What are the effects on the quality of blow molding products

 The quality of blow-molded products is affected by a variety of processes. In the extrusion blow molding process, there have always been many technical process problems. Yankang Plastic Machinery is willing to share with you how the quality of blow molding products affects the process, the reasons for the problems in these processes and the corresponding solutions, and hope to provide you with relevant suggestions for solving the problems.

      1.  Reasons for uneven vertical wall thickness

      of blow-molded products:
      (1) The self-weight sagging of the parison is serious.
      (2) The two longitudinal cross-sectional diameters of blow molded products are too different

      . Solution:
      (1) Reduce the parison melt temperature, increase the parison extrusion speed, replace the resin with a lower melt flow rate, and adjust the parison control. The device
      (2) appropriately changes the product design and adopts the bottom blowing method.

2.  Reasons for uneven lateral wall thickness
 

      of blow-molded products:
      (1) The parison extrusion is skewed.
      (2) The temperature difference between the inside and outside of the mold sleeve and the mold core is large.
      (3) The shape of the product is asymmetrical.
      (4) The parison inflation ratio is too large.

      Solution:
      (1) Adjust the width deviation of the die gap to make the parison wall thickness uniform; before the mold is closed, the straightening is bad.
      (2) Increase or decrease the heating temperature of the die sleeve to improve the temperature deviation inside and outside the die.
      (3) Before closing the mold, pre-clamp and pre-expand the parison, so that the parison is properly shifted to the thin-walled direction.
      (4) Reduce the parison inflation ratio.

      3.  Reasons for orange peel pattern or pitting on

      the surface of blow molded products:
      (1) Poor exhaust of the mold.
      (2) The mold leaks or the mold cavity condenses.
      (3) The parison is poorly plasticized, and the parison produces melt fracture.
      (4) The inflation speed is slow.
    (5) The inflation ratio is too small.

      Solution:
      (1) Sandblast the mold parison and add vent holes.
     (2) Repair the mold and adjust the cooling temperature of the mold to above the "dew point".
      (3) Reduce the screw speed and increase the heating temperature of the extruder.
      (4) Raise the inflation pressure.
      (5) Clean the compressed air passage and check whether the blowing rod is leaking.
      (6) Replace the mold sleeve and mold core to improve the parison inflation ratio.

      4.  Reasons for the reduction of the volume of blow-molded products

      :
      (1) The wall thickness of the parison increases, resulting in the thickening of the product wall.
      (2) The shrinkage rate of the product increases, resulting in the shrinkage of the product size.
      (3) The inflation air pressure is small, and the product is not inflated to the design size of the cavity.

      Solution:
      (1) Adjust the program control device to reduce the parison wall thickness; increase the parison melt temperature and reduce the parison die-release expansion ratio.
      (2) Replace the resin with small shrinkage rate, prolong the blowing time, and reduce the cooling temperature of the mold.
      (3) Properly raise the pressure of compressed air.

      5.  Reasons for the unclear shape or text of blow molded products

      :
      (1) Poor cavity exhaust
      (2) Low inflation pressure
      (3) Low temperature of parison melt, poor material plasticization
      (4) Low cooling temperature of mold , The mold has "condensation"

      solution:
      (1) Repair the mold, sandblast the cavity or add an exhaust groove
      (2) Increase the inflation pressure
      (3) Properly increase the heating temperature of the extruder and the head, and add if necessary. An appropriate amount of filling masterbatch
      (4) adjust the mold temperature to above the dew point temperature