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:

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:

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:

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:

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.

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:

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:

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
PCTG	74	PCTA	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
ACRYLIC	99	CAP	78
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
PC	138	ACRYLIC	91
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

Gud Mould Industry Co., Ltd