Shanghai Daoqin Plastics Co., Ltd.

1 rotational molding molding process and its advantages

    rotational molding is in plastics products molding types process methods, also 称旋转 molding, 旋转模塑 or molding. rotational molding process is will plastics powder add mold in, rear add hot mold make versus 互垂直 两根轴连续旋转, mold inner resin in heavy force and hot amount function lower uniform coating 布, melt 黏附于 mold inner surface upper, from formed need 形状, rear cooling mold, demolding to products.

    rotational molding molding 起源于20世纪40 year UK, 50 year in Europe to very large development, rear USA, Japan and other, polyethylene (PE) powder technology formed 熟, day formed is powder plastics molding process in has competition force molding methods. in recent years, rotational molding industrial 以10～15％ year growth rate development, formed is small amount production in, large type or ultra- large type full and semi 封闭 空心无缝 container most good molding processing methods. currently, full 球旋转模塑 use resin consumption amount already to resin output/production volume 8％～9％.

    rotational molding molding process and in plastics products molding methods (如 injection molding, blow molding, hot molding and other) versus ratio, its most significantly features is resin add hot, molding and cooling process in pressure mold inner 进行. this features make performance series advantages.

    mold simple, cost low 廉, combined molding large type plastics products.

    combined more product types, small amount plastics products production.

    combined molding complex products and composite/compounding products.

    Raw Materials.

    products thick uniform, 无接缝.

    products 无残余 force, easy deformation.

    color easy, need products color 时, 需清洗 molding mold can.

    2 rotational molding molding machine

    2．1 几 types type rotational molding machine

    摇摆式 rotational molding machine: tool has can production large, simple products advantages, factors in system 自动化程 degree high, formed efficiency low lower and as heavy.

    穿梭式 rotational molding machine: has 两 梭 machine, can production large type 储存罐, container and small type products. as simple, 维护费 use low, belongs to grade rotational molding equipment.

    housing/shell rotational molding machine: 初始费 use low, 占 面积 small, 手工劳动 less and products quality good. machine rotational molding process in di 轴旋转由主, 副轴变 speed gears electrical machine provide. can can 曲, can small type or large type mold.

    垂直式 rotational molding machine: 三臂式 and 六臂式, its 转臂操 as in 同一 平面 inner, has separation add hot, cooling or 装／卸工位, most large mold usually 限于 900～1200mm, make products large small to 局限. main/primary used for made as toys 娃娃部 parts, toys, type and automotive parts and other.

    solid 定转臂式 rotational molding machine: equipment can from small type 1000mm摆幅 to large type 3800mm摆幅, has add hot, cooling or 装／卸三 工位, equipment efficiency high, easy 维护, in rotational molding field/area in 占统治 位. usually add hot is cycle key/critical factors, therefore it formed equipment control factors.

    独立转臂式 rotational molding machine: is rotational molding industrial commonly used equipment type type, tool has gas ring add hot and gas ／ water cooling 室, provide 五 工位, 包含一台自动车架 control 每台转臂绕 in 心台转动, 而每台转臂 and between is 独立, provide more 自动化 and more processing 手段, separation 体现 独立转臂 rotational molding machine active property.

    rotational molding machine: machine is add large FSP company exclusive product. machine hot can as cold 箱, structure separation upper lower separation, upper can and 关闭, and methods 如蚌. mold 回转直径 from 1．2～3．6m.

    2．2 国 inner outer 旋转模塑 equipment development 状况

    from rotational molding add hot methods 看, currently relatively commonly used is add hot and hot add hot 式. production large type products generally using/adopting add hot 式, production small type products outer 先进 旋转模塑厂家 relatively more using/adopting hot add hot 三臂四工位 and 四臂五工位 di 轴旋转独立转臂 equipment.

    发达国家 remove for rotational molding equipment type 不断改进 outer, also large force improve/increase equipment 自动化 control water 平. UK development Rotalog旋转模塑 control system 包括测 temperature and control 显示两 large separation. temperature separation 密封安装 in mold upper insulation box/case inner, through electrical hot electrical mold inner temperature degree 实时发送 to add hot outer 监控计算 machine upper, machine mold inner temperature degree ／ time 图. and add hot room temperature degree ／ time comparison, can 直观 显示 rotational molding equipment in mold and its in material material hot, hot 情况. as can utilizing Rotalog control system decrease/reduce and optimization add hot, cooling cycle, and ensure products quality, reduce production cost, also can assessment mold and new material.

    outer rotational molding generally has more different rotational molding equipment. USA spincast company has 7台 rotational molding machine, mold most large 回转直径4m, Dimond company has 9台 rotational molding machine, mold most large 回转直径 is 4．3m, Amerikart company has 10台 rotational molding machine, mold most large 回转直径 is 3．3m.

    rotational molding equipment manufacturing and technology and outer water versus ratio also comparison rear, currently also has property relatively strong/high rotational molding equipment manufacturing 厂. inner rotational molding equipment use 情况, has below/following several features.

