Abnormal die swell of the parison

In the extrusion '2079851475616104457 production process, the product exhibits the quality defect of "Abnormal die swell of the parison".The specific manifestation is The parison diameter abnormally expands and enlarges after extrusion.This defect is more common when processing materials such as HDPE, PP, PVC and PC, and its occurrence is usually related to unreasonable settings of melt temperature, extrusion speed, blowing pressure and mold temperature.When the Abnormal die swell of the parison situation is severe, it will cause a series of chain quality defects in the product's appearance, dimensional accuracy, mechanical properties and other aspects, which not only reduces the product's functionality and safety in use, but also directly increases the scrap rate and production cost.Therefore, this problem requires systematic diagnosis and optimization from multiple dimensions such as material selection, the status of the extruder, head, die, mold clamping mechanism and blowing system, and melt temperature, extrusion speed, blowing pressure and mold temperature.

1. Excessive elastic recovery of the resin.Material selection and handling are the foundation of forming quality.The intrinsic properties 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 raw materials, mixed impurities and improper regrind ratios will all cause various defects during processing. 2. Insufficient die length-to-diameter ratio.This factor causing the problem reflects that certain process conditions or material properties in extrusion '2079851475616104457 do not meet the optimal forming requirements.Such problems are often cumulative and concealed, and should be investigated and verified as key focus items during process debugging and finalization to ensure hidden dangers are eliminated at the source. 3. Temperature too low.Temperature is the core factor affecting melt fluidity and viscosity.Excessively high temperature settings will cause decreased melt viscosity, insufficient melt strength and even thermal degradation; excessively low temperature results in poor melt fluidity and insufficient plasticization, making smooth filling or forming impossible.A reasonable temperature window should be optimally determined within the recommended range according to the melting characteristics and thermal stability of the material. In terms of equipment maintenance, the regular overhaul and accuracy confirmation of the extruder, head, die, mold clamping mechanism and blowing system are not in place, causing the actual operating parameters of the equipment to deviate from process requirements, which will also become a potential inducement of the Abnormal die swell of the parison problem.

1. Raise the melt temperature.When implementing adjustments, it is recommended to use the single-factor variable method, adjusting only one parameter at a time and fully evaluating the effect, to avoid simultaneous changes of multiple parameters making the cause of the problem untraceable.The adjustment amplitude 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. 2. Increase the length of the die land.When implementing adjustments, it is recommended to use the single-factor variable method, adjusting only one parameter at a time and fully evaluating the effect, to avoid simultaneous changes of multiple parameters making the cause of the problem untraceable.The adjustment amplitude 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. 3. Select a resin with a higher MI value.Before introducing new tools, new materials or new methods, sufficient applicability evaluation and small-batch verification should be carried out.It is recommended to first conduct offline tests or simulation analyses outside production conditions, and introduce them into the formal production line only after confirming effectiveness and safety.Keep proper change management records to facilitate subsequent traceability and experience accumulation. In terms of material management, incoming inspection of raw materials and in-process testing of work-in-progress should be strengthened, and key performance indicators of HDPE, PP, PVC and PC should be strictly controlled to ensure the stability of forming quality from the source.

In summary, the causes of the "Abnormal die swell of the parison" problem can be attributed to the combined action of multiple factors such as Excessive elastic recovery of the resin, Insufficient die length-to-diameter ratio.To solve this problem, it is necessary to start from aspects such as Raise the melt temperature, Increase the length of the die land and take 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.