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1、 制图规范 1、所有外发加工图电子文档均采用 AutoCAD R2004 的格式，一般不能将 PRO-E，UG 等三维立体图直接外发加工。 2、层的命名，颜色，线型设置(见附图 1) 全局线型比例：1.00 0 层为轮廓线层；CEN 层为中心线层；DAS 为虚线表示层；DIM 层为尺寸线 层； HAT 层为剖面线层； MOD 变更记录层； NOT 层为技术要求等文字说明层； REF 层为参考物体层； Defpoints 层为基本层，其不打印。 附图 1 3、尺寸标注设置 a、 尺寸界线、尺寸线颜色设置为层的颜色（即 bylayer）;尺寸界线起点距标注点 在打印比例是1:1时设置为0.625,
2、 尺寸界线终点超出尺寸线设置为1.25;尺寸线 箭头设置为实心的，箭头大小在打印比例是 1:1 时设置为 3.0,不设置中心标准。 （见附图 2） 附图 2 b、 文字类型设置为标准，颜色设置为层的颜色，文字高度在打印比例是 1:1 时设 置为 2.5,按比例缩放，文字放置在水平、垂直的中心，字底距尺寸线取（打印 比例是 1:1 时）0.625,线性尺寸之文字与尺寸线队齐,角度尺寸与引线标注之文 字需设置为水平。 （参见附图 3） 附图 3 c、 线性尺寸单位设置为十进制单位，精度设置为 0.00，小数点格式设置为句号， 测量比例如图幅是 1:1 打印时就设置为 1.0，如放大 n 倍就设置为
3、 1/n,如缩小 n 倍就设置为 n；角度尺寸单位设置为十进制角度单位，精度设置为 0.00.（参见 附图 4） 附图 4 4、图框采用公司标准的图框（参见附图 5） ，其版次栏每更改一次需升版，但如是采 用先打样再确认的方式，打样过程中的更改版次不升，但打样图纸需注明是打样图 纸（即每正式发行一次版次需升一次，但打样过程中的更改不升版） ，且每升版一次 其零件的物料编码一般需升版一次（按公司规定执行） 。其材料栏按有关材料标准标 示（冷轧板常用牌号是 SPCC，电解板常用牌号是 SECC，不锈钢板常用牌号是 SUS 304， 镀锌板常用牌号是 SGCC） ,如是金属板材， 其厚度标示小数点后
4、两位 （如 T=1.00） 不再标单位，其默认单位是 mm. 附图 5 5、视图放置全采用第三视角的方式（即右側看到的视图放在右视图） ；尺寸标注须 清晰、明确，方便加工时查找，整个图纸需看上去不零乱，清洁；局部放大图用罗 马字母标示，如 I、II、III、IV、V、VI 等；方向视图用阿拉伯字母表示，如 A、B、 C、D 等；如局部无法清除看到尺寸标注，需用局部放大图标注；如图纸很大时可采 用版块标注方式，即同一功能的放在同一版块标注；功能尺寸如按第 6,7,8 条款未注 公差等级能满足要求就不用标注尺寸公差，如不能满足要求，须标注公差要求；如 未注公差等级能满足功能要求，但仍需品质人员重点
5、控制尺寸，需在尺寸后惙标示 CTF 字样，意思为功能控制尺寸（英文：Control To Function） 。 6、钢板冲压制品如有公差标注，按标注公差范围验收；尺寸未注公差按 GB/T 13914-92 国家标准执行，在同一面的尺寸按 ST4 等级设计与验收，通过折弯，压形 等不在同一平面的按按 FT5 等级设计与验收，通过焊接而成的尺寸按 ST6 或 FT6 等 级设计与验收，角度未注公差按 GB/T 13915-92 国家标准执行，冲裁角度公差按 AT3 级设计及验收，弯曲角度公差按 BT3 级设计及验收。 7、机加件制品如有公差标注，按标注公差范围验收；未注公差按 GB/T 1804
6、-92 国家 标准执行，采用 f 等级(既精密级) 设计与验收。 8、塑胶制品如有公差标注，按标注公差范围验收；未注公差按 SJ/T 10628-1995 国家 标准执行，采用 4 等级设计与验收。 9、每张图纸一般需有技术要求，技术要求放置在 NOTE 层，技术要求应对影响功能 的折弯、压形、焊接等加工做出明确规范，如毛刺方向，压痕等对功能、外观有要 求，也需明确规范。 10、打印时打印机油墨的颜色设置为黑白，一般不采用彩色，打印笔号一般全选 7 号笔，黑色选线宽 0.3,其余颜色一般选 0.18,所有外发图纸须清晰，能全部看清楚为 原则。 11、绘图时比例统一用 1:1，须放大或缩小时要表
7、明。打印图纸时充满打印！ Design for Assembly Cheil Industries Inc. Design Guide For Assembly of Injection Molded Plastic Parts R&D, Application Development Center Last Updated SEP 15 1999Cheil Industries Inc. 2 Assembly techniquesAssembly techniques Improving both product quality and reducing manufacturing cost
8、 ? Press fit assembly ? Self fit assembly ? Mechanical Fastening techniques ? Welding techniques ? Adhesive bonding ? Solvent bonding Design Guide For Assembly of Injection Molded Plastic Parts R&D, Application Development Center Last Updated SEP 15 1999Cheil Industries Inc. 3 Press Fit AssemblyPres
9、s Fit Assembly Simplest means of assembling plastic parts - use Elastic or spring like characteristics of plastics hub shaft Design Guide For Assembly of Injection Molded Plastic Parts R&D, Application Development Center Last Updated SEP 15 1999Cheil Industries Inc. 4 Press Fit AssemblyPress Fit Ass
10、embly Materials consideration 0.01.02.03.04.05.0 Tensile strain (%) Tensile stress X Rigid brittle polymer Design strain may be Manufacturing related tolerance Ductile polymer Large latitude for interference Rigid polymers are too brittle for press fit applications. Ductile polymers are more generou
11、s when considering the effects of manufacturing tolerance. Design Guide For Assembly of Injection Molded Plastic Parts R&D, Application Development Center Last Updated SEP 15 1999Cheil Industries Inc. 5 Press Fit AssemblyPress Fit Assembly Interference for Press fit 0 0.002 0.004 0.006 0.008 0.00.10
