The Influence of Processing Parameters on Thin-Wall Gas Assisted Injection Molding of Thermoplastic Materials

Abstract

Thin-wall gas assisted injection molding of thermoplastics has become an important process in industry because of its light weight, relatively lower resin cost per part, and faster cycle time. This report is devoted to investigate the effects of different processing parameters on the length of gas penetration in thinwall gas assisted injection molded parts. The first part of this report is to find ways to optimize the gas penetration of molded parts. An L'18 experimental matrix design based on the Taguchi method was conducted to investigate the processing parameters that affect the length of gas penetration in thin-wall gas assisted injection molded parts. The second part of this report is to identify the relative significance of each processing parameter on the gas penetration of molded products. Two materials were used in the study: an amorphous acrylonitrile-butadiene-styrene (ABS), and a semi-crystalline polypropylene (PP). Experiments were carried out on an 80-ton reciprocating injection molding machine equipped with a high pressure gas injection unit. A plate cavity of various thicknesses (0.6, 1.2 and 2.0 mm) with a gas channel across the center was used for the experiments. After molding, the length of gas penetration in the molded parts was determined. For ABS materials, melt temperature and gas pressure were found to be the principal parameters affecting the thin-wall gas assisted injection molded parts, while for PP materials, the gas pressure and gas injection delay time were found to be the key processing parameters. In addition, warpage of molded parts was found to decrease with the length of gas penetration.

Effect of Melt and Mold Temperatures on the Solidification Behavior of HDPE during Gas‐Assisted Injection Molding: An Enthalpy Transformation Approach

“…[18][19][20] As is well known, investigations on the solidification/crystallization phenomena under real cooling conditions could contribute to the optimization of thermal or pressure history during molding process and the studies of microstructure evolution, [21][22][23] and the cooling stage also accounts for a large portion of the whole GAIM cycle, as shown in Figure 1. However, studies on the transient heat transfer with phase-change effects, which may heavily affect the formation of hierarchical structures [especially for crystalline polymers, such as high-density polyethylene (HDPE), poly(propylene) (PP), etc.…”

A Study of Taguchi and Design of Experiments Method in Injection Molding Process for Polypropylene Components

“…The Taguchi method combines the effects of each noise factor and calculates a signal-to-noise ratio (S/N ratio) for each experiment. The Taguchi method has been used successfully in several industrial applications, such as manufacturing processes, mechanical component designs, and process optimizations [7][8][9][10][11].…”

“…The product quality produced by the injection molding is always affected by the process parameters, including the cooling time, the injection pressure, the injection speed, the filling time, the melting temperature, the ejecting pressure, the molding temperature, the packing pressure, the geometric shape of the mold, material properties of the melting molds, the melting speed, and the heat transfer action of flow field, etc. The influences of the injection molding variables (conditions) on the physical and mechanical properties of thermoplastics have been studied by researchers [1,5,6,9,14,17]. For a preliminary study, the injection molding parameters were simulated by C-MOLD Õ software to identify some crucial settings.…”

Numerical and Experimental Study on the Injection Moulding of a Thin-Wall Complex Part

“…8. At the melt temperature of 190°C, for the cavity pressure, the simulation showed that the effect of pressure on the specific volume is the most important factor to predict the peak cavity pressure [15,16]. The pressure drops more rapidly when the melt temperature is lower because the melt cools down more rapidly.…”