The Investigation of Novel Dynamic Packing Technology for Injection Molded Part Quality Control and Its Production Stability by Using Real-Time PVT Control Method

Abstract

Injection molding is an effective mass production process for plastic, partly due to a number of advantages such as complex shape moldability, material selectivity, and a rapid process cycle. However, highly labor-based conventional production restrains the development of the industry. Experience-driven molding setups are used to trial the mold process, and also for quality checking the molded part for mass production. There is no effective solution for maintaining the production stability and defect-free adjustment. This study aimed to establish scientific packing pressure setup technology to optimize the molded part quality and the stability of consecutive production. The dynamic packing pressure setup technology for molded part quality and the process stability were investigated. This not only achieves the optimization of the packing pressure setup, but the stabilization of quality in mass production. Four major qualities were discussed in this study including tensile strength, regional deviation on shrinkage, total shrinkage, and warpage. The qualities improved by up to 3.9%, 92.9%, 41.9%, and 9.2%, respectively. A series of pilot runs of 300 cycles for two packing pressure control methods were tested to investigate the stability of the qualities. Dynamic packing pressure control improved the weight replication by 54%, reduced total shrinkage by 23%, and improved the warpage by 12%.

Quality monitoring and control for plasticization of acrylonitrile‐butadiene‐styrene regrind polymer in injection molding

“…24 Recently, various quality control methodologies have been proposed based on the pressure-specific volume-temperature (pvT) behavior of the molten polymer estimated by sensing information within the cavity 25,26 and optimized the course to minimize the residual stress and hence reduce both the volumetric shrinkage and the warpage of injection-molded components. [27][28][29][30][31] However, the practicability still needs to be verified with more experiments. Moreover, their performance is degraded for thick-walled and complex-geometry components due to the significant differences in the pvT course between the skin and core layers, as well as between the near-gate and far-from-gate regions.…”

“…Despite potentially expensive characterization experiments, they also designed a controller that provided an online multivariate optimization of injection molding process based on a multi‐objective function 24 . Recently, various quality control methodologies have been proposed based on the pressure‐specific volume‐temperature (pvT) behavior of the molten polymer estimated by sensing information within the cavity 25,26 and optimized the course to minimize the residual stress and hence reduce both the volumetric shrinkage and the warpage of injection‐molded components 27–31 . However, the practicability still needs to be verified with more experiments.…”

Prediction of Part Shrinkage for Injection Molded Crystalline Polymer via Cavity Pressure and Melt Temperature Monitoring

“…Injection molding is a widely used process for mass production of plastic parts owing to its advantages, such as net shaping of complex geometry parts, allowing the use of various materials, and rapid production times. However, part quality can be influenced by numerous factors, such as material properties, mold design, part geometry, and processing conditions [1][2][3][4]. During the injection molding process, different parts of the molded material are subjected to various thermal-mechanical stresses due to disparities in pressure, temperature, shear stress, and other factors.…”

“…These variations form different pressure-temperature paths on the pressure-volume-temperature (PVT) diagram. If these paths cannot converge or meet at a common, specific volume value during ejection, they can lead to uneven shrinkage and warping [2][3][4]. Achieving high dimensional accuracy and defect-free parts is a challenge for molders in their daily operations since they rely heavily on their molding expertise to conduct mold trials.…”

“…These issues cause anisotropic properties and uneven shrinkage, which are difficult to solve. Previous research has focused on shrinkage issues based on PVT relationships [3][4][5][6][7][8][9][10]. The influence of factors such as cavity pressure, mold temperature, filling-to-packing switchover, and other factors on shrinkage has also been reported [11][12][13][14].…”