표제지

목차

Nomenclature 13

제1장 서론 15

1.1. 연구배경 15

1.2. 연구동향 18

1.3. 연구목적 및 내용 20

1.3.1. 연구목적 20

1.3.2. 연구내용 22

제2장 사출성형 제품의 휨 25

2.1. 사출성형 25

2.1.1. 사출성형공정 25

2.2. 성형수축 및 휨의 발생 요인 29

2.2.1. 성형수축의 발생 요인 29

2.2.2. 휨의 발생 요인 31

2.3. 냉각시스템 33

2.3.1. 금형 냉각 시스템 요소 33

2.3.2. 냉각채널의 종류 33

2.4. 금형의 냉각시간 37

2.5. 금형의 열전달 40

2.5.1. 캐비티 내의 열전달 40

2.6. 열전도 방정식 44

제3장 급속가열·냉각 장치 49

3.1. 히트싱크에 대한 열 해석 49

3.1.1. 히트싱크 설계 49

3.1.2. 히트싱크 모델링 50

3.2. 히트싱크에 대한 수치해석결과 53

3.2.1. 자연대류에서 히트싱크 온도분포 53

3.2.2. 강제대류에서 히트싱크 온도분포 55

3.2.3. 형상에 따른 자연대류와 강제대류의 온도분포 비교 57

3.3. 펠티에 효과 60

3.4. 실험장치 및 실험방법 62

3.4.1. 실험장치 62

3.4.2. 실험방법 65

3.5. 결과 및 고찰 66

3.5.1. 형상에 따른 냉각 66

3.5.2. 형상에 따른 가열 71

3.6. RCHD 구동원리 76

3.7. RCHD 제작 78

3.8. RCHD 성능실험 81

3.8.1. 실험장치 및 방법 81

3.8.2. 결과 및 고찰 82

제4장 열 해석 83

4.1. 열 해석 모델링 83

4.2. 수치해석 결과 85

4.2.1. 시간에 따른 영향 85

4.2.2. TWCD와 RCHD의 비교 88

제5장 사출성형품의 휨 91

5.1. 실험장치 및 실험방법 91

5.1.1. 재료 91

5.1.2. 시편형상 및 금형 93

5.1.3. 사출성형용 금형 94

5.1.4. 사출성형기 95

5.1.5. 사출성형 실험 방법 95

5.2. 휨의 측정방법 97

5.3. 실험결과 99

5.3.1. ABS 수지 99

5.3.2. PP 수지 106

5.3.3. 유동패턴 분석 113

5.3.4. SEM분석 120

5.4. 실험계획법을 통한 최적 사출성형조건 135

제6장 결론 142

참고문헌 145

Abstract 153

Table 3-1. Thermal properties of AL6061 50

Table 3-2. Minimum thickness of the die casting products 50

Table 3-3. Type of surface area 51

Table 3-4. Number of nodes and elements of heat sink 52

Table 3-5. Temperature of heat sink for cooling in the natural convection 53

Table 3-6. Temperature of heat sink for heating in the natural convection 54

Table 3-7. Temperature of heat sink for cooling in the forced convection 56

Table 3-8. Temperature of heat sink for heating in the forced convection 57

Table 3-9. Experimental specification of thermoelectric module HM3030 63

Table 3-10. The specification of silicone grease YG6111 63

Table 3-11. Specifications of thermoelectric module HMT5008/100 77

Table 4-1. Properties of peltier module 84

Table 5-1. Properties of acrylonitrile butadiene styrene(LG-Chem HF-380) 92

Table 5-2. Properties of polypropylene(GS caltex M540) 92

Table 5-3. Injection conditions for experiment of ABS, PP resin 96

Table 5-4. Injection molding condition of various materials for the molding of test specimens 96

Table 5-5. Control factors and levels for ABS resin specimens 135

Table 5-6. Control factors and levels for PP resin 136

Table 5-7. Assignment of control factors to L9(2¹×3⁴)orthogonal array(이미지참조) 137

Table 5-8. Physical layout of the experiment for ABS resin 137

Table 5-9. Physical layout of the experiment for PP resin 138

Table 5-10. Mean, standard deviation and SN ratio for ABS resin 138

Table 5-11. Mean, standard deviation and SN ratio for PP resin 139

Table 5-12. Response table for SN ratio for ABS resin 139

Table 5-13. Response table for SN ratio for PP resin 140

Fig. 1-1. Flow chart for Research 24

Fig. 2-1. Process of injection molding 26

Fig. 2-2. Effect of mould restriction 30

Fig. 2-3. Residual stress caused by molecular orientation 31

Fig. 2-4. Deformation of area shrinkage 32

Fig. 2-5. Mold cooling system 33

Fig. 2-6. Structures of various cooling channel 35

Fig. 2-7. Arrangements of cooling channels 36

Fig. 2-8. Relation between cooling time and coolant temperature 39

Fig. 2-9. Heat transfer path in the injection mold 40

Fig. 2-10. Heat transfer between polymer melt and mold 41

Fig. 2-11. Temperature drop by thermal contact resistance 42

Fig. 2-12. Heat conduction through a large plane wall of thickness Δx and area A 44

