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1、Air trapsAir traps困气What is an air trapWhat is an air trapAn air trap is air that is caught inside the mold cavity.It becomesAn air trap is air that is caught inside the mold cavity.It becomestrappedtrapped byby convergingconverging polymerpolymer meltmelt frontsfronts oror becausebecause itit faile
2、dfailed toto escapeescapefrom the mold vents,or mold inserts,which also act as vents.Air-trapfrom the mold vents,or mold inserts,which also act as vents.Air-traplocationslocations areare usuallyusually inin areasareas thatthat fillfill last.last.LackLack ofof ventsvents oror undersizedundersizedvent
3、s in these last-to-fill areas are a common cause of air traps andvents in these last-to-fill areas are a common cause of air traps andthe resulting defects.Another common cause is race-tracking(thethe resulting defects.Another common cause is race-tracking(thetendency of polymer melt to flow prefere
4、ntially in thicker sections),tendency of polymer melt to flow preferentially in thicker sections),caused by a largecaused by a largethickness ratio.thickness ratio.困气是气体存在于模具型腔内无法排出，困气是气体存在于模具型腔内无法排出，困气会形成气孔是其聚集在熔体前端或未从模具排气孔以及镶件排出。困气通困气会形成气孔是其聚集在熔体前端或未从模具排气孔以及镶件排出。困气通常发生在最终填充位置。在填充末端缺少排气孔或排气孔太小都会引起空
5、位造常发生在最终填充位置。在填充末端缺少排气孔或排气孔太小都会引起空位造成制品缺陷。另一个较为普遍的原因是跑马场效应（聚合物熔体有优先向肉厚成制品缺陷。另一个较为普遍的原因是跑马场效应（聚合物熔体有优先向肉厚方向流动的趋势），是由于壁厚突变引起的。方向流动的趋势），是由于壁厚突变引起的。FIGURE 1.Air trap locations indicated by the computer-predicted melt-front advancements.(To replay the animation,click)Problems caused by air trapsEntrapped
6、 air will result in voids and bubbles inside the molded part,a short shot(incomplete fill),or surface defects such as blemishes orburn marks.To eliminate air traps,you can modify the filling patternby reducing the injection speed,enlarging venting,or placing properventing in the cavity.困气将引起成型制品内部空位
7、和气泡，短射（浇不足），或表面缺陷如污痕或烧焦。可以利用改善成型条件来解决困气问题，如减少注射速度，扩大排气孔，或者适当位置开设排气孔。In the figure below,an air trap results from race-tracking in a part witha large thickness ratio.In this case,the entrapped air can be ventedby changing the thickness ratio or by placing a vent.,via an ejectorpin)at the air trap loc
8、ation.以下的例子中，困气是由于壁厚突变产生的跑马场效应引起的。困气可以由减小壁厚变化率或者适当位置开设排气孔消除。Remedies补救措施Alter the part design 改变零件的设计Reduce the thickness ratio.Reduce the thickness ratio.减少壁厚变化减少壁厚变化This will minimize the race-tracking effect of polymer melt.可以减少聚合物熔体的跑马场效应。Alter the mold design 改变模具的设计Pay close attention to the p
9、roper placement of your vents.密切关注开设排气孔位置Place vents in the areas that fill last.Place vents in the areas that fill last.在熔体流动末端开设排气槽在熔体流动末端开设排气槽Vents are typically positioned at discontinuities of mold material,suchas at parting surfaces,between the insert and mold wall,at ejector pins,and at mold
10、slides.排气孔通常开设在模具中断处，比如分型面、镶件与模具间隙、顶针、滑块等。Re-design the gate and delivery system.Re-design the gate and delivery system.重新设计浇口和浇注系统重新设计浇口和浇注系统Changing the delivery systemcan alter the filling pattern in such a waythat the last-to-fill areas are located at the proper venting locations.改变浇筑系统可以改变充填形式使
11、得流动末端布置好排气。MakeMake suresure thethe ventvent sizesize isis largelarge enoughenough soso thatthat thethe airair presentpresent inin thethe cavitycavity cancan escapeescapeduring injection.during injection.排气槽尺寸应足够大以使得气体可以在充填过程中排出。排气槽尺寸应足够大以使得气体可以在充填过程中排出。Be careful,however,that the vent is not so lar
12、ge that it causes flashat the edge ofthe molding.The recommended vent sizeis 0.025 mm inch)for crystalline polymers,and 0.038 mm inch)for amorphous polymers.但是，排气槽不能太大防止制品产生飞边。对于结晶型塑料，排气槽应小于0.025mm，不定形塑料应小于 0.038mm。Adjust the molding conditions改善填充条件Reduce the injection speed.Reduce the injection sp
