塑料注射成型工艺基础

内容提要 注射工艺过程 注射压力 填充模式 浇注系统与流道平衡 冷却系统 应力、收缩与翘曲 常见的注塑缺陷 CAE软件应用指南

Co-injection molding

Fusible core injection molding

Gas-assisted injection molding

Injection-compression molding

Lamellar (microlayer) injection molding

Live-feed injection molding

Low-pressure injection molding

Push-pull injection molding

Structural foam injection molding

Process cycle

Importance of process conditions

Resin data table Generic Name Melt Temperature (C/F) Mold Temperature (C/F)    Min.  Rec.  Max.  ABS  200/392  230/446  280/536  25/77  50/122  80/176  PA 6  255/491  300/572  70/158  85/185  110/230  PC  260/500  305/581  340/644  95/203  120/248  PET  265/509  270/518  290/554  100/212  PMMA  240/464  250/482  35/90  60/140  POM  180/356  225/437  235/455  105/221  PP  20/68  PS  PVC  160/320  190/374  220/428  40/104  SAN 

Temperature-time curve at various locations in the mold

Screw positions at various stages

Cycle time and its components

Required mold opening

Determination of the gate/part freezing time

Pressure decreases along the delivery system and the cavity

Factors influencing injection pressure requirements (I)   Variable  Higher injection pressure required  Lower injection pressure required  PART DESIGN Part thickness  Part surface area

Factors influencing injection pressure requirements (II)   Variable  Higher injection pressure required  Lower injection pressure required  GATE DESIGN  Gate size    Flow length 

Factors influencing injection pressure requirements (III)   Variable  Higher injection pressure required  Lower injection pressure required  PROCESSING CONDITIONS  Melt temperature  Part surface area Ram speed 

Factors influencing injection pressure requirements (IV)   Variable  Higher injection pressure required  Lower injection pressure required  MATERIAL SELECTION Melt flow index 

Injection pressure as a function

Melt front advancements

Melt-front velocity and melt-front area

Fiber orientations

Variation of MFA

Basic runner system layouts

Commonly used runner cross sections

Equivalent hydraulic diameters

Runner diameter chart

Effect of runner length

Hot runner system types

Filling patterns resulting from various injection rates

Cold slug

A family-mold part with artificially balanced runners

Gate size terminology                                                FIGURE 1. Gate size terminology

Gate types （I） Direct (sprue) gate Tab gate Edge (standard) gate Overlap gate Fan gate Disk (diaphragm) gate

Gate types （II） Ring gate Spoke (spider) gate Film (flash) gate

Mold cooling accounts for more than two-thirds of the total cycle time

Proper and efficient cooling improves part quality and productivity

A typical cooling system for an injection molding machine