Analysis of the top ten problems in the blow molding process

1. The lateral wall thickness of the blow molded product is uneven:

cause:

1 parison extrusion skew 2 mold sleeve and the core inner and outer temperature difference is larger 3 product shape asymmetry 4 parison blow ratio is too large.

Solution:

1Adjust the deviation of the gap width of the die to make the wall thickness of the parison uniform; before closing the mold, straighten the type 2 to raise or lower the heating temperature of the mold sleeve, and improve the temperature deviation inside and outside the mold. 3 Pre-clip the parison before closing the mold. Tightening and pre-expansion, the parison is appropriately offset 4 in the thin-wall direction to reduce the parison blow ratio.

Second, the longitudinal wall thickness of the blow molded product is uneven:

cause:

1 parison sag is serious. 2 The longitudinal cross-sectional diameter of the blow molded product is too different.

Solution:

1 Lowering the melt temperature of the parison, increasing the extrusion speed of the parison, replacing the resin with a lower melt flow rate, adjusting the parison control device 2 to appropriately change the product design, and molding by the bottom blowing method.

Third, the appearance of blow molding products appears orange peel pattern or pitting:

cause:

1 mold exhaust failure 2 mold leakage or mold cavity condensation phenomenon 3 parison plastic poor, parison melt fracture phenomenon 4 inflation pressure is less than 5 inflation speed is slow 6 blow expansion ratio is too small.

Solution:

1 mold parison is sandblasted, additional vent hole 2 is used to repair the mold, and the mold cooling temperature is adjusted to above the "dew point". 3 Reduce the screw speed, increase the heating temperature of the extruder 4, increase the inflation pressure, and clean the compressed air passage. Check whether the blower is leaking. 6 Replace the mold sleeve and core, and increase the blow ratio of the parison.

Fourth, the volume of blow molding products is reduced:

cause:

1 The wall thickness of the parison increases, which leads to the thickening of the product wall. 2 The shrinkage rate of the product increases, resulting in a shrinkage of the product size and a small inflation pressure, and the product is not inflated to the cavity design size.

Solution:

1 Adjust the program control device to reduce the wall thickness of the parison; increase the parison melt temperature, reduce the parison expansion ratio 2, replace the resin with small shrinkage ratio, prolong the blowing time, reduce the mold cooling temperature, and properly reduce the compression. The pressure of the air.

5. The outline or graphic of the blow molded product is not clear:

cause:

1 cavity exhaust failure 2 inflation pressure is low 3 parison melt temperature is low, material plasticization is poor 4 mold cooling temperature is low, the mold has "condensation" phenomenon.

Solution:

1 Repair the mold, cavity blasting or add venting groove 2 to increase the inflation pressure 3 to properly increase the heating temperature of the extruder and the head, if necessary, add an appropriate amount of filler masterbatch 4 to adjust the mold temperature above the dew point temperature.

6. Blowing products are too much and too thick:

cause:

1 mold expansion mold, the clamping pressure is less than 2 mold edge wear, the guide column offset 3 inflation, the parison is biased at the edge of the 4 clamp blank is too shallow or the depth of the knife edge is too shallow 5 parison inflation start too early.

Solution:

1 Lifting mold clamping pressure, suitable for reducing inflation pressure 2 Repairing the mold edge, correcting or replacing the mold guide post 3 Correcting the center position of the parison and the blowing rod 3 Trimming the mold, deepening the depth of the escape trough or the knife 4 Billet inflation time.

Seven, there are too deep vertical stripes:

cause:

1 Dirty 2 mold sleeve at the die mouth, the core edge has burrs or notches 3 color masterbatch or resin decomposition to produce dark stripes 4 filter mesh through the hole, the material mixed with impurities deposited in the die.

Solution:

1 Use a copper knife to clean the die 2 to trim the die 3 to properly lower the temperature, replace the disperse color masterbatch 4, replace the filter plate, and use the dip scrap.

Eight, the embryo is blown during molding:

cause:

1 mold blade is too sharp 2 parison has impurities or bubbles 3 blown ratio is too large 4 parison melt strength is low 5 parison length is less than 5 parison wall is too thin or parison wall thickness is not uniform 6 container bulging during mold opening Crack (insufficient deflation time) 7 mold clamping force is insufficient.

Solution:

1 Appropriately increase the width and angle of the knife edge 2 Use dry raw materials, use the wet raw materials after drying, use clean raw materials; clean the die mouth 3 to replace the mold sleeve, core, reduce the bad blow ratio 4 to replace the appropriate raw materials, appropriate Reduce the melt temperature 5 Check the control device of the extruder or the storage tank head, reduce the variation of the process parameters, increase the length of the parison 6 Replace the mold sleeve or core, thicken the parison wall; Check the parison control device; Adjust the die gap 7 to adjust the deflation time or delay the mold start-up time 8 to increase the clamping pressure or reduce the inflation pressure.

Nine, blow molding products are difficult to demould:

cause:

1 product inflation cooling time is too long, mold cooling temperature is low 2 mold design is bad, the surface of the cavity has burrs 3 when the mold is opened, the front and rear template moving speed is not balanced 4 mold installation error.

Solution:

1 Properly shorten the billet inflation time, raise the mold temperature 2 to trim the mold; reduce the groove depth, the rib slope is 1:50 or 1:100; use the release agent 3 to repair the clamping device, so that the front and rear template moving speed Consistently 4 re-install the mold to correct the mounting position of the two mold halves.

Ten, the quality of blow molding products fluctuates greatly:

cause:

1 parison wall thickness abrupt change 2 mixed corner reversal mixing uneven 3 feed section blockage, resulting in extruder discharge fluctuation 4 heating temperature imbalance.

Solution:

1 Repair parison control device 2 adopts a good mixing device to extend the mixing time; if necessary, reduce the amount of corner returning material 3 Remove the agglomerate material or foreign matter at the material inlet. Reduce the temperature at the material inlet 5 Replace the electric heating Court.