机械外文翻译--- 电主轴技术水平分析

毕业设计（论文）外文参考文献翻译
机械工程系（院）20 08 届
题目（中文）电主轴的机械设计
（英文）the mechanic designs of electric spindles 学生姓名
专业班
完成日期：2008 年3月23 日
目录
1.电主轴技术水平分析 (8)
2.高速电主轴单元 (14)
The electrical technical level of main shaft is analysed
Abstract: Electrical main shaft is the processing machine tool of numerical control " heart parts ", this paper has introduced typical structure and the working principle of electrical main shaft , has elaborated the crucial technology of electrical main shaft , has summarized it to develop tendency.
Keyword: The electrical porcelain ball of main shaft mix the bearing lubrication of oil gas
1, it is general to state the processing quality that can not only raise processing efficiency substantially because of high speed processing and can still raise workpiece apparently, so, its application field is very extensive , is especially in aerospace , the manufacturing industries such as automobile and mould in. It is spoilt recently that so, the machine tool of numerical control that has high speed process capability has become market. Now, the domestic and international each famous manufacturer of machine tool adopts the electrical structure of main shaft extensively in the machine tool of numerical control , is especially being compound to process machine tool and much axle to unite to move , polyhedron processing machine tool and the machine tool of parallel connection in. Electrical main shaft is the processing machine tool of numerical control " heart parts ", its performance index direct decision the level of machine tool, it is that machine tool realizes basic condition and the prerequisite of high speed processing.
2 the working principle electrical main shaft of the working principle, typical structure and 2.1 advantage electrical main shafts of electrical main shaft is the direct motor rotor of be hollow pack in main shaft on, stator knows super-cooling but cover fixes , form a complete unit of main shaft in the casing hole of main shaft, after starting eclectricity rotor directly drive the operation of main shaft.
The typical structural layout way of the typical structural electrical unit of main shaft of 2.2 electrical main shafts is that generator sets up before main shaft , rear axle Cheng between ( as picture show ), its advantage is that the axial size of the unit of main shaft is the big, medium-sized machine tool of numerical control short comparatively, the rigidity of main shaft big, power suits comparatively; It is insufficient to be the naturally scattered hot condition in the generator in the casing of main shaft that encloses to differ from , has higher temperature rise.
The 1 casings of main shaft the 2 cooling sets of 3 4 5 import stator rotors of cooling water the 6 sets of 7 8 9 10 former 11 can export feedback installation bearing rear axles of cooling water of runner shaft of main shaft of main shaft Cheng the advantage electrical province of main shaft of 2.3 electrical main shafts have gone to take ship or positive drive, the 0 transmissions that have realized machine tool have raised transmission efficiency. The rigidity of electrical main shaft good, rotary precision is sex high respond fast good, can realize very high rotational speed and add and slow down degree and decide angle stop fast definitely ( C axle control ), the scope of speed adjustment is wide.
3, the crucial technical concept of " electrical main shaft " of electrical main shaft should not be simple to understand for the merely a sleeve of main shaft , and should be a set of
assembly, include: Stator, rotor, bearing, the high speed installation of frequency conversion and lubrication install and cool installation. Therefore electrical main shaft is the with high speed bearing technical, lubrication technical, cooling technical technical, precise production of dynamic balancing with the technologies such as assembly technology as well as generator high speed drive synthesize to utilize.
The with high speed bearing technology of 3.1 electrical main shafts realizes the electrical high speed of main shaft to melt, is precise and crucial to be the application of high speed precise bearing. Now the bearing that applied in high speed precise electrical main shaft have precise roll bearing and liquid movement press bearing and gas press bearing and magnetic suspension bearing quietly, but it is precise angle contact porcelain ball bearing and precise cylinder roller bearing mainly. It is high that liquid movement press the standardization level of bearing; Gas presses bearing quietly to be improper for in the rate occasion of great merit; Magnetic suspension bearing because of control system complex, price is expensive , its practicality gets restriction.
Angle contact ball bearing can not only at the same time bear radial and axial load, and rigidity high, high speed performance good, structural simple compact, kind specifications numerous repair easily to change, thus in electrical main shaft, get extensive application. Now along with the development of porcelain bearing technology, the electrical bearing of main shaft of the most application is to mix porcelain ball bearing, roll body use Si3N4 porcelain ball, with the structure of " little pearl dense pearl ", bearing ferrule encloses for GCr15 steel. Is this kind of to mix bearing to pass to reduce little centrifugal force and top moment , reduce the friction between little ball and raceway groove , so get lower temperature rise and better high speed performance.