Fig. 3-1. Type of heat sink with internal structure 49

Fig. 3-2. Elements of heat sink 52

Fig. 3-3. Temperature distribution of heat sink for cooling in the natural convection 53

Fig. 3-4. Temperature distribution of heat sink for heating in the natural convection 54

Fig. 3-5. Temperature distribution of heat sink for cooling in the forced convection 56

Fig. 3-6. Temperature distribution of heat sink for heating in the forced convection 57

Fig. 3-7. Comparison temperature distribution of the forced and natural convection 59

Fig. 3-8. The principle of peltier module 60

Fig. 3-9. Schematic of the two different types of heat sink with internal structure 62

Fig. 3-10. Schematic of the experimental setup 64

Fig. 3-11. Cooling experiment for heat sink of pine shape and pin shape 67

Fig. 3-12. Compare cooling experiment for heat sink of pine shape and pin shape in the forced convection and the natural convection 69

Fig. 3-13. When the voltage increase, Compare cooling temperature for heat sink of pine shape and pin shape in the forced convection and the... 70

Fig. 3-14. Heating experiment for heat sink of pine shape and pin shape 72

Fig. 3-15. When the voltage increase, compare heating experiment for heat sink of pine shape and pin shape in the forced convection and the natural... 75

Fig. 3-16. Principle of rapid heating and cooling system 77

Fig. 3-17. Rapid heating and cooling device 78

Fig. 3-18. Assembly of water-jackets, rapid heating, and cooling system 79

Fig. 3-19. Test rig of injection mold with temperature controller 80

Fig. 3-20. Experimental method of RCHD 81

Fig. 3-21. Cooling and heating experiment 82

Fig. 4-1. Mesh model 83

Fig. 4-2. Temperature distribution of core according to time change in the water cooling 86

Fig. 4-3. Temperature distribution of core according to time change in the peltier module cooling 87

Fig. 4-4. Temperature measurement position for FEM 88

Fig. 4-5. Comparison temperature of TWCD method with RCHD method 89

Fig. 4-6. Heat transfer of TWCD method and RCHD method 90

Fig. 5-1. Specimen for injection molding experiment 93

Fig. 5-2. Mold for injection molding experiment 94

Fig. 5-3. Injection molding machine (Dongshin Pro-World 100) 95

Fig. 5-4. Measuring method of specimen 97

Fig. 5-5. 3-Dimensional coordinate measuring machine used for experiments 98

Fig. 5-6. Specimen 99

Fig. 5-7. Comparison warpage for cooling time in the ABS resin 101

Fig. 5-8. Comparison warpage for mold temperature in the ABS resin 103

Fig. 5-9. Comparison warpage for packing pressure time in the ABS resin 104

Fig. 5-10. Comparison warpage for packing pressure in the ABS resin 106

Fig. 5-11. Comparison warpage for cooling time in the PP resin 107

Fig. 5-12. Comparison warpage for mold temperature in the PP resin 110

Fig. 5-13. Comparison warpage for packing pressure time in the PP resin 111

Fig. 5-14. Comparison warpage for packing pressure in the PP resin 113

Fig. 5-15. Comparison flow surface of specimens according to cooling time variation in the water cooling 115

Fig. 5-16. Comparison flow surface of specimens according to cooling time variation in the peltier module cooling 116

Fig. 5-17. Comparison flow surface of specimens according to mold temperature variation in the water cooling 118

Fig. 5-18. Comparison flow surface of specimens according to mold temperature variation in the peltier module cooling 119

Fig. 5-19. Position of specimen for SEM 120

Fig. 5-20. Comparison SEM of specimens at cooling time 20 sec in the water cooling (1:2,500 and 1:10,000 for the left and right image,... 122

Fig. 5-21. Comparison SEM of specimens at cooling time 25 sec in the water cooling(1:2,500 and 1:10,000 for the left and right image, respectively) 123

