Doc2排气不良---烧焦.doc

成型不良 － 气体烧焦 －Injection Molding Trouble - Gas burn - 何谓气体烧焦？What is Gas burn ? (appearance) 气体烧焦的生成原因Cause of gas burn generation ?注射速度偏快Fast injection speed??排气不畅Inefficient gas vent ??模具温度或树脂温度偏高 High mold temperature and resin temperature 气体烧焦的对策Countermeasure against Gas burn 减慢注射速度To reduce injection speed??改善排气状况 To improve gas venting 何谓气体烧焦？（外观）(1) What is Gas burn ? (appearance) 气体烧焦是指在成型时成型品表面的烧焦现象。Gas burn is burning mark on the surface of test piece. 图1. 手柄试样上出现的气体烧焦（*试样大小约为10cm）Figure.1 Appearance of Gas burn on the surface of test piece( * Test piece size : about 10cm ) 当树脂填充模腔时，原有的空气会从排气口排出。此时，树脂所产生的气体也会从排气口排出。但是，如果模具的排气口被堵塞，或流动末端本来就没有排气口，气体便无法排出，受到压缩后形成高温，从而导致树脂被烧焦。Gas burn occurs when entrapped gas is rapidly compressed and becomes high temperature at a resin filling end. 气体通常这样从排气口排出*CommonlyAir and gas are out from vent. 因排气口堵塞而导致排气不畅时，无处可逃的气体便会受到压缩并形成高温，从而导致树脂被烧焦。Bad conditionAir and gas are not escape. They are compressed and rise temperature. 图2. 气体烧焦的生成原因Figure.2 Gas burn generation 气体烧焦的生成原因(2) Cause of Gas burn generation (2-1) 注射速度偏快(2-1) Fast injection speed 随着树脂的填充，模腔内的空气和树脂中所含的气体会从排气口排出。但是，如果射出速度太快，气体就会来不及从排气口排出，并会因受到隔热压缩而形成高温，进而导致气体烧焦。VP切换偏慢时，也会因同样的原因而容易产生气体烧焦。As resin is filled, air in the cavity and gas caught in resin escape from the vent. If the injection speed is too fast, however, gas discharge from the vent can not follow it, and gas is adiabatically compressed to become high temperature, generating gas burn. When the V-P switching is too late, gas burn is liable to occur by a similar reason 图3. 气体来不及从排气口排出时的情况Figure.3 If the injection speed is too fast.. (2-2) 排气不畅2-2) Inefficient gas vent 与上述情况类似，当排气口的排气能力偏低时，也会发生气体烧焦。原因有两种：一种是排气口的厚度本来就偏薄，另一种是在使用期间排气口被模垢堵塞。同样的道理，当树脂中蕴含的气体量偏多时，气体烧焦也会加重。Similarly to above, if the venting capacity of gas vent is too low, gas burn may also be generated. This occurs in two cases, one being too thin vent from the beginning, and the other being vent plugging with MD or the like during the use. Whe