How to solve the uneven wall thickness of the twin-screw extruder?


1. Inaccurate positioning of the mouth template Due to […]

1. Inaccurate positioning of the mouth template
Due to the inaccurate positioning of the template in the die, the gap between the die is uneven, which causes the Ballas effect to be different, and eventually the wall thickness of the product is uneven after cooling.
Countermeasures: Correct the positioning pins between the templates and adjust the gap between the die.

2. The molding length of the die is short
The determination of the molding length of the die is the key to the design of the profile extrusion head. For different products, the molding length is different, the part of the wall thickness is small, and the flow rate is fast; the resistance of the thin wall is large, and the flow rate is slow.
Countermeasures: Refer to relevant manuals to appropriately lengthen the molding length of the die.

3. Uneven heating of the die
Due to the uneven heating temperature of the die heating plate or heating ring, the viscosity of the polymer melt in the die is inconsistent. After cooling and shrinking, uneven wall thickness will be produced.
Countermeasure: Adjust the temperature of the heating plate or heating ring.

4. Uneven wear of the die
The die is a part of the surface of the formed profile, and it will be worn and corroded in direct contact with the material. The uneven wear of the die is caused by the difference in material flow rate, flow, wall pressure, and resistance between the inner wall of the die and the different parts of the shunt cone.
Countermeasures: Use the method of "throttling and opening up" to repair the gap of the mouth template or the angle of the shunt cone.

5. The material contains impurities and blocks the flow channel
The blockage of the flow channel makes the flow velocity at the exit of the die uneven and the material is uneven, which causes uneven wall thickness of the product.
Countermeasures: Pay attention to the cleanliness of the raw materials and clean up the impurities in the die runner.