During the extrusion molding process in Dalian, the appearance of bubbles can seriously affect the quality of the product, such as reducing product strength, affecting appearance, and causing product defects. Therefore, avoiding the generation of bubbles is a key concern in the extrusion molding process. The following will elaborate on how to avoid the generation of bubbles during the extrusion molding process from the aspects of raw materials, equipment, process parameters, and operations.

1、 Raw material control

Choosing dry raw materials: Excessive moisture content in the raw materials is one of the main reasons for the formation of bubbles. Moisture will vaporize and form bubbles at high temperatures, therefore, the raw materials must be thoroughly dried before extrusion molding. Common drying methods include hot air drying, vacuum drying, etc. The drying temperature and time should be reasonably set according to the type and moisture content of the raw materials to ensure that the moisture content of the raw materials is controlled within the allowable range.

Using qualified raw materials: Impurities and low molecular weight volatiles mixed in the raw materials can also cause the generation of bubbles. Therefore, raw materials with stable quality and low impurity content should be selected, and strict inspection should be conducted before use.

Avoid moisture in raw materials: Dry raw materials should be stored properly to prevent moisture. Sealed containers or desiccants can be used to keep the raw materials dry.

2、 Equipment maintenance

Regularly clean the screw and barrel: Accumulation of materials, carbides, etc. on the inner walls of the screw and barrel can hinder the flow of materials and may cause local overheating, resulting in the formation of bubbles. Therefore, the screw and barrel should be cleaned regularly to maintain their cleanliness.

Check the heating system: Inaccurate temperature control of the heating system can lead to uneven material temperature, resulting in the formation of bubbles. The heating system should be regularly inspected to ensure accurate temperature control in each heating zone and necessary calibration should be carried out.

Ensure the normal operation of the vacuum system: The vacuum system can effectively remove gases from materials and reduce the generation of bubbles. The vacuum system should be checked regularly to ensure its normal operation, and the vacuum level should be adjusted as needed.

3、 Optimization of process parameters

Reasonable setting of extrusion temperature: Excessive extrusion temperature can lead to material degradation and the generation of bubbles; If the temperature is too low, it will lead to poor plasticization of the material, poor fluidity, and easy formation of bubbles. The extrusion temperature should be set reasonably according to the type and performance of the material, and necessary adjustments should be made.

Control screw speed: If the screw speed is too fast, it will cause the material to shear and overheat, resulting in bubbles; If the speed is too slow, it will cause the material to stay for too long and also easily generate bubbles. The screw speed should be reasonably controlled according to the type of material and product requirements.

Adjust the head pressure: If the head pressure is too low, it will cause insufficient exhaust of the material, resulting in bubbles; Excessive pressure can lead to difficulties in material flow and the formation of bubbles. The head pressure should be adjusted reasonably according to the type of material and product requirements.

4、 Operating standards

Standardized feeding operation: During feeding, air should be avoided and methods such as vacuum feeding or vibration feeding can be used.

Control extrusion speed: If the extrusion speed is too fast, it will cause the material to be unable to exhaust in time, resulting in bubbles; If the speed is too slow, it will affect production efficiency. The extrusion speed should be reasonably controlled according to the type of material and product requirements.

Observing the appearance of the product: During the extrusion molding process, the appearance of the product should be closely observed to promptly detect defects such as bubbles and make corresponding adjustments.

5、 Other measures

Use defoamer: In some cases, an appropriate amount of defoamer can be added to suppress the generation of bubbles. However, it should be noted that the amount and usage of defoamers should be strictly in accordance with the product instructions to avoid adverse effects on product performance.

Improving mold design: Reasonable mold design can improve the flow state of materials and reduce the generation of bubbles. For example, measures such as gradually expanding flow channels and increasing exhaust slots can be adopted.

Avoiding the generation of bubbles during the extrusion molding process requires comprehensive consideration of raw materials, equipment, process parameters, and operations. By strictly controlling the quality of raw materials, regularly maintaining equipment, optimizing process parameters, standardizing operating procedures, and taking necessary auxiliary measures, the generation of bubbles can be effectively reduced and product quality can be improved.

It should be noted that different materials and products have varying degrees of sensitivity to bubbles. Therefore, in actual production, it is necessary to flexibly apply the above methods according to specific situations, and continuously optimize the process based on practical experience, in order to achieve better anti bubble effects.