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Technical Brief

[+] Author and Article Information
K. M. Au

Department of Industrial and Systems Engineering,
The Hong Kong Polytechnic University,
Hung Hom,
Kowloon 852, Hong Kong
e-mail: akm_kenneth@yahoo.com.hk

K. M. Yu

EF603, Department of Industrial and Systems Engineering,
The Hong Kong Polytechnic University,
Hung Hom,
Kowloon 852, Hong Kong
e-mail: km.yu@polyu.edu.hk

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received December 29, 2010; final manuscript received January 7, 2014; published online May 21, 2014. Assoc. Editor: Yong Huang.

J. Manuf. Sci. Eng 136(4), 044501 (May 21, 2014) (9 pages) Paper No: MANU-10-1393; doi: 10.1115/1.4026494 History: Received December 29, 2010; Revised January 07, 2014

## Abstract

During thermoplastic injection moulding process, the gradual increase of the coolant temperature along the conformal cooling channel (CCC) inside the rapid tool reduces the rate of heat transfer from the polymeric melt to the cooling channel surface at the outlet portion. Injection moulded defects such as irregular warpage of the part between the coolant inlet and outlet cannot be avoided. Rapid tooling (RT) technology offers a speedy and automatic method for rapid tool design and fabrication integrated with complex internal structure such as CCC. This paper presents a novel adjustment method for cooling distance modification between the CCC and its mould cavity (or core) surface along the cooling channel. The proposed method can compensate the gradual increase of the coolant temperature from the coolant inlet to the coolant outlet. More heat can be transferred from the mould surface near the coolant outlet to the proposed variable distance conformal cooling channel (VDCCC). In this study, the cooling channel distance modification relies on two adjustment attributes: (1) the adjustment direction and (2) the adjustment amount, between the mould cavity (or core) surface (terrain) and the cooling channel axis (polyline) after the linearized approximation. A computer-aided melt flow analysis tool of moldflow plastics insight is employed in the case study in order to demonstrate the feasibility of the proposed method. The cooling performance of the proposed VDCCC design can be verified.

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## Figures

Fig. 1

Temperature variation between the coolant inlet and the coolant outlet

Fig. 2

Conventional CCC (a) CCC with variable distance (b)

Fig. 3

Workflow of the proposed adjustment method

Fig. 4

Relationship between the parting and the heat transfer directions

Fig. 5

Normal offsetting of a mould surface

Fig. 6

Cooling channel axis on the offset mould surface

Fig. 7

Cooling channel axis above the M→(u,v)

Fig. 8

Tangent plane of the cooling channel axis cutting the mould surface

Fig. 9

Linearized approximation of the mould surface and the cooling channel axis

Fig. 10

Approximation of curve on mould surface into polyline (straight line) segment

Fig. 11

Possible AiJij→ on I→i (a) and adjustment a∧ on I→i(b)

Fig. 12

Fig. 13

Adjustment amount for the new axis position of the A→'

Fig. 14

A→' the for new cooling channel axis formation

Fig. 15

A→ (axis for CCC) and A→' (axis for the VDCCC) at side view

Fig. 16

(a) VDCCC and (b) CCC and VDCCC with generation

Fig. 17

(a) CAD mould surface model, (b) normal offsetting, (c) the cooling channel axis creation, and (d) the cooling channel axis extraction for the proposed adjustment

Fig. 18

(a) Linearized approximation between the mould surface model and the cooling channel axis and (b) adjustment of the cooling channel axis by the cutting plane

Fig. 19

Comparison of the geometric designs between the conventional CCC and the VDCCC in MPI 3.1, (a) trimetric view and (b) side view

Fig. 20

Comparison of conventional CCC and the VDCCC (designs after the mesh generation process in MPI

Fig. 21

Maximum part temperature,  °C, (a) the conventional CCC and (b) the proposed VDCCC

Fig. 22

Average temperature, part  °C, (a) the conventional CCC and (b) the proposed VDCCC

Fig. 23

Volumetric shrinkage, %, (a) the conventional CCC and (b) the proposed VDCCC

Fig. 24

Average temperatures, part at different positions on the mould surface, (a) CCC and (b) VDCCC

Fig. 25

The plot of average temperatures, part against different cooling channel positions between the CCC and the VDCCC

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