塑料注塑成型加工課件

1、塑料注塑成型加工向 明四川大學(xué)高分子研究所高分子材料工程國(guó)家重點(diǎn)實(shí)驗(yàn)室塑料注塑成型加工向 明良好的注塑件質(zhì)量獲得的條件適合的注塑設(shè)備適宜的螺桿結(jié)構(gòu)良好的材料預(yù)處理工藝合適的注塑工藝條件合理的模具結(jié)構(gòu)良好的注塑件質(zhì)量獲得的條件適合的注塑設(shè)備塑料注塑基礎(chǔ)注塑加工涉及的過(guò)程1、塑料膠粒的軟化和塑化（螺桿塑化過(guò)程） 螺桿結(jié)構(gòu)的設(shè)計(jì)必須保證得到均勻一致的熔體2、塑料熔體計(jì)量 螺桿轉(zhuǎn)速，背壓3、塑料熔體向鎖閉型腔注射 鎖模力比型腔壓力高20%，熔體以均衡的方式充填模具型腔，以避免內(nèi)應(yīng)力的產(chǎn)生 多級(jí)注塑、充模流動(dòng)行為、型腔壓力分布、熔體PVT性質(zhì)4、冷卻熔體凝固并保持模具型腔形狀 均勻的模具表面溫度，避免制

2、件翹曲、保證尺寸精度5、制件頂出塑料注塑基礎(chǔ)注塑加工涉及的過(guò)程塑化過(guò)程塑化過(guò)程最大計(jì)量行程最大計(jì)量行程屏障螺桿屏障螺桿關(guān)于塑料的特征分子量熔體指數(shù)PVT性質(zhì)剪切稀化行為熱穩(wěn)定性收縮行為最大流動(dòng)比吸濕性關(guān)于塑料的特征分子量PVT性質(zhì)PVT性質(zhì)材料的收縮特性溫度引起的體積變化 結(jié)晶高分子 29% 無(wú)定型高分子 8%壓力引起的體積變化 10-15%材料的收縮特性溫度引起的體積變化塑料注塑成型加工課件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剪切變稀行為剪切變稀行為螺桿壓縮區(qū)的剪切稀化螺桿壓縮區(qū)的剪切稀化噴嘴的剪切稀化噴嘴的剪切稀化熱穩(wěn)定性熱穩(wěn)定性 K x 最大射膠體停留時(shí)間 = - x 成型周期 型腔體積 K x 最大射注塑過(guò)程充模過(guò)程 85-98% 注塑行程切換過(guò)程壓實(shí)過(guò)程冷卻過(guò)程注塑過(guò)程充模過(guò)

7、程 85-98% 注塑行程注塑過(guò)程中的收縮行為注塑過(guò)程中的收縮行為加工過(guò)程對(duì)收縮的影響加工過(guò)程對(duì)收縮的影響不同材料的收縮率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不同材料的收縮率MATERIALS% SHRINKAGEMA塑料注塑成型加工課件收縮收縮收縮與翹曲收縮與翹曲收縮與結(jié)晶收縮與結(jié)晶收縮與加工過(guò)程收縮與加工過(guò)程收縮與取向收縮與取向收縮與冷卻收縮與冷卻充模與冷卻充模與冷卻均衡流動(dòng)均衡流動(dòng)塑料注塑成型加工課件塑料注塑成型加工課件調(diào)整均衡性調(diào)整均衡性調(diào)整均衡性調(diào)整均衡性塑料注塑成型加工課件與模具和機(jī)臺(tái)相關(guān)的注塑缺陷縮痕 壁厚設(shè)計(jì)不均勻 可通過(guò)注塑壓力、保壓壓力、注塑

9、速度調(diào)整尺寸變化 冷卻不均勻，調(diào)整保壓壓力、時(shí)間、強(qiáng)化冷卻均勻性翹曲熔接縫降解重量變化與模具和機(jī)臺(tái)相關(guān)的注塑缺陷縮痕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均衡熱交換均衡熱交換塑料注塑成型加工課件塑料注塑成型加工課件均衡凝固均衡凝固熔接縫熔接縫改變?nèi)劢涌p位置改變?nèi)劢涌p位置成型周期成型周期塑料注塑成型加工課件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決方法工程塑料的加工缺陷及解決方法熱塑性工程塑料的加工材料加工在材料應(yīng)用中處于舉足輕重的地位 特定用途 材料選擇 依據(jù)材料性能的準(zhǔn)確測(cè)試 但在實(shí)際的過(guò)程中,加工過(guò)程并不能完整的將材料性能表達(dá)到具體的制件上 特定用途 材料選擇 加工條件 熱塑性工程塑料的加工材料加工在材料應(yīng)用中處于舉足輕重的地位如果選擇的工程塑料的加工窗口過(guò)窄,塑料會(huì)在加工過(guò)程中發(fā)生力學(xué)、物理、化學(xué)的變化通常, 加工窗口越窄,

17、制件的不合格率越高一般在塑料加工過(guò)程中，制件的質(zhì)量控制主要通過(guò)將其與已知性能的好樣品進(jìn)行比較如果選擇的工程塑料的加工窗口過(guò)窄,塑料會(huì)在加工過(guò)程中發(fā)生力學(xué)熱塑性工程塑料的加工缺陷的發(fā)現(xiàn)目測(cè) 表面、外觀質(zhì)量力學(xué)性能測(cè)試 材料性能和加工條件對(duì)制件使用性能的影 響重量比較尺寸穩(wěn)定性觀察內(nèi)應(yīng)力的表征熱塑性工程塑料的加工缺陷的發(fā)現(xiàn)目測(cè)加工缺陷表觀缺陷 外觀、尺寸、重量變化、制件發(fā)脆等隱性缺陷 導(dǎo)致材料過(guò)早失效加工缺陷表觀缺陷熱塑性工程塑料加工的表觀缺陷黑點(diǎn)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 熱塑性工程塑料加工的表觀缺陷黑點(diǎn)氣泡 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 氣泡流痕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 流痕膠燒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