Rough product inner wall (flow marks)

In the rotational molding production process, the product exhibits the quality defect of "Rough product inner wall (flow marks)". The specific manifestation is that the inner wall surface of the product is rough or has flow marks. This defect is relatively common when processing materials such as LLDPE, HDPE, PVC, PA and other powders, and its occurrence conditions are usually related to the unreasonable settings of heating temperature and time, rotation speed ratio, cooling rate, and mold wall thickness. When the "Rough product inner wall (flow marks)" situation is severe, it will cause a series of chain quality defects in the product in terms of appearance, dimensional accuracy, mechanical properties, etc., which not only reduces the functionality and safety of the product 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 rotational molding machine, heating oven, rotating arm, and cooling station, and heating temperature and time, rotation speed ratio, cooling rate, and mold wall thickness.

1. Insufficient melting of the powder. This factor causing the problem reflects that certain process conditions or material characteristics in rotational '2079851475616104453ing have not met the optimal molding requirements. Such problems are often cumulative and hidden, and should be investigated and verified as key focus items during process debugging and finalization to ensure that hidden dangers are eliminated at the source. 2. Insufficient sintering temperature. Temperature is the core factor affecting melt fluidity and viscosity. A temperature set too high will cause the melt viscosity to decrease, insufficient melt strength, and even thermal degradation; a temperature that is too low results in poor melt fluidity and insufficient plasticization, making it impossible to fill or form smoothly. A reasonable temperature window should be optimized and determined within the recommended range according to the melting characteristics and thermal stability of the material. 3. Improper powder particle size. This factor causing the problem reflects that certain process conditions or material characteristics in rotational '2079851475616104453ing have not met the optimal molding requirements. Such problems are often cumulative and hidden, and should be investigated and verified as key focus items during process debugging and finalization to ensure that hidden dangers are eliminated at the source. In terms of equipment maintenance, the regular overhaul and precision confirmation of the rotational molding machine, heating oven, rotating arm, and cooling station 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 "Rough product inner wall (flow marks)" problem.

1. Increase the sintering temperature and time. 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 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. Select powder with appropriate particle size. 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 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. It is recommended to formulate a preventive checklist for the "Rough product inner wall (flow marks)" problem, incorporate powder melting uniformity and product wall thickness control into the daily inspection scope, and conduct online monitoring of key parameters through the SPC statistical process control method to achieve early warning and rapid response to the problem. In terms of material management, incoming inspection of raw materials upon arrival and in-process inspection of work-in-progress should be strengthened, and the key performance indicators of LLDPE, HDPE, PVC, PA and other powders should be strictly controlled to ensure the stability of molding quality from the source.

In summary, the causes of the "Rough product inner wall (flow marks)" problem can be attributed to the combined action of multiple factors such as Insufficient melting of the powder, Insufficient sintering temperature. Solving this problem requires starting from aspects such as Increase the sintering temperature and time, Select powder with appropriate particle size 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 powder melting uniformity and product wall thickness control.