塑胶成型不良问题及对策处理.doc

Air traps 困氣What is an air trap? An air trap is air that is caught inside the mold cavity. It becomes trapped by converging polymer melt fronts or because it failed to escape from the mold vents, or mold inserts, which also act as vents. Air-trap locations are usually in areas that fill last. Lack of vents or undersized vents in these last-to-fill areas are a common cause of air traps and the resulting defects. Another common cause is race-tracking (the tendency of polymer melt to flow preferentially in thicker sections), caused by a large thickness ratio. 困氣是氣體存在于模具型腔內無法排出，困氣會形成氣孔是其聚集在熔體前端或未從模具排氣孔以及鑲件排出。困氣通常發生在最終填充位置。在填充末端缺少排氣孔或排氣孔太小都會引起空位造成制品缺陷。另一個較為普遍的原因是跑馬場效應（聚合物熔體有優先向肉厚方向流動的趨勢），是由于壁厚突變引起的。FIGURE 1. Air trap locations indicated by the computer-predicted melt-front advancements. (To replay the animation, click Replay) Problems caused by air traps Entrapped air will result in voids and bubbles inside the molded part, a short shot (incomplete fill), or surface defects such as blemishes or burn marks. To eliminate air traps, you can modify the filling pattern by reducing the injection speed, enlarging venting, or placing proper venting in the cavity. 困氣將引起成型制品內部空位和氣泡，短射（澆不足），或表面缺陷如污痕或燒焦。可以利用改善成型條件來解決困氣問題，如減少注射速度，擴大排氣孔，或者適當位置開設排氣孔。In the figure below, an air trap results from race-tracking in a part with a large thickness ratio. In this case, the entrapped air can be vented by changing the thickness ratio or by placing a vent (e.g., via an ejector pin) at the air trap location.以下的例子中，困氣是由于壁厚突變產生的跑馬場效應引起的。困氣可以由減小壁厚變化率或者適當位置開設排氣孔消除。Remedies 補救措施Alter the part design改變零件的設計Reduce the thickness ratio.減少壁厚變化This will minimize the race-tracking effect of polymer melt.可以減少聚合物熔體的跑馬場效應。Alter the mold design改變模具的設計Pay close attention to the proper placement of your vents.密切關注開設排氣孔位置Place vents in the areas that fill last.在熔體流動末端開設排氣槽Vents are typically positioned at discontinuities of mold material, such as at parting surfaces, between the insert and mold wall, at ejector pins, and at mold slides.排氣孔通常開設在模具中斷處，比如分型面、鑲件與模具間隙、頂針、滑塊等。Re-design the gate and delivery system.重新設計澆口和澆注系統Changing the delivery system can alter the filling pattern in such a way that the last-to-fill areas are located at the proper venting locations.改變澆筑系統可以改變充填形式使得流動末端布置好排氣。Make sure the vent size is large enough so that the air present in the cavity can escape during injection.排氣槽尺寸應足夠大以使得氣體可以在充填過程中排出。Be careful, however, that the vent is not so large that it causes flash at the edge of the molding. The recommended vent size is 0.025 mm (0.001 inch) for crystalline polymers, and 0.038 mm (0.0015 inch) for amorphous polymers.但是，排氣槽不能太大防止制品產生飛邊。對于結晶型塑料，排氣槽應小于0.025mm，不定形塑料應小于0.038mm。Adjust the molding conditions改善填充條件Reduce the injection speed.減少注射速度High injection speeds can lead to jetting, which causes air to become entrapped in the part. Lowering the injection speed will give the air displaced by the melt sufficient time to escape from the vents.速度過高會引起噴射，這會使氣體無法逃脫。較低的注射速度可以使氣體有充足的時間從排氣槽排出。Black specks/black streaks黑斑和黑痕What are black specks and black streaks? Black specks and black streaks are dark spots or dark streaks found on the surface or throughout a molded part. Brown specks or streaks refer to the same type of defect, except the burning or discoloration is not as severe.黑斑和黑痕是出現于制品表面或貫穿在整個零件內部的黑點或黑條紋。它們都是同種形式的缺陷，是不太嚴重的燒焦或色變。Causes of black specks/black streaks Black 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過熱或樹脂被污染而引起的。