毕业设计（论文）-八轴转塔式数控加工中心设计.doc

河南科技大学毕业设计论文转塔式数控加工中心设计摘 要数控机床是一种高科技的机电一体化产品，是现代制造技术中不可缺少的生产手段。随着科技的不断发展，数控机床在国内也进入了实用化阶段，但在目前我国许多国营大厂都有一批老机床，若在老机床的基础上对其进行改造，配以数控技术，这样不仅可降低成本，而且可提高老机床的使用寿命。因此，我们毕业设计的题目就是将普通铣床改为集镗、铣、钻为一体的八轴转塔式简易加工中心，实现不用人工换刀的情况下，短时间内进行镗、铣、钻的转换，这样不仅可以提高生产效率和加工精度，并且还可以降低成本。我主要负责机床的整体布局和八轴转塔自动换刀装置的设计。在机床的整体布局方面，我从人机工程学和产品造型两方面对机床进行设计。八轴转塔自动装置的工作原理是在八个轴上事先根据工序的安排将加工中所需要的刀具装夹好，当将油注入中心油缸后，产生压力带动整个转塔头使八轴转塔旋转，使其实现自动换刀的功能。这套简易的数控加工中心也应用了近年来才发展起来的变频技术，从而提高了其中的科技含量。由于现在国内的国营大厂都面临老机床淘汰的情况，因此在老机床的基础上进行数控改造是很有市场前景的，从而进行这次毕业设计也是比较实用的。关键词：数控技术，八轴转塔头，变频技术，自动换刀DESIGN OF TURRET NUMERICAL CONTROL MACHINING CENTERABSTRACTThe numerical control lathe is the kind of Hi-Tech and electromechanics integrated products, is the indispensable means of production in the modern manufacturing technology. With the constant development of science and technology, the numerical control lathe has entered practical stage of taking too at home. But at present in our country, a lot of state-run factories have a batch of old lathes, if we transform to them on the basis of old lathes and mix them with numerical control technology. We can not only decrease the costs, but also raise the service lives of the old lathes. However, our topics of graduation project is to switch the ordinary milling machines to turret numerical control machining center, which have the functions of boring, milling, and drilling. They can realize to the transfer of boring, milling and drilling in the short time in the condition of being not artificial to transfer knives. It can not only improve production efficiency and machining accuracy, but also decrease costs. Im responsible for the whole overall arrangements of lathe and the design of eight axles turret numerical control machining center. I apply the knowledge of man-machine engineering and model of the products into the whole overall arrangements of lathe. The operation principles of eight axles turret numerical control machining center is to insert cutters in the axles according to the arrangement of working procedure in advance of machining, and after inject the oil into the jar of center,the pressure make eight axles turret to be transferred entirely, this make it to realize the function of transfer knives automatically. This set of simples numerical control machining center have used the frequency conversion technology which was developed in recent years too, thus this improved the scientific and technological content among them. Because the domestic state-run factories all face the situation that the old lathes need eliminates now, so there are market prospects very much to carry on the transformation of numerical control on the basis of old lathe, thus it is practical for us to carry on this graduation project. KEY WORDS: the technology of numerical control, eight axles turret, frequency conversion technology, change the knife automaticallySLEEVE BEARINGSBEARING MATERIALS The antifriction properties of rubbing pairs are considered in conjunction with the materials of the shaft and bearing, and the lubricant. Bearing materials are chosen for application in a pair with a steel or, much less frequently, cast iron shaft journal. Owing to the fact that the cost of shafts is, as a rule, higher than that of the bearing liners (especially in the case of crankshafts and other main shafts), their wear must be less than that of the liners. The higher the hardness of the shaft journals, the more reliable their performance. As a rule, journals are hardened. Journals running in high-speed bearings are hardened to a high hardness, 55 to 60 Rc (following carburizing). Integrated requirements, complying with the basic criteria of bearing performance, can be made to bearing materials. Thus, they must: (a) be antifrictional, a property characterized by the coefficient of friction in operation in a pair with the material of the shaft journal, and by the temperature at the working surface; (b) have high wear resistance; and (c) have high fatigue strength. Of importance in meeting these integrated requirements are the following basic properties of bearing materials: (a) thermal conductivity, to provide intensive heat disposal from the friction surfaces, and a low coefficient of linear expansion to avoid large changes