塑料注塑成型加工课件

1、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塑料注塑成型加工向 明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良好的注塑件质量获得的条件适合的注塑设备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

2、件翘曲、保证尺寸精度5、制件顶出塑料注塑基础注塑加工涉及的过程塑化过程塑化过程最大计量行程最大计量行程屏障螺杆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关于塑料的特征分子量PVT性质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%材料的收缩特性温度引起的体积变化塑料注塑成型加工课件Poly-merDensityRoomTemp.Process temp.degree cDensity process temp%age injection utilisa-tion capacityP

3、ermissible residence time - min.Max-flow ratio for 1mm wall thicknessScrew cushionmmShrinkage %Output ratio related toPsScrew rpm related toPsABS1.05220-2600.9640 - 80100-1404-60.4 - 0.70.830.83CA1.29170-2501.1050 - 805- 830030.4 - 0.7NANAPOM1.42192-2151.1630 - 8015100-2302 - 62NANAPMMA1.18220-2601.

4、0935 - 804- 8100-1302 - 60.4 - 0.80.940.74PPO1.06250-290NA30 - 808100-1403 - 40.4 - 0.7NANAPA6 /61.14220-2800.9540 - 805100-2302 - 4NA0.580.50PC1.22280-3101.0850 - 802- 360-10040.7 - 0.80.670.57PES1.37330-400NANANA60- 1204- 50.60.950.83PBT1.31220-270NA40 - 803- 4125-1854NANANAPPS1.5 - 2.1300-360NA50

5、-802- 4120-1504 - 60.2NANAPETP1.38260-3001.250 - 802- 450-9041.3 - 4PS1.05220-2700.9525 - 902-4150-20040.451.001.00HDPE0.95220-2800.7410 -851702 - 61.5 - 20.730.94LDPE0.92180-2800.7410 - 952002 - 6NA0.821.05PP0.91250-2750.7310 - 8517041.2 - 2.20.630.86RPVC1.3 - 1.6170-190NA25 - 8020600.5 -

6、0.2NANASPVC1.1 - 1.14180-200NA20 - 801518041 .2NANASAN1.08240-2700.9940 - 805- 6140-18040.50.961.12TPU1.20180-225NA40 - 80305031 - 1.15NANAPoly-merDensityProcess temp.De剪切变稀行为剪切变稀行为螺杆压缩区的剪切稀化螺杆压缩区的剪切稀化喷嘴的剪切稀化喷嘴的剪切稀化热稳定性热稳定性 K x 最大射胶体停留时间 = - x 成型周期 型腔体积 K x 最大射注塑过程充模过程 85-98% 注塑行程切换过程压实过程冷却过程注塑过程充模过

7、程 85-98% 注塑行程注塑过程中的收缩行为注塑过程中的收缩行为加工过程对收缩的影响加工过程对收缩的影响不同材料的收缩率MATERIALS% SHRINKAGEMATERIALS% SHRINKAGENylon 61 -1.5Polycarbonate0.8Nylon 6- GR0.5Acetal2Nylon 6/61 -2PVC - Rigid0.5 - 0.7Nylon 6/6 -GR0.5PVC - Soft1 - 3LDPE1.5 - 3ABS0.4 - 0.6HDPE2 - 3PP1.2 - 2Polystyrene0.5 - 0.7Cellulose acetate0.5Styr

8、ene-acrylonitrile0.4 - 0.6Cellulose acetate. butyrate0.5Acrylic0.3 - 0.6Cellulose propionate0.5不同材料的收缩率MATERIALS% SHRINKAGEMA塑料注塑成型加工课件收缩收缩收缩与翘曲收缩与翘曲收缩与结晶收缩与结晶收缩与加工过程收缩与加工过程收缩与取向收缩与取向收缩与冷却收缩与冷却充模与冷却充模与冷却均衡流动均衡流动塑料注塑成型加工课件塑料注塑成型加工课件调整均衡性调整均衡性调整均衡性调整均衡性塑料注塑成型加工课件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

9、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与模具和机台相关的注塑缺陷缩痕POSITIONSPEEDPRESSUREFILLING PHASEAlso known as Speed phase.Select end of 1st step and start of 2nd step.Set SPEED 1Try to set high.Only one pressure setting is required during FILLING PHASE.Pressure Setting should be more than actual filling

10、 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.Also known as Speed phase.There may be no. of steps available on machine.Select end of 2nd ste

11、p and start of 3rd stepSet SPEED 2Lower speed for crossing narrow passage / gateSteps are position controlled.Select end of 3rd step and start of SWITCH OVER POINT. This point is at around 80-95% of the injection stroke.Set SPEED 3Reduce to lower sink mark / increase to shift weld line.PRESSURE PHAS

12、E-Holding phase.There may be no. of steps available on machine.Timer controls the Holding pressure steps if available on machine.Holding pressure time for step 1 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, a

13、s there is less or no space to move the melt.Holding pressure 1 set just enough to fill cavity without overpacking.Steps are timers controlled.Holding pressure time for step 2 is set on a timer,Holding pressure 2 set just enough to fill cavity without overpacking.Holding pressure time for step 3 is

14、set on a timer,Holding pressure 3 set just enough to fill cavity without overpacking.POSITIONSPEEDPRESSUREFILLING P均衡热交换均衡热交换塑料注塑成型加工课件塑料注塑成型加工课件均衡凝固均衡凝固熔接缝熔接缝改变熔接缝位置改变熔接缝位置成型周期成型周期塑料注塑成型加工课件The predominantly material causes involved in failure were:The predominating process faults were:Environmenta

15、l Stress Cracking,Excessive moulded-in stresses,Cyclic Fatigue,Voiding,Notch Sensitivity,Poor weld lines,Chemical Attack and; Stress Cracking,Adverse Orientation,UV Degradation,Material contamination,Thermal Degradation,Longer Residence time in the machine,Creep,Wrong material selection or poor part

16、 design,Buckling,Wrong material selection or poor part designThe predominantly material cau工程塑料的加工缺陷及解决方法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 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,

17、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热塑性工程塑料的加工缺陷的发现目测加工缺陷表观缺陷 外观、尺寸、重量变化、制件发脆等隐性缺陷 导致材料过早失效加工缺陷表观缺陷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 pu

18、rging of barrel dirty plasticizing unit inadequate nozzledead edges in gate/runner system granule impurities degradation by other resins pick-up of degraded material from cylinder wall during cooling 热塑性工程塑料加工的表观缺陷黑点气泡 injection pressure too low inadequate functioning of back flow valve suck-back to

19、o long plasticizing too fast air trap in the hopper feed improper feed volatiles and trapped gas mould temperature too low thin to thick transition melt overheating1. control holding / injection pressure 2. increase back pressure 3. increase mould temperature 4. check back flow valve 5. allow for ad

20、equate venting 6. enlarge gate 7. shorten land length 气泡流痕injection speed too slow or too fast injection pressure too low hold pressure too long inadequate mould cooling mould too hot around gate mould too cold gate too small wrong gate location gate land length too long wrong hot runner system melt

21、 temperature too low 1. adapt injection speed 2. add a large cold slug area 3. add cold wells at the end of runner systems 4. control nozzle heat better: if necessary add beryllium copper tip (not recommended for FR resins) 5. shorten or eliminate standard sprue bushing:use a hot sprue bushing 6. cl

22、ean flow must exist from the cylinder, adaptor, nozzle and tip: avoid and eliminate any dead pockets or sections 流痕胶烧problems with back flow valve injection speed too fast back pressure too high inadequate venting : entrapped air frictional burning check sprue diameter melt too hot or too cold:may create sh