注塑完整版.ppt

1、射出成形問題 解決方法,技術,Application Guide,2,射出成形過程,1. 將材料餵入成形機的料筒內,2.材料靠著旋轉的螺桿達到輸送熔融和混煉,此時料管同時對材料 進行加熱,3. 熔融的材料在高壓之下射入模腔內,4. 成品從模具中冷卻後才拿出,5. 成品拿出後,再進行下一次的射出成形,3,射出成形條件,料管溫度 / 模具溫度 / 烘料溫度,射出速度 / 螺桿轉速,射出壓力 / 保壓 / 背壓,計量 / 保壓切換點 / 鬆退 / 殘量,射出 / 保壓時間,冷卻時間,速度,壓力,位置,時間,溫度,Pressure,條件,4,最初成形條件的設定方法,1.溫度 低熔融溫度(避免材料裂解,

2、降低成形時間),2.壓力 低壓射出,低保壓與低背壓(避免過度填充損傷模具),3.合模壓力 大一點 (避免模具撐開),4.速度 射速 慢 (避免填充) 螺桿轉速 慢 模具開與關 慢 (避免損傷模具) 計量 小 (避免過度填充),5.時間 射出-保壓 長 ( 確定澆口已封閉) 冷卻 長,5,多段式射出成形理論與應用,控制射出速度的第一段,第二段,第三段(成品表皮)是會影響成品的外觀,控制保壓在第四段,第五段,第六段(成品表皮)是會影響成品的功能特性,6,射出速度位置圖,1. 用中高速 2. 用低速避免靠近澆口位置處有噴流痕和銀線 3. 用高速避免流痕和結合線 4.用中低速避免瓦斯氣.毛邊,且易於切

3、換到保壓,7,保壓位置圖,1.用低壓避免毛邊 2.用高壓避免縮水與尺寸變小 3.用低壓避免殘留應力,如果用低壓時會產生下列情況: 短射 縮水 尺寸變小,如果用高壓時會產生下列情況: 毛邊 翹曲 尺寸變大 龜裂 殘餘應力 脫模 問題,8,模穴壓力與時間曲線圖,9,模穴內壓曲線圖,縮不同的軸向螺桿移動速度造成在壓階段明顯的壓力變化,高的模具溫度可以改善模具內的壓力傳遞,在冷卻階段中,澆口的設計對保壓壓力有明顯的影響,模穴內介於接近澆口處及接近流徑末端處也有明顯壓力差,Vs1 Vs2 Vs3 Vs:軸向螺桿速度,10,從射出保壓階段切換點位置對模穴壓力曲線的影響圖,11,Black spot, co

4、ntamination/黑點,material burning in injection cylinder - Continuos black spot by long residence and burning in damaged screw and barrel - Black spot by partial over-heating in damaged screw head - Black spot by long time machine stop in state of heating of the injection cylinder - Black spot by Burne

5、d Material in Nozzle part,Contamination - Small metal pieces by damaged screw and barrel - Contamination in surface of the material bag on feeding to Hopper and silo - Contamination of string and slice in opening the bag - Contaminated air in Auto feeding,Insufficiently dispersed pigment,Degradation

6、 of flame retardant and stabilizing additives,12,Black spot, Contamination,Material Burning in Injection Cylinder - Continuous black spot by long residence and burning in damaged screw and barrel - Black spot by partial over-heating in damaged screw head - Black spot by long time machine stop in sta

7、te of heating of the injection cylinder - Black spot by Burned Material in Nozzle part,13,Black spot, Contamination,Design Guide for material feeding block in Injection Molding Machine,14,Black Streak/黑紋,15,Silver streak/銀線,16,Weld line/結合線,17,Weld line/結合線,Occur when two or more flow paths meet dur

8、ing the filling process (塑膠充填時, 兩道以上塑膠流遇上時就會發生),18,Weld line/結合線,Welds Strength, Chemical resistance and Appearance (結合強度, 耐化學性與外觀表現),-are influenced by /由以下因素所影響,Material selection 材料選擇,Processing Conditions 成形條件,Mold design 模具設計,Part design 成品設計,Weld (融合),19,Weld line /結合線,在結合線的區域是物性最脆弱的地方,-造成原因,不

9、完整的分子結合與擴散,冷卻時分子的配向不規則,在結合的表面有V字型的凹陷存在,在結合面有微小的氣孔與相異材質的存在,20,Weld line /結合線,Molecular diffusion and entanglement/ 分子的擴散與分佈,No diffusion (無擴散),Partial diffusion (部份擴散),Complete diffusion (完全擴散),21,Weld line /結合線,Frozen-in Fiber orientation/ 纖維分佈,Weld line strengths for fiber reinforced polymers can b

10、e low for a number of reasons including unfavorable fiber orientation at the weld interface due to the fountain like flow behavior of the flow front. (纖維強化塑膠可能會因結合介面纖維分散的不理想, 而造成結合線的強度更弱),Weld strength retention problem may be most severe for long fiber reinforced thermoplastic materials (長纖熱塑形塑膠更易造

