Bottle body brittle cracking (drop cracking)

During the extrusion '2079851475616104457 production process, the product exhibits the quality defect of "Bottle body brittle cracking (drop cracking)". Specifically manifested as brittle fracture of the product in the drop test. 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 Bottle body brittle cracking (drop cracking) 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. Resin melt index too low. 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. Regrind proportion too high. 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. Insufficient strength at the weld line. The mechanical properties of the material and the structural strength of the product directly determine the safety and reliability of the product in use. The root of insufficient strength may come from factors such as the intrinsic properties of the material, degradation caused by processing, poor welding, and stress concentration caused by uneven wall thickness. Improving strength requires coordinated improvements in material selection, process optimization, and structural design. 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 Bottle body brittle cracking (drop cracking) problem.

1. Select a resin with an appropriate MI value. Before introducing new tools, new materials, or new methods, a full applicability assessment and small-batch verification should be carried out. It is recommended to first conduct offline tests or simulation analysis outside of production conditions, and introduce them into the formal production line only after confirming effectiveness and safety. Keep change management records to facilitate subsequent traceability and experience accumulation. 2. Reduce the regrind proportion. Adjustments should follow the principle of gradual progress; the magnitude of each adjustment should not be too large, and it is recommended to decrease in steps of 5%~15% of the current value. After each adjustment, observe the product quality changes stably for at least 5~10 mold cycles, and continue adjusting only after confirming that the improvement direction is correct; one-step excessive adjustment must be avoided. 3. Optimize the pinch-off to reduce the influence of weld lines. Adjustments should follow the principle of gradual progress; the magnitude of each adjustment should not be too large, and it is recommended to decrease in steps of 5%~15% of the current value. After each adjustment, observe the product quality changes stably for at least 5~10 mold cycles, and continue adjusting only after confirming that the improvement direction is correct; one-step excessive adjustment must be avoided. 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 "Bottle body brittle cracking (drop cracking)" problem can be attributed to the combined action of multiple factors such as resin melt index too low and regrind proportion too high. Solving this problem requires starting from aspects such as select a resin with an appropriate MI value and reduce the regrind proportion, 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.