Evaluation Method for the Reasonableness of Countermeasures for Defective Products in the Negative-Pressure Molding Mechanism

Abstract

We propose a new digital evaluation model for the negative-pressure molding mechanism, which is used to verify the feasibility of improvement measures for quality problem of the pad. The gas–solid flow in the negative pressure molding system facing the pad of diapers at the molding surface under different outlet pressures is studied using CFD-DEM bidirectional coupling simulation method. Aiming at the concentration of velocity/pressure values in the molding defect region, the uniformity coefficient is used as an important evaluation index to reflect the molding quality, and the parameters are optimised for the velocity and pressure uniformity of the gas phase in the molding defect region. For the fine flocculent discrete element, the parameter calibration is carried out, and the percentage of solid phase bearing at the screen is used as a reference index to further verify the feasibility of the improvement scheme. Finally, the model is applied to an improvement example, the results show that the molding defects of the cotton core layer are related to the velocity distribution of the molding surface. The molding quality can be significantly improved by setting a retaining ring at the outlet of the wind barn. The speed uniformity coefficient is improved by 44.2% when the retaining ring thickness s = 140 mm, inner diameter d = 1000 mm, and the relative position l = 0 mm. The molding quality has been significantly improved.