Effective fast-response pressure control for thin-wall gas-assisted injection molding

Abstract

As compared with the traditional injection molding, gas-assisted injection molding (GAIM) exhibits more advantages such as requiring lower injection pressure, reducing part weight, minimizing residual stress, and improving part quality, etc. When GAIM is applied to thin-wall parts, the required filling time (usually less than 0.3 seconds) becomes a critical factor for successful molding. In this study, a new pressure control system that operates with much less response time than what most commercial gas-assisted units need was developed. The new control system consists of a fast interpolation device for fast approaching the set pressure and a fast-response pressure control valve incorporated with a PID controller to accelerate and fine-tune the steady output. To verify the effectiveness and performance of the proposed system, several experiments were conducted. The experimental results have shown that the proposed control system can effectively shorten the response time so that the filling time can be less than 0.3 s to provide good quality for the thin-wall injected products.