Rainbow patterns on the product surface (stress birefringence)

In the extrusion '2079851475616104457 production process, the product exhibits the quality defect of "Rainbow patterns on the product surface (stress birefringence)".The specific manifestation is Rainbow-colored interference fringes appear on the product wall under polarized light.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 Rainbow patterns on the product surface (stress birefringence) 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. Excessive internal residual stress.This factor causing the problem reflects that certain process conditions or material properties in extrusion '2079851475616104457 do not meet the optimal forming requirements.Such problems are often cumulative and concealed, and should be investigated and verified as key focus items during process debugging and finalization to ensure hidden dangers are eliminated at the source. 2. Uneven orientation.Uniformity runs through all stages of the forming process.Uneven temperature, uneven pressure distribution, uneven cooling and uneven material mixing all lead to discreteness in product quality.Ensuring the uniform distribution of physical quantities is a prerequisite for obtaining products with good consistency and stable quality. 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 Rainbow patterns on the product surface (stress birefringence) 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 Rainbow patterns on the product surface (stress birefringence) problem.

1. Optimize the blowing and cooling processes to reduce residual stress.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. Annealing treatment.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. It is recommended to formulate a preventive checklist for the Rainbow patterns on the product surface (stress birefringence) problem, incorporate parison wall thickness control and parison temperature uniformity into the daily inspection scope, 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 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 "Rainbow patterns on the product surface (stress birefringence)" problem can be attributed to the combined action of multiple factors such as Excessive internal residual stress, Uneven orientation.To solve this problem, it is necessary to start from aspects such as Optimize the blowing and cooling processes to reduce residual stress, Annealing treatment 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.