塑料注塑成型加工

屏障螺杆
关于塑料的特征
分子量 熔体指数 PVT性质 剪切稀化行为 热稳定性 收缩行为 最大流动比
PVT性质
材料的收缩特性
温度引起的体积变化 结晶高分子 29% 无定型高分子 8%
压力引起的体积变化 10-15%
Poly-mer
ABS
CA POM PMMA PPO PA6 /6 PC PES PBT PPS PETP PS HDPE
加工过程对收缩的影响
不同材料的收缩率
MATERIALS Nylon 6 Nylon 6- GR Nylon 6/6 Nylon 6/6 -GR LDPE HDPE Polystyrene
Styrene-acrylonitrile
% SHRINKAGE 1 -1.5 0.5 1 -2 0.5 1.5 - 3 2-3
LDPE
PP
RPVC
SPVC SAN TPU
Density Room Temp.
1.05
1.29 1.42 1.18 1.06 1.14 1.22 1.37 1.31 1.5 - 2.1 1.38 1.05 0.95
0.92
0.91
1.3 - 1.6
1.1 - 1.14 1.08 1.20
Process temp. degree c
0.4 - 0.6 1.2 - 2
0.5
0.5
Acrylic
0.3 - 0.6
Cellulose propionate
0.5
收缩
收缩与翘曲
收缩与结晶
收缩与加工过程
收缩与取向
收缩与冷却
充模与冷却
均衡流动
调整均衡性
调整均衡性
与模具和机台相关的注塑缺陷
缩痕 壁厚设计不均匀 可通过注塑压力、保压压力、注塑速度调整
Only one pressure setting is required during FILLING PHASE.
Pressure Setting should be more than actual filling pressure. as relief valve should not be actuated. If it is actuated, then speed control will be lost.
通常, 加工窗口越窄, 制件的不合格率越 高
一般在塑料加工过程中，制件的质量控 制主要通过将其与已知性能的好样品进 行比较
热塑性工来自百度文库塑料的加工缺陷的 发现
目测 表面、外观质量
力学性能测试 材料性能和加工条件对制件使用性能的 影
响
重量比较 尺寸稳定性观察
加工缺陷
表观缺陷 外观、尺寸、重量变化、制件发脆等
dead edges in gate/runner system
granule impurities degradation by other resins pick-up of degraded material from cylinder wall during cooling
气泡
injection pressure too low inadequate functioning of back flow valve suck-back too long plasticizing too fast air trap in the hopper feed improper feed
increase to shift weld line.
Set SPEED low value say up to 35% not more.
This can be one step of speed for different Holding steps.
Speed set is low, as there is less or no space to move the melt.
Thermal Degradation,
Longer Residence time in the machine,
Creep,
Wrong material selection or poor part design,
Buckling,
Wrong material selection or poor part design
塑料注塑成型加工
向明
四川大学高分子研究所 高分子材料工程国家重点实验室
良好的注塑件质量获得的条件
适合的注塑设备 适宜的螺杆结构 良好的材料预处理工艺 合适的注塑工艺条件 合理的模具结构
塑料注塑基础
注塑加工涉及的过程
1、塑料胶粒的软化和塑化（螺杆塑化过程） 螺杆结构的设计必须保证得到均匀一致的熔体
0.2
NA
NA
50-90
4
1.3 - 1.5
0.8
0.74
150-200
4
0.45
1.00
1.00
170
2 -6
1.5 - 2
0.73
0.94
200
2 -6
NA
0.82
1.05
170
4
1.2 - 2.2
0.63
0.86
60
0.5 - 0.2
NA
NA
180
4
140-180
4
50
3
1 .2
NA
NA
0.5
0.5 - 0.7
0.4 - 0.6
MATERIALS Polycarbonate Acetal PVC - Rigid PVC - Soft ABS PP Cellulose acetate
Cellulose acetate.......... butyrate
% SHRINKAGE 0.8 2
0.5 - 0.7 1-3
2 -6
2
NA
NA
100-130
2 -6
0.4 - 0.8
0.94
0.74
100-140
3 -4
0.4 - 0.7
NA
NA
100-230
2 -4
NA
0.58
0.50
60-100
4
0.7 - 0.8
0.67
0.57
60- 120
4- 5
0.6
0.95
0.83
125-185
4
NA
NA
NA
120-150
4 -6
工程塑料的加工缺陷及解决方 法
热塑性工程塑料的加工
材料加工在材料应用中处于举足轻重的 地位
特定用途 材料选择 依据材料性能的准确测试 但在实际的过程中,加工过程并不能完整的将材料性能表达到 具体的制件上 特定用途 材料选择
加工条件
如果选择的工程塑料的加工窗口过窄, 塑料会在加工过程中发生力学、物理、 化学的变化
NA
NA
40 - 80
3- 4
50-80
2- 4
50 - 80
2- 4
25 - 90
2-4
10 -85
