CG2-150型火焰仿型切割机设计
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第五章翻译(电火花线切割的介绍) 电火花线切割加工在对一些难切削的材料、特殊及复杂形状的零件的加工上较传统的切削加工方法具有明显的优势,因此被广泛应用于模具、工具、航空航天等制造加工领域。 根据电极丝运动的方式将电火花线切割机床分为快走丝电火花线切割机床和慢走丝电火花线切割机床,二者具有不同的特点和应用场合。快走丝电火花线切割机床因其操作简单、成本低等优点而被普遍采用。在线切割加工过程中,影响加工质量和效率的因素较多,本文结合相关资料,对数控快走丝电火花线切割加工的工艺方法进行研究。 一加工原理 1电极丝与工件之间脉冲式放电加工; 2电极丝沿其轴向作走丝运动; 3工件相对于电极丝在X,Y平面内作数控运动。 二数控电火花线切割加工的特点 1无需制造成形电极,工件材料的预留量少; 2能够方便地加工复杂形状的型孔,微孔,窄缝等; 3直接采用精加工和半精加工规准一次加工成形,一般不需要中途转换规准; 4只对工件材料进行图形轮廓加工,图形内外的余料还可利用; 5自动化程度高,操作方便,加工周期短,成本低。 三数控电火花线切割加工的应用 数控电火花线切割加工为新产品试制,精密零件加工及模具制造开辟了一条新的工艺途径,主要应用于以下几个方面: 1适用于各种形状的冷冲模具。 2可以加工微细异形孔、窄缝和复杂形状的工件。 3加工样板和成型刀具。 4加工粉末冶金模、镶拼型腔模、拉丝模、波纹板成型模。 5加工硬质材料、切割薄片,切割贵重金属材料。 6加工凸轮,特殊的齿轮。 7适合于小批量、多品种零件的加工,减少模具制作费用,缩短生产周期。 四数控电火花线切割的加工工艺 1工件材料的选择 为了加工出尺寸精度高、表面质量好的线切割产品,必须对所用工件材料进行细致考虑: (1) 由于工件材料不同,熔点、气化点、导热系数等都不一样,因而即使按同样方式加工,所获得的工件表面质量也不相同,因此必须根据实际需要的表面质量对工件材料作相应的选择。例如要达到高精度,就必须选择硬质合金类材料,而不应该选不锈钢或未淬火的高碳钢等,否则很难达到所需要求。 (2) 由于工件材料内部残余应力对加工的影响较大,在对热处理后的材料进行加工时,由于大面积去除金属和切断加工会使材料内部残余应力的相对平衡受到破坏,从而可能影响零件的加工精度和表面质量。为了避免这些情况,应选择锻造性好、淬透性好、热处理变形小的材料。 2切割路线的选择(多次切割) 为了获得较高的加工精度,可以考虑在快走丝线切割机床采用多次切割工艺。采用多次切割工艺时,第一次切割主要进行高速稳定切割,因此可选用高峰值电流;第二次切割的主要任务是修光。应选择较小的脉冲电流和脉冲宽度。 3穿丝孔和电极丝切入位置的选择 对于不同的工件,加工穿丝孔的位置不同。在切割中、小孔形凹形类工件时,穿丝孔应位于凹形的中心位置,既便于穿丝孔加工位置准确,又便于控制坐标轨迹的计算;在切割凸形或大孔形凹形类工件时,穿丝孔应设置在加工起点附近,以缩短无用切割行程,同时应便于简化有关轨迹控制的计算。穿孔丝也可选在距离型孔边缘2-5mm处,如图所示。加工凸模时,为减小变形,电极丝切割时的运动轨迹与运动边缘的距离应大于5mm. 4电参数的选择 对加工质量具有明显影响的电参数主要包括脉冲电流、脉冲宽度、脉冲间隔、运丝速度等,通常需要在保证表面质量、尺寸精度的前提下,尽量提高加工效率。 脉冲电源是影响加工表面质量的重要因素。减小单个脉冲能量可以改善表面粗糙度。决定单个脉冲能量的因素主要是脉冲宽度和脉冲电流。因此采用小的脉冲宽度和脉冲电流可获得良好的表面粗糙度。但是单个脉冲能量越小, 切割速度越慢, 如果脉冲电流太小,将不能产生放电火化, 不能正常切割。一般来讲,精加工时,脉冲宽度可在20s内选择;中加工时,可在20s60s内选择。 脉冲间隔对切割速度影响较大,而对表面粗糙度影响较小。脉冲间隔越小,单位时间放电加工的次数越多,因而切割速度也越高。实际上,脉冲间隔不能太小,否则放电产物来不及被冲刷掉,放电间隙不能充分消电离,加工不稳定,容易烧伤工件或断丝。对于厚度较大的工件,应适当加大脉冲间隔,以充分消除放电产物,形成稳定切割。一般脉冲间隔在10s250s范围内基本上能适应各种加工条件,进行稳定加工。 走丝速度对加工速度具有一定影响,随着走丝速度的提高,加工速度将明显增大。但是,高速度会引起电极丝较大的振动而使工件表面的直线度和粗糙度恶化。因此,应在保证加工质量的前提下,选择一个具有适当加工速度的合理走丝速度。 5其它非电参数的选择 (1)电极丝及其走丝速度的选择 一般采用0.06-0.20mm的钼丝。提高走丝速度有利于电极丝把工作液带入较大厚度的工件放电间隙中,有利于电蚀产物排放和放电加工的稳定。 (2)工作液的选择及使用 煤油介电强度高,间隙消耗放电能量多,分配到两极的能量少,排屑困难,故切割速度低。但煤油受冷热变化影响不明显,且润滑性能好,因此不容易断丝。皂化液洗涤性能好,有利于排屑,切割速度较高。 乳化型工作液的节电强度比水高,比煤油低,冷却能力比水弱,比煤油好,洗涤性比水和煤油都好,较非乳化型工作液的切割速度高,是普遍使用的工作液。 纯净的工作液最初使用时并不能获得最好加工效果,而在使用12个工作日后,金属屑进入工作液中形成一定脏度的混合液,这种混合液在切割中具有良好的效果。因此,定期更换工作液时往往不需要将工作液箱清洗非常干净,以获得具有一定脏度的混合液。 五常见问题的处理 1五种放电状态 (1)开路(空载脉冲) 放电间隙没有击穿,间隙上有大于50V的电压,但间隙内没有电流流过,为空载状态(td=ti)。 (2)火花放电(工作脉冲,或称有效脉冲) 间隙内绝缘性能良好,工作液介质击穿后能有效地抛出、蚀除金属。波形特点是:电压上有td,te和Ie波形上有高频振荡的小锯齿波形。 (3)短路(短路脉冲) 放电间隙直接短路相接,这是由于伺服进给系统瞬时进给过多或放电间隙中有电蚀产物搭接所致。间隙短路时电流较大,但间隙两端的电压很小,没有蚀除加工作用。 (4)电弧放电(稳定电弧放电) 由于排屑不良,放电点集中在某一局部而不分散,局部热量积累,温度升高,恶性循环,此时火花放电就成为电弧放电,由于放电点固定在某一点或某局部,因此称为稳定电弧,常使电极表面结炭、烧伤。波形特点是td和高频振荡的小锯齿波基本消失。 (5)过渡电弧放电(不稳定电弧放电,或称不稳定火花放电) 过渡电弧放电是正常火花放电与稳定电弧放电的过渡状态,是稳定电弧放电的前兆。波形特点是击穿延时td很小或接近于零,仅成为一尖刺,电压电流波上的高频分量变低成为稀疏和锯齿形。早期检测出过渡电弧放电,对防止电弧烧伤有很大意义。 2精度、表面质量分析及解决办法 由于高速丝线切割机是采取线电极高速往复供丝的方式,线电极的损耗均匀地分布在近300米电极丝上,虽然电极丝的损耗极小,但电火花线切割机工作时影响其加工工件表面质量的因素很多,更需要对其有关加工工艺参数进行合理选配,才能保证所加工工件表面质量。 对线切割加工质量有直接影响的因素主要涉及人员、设备、材料等方面。为了改善加工工件表面质量,可以从影响最大的人为因素、机床因素和材料因素等三方面来考虑对加工质量的控制方式和改进方法。具体方法如下:(1)合理安排切割路线。 (2) 正确选择切割参数。 (3)采用近距离加工。(4)注意加工工件的固定。 (5)在加工前,必须检查电极丝,电极丝的张力对加工工件的表面质量也有很大的影响,加工表面质量要求高的工件,应在不断丝的前提下尽可能提高电极丝的张力。 (6)高速走丝线切割机一般采用乳化油与水配制而成的工作液。 (7)必须检查导电块的磨损情况。 (8)检查导轮的转动情况,若转动不好则应更换,还必须仔细检查上、下喷嘴的损伤和脏污程度,用清洗液清除脏物,有损伤时需及时更换。还应经常检查贮丝筒内丝的情况,丝损耗过大就会影响加工精度及表面质量。 (9)保持稳定的电源电压。 (10)根据实际需要的表面质量对工件材料作相应的选择。 (11)加工过程中应将各项参数调到最佳状态,以减少断丝现象。 影响电火花线切割加工工件表面质量的因素很多,但只要对其进行系统的分析和科学的分类,就可以对这类复杂而且零乱的因素进行控制与调配,从而改善和提高工件表面质量。 3电极丝损耗分析及措施 数控电火花线切割加工中,电极丝的损耗或断丝严重影响其连续自动操作的进行,尤其是在高速走丝电火花线切割中,因电极丝在加工中的反复使用,随着电极丝损耗的增加,切缝越来越窄,不仅会使加工面的尺寸误差增大;而且一旦在加工中发生断丝,加工必须重新开始,这不仅花费较多工时,而且影响加工的表面质量。造成电极丝损耗或断丝的原因及措施有:(1)电极丝快速(810ms)移动时和导轮、导电块产生磨擦,引起导轮和导电块磨损。长期使用时,导轮V型槽底被电极丝拉出沟槽,导电块长期使用时,接触电极丝的一面也被拉出沟槽。由此造成导丝部位摩擦阻力增大、电极丝由于运动受阻而断裂。 (2)切除材料发生偏移切除材料重量大时,在加工即将结束时容易发生偏转和位移,造成电极丝被卡断。为此,可在工件和切除材料的平面上添加一块经过磨削的平面永久磁钢,以利于切除材料在切割过程中保持固定位置。 (3)工件材料内应力过大线切割时,工件材料内应力的相对平衡状态受到破坏,容易造成切缝变窄而卡断电极丝。 (4)电极丝损耗线切割加工中,在工件材料被蚀除、切割成型的同时,电极丝也会被放电腐蚀,即电极丝发生损耗。电极丝使用的时间较长时,丝径变细且布满显微放电凹坑、抗拉强度下降,最终发生断裂。一般来说,在测量丝径比新丝减少0.03O.05mm时,应及时更换新丝。 (5)电极丝叠绕电极丝应均匀、整齐地绕在储丝筒上。储丝筒内外圆不同轴时会产生不平衡惯量,转动时容易产生叠丝,导致电极丝断裂。因此,储丝筒必须经过动平衡校正。除此之外,运丝丝杠螺母副间隙太大;工件端面切割条件恶劣; 工作液选用不当或者太脏;选择脉冲电流、脉冲宽度过大;进给速度过大等等都会引起电极丝损耗或断丝,因此,为了防止出现断丝故障,需要选择合适的电参数、定期更换工作液、定期更换导轮、稳定装夹工件并选择合理的切割路线等。英文翻译:Part of five translationWEDM in some hard-to-cut materials, special and complex forms processing components than traditional machining method has obvious advantages, it is widely used in moulds, tools, aerospace and other manufacturing processing. According to wire electrode movement in the way that WEDM into WEDM Fast silk and silk WEDM walking, the two have different characteristics and applications. Fast wire WEDM its simple operation, and low cost advantages have been widely adopted. Online cutting process, the impact on the quality and efficiency of processing many factors, the paper with the relevant information on the NC Fast silk WEDM process approach.一. Machining Principle1. Electrode wire and workpiece between pulse discharge machining; 2. Electrode wire along its axial movement for Wire; 3. Parts of the electrode wire in the X, Y plane for NC campaign.二. NC WEDM features1. Without forming electrode manufacturing workpiece material for less; 2. Easy processing of complex shape of holes, microporous, Narrow; 3. Direct use of semi-finishing and finishing processing forming a quasi-regulatory generally do not regulate quasi-way conversion; 4. Only the graphical outline of the workpiece materials processing, graphics and outside the residuals can also use; 5. A high degree of automation, convenient operation, the processing cycle short, low cost.三. NC WEDM Application1. Apply to a variety of shapes Die. 2. Micro-machining can be contoured, narrow shape of the workpiece and complexity. 3. Processing model and molding tool. 4. PM-processing, Xiangpin cavity mode, drawing module, corrugated sheets forming die. 5. Machining of hard materials, cutting thin slices, cutting precious metal materials. 6. Cam processing, special gear. 7. Suitable for small quantities and variety parts processing, and reduce production costs die, shortening the production cycle.