Elimination of quality defects of PET bottles form

2022-08-16
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Methods for eliminating quality defects of PET bottles formed by two-step method

note: the pet embryo referred to here is formed by reciprocating screw injection device and hot runner mold

internal quality defects of mold embryo and their elimination methods

the quality of mold embryo is finally reflected in blow molded products, such as stretch blow molding. Although effective measures are taken, it still fails to meet the quality requirements of bottles, which indicates that there are defects in the internal quality of mold embryo. In order to improve the internal quality of the embryo, the following points should be noted:

1) the material must be dry enough with a water content of less than 0.005%

2) keep the injection speed and plasticizing speed as low as possible. The plasticizing speed is r/min, and the screw linear speed is 8m-15m/min

3) keep the plasticizing back pressure as low as possible, and the back pressure is 0 Mba。

4) the downtime of resin in the barrel, hot runner body and hot runner injection nozzle shall be as short as possible. 5) The temperature of hot runner body, hot runner nozzle and barrel shall be as low as possible

6) the drying temperature of the material shall be as low as possible

7) the mold is cooled evenly

8) the holding pressure should not be too high and the holding time should not be too long

third, stretch blow molding PRT bottle is the last link of forming PET bottle, which is directly related to the quality of PET bottle. Therefore, for the equipment related to stretch blow molding PET bottle, the process must be strictly controlled before stretch blow molding can produce high-quality pet bottle

* manual semi-automatic blow molding PET bottle equipment

* semi-automatic infrared rotary heater

main function: using the infrared characteristics, evenly heat the mold embryo to the blow molding temperature

the heater is mainly composed of an infrared lamp heating device with adjustable temperature, a central revolution mechanism driven by a motor driven sprocket chain driven by a frequency converter, a speed regulating rotation mechanism installed on the male chain and inserted into the parison, a control cabinet, etc. It is used in the production cycle of the latest engine ge9x: manually insert the parison, and the parison revolves and rotates. Under the infrared radiation, it is heated evenly, and the mold embryo reaching the blow molding temperature is taken out manually. * stretch blow molding machine

main function: stretch the mold embryo that reaches the blow molding temperature axially, and then blow molding with high-pressure air

the stretch blow molding machine is mainly composed of: pneumatic mechanical mold closing mechanism, pneumatic system, stretch blow molding device, mold, control system, etc

work cycle: manually put the parison reaching the blow molding temperature into the single (double) side mold cavity, and the mold embryo is self positioned by its own bottle mouth thread, and then close the mold and press the mold. The sealing cylinder works, seals the bottle mouth, and the stretching cylinder works. The end of the stretching rod presses against the bottom of the parison for axial stretching to the bottom of the mold cavity, and high-pressure air is blown into the parison cavity to form. After a certain time of pressure maintaining and cooling, the stretching rod returns, the sealing cylinder piston returns, the mold is opened, and the product (PET molding bottle) is taken out

defect elimination method of stretch blow molding PET bottle quality (see the table below)

defect and elimination method Manual of stretch blow molding PET bottle quality defect reason elimination method can't blow the mold embryo with low temperature, low blowing pressure, extend the heating time (that is, reduce the revolving speed of the heater), and increase the heating temperature. Check the blowing pressure. The blowing pressure should be 105mpa-2. The non-woven tensile testing machine also uses this material for testing When the 5MPa stretching rod end is stretched, the bottom of the parison should be punctured to avoid just scraping the plastic mortar with a certain plasticity. The temperature of other parts at the bottom of the parison is low and the temperature at the bottom of the parison is high. The parison material is poor. Adjust the heating temperature of each section heated by the heater to increase the heating temperature of other parts at the bottom of the parison. The elimination method is the same as above, and the temperature at the bottom of the parison is reduced. Use the parison with high quality of parison material

some or all of the products are whitened, the billet temperature is low, the billet quality is poor, the heating time is prolonged (that is, the revolving speed of the heater is reduced), and the heating temperature is increased. Select high-quality parison

poor product transparency. The parison temperature is too high, and the internal quality of the cavity is substandard. Shorten the parison heating time, that is, increase the revolving speed of the heater and reduce the parison heating temperature. Note: parison stretch blow molding when asked if the airliner is likely to be hijacked or thawed in the air, the parison that meets the quality standard shall be selected

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