塑料注塑成型加工

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:
Environmental Stress Cracking, Cyclic Fatigue, Notch Sensitivity, UV Degradation,
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 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
Styrene-acrylonitrile
0.4 - 0.6
Cellulose acetate.......... butyrate
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
The predominating process faults were:
Excessive moulded-in stresses, Voiding, Poor weld lines, Material contamination,
Chemical Attack and; Stress Cracking, Adverse Orientation,
NA NA 0.94 NA 0.58 0.67 0.95 NA NA 0.8 1.00 0.73
NA NA 0.74 NA 0.50 0.57 0.83 NA NA 0.74 1.00 0.94
LDPE
0.92
180-280
0.74
10 - 95
200
2-6
NA
0.82
1.05
PP
0.91
250-275
granule impurities degradation by other resins pick-up of degraded material from cylinder wall during cooling
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
170-250 192-215 220-260 250-290 220-280 280-310 330-400 220-270 300-360 260-300 220-270 220-280
Thermal Degradation,
Creep, Buckling,
Longer Residence time in the machine,
Wrong material selection or poor part design, Wrong material selection or poor part design
1.10 1.16 1.09 NA 0.95 1.08 NA NA NA 1.2 0.95 0.74
50 - 80 30 - 80 35 - 80 30 - 80 40 - 80 50 - 80 NA 40 - 80 50-80 50 - 80 25 - 90 10 -85
5- 8 15 4- 8 8 5 2- 3 NA 3- 4 2- 4 2- 4 2-4
PRESSURE PHASEHolding phase. There may be no. of steps available on machine. Steps are timers controlled.
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 time for step 3 is set on a timer,
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.
塑化过程
百度文库
最大计量行程
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 吸湿性
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
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
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 % SHRINKAGE 1 -1.5 0.5 1 -2 0.5 1.5 - 3 2-3 0.5 - 0.7 MATERIALS Polycarbonate Acetal PVC - Rigid PVC - Soft ABS PP Cellulose acetate % SHRINKAGE 0.8 2 0.5 - 0.7 1-3 0.4 - 0.6 1.2 - 2 0.5
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 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
热塑性工程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 内应力的表征
加工缺陷


表观缺陷 外观、尺寸、重量变化、制件发脆等 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 dead edges in gate/runner system
Screw cushion mm
Shrinkage %
Output ratio related to Ps
Screw rpm related to Ps
ABS
1.05
220-260
0.96
40 - 80
100-140
4-6
0.4 - 0.7
0.83
0.83
CA POM PMMA PPO PA6 /6 PC PES PBT PPS PETP PS HDPE
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 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 重量变化
POSITION
SPEED
PRESSURE
FILLING PHASE Also known as Speed phase. Also known as Speed phase. There may be no. of steps available on machine. Steps are position controlled.
0.73
10 - 85
170
4
1.2 - 2.2
0.63
0.86
RPVC
1.3 - 1.6
170-190
NA
25 - 80
20
60
0.5 - 0.2
NA
NA
SPVC SAN TPU
1.1 - 1.14 1.08 1.20
180-200 240-270 180-225
NA 0.99 NA
20 - 80 40 - 80 40 - 80
15 5- 6 30
180 140-180 50
4 4 3
1 .2 0.5 1 - 1.15
NA 0.96 NA
NA 1.12 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
Density Room Temp.
Process temp. degree c
Density process temp
%age injection utilisation capacit y
Permissible reside nce time min.
Max-flow ratio for 1mm wall thickne ss
300 100-230 100-130 100-140 100-230 60-100 60- 120 125-185 120-150 50-90 150-200 170
3 2-6 2-6 3-4 2-4 4 4- 5 4 4-6 4 4 2-6
0.4 - 0.7 2 0.4 - 0.8 0.4 - 0.7 NA 0.7 - 0.8 0.6 NA 0.2 1.3 - 1.5 0.45 1.5 - 2
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. 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 2 set just enough to fill cavity without overpacking. Holding pressure 3 set just enough to fill cavity without overpacking.
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 / increase to shift weld line.
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.