11、成結合線強度殘留問題),22,Weld line /結合線,V-notch shape of Weld line (結合線的V 型缺口),23,Design guide - Weld Lines (結合線),Weld vanishing angle (結合消失角度),Weld lines tend to disappear at a “vanishing angle” reaches 120oto 150o depending on the material (結合消失角度視材料而定, 一般以120o 到150o 為宜),Adapted from Robert A, Malloy . Plas

12、tic Part Design for Injection Molding (1994),24,Weld line /結合線,Weld strength depending on the size/shape or the number of core (結合線強度視模穴的大小, 形狀和數量決定),Weld strengths tend to decrease as the number of flow stream divisions and recombination increases (塑膠流分流愈多, 則結合線強度愈弱),(particular problem for grill t

13、ype structure) (網狀結構的衍生問題),(1) (2) (3) (4) (5),(1) (2) (3) (4) (5),25,Design guide - Weld Lines (結合線),Improving Weld Performance and Appearance (結合線外觀和強度改善),Add an overflow well adjacent to the weld (增加一個溢流井來調整結合線),Butt weld,Weld overflow well (在溢流井處結合),Multiple gating scheme (多點式進澆),Butt weld,26,We

14、ld line /結合線,Improving Weld Performance and Appearance / 結合線的強度和外觀改善,Proper gate runner design 適當的流道澆口設計,Increase Mold temperature 提高模溫,Vacuum venting 逃氣孔改善,Multi-Live Feed injection molding (喂料系統的改善),CAE mold filling simulation (電腦輔助模流分析),27,Ribs / 肋,Guidelines for Rib dimensions: Components wall t

15、hickness:T Draft per side(d):0.5o 1.5o Rib height(H):less than 5T(typically 2.5T3T) Rib spacing(on center):more than (2T3T) Base radius(R):0.25T0.40T Rib thickness(W):0.4T0.8T (less than 0.5T for PC/ABS,0.5T0.7T for ABS),28,Ribs - Ribs with Excessive wall thickness ( 肋 - 肋 & 璧厚設計),29,Boss,A boss wit

16、h outside diameter which is two times the inside diameter is sufficiently strong (boss 的設計外徑應為內徑的兩倍以上, 才有足夠的強度),30,Boss,Gussets are another form of ribbing that can be used to reinforce a side wall of a part or boss 支撐肋的設計亦可強化成品或boss的強度,31,Boss,Boss design with possible sink marks & voids Boss的不良設計會

17、造成成品凹陷和孔洞出現,Improved boss design 改良式boss設計,32,Sink Mark /凹陷痕,Balanced design of Boss/平衡式boss設計,33,Corner ( 轉角),Good design (較佳設計),Incorrect design (不良設計),Generous radius (圓弧半俓) Uniform wall thickness (均一壁厚) Smooth flow transition (流動平順),Stress concentration Sharp flow restriction (流動不順, 應力集中),Non-un

18、iform wall thickness Shrinkage/void/sinks Non-uniform flow (非均一壁厚, 衍生翹曲/ 包封/凹陷/流動不順問題),Non-uniform wall thickness shrinkage/void/sinks Non-uniform flow (非均一壁厚, 衍生翹曲/ 包封/凹陷/流動不順問題),34,Design for Assembly (組裝設計),Improving both product quality and reducing manufacturing cost (改善成品品質和降低生產成本),Press fit a

19、ssembly (扣壓式組合) Self fit assembly - Snap Joint (自動式組合-連接卡筍) Mechanical Fastening techniques Screws (機械固定技術 螺絲) Welding techniques (結合技術) Adhesive bonding (黏著性結合) Solvent bonding (溶劑結合),35,Design for Assembly (組裝設計),Snap Joint assembly (組裝連接卡筍須符合組裝和拆除的需求) satisfy both Design for assembly and Design f

20、or disassembly,Simple & Most versatile means of plastic product assembly 利用簡易而通用的塑膠成品來組裝,Insertion 崁入,Deflection 偏差,Elastic recovery 彈性回覆,R,R,Lead-in angle () 導入角度,36,Snap Fit Assembly (卡筍組裝設計),Snap Joint assembly (連接卡筍設計),y = 0.67 L2/d,y = 1.1 L2/d, = maximum tensile strain (最大張力),Permissible defle

21、ction for the tapered beam is about 60% greater than that of the constant cross section of rectangular beam (對於傾斜式懸臂樑比長方形允許變形度大約大60%),37,Snap Fit Assembly (卡筍組裝設計),Snap Joint assembly (連接卡筍設計),Stress concentration factors show that larger radius values tend to reduce the stress concentration and mol

