• 3.1 common defects and solutions of injection molding products

    3.1.1 shortage of materials (insufficient injection) and solutions 50

    3.1.2 shrinkage and solutions 53

    3.1.3 bulge and solutions 55

    3.1.4 shrinkage (vacuum bubble) and solutions 55

    3.1.5 edge overflow (flash, batch front) and solutions 56

    3.1.6 weld lines and solutions 58

    3.1.7 bubbles (cavitation) and solutions 65

    3.1.8 warpage (deformation) and solutions 67

    3.1.9 shrinkage marks and solutions 70

    3.1.10 crazing (silver wire, material flower) and solutions 71

    3.1.11 water ripple and solutions 73

    3.1.12 spray pattern (serpentine pattern) and solutions 74

    3.1.13 tiger skin lines and solutions 77

    3.1.14 streaks (shadows) and solutions 81

    3.1.15 black lines (black strips) and solutions 81

    3.1.16 embrittlement and solutions 82

    3.1.17 cracks (cracks) and solutions 83

    3.1.18 coke burning (carbonization) and solutions 85

    3.1.19 black spots and solutions 86

    3.1.20 top White (top explosion) and solutions 86

    3.1.21 strain (drag) and solutions 88

    3.1.22 color difference and solutions 89

    3.1.23 color mixing and solutions 91

    3.1.24 poor surface gloss and solutions 92

    3.1.25 insufficient transparency and solutions 92

    3.1.26 surface floating fiber and solutions 93

    3.1.27 dimension out of tolerance and solutions 93

    3.1.28 peeling and solutions 94

    3.1.29 cold spots and solutions 94

    3.1.30 insufficient strength of plastic parts and solutions 95

    3.1.31 defective metal inserts and solutions 95

    3.1.32 change from through hole to blind hole and solutions 96

    3.1.33 excessive internal stress and solutions 97

    3.1.34 light spot (ghost) and solutions 97

    3.1.35 loose glue wrapping and solutions 98

    3.1.36 product size instability and solutions 100

    3.1.37 white spots and solutions 101

    3.1.38 cold glue residue and solutions 101

    3.1.39 irregular sinkholes and solutions 102

    3.2 analysis and treatment of product defects

    3.2.1 investigation and understanding of product defects 103

    3.2.2 damic process for dealing with product defects 104

    3.2.3 systematic verification and analysis methods 104

    3.2.4 finding the cause of defects by fishbone diagram 104

    Chapter 4 common problems and solutions in injection molding process

    4.1 common problems and solutions in injection molding process

    4.1.1 unsmooth blanking and solutions 106

    4.1.2 excessive noise during plasticizing and solutions 106

    4.1.3 screw slip and solutions 107

    4.1.4 nozzle blockage and solutions 107

    4.1.5 nozzle casting and solutions 107

    4.1.6 nozzle glue leakage and solutions 108

    4.1.7 die and solutions 108

    4.1.8 product sticking front mold and solutions 108

    4.1.9 die sticking of nozzle material (channel condensate) and solutions 109

    4.1.10 wire drawing and solution of nozzle (front end of main runner) 109

    4.1.11 difficulties in mold opening and solutions 109

    4.1.12 trapped gas caused by hot runner and solutions 110

    4.1.13 long forming cycle and solutions 110

    4.1.14 solutions to other abnormal phenomena 111

    4.2 management of injection molding process

    4.2.1 testing and inspection of injection molded products 112

    4.2.2 preparations before startup 114

    4.2.3 operation specification of injection molding process115

    4.2.4 special measures for injection molding white or transparent products 115

    Feeding position of flow channel (116.5)

    4.2.6 recycling management of nozzle material (channel condensate) 117

    4.2.7 organization and daily management of injection molding production 117

    Chapter 5 Summary of practical experience in injection molding

    5.1 experience on improving the quality of injection molding products

    5.1.1 different types of screws shall be selected for different plastics 119

    5.1.2 pay attention to the three plastic indexes that affect the injection quality 123

    5.1.3 pay attention to several process parameters affecting injection molding quality 124

    5.1.4 pay attention to the relationship between injection and pressure holding 132

    5.2 summary of adjustment methods and skills of injection molding process

    5.2.1 the color of plastic parts in production can be controlled by adjusting the temperature 133

    5.2.2 key factors causing color instability in production 134

    5.2.3 effect of color matching pigments on the strength of injection molded parts 134

    5.2.4 injection molding process for improving dimensional accuracy of plastic parts 135

    5.2.5 solving skills of shrinkage problem of thick wall plastic parts 135

    5.2.6 three process conditions to pay attention to when the shrinkage problem is difficult to solve 136

    5.2.7 solving skills for deformation of large-size planar plastic parts 137

    5.2.8 solutions to serious shrinkage of the outer surface of injection molded parts at the column position 138

    5.2.9 problems needing attention in injection molding of transparent thick wall plastic parts 138

    5.2.10 improvement of melt impact mark on mirror logo 139

    5.2.11 important process conditions to ensure smooth surface of injection molded parts 140

    5.2.12 two matters that are easy to cause overflow and white top and are not easy to attract attention 140

    5.2.13 adjustment method in case of serious edge overflow and top white of injection molded parts 141

    5.2.14 multistage adjustment techniques to prevent air wrinkles when rapid filling is required 141

    5.2.15 methods to prevent more black spots of transparent plastic parts and light colored plastic parts 142

    5.2.16 reasons for easy occurrence of air marks or shot marks at the gate 143

    5.2.17 solutions to the problem of Gate gas grain of PC injection molded parts 144

    5.2.18 reasons and measures for shrinkage of PC plastic parts that are difficult to solve 144

    5.2.19 causes of embrittlement and white fog of injection molded parts of PC material and its process problems 145

    5.2.20 cause analysis of Gate gas pattern of PC parts becoming a difficult problem in injection molding 146

    5.2.21 cause analysis of water ripple and weld mark of large-size PVC plastic parts 146

    5.2.22 effective measures to solve the problem of water ripple of large-size injection molded parts from the perspective of mold146

    5.2.23 adjustment skills for difficult problems of water ripple and weld mark of large PVC injection molded parts 147

    5.2.24 improvement measures for fusion mark and water ripple of PVC injection molded parts 149

    5.2.25 several problems of trapped gas and their improvement measures 151

    5.2.26 adjustment method to solve the problem of gas entrapment caused by melt countercurrent 152

    5.2.27 adjustment method when the filling of each mold cavity is seriously unbalanced 153

    5.2.28countermeasures against easy breakage of thimble during injection molding of K material 153

    5.2.29 reasons for easy engagement of guide post and guide sleeve after disassembly and assembly of large mold154

    5.2.30 solutions to the drag phenomenon of electroplated molds during injection molding 154

    5.2.31 on site treatment method for spot of injection molded parts with matte surface 154

    5.2.32 two kinds of slider (row position) structures that are not conducive to injection molding production 155

    5.2.33 application and skills of adjusting the filling speed of each cavity 155

    5.2.34 problems easily caused by the use of long nozzles and their remedial measures 156

    5.2.35 control measures to prevent poor oil injection and electroplating of injection molded parts in injection molding production 156

    5.2.36 effective measures to solve the oil drop of soft plastic parts with low hardness after oil injection 157

    5.2.37 matching problems and solutions between injection parts production and oil injection mold157

    5.2.38 method of matching adjustment of injection molded parts requiring silver paint 158

    5.2.39 example of gate layout of large-size plastic parts 159

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