Porcelain ball mix bearing and steel ball bearing compare , advantage is as follows:
( 1 ) the porcelain ball bearing friction performance of porcelain and steel composition very good, can reduce the stress of material and lubricant.
( 2 ) because of porcelain density low , can reduce the centrifugal force in operation.
( 3 ) the heat with lower porcelain coefficient of expansion have reduced bearing efficiently add the change of load in advance.
( 4 ) the flexible mould of porcelain quantity higher, can raise the rigidity of bearing.
Above-mentioned factor have prolonged the life of bearing substantially with have promoted the operation limit speed of bearing.
The lubrication technical with high speed electrical main shaft of 3.2 electrical main shafts the temperature rise that must control bearing with reasonable, controallable bearing lubrication way , in order to guarantee stability and the precision of the machining complex of numerical control of machine tool. Adopt to roll the lubrication way of the electrical main shaft of bearing now have the waies such as fat lubrication, oil fog lubrication and the lubrication of oil gas mainly.
Fat lubrication in the electricity with relatively lower rotational speed main shaft in is more common lubrication way. The lubrication system of fat lubrication type electrical main shaft is simple , uses convenience and free from contamination , has strong versatility.
Oil fog lubrication has lubrication and cooling double role, it is taking compressed air as power , mixes oil liquid atomization into air through oil fog ware to flow , then transports it to need the location of lubrication. The equipment needed by oil fog lubrication is simple ,
maintenance convenience has more cheap price , is a kind of with high speed electrical lubrication way of main shaft that used generally. But it has pollutive environment, oil consume more higher shortcoming. Along with the raising that people ask for environmental protection, oil fog lubrication way must be superseded gradually.
The lubrication technology of oil gas is use compressed air the lubricating oil of be trace difference succession continuously land provide each set of bearing of main shaft accurately, small oil drop in roll with , outside raceway between form the flexible oil membrane of dynamic pressure, and reduce air can take the partial heats produced by bearing operation. Practice shows that the fuel delivery in lubrication is been harmful for too much less , and former two lubrication waies can not control the amount of fuel delivery accurately , disadvantage in the raising of the bearing rotational speed and life of main shaft. And develop the lubrication way of oil gas of geting up recently the lubricating oil that can control the point of every friction accurately quantity, reliability is very high. Practice proof and the lubrication of oil gas are the most ideal method of lubrication of great merit of the rate electrical bearing of main shaft, but the equipment needed by it is complex , cost is high. Because of the lubrication way lubrication effect ideal of oil gas, now have become international the last most popular lubrication way.
Its cooling electrical main shaft and the analysis of thermal source of 3.3 electrical main shafts have two major internal thermal sources: Built-in motor give out heat with the bearing of main shaft give out heat. If not control , from the heat that this arouses warp can the serious processing precision and bearing service life that reduces machine tool , so, the service life that causes electrical main shaft shortens.
Electrical main shaft because of the depository type configuration of main shaft in adopting, locate in the generator in the unit of main shaft can not break up with fan heat, therefore naturally, scattered hot condition is lacked comparatively. Generator is realizing energy transition , is internal to produce power loss , so makes generator give out heat. Study to show , is under generator with high speed operation condition , have near 1/3 generator give out heat quantity from generator rotor produce , and the absolutely most of heats that rotor produces are passed through the air gap between rotor and stator in stator; Others 2/3 the stator that heat produces in generator. So produce the major solution method of giving out heat for generator is the cycle for that generator stator adopts cooling fluid flow to carry out force to cool. Typical cooling system is to cool generator stator with the water type cooling installation of outer circulation , goes to the heat tape of generator.
What angle contact ball bearing give out heat , is roller mainly under high speed and the rolling friction between raceway, the etc. that receive the top sliding friction that moment produces as well as the viscous friction of lubricating oil produce. Reduce little bearing to give out heat the major measure of quantity:
( 1 ) reduce the diameter of little ball properly reduce little ball diameter can reduce little centrifugal force and top moment, so, reduce little friction, quantity decreases to give out heat.
