单螺杆挤出机构设计
单螺杆挤出机构设计,螺杆,挤出,机构,设计
Extruder1.General descriptionBy role type extruder can be divided into continuous and non-continuous extrusion extrusion. Plastic extruding machine plastic machine. Plastic extrusion machines in accordance with material flow direction of machine head and screw the angle between the line from the Center, will head into the bevel head (angle of 120) and right angle head. On a housing is bolted to the fuselage nose, head of mold core and nuts in the nose into the line port, core with core in front of, core and core the centre hole used by the core wire.2.machine introduction Extruder extruder is the host, it consists of extrusion systems, drive systems, and heating and cooling systems. 1. extrusion system for extrusion system consists of screw and barrel, Hopper, die, and die, plastic extrusion system for plasticizing to melt evenly, and, in the process of establishing, under pressure from continuous extrusion screw. (1) screw: is the main parts of the extruder, it directly concerns the scope of application of extruder and productivity, made from high-strength corrosion-resistant alloy steel. (2) barrel: is a metal cylinder, generally with higher heat resistance, compressive strength, rugged durability and corrosion resistance of alloy steel or lined steel composite pipe made. Barrel and screw fit, achieve a crushing, softening, melting of the plastic, plastic, exhaust and compacted, and continuous uniform conveying rubber molding system. Barrel length is 1530 times its diameter, so that the plastic is fully heated and fully plastic into principles. (3) the hopper: hopper bottom cut off device to adjust and cut the material flow, side of the hopper is equipped with vent and calibration of metering devices. (4) head and die: die formed by a coat of alloy steel and carbon steel, head mold. Head is the role of the rotary motion of the plastic melt into a parallel linear movement, in a uniform steady import mode, and endows plastics with the necessary pressure. Plastic plastic compaction in the barrel, via porous filter plate along a certain stream of road through the head neck into the head mold, mold mandrel set where appropriate, formation cross sections and constantly reducing the annular space, plastic melt around the wires form a continuous dense coating of tubes. To ensure reasonable channel head plastic, eliminating the accumulation of plastic corners, always placed a shunt socket, for elimination of plastic extrusion pressure fluctuations, there is set of grading rings. Head is also equipped with mould correction and adjustment device, easy to adjust and correct concentricity of the core and die sets. Plastic extrusion machines in accordance with material flow direction of machine head and screw the angle between the line from the Center, will head into the bevel head (included angle of 120 degrees) and right angle head. Head of shell is with bolt fixed in fuselage Shang, head within of mold has die core sat, and nut fixed in head into line port, die core block of front with die core, die core and the die core block of Center has hole, for through core line; in head Qian Department with are pressure ring, for balanced pressure; squeeze package forming part by die sets block and die sets composed, die sets of location can by bolt through support to regulation, to adjustment die sets on die core of relative location, easy regulation squeeze package layer thickness of uniform sexual. Head external heater and temperature measuring devices. 2. drive screw is the transmission drive system for supply screw Torque required and speed during the extrusion process, usually by the motor, gearbox and bearings and other components. 