Effect of melt viscoelastic characteristics on manufacturing precision of in⁃mold micro assembly molding

doi:10.19491/j.issn.1001-9278.2024.09.012

Abstract

Abstract:

Aiming at the functional self⁃lubricating liquid film assisted in⁃mold micro assembly molding of the micro universal spherical revolute motion pair， the key technical issue to achieve precise control of its manufacturing accuracy is to clarify the multi field collaborative coupling evolution law among the diameter manufacturing tolerance of the micro assembly interface， viscoelastic thermal fluid solid coupling impact load， the thickness of continuous phase transformation evolution zone， thermal viscoelastic plastic stress， and melt viscoelastic characteristics. The research results indicated that the diameter manufacturing tolerance of the micro assembly interface was controlled by the viscoelastic characteristics of the secondary injection molding melt. When the reference viscosity increased from 2 267 to 15 000 Pa·s， the diameter manufacturing tolerance of the micro assembly interface increased by 72.7 % from 11 to 19 μm. When the relaxation time increased from 0.05 to 0.25 s， the diameter manufacturing tolerance of the micro assembly interface decreased by 38.7 % from 31 to 19 μm. To meet the industry standard of dimensional manufacturing tolerance technical indicators ≤ 30 μm， it is not advisable to use a high elastic melt with a relaxation time ≤ 0.05 s for the functional self⁃lubricating liquid film assisted in⁃mold micro assembly molding.

Key words: universal direction spherical revolute kinematic pair, in?mold micro assembly molding, dimensional manufacturing tolerances, viscoelastic characteristics, simulation

CLC Number:

TQ320.66

FU Lingjie, XUE Peng, ZHOU Guofa. Effect of melt viscoelastic characteristics on manufacturing precision of in⁃mold micro assembly molding[J]. China Plastics, 2024, 38(9): 66-72.

Figures/Tables 16

Fig.1. Simulation method implementation flowchart

Fig.2. 3D solid model of motion pair

Fig.3. Schematic diagram of variable combination primary and secondary cavity structures

材料	$η$ / $P a ⋅ s$	$η r$	ξ	λ/s	β
PS	15 000	0.067	1.87	0.1	0.22

材料	$η$ / $P a ⋅ s$	$η r$	ξ	λ/s	β
PS	15 000	0.067	1.87	0.1	0.22

Tab.1. PTT model parameter of PS melt

Δ/K	E_g/MPa	E_r/MPa	X_E	T_g/K
1.7	300	1.4	0.003	388

Tab.2. Thermal viscoelastic modulus model （3） parameters of PMMA solid

材料回归参数变量名	变量值（ $T ≤ T g$ ）	变量值（ $T ≥ T r$ ）
σ₀	4 551.2	32.773
A₀₁	-11.23	0.052 24
B₀₁	-1 233.4	2 698.654
B₀₂	2 573.73	-3 656.2
B₀₃	-1 516.64	1 588.435
A₁	0.191 1	43.806
A₂	1.3×10^-3	-0.208 8
A₃	1.628×10^-6	2.595×10^-4
B₁	4.796 4	-637.165
B₂	-9.27	146.866

材料回归参数变量名	变量值（ $T ≤ T g$ ）	变量值（ $T ≥ T r$ ）
σ₀	4 551.2	32.773
A₀₁	-11.23	0.052 24
B₀₁	-1 233.4	2 698.654
B₀₂	2 573.73	-3 656.2
B₀₃	-1 516.64	1 588.435
A₁	0.191 1	43.806
A₂	1.3×10^-3	-0.208 8
A₃	1.628×10^-6	2.595×10^-4
B₁	4.796 4	-637.165
B₂	-9.27	146.866

Tab.3. Thermoplastic constitutive mode parameters of PMMA solid

Fig.4. Influence of melt viscoelastic properties on δC distribution

Fig.5. Micro assembly interfacial δCmax vs melt viscoelastic characteristic parameters

Fig.6. Extract path diagram

Fig.7. Influence of melt viscoelastic characteristics on distribution of diameter manufacturing tolerance for thermal fluid structure coupling deformation

参考黏度/Pa·s	考虑体积收缩直径制造尺寸公差/μm	松弛时间/ s	考虑体积收缩直径制造尺寸公差/μm
2 267	11	0.05	31
5 000	13	0.10	19
8 000	16	0.15	17
11 000	17	0.20	16
15 000	19	0.25	15

Tab.4. Influence of viscoelastic characteristics on diameter manufacturing tolerance of end product

Fig.8. Influence of melt viscoelastic characteristics on temperature field in phase transition evolution zone

Fig.9. Maximum thickness of phase transition evolution zone vs melt viscoelastic characteristics

Fig.10. Influence of melt viscoelastic characteristics on thermal fluid structure coupling pressure distribution

Fig.11. Influence of melt viscoelastic characteristics on thermal viscoelastic plastic normal stress distribution

Fig.12. Influence of melt viscoelastic characteristics on thermal viscous drag shear stress distribution

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