Blow molding products common ten problems

First, the longitudinal wall thickness of blow molding products is not uniform:

Causes: (1) the dead weight of the billet sagging phenomenon is serious (2) the longitudinal diameter of the two cross sections of the blow molding products is too big

Solution measures: (1) reduce the melt temperature of the billet, improve the extrusion speed of the billet, replace the resin with lower melt flow speed, adjust the control device of the billet, (2) appropriately change the product design, and adopt the bottom blowing molding method

Two, blow molding products transverse wall thickness is not uniform:

The causes are as follows: (1) the billet extrusion skew (2) the temperature difference between the inner and outer parts of the die sleeve and the die core is large (3) the shape of the products is not symmetrical (4) the billet blowing ratio is too large

Solution measures: ① adjust the gap width deviation of the mouth die, so that the blank wall thickness is uniform; Before the die is closed, the straightening is bad; ② the heating temperature of the die sleeve is raised or lowered to improve the temperature deviation between the inside and outside of the die; ③ before the die is closed, the blank is pre-clamped and pre-expanded to make the blank offset to the thin wall properly; ④ the blowing and swelling ratio of the blank is reduced

Three, blow molding product surface appears orange peel pattern or pitting:

Causes: ① Bad exhaust of the mold ② Water leakage of the mold or condensation of the mold cavity ③ Bad plasticization of the mold billet, melt rupture of the mold billet ④ Lack of blowing pressure

The blowing speed is slow and the blowing ratio is too small

Solutions: (1) mould parison sandblasting processing, additional vents (2) to repair the mold, to adjust the mould cooling temperature above the "dew point" (3) reduce the screw rotation speed, enhance the extruder temperature (4) high blowing air pressure (5) clean compressed air channel, check whether the blow bar is flat 6 replacement mold, mold core, DiGaoXing billet blowing ratio

Four, blow molding product volume reduction:

Causes: ① the thickness of the blank wall increases, leading to the thickness of the product wall ② the shrinkage rate of the product increases, leading to the size of the product shrinkage ③ the blowing pressure is small, the product is not blown to the design size of the cavity

Solutions: ① Adjust the program control device to reduce the thickness of the billet wall; Increase the melt temperature of the billet, reduce the expansion ratio of the billet from the mold, replace the resin with small shrinkage rate, prolong the blowing time, reduce the cooling temperature of the mold, and raise the pressure of the compressed air appropriately

Five, blow molding products outline or graphics are not clear:

Causes: ① Bad air exhaust of mold cavity ② Low blowing pressure ③ Low melt temperature of mold billet, poor plasticization of materials ④ Low cooling temperature of mold and "condensation" of mold

Solutions: (1) repair the mold, cavity sandblasting treatment or additional exhaust groove (2) improve the blowing pressure (3) appropriately improve the extruder and machine head heating temperature, when necessary to add a proper amount of filling master material (4) to the mold temperature above the dew point temperature

Six, blow molding products too much edge, too thick:

Causes: ① mold expansion, mold locking pressure is insufficient ② die edge wear, guide column deviation ③ when blowing, blank deflection ④ the blank blade escape groove is too shallow or the knife edge depth is too shallow ⑤ the billet charging start too early

Solutions: ① Raise the mold locking pressure, suitable for reducing the blowing pressure ② repair the mold blade, correct or replace the mold guide post ③ correct the central position of the blank and the blowing rod ③ dress the mold, deepen the depth of the escape groove or the knife ④ adjust the billet charging time

Seven, appear too deep longitudinal stripes:

Causes: ① die mouth dirty ② die sleeve, core edge has burr or gap ③ color master material or resin decomposition to produce dark stripes ④ filter hole, material mixed with impurities deposited in the die mouth

Solution measures: ① clean the die mouth with copper knife ② dress the die mouth ③ reduce the temperature appropriately, replace the masterbatch with good dispersion ④ replace the filter screen plate, and use the scraps with the material

VIII. The mold embryo is blown out during molding:

Causes: (1) the die edge is too sharp (2) the billet has impurities or bubbles (3) the blowing ratio is too large (4) the billet melt strength is low (5) the billet length is not enough (5) the billet wall is too thin or the billet wall thickness is not uniform (6) the container in the opening of the mold bulging crack (insufficient deflating time)⑦ the mold locking force is not enough

Solutions:

(1) appropriately increase the width and Angle of the knife edge (2) the use of dry raw materials, wet raw materials after drying, the use of clean raw materials; Clean the die mouth (3) replace the die sleeve and die core, reduce the blowing ratio of the type bad (4) replace the appropriate raw materials, appropriately reduce the melt temperature (5) check the control device of the extruder or the storage cylinder head, reduce the change of process parameters, increase the length of the blank (6) replace the die sleeve or die core, and thaw the blank wall; Check the billet control device; Adjust the gap between the die mouth ⑦ adjust the deflating time or delay the start time of the die opening; raise the pressure of the lock or reduce the blowing pressure

Nine, blow molding products demoulding difficulties:

Causes: (1) the cooling time of the products is too long, the cooling temperature of the mold is low, (2) the mold design is poor, the surface of the cavity has burr, (3) when the mold is opened, the moving speed of the front and rear templates is not balanced, and (4) the mold is installed wrong

Solutions:

(1) Appropriately shorten the billet blowing time, improve the mold temperature (2) dressing the mold; Reduce the depth of the groove, the slope of the convex rib is 1:50 or 1:100; Use release agent ③ to repair the mold locking device so that the front and rear formwork move at the same speed ④ reinstall the mold and correct the installation position of the two halves of the mold

Ten, the quality of blow molding products fluctuates greatly:

Causes: (1) sudden change in the thickness of the billet wall (2) uneven mixing of the mixing edges and corners (3) blockage of the feed section, resulting in fluctuation of the extruder discharge (4) uneven heating temperature

Solution measures: ① repair billet control device ② use good mixing device, prolong mixing time; When necessary, reduce the amount of return material at the edges and corners (3) remove lumps at the material mouth (4) material or foreign bodies. Reduce the temperature at the material outlet ⑤ replace the electric heating cabinet