    (1) use rotational molding machine 以直火 add hot is 主, also has a small amount of hot add hot 三臂四位独立转臂 rotational molding machine, other machine very less.

    (2) hot add hot 独立转臂 equipment full is outer Imported, main/primary is USA, Italy, Germany and Japan product, 几乎没 Domestic product. Imported add hot machine very less, use add hot machine large more is inner 厂家 仿 products.

    (3)国 inner rotational molding rotational molding equipment amount very less, rotational molding 厂规模 relatively small.

    3 rotational molding molding mold

    3．1 overview

    mold is rotational molding molding in can less important 装备.

    rotational molding mold simple, is pressure molding mold, therefore thin, light 质. rotational molding mold upper lower semi formed, use sheet/plate solid 定. is mold cavity inner formed gas 体, anti products deformation, mold upper 开设排 gas 孔.

    in rotational molding process industrial in, mold made as has types commonly used methods: sheet/plate welding, aluminum alloy and electroplating molding. rotational molding molding for mold strong/high degree requirements high, must tool has good hot property, can frequency add hot and cooling process in force 交替. low carbon 钢, aluminum, 不锈钢 and other is made material. selection mold made as methods usually need below/following 三 方面: complex degree, mold amount and products surface quality requirements. in this requirements in, products and dimensions 占主导 位. can according to different selection different made as methods. meanwhile, in manufacturing mold 时, cost is another important factors. mold made as cost made material, mold thick degree, separation type 面 位置, mold amount and surface treatment and other and other. combined design rotational molding mold structure and positive selection mold material is surface light bubbles, thick uniform force excellent products need ensure.

    mold housing/shell 体 壁 thick design pressure container design specification 进行, from rigid degree 计算出发, combined products thick degree, add hot methods and made methods and other comprehensive 考虑. generally relatively large type mold using/adopting sheet/plate, its thick degree is 2?4mm, mold inner need light. another mold thick degree 取决于旋转 direction and add hot methods, used for hot liquid 体传导 add hot mold, relatively thick, generally is 7．9～12．7mm, ensure hot uniform, 不发生 hot 点; hot ring add hot mold, relatively thin, generally is 5～7mm.

    3．2 铸 aluminum mold

    use 传统 砂 type production parts degree low, made cycle long, parts surface quality more method to rotational molding requirements, rear also 需人工打 abrasion light. therefore, production rotational molding use aluminum 模就必 must using/adopting precision methods, meanwhile fast speed made technology, shrink short mold manufacturing cycle. has this 样, rotational molding molding investment less, fast advantages can separation 显示. precision process methods multiple more 样, for/regarding rotational molding mold this dimensions relatively large 且形状 complex mono parts parts using/adopting type or type is non 常经济. again combined using/adopting hot pressure method, make aluminum alloy flow property large large improve/increase, 进一步 decrease small rotational molding 模体 壁 thick, for add fast rotational molding molding in hot amount 传导, shrink short molding cycle is separation has 利.

    3．3 fast speed made technology

    fast speed made technology use fast speed type technology RPM (Rapid Prototyping Moulding) made type or processing various metal mold methods, is 集CAD／CAM, chemical industry, material and precision machine and other most new formed 就于一身 high new technology. currently development comparison formed fast speed type methods has light type method SLA, thin sheet/plate method LOM, filament method FDM and selection property light method SLS and other. in rotational molding manufacturing in, use surface film LOM原 type 代替木模直接 manufacturing type, type (large parts) or type silicon 橡胶模 渡转换 to type, type (small parts), again use type, type 浇注出 metal mold methods, achieve aluminum precision will is separation has 利.

    4 rotational molding molding products quality control

    4．1 Common quality issues

    simple use is rotational molding molding large advantages, meanwhile to technology belt/tape 一 先天不足 defect. ratio 如, products internal easy generate bubbles, surface easy 出现空洞; products easy bending, shrinkage, color and other. this phenomenon effect/influence products appearance 形象, but also more important is heavy loss products force property can. therefore, research bubbles formed and 消失, bending, shrinkage phenomenon formed and 消失以 and products impact strong/high degree for improve/increase molding products quality tool has separation important 意义.