Material degradation Overheated materials can degrade and lead to black streaks. Material that stays in the nicked rough surfaces of the barrel wall and screw surfaces for a prolonged period of time after heating will char and degrade, resulting in the defect. 材料過熱會降解導致黑痕，材料在加熱過程中停留在粗糙的料筒和螺桿表面的時間過長會燒焦并講解，導致產品缺陷。Material contamination Contaminants in the air or material, such as dirty regrind, foreign material, different color material, or a lower melt-temperature material, are what most often lead to black specks and black streaks. Airborne dirt can also cause dark spots on the surface of a molded part.在空氣中或被其它材料污染，比如被污染的外來料，不同顏色的材料，低熔點材料，都通常引起黑斑和黑痕的原因。空氣中的粉塵也是會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 Brittleness 脆化 Burn marks 燒焦 Discoloration 色變Remedies Handle the material carefully小心使用材料Make sure no contaminated materials, such as dirty regrind, are blended into the original material.確保沒有被污染的材料，比如臟的再生料加入到原材料當中。Put the cover on the hopper and all bins of material. Airborne dirt can contaminate the original material, leading to black spots.將容器蓋上蓋子，空氣中的灰塵會污染原料導致黑斑。Alter the mold design改變模具設計Clean the ejectors and slides. The streaks could be caused by the grease or lubricants on the slides or ejectors.清潔頂針和滑塊，條紋可以由滑塊或頂針上的油脂或潤滑油引起。Improve the venting system. If the black specks are found at the end of flow paths or blind spots, they are likely caused by a poor venting system. Compressed air trapped in the cavity is sometimes ignited, leading to the defect.改善排氣系統，如果在流動末端或盲點發現有黑斑，有可能是由于排氣不良引起的。被壓縮的型腔內的氣體有時會被點燃，造成產品缺陷。Clean or polish any nicked surface on the runner system to keep dirt from lodging in these areas.Clean the mold before molding.清潔或拋光流道內的粗糙表面，使污垢遠離這些區域。并在成型前進行清潔。Select a proper machine 選用適合的機臺Size a proper injection machine for a specific mold.The typical shot size should be between 20 and 80 percent of machine injection capacity. For temperature-sensitive materials, the range should be narrowed down more. Plastics simulation software can help you select the right size injection machine for a specific mold. This will help avoid resin remaining in the heated barrel for prolonged periods of time.注射量應為注射機最大注射量的20%80%，對于溫度敏感型材料，變化范圍應該更窄些，塑膠仿真軟件可以為成型模具選擇適合的注射機。有助于避免塑料在加熱料筒中停留時間過長。Check for scratched or dented barrel/screw surfaces that trap material.檢驗刮傷或凹陷的料筒或螺桿表面是否留有材料This could lead to the material becoming overheated or burned.殘存的材料將會過熱或燒焦Check for local overheating by a run-away heater band or a malfunctioning temperature controller.檢驗是否因料筒加熱器脫離或溫度控制器的故障引起局部過熱。Adjust the molding conditions調節成型條件Lower the barrel and nozzle temperature.降低料筒或噴嘴溫度Material degradation can result from a high melt temperature. 材料講解會由熔體溫度過高引起Purge and clean the injection unit.清潔注射裝置The black streaks might be caused by contamination from the barrel wall or the screw surface. When molding with two materials, after switching from one material to the other, the old material might not be purged from the barrel completely. This could generate defects during the molding of the second material.黑痕可能會由于被污染的料筒壁或螺桿表面引起。當注射兩種不同材料并從一種材料轉換成另一種材料時，舊材料可能沒有被完全清洗，在成型第二種材料時就會產生缺陷。Avoid recycling rejected parts with black specks and black streaks.避免回收使用有黑痕或黑斑的不良制品。Recycling such parts could lead to further contamination, unless theyll be used for parts that are in black or for which such defects are acceptable.回收利用該種類型的制品會導致更深一層的污染，除非它們是用于黑色或該缺陷是可以接受的零件。Brittleness What is brittleness? 