灭火器喷嘴.docx
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灭火器喷嘴.docx
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灭火器喷嘴
灭火器喷嘴
大连理工大学课程设计专用纸 目录 1.前言·····················································································································································-2-2.塑件分析··············································································································································-3- 塑件材料选择·····························································································································-4-塑件形状····································································································································-4-制品质量····································································································································-4-尺寸精度····································································································································-4-表面粗糙度·································································································································-5- 制品表面粗糙度的选择···································································································-5- 3.注塑成型工艺条件·······························································································································-5- 注塑成型工艺简介·····················································································································-5-注塑成型工艺条件·····················································································································-6-4.拟定模具结构形式·······························································································································-6- 分型面位置的确定·····················································································································-7-型腔数量的确定·························································································································-7-模架的选择·································································································································-8-5.注塑机的选择及校核···························································································································-8- 选择注塑机·································································································································-8- 公称注射量选定注射机·······························································································-8-锁模力选定注射机·······································································································-8-注塑机的校核·····························································································································-9- 最大注塑量的校核···········································································································-9-锁模力的校核··················································································································-9-塑化能力的校核············································································································-10- 6.浇注系统的设计································································································································-10- 主流道······································································································································-11-浇口···········································································································································-11-7.成型零件的工作尺寸计算·················································································································-12- 成型零件工作尺寸的计算·········································································································-12- -1- 大连理工大学课程设计专用纸 凹模的工作尺寸计算·····································································································-13-型芯的工作尺寸计算·····································································································-14-型腔壁厚、支撑板厚度的确定·································································································-15-8.脱模推出机构的设计·························································································································-17- 在设计脱模推出机构是应遵循下列原则。
·············································································-17-脱模力的计算···························································································································-17-设计塑件的推出机构···············································································································-17-9.侧向分型与抽芯机构设计·················································································································-18- 抽拔距·······································································································································-18-斜导柱倾角:
