1、e Gas Assist Injection Molding Gas A.I.M Seminar 气 体 辅 助 成 型 技 术 2005-02-24 GE Advanced Material Confidential 1 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding Key Features 主 要 特 征 l An Extension of Traditional Injection Molding 传 统 注 塑 技 术 的 拓 展 l Produces
2、Molded Parts with Hollow Sections 制 品 中 空 l A Low Cavity Pressure Process 低 型 腔 压 力 l A “ Short Shot“ Process 缺 料 注 塑 2005-02-24 GE Advanced Material Confidential 2 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding Molding Overview 成 型 概 述 l High Pressure Gas
3、(Nitrogen) is Injected into the Uncured Resin高 压 气 体 (N 2)充 入 未 凝 树 脂 l The Gas “ Bubble“ Follows the Path of Least Resistance (High T & Low P)气 体 流 向 阻 力 最 小 处 l Hollow Sections Result from Displaced Resin and Shrinkage in Thick Sections制 品 内 部 壁 厚 处 中 空 2005-02-24 GE Advanced Material Confidential
4、 3 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding Stages of Gas Assist Molding 气 辅 成 型 的 各 阶 段 部 分 充 模 首 次 充 气 二 次 充 气 2005-02-24 GE Advanced Material Confidential 4 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding P
5、rocess Benefits 加 工 优 势 It is important to note that some (not all) of these benefits may be realized for any given part. l Reduced Sink Marks or Read Through under Channels or Ribs减 轻 缩 痕 l Smooth Surface Finish when Compared to Structural Foam制 品 表 面 光 滑 l Reduced Cycle Time when Compared with Str
6、uctural Foam or Thick Parts降 低 循 环 时 间 l Lower Part Weight in Some Parts减 小 制 品 质 量 2005-02-24 GE Advanced Material Confidential 5 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding Process Benefits (continued) l Enhanced Flow Capability增 加 流 动 性 Reduced clamp
7、tonnage requirements降 低 锁 模 吨 位 Reduced pressure requirements降 低 注 射 压 力 Replaces external hot or cold runners with built-in (gas) channels (lower tooling cost).降 低 模 具 成 本 l Reduced Molded-in Stress and Stress Gradient throughout the part 降 低 模 内 应 力 Uniform packing/shrinkage均 匀 收 缩 Reduced part wa
8、rpage减 轻 制 品 挠 曲 l Greater Design Freedom更 大 的 设 计 自 由 度 Adds structure with little penalty结 构 多 样 化 Allows the molding of thick parts可 成 型 较 厚 制 品 2005-02-24 GE Advanced Material Confidential 6 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding Enhanced Flow w
9、ith Gas Assist 气 辅 增 强 流 动 Gas core Channels act as flow leaders气 道 引 流 2005-02-24 GE Advanced Material Confidential 7 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding 13“ x 20“ Plaque Sink clearly visible Sink reduced significantly 2005-02-24 GE Advanced Mat
10、erial Confidential 8 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding Weight Reduction 减 轻 重 量 2005-02-24 GE Advanced Material Confidential 9 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding Warpage in a 4“ x 30“ Plaqu
11、e with Rib 改 善 翘 曲 变 形 Without Gas With Gas 2005-02-24 GE Advanced Material Confidential 10 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding Process Sequence 加 工 顺 序 l Clamp Mold锁 模 l Inject Resin to a Short Shot or Partial Pack注 射 原 料 ( 未 充 满 ) l Inject High
12、 Pressure Gas (Nitrogen)注 高 压 气 体 l Hold Gas Pressure while Cooling冷 却 时 保 持 气 压 l Vent Gas排 除 气 体 l Open Mold / Eject Part开 模 /取 件 2005-02-24 GE Advanced Material Confidential 11 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding Process Variables 加 工 变 量 Inje
13、ction Molding 注 射 系 统 l Mold Temperature模 温 l Melt Temperature熔 体 温 度 l Injection speed注 射 速 度 2005-02-24 + Gas Assist Molding 气 体 辅 助 系 统 l Gas Pressure Profile气 压 剖 面 图 l Gas Timing定 时 进 气 l Material Characteristics材 料 特 性 GE Advanced Material Confidential 12 PDF created with FinePrint pdfFactory
14、trial version http:/ e Gas Assist Injection Molding Setting of molding conditions in the GAI molding *Delay time for gas injection气 体 注 射 的 延迟 时 间 *Gas pressure气 体 压 力 *Gas retention time 气 体 保 留 时 间 *Gas release time.气 体 释 放 时 间 2005-02-24 GE Advanced Material Confidential 13 PDF created with FineP
15、rint pdfFactory trial version http:/ e Gas Assist Injection Molding 气 体 注 入 压 力 P.P.C落 十 段 气 体 压 力 控 制 图 表 高 压 保 压 闭 环 控 制 升 压 力 压 力 下 降 低 压 下 降 第 三 段 第段 时 间 第 一 段 第 二 段 线 性 位 移 延 迟 第 五 段 第 六 段 第 七 段 模 具 顶 出 第 八 段 第 九 段 第 十 段 2005-02-24 GE Advanced Material Confidential 14 PDF created with FinePrint
16、 pdfFactory trial version http:/ e Gas Assist Injection Molding Delay time for gas injection延 迟 时 间 Delay time for gas injection means the time from the completion of resin injection to the start of gas injection. If it is too short, the thickness of the skin layer can be too thin or even the skin l
17、ayer can be broken to form holes in some cases. On the other hand, if it is too long, the appearance can be poor or the gas can not be injected because the resin is already solidified. 延 迟 时 间 是 树 脂 注 射 完 成 至 气 体 开 始 注 射 的 一 段 时 间 。 太 短 ， 制 品 表 层 太 薄 甚 至 会 引 起 表 面 气 孔 。 太 长 的 话 ， 树 脂 已 固 化 会 导 致 不 能
18、 注 射 气 体 或 表 面 光 泽 差 。 2005-02-24 GE Advanced Material Confidential 15 PDF created with FinePrint pdfFactory trial version http:/ e Gas pressure 气 压 Gas Assist Injection Molding The gas pressure is usually less than 30MPa and it is not necessary to apply the pressure as high as 100MPa like in the ca
