Interlayer separation within the product wall (multiple-feed process)

In the rotational molding production process, the product exhibits the quality defect of "Interlayer separation within the product wall (multiple-feed process)".The specific manifestation is Separation occurs between the layers of the multiple-feed product.This defect is more common when processing materials such as LLDPE, HDPE, PVC and PA powders, and its occurrence is usually related to unreasonable settings of heating temperature and time, rotation speed ratio, cooling rate and mold wall thickness.When the Interlayer separation within the product wall (multiple-feed process) 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 rotational molding machine, heating oven, rotating arm and cooling station, and heating temperature and time, rotation speed ratio, cooling rate and mold wall thickness.

1. Mismatched interlayer sintering temperatures.Temperature is the core factor affecting melt fluidity and viscosity.Excessively high temperature settings will cause decreased melt viscosity, insufficient melt strength and even thermal degradation; excessively low temperature results in poor melt fluidity and insufficient plasticization, making smooth filling or forming impossible.A reasonable temperature window should be optimally determined within the recommended range according to the melting characteristics and thermal stability of the material. 2. Insufficient interlayer bonding force.This factor causing the problem reflects that certain process conditions or material properties in rotational molding 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. 3. Contamination between layers.The mixing of foreign matter will destroy the homogeneity of the melt, causing defects such as spots, voids and stress concentration in the product.These foreign matters may come from the raw material itself, residues in regrind, equipment material accumulation falling off, or pollutants in the production environment.Strengthening raw material purification management and equipment cleaning is the key to preventing foreign matter from mixing in. 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 Interlayer separation within the product wall (multiple-feed process) problem.

1. Optimize the sintering process of each layer.Optimization work must be based on accurate diagnosis of the root cause of the problem; blind attempts must be avoided.It is recommended to first determine the key influencing factors and their interactions through process DOE test methods or historical production data analysis, and then carry out targeted parameter optimization and structural improvement to achieve twice the result with half the effort. 2. Ensure the interlayer interface is clean.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. 3. Adjust the interlayer feeding time.Optimization work must be based on accurate diagnosis of the root cause of the problem; blind attempts must be avoided.It is recommended to first determine the key influencing factors and their interactions through process DOE test methods or historical production data analysis, and then carry out targeted parameter optimization and structural improvement to achieve twice the result with half the effort. 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 LLDPE, HDPE, PVC and PA powders should be strictly controlled to ensure the stability of forming quality from the source.

In summary, the causes of the "Interlayer separation within the product wall (multiple-feed process)" problem can be attributed to the combined action of multiple factors such as Mismatched interlayer sintering temperatures, Insufficient interlayer bonding force.To solve this problem, it is necessary to start from aspects such as Optimize the sintering process of each layer, Ensure the interlayer interface is clean 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 powder melting uniformity and product wall thickness control.