Mold resonance during rotation

In the rotational molding production process, the product exhibits the quality defect of "Mold resonance during rotation".The specific manifestation is The mold produces resonance vibration at a specific rotation speed.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 Mold resonance during rotation 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 rotation speed happens to reach the natural frequency of the mold-product system.Speed parameters affect the flow state and time allocation of the melt during the forming process.Too slow speed leads to premature cooling and insufficient filling; too fast speed causes melt fracture, air entrapment and shear overheating.Optimization of the speed curve should make the melt flow smoothly and orderly in the cavity. 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 Mold resonance during rotation through chain effects.

1. Avoid the resonance rotation speed range.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. Reinforce the mold support.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 rotation speed.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 "Mold resonance during rotation" problem can be attributed to the combined action of multiple factors such as The rotation speed happens to reach the natural frequency of the mold-product system.To solve this problem, it is necessary to start from aspects such as Avoid the resonance rotation speed range, Reinforce the mold support 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.