四. NC WEDM Processing1. Workpiece material selection In order to produce a high dimensional accuracy and surface quality good Wire products must be used by the workpiece material and meticulous consideration: (1) Since different workpiece materials, melting point, gasification, thermal conductivity, etc. is not the same, so in the same way even if the processing and have received the workpiece surface quality is not the same, it must be based on the actual needs of the surface quality of the workpiece material accordingly choice. For example, to achieve high-precision, we must choose carbide materials, the election should not be hardening stainless steel or high-carbon steel, it will be difficult to meet the required demand. (2) Since the workpiece material processing internal residual stress on the impact of larger, in the heat treatment processing of the material, due to the removal of metals and materials will cut processing internal residual stress the relative balance of damage, which could affect parts machining precision and surface quality. In order to avoid such circumstances, should choose forging good, hardenability, and heat treatment of small deformation of materials. 2. Cutting line choice (multiple Cutting) In order to obtain high precision machining can be considered in the Fast Wire WEDM used repeatedly cutting process. Used repeatedly cutting technology, the first major high-speed stability cutting cutting, it may choose to use the peak current; second cutting is the main task of repair light. Should choose smaller pulse current and pulse width. 3. Wear silk hole and the electrode placed choose Siqi For different parts, processing wear silk hole different positions. In cutting, keyhole-shaped concave Parts, wear silk concave hole should be located in the centre of the hole is easy to wear silk processing location accurate, and easy to control trajectory coordinates calculated in cutting convex or concave-shaped hole - Parts, wear silk hole in the processing should be set up near the starting point, cut to shorten the trip useless, and should be easy to simplify the trajectory control calculations. Also optional perforated silk-hole from the edge of 2-5 mm, as shown. Processing punch, to reduce the deformation of the electrode Siqi cutting trajectory and distance from the edge of movement should be larger than 5 mm. 4. , The choice of parameters Quality of the processing has significant effect on the electrical parameters including pulse current, pulse width, pulse interval, Wan wire speed, usually need to guarantee the quality of the surface, under the premise of dimensional accuracy, as far as possible to improve processing efficiency. Pulse power is affecting the quality of surface machining an important factor. A single pulse energy can be reduced to improve the surface roughness. Decision of a single pulse energy is the main factor pulse width and pulse current. Therefore the use of small current pulse width and pulse will be good surface roughness. However, the smaller the single pulse energy, and cutting speed is slower, if pulse current is too small will not be able to have a discharge cremation, not normal cutting. Generally speaking, finishing, the pulse width can be within 20 s choice of processing, in 20 s 60 s choose. Pulse interval greater impact on the cutting speed, and the surface roughness less affected. Pulse