10 - 95
10 - 85
25 - 80
20
20 - 80
15
40 - 80
5- 6
40 - 80
30
100-140
4-6
0.4 - 0.7
0.83
0.83
300
3
0.4 - 0.7
NA
NA
100-230
Cyclic Fatigue,
Voiding,
Notch Sensitivity,
Poor weld lines,
Chemical Attack and; Stress Cracking, Adverse Orientation,
UV Degradation,
Material contamination,
Output ratio related to
Ps
Screw rpm related to
Ps
220-260
0.96
170-250
1.10
192-215
1.16
220-260
1.09
250-290
NA
220-280
0.95
280-310
1.08
330-400
NA
220-270
NA
300-360
NA
260-300
Select end of 1st step and start of 2nd step.
Select end of 2nd step and start of 3rd step
Select end of 3rd step and start of SWITCH OVER POINT. This point is at around 8095% of the injection stroke.
尺寸变化 冷却不均匀，调整保压压力、时间、强化冷却均 匀性
翘曲 熔接缝 降解
POSITION
SPEED
PRESSURE
FILLING PHASE Also known as Speed phase. Also known as Speed phase. There may be no. of steps
Density process temp
%age injection utilisation capacit y
Permissible reside nce time min.
Max-flow ratio for 1mm wall thickne ss
Screw cushion mm
Shrinkage %
2、塑料熔体计量 螺杆转速，背压
3、塑料熔体向锁闭型腔注射 锁模力比型腔压力高20%，熔体以均衡的方式充填模具型腔，以避免内应力 的产生 多级注塑、充模流动行为、型腔压力分布、熔体PVT性质
4、冷却—熔体凝固并保持模具型腔形状 均匀的模具表面温度，避免制件翘曲、保证尺寸精度
5、制件顶出
塑化过程
最大计量行程
1.2
220-270
0.95
220-280
0.74
180-280
0.74
250-275
0.73
170-190
NA
180-200
NA
240-270
0.99
180-225
NA
40 - 80
50 - 80
5- 8
30 - 80
15
35 - 80
4- 8
30 - 80
8
40 - 80
5
50 - 80
2- 3
available on machine. Steps are position controlled.
PRESSURE PHASEHolding phase. There may be no. of steps
available on machine.
Steps are timers controlled.
隐性缺陷 导致材料过早失效
热塑性工程塑料加工的表观缺 陷
黑点
原因
down time too long barrel switched off over a long period of time poor purging of barrel dirty plasticizing unit inadequate nozzle
Timer controls the Holding pressure steps if available on machine.
Holding pressure time for step 1 is set on a timer,
Holding pressure time for step 2 is set on a timer,
Holding pressure 2 set just enough to fill cavity without overpacking.
Holding pressure 3 set just enough to fill cavity without overpacking.
均衡热交换
均衡凝固
熔接缝
改变熔接缝位置
成型周期
The predominantly material causes involved in failure were:
The predominating process faults were:
Environmental Stress Cracking,
Excessive moulded-in stresses,
Filling pressure depends on resistance to move the melt. It depends on flow ratio and viscosity of melt.
Holding pressure 1 set just enough to fill cavity without overpacking.
Holding pressure time for step 3 is set on a timer,
Set SPEED 1 Try to set high. Set SPEED 2 Lower speed for crossing narrow
passage / gate Set SPEED 3 Reduce to lower sink mark /
0.96
1.12
1 - 1.15
NA
NA
剪切变稀行为
螺杆压缩区的剪切稀化
喷嘴的剪切稀化
热稳定性
K x 最大射胶体 停留时间 = ---------------------------- x 成型
周期
型腔体积
注塑过程
充模过程 切换过程 压实过程 冷却过程
85-98% 注塑行程
注塑过程中的收缩行为