3. heating and cooling heating and cooling devices are necessary for plastic extrusion process can be carried out. (1) extrusion presses usually use an electric heating, divided into induction heating and resistive heating, heater installed in each part of the body, neck, and head. Heating device by an external heating cylinder of plastic, making it heated up to processing needed temperature is reached. (2) the cooling unit is to ensure that the plastic that is set up in the temperature range of technical requirements. Specifically to eliminate rotation of the screw cut the excess heat of friction, in order to avoid high temperature plastic decomposition, scorch or stereotyped difficulties. Machine tube cooling is divided into water-cooled and wind cold two species, General medium squeeze plastic machine used wind cold comparison suitable, large is more used water-cooled or two species Forms combines cooling; screw Rod cooling main used Center water-cooled, purpose is increased material solid conveying rate, stable out rubber volume, while improve products quality; but in hopper Department of cooling, a is to strengthened on solid material of conveying role, prevent due to warming makes plastic grain made stick jam material mouth, II is guarantee drive part normal work.3.classification Number usually screw extruder is divided into single-screw extruders, twin screw extruder and multi screw extruders. Screw-type extruder-plastic systems, heating and cooling systems, transmission systems and electrical control system composed of four parts. Plasticizing screw is the main part of the system, depending on the varieties selection of plastic and its products structure of screw. Extruder screw diameter for 30250mm at a speed of 30300R/min. Screw length is usually the diameter of 2025 times, up to 30 times. Extruding machine cylinder electric heaters heat water or air cooling. Screw conveyor used in extruder machines, commutator motors or DC motors.4.basic mechanism Turning in the screw in the cylinder and push the plastic. Screw is actually a ramp or slope, the Twining layer in the Center. Its purpose was to increase the pressure in order to overcome the resistance of larger. An extrusion machine, there are 3 kinds of obstacles need to be overcome: the solid particle (feed) on the screw and cylinder wall friction when turning the first few laps (feed) mutual friction between them; melt adhesion on the wall; the internals of the melt forward logistics and resistance.5.mechanical principles In the raw material powder add water or a suitable liquid, stirring constantly. The mixed material using high pressure from the porous head or metal extrusion. Usually, after the material into a cylindrical container, screw extrusion materials. Using frequency conversion technology, the pressure can be controlled, so that you can select the most appropriate linear speed. Principles of single-screw extruder Single screw on the effective length is divided into three sections, deep pitch screw by screw diameter size determine the effective length of the third, usually broken down by each one-third. Last thread began to call transportation section: material requirements are not plastic, but you want to warm up, squeeze the real, old extrusion theory is that here the items are loosely, and later by showing that the material here is actually solid, which means that after the material is squeezed is a solid plug-like, so as long as the complete conveying tasks is its function. Compression in the second paragraph, spiral groove volume becomes smaller, and