22、d filling orientation related problems, however, excessive radii can lead to complications due to sinks, voids, shrinkage stress. (較大的半徑設計可以降低應力集中和改良填充的位向分佈，然而 過大的半徑易會造成凹陷、包封和翹曲問題出現。),38,Design for Assembly (組裝設計),Mechanical fastener Screw (螺絲),Screws provide a simple, fast, and effective method of

23、joining similar or dissimilar materials (螺絲可提供一個簡單,快速而有效結合相似或相異材料的方法),Machine screws (I.e. nuts and bolts) ( 機械螺絲螺絲與螺帽) Machine screws with a threaded metal inserts or molded threads ( 機械螺絲可利用成形崁入) Self threading screws (自攻螺絲),39,Design for Assembly (組裝設計),Mechanical fastener Screw (機械式固定螺絲),Machine

24、 screw and bolt (機械螺絲與螺帽) 在底部和頂面表面漂亮的遮斷物 許多部份需要安裝 在安裝中需從頭到尾 需要鎖金屬片以免震鬆 耐久的組裝,Machine screw and insert ( 機械螺絲與嵌入物 ) 一方可有光滑的表面 比較少部份需要安裝 嵌 入物需在成型中或成型後嵌入boss中 需要特別設備來嵌入 持久耐用 適於多次的組裝,Self threading screw and plastic boss ( 自攻螺絲與塑膠boss ) 一方可有光滑的表面 比較少部份需要安裝 在安裝中形成緊密塑膠螺紋 最少設備成本 耐用度有限 重覆安裝可能可以但次數有限,40,Scre

25、w Assembly (螺絲組裝),Self threading screw (自攻螺紋),絲規格大小與boss的設計是依據,螺絲拉拔阻力 鎖牙力要求與崩牙比例 重覆組裝性 力矩保持與震動阻抗 對於boss 組裝的環狀應力 組裝的特性,如以退牙與鎖牙比例,Through clearance boss,Blind pilot Boss (導盲柱),Radial Clearance (園隙),Minor screw (根徑),Major screw (外徑),Thread Depth (牙深),Thread depth (%) Utilized (有效深度),Pilot hole (導孔),41,

26、Design for Assembly (組裝設計),Self threading screw (自攻螺絲),Typical torque vs. turns of engagement behavior for a self threading screw being driven into a plastic boss (自攻螺絲鎖牙到進入塑膠boss的典型力矩與螺絲嚙合轉數圖),42,Screw Assembly(螺絲組裝),Self threading screw (自攻螺紋),Lb,Sink mark(縮水),Shrinkage voids (收縮氣泡),Blind boss (盲b

27、oss),Through boss (普通boss),Self threading Screw (自攻螺絲),The core pins that are used to form the holes in blind bosses should be extended as much as possible to core out excessive material. (core pin在形成盲boss位置時, 應該僅量延伸讓盲boss挖空),43,Screw Assembly (螺絲組裝),Self threading screw (自攻螺紋),Lb=length of hole in

28、the blind boss Lt= length of hole in the through boss (盲boss孔的長度) (普通boss孔的長度),The blind boss core pin length is reduced to minimize the molding problems associated with long, cantilever core pins (盲boss孔的長度要減少, 以降低懸臂樑pin太長而衍生的成形問題),44,Design for Assembly,Self threading screw(自攻螺紋),Torque,Torque-tur

29、n curve for a self threading screw showing poor strip/drive torque ratio (left) and high strip/drive torque ratio (right). 自攻螺絲力矩曲線圖示: 低鬆牙/鎖牙力矩(左圖),高鬆牙/鎖牙力矩(左圖),45,Design for Assembly (組裝設計),Self threading screw (自攻螺紋),Torque (力矩),Turns of engagement (嚙合的轉數),Correct pilot hole diameter (正確導孔半徑),Over

30、sized pilot hole diameter (過大的導孔半徑),Undersized pilot hole diameter (過小的導孔半徑),高鬆牙力 /鎖牙力 比 & 高鬆牙力矩,高鬆牙力 /鎖牙力 比 but 低鬆牙力矩,高鬆牙力矩 But 低鬆牙力 /鎖牙力 比,46,Design for Assembly (組裝設計),Self threading screw (自攻螺紋),0,100,200,300,400,500,0.05,0.06,0.07,0.08,0.09,0.10,0.11,0.12,0.13,0.14,Boss 肉厚(inches),Failure load

31、in tension (lbs) (張力荷重),螺絲拉開,螺絲拉開,螺絲拉開,Boss 崩裂,Boss 崩裂,1.8 轉鎖模力,2.7轉鎖模力,3.6 轉鎖模力,PP共聚塑膠 #6 BT 自攻螺絲 0.114”導孔直徑 (60% 有效深度),Tensile screw pull out results for a type BT screw and a polypropylene boss. (對於BT型螺絲應用到PP塑膠的拉開張力強度圖解),47,Part Ejection - draft angle (成品頂出 設計角度),Cavity (母模),Core (公模),: draft angle (脫模角度) 1/2 1o (1.5 2