( 2 ) adopt new material for example adopt porcelain material do ball, porcelain ball bearing and steel quality angle contact ball bearing are compared with , when high speed turns around ball and raceway between roll with sliding friction reduce little, give out heat to measure reduction.
( 3 ) the lubrication way oil gas of reasonable adopting and the lubrication waies such as oil fog for bearing not only have lubrication role, still have certain cooling role.
Service life and the performance of 3.4 electrical main shafts that design and assembly electrical main shaft will get must carry out elaborate design and production for the electrical every part of main shaft. The stator of electrical main shaft from have is high Dao the high quality flat of silicon steel of magnetic rate press repeatedly, in stator cavity have to rush system inlay line groove. Rotor from rotor core, squirrel cage and runner shaft 3 partial groups become. Location precision and the size precision of the case of main shaft will also directly affect the comprehensive precision of main shaft. Usually directly design bearing hole in the case of main shaft on, to add to pack generator stator must open at least one end. When the high speed of main shaft spins , any unbalanced quality of Xiao De arouses the vibration of high frequency of big electrical main shaft. Therefore the precision requirement of dynamic balancing of precise electrical main shaft reach G1 G0. 4 levels. For the dynamic balancing of this kind of grade, with conventional method, it is the insufficient dynamic balancing that need to still carry out whole after assembling to carry out dynamic balancing only respectively before assembling for every element on main shaft, even still design special voluntarily balanced system to realize the online dynamic balancing of main shaft. Additionally, when designing electrical main shaft must comply with structural symmetrical principle, key coupling and thread coupling strictly in electrical main shaft on have been prohibited use, and have adopted profit coupling generally, realize torque with this transmit. After profit coupling and thread coupling or key coupling compare have: Will not produce curved and torsion stress on main shaft, as the revolving precision of main shaft does not affect;
the sport control of 3.5 little electrical main shafts in the machine tool of numerical control in, electrical main shaft usually adopts the method of frequency control. Now, there are the ordinary drive and control of frequency conversion mainly , direct torque and control as well as the drive of vector control actuator control 3 kinds of control way.
Ordinary frequency conversion is scalar drive and control, it drives to control property, export power and rotational speed for permanent torque drives into direct ratio. It is thought of that the development performance of the ordinary control of frequency conversion is not enough to manage , in low speed, control performance is not good, export power is not enough to stabilize , also does not have C axle function. But price is cheap , has simple structure , is used in grinding machine and ordinary with high speed milling machine etc. normally. Vector control technology imitate the control of the motivation of direct current, with rotor magnetic field it is directional , use vector the method of alternating come to realize drive and control, have good development performance. Vector control actuator has great torque value when just starting , besides, electrical main shaft has simple structure and very little inertia, so, it is big to start acceleration, can realize to start after instant reach promise limit speed. It is two that this kind of actuator also have open loop and closed circuit, the latter can realize the feedback of location and speed , not only has better development performance , can still realize C axle function; And the development performance of the former is lacked , also does not have C axle function , but has relatively cheap price.
Directly torque control develops after being then vector control technology, is another as geting up to grow the new high performance alternating technology of speed adjustment, its
control thought is novel , construction of system is succinct and clear , more suits the drive of high speed electrical main shaft , can more satisfy the with high speed electrical high rotational speed of main shaft, the wide scope of speed adjustment and high speed instant to allow the requirement of development property and the property of static quiet that stops , has become a hot technology of alternating transmission field.
4 electrical main shaft develop tendency along with the high speed and technology of machine tool cut the needs of actual application and the development of technology, people have also put forward more and more high requirement for the performance of the electrical main shaft of machine tool, the technology of electrical main shaft develop tendency major expression in some following aspects:
( 1 ) to the at low speed big torque direction development and rate of great merit ( 2 ) to high accuracy and high rigidity direction development ( 3 ) to accurately directional( stop definitely) direction development ( 4 ) to fast from , stop direction development ( 5 ) to exceed with high speed direction development ( 6 ) to standardization direction development 。

