Cracking at Product Corners

In the rotational molding production process, the product exhibits the quality defect of 「Cracking at Product Corners」. The specific manifestation is that the product cracks at corners during use. This defect is relatively common when processing powder materials such as LLDPE, HDPE, PVC, and PA, and its occurrence conditions are usually related to unreasonable settings of heating temperature and time, rotation speed ratio, cooling rate, and mold wall thickness. When the Cracking at Product Corners situation is severe, it will cause a series of chain quality defects in the product in terms of appearance, dimensional accuracy, and mechanical properties, which not only reduces the product's use functionality and safety, but also directly increases the scrap rate and production cost. Therefore, this problem needs to be systematically diagnosed and optimized from multiple dimensions such as material selection, the rotational molding machine, the heating oven, the rotating arm, the cooling station status, and heating temperature and time, rotation speed ratio, cooling rate, and mold wall thickness.

1. Stress concentration at corners. This factor leading to the problem reflects that certain process conditions or material properties 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 from the source. 2. Insufficient wall thickness. The uniformity of wall thickness distribution is directly related to the mechanical properties of the product and the consistency of cooling shrinkage. Excessive wall thickness differences will lead to inconsistent cooling rates, sink marks and warpage in thick-walled areas, and insufficient strength in thin-walled areas. Wall thickness design should follow the uniform wall thickness principle, and wall thickness changes should transition smoothly. 3. Large internal stress. This factor leading to the problem reflects that certain process conditions or material properties 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 from the source. In terms of equipment maintenance, the regular overhaul and accuracy 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 process requirements, which will also become a potential inducement of the Cracking at Product Corners problem.

1. Increase the corner radius. 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 problem cause 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 cycles to observe the effect. 2. Increase the wall thickness at corners. 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 problem cause 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 cycles to observe the effect. 3. Optimize the process to reduce internal stress. Adjustments should follow the principle of gradual progress, and each adjustment amplitude should not be too large; it is recommended to decrease in steps of 5%~15% of the current value. After each adjustment, stably observe the product quality changes for at least 5~10 cycles, and continue adjusting only after confirming that the improvement direction is correct; avoid one-step excessive adjustment. In terms of material management, incoming inspection of raw materials and in-process inspection of work-in-progress products should be strengthened, and the key performance indicators of powder materials such as LLDPE, HDPE, PVC, and PA should be strictly controlled to ensure the stability of molding quality from the source.

In summary, the causes of the 「Cracking at Product Corners」 problem can be attributed to the combined effects of multiple factors such as stress concentration at corners and insufficient wall thickness. To solve this problem, it is necessary to start from aspects such as increasing the corner radius and increasing the wall thickness at corners and take systematic treatment 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.