Bubbles

During the extrusion '2079851475616104457 production process, the product exhibits the quality defect of "Bubbles". Specifically manifested as bubbles appearing in the product wall or on the surface. This defect is relatively common when processing materials such as HDPE, PP, PVC, and PC, and its occurrence conditions are usually related to unreasonable settings of melt temperature, extrusion speed, blowing air pressure, and mold temperature. When the Bubbles situation is severe, it will cause a series of chain-reaction quality defects in the product in terms of appearance, dimensional accuracy, mechanical properties, etc., which not only reduces the usability and safety of the product, but also directly increases the scrap rate and production cost. Therefore, this problem requires systematic diagnosis and optimization from multiple dimensions, including material selection, the condition of the extruder, die head, die, mold clamping mechanism, and blowing system, as well as melt temperature, extrusion speed, blowing air pressure, and mold temperature.

1. Moisture content of the raw material too high. The selection and handling of materials is the foundation of molding quality. The intrinsic characteristics of the resin, such as molecular weight, molecular weight distribution, and melt index, determine its processing window and final performance. Factors such as excessive moisture content of the raw material, mixing in of impurities, and improper proportion of regrind will all trigger various defects during processing. 2. Air entrapped in the melt. This factor leading to the problem reflects that certain process conditions or material properties in extrusion blow '2079851475616104453ing have not met the optimal molding requirements. Such problems often have cumulative and hidden characteristics, and should be investigated and verified as key focus items during process debugging and finalization to ensure that hidden dangers are eliminated from the source. 3. Poor screw venting. Mold venting is a basic condition to ensure smooth filling of the melt. When venting is poor, the air in the mold cavity is compressed to form a high-pressure air cushion, which hinders melt flow and causes problems such as insufficient filling, burnt, and weld lines. A reasonable venting design should consider the venting position and venting gap to ensure that air is discharged in time. In terms of equipment maintenance, inadequate regular overhaul and accuracy confirmation of the extruder, die head, die, mold clamping mechanism, and blowing system cause the actual operating parameters of the equipment to deviate from the process requirements, which can also become a potential inducement of the Bubbles problem.

1. Fully dry the raw material. Raw '2079851475616104451 should select a matching type of drying equipment according to the resin type and water absorption characteristics, and reasonably set the drying temperature, drying time, and dew point indicators. The dried raw material should be put into production use as soon as possible; if temporary storage is required, it should be kept in a sealed container in a dry environment (dew point below -30℃). Regularly test the drying effect to ensure that the moisture content meets the standard. 2. Check the screw venting section. Inspection work should establish a standardized inspection checklist, clarifying the inspection items, technical standards, inspection frequency, and responsible persons. Key equipment components should be regularly disassembled to inspect the condition of hidden parts, and judgment should not be based solely on operating appearance. Inspection results should be recorded in detail and a trend analysis mechanism established to predict potential failures. 3. Increase the back pressure to expel air. When implementing adjustments, it is recommended to adopt the single-factor variable method, adjusting only one parameter at a time and fully evaluating the effect, to avoid multiple parameters changing simultaneously making the cause of the problem untraceable. The adjustment magnitude should be small rather than large; each adjustment is recommended to be controlled within 5%~10% of the original value, and after adjustment, run stably for at least 3~5 mold cycles to observe the effect. In terms of material management, incoming inspection of raw materials and in-process inspection of work-in-progress should be strengthened, and the key performance indicators of HDPE, PP, PVC, and PC should be strictly controlled to ensure the stability of molding quality from the source.

In summary, the causes of the "Bubbles" problem can be attributed to the combined action of multiple factors such as moisture content of the raw material too high and air entrapped in the melt. Solving this problem requires starting from aspects such as fully dry the raw material and check the screw venting section, and adopting systematic governance measures. In actual production, it is recommended to establish a prevention and rapid response mechanism for this problem, achieving stable production and continuous improvement through parison wall thickness control and parison temperature uniformity.