the temperature to achieve the degree of plastic materials, compressed by the conveying section three, here condensed into one, this is called a compression ratio of screw-3:1, some machines also have changed, complete plasticized material will go to the third paragraph. Paragraph metering section here will keep the plasticization temperature, just accurate, quantitative transmission adopted like metering pumps molten material to supply the head, in which case temperature does not fall below the plasticizing temperature, usually slightly higher.6.practice Various types of products in plastic extrusion lines, will have its operating features, a detailed understanding of its operating features before they can fully develop the efficiency of the machine. Is one type of extruder and its a good grasp of extruder operation and correct use of the extruder. Screw extruder including machine installation, adjustment, start-up, operation, maintenance and repair, a series of links, it uses General machines have in common, mainly in terms of drive motor and speed reducer transmission device. Screw extruder system out of the system, but with unique characteristics, use screw extrusion unit should pay special attention to its features. Machine installation, adjustment and testing of extruder instruction manuals are clear that operation of the extruder, maintenance and service are summarized below: Operator must be familiar with the structural characteristics of their own of extruder operation, in particular, to correct structural characteristics of screw, heating and cooling the control instrument, die characteristics and Assembly, in order to properly grasp of extrusion conditions, correctly operate the machine7.control system Plastic extruder control system including heating systems, cooling systems and process parameter measurement system, primarily by electrical equipment, instrument and executing agencies (namely, operation and control panel). Its main role is to: drag the motor control and the flow adjustment of main engine and auxiliary machine, meet the technological requirements of speed and power output, and enables the coordination of main engine and auxiliary machine; testing and regulation of plastic extrusion machine temperature, pressure, flow, control or automatic control of the whole unit. Extruder for transmission control and temperature control electric control system is broadly divided into two major parts, the extrusion process, including temperature, pressure, screw speed, screw, barrel cooling, cooling products cooling control of inside and outside diameters, and film speed, straight lines and guarantee take-up from empty to full disk on a disk of constant tension winding control. 1. temperature control of plastic extrusion machine Wire and cable insulation and sheathing extruder based on deformation properties of thermoplastics, over the edge of the sticky fluid. In addition to requiring external heating screw and barrel, to plastic to make it melt extrusion, also the screw extrusion of plastic itself when heated, therefore requires that the host, the temperature should be considered overall, taking heat heater on and off, but also consider spillover factor screw extrusion heat cooling, there must be effective cooling facilities. And requires proper rational method to determine the location and installation of measuring component thermocouple, temperature control instrument readings accurately reflects the actual temperature of the host segments. Good and requires the precision of temperature control instruments and systems to enable host fluctuations in temperature control system of stability as a whole meets the requirements of all kinds of plastic extrusion temperature. 