电主轴技术水平分析
摘要：电主轴是高速数控加工机床的“心脏部件”，本文介绍了电主轴的工作原理、典型结构，阐述了电主轴的关键技术，总结了其发展趋势。

关键词：电主轴陶瓷球混合轴承油气润滑
1、概述
由于高速加工不但可以大幅度提高加工效率，而且还可以显著提高工件的加工质量，所以其应用领域非常广泛，特别是在航空航天、汽车和模具等制造业中。

于是，具有高速加工能力的数控机床已成为市场新宠。

目前，国内外各著名机床制造商在高速数控机床中广泛采用电主轴结构，特别是在复合加工机床、多轴联动、多面体加工机床和并联机床中。

电主轴是高速数控加工机床的“心脏部件”，其性能指标直接决定机床的水平，它是机床实现高速加工的前提和基本条件。

2、电主轴的工作原理、典型结构及优点
2.1 电主轴的工作原理
电主轴就是直接将空心的电动机转子装在主轴上，定子通过冷却套固定在主轴箱体孔内，形成一个完整的主轴单元，通电后转子直接带动主轴运转。

2.2电主轴的典型结构
电主轴单元典型的结构布局方式是电机置于主轴前、后轴承之间，其优点是主轴单元的轴向尺寸较短，主轴刚度大，功率大，较适合于大、中型高速数控机床；其不足是在封闭的主轴箱体内电机的自然散热条件差，温升比较高。

2.3电主轴的优点
电主轴省去了带轮或齿轮传动，实现了机床的“零传动”，提高了传动效率。

电主轴的刚性好、回转精度高、快速响应性好，能够实现极高的转速和加、减速度及定角度的快速准停（C轴控制），调速范围宽。

3、电主轴的关键技术
“电主轴”的概念不应简单理解为只是一根主轴套筒，而应该是一套组件，包括：定子、转子、轴承、高速变频装置、润滑装置、冷却装置等。

因此电主轴是高速轴承技术、润滑技术、冷却技术、动平衡技术、精密制造与装配技术以及电机高速驱动等技术的综合运用。

3.1电主轴的高速轴承技术
实现电主轴高速化精密化的关键是高速精密轴承的应用。

目前在高速精密电主轴中应用的轴承有精密滚动轴承、液体动静压轴承、气体静压轴承和磁悬浮轴承等，但主要是精密角
接触陶瓷球轴承和精密圆柱滚子轴承。

液体动静压轴承的标准化程度不高；气体静压轴承不适合于大功率场合；磁悬浮轴承由于控制系统复杂，价格昂贵，其实用性受到限制。

角接触球轴承不但可同时承受径向和轴向载荷，而且刚度高、高速性能好、结构简单紧凑、品种规格繁多、便于维修更换，因而在电主轴中得到广泛的应用。

目前随着陶瓷轴承技术的发展，应用最多的电主轴轴承是混合陶瓷球轴承，即滚动体使用Si3N4陶瓷球，采用“小珠密珠”结构，轴承套圈为GCr15钢圈。

这种混合轴承通过减小离心力和陀螺力矩，来减小滚珠与沟道间的摩擦，从而获得较低的温升及较好的高速性能。

陶瓷球混合轴承与钢球轴承相比，优点如下：
（1）陶瓷与钢组成的陶瓷球轴承摩擦性能非常好，能降低材料与润滑剂的应力。

（2）因陶瓷密度低，可降低运转时的离心力。

（3）陶瓷较低的热膨胀系数有效降低了轴承预加负荷的变化。

（4）陶瓷的弹性模量较高，可以提高轴承的刚性。

上述因素大幅度地延长了轴承的寿命和提升了轴承的运转极限速度。

3.2电主轴的润滑技术
高速电主轴必须采用合理的、可控制的轴承润滑方式来控制轴承的温升，以保证数控机床工艺系统的精度和稳定性。

采用滚动轴承的电主轴的润滑方式目前主要有脂润滑、油雾润滑和油气润滑等方式。

脂润滑在转速相对较低的电主轴中是较常见的润滑方式。

脂润滑型电主轴的润滑系统简单、使用方便、无污染、通用性强。

油雾润滑具有润滑和冷却双重作用，它以压缩空气为动力，通过油雾器将油液雾化并混入空气流中，然后把其输送到需要润滑的位置。

油雾润滑所需设备简单，维修方便，价格比较便宜，是一种普遍使用的高速电主轴润滑方式。

但它有污染环境，油耗比较高等缺点。

随着人们对环保要求的提高，油雾润滑方式必将逐渐被淘汰。

油气润滑技术是利用压缩空气将微量的润滑油分别连续不断地、精确地供给每一套主轴轴承，微小油滴在滚动和内、外滚道间形成弹性动压油膜，而压缩空气则可带走轴承运转所产生的部分热量。

