# US 2014/0156237 A1 · Predicting Shrinkage of Injection Molded Products with Viscoelastic Characteristic

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- Number: US 2014/0156237 A1
- Document ID: US20140156237A1
- Status: Published application
- Kind: A1
- Application number: 14/091,756
- Filed: 2013-11-27
- Published: 2014-06-05
- Earliest claimed: 2012-12-03
- Assignees: Coretech System Co., Ltd.
- Applicants: Coretech System Co., Ltd.
- Inventors: Rong Yeu CHANG; Chia Hsiang HSU; Hsien Sen CHIU; Shih Po SUN; Chen Chieh WANG; Huan Chang TSENG
- Web page: https://patentgrep.com/patent/US20140156237A1

## CPC

- B29C 45/7693: {using rheological models of the material in the mould, e.g. finite elements method}
- G06F 30/20: Design optimisation, verification or simulation (optimisation, verification or simulation of circuit designs G06F30/30)
- G06F 30/23: using finite element methods [FEM] or finite difference methods [FDM]
- G06F 30/28: using fluid dynamics, e.g. using Navier-Stokes equations or computational fluid dynamics [CFD]
- B29C 2945/7605: Viscosity
- B29C 2945/76103: shrinkage, dilation, dimensional change, warpage
- B29C 2945/76588: shrinkage, dilation, dimensional change, warpage
- G06F 2111/10: Numerical modelling
- G06F 2113/22: Moulding
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

A computer-implemented method and non-transitory computer medium for calculating a shrinkage of a molding product comprises a step of using a computer processor to calculate a molding pressure of a molding fluid in a molding cavity by taking into consideration an increase of a shear viscosity of the molding fluid by a decrease of a shear rate, and a step of calculating the shrinkage of the molding products by taking into consideration a variation of a specific volume of the molding fluid as the molding pressure and a molding temperature decrease.

## Claims

### Claim 1

A computer-implemented method for calculating a shrinkage of a molding product, comprising a step of using a computer processor to calculate the shrinkage of the molding product from a molding fluid by taking into consideration an increase of a shear viscosity of the molding fluid by a decrease of a shear rate.

### Claim 2 (depends on 1)

The computer-implemented method according to claim 1, wherein the increase of the shear viscosity by the decrease of the shear rate describes an elastic characteristic of the molding fluid.

### Claim 3 (depends on 1)

The computer-implemented method according to claim 1, wherein the increase of the shear viscosity of the molding fluid by the decrease of the shear rate is represented using an expression:
ηVE(P,{dot over (γ)})=exp(b({dot over (γ)})P);
where ηVE represents the increase of the shear viscosity, {dot over (γ)} represents the shear rate, P represents a molding pressure, and b({dot over (γ)}) represents the shear rate.

### Claim 4 (depends on 3)

The computer-implemented method according to claim 3, wherein the shear rate is represented using an expression:
b

(
γ
.
)
=
∑
n
=
1
N


c
n

exp

(
-
γ
.
/
t
n
)
;
where cn and tn are constants.

### Claim 5 (depends on 1)

The computer-implemented method according to claim 1, wherein the shear viscosity of the molding fluid is represented using an expression:
η
=
η
0
VE
1
+
(
η
0
VE

γ
.
τ
*
)
1
-
n
;
η
0
VE
=
η
0

(
T
,
P
)

η
VE

(
P
,
γ
.
)
;
where η represents the shear viscosity, {dot over (γ)} represents the shear rate, P represents a molding pressure, T represents a molding temperature, n and τ* represent constants, and ηVE(P,{dot over (γ)}) represents the increase of the shear viscosity of the molding fluid by the decrease of the shear rate.

### Claim 6 (depends on 5)

The computer-implemented method according to claim 5, wherein the increase of the shear viscosity of the molding fluid by the decrease of the shear rate is represented using an expression:
ηVE(P,{dot over (γ)})=exp(b({dot over (γ)})P);
where ηVE represents the increase of the shear viscosity, {dot over (γ)} represents the shear rate, P represents a molding pressure, and b({dot over (γ)}) represents the shear rate.

### Claim 7 (depends on 6)

The computer-implemented method according to claim 6, wherein the shear rate is represented using an expression:
b

(
γ
.
)
=
∑
n
=
1
N


c
n

exp

(
-
γ
.
/
t
n
)
;
where cn and tn are constants.

