A study in injection molding dynamics

Self Cite

Because of its versatility, cost effectiveness, and ability to produce intricate shapes to tight specifications, the injection molding process is widely used in plastics processing. Mold cavity pressure plays an important role in determining the quality of the molded articles. The dynamic behavior and control of cavity pressure were studied for the filling and packing phases. The dynamics of cavity pressure during filling were investigated and found to be both nonlinear and time-varying in relation to the hydraulic servo-valve opening, which is the manipulated variable. A self-tuning control system was designed and tested for a wide range of conditions. The transition from filling to packing was best detected by the change in the derivative of cavity pressure. The dynamics of cavity pressure during packing were studied and modeled similarly as for filling. The self-tuning technique was successfully extended and implemented in the packing phase.

Section: Pressure Controlmentioning

confidence: 99%

Cavity pressure dynamics and self‐tuning control for filling and packing phases of thermoplastics injection molding

Gao

Patterson

Kamal

1996

Self Cite

“…The transducers for the measurement of the hydraulic and nozzle pressures were installed during a n earlier study (12). The screw RPM readings were taken from a tachometer installed on the screw shaft.…”

Section: Measured and Manipulated Variablesmentioning

confidence: 99%

“…The SSRs were interfaced to the front and rear zone heating elements and 220V, 60Hz power line (1 4). The manipulation of the servovalve opening was facilitated by a n interface to the microcomputer via a D/A converter constructed earlier [ 12).…”

Section: Measured and Manipulated Variablesmentioning

confidence: 99%

An injection molding study. Part I: Melt and barrel temperature dynamics

Kamal

Patterson

Gomes

1986

Self Cite

The dynamics of the key variables in the plastication phase of injection molding were studied using a microcomputer controlled laboratory scale injection molding machine. Interfaces for the measurement and manipulation of suitable variables were developed. An approximate theoretical analysis provided a preliminary understanding of the effect of a step input in heating power on melt and barrel temperatures. Deterministic and stochastic models were derived from experimental data for the melt and the front and rear zone barrel temperatures with heater power manipulation. Experiments were performed for evaluating the effects of back pressure manipulation, heating zone interaction, and process disturbances on the melt and barrel temperatures. Experiments showed that it is desirable to directly control the melt temperature rather than the barrel temperatures.

“…Models obtained in this approach are simple and linear in most cases. Kamal et al applied such techniques to model transient responses of a single screw extruder used for injection molding [25, 26]. These linear models can be used effectively to capture the behavior of highly nonlinear processes over a limited range of operation.…”

Section: Introductionmentioning

confidence: 99%

Identification of transient responses of a plasticating twin screw extruder due to excitation in feed rate

Iqbal

Sundararaj

Shah

2010

A corotating plasticating twin screw extruder (TSE) was excited by changing feed rate according to predesigned random binary sequence (RBS) and stair type excitation. A high density polyethylene was used as processing material in this study. Empirical models were developed relating two output variables, melt pressure at die (Pm), and melt temperature at die (Tm), with feed rate (F). Classical linear system identification technique was used to develop models. Models were developed using a data set obtained from RBS excitation. Stair type excitation data were used to validate the developed models. The structure of the obtained models was autoregressive moving average with exogenous input (ARMAX). Models with ARMAX structure and order of 2 were found to be sufficient to capture the dynamic behaviors of Pm and Tm when F was changed. A delay‐gain model was proposed for Pm and was found to capture the response quite satisfactorily. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers