Electrostatic agglomeration of powder in the mold

In the rotational molding production process, the product exhibits the quality defect of "Electrostatic agglomeration of powder in the mold".The specific manifestation is The powder agglomerates together due to electrostatic action.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 Electrostatic agglomeration of powder in the mold 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. Static electricity generated by powder friction.Mechanical wear and loosening during long-term equipment operation will cause clearance changes, decreased accuracy and unstable operation, thereby triggering various process and quality problems.Establishing a regular inspection and preventive maintenance system for equipment operating status, and timely repairing or replacing worn parts, is a necessary measure to maintain equipment accuracy and process stability. 2. Dry environment.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. 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 Electrostatic agglomeration of powder in the mold through chain effects. 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 Electrostatic agglomeration of powder in the mold problem.

1. Treat the powder with an antistatic agent.Before introducing new tools, new materials or new methods, sufficient applicability evaluation and small-batch verification should be carried out.It is recommended to first conduct offline tests or simulation analyses outside production conditions, and introduce them into the formal production line only after confirming effectiveness and safety.Keep proper change management records to facilitate subsequent traceability and experience accumulation. 2. Increase ambient humidity.When implementing adjustments, it is recommended to use 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. Ground the mold.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. 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 "Electrostatic agglomeration of powder in the mold" problem can be attributed to the combined action of multiple factors such as Static electricity generated by powder friction, Dry environment.To solve this problem, it is necessary to start from aspects such as Treat the powder with an antistatic agent, Increase ambient humidity 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.