Influence of Film Heat Lag of In⁃mold Decoration on Molding Process

doi:10.19491/j.issn.1001-9278.2020.04.012

Abstract

Abstract:

In this paper, taking the in?mold decoration test plate as a research object, the influence factors of film heat?lag effect and the influence on the molding process were analyzed by simulation and experimental methods. The results indicated that the film heat?lag effect generated the hysteresis of temperature change for the moving mold side compared to the fixed mold side, and there was a maximum temperature difference of 8.6 °C under the experimental conditions. The film heat lag decreased with an increase of mold temperature, but increased with the increase of melt temperature and film thickness. The filling and cooling of the melt were influenced by the film, resulting in uneven cooling of the product. The heat?lag effect of the film led to an increase in warpage of the product.

Key words: in?mold decoration, film heat?lag, warpage

CLC Number:

TQ 325.1

Jinkun WANG, Zhenghua MENG, Wei GUO, Haosheng HU, Lei ZHOU. Influence of Film Heat Lag of In⁃mold Decoration on Molding Process[J]. China Plastics, 2020, 34(4): 70-77.

Figures/Tables 19

熔体温度/℃	模具温度/℃	注射压力/MPa	保压压力/MPa	保压时间/s	冷却时间/s
240	50	100	80	4	20

Tab.1. Injection molding process parameters

Fig.1. Overall mold structure

Fig.2. Cooling pipe layout diagram

Fig.3. Temperature field comparison of two kinds of molds

Fig.4. Temperature difference between the moving die side and the fixed one

参数	PC/ABS	PC
模具温度/℃	40、60、80	40 、60 、80
熔体温度/℃	230、250、270	270、290、310
保压压力/MPa	80	80
保压时间/s	3	3
注射时间/s	1.5	1.5
注射压力/MPa	100	100
冷却时间/s	20	20

Tab.2. Process parameters of the two material

Fig.5. Influence of mold temperature and melt temperature on film heat stagnation of PC and PC/ABS

材料名称	比热/kg·℃	导热系数/m·℃
PC/ABS	2 310	0.220
PC	2 100	0.214

Tab.3. Thermophysical properties of experimental materials

Fig.6. Comparison of rheological properties of PC and PC/ABS

Fig.7. Effect of film thickness on hysteresis temperature

Fig.8. Temperature field distribution close to the film, the mold and the melt at 4.4 s

Fig.9. Melt flow front during filling

Fig.10. Section of temperature field at temperature measurement points at 1.3 s

Fig.11. Temperature variation at the boundary

Fig.12. Diagram of temperature variation inside melt

Fig.13. Temperature difference between two sides of the melt

熔体

温度/℃

模具

温度/℃

注射时间/s

保压压力/MPa

保压时间/

冷却时间

240

1.5

Tab.4. Process parameter for warp analysis

Fig.14. Comparison of warp deformation under two processes

Fig.15. Warp deformation enlarged by 10 times

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