New structure of classic front mold stripping thread and rear mold lifter

Time:2023-09-09 19:21:04 / Popularity: / Source:

In mold design, structure of front mold is also out of box, including lifter of front mold, slider of front mold, and inner slider of front mold. However, when encountering some consumer electronic products, in order to meet product assembly and function requirements, some products are designed with undercuts on the front and rear molds, as shown in product below, there are several rounds of undercuts with screw teeth on front mold, and threaded undercuts on back mold. How do these undercuts come out? Today I will share with you a classic structure of front mold stripping thread and rear mold lifter. I hope to give you some inspiration:
mold design 

Product glue feeding method

There are many kinds of product glue feeding methods, such as bottom glue feeding, submerged glue feeding, direct gate, corner glue feeding, point glue feeding, etc. Since back mold of this product is not easy to feed glue, it adopts hot runner to cold runner (submerged glue feeding). Submerged glue feeding can submerge front mold, rear mold, thimble, and bone position. This set of molds adopts glue feeding method of diving into front mold, as shown in figure below:
mold design 

In order to facilitate processing, front mold inserts are inserted separately

There are many glue positions on the front mold inserts. Cooling glue position is designed to transport water in a spiral on insert, as shown in figure below:
mold design 

Design of rack and pinion mechanism

Pay attention to design of rack and pinion structure. Pressure angle of national standard gear is 20 degrees. Modulus of the two gears must be equal so that two gears can mesh normally. When designing structure, a brace is also designed. Number of turns of gear is related to number of turns of screw teeth of product. When designing, it must be noted that number of rotations of gear (circumference) is equal to distance from rack, otherwise gear will be easily pulled off, as shown in figure below:
mold design 

Inner buckle of rear mold adopts an ordinary lifter structure

When designing lifter, attention should be paid to angle range (3-12) degrees of lifter. Material of lifter is generally H13 or 1.2344. Lifter needs heat treatment: it is generally hardened to (48-52) HRC, and surface of lifter needs to be nitrided. Due to limited space, angle of four lifters is designed to be 3 degrees, and fixing method of bolt is adopted. When matching mold, it is necessary to install four lifters in rear mold core to save mold together.
mold design 

Pay attention when designing lifter seat

Due to limitation of space, lifter seat adopts mosaic structure, which is divided along direction of 45 degrees, and lifter seat is designed as a guide chute, which is convenient for processing. Each lifter seat can be processed directly by wire cutting, which saves space. Disadvantage is that it increases workload of fitter for mold matching. Fixing method of lifter seat: use screws to fix it on thimble bottom plate, as shown in figure below:
mold design 

Movement principle

When mold is opened, oil cylinder drives rack to move. Rack hangs on oil cylinder through T-block, rack drives pinion to rotate, pinion and big gear are connected together through bearings. When big green gear rotates, it will drive tooth gear of product to rotate together, so as to achieve effect of product thread removal. When product thread comes out, product remains in rear mold. At this time, ejector pin moves ejector plate through ejector hole, driving lifter of rear mold to move upward together. At this time, product is ejected out of mold, as shown in following figure:
mold design 

Heat distortion thermometer for common plastics

Heat distortion temperature
Heat deflection temperature (low pressure) ASTM D 648 Heat Deflection Temperature (High Pressure) ASTM D 648
Variety °C Variety °C
PET 67 Polyester Elastomer 49
ETG 70 PET 62
PVC 70 PETG 64
PCTA 73 PA 65
CA 81 PCTG 65
K-RESIN 85 Homo-polymer PP 65
CAB 85 PVC 67
CAP 88 Flame Retardant PP 70
CLEAR ABS 89 High Heat Resistance PP 70
Polyster Elastomer 90 CA 71
m-PPO 92 CAB 74
SAN 92 PA 66 75
gABS 95 K-RESIN 77
PC/ABS 104 m-PPO 80
Homo-polymer PP 105 SAN 80
Flame Retardant PP 110 CLEAR ABS 83
High Heat Resistance PP 135 ABS 84
POM(Co-) 160 PC/ABS 95
PP+30%GF 165 POM(Co-) 110
POM(Homo-) 170 POM(Homo-) 124
PSU 179 PC 131
PA 6 180 PP+30%GF 155
PES 208 PSU 167
PBT+20%GF 217 PBT+20%GF 193
PA 66 220 PBT+30%GF 195
PBT+30%GF 220 PES 195
PET+30%GF 239 PCTA+15%GF 202
PA66+13%GF 240 PET+30%GF 217
PA66+33%GF 250 PA66+13%GF 230
PCTA+15%GF 259 PA66+33%GF 245
PPS 260 PCT+30%GF 247
LCP+30%GF 265 PPS 260
PCT+30%GF 275 LCP+30%GF 265

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