脆化A brittle molded part has a tendency to break or crack. Brittleness results from material degradation leading to shorter molecular chain length ( thus lower molecular weight). As a result, the physical integrity of the part is substantially less than the specification. 脆性零件有斷裂或爆裂的傾向。脆化是由于材料降解導致分析鏈縮短（可減輕分子量）造成的。結果，零件的物理性能達不到要求。FIGURE 1. Degraded part tends to be brittle and break easily Causes of brittleness Brittleness is caused by material degradation due to 脆化是由于材料講解引起的： Improper drying conditions 不合理的干燥條件 Improper temperature setting 不合理的溫度設定 Improper runner system and gate design 不合理的流道系統和澆口的設定 Improper screw design 不合理的螺桿設計 Weld line weakness 結合線較弱Other defects resulting from the same causes 相同的原因會導致以下缺陷 Black specks/black streaks 黑斑或黑痕 Burn marks 燒焦 Discoloration 色變Remedies Adjust the material preparationSet proper drying conditions before molding. 成型前設置適合的干燥條件Brittleness can be caused by excessive drying time or drying temperature such as at full heat for several days. Excessive drying either drives off volatiles in the plastic, making it more sensitive to processing, or degrades the material by reducing the molecular weight. Material suppliers can provide optimum drying conditions for the specific materials.脆化可能是由于干燥時間過久或干燥溫度過高引起的。過量的干燥不僅會使塑料不穩定，造成對工藝條件較為敏感，而且會使分子量減少造成材料降解。材料供應商會對各種材料提供適合的干燥條件。Reduce regrind material. The brittleness could be caused by too much reground material added into the original virgin material.脆化也有可能是因為太多再生料加入到原料當中。Change to a high-strength material since low-strength materials tend to become more brittle if processed improperly.在工藝條件不適當的條件下，如果 強度材料容易脆化，則改用高強度材料Alter the mold designEnlarge the sprue, runner, and/or gate.增大主流道、分流道、澆口。Restrictive sprue, runner, gate, or even part design could cause excessive shear heating that aggravates an already overheated material, causing material degradation.主流道、分流道和澆口甚至制品過小都會產生大量的剪切熱，使材料的過熱加重，引起材料降解。Select a proper machine/machine componentGet a better screw design for the material youre using to achieve a better mixed melt temperature.改善螺桿設計以使熔體充分混合并達到所需溫度Contact material suppliers to get the right screw design information to avoid improper melt mix or overheating that leads to material degradation.聯系廠商取得正確的螺桿設計尺寸，避免熔體不適當的混合或過熱導致材料降解。Adjust molding conditionsReduce the barrel temperature and nozzle temperature.減少料筒和噴嘴溫度If the barrel and nozzle temperature are too high, the material in the barrel will be overheated, leading to thermal degradation and the color change.如果料筒和噴嘴溫度過高，料筒內材料將過熱，導致降解或顏色變化Reduce the back pressure, screw rotation speed, or injection speed. since shear heating can result in material degradation.減少背壓、螺桿轉速、或注射速度，因為剪切熱會導致材料降解Within the limit not to overheat the material, increase melt temperature, mold temperature or injection pressure if the weld line has a tendency to crack. See Weld lines and meld lines for more information.若材料結合線太弱，在材料過熱極限范圍內增加熔體溫度，模具溫度或注射壓力Burn marks What is a burn mark? Burn marks are small, dark or black spots that appear near the end of the flow path of a molded part or in the blind area where the air trap forms. 燒焦是小，暗或黑色斑點出現在成型零件的流動末端或形成困氣的盲點區域。FIGURE 1. Burn marks Causes of burn marks Entrapped air If the injection speed or injection pressure is too high, the air trapped in the runner system and cavity cannot be released to the atmosphere through the venting system properly within a very short filling time. Air traps also occur in improperly vented systems when race-tracking behavior is significant. Consequently, the air will be compressed, resulting in a very high pressure and temperature, and which will cause the polymer to degrade on the surface near the end of the flow path or the blind area. 如果注射速度或注射壓力太高，在較短的注射時間下，流道或型腔內的氣體無法通過排氣系統釋放到空氣當中。跑馬場效應較為嚴重時，不合理的排氣系統的設計獎產生困氣。所以空氣將被壓縮，導致壓力和溫度增大，這會引起流動末端或盲點區域的制品表面塑料降解。Material degradation Burn marks can also result from the degraded (charred) materials being carried downstream and then appearing on the surface of the molded part or near the venting areas. Material degradation is caused by: 燒焦也有可能是因為已經降解的材料被帶到下游并出現在成型零件靠近排氣區域，材料降解原因：High melt temperature Excessive melt temperature can be caused by improper barrel temperature setting, a broken thermocouple, or a malfunctioning temperature controller. 熔體過熱是由于不適當的料筒溫度的設定、損壞的熱電偶或溫控器失靈引起的High screw rotation speed If the screw speed is too high during the plasticization period, it will create too much frictional heat, which could degrade the material. 在熔體塑化階段，如果螺桿的速度過高，會產生較多的剪切熱，這會導致材料降解。Restrictive flow path When the melt flows through restrictive nozzle, runner, gate, or part sections, it creates a lot of shear (frictional) heat, which could degrade the material. 當熔體流經限制性的噴嘴、流道、澆口或制品截面時，將產生大量的剪切熱，導致材料降解。Other defects resulting from the same causes Black specks/black streaks Brittleness Discoloration Remedies Alter the mold design改變模具設計Place an adequate venting system throughout the mold to help vent out the entrapped air.開設適當的排氣系統。Vents are especially important near the end of the flow path and in the blind area. The recommended venting size is 0.025 mm (0.001 inches) for crystalline polymers, and 0.038 mm (0.0015 inches) for amorphous polymers.流動末端和盲點區域的排氣很重要，結晶性材料推薦排氣槽尺寸為0.025，不定塑料為0.038。Enlarge the sprue, runner, and/or gate.增大主流道、分流道或澆口Restrictive sprue, runner, gate, or even part design could cause excessive shear heating that aggravates an already overheated material, causing material degradation.Adjust the molding conditions 調節注射條件Reduce the likelihood of burn marks by avoiding excessive melt temperatures during the molding process:避免成型過程中熔體溫度過高，減少燒焦的可能性。Reduce the injection pressure.減少射壓Reduce the injection speed.減少注射速度Reduce the screw rotation speed.減少螺桿轉速Decrease the barrel temperature.減少料筒溫度Check the band heaters on the barrel and nozzle, and calibrate the thermocouple.減少料筒、噴嘴的加熱器是否損壞，校準熱電偶Delamination What is delamination? 層脫Delamination (sometimes called lamination or layering) is a defect in which the surface of a molded part can be peeled off layer by layer. 層脫（有時叫做層裂或分層）是成型制品表面一層一層剝落。FIGURE 1. Delamination causes layer-wise peel-off on the surface of a molded part Causes of delamination 層脫原因Delamination can be caused by several factors, including: Incompatible materials blended together 不相容的材料混合在一起 Too much mold release agent being used during the molding process 注射成型過程使用過多的脫模劑。 Low melt temperature in the cavity 型腔內的熔體溫度過低 Excessive moisture 水分過多 Sharp corners at the gate and runner 澆口或流道拐角處有尖角Remedies Change the material preparation 做好材料的成型前準備Avoid using foreign material or contaminated regrind material in the molding process.避免使用外來料或受污染的再生料。Alter the mold design更改模具設計Smooth all of the corners at the gate and runner.在澆口和流道拐角處倒圓角Sharp corners can tear apart melt flow and cause lamination.尖角會將熔體流動分離引起分層Adjust the molding conditions改善成型條件Avoid using excessive mold release agent to fix the de-molding problem.避免使用過量脫模劑來解決脫模問題Delamination can be caused by excessive use of mold release agent. You should repair the ejection system or other problems to eliminate the difficulty of de-molding instead of over-using the mold release agent.