12、.20.30.40.50.60.70.80.91.0 Ratio of (Shaft diameter/Hub outside diameter) s/ o Interference limit - I m/m of shaft Interference limits for nylon 66 hub Nylon 66 shaft Steel shaft Room temp. 50 % RH I = (D s)/W (W + h)/Eh +(1- s)/Es where: I = diametrical interference (inch) D = design stress level (
13、lbs/inch2) o = hub outside diameter (inch) s = shaft diameter (inch) Eh = hub modulus (lbs/inch2) Es = shaft modulus (lbs/inch2) h = Poisson s ratio for hub material s = Poissons ratio for shaft material W = 1 + ( s / o)2/1-( s / o)2 The amount of interference for a press fit can be determined using
14、 design equations, or graphs, indicating the maximum recommended interference for a particular material. Design Guide For Assembly of Injection Molded Plastic Parts R&D, Application Development Center Last Updated SEP 15 1999Cheil Industries Inc. 6 Press Fit AssemblyPress Fit Assembly Use of undercu
15、t shaft for press fit hub/shaft assembly s1 s2 i I = s2 - i i s2 s1 Hub is pushed over high spot on shaft during assembly (short time only) Hub reaches final axial location (long term) Design Guide For Assembly of Injection Molded Plastic Parts R&D, Application Development Center Last Updated SEP 15
16、 1999Cheil Industries Inc. 7 Press Fit AssemblyPress Fit Assembly Shaft can be smooth, textured or even knurled Time Slippage torque Time Slippage torque Press fit smooth shaft Press fit knurled or splined shaft s i i s Rate of decrease determined by design stress level and relaxation characteristic
17、s of the hub material Knurled, textured or splined surfaces can result in cold flow and some mechanical interlocking Design Guide For Assembly of Injection Molded Plastic Parts R&D, Application Development Center Last Updated SEP 15 1999Cheil Industries Inc. 8 Snap Fit AssemblySnap Fit Assembly Snap
18、 Joint assembly satisfy both Design for assembly and Design for disassembly Simple & Most versatile means of plastic product assembly Insertion Deflection Elastic recovery R R Lead-in angle () Design Guide For Assembly of Injection Molded Plastic Parts R&D, Application Development Center Last Update
19、d SEP 15 1999Cheil Industries Inc. 9 Snap Fit AssemblySnap Fit Assembly Snap Joint assembly L R d y Cantilever snap beam constant rectangular cross section dd/2 Tapered cantilever snap beam decreasing depth from d to d/2 y = 0.67 L2/d y = 1.1 L2/d = maximum tensile strain Permissible deflection for
20、the tapered beam is about 60% greater than that of the constant cross section of rectangular beam Design Guide For Assembly of Injection Molded Plastic Parts R&D, Application Development Center Last Updated SEP 15 1999Cheil Industries Inc. 10 Snap Fit AssemblySnap Fit Assembly Snap Joint assembly St
21、ress concentration at the corner Deflection Neutral axis + - R T Applied Load 00.20.40.60.81.01.21.4 1.0 1.5 2.0 2.5 3.5 3.0 Radius/wall thickness (R/T) Stress concentration factor Stress concentration factors show that larger radius values tend to reduce the stress concentration and mold filling or
22、ientation related problems, however, excessive radii can lead to complications due to sinks, voids, shrinkage stress. Design Guide For Assembly of Injection Molded Plastic Parts R&D, Application Development Center Last Updated SEP 15 1999Cheil Industries Inc. 11 Mechanical Fastening TechniquesMechan
