Product flash blown out from mold vent holes

In the extrusion '2079851475616104457 production process, the product exhibits the quality defect of "Product flash blown out from mold vent holes".The specific manifestation is Small flash protrusions appear at the vent holes.This defect is more common when processing materials such as HDPE, PP, PVC and PC, and its occurrence is usually related to unreasonable settings of melt temperature, extrusion speed, blowing pressure and mold temperature.When the Product flash blown out from mold vent holes situation is severe, it will cause a series of chain quality defects in the product's appearance, dimensional accuracy, mechanical properties and other aspects, which not only reduces the product's functionality and safety in use, but also directly increases the scrap rate and production cost.Therefore, this problem requires systematic diagnosis and optimization from multiple dimensions such as material selection, the status of the extruder, head, die, mold clamping mechanism and blowing system, and melt temperature, extrusion speed, blowing pressure and mold temperature.

1. Vent holes too large or too deep.Mold venting is a basic condition for ensuring smooth melt filling.When venting is poor, the air in the cavity is compressed to form a high-pressure air cushion, hindering melt flow and causing problems such as short shots, burning and weld lines.Reasonable venting design should consider vent positions and vent clearances to ensure air is discharged in time. 2. Excessive blowing pressure.Pressure directly determines the filling capacity of the melt and the mold-contacting effect during the forming process.Insufficient pressure results in incomplete filling and poor replication accuracy; excessive pressure may cause secondary defects such as flash and excessive internal stress.The pressure setting should comprehensively consider factors such as material viscosity, product size and mold structure. In addition, the insufficient overall coordination of parison wall thickness control and parison temperature uniformity is also a factor that cannot be ignored; there are complex interactions and coupling relationships among the process parameters, and the deviation of any parameter may aggravate the degree of Product flash blown out from mold vent holes through chain effects. In terms of equipment maintenance, the regular overhaul and accuracy confirmation of the extruder, head, die, mold clamping mechanism and blowing system 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 Product flash blown out from mold vent holes problem.

1. Reduce the vent hole size.Adjustments should follow the principle of gradual progress; each adjustment should not be too large, and a decrement of 5%~15% of the current value is recommended.After each adjustment, stably observe the product quality changes for at least 5~10 mold cycles, and continue adjusting only after confirming the improvement direction is correct; never make excessive one-step adjustments. 2. Reduce the blowing pressure.Adjustments should follow the principle of gradual progress; each adjustment should not be too large, and a decrement of 5%~15% of the current value is recommended.After each adjustment, stably observe the product quality changes for at least 5~10 mold cycles, and continue adjusting only after confirming the improvement direction is correct; never make excessive one-step adjustments. 3. Switch to sintered metal vent inserts.Before implementing this measure, its feasibility and expected effects should be fully evaluated, plan details communicated and confirmed with relevant technical personnel, key quality indicator changes closely monitored during implementation, adjustment effects recorded and fed back in a timely manner, forming reusable process experience. In terms of material management, incoming inspection of raw materials and in-process testing of work-in-progress should be strengthened, and key performance indicators of HDPE, PP, PVC and PC should be strictly controlled to ensure the stability of forming quality from the source.

In summary, the causes of the "Product flash blown out from mold vent holes" problem can be attributed to the combined action of multiple factors such as Vent holes too large or too deep, Excessive blowing pressure.To solve this problem, it is necessary to start from aspects such as Reduce the vent hole size, Reduce the blowing pressure and take 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.