实践表明在润滑中供油量过多或过少都是有害的，而前两种润滑方式均无法准确地控制供油量多少，不利于主轴轴承转速和寿命的提高。

而新近发展起来的油气润滑方式则可以精确地控制各个摩擦点的润滑油量，可靠性极高。

实践证明，油气润滑是高速大功率电主轴轴承的最理想润滑方法，但其所需设备复杂，成本高。

由于油气润滑方式润滑效果理想，目前已成为国际上最流行的润滑方式。

3.3电主轴的热源分析及其冷却
电主轴有两个主要的内部热源：内置电动机的发热和主轴轴承的发热。

如果不加以控制，由此引起的热变形会严重降低机床的加工精度和轴承使用寿命，从而导致电主轴的使用寿命缩短。

电主轴由于采用内藏式主轴结构形式，位于主轴单元体中的电机不能采用风扇散热，因此自然散热条件较差。

电机在实现能量转换过程中，内部产生功率损耗，从而使电机发热。

研究表明，在电机高速运转条件下，有近1/3的电机发热量由电机转子产生，并且转子产生的绝大部分热量都通过转子与定子间的气隙传入定子中；其余2/3的热量产生于电机的定子。

所以，对电机产生发热的主要解决方法是对电机定子采用冷却液的循环流动来实行强制冷却。

典型的冷却系统是用外循环水式冷却装置来冷却电机定子，将电机的热量带走。

角接触球轴承的发热主要是滚子与滚道之间的滚动摩擦、高速下所受陀螺力矩产生的滑动摩擦以及润滑油的粘性摩擦等产生的。

减小轴承发热量的主要措施：
（1）适当减小滚珠的直径减小滚珠直径可以减小离心力和陀螺力矩，从而减小摩擦，减少发热量。

（2）采用新材料比如采用陶瓷材料做滚珠，陶瓷球轴承与钢质角接触球轴承相比，在高速回转时，滚珠与滚道间的滚动和滑动摩擦减小，发热量降低。

（3）采用合理的润滑方式油气和油雾等润滑方式对轴承不但具有润滑作用，还具有一定的冷却作用。

3.4电主轴的设计和装配
电主轴要获得好的性能和使用寿命，必须对电主轴各个部分进行精心设计和制造。

电主轴的定子由具有高导磁率的优质矽钢片迭压而成，定子内腔带有冲制嵌线槽。

转子由转子铁芯、鼠笼和转轴三部分组成。

主轴箱的尺寸精度和位置精度也将直接影响主轴的综合精度。

通常将轴承座孔直接设计在主轴箱上，为加装电机定子，必须至少开放一端。

主轴高速旋转时，任何小的不平衡质量即可引起电主轴大的高频振动。

因此精密电主轴的动平衡精度要求达到G1~G0.4级。

对于这种等级的动平衡，采用常规的方法即仅在装配前对主轴上的每个零件分别进行动平衡是远远不够的，还需在装配后进行整体的动平衡，甚至还要设计专门的自动平衡系统来实现主轴的在线动平衡。

另外，在设计电主轴时，必须严格遵守结构对称原则，键联接和螺纹联接在电主轴上被禁止使用，而普遍采用过盈联接，并以此来实现转矩的传递。

过盈联接与螺纹联接或键联接相比有：不会在主轴上产生弯曲和扭转应力，对主轴的旋转精度没有影响；主轴的动平衡易得到保证等优点。

转子与转轴之间的过盈联接分为两类，一类是通过套筒实现的，此结构便于维修拆卸；另一类是没有套筒，转子直接过盈联接在转轴上，此类联接转子装配后不可拆卸。

由于内孔与转轴配合面之间有很大的过盈量，所以转子与转轴可以采用转轴冷缩和转子热胀法装配。

带有套筒的联接拆卸时，需向转子套筒上预留的油孔中高压注油，迫使转子的过盈套筒涨开，即可顺利拆卸下电机的转子。

电机定子通过一个冷却套固定装在电主轴的箱体中。

3.5电主轴的运动控制
在数控机床中，电主轴通常采用变频调速方法。

目前主要有普通变频驱动和控制、矢量控制驱动器的驱动和控制以及直接转矩控制三种控制方式。

普通变频为标量驱动和控制，其驱动控制特性为恒转矩驱动，输出功率和转速成正比。

普通变频控制的动态性能不够理想，在低速时控制性能不佳，输出功率不够稳定，也不具备C轴功能。

但价格便宜、结构简单，一般用于磨床和普通的高速铣床等。

矢量控制技术模仿直流电动机的控制，以转子磁场定向，用矢量变换的方法来实现驱动和控制，具有良好的动态性能。

矢量控制驱动器在刚启动时具有很大的转矩值，加之电主轴本身结构简单，惯性很小，故启动加速度大，可以实现启动后瞬时达到允许极限速度。

这种驱动器又有开环和闭环两种，后者可以实现位置和速度的反馈，不仅具有更好的动态性能，
还可以实现C轴功能；而前者动态性能稍差，也不具备C轴功能，但价格较为便宜。

直接转矩控制是继矢量控制技术之后发展起来的一种新型的高性能交流调速技术，控制思想新颖，系统结构简洁明了，适合于高速电主轴的驱动，能满足高速电主轴高转速、宽调速范围、高速瞬间准停的动态特性和静态特性的要求，已成为交流传动领域的一个热点技术。