23、ical Fastening Techniques Mechanical fastener - Screw Screws provide a simple, fast, and effective method of joining similar or dissimilar materials ?Machine screws (I.e. nuts and bolts) ?Machine screws with a threaded metal inserts or molded threads ?Self threading screws Design Guide For Assembly
24、of Injection Molded Plastic Parts R&D, Application Development Center Last Updated SEP 15 1999Cheil Industries Inc. 12 Mechanical Fastening TechniquesMechanical Fastening Techniques Mechanical fastener - Screw Machine screw and bolt ?Esthetic interruption on both top and bottom surfaces ?Many parts
25、required for assembly ?Access to both top and bottom of the part is required during assembly ?Need locking hardware to avoid vibration loosening ?Durable assembly Machine screw and insert ?One smooth surface obtained ?Fewer parts required for assembly ?Internally threaded insert must be inserted int
26、o boss during or after molding ?Requires special equipment/tooling for insert ?Good overall durability ?Suitable for repeated assembly Self threading screw and plastic boss ?One smooth surface obtained ?Minimum number of parts required for assembly ?Mating plastic threads formed during assembly ?Min
27、imum fastener and equipment cost ?Limited durability (mating thread is plastic) ?Repeated assembly possible but limited Design Guide For Assembly of Injection Molded Plastic Parts R&D, Application Development Center Last Updated SEP 15 1999Cheil Industries Inc. 13 Mechanical Fastening TechniquesMech
28、anical Fastening Techniques Self threading screw The screw type, size, and the design of the boss system are dependent upon ? Screw pull out resistance ? Clamp load requirement and decay rate ? Repeated assembly requirements ? Torque retention and vibration resistance ? Hoop stresses for the boss as
29、sembly ? Assembly characteristics such as the strip to drive torque ratio Through clearance boss Blind pilot boss Radial clearance Minor screw Major screw Thread depth Thread depth (%) Utilized Pilot hole Design Guide For Assembly of Injection Molded Plastic Parts R&D, Application Development Center
30、 Last Updated SEP 15 1999Cheil Industries Inc. 14 Mechanical Fastening TechniquesMechanical Fastening Techniques Self threading screw Screw engagement (turns) Torque Start Drive torque Maximum drive torque (clamping starts) Failure (destruction) torque: stripping. Yield Recommended tightening torque
31、 Prestress (clamping) torque Typical torque vs. turns of engagement behavior for a self threading screw being driven into a plastic boss Design Guide For Assembly of Injection Molded Plastic Parts R&D, Application Development Center Last Updated SEP 15 1999Cheil Industries Inc. 15 Mechanical Fasteni
32、ng TechniquesMechanical Fastening Techniques Self threading screw Lb Lb Sink mark Shrinkage voids Blind boss Through boss Self threading screw 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. Design Guide For Assembl
33、y of Injection Molded Plastic Parts R&D, Application Development Center Last Updated SEP 15 1999Cheil Industries Inc. 16 Mechanical Fastening TechniquesMechanical Fastening Techniques Self threading screw Lb Lt Lb Lt Lb=length of hole in the blind boss Lt= length of hole in the through boss The blin
