Bubbles inside the product (pinholes)

In the rotational molding production process, the product exhibits the quality defect of "Bubbles inside the product (pinholes)". The specific manifestation is that bubbles or pinholes appear on the inner wall of the product. 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 "Bubbles inside the product (pinholes)" 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. Air entrapped in the powder not discharged. 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. Bubbles not eliminated during the melting process. 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. 3. Water in the resin. 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 properties. Factors such as raw material moisture content exceeding the standard, impurity mixing, and improper regrind ratio will all cause various defects during processing. 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 "Bubbles inside the product (pinholes)" problem.

1. Optimize the heating temperature and time. 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 parameter optimization and structural improvement in a targeted manner to achieve twice the result with half the effort. 2. Use dry powder. 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. 3. Improve degassing conditions. 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 parameter optimization and structural improvement in a targeted manner to achieve twice the result with half the effort. 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 "Bubbles inside the product (pinholes)" problem can be attributed to the combined action of multiple factors such as Air entrapped in the powder not discharged, Bubbles not eliminated during the melting process. Solving this problem requires starting from aspects such as Optimize the heating temperature and time, Use dry powder 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.