interval smaller unit of time the frequency of EDM more, thus cutting speeds higher. In fact, not too small pulse spacing, or discharge of washouts was too late, discharge gap can not be fully deionization, processing unstable, easily burn the workpiece or broken wires. For larger workpiece thickness, and should be appropriately increased pulse interval in order to fully discharge elimination of product form a stable cutting. General pulse interval in 10 s 250 s can basically meet within the framework of various processing conditions, stable processing. Wire speed of the processing speed of a certain impact on the Wire with the speed of processing speed will be increased significantly. However, the high-speed wire electrodes will cause greater vibration而使workpiece surface roughness of straightness and deterioration. Therefore, we should guarantee the quality of processed under the prerequisite of a proper choice of a reasonable processing speed fiber walking speed. 5. Other non-electrical parameters choice (1) electrode wire and fiber walking speed choice Generally use 0.06-0.20 mm of molybdenum wire. Increase the speed to go wire to wire electrode into the larger work of the thickness of the workpiece in the discharge gap is conducive to corrosion product of emissions and discharge machining stability. (2) of the choice and use of Kerosene high dielectric strength, space discharge energy consumption, the energy distribution to less polarization, Paixie difficult as low cutting speeds. But the cold kerosene not obvious change, and the lubricating properties, and therefore not easily broken wires. Saponification of washing performance and to Paixie, high cutting speed. Working fluid emulsion type of energy-saving water than the high-intensity, low compared with kerosene, the weak than water cooling capacity than kerosene, and water and detergent than kerosene is good, compared with non-working fluid emulsion-cutting, high-speed, is the widespread use of working fluid. The purity of the initial use of the work and not the best processing results, and in the use of 1 to 2 working days, metal shavings into the working fluid in a certain degree of dirt mixed in the cutting of this mixture has a good effect . , And periodic replacement of often do not work cleaning fluid me very clean in order to obtain a certain degree of dirty mixture.五. Common Problems in1. Five discharge status (1) Open (empty Pulse) No breakdown discharge gap, the gap is greater than the voltage of 50 V, but there is no current gap flow for the empty state (td = ti). (2) spark discharge (working pulse, or effective pulse) Gap, good insulation properties, dielectric breakdown after working solution can be effectively thrown out, in addition to metal corrosion. Waveform characteristics are: voltage on the td, and Ie te waveform on the high-frequency oscillation of small sawtooth waveform. (3) short-circuit (short pulse) Short-circuit directly connecting discharge gap, as the servo system for instantaneous feed too much or discharge gap in the product overlap caused by corrosion. Short-circuit current, larger space, but a very small gap ends of the voltage, not the