2. the pressure control of the extruder In order to reflect the extrusion head, need to detect when the extrusion head pressure, due to the domestic plastic extrusion machine without pressure sensor head, generally for thrust measurement as an alternative after the screw head pressure measurement, load table screw (ammeter or voltmeter) accurately reflects the size of extrusion pressure. Extrusion pressure fluctuations, causing extrusion quality is one of the important factors of instability, extrusion pressure fluctuation and the extrusion temperature, cooling, closely related to factors such as length of continuous operation. When an exception happens when would preclude removing them immediately, must reorganize production should be decisively shut down, can prevent the increase in waste, can prevent the occurrence of accidents. By detecting the pressure gauge reading, you can know the stress of plastic extrusion, generally takes thrust after the limit value alarm control. 3. screw speed control Screw speed regulation and stability are important technological requirements of the host drive. Screw RPM directly determine the amount of glue and extrusion speed, normal production wants to achieve the highest possible speed and achieve high yield, requirements for extruder screw speed from start to the desired speed, speed range available for use. Stability of rotating speed and high speed fluctuations will result in output volatility, affecting the quality of extrusion, so the traction line under speed does not change, it will cause the cable outer diameter changes. Same as traction device for wire-speed movement also results in changing the cable diameter, screw speed and traction line may be reflected by sitting the appropriate instrument, squeeze should closely observe to ensure high quality and high yield. 4. the outer diameter of the cable outer diameter size of control as described above in order to ensure that products, in addition to control core (core) outside the tolerance, in the extrusion temperature, screw speed, line speed should be controlled to ensure traction device, measurement of outer diameter control are integrated reflecting the above level of precision and control. Plastic extrusion units, particularly on high-speed extrusion production line should be equipped with on-line diameter measuring instrument, test the cable outer diameter at any time, and the variance signal feedback to adjust the speed of traction or screw, correct outside diameter variances. 5. the winding requirements of tension control In order to ensure different speed of take-up, from empty to full tension requirement hope line take-up device have the tank thread tension adjustment, or consider constant linear velocity in electrical systems and constant tension control system of rewinding, and so on. 6. complete machine of electric automatic control This is high speed extrusion lines for the process control requirements of, inter alia: power on temperature interlock working pressure protection and interlock material synchronous control, towing two large transmission ratios; take-up and traction control; od-line detection and feedback control; according to different needs of single components and machine track control 挤出机1.概述挤出机按作用类型可分为连续挤出和非连续挤出。塑料挤出机也是塑料机械的一种。挤塑机按照机头料流方向和螺杆中心线的夹角,将机头分成斜角机头(夹角120)和直角机头。机头的外壳是用螺栓固定在机身上,机头内的模具有模芯坐,并用螺帽固定在机头进线端口,模芯座的前面装有模芯,模芯及模芯座的中心有孔,用于通过芯线。2.机器介绍塑料挤出机的主机是挤塑机,它由挤压系统、传动系统和加热冷却系统组成。1.挤压系统挤压系统包括螺杆、机筒、料斗、机头、和模具,塑料通过挤压系统而塑化成均匀的熔体,并在这一过程中所建立压力下,被螺杆连续的挤出机头。