Real‐time diagnosis of co‐injection molding using ultrasound

Abstract

Co‐injection molding, also known as sandwich molding, is a process in which two or more polymers are laminated together in a mold cavity. Integrated ultrasonic sensors embedded into a mold insert of a co‐injection‐molding machine have been used for real‐time, nonintrusive, and nondestructive diagnosis of co‐injection‐molding processes. Diagnosis of core arrival, core flow speed, part solidification, part detachment from the mold, thickness of skin and core, and core length at the mold was demonstrated. It is found that core flow speed and peak cavity pressure monotonically increased and decreased with the core volume percentage, respectively. Thicknesses of the skin and core of the molded part were estimated using the presented ultrasonic technique during molding with an accuracy better than ±17%. In addition, the core length had correlation with core thickness, core flow speed, and peak cavity pressure. Among them, the core thickness measured by the ultrasonic technique had the better correlation. This technique enables process optimization, the maximum process efficiency, and in‐process quality assurance of the molded parts. POLYM. ENG. SCI., 47:1491–1500, 2007. © 2007 Society of Plastics Engineers

Nondestructive measurement of layer thickness in water‐assisted coinjection‐molded product by ultrasonic technology

“…In WACIM, the thickness of the layer walls significantly affects the mechanical properties of molded products and is an important factor in judging the quality of the products . Many studies have been conducted to investigate the thickness and distribution of residual walls of the products . Kuang et al .…”

“…applied an ultrasound sensor system for real‐time diagnosis of water‐ and gas‐assisted injection molding. Cheng et al . employed ultrasound for an online diagnosis of a coinjection molding process.…”

Correlation between runner pressure and cavity pressure within injection mold

“…For example, the process parameters are corrected by monitoring the cavity pressure in order to reduce shrinkage and warpage resulting from residual stress inside the plastic parts [1][2][3]. There are many methods of monitoring the physical quantities inside a cavity during the process, including measuring the melt flow front [4][5][6][7][8][9], mold heat flux [10,11], mold temperature [11][12][13][14][15], cavity pressure/ temperature [1,2,[14][15][16][17][18][19][20][21][22][23], and dimensions and properties of the molded part [3,[24][25][26][27]. The sensor types include the frequently used contact type, noncontact type [28][29][30][31], and even a wireless type of sensor [32][33][34][35][36].…”

Co‐injection molding of immiscible polymers: Skin‐core structure and adhesion studies

“…Monitoring and recording the cavity pressure change in real time is helpful to study the rheological behavior of the molten plastic during co‐injection molding and, thus, understanding how material is distributing inside the mold. Controlling cavity pressure to follow desired trajectories has been the subject of study of many researchers [12–17].…”