Warpage of microcellular foaming and in⁃mold decoration combined injection molding under asymmetric temperature field

doi:10.19491/j.issn.1001-9278.2021.12.011

Abstract

Abstract:

Taking the tensile test sample as an example， we investigated the effects of main process parameters on the warpage under molding condition of asymmetric temperature field in the process of microcellular foaming and in?mold decoration combined injection molding （MIM/IMD） using an orthogonal experimental design and flow simulation to obtain an optimal combination of process parameters with minimum warpage. The simulation results of four injection molding processes （MIM/IMD， IMD， MIM， CIM） were then compared in the directions of X， Y and Z axis， including the warpage variation in different directions of samples， cell size and density to explore the influence of the microporous structure and distribution on the warpage. The results indicated that the warpage reached the minimum and the warpage decreased by a maximum of 3.414 mm when the melt temperature， injection rate， filling/holding pressure （V/P） switch， supercritical N₂ concentration， and cooling time we set as 210 °C， 55 cm³/s， 98 %， 0.2 wt%， 40 s， respectively. The application of microcellular foaming technology in the injection molding process can facilitate to reduce the warpage of the molded products. The asymmetric temperature field made the cell size and density greater those that in the non?film side. Moreover， the temperature in the film side was also higher than that in the non?film side. This made the shrink of sample in the film side slower than that in the non?film side. As a result， the unbalanced warpage in both sides of the sample tended to concave and curl towards the non?film side.

Key words: injection molding, microcellular foaming, warpage under molding, warpage, asymmetric temperature field

CLC Number:

TQ320.66⁺2

YU Shengrui, ZOU Jiayong, LUO Jie, ZENG Yihe, LIU Guang, LING Yan, WANG Yunming, HAN Wen, ZHOU Huamin. Warpage of microcellular foaming and in⁃mold decoration combined injection molding under asymmetric temperature field[J]. China Plastics, 2021, 35(12): 63-69.

Figures/Tables 6

Fig.1. Tensile sample model

水平	A/s	B/°C	C/cm³·s^-1	D/%	E/%
1	10	210	10	86	0.2
2	20	220	25	90	0.5
3	30	230	40	94	0.8
4	40	240	55	98	1.1

Tab.1. Setting of molding conditions

试验号	翘曲变形量/mm	试验号	翘曲变形量/mm
1	5.251	9	4.068
2	4.865	10	3.956
3	4.896	11	6.680
4	5.512	12	6.119
5	4.877	13	4.593
6	5.822	14	5.140
7	5.169	15	3.588
8	5.867	16	6.440

Tab.2. Orthogonal test results

Fig.2. Warpage of different factors and levels

Fig.3. Warpage in different directions under four molding process conditions

Fig.4. Melt viscosity， temperature， cell distribution and temperatrue difference distribution of composite molding products on the MIM/IMD of microcellular foam mold

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