4、电主轴的发展趋势
随着机床技术、高速切削技术的发展和实际应用的需要，人们对机床电主轴的性能也提出了越来越高的要求，电主轴技术的发展趋势主要表现在以下几个方面：（1）向高速大功率和低速大转矩方向发展
（2）向高精度、高刚度方向发展
（3）向精确定向（准停）方向发展
（4）向快速起、停方向发展
（5）向超高速方向发展
（6）向标准化方向发展
The electrical unit of high speed main shaft
The representative application of high speed processing is to carry out milling with the milling cutter of hard alloy of little diameter for the of aluminium alloy, model and the mould of various materials, the rotational speed of machine tool of main shaft is to cut speed scope and the / rotational speed of cutting tool of main shaft that calculated according to the diameter of milling cutter of this speed and difference reasonably according to the economy that the modern material of cutting tool can reach to determine. Evidently only cuting Tai or nickel alloy , because of cutting tool can reach cut speed reasonably lower ( 300 m/min below ), the highest rotational speed of cutter spindle but in r/min of ten thousands below besides, other materials cut the / highest rotational speed of cutting tool of main shaft that will be beged in r/min of ten thousands more than, even ask to reach r/min of fifty thousands to r/min of eighty thousands. As this high rotational speed of main shaft, with the main transmission structural( generator add positive drive and ship of leather belt) way that general machine tool uses , is impossible to realize , normally need to adopt from the generator of frequency control and the main shaft of machine tool integrated together " the electrical main shaft claimed " direct drive come to realize.
Electrical main shaft realizes the wide speed adjustment of main shaft through exchanging frequency control and vector control. It's advantage is not only easier main transmission structure, reduce the system of main transmission turn inertia, and have reduced power comsumption , have raised the ability that realizes the higher speed of main shaft and adds deceleration degree , so can also realize to decide angle allow fast Ding ( C axle control ) function, this is very important for with high speed processing machine tool.
Certainly, the design production of the high speed of main shaft will be
concerned with a lot of special problems, as lubrication way and the structural type of the supporting of main shaft ( generator rotor ) generator give out heat with cooling measure, the problem of dynamic balancing as well as the connection of main shaft and cutting tool, it is studied and solved that luckily these problems has had a lot of research units and has gone on , the with high speed electrical unit of main shaft is being domestic and international to have got the special manufacturer domestic production that has carried out specialization and seriation , the design producer of machine tool needs only that according to processing, object asks , determines the needed rotational speed of main shaft with torque scope come choose reasonably have been.
高速电主轴单元
高速加工的典型应用是以小直径的硬质合金铣刀来对各种材料的模具,模型和铝合金件进行铣削,机床主轴转速是根据现代刀具材料所能达到的经济合理切削速度范围(图3)和按此速度及不同的铣刀直径所计算得的刀具/主轴转速(图4)来确定.可见除切削钛或镍合金时,由于刀具所能达到的合理切削速度较低(300m/min以下),刀具主轴最高转速可在10000r/min以下外,其他材料的切削所要求的刀具/主轴最高转速都在10000r/min以上,甚至要求达到50000r/min至80000r/min.如此高的主轴转速,采用一般机床用的主传动结构(电机加皮带轮和齿轮传动)方式是不可能实现的,一般都需采用由变频调速电机和机床主轴集成在一起的所谓"电主轴"直接驱动来实现.
电主轴是通过交流变频调速和矢量控制来实现主轴的宽调速的.它的优点不仅是简化了主传动结构,减少主传动系统的转动惯量,而且降低了功耗,提高了实现更高主轴速度和加减速度的能力,从而也可实现定角度的快速准仃(C轴控制)功能,这对高速加工机床是十分重要的.
当然,高速主轴本身的设计制造会涉及许多特殊问题,如主轴(电机转子)支承的结构型式和润滑方式,电机的发热和冷却措施,主轴和刀具的连接以及动平衡问题等,好在这些问题已有许多科研单位进行了研究和解决,高速电主轴单元在国内外均有了专门的生产厂家进行了专业化,系列化的生产,机床设计制造者只需根据加工对象要求,确定所需的表面主轴转速和扭具范围来合理地选用就是了.。