13、eed.减少注射速度减少注射速度High injection speeds can lead to jetting,which causes air to becomeentrapped in the part.Lowering the injection speed will give the airdisplaced by the melt sufficient time to escape from the vents.速度过高会引起喷射，这会使气体无法逃脱。较低的注射速度可以使气体有充足的时间从排气槽排出。Black specks/black streaksBlack specks/b
14、lack streaks 黑斑和黑黑斑和黑痕痕What are black specks and black streaksWhat are black specks and black streaksBlack specks and black streaks are dark spots or dark streaks found onBlack specks and black streaks are dark spots or dark streaks found onthe surface or throughout a molded part.Brown specks or str
15、eaks referthe surface or throughout a molded part.Brown specks or streaks referto the same type of defect,except the burning or discoloration is notto the same type of defect,except the burning or discoloration is notas severe.as severe.黑斑和黑痕是出现于制品表面或贯穿在整个零件内部的黑点或黑条黑斑和黑痕是出现于制品表面或贯穿在整个零件内部的黑点或黑条纹。它们都
16、是同种形式的缺陷，是不太严重的烧焦或色变。纹。它们都是同种形式的缺陷，是不太严重的烧焦或色变。Causes of black specks/black streaksBlack specks and black streaks are caused by overheated(degraded,burned)material or by contamination of the resin.黑斑和黑痕是由于材料过热或树脂被污染而引起的。Material degradation?Material degradation?Overheated materials can degrade and l
17、ead to black streaks.Material thatstays in the nickedrough surfaces of the barrel wall andscrew surfacesfor a prolonged period of time after heating will char and degrade,resulting in the defect.材料过热会降解导致黑痕，材料在加热过程中停留在粗糙的料筒和螺杆表面的时间过长会烧焦并讲解，导致产品缺陷。Material contamination?Material contamination?Contami
18、nants in the air or material,such as dirty regrind,foreignmaterial,different color material,or a lower melt-temperature material,are what most often lead to black specks and black streaks.Airborne dirtcan also cause dark spots on the surface of a molded part.在空气中或被其它材料污染，比如被污染的外来料，不同颜色的材料，低熔点材料，都通常引
19、起黑斑和黑痕的原因。空气中的粉尘也是会引起成型制品表面的黑斑。Other defects resulting from the same causes相同原因引起的其他缺陷脆化烧焦色变RemediesHandle the material carefully小心使用材料Make sure no contaminated materials,such as dirty regrind,are blended into theMake sure no contaminated materials,such as dirty regrind,are blended into theoriginal
20、material.original material.确保没有被污染的材料，比如脏的再生料加入到原材料当中。确保没有被污染的材料，比如脏的再生料加入到原材料当中。Put the cover on the hopper and all bins of material.Airborne dirt can contaminatePut the cover on the hopper and all bins of material.Airborne dirt can contaminatethe original material,leading to black spots.the origin
21、al material,leading to black spots.将容器盖上盖子，空气中的灰尘会污染原将容器盖上盖子，空气中的灰尘会污染原料导致黑斑。料导致黑斑。Alter the mold design 改变模具设计CleanClean thethe ejectorsejectors andand slides.slides.TheThe streaksstreaks couldcould bebe causedcaused byby thethe greasegrease oror lubricantslubricantson the slides or ejectors.on the
22、 slides or ejectors.清洁顶针和滑块，条纹可以由滑块或顶针上的油脂或润滑油引起。清洁顶针和滑块，条纹可以由滑块或顶针上的油脂或润滑油引起。Improve the venting system.If the black specks are found at the end of flow paths orImprove the venting system.If the black specks are found at the end of flow paths orblind spots,they are likely caused by a poor venting s
23、ystem.Compressed air trappedblind spots,they are likely caused by a poor venting system.Compressed air trappedin the cavity is sometimes ignited,leading to the defect.in the cavity is sometimes ignited,leading to the defect.改善排气系统，如果在流动改善排气系统，如果在流动末端或盲点发现有黑斑，末端或盲点发现有黑斑，有可能是由于排气不良引起的。有可能是由于排气不良引起的。被压
24、缩的型腔内的气体有时会被点燃，被压缩的型腔内的气体有时会被点燃，造成产品缺陷。造成产品缺陷。Clean or polish any nicked surface on the runner system to keep dirt from lodging inClean or polish any nicked surface on the runner system to keep dirt from lodging inthese areas.these areas.Clean the mold before molding.Clean the mold before molding.清洁
25、或抛光流道内的粗糙表面，使污垢远离这些区域。并在清洁或抛光流道内的粗糙表面，使污垢远离这些区域。并在成型前进行清洁。成型前进行清洁。Select a proper machine 选用适合的机台Size a proper injection machine for a specific mold.Size a proper injection machine for a specific mold.The typical shot size should be between 20 and 80 percent of machineinjection capacity.For temperat
