How to eliminate the defects in Suzhou blow molding processing technology

1. Key points of process control for blow molding in Suzhou

1) For extrusion blow molding

Pay attention to controlling the sagging phenomenon and wrinkling defects of the billet. If the vertical extension is too long, the wall thickness will decrease and the amount of residual material removed will also increase; If the vertical extension is not enough and the billet is too short, it cannot be inflated.

2) Wrinkling phenomenon

When the billet descends to a certain length, circumferential stress occurs due to the inability of the upper melt of the billet to bear its own weight; Generally, high melt strength, small expansion of billet diameter, high extrusion rate, and larger die gap all contribute to improving wrinkles.

3) Uneven wall thickness

Another issue is that when the billet descends, the wall thickness is uneven. Usually, a hexagonal nut is installed on the die of the machine head to adjust the gap between the core rod and the die.

4) Make sure to exhaust properly

To achieve good surface quality of the parts, attention must be paid to exhaust. For example, PE material is sandblasted on the surface of the mold with a particle size of less than 180 #, while blow molds made of hard plastic have exhaust holes, exhaust needles, and exhaust grooves; In addition, increasing the inflation pressure can also help improve the appearance of the product.

2. Defect elimination in Suzhou blow molding processing

1) Wrinkles

Check if the head die and core rod are coaxial

Reduce the temperature of the billet

Increase the die gap or molding section length of the machine head

Choose polymers with smaller expansion of the preform

2) Uneven length

Check for bridging of raw materials in the feeding hopper

Check if the temperature in the feeding section of the barrel is too high

Check for fluctuations in screw speed

Increase the back pressure of the extruder

Check the temperature control device of the extruder and head

Check for wear on the screw and barrel

Check if the recycled and new materials are mixed evenly

Check if the filter screen is cracked or partially blocked by magazines

3) Bubble hole

Strictly dry hygroscopic polymers

Heat the raw materials in the hopper to remove moisture

Reduce the water cooling capacity at the inlet of the extruder

Check and remove impurities from the raw materials

Clear the material accumulation inside the extruder and head, avoid explanation

Increase the back pressure of the extruder

4) Stripes

Remove impurities from raw materials

Remove impurities accumulated inside the machine head

Avoid material accumulation and explanation

Reduce the temperature of the billet

Polish or replace the die of the machine head

Replace the burnt heating coil

5) Gel

Screen out the fines from the recycled materials

Dry raw materials

Improve the dispersion and mixing performance of the screw and reduce the barrel size