使用過量脫模劑可以導致層脫。可以通過修整脫模機構或其他可以消除脫模困難問題的方法來代替使用過多脫模劑Follow the pre-dry instructions for the specific material and pre-dry the material properly before molding.根據材料的干燥說明，在成型前對材料進行充分的預干燥。Excessive moisture heats up and forms steam, which results in lamination on the surface.大量水分蒸發并形成蒸汽，會導致表面分層。Increase the barrel temperature and mold temperature.增大料筒和模具溫度If the melt temperature is too low, layers of material are formed because they cant bond to each other. When ejected or subjected to stress, they separate from each other.如果熔體溫度過低，材料因不能結合而分層，當頂出或承受應力時，材料就會脫離。Dimensional variation What is dimensional variation? Dimensional variation is a defect characterized by the molded part dimension varying from batch to batch or from shot to shot while the machine settings remain the same.尺寸變化是在機臺設置參數相同的情況下，成型制品尺寸按批次或件數變化。FIGURE 1. Dimensional variation is an unexpected change of part dimension Causes of dimensional variation Dimensional variation can be caused by 尺寸變化是由于： Unstable machine control 機臺控制不穩定 A narrow process window成型窗口狹窄 Improper process conditions settings 成型條件設計不合理 A broken check ring (within the injection unit) 計量單位不準確 Unstable material property 材料性能不穩定Remedies Improve the material preparation改善成型前準備Contact the material vendor and change the material lot if the material has patch-to-patch variation.聯系材料供應商更換材料批次如果材料按批次變化Pre-dry the material before molding if the material is too wet.如果材料太潮，進行成型前預干燥Limit the percentage of regrind material added to the origin material.限制回收料加入到原料的比例The irregular particle size can cause different levels of mixed melt material, and lead to unstable molded part dimensional variation.不規則的顆粒尺寸會引起材料混合程度不一樣，并導致不穩定的零件尺寸變化Change a mold design/componentFix or adjust the ejection system if the molded part is bowed or distorted during ejection.Design a proper runner and gate system for a specific mold and material.安裝或調整頂出機構如果制品在頂出過程中發生彎曲或扭曲Use plastic injection molding simulation software to optimize the runner system dimension to assure a smooth melt flow into the cavity使用塑膠注射成型仿真軟件優化流道系統尺寸確保熔體進入型腔流暢。Change a machine component更換機器元件Replace the check ring if it is broken or worn out.更換損壞或磨損的報警器Replace heater bands or the thermocouple if it is out of order and causes unstable melt flow.更換加熱器或熱電偶如果其罷工和導致熔體流動不穩定Adjust the molding conditions調節成型條件Increase the injection and packing pressure增加注射壓力和保壓壓力Make sure enough material is delivered into the cavity during the filling and packing stages.確保材料在充型和保壓階段充分進入模具型腔Increase the injection and packing time to be sure enough material is delivered into the cavity during filling and packing stages.增大注射壓力和保壓壓力以確保充型和保壓階段充分進入模具型腔Make sure the mold temperature is even by checking the cooling system.檢查冷卻系統確保模具溫度均勻Set-up screw metering and injection stroke, screw rotation speed, and back pressure properly so that they fall within the process window.設置螺桿計量和注射位置、螺桿轉速和背壓并使它們在成型窗口內Discoloration 色變What is discoloration? Discoloration is a color defect characterized by a molded parts color having changed from the original material color. 色變是塑料成型制品顏色上區別于原材料的變化Causes of discoloration This defect can be caused by either material degradation or contamination from the following problems: 色變是由材料降解或受污染引起的。有以下問題產生 The material staying in the barrel too long. 材料停留于料筒時間太長 The barrel temperature being too high, causing the color to change. 料筒溫度太高，致使顏色變化 Contamination caused by reground material, different color material,