科學(xué)化射出成型_-閱讀頁(yè)
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【正文】 :1 到 8:1 High ratios tend to work the plastic more。更高的溫度 26 5. Plastic Temperature Temperature profile溫度特征 ? Target mid range of mfg. remendations目標(biāo)為使用原料商推薦范圍之中間值 ? Use 800 – 1200 psi to turn screw用 800– 1200 psi轉(zhuǎn)動(dòng)螺桿 ? Most energy to melt plastic es from screw rotation (shearing effect)多數(shù)熔化塑料的能量來(lái)自螺桿的轉(zhuǎn)動(dòng) (剪切熱作用 ) ? Front zone should not attempt to change melt temperature前面區(qū)域不應(yīng)該試圖用來(lái)改變?nèi)廴跍囟? Watch Temperature controller during molding:成型時(shí)要時(shí)常觀察溫度控制器 ? If zone overrides set points如果區(qū)域超過(guò)設(shè)定點(diǎn) ? raise rear or center zone–提高后方或中心區(qū)域 slow screw rpm–減慢螺桿 rpm lower back pressure–減低背壓 remove barrel blanket 移除料桶的毯子 ? 27 6. Characteristics to Monitor Factors to Monitor:主要監(jiān)控因素 : ? Pressure at transfer (VP)切換時(shí)的壓力 ? Cushion緩沖 ? Fill Time充填時(shí)間 ? Recovery time恢復(fù)時(shí)間 28 7. Molding Window Optimization Process Window Study加工窗口研究 ?Traditionally Hold Pressure and Melt Temperature (and Mold Temp for SC Materials)傳統(tǒng)上保壓和熔融溫度 (和 sc物料的模具溫度 ) ? As discussed Melt temp has very little effect on processability (shear rate is the main controller)如討論所說(shuō) ,熔融溫度對(duì)加工能力很少有影響 ,剪切率是主要控制因素 ? Drop melt temp from study?放棄熔融溫度的研究 ? ? Add high and low fill rate?增加高和低的填充率 ? 29 8. Appendix Appendix附錄 30 Shear Rate Formula For a circular orifice:對(duì)於圓形的管口 Where Q is the volumetric flow rate And r is the radius of the orifice Q是容量流速 , r 是管口的半徑 So, during the first stage, shear rate is affected by the geometry of the tool and the volume of melt entering the cavity during the injection , 在第一階段 , 剪切率是受在射出期間 ,模具的幾何形狀和熔融進(jìn)入模穴的容量所影響的 4Q pr3 剪切率 Shear Rate = 31 Shear Rate for Machine For simplicity, imagine measuring the shear rate at the nozzle of an old fashioned plunger type molding machine: 衝程 Stroke = L 灌咀半徑 Nozzle Radius = r 射出時(shí)間 Injection Time = t 料管半徑 Barrel Radius = R 簡(jiǎn)單來(lái)說(shuō) , 想像在一種老的柱塞類(lèi)型的成型機(jī)器的噴管上測(cè)量剪率 32 Shear Rate for Machine (cont.) Then the volumetric flow rate is: 容量流速是 : Q = (面積 X長(zhǎng)度 )/時(shí)間 Substituting into the shear rate formula, we get: 代入剪切率公式 , 我們得到 : t pR2 L Q = 4Q pr3 Shear Rate = 4(pR2L/t) pr3 = 4R2L r3t = Area x Length Time ( ) 33 Effect of Stroke on Shear Rate So, if the tool and machine aren’t varied : 所以 , 如果工具和機(jī)器不變化 : Where k is a constant equal to 4R2/r3 k 是恆定的等於 4R2/r3 In other words: Shear Rate is directly proportional to the stroke and inversely proportional to the injection time。 單獨(dú)改變?nèi)魏我环蕉紩?huì)帶來(lái)剪切率變動(dòng) L t 剪切率 Shear Rate = k.
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