19、se of usual injection molding. 不 低 于 30MPa但 不 应 高 于 100MPa。 Gas retention time 保 留 时 间 The process of gas retention fills the roles of both dwell and cooling in usual injection molding. The longer the gas retention time is, the better the dimensional accuracy becomes.保 留 时 间 越 长 ， 尺 寸 精 度 越 高 。 2005
20、-02-24 GE Advanced Material Confidential 16 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding Gas release time 释 放 时 间 Gas release time is set in order to release the high pressure gas inside before opening the mold. If the mold is opened before the release of
21、 internal pressure, the molded products are sometimes broken by the internal pressure. 设 定 释 放 时 间 是 为 了 释 放 开 模 前 的 高 压 气 体 ， 否 则 有 可 能 会 使 产 品 破 裂 。 2005-02-24 GE Advanced Material Confidential 17 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding Types of Ga
22、s Systems l Gas Injection through the Machine Nozzle 设 备 喷 嘴 进 气 l Gas Injection into the Polymer Stream (Runner, Manifold) 熔 流 中 进 气 l Gas Injection Directly into the Cavity (in article) using Mold Pins/Nozzles 使 用 气 针 ,型 腔 进 气 2005-02-24 GE Advanced Material Confidential 18 PDF created with FinePr
23、int pdfFactory trial version http:/ e Gas Assist Injection Molding Gas Injection Through the Machine Nozzle 设 备 喷 嘴 进 气 N 2 in N 2 out via recovery N 2 out at sprue break 2005-02-24 GE Advanced Material Confidential 19 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection
24、 Molding Gas Injection into the Polymer Stream 熔 流 进 气 N 2 out at ejection or retraction 2005-02-24 Hydraulics optional GE Advanced Material Confidential N 2 in/out 20 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding Gas Injection Directly into the Cavity 型 腔
25、 进 气 Hydraulics optional N 2 in/out N 2 out at ejection or retraction 2005-02-24 Hydraulics GE Advanced Material Confidential optional N 2 in/out 21 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding Gas Supply l Nitrogen Bottles l Liquid Nitrogen Tank l Membra
26、ne Filter 2005-02-24 GE Advanced Material Confidential 22 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding GAS Assisted Injection Molding Part and Mold Design lRod-like part: Use a cross-section approaching round shape. If a non-circular sharp cross-section i
27、s used, use a generous radius at any turn on periphery lLarge structural part: Use a small nominal thickness and connect thick sections to be gas channels lUniform melt is very important lAccurate shot size is very important lAccurate cavity dimension is very important lEven cooling is very importan
28、t lGas channels should be evenly laid-out on the whole part 2005-02-24 GE Advanced Material Confidential 23 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding GAS Assisted Injection Molding Part and Mold Design lGas channel layout should follow the major polyme
29、r flow direction lExtend gas channel to the last filled area where should be non-appearance place lGas channel should not be close-looped lWhen a gas channel has two or more branches, a step-down channel at end of each branch can avoid gas acceleration lGas should be limited within the gas channel l
30、Small gas channel would induce permeation 2005-02-24 GE Advanced Material Confidential 24 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding GAS Assisted Injection Molding Part and Mold Design lGas should penetrate to the end of the gas channel lUse a generous
31、radius at each turn of gas channel lWhen short shot method is used, the volume of unfilled areas prior to gas injection should not exceed 50% of the total volume of the gas channels. lGas channel layout should follow the major polymer flow direction 分 流 道 扼 流 段 型 腔 气 针 2005-02-24 GE Advanced Materia
32、l Confidential 25 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding GAS Assisted Injection Molding Part and Mold Design lPolymer entrance can be located at thin wall area and apart from gas entrance by more than 30mm, to avoid permeation and back-flow. lWhen p
33、olymer and gas enter the cavity at the same location, a balanced polymer flow promotes even gas penetration. lLocated overflow well at the last filled area. lOverflow well can promote gas penetration, increase gas volume percentage in the gas channel, remove hesitation and stability part quality 200
34、5-02-24 GE Advanced Material Confidential 26 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding GAS Assisted Injection Molding Part and Mold Design lLocate gas nozzle at furthest point last filled area. lOrientate the outlet of gas nozzle along the same directi
35、on as polymer flow lMulticavity mold: Gas to each cavity is supplied by independent gas nozzle. lKeep the melt from velocity constant. 注 气 孔 注 气 孔 2005-02-24 流 道 GE Advanced Material Confidential 27 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding Typical Pro
36、cess and Design Problems 2005-02-24 GE Advanced Material Confidential 28 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding Converging Flow Hollow Core Solid Slug 2005-02-24 Gas Gate GE Advanced Material Confidential 29 PDF created with FinePrint pdfFactory trial version http:/ e Gas Assist Injection Molding Effect of Gravity Resin/Gas Flow Solid on Bottom 2005-02-24 GE Advanced Material Confidential 30 PDF created with FinePrint pdfFactory trial version http:/
