Flash on the Mold Parting Line

In the rotational molding production process, the product exhibits the quality defect of 「Flash on the Mold Parting Line」. The specific manifestation is that flash appears at the parting line. 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 Flash on the Mold Parting Line 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. Mold clamping surface not flat. 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. Insufficient clamping force of the fixture. 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. 3. Poor sealing of the clamping surface. 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 Flash on the Mold Parting Line problem.

1. Repair the clamping 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. Increase the clamping force of the fixture. 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. Use high-temperature-resistant sealing materials. Before introducing new tools, new materials, or new methods, adequate applicability evaluation 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. Make good change management records to facilitate subsequent traceability and experience accumulation. 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 「Flash on the Mold Parting Line」 problem can be attributed to the combined effects of multiple factors such as the mold clamping surface not being flat and insufficient clamping force of the fixture. To solve this problem, it is necessary to start from aspects such as repairing the clamping surface and increasing the clamping force of the fixture 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.