Fig. 5-22. Comparison SEM of specimens at cooling time 30 sec in the water cooling (1:2,500 and 1:10,000 for the left and right image, respectively) 124

Fig. 5-23. Comparison SEM of specimens at cooling time 20 sec in the peltier module cooling (1:2,500 and 1:10,000 for the left and right... 125

Fig. 5-24. Comparison SEM of specimens at cooling time 25 sec in the peltier module cooling (1:2,500 and 1:10,000 for the left and right image,... 126

Fig. 5-25. Comparison SEM of specimens at cooling time 30 sec in the peltier module cooling (1:2,500 and 1:10,000 for the left and right image, re... 127

Fig. 5-26. Comparison SEM of specimens at mold temperature 65 ℃ in the water cooling (1:2,500 and 1:10,000 for the left and right image,... 129

Fig. 5-27. Comparison SEM of specimens at mold temperature 75 ℃ in the water cooling (1:2,500 and 1:10,000 for the left and right image, respectively) 130

Fig. 5-28. Comparison SEM of specimens at mold temperature 85 ℃ in the water cooling (1:2,500 and 1:10,000 for the left and right image, re... 131

Fig. 5-29. Comparison SEM of specimens at mold temperature 65 ℃ in the peltier module cooling (1:2,500 and 1:10,000 for the left and right ima... 132

Fig. 5-30. Comparison SEM of specimens at mold temperature 75 ℃ in the peltier module cooling (1:2,500 and 1:10,000 for the left and right image, respec... 133

Fig. 5-31. Comparison SEM of specimens at mold temperature 85 ℃ in the peltier module cooling (1:2,500 and 1:10,000 for the left and right... 134

Fig. 5-32. Main effect plot for SN ratio 141

 Plastic injection parts are used for automobiles, electronic products, machinery, cellular phones and consumer products. Injection-molded parts can have a complicated shape, do not need pose-processing and have an advantage of mass production. Molding defects occur in plastic parts according to changes in material properties, complicated molding shapes, and process parameters. The injection molding defect, molded sink mark, affects the dimensions and warpage of the product. The molded sink mark is caused by crystallization, elastic recovery of a injection part, crystalline and amorphous polymer, or molding operation conditions (packing pressure, packing time, resin temperature, and mold temperature). The sink mark produces warpage of plastic part.

A method to improve the warpage of the plastic part is removal of residual stress of the plastic product. by making non-uniform cooling occurring in the injection molding process into uniform cooling. In this thesis, the rapid heating and cooling device was developed using a peltier module for uniform cooling.

A heat sink was designed to remove the heat generated for the purpose of increasing the efficiency of the peltier module. The efficiency was compared between the heat sink of Pine fins and that of Pin fins in an tunnel structure at each natural and forced convections. It was verified with computer-aided engineering (CAE) technology and experiments. As a result, the heat sink of Pine fins has a low temperature distribution toward the fin center both in the forced and the natural convection. The forced convection had better efficiency than the natural one regardless of the configuration.

A rapid cooling and heating device (RCHD) was manufactured and compared with the traditional water cooling device (TWCD) method in warpage leading to analysis results. The materials used were crystalline polypropylene and amorphous acrylonitrile-butadiene-styrene polymer. Variations in warpage were compared according to the molding process parameters such as packing pressure, packing time, resin temperature, and mold temperature. Molecular arrangement of injection-molding parts was examined with chemical etching against cooling time and mold temperature.

It can be shown that the RCHD method has a lower warpage than the TWCD method and consequently a more uniform cooling for amorphous acrylonitrile-butadiene-styrene polymer. Injection molded parts of amorphous acrylonitrile-butadiene-styrene polymer were examined after chemical etching. The injection-molding parts by the RCHD method have less distribution of white areas than those by the TWCD method and consequently it can be found that the RCHD method produces a uniform cooling.

The distribution state of the acrylonitrile-butadiene-styrene polymer was confirmed Through the Scanning electron microscope. In the TWCD method the distribution state of the polymer be densely distributed, and RCHD method be distributed wider than TWCD method. this is that injection molded parts be seen that cooling was made uniformly. As the temperature of the mold is gradually progress, The particles of the polymer is increased, this is that internal stress was reduced.

Through of experimental method(DOE), Optimum molding condition of the injection molding are a mold temperature of 75℃, holding time 2.5sec, cooling time 20sec, and the holding pressure for 20% kg/㎠ in the ABS resin. and mold temperature of 35℃, holding time 2.5sec, cooling time 20sec, and the holding pressure for 20% kg/㎠ in the PP resin.