34、d boss core pin length is reduced to minimize the molding problems associated with long, cantilever core pins Design Guide For Assembly of Injection Molded Plastic Parts R&D, Application Development Center Last Updated SEP 15 1999Cheil Industries Inc. 17 Mechanical Fastening TechniquesMechanical Fas
35、tening Techniques Self threading screw Screw engagement (turns) Torque Start Drive torque Maximum drive torque (clamping starts) Failure (destruction) torque: stripping. Wide separation (reduces risk of stripping) Stripping torque Maximum drive torque = 4:1 Torque Screw engagement (turns) Start Driv
36、e torque Maximum drive torque (clamping starts) Failure (destruction) torque: stripping. Limited separation Stripping torque Maximum drive torque = 2:1 Low strip/drive ratio Torque-turn curve for a self threading screw showing poor strip/drive torque ratio (left) and high strip/drive torque ratio (r
37、ight). Design Guide For Assembly of Injection Molded Plastic Parts R&D, Application Development Center Last Updated SEP 15 1999Cheil Industries Inc. 18 Mechanical Fastening TechniquesMechanical Fastening Techniques Self threading screw Torque Turns of engagement Correct pilot hole diameter Oversized
38、 pilot hole diameter Undersized pilot hole diameter High strip / drive ratio and high strip torque High strip / drive ratio but low strip torque High strip torque but low strip / drive ratio The boss pilot hole diameter has a significant influence on both maximum drive torque and strip / drive torqu
39、e ratio. Low drive torque and high strip /drive torque ratios are most desirable as this limits the potential for failure during the initial or subsequent assembly procedures. Design Guide For Assembly of Injection Molded Plastic Parts R&D, Application Development Center Last Updated SEP 15 1999Chei
40、l Industries Inc. 19 Mechanical Fastening TechniquesMechanical Fastening Techniques Self threading screw 0 100 200 300 400 500 0.050.060.070.080.090.100.110.120.130.14 Boss wall thickness (inches) Failure load in tension (lbs) Screw pulls out Screw pulls out Screw pulls out Boss tensile failure Boss
41、 tensile failure 1.8 turns engagement 2.7 turns engagement 3.6 turns engagement Polypropylene homopolymer #6 BT thread cutting screw 0.114 inch pilot hole diameter (60% thread depth) Tensile screw pull out results for a type BT screw and a polypropylene boss. Design Guide For Assembly of Injection M
42、olded Plastic Parts R&D, Application Development Center Last Updated SEP 15 1999Cheil Industries Inc. 20 Welding TechniquesWelding Techniques Molecular diffusion and entanglement Upper part Lower part Weld interface Welded thermoplastic partsEntangled polymer chains at the weld interface Molecular d
43、iffusion and entanglement must occur during welding. The molecular mobility can be the result of solvent swelling or thermal energy ?Ultrasonic welding- High frequency vibration , intermolecular friction ?Vibration welding- surface friction and/or viscous dissipation ?Spin(rotational) welding- interfacial friction ?Hot tool welding- heat conduction ?Induction welding- heating by high frequency electromagnetic field ?Resistance welding- heat conduction by conductive wire ?Hot gas welding- use hot air or nitrogen ?Extr