    4．2 bubbles and 孔眼

    bubbles formed is is powder pellets 熔化并 adhesion in 一起 时候, its belt/tape gas. in industrial production in, using/adopting improve/increase add hot temperature degree methods decrease/reduce or remove products in bubbles. is improve/increase add hot temperature degree, long or remove products in bubbles 时, material material viscosity decrease small, bubbles expand dispersion easy. meanwhile is has more more time make bubbles expand dispersion more 彻底. this type of methods for remove products in bubbles although has 效, is has function. ratio increase melt temperature degree will molding cycle long, reduce production efficiency; high temperature lower material material by oxidation, make products force property can reduce, especially is impact strong/high degree is obvious.

    4．3 impact strong/high degree

    effect/influence products impact strong/high degree factors relatively more, ratio add hot temperature degree, add hot time, cooling speed degree, pellets dimensions, mold material and other, its in add hot temperature degree and add hot time is effect/influence impact strong/high degree main/primary factors. temperature degree low, material melt 不够, products impact strong/high degree reduce; temperature degree high 则会引起 plastics generate degradation, reduce products impact strong/high degree. melt flow rate MFI and its impact strong/high degree has 直接 关联, MFI随 impact strong/high degree decline decline. 因而MFI can as is products impact strong/high degree 指征.

    4．4 shrinkage and deformation

    shrinkage, deformation is plastics rotational molding molding products large defect. shrinkage, deformation generally is cooling formed residual stress 引起, experiment/testing through different cooling methods 交替进行 cooling can decrease/reduce products residual stress, or in cooling toward mold inner pressure shrink gas, through pressure shrink gas make already solid plastics 紧紧贴 in mold inner 壁, retardant it 脱离模壁 or deformation, to plastics full cooling is 止, this 样便起 to cooling type function. and due to method for/regarding already solid plastics inner surface meanwhile cooling, cooling mechanism, from decrease small residual stress, made products shrinkage and deformation. experiment/testing 证明, large separation plastics cooling 时通入0．11MPa pressure shrink gas basic upper remove shrinkage, deformation phenomenon.

    5 rotational molding molding research 进展

    from inner outer 情况看, rotational molding molding technology already very large 进步. research as is rotational molding molding process and improve/increase products quality, in recent years in processing process research and 模拟仿 true, rotational molding molding specialized resin, processing equipment and mold optimization design, process conditions control and other 方面开展 a large amount of research. this research large more is solution rotational molding molding key/critical issues: 1) rotational molding molding for specialized material requirements 苛刻; 2) rotational molding molding processing time long, consumption can high.

    rotational molding molding in, 人们希望 polymer can 象石膏浆 that tool has good coating property can. in add hot methods lower, through mold to hot 不足以 make polymer material to good flow coating 布效果, can powder material in heavy force function lower achieve mold cavity inner uniform coating 布, 并一层层熔 melt molding. due to speed degree slow, this 里离心 force function basic can 忽略(and metal 离心浇铸存 in relatively large 差别). powder material in mold cavity inner 运动受 hot melt coating in mold cavity inner process separation complex and effect/influence to products quality. lower research toward value 关注.

    ①国 outer comparison deep research rotational molding molding in powder flow and its for molding effect/influence. research table/sheet 明, powder material in mold cavity inner can is types type type: ring 流, 雪崩流 and sliding 流. rotational molding molding in most good is ring 流, its is 雪崩流, sliding difficult to combined products. this powder flow factors main/primary is powder material and mold cavity inner friction coefficient and pellets 本身由团 poly force and 几何形状 and other flow property can. therefore, rotational molding molding specialized material remove requirements heat resistant time long outer, also for powder pellets and friction coefficient has requirements.

    ② in rotational molding molding in, essence upper is through external hot mold add hot to plastics melt temperature degree above, rear hot mold again will hot amount to internal powder material. due to plastics thermally conductive property 差, need make full material material separation melt need very long time, but also method use extrusion and injection molding processing in commonly used material. rotational molding molding in polymer melt 凝结, is effect/influence processing time and products quality important factors.

    ③ is process and equipment optimization and improve/increase products quality, also utilizing rotational molding processing process type and machine true and other research, in-depth understanding rotational molding molding main/primary process parameters for molding cycle effect/influence.