26、ure-sensitive materials,the rangeshould be narrowed down more.Plastics simulation software can help youselect the right size injection machine for a specific mold.This willhelp avoid resin remaining in the heated barrel for prolonged periods oftime.注射量应为注射机最大注射量的 20%80%，对于温度敏感型材料，变化范围应该更窄些，塑胶仿真软件可以为
27、成型模具选择适合的注射机。有助于避免塑料在加热料筒中停留时间过长。Check for scratched or dented barrel/screw surfaces that trap material.Check for scratched or dented barrel/screw surfaces that trap material.检验刮伤或凹检验刮伤或凹陷的料筒或螺杆表面是否留有材料陷的料筒或螺杆表面是否留有材料This could lead to the material becoming overheated or burned.残存的材料将会过热或烧焦Check for
28、 local overheating by a run-away heater band or a malfunctioning temperatureCheck for local overheating by a run-away heater band or a malfunctioning temperaturecontroller.controller.检验是否因料筒加热器脱离或温度控制器的故障引起局部过热。检验是否因料筒加热器脱离或温度控制器的故障引起局部过热。Adjust the molding conditions调节成型条件Lower the barrel and nozzl
29、e temperature.Lower the barrel and nozzle temperature.降低料筒或喷嘴温度降低料筒或喷嘴温度Material degradation can result from a high melt temperature.材料讲解会由熔体温度过高引起Purge and clean the injection unit.Purge and clean the injection unit.清洁注射装置清洁注射装置The black streaks might be caused by contamination from the barrel wall
30、or the screw surface.When molding with two materials,after switchingfrom one material to the other,the old material might not be purged fromthe barrel completely.This could generate defects during the molding ofthe second material.黑痕可能会由于被污染的料筒壁或螺杆表面引起。当注射两种不同材料并从一种材料转换成另一种材料时，旧材料可能没有被完全清洗，在成型第二种材料时
31、就会产生缺陷。Avoid recycling rejected parts with black specks and black streaks.Avoid recycling rejected parts with black specks and black streaks.避免回收使用有黑避免回收使用有黑痕或黑斑的不良制品。痕或黑斑的不良制品。Recycling such parts could lead to further contamination,unless theyllbe used for parts that are in black or for which such
32、 defects areacceptable.回收利用该种类型的制品会导致更深一层的污染，除非它们是用于黑色或该缺陷是可以接受的零件。BrittlenessBrittlenessWhat is brittlenessWhat is brittleness脆化A brittle molded part has a tendency to break or crack.BrittlenessA brittle molded part has a tendency to break or crack.Brittlenessresults from material degradation leadi
33、ng to shorter molecular chainresults from material degradation leading to shorter molecular chainlengthlength(thusthus lowerlower molecularmolecular weight).weight).AsAs a a result,result,thethe physicalphysical integrityintegrityof the part is substantially less than the specification.of the part i
34、s substantially less than the specification.脆性零件有脆性零件有断裂或爆裂的倾向。脆化是由于材料降解导致分析链缩短（可减轻分子量）造断裂或爆裂的倾向。脆化是由于材料降解导致分析链缩短（可减轻分子量）造成的。结果，零件的物理性能达不到要求。成的。结果，零件的物理性能达不到要求。FIGURE 1.Degraded part tends to be brittle and break easilyCauses of brittlenessBrittleness is caused by material degradation due to 脆化是由于材料
35、讲解引起的：Improper drying conditions 不合理的干燥条件Improper temperature setting 不合理的温度设定Improper runner system and gate design 不合理的流道系统和浇口的设定Improper screw design 不合理的螺杆设计Weld line weakness 结合线较弱Other defects resulting from the same causes相同的原因会导致以下缺陷黑斑或黑痕烧焦色变RemediesAdjust the material preparationSet proper
36、drying conditions before molding.Set proper drying conditions before molding.成型前设置适合的干燥条件Brittleness can be caused by excessive drying time or drying temperaturesuch as at full heat for several days.Excessive drying either drives offvolatiles in the plastic,making it more sensitive to processing,ord
37、egrades the material by reducing the molecular weight.Materialsuppliers can provide optimum drying conditions for the specificmaterials.脆化可能是由于干燥时间过久或干燥温度过高引起的。过量的干燥不仅会使塑料不稳定，造成对工艺条件较为敏感，而且会使分子量减少造成材料降解。材料供应商会对各种材料提供适合的干燥条件。ReduceReduce regrindregrind material.material.TheThe brittlenessbrittleness