in the clearances in the bearings during operation; (b) capacity for being run in readily, which reduces edge and local pressures resulting from elastic deformation and errors in manufacture; (c) good wettability with oil and the capacity for forming stable and rapidly restorable oil films on its surfaces; (d) good corrosion resistance; (e) low modulus of elasticity. Also of basic importance are processing properties, such as castability, machinability, etc. The most favorable structure for an antifriction material is one having a plastic matrix into which hard components are embedded. With respect to their chemical composition, antifriction bearing materials can be classified into the following large groups: (a) metallic materials: babbitts, bronzes, zinc-base alloys, aluminium-base alloys and antifriction cast irons; (b) sintered metal powders; (c) nonmetallic materials: plastics, wood laminates, rubbers, etc. Bearing Metals. Babbitts are high-quality bearing alloys that have been used for many years in engineering. They are based on tin or lead and are characterized by their low hardness (they are used for casting into a support or housing), good running-in properties, and relatively lower requirements as to the hardness of the shaft journals and to the state of the rubbing surfaces. High-tin babbitts, grades B83, B89, etc. are to be applied for high running speeds and high pressures. They allow operation at pressures up to p=200 kgf/cm2 and pv= 1000 kgf-m/cm2-s. Toavoid burning-out, babbitts are used for temperatures up to 110C only. Typical applications are in the bearings of steam turbines, and of powerful electric generators and motors. The use of high-tin babbitts leads to minimum wear of the shaft journals. Shortcomings of high-tin babbitts are their relatively low fatigue strength, which restricts their application in impact-type machinery and high-speed piston machines, and the impossibility of applying them in thin layers because of their large crystals. Soviet automobiles use bearing liners with a layer of babbitt, grade COC6-6 (88% lead, 6% tin and 6% antimony), and a cermet sublayer, sintered of a powder with 40% Ni and 60% Cu, on a steel backing. There is excellent cohesion between the layers because the sublayer is impregnated with the babbitt which forms, with the sintered metal, a substantially increased cohesion surface. On the other side, the sublayer diffuses into the steel backing. This grade of babbitt has an increased fatigue strength and, owing to the absence of hard components, its use leads to less shaft wear. Another advantage is that it lends itself to high-production manufacturing techniques (pressforming from strip stock). A calcium babbitt, grade BR2, is used in diesel engine manufacture. Among those long in use in the engineering industries are the tin-lead babbitts, grades B16 and BH, which have properties close to those of the high-tin babbitts (p=150 kgf/cm2 and pv =500kgf-m/cm2-s). Calcium babbitt, grade BK, finds application for medium duty. It contains no tin and is used, for instance, for babbitting the bearings of railway rolling stock. A less expensive babbitt, grade BC, is used for light duty applications. Bronzes. At high speeds and pressures (up to p=300 kgf/cm2) and, in particular, for variable loads typical of internal-combustion engines, a leaded bronze, grade Bp.C-30, is used. It has a higher fatigue strength than the high-tin babbitts. Leaded bronze makes higher requirements than the babbitts do to the hardness of the shaft journals (hardening is compulsory),to the surface finish of the journals and liners, and also to the lubricants since oxidized oils cause corrosion. Shaft wear is higher than that with babbitt liners. If the lead content is increased to 35%,the wear can be reduced. Leaded bronze is applied to strip stock from which the liners are pressformed or it is cast into the liner. Owing to the danger of corrosion, the use of leaded bronze has been curtailed in recent years. The working surface of the liners of critical bearings is coated with a thin running-in layer of an alloy of lead with tin, or of indium or tin. Universal tin bronzes of the Bp. O10-1 type provide for efficient performance at high pressures and medium speeds. However, owing