In the molding process of extrusion blow molding products, there are always many technical problems. We will share with you the reasons for these problems and the solutions to them. We hope to provide suggestions for solving problems.
First, the longitudinal wall thickness of the blow molded products is not uniform:
cause:
1 There is a serious sagging of the self-weight of the parison
2 blow molding products longitudinal two cross-sectional diameter difference is too big
solution:
1Reducing the parison melt temperature, increasing the parison extrusion speed, replacing the resin with a lower melt flow rate, and adjusting the parison control device
2 Appropriately change the product design, use the bottom blowing method Second, the transverse thickness of the blow molded products is not uniform:
cause:
1 parison extrusion skew
2 mold sets and mold core temperature difference between inside and outside
3 product appearance asymmetry
Excessive blow-up ratio of parison 4
solution:
1Adjust the die gap width deviation, make the parison wall thickness uniform; before closing the die, straighten the type bad
2 Raise or reduce the mold heating temperature to improve the temperature deviation inside and outside the mold
3 Pre-clamping and pre-expanding of the parison before closing the mold, so that the parison is properly offset in the direction of the thin wall
4 reduce the parison blowing ratio Third, the appearance of orange-like patterns or spots on the surface of blow molded products:
cause:
1 mold exhaust failure
2 mold leakage or mold cavity condensation
3 Poor plasticization, melt fracture of parison 4 Insufficient inflation pressure
5 slow inflation
6 Blow-up ratio is too small
solution:
1 mold parison blasted, add exhaust hole
2 Repair the mold, adjust the mold cooling temperature to above the dew point
3 Reduce the screw speed, increase the extruder heating temperature
4 Raise inflation pressure
5 Clear the compressed air passage and check if the blow pin is leaking
6 Replace the mold sleeve, mold core, improve the inflation ratio of the parison
Fourth, blow-molded product volume reduction: cause:
1 The parison wall thickness increases, resulting in a thicker wall
2 Increased product shrinkage, resulting in shrinkage of product size
3 Inflated air pressure is small, the product is not blown to the cavity design size
solution:
1Adjust the program control device to reduce the wall thickness of the parison; increase the temperature of the parison melt and reduce the parison expansion ratio of the parison
2Replace the resin with small shrinkage, prolong the blowing time, reduce the cooling temperature of the mold
3 properly mention the pressure of compressed air
Fifth, the outline or graphic of blow molding products is not clear: cause:
Poor cavity 1
2 low inflation pressure
3 parison melt temperature is low, poor material plasticization
4 mold cooling temperature is low, the mold has 'condensation' phenomenon
solution:
1 repair mold, cavity blasting or add exhaust slots
2 increase inflation pressure
3 Appropriately increase the heating temperature of the extruder and head, and if necessary, add an appropriate amount of filler masterbatch
4 adjust the mold temperature to the dew point temperature
Sixth, blow molding products too many flashes, too thick: cause:
1 mold expansion mold, insufficient clamping pressure
2 mold blade wear, guide column offset
3 During the inflation, parison deflection
4 The blanking slot at the knife blank is too shallow or the depth of the knife edge is too shallow
5 parison inflation start prematurely
solution:
1 mention mold clamping pressure, suitable for reducing inflation pressure
2 Repair the die edge, correct or replace the die guide
3 Correct the center position of the parison and blow pin
3 Trim the mold to deepen the depth of the escape slot or knife
4 Adjust the inflation time of the parison Seven, there have been deep vertical stripes: cause:
1 die mouth dirty
2 die sets with burrs or nicks on core edges
3-color masterbatch or resin decomposed to produce dark stripes
4 The filter passes through the hole and the material is mixed with impurities deposited on the die
solution:
1 Use a copper knife to clean the die
2 trimming die
3 properly reduce the temperature, replace the good color masterbatch
4 Replace the filter plate, use the stain scrap
Eight, the embryo is blown during molding: cause:
1 mold blade is too sharp
2 parisons have impurities or air bubbles
3 Blowing ratio is too large
4 parison melt strength is low
5 lack of parison length
5 The parison wall is too thin or the thickness of the parison is not uniform
6 The container bursts during mold opening (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 wet raw materials after drying, use clean raw materials, clean molds
3 Replace the mold sleeve, mold core, reduce the bad blow ratio
4 replace the appropriate raw materials, appropriately reduce the melt temperature
5 Check the control device of the extruder or storage cylinder head to reduce the change of process parameters, increase the length of the parison 6 Replace the mold sleeve or mold core, thicken the parison wall; Check the parison control device; Adjust the gap of the mold mouth
7Adjust the deflation time or delay the die start time
8 Raise the clamping pressure or reduce the inflation pressure Nine, blow molding products difficult to remove: cause:
1 product blowing cooling time is too long, mold cooling temperature is low
2 poor mold design, cavity surface burr
3At the time of mold opening, the speed of the template movement before and after the balance is not balanced.
4 mold installation error
solution:
1Appropriately shorten the inflation time of the parison and raise the mold temperature
2Rebuild the mold; reduce the depth of the groove, the slope of the ribs is 1: 50 or 1: 100; use mold release agent
3 Repair the clamping device so that the moving speeds of the front and rear templates are the same
4 Reinstall the mold and correct the installation position of the mold halves
Tenth, the quality of blow molding products fluctuates greatly: Causes:
1 sudden change in wall thickness
2 Incorporate uneven mixing of corners
3 feed blockage, causing extruder discharge fluctuations
4 uneven heating temperature
solution:
1 Repair the parison control device
2Use a good mixing device to extend mixing time; if necessary, reduce the amount of material used for corners
3 removal of agglomerates at the material outlet
4 material or foreign matter. Reduce the temperature at the material outlet
5 Replace Electric Heating Cabinet