38、couldcould bebe causedcaused byby tootoo muchmuch regroundreground materialmaterialadded into the original virgin material.added into the original virgin material.脆化也有可能是因为太多再生料加入到原料当中。脆化也有可能是因为太多再生料加入到原料当中。Change to a high-strength material since low-strength materials tend to become moreChange to
39、a high-strength material since low-strength materials tend to become morebrittle if processed improperly.brittle if processed improperly.在工艺条件不适当的条件下，如果在工艺条件不适当的条件下，如果 强度材料容易脆化，则强度材料容易脆化，则改用高强度材料改用高强度材料Alter the mold designEnlarge the sprue,runner,and/or gate.Enlarge the sprue,runner,and/or gate.增大主
40、流道、分流道、浇口。增大主流道、分流道、浇口。Restrictive sprue,runner,gate,or even part design could cause excessiveshear heating that aggravates an already overheated material,causingmaterial degradation.主流道、分流道和浇口甚至制品过小都会产生大量的剪切热，使材料的过热加重，引起材料降解。Select a proper machine/machine componentGet a better screw design for the
41、 material youre using to achieve a better mixed meltGet a better screw design for the material youre using to achieve a better mixed melttemperature.temperature.改善螺杆设计以使熔体充分混合并达到所需温度改善螺杆设计以使熔体充分混合并达到所需温度Contact material suppliers to get the right screw design information toavoid improper melt mix or
42、 overheating that leads to material degradation.联系厂商取得正确的螺杆设计尺寸，避免熔体不适当的混合或过热导致材料降解。Adjust molding conditionsReduce the barrel temperature and nozzle temperature.Reduce the barrel temperature and nozzle temperature.减少料筒和喷嘴温度减少料筒和喷嘴温度If the barrel and nozzle temperature are too high,the material in t
43、hebarrel will be overheated,leading to thermal degradation and the colorchange.如果料筒和喷嘴温度过高，料筒内材料将过热，导致降解或颜色变化ReduceReduce thethe backback pressure,pressure,screwscrew rotationrotation speed,speed,oror injectioninjection speed.speed.sincesince shearshear heatingheatingcan result in material degradati
44、on.can result in material degradation.减少背压、螺杆转速、或注射速度，因为剪切热会导致减少背压、螺杆转速、或注射速度，因为剪切热会导致材料降解材料降解Within the limit not to overheat the material,increase melt temperature,moldWithin the limit not to overheat the material,increase melt temperature,moldtemperature or injection pressure if the weld line has
45、 a tendency to crack.See fortemperature or injection pressure if the weld line has a tendency to crack.See formoremore information.information.若材料结合线太弱，在材料过热极限范围内增加熔体温度，模具温度或注射若材料结合线太弱，在材料过热极限范围内增加熔体温度，模具温度或注射压力压力Burn marksBurn marksWhat is a burn markWhat is a burn markBurn marks are small,dark or
46、black spots that appear near the end ofBurn marks are small,dark or black spots that appear near the end ofthe flow path of a molded part or in the blind area where the air trapthe flow path of a molded part or in the blind area where the air trapforms.forms.烧焦是小，暗或黑色斑点出现在成型零件的流动末端或形成困气的盲点区域。FIGURE
47、1.Burn marksCauses of burn marksEntrapped airIf the injection speed or injection pressure is too high,the air trappedin the runner system and cavity cannot be released to the atmospherethrough the venting system properly within a very short filling time.also occur in improperly vented systems when r
48、ace-tracking behavior issignificant.Consequently,the air will be compressed,resulting in a veryhigh pressure and temperature,and which will cause the polymer to degradeon the surface near the end of the flow path or the blind area.如果注射速度或注射压力太高，在较短的注射时间下，流道或型腔内的气体无法通过排气系统释放到空气当中。跑马场效应较为严重时，不合理的排气系统的
49、设计奖产生困气。所以空气将被压缩，导致压力和温度增大，这会引起流动末端或盲点区域的制品表面塑料降解。Material degradationBurn marks can also result from the degraded(charred)materials beingcarried downstream and then appearing on the surface of the molded partor near the venting areas.Material degradation is caused by:烧焦也有可能是因为已经降解的材料被带到下游并出现在成型零件靠近
50、排气区域，材料降解原因：High melt temperature?High melt temperature?Excessive melt temperature can be caused by improper barrel temperaturesetting,a broken thermocouple,or a malfunctioning temperaturecontroller.熔体过热是由于不适当的料筒温度的设定、损坏的热电偶或温控器失灵引起的High screw rotation speed?High screw rotation speed?If the screw sp