(1)螺杆:是挤塑机的最主要部件,它直接关系到挤塑机的应用范围和生产率,由高强度耐腐蚀的合金钢制成。(2) 机筒:是一金属圆筒,一般用耐热、耐压强度较高、坚固耐磨、耐腐蚀的合金钢或内衬合金钢的复合钢管制成。机筒与螺杆配合,实现对塑料的粉碎、软化、熔融、塑化、排气和压实,并向成型系统连续均匀输送胶料。一般机筒的长度为其直径的1530倍,以使塑料得到充分加热和充分塑化为原则。(3) 料斗:料斗底部装有截断装置,以便调整和切断料流,料斗的侧面装有视孔和标定计量装置。(4) 机头和模具:机头由合金钢内套和碳素钢外套构成,机头内装有成型模具。机头的作用是将旋转运动的塑料熔体转变为平行直线运动,均匀平稳的导入模套中,并赋予塑料以必要的成型压力。塑料在机筒内塑化压实,经多孔滤板沿一定的流道通过机头脖颈流入机头成型模具,模芯模套适当配合,形成截面不断减小的环形空隙,使塑料熔体在芯线的周围形成连续密实的管状包覆层。为保证机头内塑料流道合理,消除积存塑料的死角,往往安置有分流套筒,为消除塑料挤出时压力波动,也有设置均压环的。机头上还装有模具校正和调整的装置,便于调整和校正模芯和模套的同心度。挤塑机按照机头料流方向和螺杆中心线的夹角,将机头分成斜角机头(夹角120度)和直角机头。机头的外壳是用螺栓固定在机身上,机头内的模具有模芯坐,并用螺帽固定在机头进线端口,模芯座的前面装有模芯,模芯及模芯座的中心有孔,用于通过芯线;在机头前部装有均压环,用于均衡压力;挤包成型部分由模套座和模套组成,模套的位置可由螺栓通过支撑来调节,以调整模套对模芯的相对位置,便于调节挤包层厚度的均匀性。机头外部装有加热装置和测温装置。2.传动系统 传动系统的作用是驱动螺杆,供给螺杆在挤出过程中所需要的力矩和转速,通常由电动机、减速器和轴承等组成。3.加热冷却装置 加热与冷却是塑料挤出过程能够进行的必要条件。(1) 现在挤塑机通常用的是电加热,分为电阻加热和感应加热,加热片装于机身、机脖、机头各部分。加热装置由外部加热筒内的塑料,使之升温,以达到工艺操作所需要的温度。(2) 冷却装置是为了保证塑料处于工艺要求的温度范围而设置的。具体说是为了排除螺杆旋转的剪切摩擦产生的多余热量,以避免温度过高使塑料分解、焦烧或定型困难。机筒冷却分为水冷与风冷两种,一般中小型挤塑机采用 风冷比较合适,大型则多采用水冷或两种形式结合冷却;螺杆冷却主要采用中心水冷,目的是增加物料固体输送率,稳定出胶量,同时提高产品质量;但在料斗处的冷却,一是为了加强对固体物料的输送作用,防止因升温使塑料粒发粘堵塞料口,二是保证传动部分正常工作。3.分类挤出机通常按螺杆数目分为单螺杆式挤出机、双螺杆式挤出机和多螺杆式挤出机。螺杆式挤出机由塑化系统、加热与冷却系统、传动系统和电气控制系统四部分组成。塑化系统的主要部件是螺杆,根据塑料及其制品的品种选择不同结构的螺杆。常用挤出机的螺杆直径为30250mm,转速为30300r/min。螺杆长度通常为直径的2025倍,最大为30倍。挤出机机筒多用电加热器加热而用水或空气冷却。螺杆式挤出机挤出机所用的传动机多为整流子电动机或直流电动机。4.基本机理一个螺杆在筒体中转动并把塑料向前推动。螺杆实际上是一个斜面或者斜坡,缠绕在中心层上。其目的是增加压力以便克服较大的阻力。就一台挤出机而言,有3种阻力需要克服:固体颗粒(进料)对筒壁的摩擦力和螺杆转动前几圈时(进料区)它们之间的相互摩擦力;熔体在筒壁上的附着力;熔体被向前推动时其内部的物流阻力。5.机械原理在原料粉末里添加水或适当的液体,并进行不断的搅拌。将搅拌好的材料,用高挤出压力从多孔机头或金属网挤出。通常是把材料放入圆筒形容器以后,用螺杆挤出材料。在使用变频技术以后,可对压力进行控制,从而可以选择最合适的线性速度。单螺杆挤出机原理单螺杆一般在有效长度上分为三段,按螺杆直径大小螺距螺深确定三段有效长度,一般按各占三分之一划分。料口最后一道螺纹开始叫输送段:物料在此处要求不能塑化,但要预热、受压挤实,过去老挤出理论认为此处物料是松散体,后来通过证明此处物料实际是固体塞,就是说这里物料受挤压后是一固体象塞子一样,因此只要完成输送任务就是它的功能了。第二段叫压缩段,此时螺槽体积由大逐渐变小,并且温度要达到物料塑化程度,此处产生压缩由输送段三,在这里压缩到一,这叫螺杆的压缩比3:1,有的机器也有变化,完成塑化的物料进入到第三段。第三段是计量段,此处物料保持塑化温度,只是象计量泵那样准确、定量输送熔体物料,以供给机头,此时温度不能低于塑化温度,一般略高点。6.操作规程塑料挤出生产线中各个类型产品,都有其操作特点,对其操作特点有个详细的了解,才可以充分发挥机器的效能。挤出机是其中一种类型及其,把握好挤出机的操作要点,正确合理地使用挤出机。螺杆挤出机的使用包括机器的安装、调整、试车、操作、维护和修理等一系列环节,它的使用具有一般机器的共性,主要表现在驱动电机和减速变速装置方面。但螺杆挤出机的工作系统即挤出系统,却又独具特点,在使用螺杆挤出机时应特别注意其特点。机器的安装、调整、试车一般在挤出机的使用说明书中均有明确规定,这里对挤出机的操作要点,维护与保养简述如下:操作人员必须熟悉自己所操作的挤出机的结构特点,尤其要正确掌握螺杆的结构特性,加热和冷却的控制仪表特性、机头特性及装配情况等,以便正确地掌握挤出工艺条件,正确地操作机器7.控制系统塑料挤出机的控制系统包括加热系统、冷却系统及工艺参数测量系统,主要由电器、仪表和执行机构(即控制屏和操作台)组成。其主要作用是:控制和调节主辅机的拖动电机,输出符合工艺要求的转速和功率,并能使主辅机协调工作;检测和调节挤塑机中塑料的温度、压力、流量;实现对整个机组的控制或自动控制。挤出机组的电气控制大致分为传动控制和温度控制两大部分,实现对挤塑工艺包括温度、压力、螺杆转数、螺杆冷却、机筒冷却、制品冷却和外径的控制,以及牵引速度、整齐排线和保证收线盘上从空盘到满盘的恒张力收线控制。1. 挤塑机主机的温度控制电线电缆绝缘和护套的塑料挤出是根据热塑性塑料变形特性,使之处于粘流态进行的。除了要求螺杆和机筒外部加热,传到塑料使之融化挤出,还要考虑螺杆挤出塑料时其本身的发热,因此要求主机的温度应从整体来考虑,既要考虑加热器加热的开与关,又要考虑螺杆的挤出热量外溢的因素予以冷却,要有有效的冷却设施。并要求正确合理的确定测量元件热电偶的位置和安装方法,能从控温仪表读数准确反映主机各段的实际温度。以及要求温控仪表的精度与系统配合好,使整个主机温度控制系统的波动稳定度达到各种塑料的挤出温度的要求。2. 挤塑机的压力控制为了反映机头的挤出情况,需要检测挤出时的机头压力,由于国产挤塑机没有机头压力传感器,一般是对螺杆挤出后推力的测量替代机头压力的测量,螺杆负荷表(电流表或电压表)能正确反映挤出压力的大小。挤出压力的波动,也是引起挤出质量不稳的重要因素之一,挤出压力的波动与挤出温度、冷却装置的使用,连续运转时间的长短等因素密切相关。当发生异常现象时,能排除的迅速排除,必须重新组织生产的则应果断停机,不但可以避免废品的增多,更能预防事故的发生。通过检测的压力表读数,就可以知道塑料在挤出时的压力状态,一般取后推力极限值报警控制。3. 螺杆转速的控制螺杆转速的调节与稳定是主机传动的重要工艺要求之一。螺杆转速直接决定出胶量和挤出速度,正常生产总希望尽可能实现最高转速及实现高产,对挤塑机要求螺杆转速从起动到所需工作转速时,可供使用的调速范围要大。而且对转速的稳定性要求高,因为转速的波动将导致挤出量的波动,影响挤出质量,所以在牵引线速度没有变化情况下,就会造成线缆外径的变化。同理如牵引装置线速波动大也会造成线缆外径的变化,螺杆和牵引线速度可通过操作台上相应仪表反映出来,挤出时应密切观察,确保优质高产。4. 外径的控制如上所述为了保证制品线缆外径的尺寸,除要求控制线芯(缆芯)的尺寸公差外,在挤出温度、螺杆转速、牵引装置线速度等方面应有所控制保证,而外径的测量控制则综合反映上述控制的精度和水平。在挤塑机组设备中,特别是高速挤塑生产线上,应配用在线外径检测仪,随时对线缆外径进行检测,并且将超差信号反馈以调整牵引或螺杆的转速,纠正外径超差。5. 收卷要求的张力控制为了保证不同线速下的收线,从空盘到满盘工作的恒张力要求,希望收排线装置有贮线张力调整机构,或在电气上考虑恒线速度系统和恒张力系统的收卷等等。6. 整机的电气自动化控制这是实现高速挤出生产线应具备的工艺控制要求,主要是:开机温度联锁;工作压力保护与联锁;挤出、牵引两大部件传动的比例同步控制;收线与牵引的同步控制;外径在线检测与反馈控制;根据各种不同需要组成部件的单机与整机跟踪的控制。9
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