Tie-Bar Elongation Based Filling-To-Packing Switchover Control and Prediction of Injection Molding Quality

Abstract

Filling-to-packing switchover (also called V/P switchover) is critical for assuring injection molding quality. An improper V/P switchover setting may result in various defects of injection-molded parts, such as excessive residual stress, flash, short shot, and warpage, etc. To enhance a consistent molding quality, recent V/P switchover approaches adopt cavity pressure profiles requiring sensors embedded in mold cavities, which is invasive to mold cavities and more expensive. Instead of using cavity pressure sensors, by working with the most popular screw position switchover control, this study hereby proposes a novel approach of tuning V/P switchover timing using a tie-bar elongation profile. In this investigation, a dumbbell testing specimen mold is applied to verify the feasibility of the method proposed. The results show that the mold filling and packing stages can be observed along the tie-bar elongation profile, detected by mounting strain gauges on the tie bars. Also, the characteristics of the cavity pressure are similar to those of the tie-bar elongation profile under a proper clamping force condition. Moreover, the varying process parameter settings which include injection speed, V/P switchover point, and holding pressure, can be reflected in these profiles. By extracting their characteristics, the application of the V/P switchover is proved to be realistic. This research conducted an experiment to verify the proposed V/P switchover decision method based on the tie-bar elongation profile. The result showed that the fluctuation of the part’s weight corresponding to a slight change of the barrel’s temperature from 210 °C to 215 °C can be successfully controlled with this method. Besides, the maximum clamping force increment extracted from the tie-bar elongation profile was found to be a good indicator for online monitoring of the reground material variation.

A Simple Method of Reducing Coolant Leakage for Direct Metal Printed Injection Mold with Conformal Cooling Channels Using General Process Parameters and Heat Treatment

“…The cooling times of the wax patterns fabricated by the injection mold with and without coolant leakage were 22 s and 39 s, respectively. Note that a distinct defect of the molded wax pattern, named short shot (an incompletely filled mold cavity [ 18 , 19 ]), was observed when the mold had coolant leakage. In this study, injection molds were fabricated by a hexagonal scanning strategy because it provides a regular arrangement of pores inside the injection mold.…”

Increasing the Sustainability of the Hybrid Mold Technique through Combined Insert Polymeric Material and Additive Manufacturing Method Design

“…In Moldex3D, the injection pressure is defined at the melt entrance into the injection molding set-up, thus the sprue entrance. After filling, the compression phase starts as part of the holding phase, in which the pressure peaks up to the highest values of the injection cycle and therefore has the greatest impact on the necessary clamping force [41].…”

Quality Classification of Injection-Molded Components by Using Quality Indices, Grading, and Machine Learning

“…Although the cost of installing cavity sensors in production systems is higher than the cost of using machine profiles, the use of cavity profiles helps to reduce prediction errors [ 9 , 10 ]. A high correlation exists between part quality and features extracted from cavity pressure curves [ 11 , 12 ]. In addition, quality indices can help to rapidly determine the quality of parts without the need for any measuring equipment, a process that is feasible for quality control in actual injection molding operations.…”