Parison Diameter Fluctuation

In the extrusion '2079851475616104457 production process, the product shows the quality defect of "parison diameter fluctuation". The specific manifestation is periodic or non-periodic changes in the parison diameter. This defect is relatively common when processing materials such as HDPE, PP, PVC, PC, and its occurrence conditions are usually related to unreasonable settings of melt temperature, extrusion speed, blowing pressure, and mold temperature. When the parison diameter fluctuation is severe, it will cause a series of chain quality defects in appearance, dimensional accuracy, mechanical properties and other aspects of the product, 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, extruder, die head, die, mold clamping mechanism, blowing system status, and melt temperature, extrusion speed, blowing pressure, mold temperature.

1. Melt pressure fluctuation. Pressure directly determines the filling ability and mold-contacting effect of the melt during the forming process. Insufficient pressure results in incomplete filling and poor replication accuracy; excessive pressure may cause secondary defects such as flash and excessive internal stress. The setting of pressure should comprehensively consider factors such as material viscosity, product size and mold structure. 2. Unstable screw axial force. 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. This type of problem is often cumulative and concealed, and should be investigated and verified as a key focus item during process debugging and finalization to ensure that hidden dangers are eliminated from the source. In addition, insufficient overall coordination of parison wall thickness control and parison temperature uniformity is also a factor that cannot be ignored; there are complex interactions and coupling relationships among the process parameters, and the deviation of any parameter may aggravate the degree of parison diameter fluctuation through chain effects. In terms of equipment maintenance, the regular overhaul and accuracy confirmation of the extruder, die head, die, mold clamping mechanism and blowing system are not in place, causing the actual operating parameters of the equipment to deviate from the process requirements, which will also become a potential inducement of the parison diameter fluctuation problem.

1. Install a pressure-stabilizing device between the die head and the extruder. The installation of equipment or accessories should strictly follow the installation instructions, and the key mating surfaces must be cleaned and checked for damage before installation. Fastening bolts should be tightened evenly according to the specified torque value and diagonal sequence, and after installation, use precision measuring tools to verify whether the installation accuracy meets the technical requirements. 2. Check the wear condition of the screw. A standardized inspection checklist should be established for inspection work, clarifying inspection items, technical standards, inspection frequency and responsible persons. Key equipment components should be regularly disassembled to inspect the status 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 should be established to predict potential failures. It is recommended to formulate a preventive inspection checklist for the parison diameter fluctuation problem, incorporate parison wall thickness control and parison temperature uniformity into the scope of daily inspection, and use the SPC statistical process control method to monitor key parameters online to achieve early warning and rapid response to problems. In terms of material management, the 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, PC should be strictly controlled to ensure the stability of molding quality from the source.

In summary, the causes of the "parison diameter fluctuation" problem can be attributed to the combined effect of multiple factors such as melt pressure fluctuation and unstable screw axial force. Solving this problem requires starting from aspects such as installing a pressure-stabilizing device between the die head and the extruder and checking the wear condition of the screw, and adopting systematic governance measures. In actual production, it is recommended to establish a prevention and rapid response mechanism for this problem, and achieve stable production and continuous improvement through parison wall thickness control and parison temperature uniformity.