Streaks on the Product Surface

In the rotational molding production process, the product exhibits the quality defect of 「Streaks on the Product Surface」. The specific manifestation is that regular or irregular streaks appear on the product surface. 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 Streaks on the Product Surface 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. Scratches on the mold surface. 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. Unstable rotation speed. 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. 3. Uneven heating. Uniformity runs through every link of the '2079851475616104453. Uneven temperature, uneven pressure distribution, uneven cooling, and uneven material mixing will all lead to dispersion in product quality. Ensuring the uniform distribution of all physical quantities is a prerequisite for obtaining products with good consistency and stable quality. 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 Streaks on the Product Surface problem.

1. Polish the mold surface. Polishing operations should proceed step by step from coarse to fine, and the grinding direction should be changed each time a finer abrasive is used to eliminate the texture marks from the previous pass. The final surface roughness should be tested with a roughness meter to confirm it meets the standard. After polishing, thoroughly clean to remove abrasive and grinding agent residues to prevent them from entering the melt and contaminating the product. 2. Stabilize the rotation speed. Before implementing this measure, its feasibility and expected effects should be fully evaluated, and the plan details should be communicated and confirmed with relevant technical personnel. During implementation, key quality indicator changes should be closely monitored, and adjustment effects should be recorded and fed back in time to form reusable process experience. 3. Improve heating uniformity. 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. 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 「Streaks on the Product Surface」 problem can be attributed to the combined effects of multiple factors such as scratches on the mold surface and unstable rotation speed. To solve this problem, it is necessary to start from aspects such as polishing the mold surface and stabilizing the rotation speed 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.