Flash at the mold parting line

During the extrusion '2079851475616104457 production process, the product exhibits the quality defect of "Flash at the mold parting line". Specifically manifested as obvious flash appearing at the parting line. This defect is relatively common when processing materials such as HDPE, PP, PVC, and PC, and its occurrence conditions are usually related to unreasonable settings of melt temperature, extrusion speed, blowing air pressure, and mold temperature. When the Flash at the mold parting line situation is severe, it will cause a series of chain-reaction quality defects in the product in terms of appearance, dimensional accuracy, mechanical properties, etc., which not only reduces the usability and safety of the product, but also directly increases the scrap rate and production cost. Therefore, this problem requires systematic diagnosis and optimization from multiple dimensions, including material selection, the condition of the extruder, die head, die, mold clamping mechanism, and blowing system, as well as melt temperature, extrusion speed, blowing air pressure, and mold temperature.

1. Insufficient mold clamping force. This factor leading to the problem reflects that certain process conditions or material properties in extrusion blow '2079851475616104453ing have not met the optimal molding requirements. Such problems often have cumulative and hidden characteristics, 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. Wear of the mold parting surface. The mold is the core tool that imparts shape and surface quality to the product. Unreasonable mold design, such as improper runner/gate dimensions, insufficient venting, inadequate draft angle, etc., will directly cause molding defects. The machining accuracy, surface treatment quality, and daily maintenance condition of the mold also directly affect product quality. 3. Parison too large. This factor leading to the problem reflects that certain process conditions or material properties in extrusion blow '2079851475616104453ing have not met the optimal molding requirements. Such problems often have cumulative and hidden characteristics, 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, inadequate regular overhaul and accuracy confirmation of the extruder, die head, die, mold clamping mechanism, and blowing system cause the actual operating parameters of the equipment to deviate from the process requirements, which can also become a potential inducement of the Flash at the mold parting line problem.

1. Increase the mold clamping force. When implementing adjustments, it is recommended to adopt the single-factor variable method, adjusting only one parameter at a time and fully evaluating the effect, to avoid multiple parameters changing simultaneously making the cause of the problem untraceable. The adjustment magnitude 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 mold cycles to observe the effect. 2. Repair and finish the mold parting surface. The polishing operation should proceed step by step from coarse to fine; each time a finer abrasive is used, the polishing direction should be changed to eliminate the texture marks of the previous step. The final surface roughness should be tested with a roughness meter to confirm that it meets the standard. After polishing is completed, it should be thoroughly cleaned to remove residues of abrasives and grinding agents to prevent them from entering the melt and contaminating the product. 3. Reduce the parison diameter. Adjustments should follow the principle of gradual progress; the magnitude of each adjustment should not be too large, and it is recommended to decrease in steps of 5%~15% of the current value. After each adjustment, observe the product quality changes stably for at least 5~10 mold cycles, and continue adjusting only after confirming that the improvement direction is correct; one-step excessive adjustment must be avoided. In terms of material management, incoming inspection of raw materials and in-process inspection of work-in-progress should be strengthened, and the key performance indicators of HDPE, PP, PVC, and PC should be strictly controlled to ensure the stability of molding quality from the source.

In summary, the causes of the "Flash at the mold parting line" problem can be attributed to the combined action of multiple factors such as insufficient mold clamping force and wear of the mold parting surface. Solving this problem requires starting from aspects such as increase the mold clamping force and repair and finish the mold parting surface, and adopting systematic governance measures. In actual production, it is recommended to establish a prevention and rapid response mechanism for this problem, achieving stable production and continuous improvement through parison wall thickness control and parison temperature uniformity.