A Comparison of Numerical and Actual Measurements of Large-Scale Rib-Structured Pallet Flatness Using Recycled Polypropylene in Injection Molding

Abstract

Many challenges are associated with the injection molding process for forming a rib-structured pallet (1100 mm × 1100 mm × 140 mm, length × width × height) because greater flowing resistance through the rib channels within the pallet can induce insufficient filling. Essentially, multi-gate filling involves a sequential valve gate system, which helps to spread the filling front with fewer weld lines. Based on the presetting of the sequential scheme of the valve gates, actual measurements of pallet flatness using the ATOS scan system were compared to numerical warpage measurements of a pallet derived by Moldex3D 2020. In this study, we propose a sequential scheme by actuating the valve gates to open once the flow front spreads towards them; then, actual warpage measurements of a pallet are compared with numerical measurements. The results show that the warpage of the top surface of the pallet is 5.144 mm in actual measurements and 5.729 mm in simulation. The results all indicated small warpage with respect to the pallet size. The simulation and actual measurements of flatness are in excellent agreement; the difference in top flatness between the simulated and actual pallet is 0.59 mm, while the bottom flatness difference is 0.035 mm. By adjusting the cooling water temperature, increasing the mold temperature, and decreasing the material temperature, overall flatness and warpage displacement can be reduced.

Filling-Balance-Oriented Parameters for Multi-Cavity Molds in Polyvinyl Chloride Injection Molding

“…However, the ranges of the melt temperature and filling rate in PVC injection molding are limited due to PVC degradation [6]. Under the real settings of the machine specifications, simulations by molding flow software have been successfully implemented to derive molding parameters for practical operations [7][8][9][10][11]. To avoid PVC degradation during injection molding, simulations may also help to construct a successful set of parameters to enhance the molding efficiency by examining the temperature distribution of the cavity during the filling stage [12].…”

“…Filling imbalance can also lead the firstly filled cavity to an over-packing situation [7]. The short-shot technique by an empirical approach [10,11] can reveal filling imbalance. Based on the revealed results, the sizes of the runners and/or gates of the mold can be changed using machine tools via a traditional trial-and-error approach.…”