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1、从注塑成型问题诊断探讨产品、模具 与工艺设计的优化 Reviewing Part, Mold and Process Design Optimization from the Point of View of Troubleshooting徐昌煜 Charles Hsu 2011年5月15和16日 于广州骏星酒店试模及量产时，经常遭遇的问题包括银纹、波纹、虎 皮纹、流痕、气痕、缩痕、熔接痕、应力痕、黄化、脆裂、 变形、周期时间长 等， 使得材料、能源、机器、设备、时 间、人力及金钱浪费、良率偏低、甚至无法交货。 若无正 本清源之道，只有走上败亡之途。试模和量产中80%的问题源自设计不当，产品、
2、模具 与工艺设计 是救亡图存、反败为胜 的关键。强度、应力、降解与污染 (60分钟)对材料施加外力时，材料产生阻力而变形。 换言之，材 料受外力而在内部积蓄应变能。 在变形的初期，以分子内原 子间的距离变化或分子间距离的变化来应对，之后逐渐无法应 对而发生各种构造变化，如部分分子向外力方向，或分子链从 结晶中拉出等。 这时，部分能量则因材料的粘性效应而变为 热能逃出。 若继续对材料做功，材料则形成新表面以便放掉 能量，这就是破坏，而这时的材料的限界阻力就是强度。强度 Strength外力有: (1)拉伸、(2)压缩、(3)剪、(4)弯曲 和(5)扭转， 这些是 由外力的方向差产生的。外力 Ex
3、ternal Force FF拉伸剪弯曲扭转当外力施加于材料时，材料内部产生一种阻挡这外力的内力。 每单位面积的内力叫做应力。外力F，应力时：A是内力作用面的截面积。材料的强度系以每单位面积可以承受的内力即应力表示。应力和强度 Stress and Strength拉伸应力、拉伸应变和弹性模量where F: tensile force 拉伸 力 A : area where F applies拉伸力所施之面积(紅色) : tensile stress 拉伸应力 : tensile strain 拉伸应变 E: modulus of elasticity 弹性模量 : Poissons rat
4、io 泊松比Fl1d2 d1l2 = (unit lateral contraction)/(unit axial elongation)where F: shear force 剪力 Aacmn: area where F applies 剪力所施之面积: shear stress 剪切应力: shear strain 剪切应变 G: shear modulus 剪切模量剪切应力、剪切应变和剪切模量ccaabd Fmn lrBByxyzydASEC B-Bwhere x : bending stress in the xdirection x 方向弯曲应力 M : bending momen
5、t 弯曲力矩 I : moment of inertia of A withrespect to z axis 惯性力矩 A : cross-sectional area 断面积(断面线处)where E : modulus of elasticity 弹性模量 EI : flexural rigidity of the beam梁之弯曲刚性弯曲应力mn dxxTmndx abc ddcdAr roTorsion and Torque 扭力与转矩 Where G : shear modulus 剪切模量: shear strain 剪切应变 r0 : outside diameter of t
6、he shaft 轴外径 r : dA形心至轴之中心线之距离 : the angle of twist which is proportional to the distance x of the cross-section from the fixed end扭转转角(与断面和固定端的距离x成正比) : = d/dx, the angle of twist per unit length of the shaft 单单位轴长轴长 之扭转转角 T : torque (applied couple) 转矩(所施之力偶): shear stress on dA dA上的剪切应应力: shear s
7、tress at the outer surface of the shaft 轴轴外径表面之剪切应应力 J : polar moment of inertia 极惯惯性力矩mndx abc ddcdAr roTorsion and Torque 扭力与转矩 Residual stress is a process-induced stress, frozen in a molded part. It can be either flow-induced or thermal-induced. Residual stresses affect a part similarly to exter
8、nally applied stresses. If they are strong enough to overcome the structural integrity of the part, the part will warp upon ejection, or later crack, when external service load is applied. Residual stresses are the main cause of part shrinkage and warpage.残余应力是制程中凝固在成型品中的应力。 它可能是流动引起的 或热引起的。 残余应力对产品
9、的影响与外力产生的应力相似。 如 果它们大到足以克服产品结构的完整性，产品在脱模时就会变形， 而在之后受到外力时开裂。 残余应力是收缩翘曲的主因。p. 145,“C-MOLD Design Guide”残余应力 Residual StressThe process conditions and design elements that reduce shear stress during cavity filling will help to reduce flow-induced residual stress. Likewise, those that promote sufficient
10、 packing and uniform mold cooling will reduce thermal-induced residual stress. For fiber-filled materials, those process conditions that promote uniform mechanical properties will reduce thermal-induced residual stress.在型腔充填期间能够减少剪切应力的工艺条件和设计要素可以减少 流动引起的残余应力。 同样地， 举凡促进充分保压和均匀冷却者 可以减少热引起的残余应力。 至于添加纤维
11、的材料，举凡增进机械 性均布者可以减少热引起的残余应力。p. 145,“C-MOLD Design Guide”残余应力 Residual Stress流动引起的残余应力 Flow -induced Residual Stress Unstressed long-chain polymer molecules tend to conform to a random-coil state of equilibrium at temperatures higher than the melt temperature (i.e., in a molten state). During process
12、ing the molecules orient in the direction of flow, as the polymer is sheared and elongated. If solidification occurs before the polymer molecules are fully relaxed to their state of equilibrium, molecular orientation is locked within the molded part. This type of frozen-in stressed state is often re
13、ferred to as flow-induced residual stress.无应力的长链高分子在熔点以上倾向于任意卷曲的平衡状态。 制程中被剪切和拉伸的高分子依流向排列， 如果高分子在充 分松弛前被凝固， 分子排列便被锁在成型品中，此一凝入的 应力就是流动引起的残余应力。p. 145,“C-MOLD Design Guide”Because of the stretched molecular orientation in the direction of flow, it introduces anisotropic, non-uniform shrinkage and mechan
14、ical properties in the directions parallel and perpendicular to the direction of flow.因为伸张的高分子沿流向排列，所以流向和垂直流向的机械性 质不同而收缩率也不同。p. 145,“C-MOLD Design Guide”流动引起的残余应力 Flow -induced Residual Stress热引起的残余应力 Thermal-induced Residual Stress Thermal-induced residual stress occurs due to the following reasons
15、: Material shrinks as the temperature drops from the process settings to the ambient conditions reached when the process is complete. The material elements experience different thermal- mechanical histories (e.g., different cooling rates and packing pressures) as the material solidifies from the mol
16、d wall to the center. 热引起的残余应力的起因如下： 制程从设定温度降到室温时材料收缩。 当材料从模壁向型腔中心固化时，材料单元经历了不同的热力 过程(如不同的冷却率和保压)。p. 147,“C-MOLD Design Guide” Changing pressure, temperature, and molecular and fiber orientation result in variable density and mechanical properties. Certain mold constraints prevent the molded part from shrinking in the planar directions. 改变压力、温度和分子/纤维排列产
