Wall thickness too thin after mold closing

During the extrusion '2079851475616104457 production process, the product exhibits the quality defect of "Wall thickness too thin after mold closing". Specifically manifested as the parison being squeezed during mold closing, resulting in locally thin wall thickness. 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 Wall thickness too thin after mold closing 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. Pinch-off design too tight. Unreasonable structural design or process layout is often the systemic root of the problem. Runner design defects causing uneven flow, unreasonable cooling water channel layout causing temperature differences, insufficient venting structures causing air entrapment, etc., are all fundamental problems that need to be solved with emphasis during the design and development stage. 2. Parison diameter too large. 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. In addition, insufficient overall coordination between 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 various process parameters, and the deviation of any single parameter may aggravate the degree of Wall thickness too thin after mold closing through chain effects. 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 Wall thickness too thin after mold closing problem.

1. Optimize the pinch-off angle and depth. Optimization work must be based on an accurate diagnosis of the root cause of the problem, and blind attempts must be avoided. It is recommended to first determine the key influencing factors and their interactions through the process DOE test method or historical production data analysis, and then carry out targeted parameter optimization and structural improvement to achieve twice the result with half the effort. 2. Appropriately reduce the parison diameter. 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. It is recommended to formulate a preventive checklist for the Wall thickness too thin after mold closing problem, incorporate parison wall thickness control and parison temperature uniformity into the scope of daily inspections, and conduct online monitoring of key parameters through the SPC statistical process control method to achieve early warning and rapid response to problems. 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 "Wall thickness too thin after mold closing" problem can be attributed to the combined action of multiple factors such as pinch-off design too tight and parison diameter too large. Solving this problem requires starting from aspects such as optimize the pinch-off angle and depth and appropriately reduce the parison diameter, 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.