Control-oriented modeling of servo-pump driven injection molding machines in the filling and packing phase

Abstract

Servo-valves or variable displacement pumps are typically used to control conventional hydraulic injection molding machines (IMMs). Recent developments in electrical drive technology allow to utilize servo-motor driven pumps instead, which is beneficial due to their higher energy efficiency. Their dynamic behavior, however, is significantly different compared to the conventional setup. Thus, currently used mathematical models and control concepts cannot be directly applied. This paper presents a computationally efficient and scalable mathematical model of the injection process for these servo-pump driven IMMs. A first-principles model of the injection machine is combined with a phenomenological model describing the injection process, i.e. the compression of the melt and the polymer flow into the mold. The proposed model is tailored to real-time applications and serves as an ideal basis for the design of model-based control strategies. The feasibility of the proposed model is demonstrated by a number of different experiments. They confirm a high model accuracy over the whole operating range for different mold geometries. ARTICLE HISTORY

Development and Validation of a 1D Dynamic Model of an Injection Moulding Process and Design of a Model-Based Nozzle Pressure Controller

“…Modelling and control of the moulding process is an area that has been of interest for several decades; more-general literature reviews can be found in [8,16,17]. Early work with simulation of the injection moulding process started in the 1950s, when Spencer and Gilmore [18] investigated the filling phase.…”

“…These programs analyse the behaviour of the dynamic system through a meshing, which introduces a large set of equations. The computational demands of these models, coupled with their emphasis on spatial distribution rather than dynamic behaviour, render these methods impractical for control design purposes [17].…”

Optimal Robust Tracking Control of Injection Velocity in an Injection Molding Machine

“…The development of related technologies, such as plastic molding, will have a profound impact on the competitiveness of the discrete manufacturing industry in the future and will also have an important radiative impact on the industrial sector. Therefore, the intelligent automation of various IMMs has become a hotspot in the study of discrete industrial manufacturing [9][10][11][12][13][14][15][16][17][18][19]. Recent years have seen a large number of pertinent studies on control and optimization methods for the temperature, pressure, and injection velocity in various IMMs [20][21][22][23][24][25][26][27][28][29][30][31][32][33].…”

Cycle‐based Adaption of a Model‐Predictive Control Strategy for Injection Molding Machines

“…It comprises a barrel filled with polymer and a screw, which can be rotated and positioned in this barrel. It is based on a detailed mathematical model of the system [4] and utilizes penalty functions to account for the system constraints. The cyclic production process can be divided into the following main phases: (i) In the injection phase, the liquid polymer is injected through the nozzle into the mold by moving the screw in negative x s direction.…”