to the high tin content, their application is limited. This bronze is not to be recommended for use in bimetallic bearing liners. Secondary tin-zinc-lead bronzes (i.e. ones obtained by remelting), for instance, grade Bp. OC6-6-3, have found extensive application and have proved quite satisfactory for medium duty. Aluminium-iron bronzes are used to some extent for bearings subject to considerable pressures at low speeds and operating with a hardened shaft journal. In recent years, aluminium-base bearing alloys have come into use because they are more economical due to the low cost of the basic material. These alloys have low density, low corrosion resistance, high thermal conductivity, low modulus of elasticity and a high fatigue strength. The use of these alloys increased considerably after a technique was developed for applying them to a steel backing by a rolling process. Tinless aluminium bearing alloys have sufficiently high antifriction properties, but at high speeds their resistance to scoring is not very high; they are sensitive to dirt in the oil and have a high coefficient of linear expansion. The most widely used of these alloys in the USSR is grade ACM which is found in the bearings of tractor engines. No favorable results were obtained, however, when attempts were made to apply them in the bearings of automobile engineswhich run at higher speeds.The most promising bearing materials are the aluminium-tin antifriction alloys which have high antifriction properties and high fatigue strength. In use are alloys grade AO9-2 (9%tin, 2%copper, cast in and used as a monometal), AO9-2B (cast in and used as a bimetal), AO9-1(made by rolling and used as a bimetal). and AO20-1 (made by rolling and used as a bimetal).These alloys have optimal structure and are capable, in cases of oil starvation, of forming a protective film of tin on the journal. Alloys AO9-1 and AO9-2, for example, are being efficiently employed in the bearings of internal-combustion engines of diesel locomotives, ships and heavy-duty tractors.Of the zinc bearing alloys, the best known is grade AM10-5(10% aluminium,5% copper and the remainder zinc),Owing to its satisfactory antifriction properties, abundancy of its constituent materials, low cost and simple manufacture, this alloy is widely used in place of type 16 babbitts and bronzes. Shortcomings of this alloy are its poor running-in properties, and the consequently higher requirements made to the accuracy of the bearing surfaces, and the high coefficient of linear expansion. The highest permissible temperature of such bearings is 80C. The alloy is used either for cast-in or for pressfitted liners.A new bearing alloy is grade AM9-1.5;a technique has been developed for making bimetallic strip stock. Tests show that it has high wear resistance.Polymetallic multiple-layer bearings are being employed to an ever-increasing extent. Bearings are used, for example, in automobile engines that consist of a steel backing, a 0.25-mm layer of leaded bronze, serving as a compliant cushion with good thermal conductivity and fatigue strength, an extremely thin layer of nickel or a copper-zinc alloy which prevents diffusion of the tin, and, finally, a surface antifriction layer of a tin-lead alloy, 25 microns thick, which has excellent running-in properties.Antifriction cast iron (USSR Std GOST 1585-70) can be applied for low-speed moderately loaded bearings. The hardness of the shaft journals must be higher than that of the cast iron liners. The working surfaces should be carefully run in using a colloidal mixture of graphite in oil. The permissible pressures in these bearings drop sharply with an increase in running speed .Cast iron liners are especially sensitive to edge pressures, impact loads, poor lubricant, etc. Sulphocyaniding has proved to be an effective measure for improving their performance.Sintered Metal Powders (cermets). These materials, made of metal powders by compression moulding at high pressure and subsequent sintering at high temperature, are used in connection with their satisfactory operation with poor lubrication. These materials have a porous structure in which the pores occupy from 15 to 40% of the volume. In the finished bearing these pores are filled with oil (by special impregnation of the liners with hot oil). The most widely employed are the iron-graphite liners consisting of 1 to 3% graphite and the remainder, iron. Also used are bronzegraphite liners with 10% tin,1 to 4% graphite and the remainder, copper, but their properties differ only slightly from the much less expensive iron-graphite liners.Their primary field of application is dictated by their property of self-lubrication: these are mainly bearings that are difficult or impossible to lubricate reliably by ordinary means.At low pressures and speeds, sintered bearings can operate for long periods of time with their only lubrication being from the oil in the pores of the liners. Permissible running conditions for iron-graphite bearings having an average porosity of 20 to 25% and subject to a steady load are:v, m / s. 0.5 1 1.5 2 2.5 3 3.5 4p, kgf / cm2. 70 65 60 55 45 35 18 8Nonmetallic Materials. Nometallic materials employed for the liners of bearings are: (a) plastics, (b) compressed wood (laminated wood), (c) various hardwoods (lignum vitae, boxwood, oak, etc.), (d) rubber, and (e) graphite materials.An essential feature of most nonmetallic bearing materials, due to their low thermal conductivity ,is that the best lubricant for them is water which ensures proper cooling. Oil or an emulsion is required only at low speeds and high pressures.When water is used as the lubricant, corrosion of the shaft in the bearings can be avoided by introducing a plastic lubricant (for instance, grease) into the bearing before stopping the machine, or by coating the shaft with stainless steel.Reasons for applying nonmetallic bearing materials are: (a) no chemical affinity with the shaft material, (b) good running-in properties, (c)products of wear are soft, and (d) the feasibility of lubricating with water or any other fluid which may be the working medium in the machine.The main fields of application of plastic bearing liners are:(1) bearings for which it is impossible to use a fluid lubricant and for which complete or partial self-lubrication is required(automobile suspensions, and the bearings of certain chemical and textile machines);(2) bearings lubricated by the working medium (submersible pumps and certain food-processing machines);(3) bearings of heavy low-speed machinery in which fluid friction running conditions are not always attainable. This may be due to frequent starts and stops, low speeds, or high local pressures resulting from elastic deformation or manufacturing errors.目 录前 言 1第一章 技术参数分析及方案的确定1.1技术参数分析 21.2 初步方案制定 21.2.1 机床总体方案的制定 21.2.2 对于主轴部件的确定 31.3 八轴转塔头的结构设计 3第二章 设计计算2.1 电动机的选择52.2 计算总传动比52.3 计算各传动装置的运动和动力参数52.4 带传动的设计62.5 锥齿轮传动的设计72.6 圆柱齿轮设计 102.7 主轴部分的设计计算 122.8 轴的设计 142.9 轴承的计算 192.10 键强度的校核22第三章 操作/使用说明3.1 基本要求 243.2 操作注意事项 25第四章 性能分析及设计总结26第五章 小结 27参考文献28 致谢29附录30前 言在这次毕业设计中接到的课题是对数控机床的部分进行设计，我设计的是八轴转塔自动换刀装置。接到课题后，进行了充分的调研工作，查阅了大量的相关资料。数控机床是一种高科技的机电一体化产品，集微电子技术、计算机技术、自动控制技术及伺服驱动技术、精密机械技术于一身的高度机电一体化产品，是现代机床技术水平的重要标志，是当前世界机床技术进步的主流。数控机床随着微电子技术、计算机技术、自动控制技术的发展而得到飞跃的发展。目前几乎所有的传统机床都有数控机床的品种，数控机床逐渐成为机械工业技术改造的首选设备。但我们了解到我国的国营大厂仍有一批老机床，随着数控机床的发展这批老机床一定会被淘汰，但若对其进行改造，将这批老机床改造成数控机床，这样不但能延长这批老机床的寿命、降低了成本，而且还能满足机床自动化的要求。因此，我们准备对普通升降式铣床进行改造。通过查阅有关书籍及大量的资料，我们将升降式铣床改为八轴转塔式简易加工中心，实现不人工换刀的情况下短时间内进行铣、镗、钻的转换。通过这次毕业设计，我不但对数控机床的结构有了系统的了解，并且还掌握了一种工业系统设计的思维方式，对今后的工作及实践都有帮助。第一章 技术参数分析及方案的制定1.1 技术参数分析由于主轴部件直接参与切削，因而数控机床的加工质量很大程度上要靠它保证。因此，主轴部件主要参数有以下几项： 主轴部件旋转精度。表现在工作时主轴回转中心位置的不断变化，即“主轴轴心漂移现象”，应通过采用回转精度好的轴承和提高与轴承配合表面的精度等方法来提高。 静刚度。静刚度不足会造成加工的尺寸误差和形状误差，并且会影响主轴部件的工作性能和寿命。因此，应通过适当加粗主轴直径、选择最佳跨距等方法来提高静刚度。 抗振性。由于传动齿轮中存在缺陷或切削过程的再生自振等所引起的冲击或交变力的干扰，从而使主轴产生振动，这不但会影响加工精度和表面质量，甚至会使加工无法进行。因此，应提高主轴的刚度。选用阻尼比大的主轴轴承，并且要求主轴部件的运动件要有足够的精度并进行动平衡。 热稳定性。主轴部件工作时，由于与主轴相联系的传动件或刀具传来的切削热等原因，主轴部件的温度将上升，造成主轴部件的变形，影响主轴部件的工作性能。因此，应通过减少部件中的发热量，减少外部热量传入及创造良好的散热条件来提高热稳定性。1.2 初步方案制定1.2.1 机床总体方案的制定机床主机是数控机床的主体，它包括床身、底座、立柱、工作台、主轴箱、进给机构、刀架及自动换刀装置等机械部件。它是在数控机床上自动完成各种切削加工的机械部分。通常用提高结构系统的静刚度、增加阻尼、调整结构件质量和固有频率等方法来提高机床主机的刚度和抗振性，使机床主机能适应数控机床连续自动地进行切削加工的需要。采取改善机床结构布局、减少发热、控制温升及采用热位移补偿等措施，可减少热变形对机床主机的影响；采用高性能的主轴伺服驱动和进给伺服驱动装置，使数控机床的传动链缩短，可简化机床机械传动系统的结构；采用高传动效率、高精度、无间隙的传动装置和传动元件，如：滚动丝杠螺母副、滑动导轨等传动元件。辅助装置作为数控机床的配套部件，是保证充分发挥数控机床功能所必需的配套装置。辅助装置包括：液压装置，冷却、润滑装置，防护、照明等。液压装置是应用液压系统，使机床完成自动换刀所需的动作，实现运动部件的制动，完成工作台的自动夹紧、松开，工件、刀具定位表面的自动吹屑等辅助功能。排屑装置的作用是将切屑从加工区域排出。迅速有效