exception processing corrosion role. (4) arc discharge (stable arc discharge) As Paixie undesirable discharge point on a local rather than decentralized, localized heat accumulation, temperature increases, the vicious circle, this time on a spark discharge arc discharge, a discharge point in the fixed point or a partial, as stability arc, making electrode surface coke burn. Td and waveform characteristics of high-frequency oscillation is a small sawtooth disappeared. (5) the transition arc discharge (unstable arc discharge, or instability spark discharge) Transition arc discharge is a normal spark discharge and stability in the transition state arc discharge, arc discharge is stable precursor. Waveform characteristics of the breakdown delay td little or close to zero, only to become a Jianqi, voltage and current wave of high frequency components as sparse and low variable zigzag. Early detection of a transition arc discharge, to prevent arc burns have great significance. 2. Precision, surface quality analysis and solutions Machine is due to high-speed wire line electrode wire for high-speed reciprocating, the loss of electrodes evenly distributed in the last 300 meters electrode wire, although very small electrode wire loss, but WEDM affect its processing work surface quality of many factors, the need for the processing parameters reasonable matching, the process can guarantee the quality of the workpiece surface. Cutting the line have a direct impact on the quality of the main factors involved in personnel, equipment, materials, and so on. In order to improve the quality of workpiece surface processing, the greatest impact from the human factor, machine factors and material factors to consider three aspects of the processing methods and quality control improved method. Specific methods are as follows: (1) reasonable arrangements for cutting line. (2) correct choice for cutting parameters. (3) close processing. (4) attention to the processing of the workpiece fixed. (5) In processing, must be examined electrode wire electrode wire tension on the surface of the workpiece machining quality had a great impact, high-machined surface of workpiece quality requirements, the wire should be as far as possible, under the premise of improving the electrode wire tension. (6) High-Speed Wire Machine generally use of emulsified oil and water from the work of preparation. (7) must be examined conductive block wear. (8) the check-round rotation, if the rotation should not change, must also be carefully examined, the nozzle extent of the damage and dirt, remove the milk with cleaning fluid, damage to the timely replacement. It should also be regular checks receptacle wire tube silk, silk loss will be affected too large machining accuracy and surface quality. (9) maintain a stable power supply voltage. (10) In accordance with the actual needs of the surface quality of the workpiece materials for the corresponding choice. (11) Processing of the parameters should be transferred to the best condition to reduce the phenomenon of broken wires. WEDM impact of the workpiece surface quality of a number of factors, but as long as its systematic analysis and scientific categorization, and can be complex and disorder of such factors control and deployment, which improve and enhance the quality of the workpiece surface. 