Rainbow interference patterns on the product surface (thin-film interference)

In the rotational molding production process, the product exhibits the quality defect of "Rainbow interference patterns on the product surface (thin-film interference)".The specific manifestation is Rainbow-colored interference fringes appear on the product surface.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 Rainbow interference patterns on the product surface (thin-film interference) 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. The release agent forms a non-uniform film on the surface producing optical interference.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 powder melting uniformity and product wall thickness control 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 interference patterns on the product surface (thin-film interference) through chain effects.

1. Apply the release agent uniformly and thinly.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. 2. Change the type of release agent.When replacing parts, original manufacturer spare parts of the same or higher specification should be selected to ensure installation accuracy and fit tolerances meet equipment technical requirements.After replacement, relevant parameters need to be recalibrated and trial runs conducted to verify the effect; normal production can only be resumed after confirming expectations are met.It is recommended to establish a spare parts life cycle management ledger. It is recommended to formulate a preventive checklist for the Rainbow interference patterns on the product surface (thin-film interference) problem, incorporate powder melting uniformity and product wall thickness control 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 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 "Rainbow interference patterns on the product surface (thin-film interference)" problem can be attributed to the combined action of multiple factors such as The release agent forms a non-uniform film on the surface producing optical interference.To solve this problem, it is necessary to start from aspects such as Apply the release agent uniformly and thinly, Change the type of release agent 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.