### Claim 8 (depends on 1)

The computer-implemented method according to claim 1, further comprises a step of calculating a molding pressure of the molding fluid in a molding cavity by taking into consideration the increase of the shear viscosity of the molding fluid by the decrease of the shear rate.

### Claim 9 (depends on 8)

The computer-implemented method according to claim 8, further comprises a step of calculating the shrinkage of the molding products by taking into consideration a variation of a specific volume of the molding fluid as the molding pressure decreases.

### Claim 10 (depends on 9)

The computer-implemented method according to claim 9, wherein the calculating of the shrinkage further takes into consideration the variation of the specific volume of the molding fluid as a molding temperature decreases.

### Claim 11 (depends on 10)

The computer-implemented method according to claim 10, wherein the calculating of the shrinkage further takes into consideration the variation of the specific volume on different parts of the molding fluid.

### Claim 12

A non-transitory computer medium containing computer instructions stored therein for causing a computer processor to perform operations for calculating a shrinkage of a molding product, the operations comprising a step of calculating the shrinkage of the molding product from a molding fluid by taking into consideration an increase of a shear viscosity of the molding fluid by a decrease of a shear rate.

### Claim 13 (depends on 12)

The non-transitory computer medium according to claim 12, wherein the increase of the shear viscosity by the decrease of the shear rate describes an elastic characteristic of the molding fluid.

### Claim 14 (depends on 12)

The non-transitory computer medium according to claim 12, wherein the increase of the shear viscosity of the molding fluid by the decrease of the shear rate is represented using an expression:
ηVE(P,{dot over (γ)})=exp(b({dot over (γ)})P);
where ηVE represents the increase of the shear viscosity, {dot over (γ)} represents the shear rate, P represents a molding pressure, and b({dot over (γ)}) represents the shear rate.

### Claim 15 (depends on 14)

The non-transitory computer medium according to claim 14, wherein the shear rate is represented using an expression:
b

(
γ
.
)
=
∑
n
=
1
N


c
n

exp

(
-
γ
.
/
t
n
)
;
where cn and tn are constants.

### Claim 16 (depends on 12)

The non-transitory computer medium according to claim 12, wherein the shear viscosity of the molding fluid is represented using an expression:
η
=
η
0
VE
1
+
(
η
0
VE

γ
.
τ
*
)
1
-
n
;
η
0
VE
=
η
0

(
T
,
P
)

η
VE

(
P
,
γ
.
)
;
where η represents the shear viscosity, {dot over (γ)} represents the shear rate, P represents a molding pressure, T represents a molding temperature, n and τ* represent constants, and ηVE(P,{dot over (γ)}) represents the increase of a shear viscosity of the molding fluid by the decrease of a shear rate.

### Claim 17 (depends on 16)

The non-transitory computer medium according to claim 16, wherein the increase of the shear viscosity of the molding fluid by the decrease of the shear rate is represented using an expression:
ηVE(P,{dot over (γ)})=exp(b({dot over (γ)})P);
where ηVE represents the increase of the shear viscosity, {dot over (γ)} represents the shear rate, P represents a molding pressure, and b({dot over (γ)}) represents the shear rate.

### Claim 18 (depends on 17)

The non-transitory computer medium according to claim 17, wherein the shear rate is represented using an expression:
b

(
γ
.
)
=
∑
n
=
1
N


c
n

exp

(
-
γ
.
/
t
n
)
;
where cn and tn are constants.

### Claim 19 (depends on 12)

The non-transitory computer medium according to claim 12, further comprising a step of calculating a molding pressure of the molding fluid in a molding cavity by taking into consideration the increase of the shear viscosity of the molding fluid by the decrease of the shear rate.

### Claim 20 (depends on 19)

The non-transitory computer medium according to claim 19, wherein the operations further comprise a step of calculating the shrinkage of the molding products by taking into consideration a variation of a specific volume of the molding fluid as the molding pressure decreases.

### Claim 21 (depends on 20)

The non-transitory computer medium according to claim 20, wherein the calculating of the shrinkage further takes into consideration the variation of the specific volume of the molding fluid as a molding temperature decreases.

### Claim 22 (depends on 21)

The non-transitory computer medium according to claim 21, wherein the calculating of the shrinkage further takes into consideration the variation of the specific volume on different parts of the molding fluid.