3. Loss Analysis and wire electrode measures NC WEDM, electrode wire or broken wires in the depletion of its serious impact on the conduct of continuous automatic operation, especially in the high-speed Wire EDM wire cutting as a result of electrode wire in the processing of repeated use, with the electrode The increase in loss silk, kerf increasingly narrow, not only will the size of the processing of error increases in the processing and once in a broken wires, processing must be re-started, this is not only spend more hours of work, but also affect the processing of surface quality. Loss caused electrode wire or broken wires and the reasons for the measures: (1) electrode wire fast (8 10 m / s), and mobile-round, conductive block create friction caused guide pulley block and conductive wear. Long-term use, the V-round lead by the bottom of a trench Wire electrodes, conductive block long-term use, the contact electrode wire has been pulled out of a trench. The resulting guide wire increased friction parts, wire electrode movement delay due to fracture. (2) resection of material removal offset the weight of the material, in the processing at the end of the forthcoming high deflection and displacement caused by the electrode wire card off. To this end, and the removal of the workpiece material and adding a plane after the plane grinding permanent magnet, the material removal in order to facilitate the process of cutting to maintain a fixed position. (3) Stress the workpiece material, line cutting, workpiece material, the relative balance of stress damage, making it easy for narrow kerf, and a power wire card. (4) electrode wire cutting line loss, in addition to the workpiece material is corrosion, cut-At the same time, wire electrode discharge will be corrosion, wear and tear is a wire electrode. Electrode wire used a longer time, the wire diameter and filled with fine microstructure changed discharge pit, the tensile strength decreased, and ultimately fracture. Generally speaking, the new measurement wire diameter wire than 0.03 O.05mm reduction, should be the timely replacement of the new wire. (5) electrode wire electrode wire should be stacked around uniform neatly around in the storage cylinder on the wire. Cylindrical different wire barrel Reserve will have a balanced axis of inertia, rotates easily lead Permian silk, lead wire electrode fracture. Therefore, the certificates must be silk tube balancing correction. In addition, the Advisory Nut shipped fishes and vice gap too workpiece cutting face harsh conditions of work, or the improper selection of Tazang chose pulse current, pulse width too large; feed speeds, and so on will lead to loss or electrode wire broken wires, Therefore, in order to prevent the emergence of broken wires failure, the need to choose the appropriate parameters, and the replacement of regular, periodic replacement guide pulley, stability and the workpiece clamping reasonable choice cutting routes
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