Real-time characterization of microcellular injection molding via ultrasonic technology

Microcellular injection molding (MIM) has been extensively used for producing foamed plastic parts. It has the advantage of material, energy, and cost savings, as well as enhanced dimensional stability. However, the in-situ characterization of MIM is still challenging. In this study, an ultrasonic method for the real-time characterization of MIM parts parameters-i.e., cell size, surface roughness, and skin layer thickness-during the MIM process is proposed. To the best of our knowledge, this is the first time that ultrasonic technology has been employed for the characterization of MIM. A series of experiments were performed to validate the proposed method. Experimental results showed that the duration process times of the ultrasonic signals and the change of the ultrasonic speed in the transducer path could be used to characterize the cell size and the skin layer thickness. The time delay of the first ultrasonic signal and the largest ultrasonic amplitude of the ultrasonic signals was employed to characterize the surface roughness. The proposed method has the advantages of being nondestructive, real-time, low-cost, and safe. As such, it has significant application prospects in MIM production.