···························································································································-19-斜导柱的工作长度····················································································································-19-斜导柱抽芯机构的设计············································································································-19-10.排气系统设计··································································································································-20-11.温度调节系统设计···························································································································-21- 对温度调节系统的要求···········································································································-21-冷却系统设计:
······················································································································-21- 设计原则······················································································································-21-冷却时间的确定···········································································································-21-塑料熔体释放的热量···································································································-22-高温喷嘴向模具的接触传热························································································-22-注射模通过自然冷却传导走的热量············································································-23-冷却系统的计算···········································································································-24- 12.导向与定位机构·······························································································································-25- 导柱导向定位机构·················································································································-25-13.模具开合模动作过程·······················································································································-26- 开模过程································································································································-26-合模过程································································································································-26-14.总结··················································································································································-27-15.
大连理工大学课程设计专用纸 塑件形状 图1塑件图 该制件形状为旋转体,四面有四个通孔,形状较为简单:
制品质量 根据M=ρV 查表1可得PP1340的密度:
ρ=/cm3 V=π/4D2H-π/4d2h =π/4×74×【π×90×74-4×】/(π×90×74)+ π/4×8+π/4×8+π/4×10 ≈148942mm3≈149cm3 故制品的质量M约为136g 尺寸精度 于改制件未标注公差,查取MT5,B类公差。
-6- 大连理工大学课程设计专用纸 表面粗糙度 制品表面粗糙度的选择 该制品为不透明制品,非配合表面和隐藏的面可取较大的表面粗糙度。
同时可利用这种表面粗糙度的差异使塑件在开模时更加有力的包住型芯,而留在型芯上。
制件各处具体的表面粗糙度在后文将陆续介绍。
热塑性塑料产生的常见性表观质量缺陷及产生原因 表2热塑性塑料常见表观质量缺陷及产生原因 制品表观缺陷 产生的原因 ①注射量不够,加料量及素化能力不足;②料桶、喷嘴及模具温度低;③注射压力太低;④注射速度太慢或太快; 塑件不完整 ⑤流道或浇口太小,浇口数目不够,位置不当;⑥飞边溢料太多; ⑦塑件壁厚太薄,形状复杂且面积大;⑦原料流动性太差,或含水分及挥发物多 ①分型面贴和不严,有间隙,型腔和型芯部分滑动零件间隙过大; ②模具强度和刚性差; 塑件四周飞边过③料桶、喷嘴及模具温度太高; 大④注射压力太大、锁模力不足或锁模机构不良,注射机定、动 模板不平行; ⑤原料流动性太大;⑥加料量过多 塑件有气泡 ①塑料干燥不良,含水分或挥发物; -7- 大连理工大学课程设计专用纸 ②料温高,加热时间长,塑料存在降解、分解;③注射速度太快;④注射压力太小;⑤模温太低,易出真空泡;⑥模具排气不良①加料量不足; ②料温太高,模温也高,冷却时间短;③塑件设计不合理,壁太厚或厚薄不均 塑件凹陷 ④注射及保压时间太短;⑤注射压力不足;⑥注射速度太快; ⑦浇口位置不当,不利于供料;①注射机的电气,液压系统不稳定;②加料量不稳定; ③塑料颗粒不均,收缩率不稳定; 塑件尺寸不稳定④成型条件变化,成型周期不一致; ⑤浇口太小,多型腔时各进料口大小不一致,进料不平衡;⑥模具精度不良,活动零件动作不稳定,定位不准确; ①注射压力太高,注射时间太长或太短;②模具温度太高; ③浇口尺寸太大或位置不当; ④模腔表面粗糙度过大或有划痕; 塑件粘模 ⑤脱模斜度太小,不易脱模;⑥推出位置结构不合理 -8- 大连理工大学课程设计专用纸 ①料温太低,塑料流动性太差②注射压力太小,注射速度太低; ③浇口系统流程长,截面积小,进料口尺寸及形状、 熔接痕 位置不对,料流阻力大;④塑件形状复杂,壁太薄;⑤冷料穴设计不合理 ①料温低,模温、喷嘴温度也低;②注射压力太小,注射速度低; 塑件表面出现波③冷料穴设计不合理; 纹 ④塑料流动性差; ⑤模具冷却系统设计不合理;⑥流道曲折、狭窄,表面粗糙①具温度太高,冷却时间不够; ②塑件形状设计不合理,薄厚不均,相差太大,强度不足;③嵌件分布不合理,预热不足; 塑件翘曲变形 ④塑料分子取向作用太大;⑤模具推出位置不当,受力不均;⑥保压补缩不足,冷却不均,收缩不均;①不同塑料混杂;②同种塑料不同级别相混; 塑件分层脱皮 ③塑化不均匀;④原料污染或混入异物 -9- 大连理工大学课程设计专用纸 3.注塑成型工艺条件 注塑成型工艺简介 注塑成型是塑料先在注塑机的加热料筒中受热熔融,而后柱塞或往复式螺杆将熔体推挤到闭合模具的模腔中成型的一种方法。
它不仅可在高生产率下制得高精度,高质量的制品,而且可加工的塑料品种多和用途广,因此注塑是塑料加工中重要成型方法之一。
一般分为三个阶段的工作。
图2注塑成型压力—时间曲线 物料准备:
为了使注塑能顺利地进行并保证产品得到质量,在成型前有一系列的准备工作。
包括对物料的颗粒情况、外观色泽,杂质含量等进行检验,并测试其流动性,热稳定性和收缩率等指标。
对于吸湿性比较强的塑料,应进行适当的预热干燥,为了保证顺利脱模,部分塑料制品还需要选用脱模剂。
注塑过程:
塑料在料筒内经过塑化达到流动状态后,进入模腔内的流动可分为注射,保压,倒流和冷却四个阶段,注塑过程可以用图2表示。
图中T0代表螺杆或柱塞开始注射熔体的时刻;当模腔充满熔体时,熔体压力迅速上升,达到最大值P0。
从时间T1到T2,塑料仍处于螺杆的压力下,熔体会继续流入模腔内以弥补因冷却收缩而产生的空隙。
于塑料仍在流动,而温度又在不断下降,定向分子容易被凝结,所以这一阶段是大分子定向形成的主要阶段。
这一阶段的时间越长,分子定向的程度越高。
从螺杆开始后退到结束,于模腔内的压力比流道内高,会发生熔体倒流,从而使模腔内的压力迅速下降。
倒流一直进行到浇口处熔体凝结时为止。
制件后处理:
注塑制品经脱模或机械加工后,常需要经过适当的后处理以改善制品的性能和提高尺寸稳定性;制品的后处理主要指退火和调湿处理。
-10-
大连理工大学课程设计专用纸 注塑成型工艺条件 温度;注塑成型过程中需要控制的温度有料筒温度,喷嘴温度和模具温度等。
PP1340料温度的经验数据如下表所示。
表3温度的经验数据 料筒温度/℃
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