High internal stress in the preform

In the stretch '2079851475616104457 production process, the product exhibits the quality defect of "High internal stress in the preform". The specific manifestation is that the residual stress of the preform is large, affecting '2079851475616104457 quality. This defect is relatively common when processing materials such as PET, PP, PC, and its occurrence conditions are usually related to the unreasonable settings of stretching temperature, stretch ratio, blowing pressure, and preform heating uniformity. When the "High internal stress in the preform" situation is severe, it will cause a series of chain quality defects in the product in terms of appearance, dimensional accuracy, mechanical properties, etc., which not only reduces the functionality and safety of the product 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 stretch '2079851475616104457 machine, heating oven, stretch rod, and blow mold, and stretching temperature, stretch ratio, blowing pressure, and preform heating uniformity.

1. Injection pressure too high. Pressure directly determines the filling ability of the melt during the forming process and the effect of conforming to the mold. 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 dimensions, and mold structure. 2. Holding pressure time too long. This factor causing the problem reflects that certain process conditions or material characteristics in stretch blow '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 at the source. 3. Cooling too fast. Cooling conditions determine the setting process of the product and its final internal structure. Uneven cooling causes shrinkage differences and residual stress, leading to warpage and dimensional deviation; insufficient cooling makes the product not rigid enough at demolding; overly rapid cooling generates large internal stress. The cooling system design should ensure uniform and efficient heat dissipation in all parts. In terms of equipment maintenance, the regular overhaul and precision confirmation of the stretch '2079851475616104457 machine, heating oven, stretch rod, and blow mold are not in place, causing the actual operating parameters of the equipment to deviate from the process requirements, which will also become a potential inducement of the "High internal stress in the preform" problem.

1. Reduce the injection and holding pressure. Adjustments should follow the principle of gradual progress; the amplitude of each adjustment should not be too large, and it is recommended to decrease by 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; avoid one-step excessive adjustment. 2. Extend the cooling time. 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 simultaneous changes of multiple parameters making the cause of the problem 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 mold cycles to observe the effect. 3. Optimize the injection process. Optimization work must be based on an accurate diagnosis of the root cause of the problem, and blind attempts must be avoided. It is recommended to first determine the key influencing factors and their interactions through the process DOE test method or historical production data analysis, and then carry out parameter optimization and structural improvement in a targeted manner to achieve twice the result with half the effort. In terms of material management, incoming inspection of raw materials upon arrival and in-process inspection of work-in-progress should be strengthened, and the key performance indicators of PET, PP, PC should be strictly controlled to ensure the stability of molding quality from the source.

In summary, the causes of the "High internal stress in the preform" problem can be attributed to the combined action of multiple factors such as Injection pressure too high, Holding pressure time too long. Solving this problem requires starting from aspects such as Reduce the injection and holding pressure, Extend the cooling time and adopting systematic governance 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 preform heating uniformity and biaxial stretch orientation control.