| preform sprue satin | 1. poor insulating 2. insufficient cooling 3. poor screw non-return 4. pressure maintaining too low | 1. guarantee sprue part insulating 2. enlarge cooling 3. clean screw nozzle 4. increase pressure maintaining |
| preform bends after de-moulding | 1. sprue not in centre 2. cooling unevenly | 1. modify mould 2. decrease pressure maintaining 3. increase injection speed 4. extend cooling 5. clean water tunnel 6. increase cooling warer pressure and yield |
| preform bends after increasing temperature | 1. preform not in centre 2. different density | 1. modify mould 2. decrease temperature, especially the bending parts |
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