Local Thickening of Product Wall Thickness

In the rotational molding production process, the product exhibits the quality defect of 「Local Thickening of Product Wall Thickness」. The specific manifestation is that the product wall thickness thickens abnormally in local areas. 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 Local Thickening of Product Wall Thickness 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. Uneven distribution of powder in the mold. The mold is the core tool that gives the product its shape and surface quality. Unreasonable mold design, such as improper runner/gate dimensions, insufficient venting, and insufficient demolding draft angle, will directly lead to molding defects. The machining accuracy, surface treatment quality, and daily maintenance status of the mold also directly affect product quality. 2. Improper rotation speed causing powder accumulation. Speed parameters affect the flow state and time allocation of the melt during the '2079851475616104453. Too slow a speed leads to premature cooling and insufficient filling; too fast a speed causes melt fracture, air entrapment, and shear overheating. The optimization of the speed curve should make the melt flow smoothly and orderly in the cavity. In addition, insufficient overall coordination of powder melting uniformity and product wall thickness control is also a factor that cannot be ignored. There are complex interactions and coupling relationships among various process parameters, and the deviation of any parameter may aggravate the degree of Local Thickening of Product Wall Thickness through chain effects. 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 Local Thickening of Product Wall Thickness problem.

1. Optimize the rotation speed and speed ratio. Optimization work needs to be based on accurate diagnosis of the root cause of the problem, and blind attempts should be avoided. It is recommended to first determine the key influencing factors and their interactions through process DOE test methods 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. Improve the uniformity of powder distribution. Optimization work needs to be based on accurate diagnosis of the root cause of the problem, and blind attempts should be avoided. It is recommended to first determine the key influencing factors and their interactions through process DOE test methods or historical production data analysis, and then carry out targeted parameter optimization and structural improvement to achieve twice the result with half the effort. It is recommended to formulate a preventive inspection checklist for the Local Thickening of Product Wall Thickness problem, incorporate powder melting uniformity and product wall thickness control into the scope of daily patrol 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 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 「Local Thickening of Product Wall Thickness」 problem can be attributed to the combined effects of multiple factors such as uneven distribution of powder in the mold and powder accumulation caused by improper rotation speed. To solve this problem, it is necessary to start from aspects such as optimizing the rotation speed and speed ratio and improving the uniformity of powder distribution 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.