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減速器箱體專用機(jī)床夾具及移動式交換工作臺設(shè)計
Design of the reducer box’s dedicated fixture and mobile switching table
長春理工大學(xué)光電信息學(xué)院
畢業(yè)設(shè)計(論文)題目申報表
院 別 機(jī)電工程分院
教 研 室 機(jī)械工程教研室
指導(dǎo)教師 陳玲 職稱 教授
職稱
2009年 12月 20日
題目名稱
減速器箱體專用機(jī)床夾具及移動式交換工作臺設(shè)計
題 目
類 別
設(shè)計類
√
題目
性質(zhì)
結(jié)合實(shí)際
√
專
業(yè)
機(jī)械制造及其自動化
參加本題目
學(xué)生人數(shù)
1
論文類
虛擬題目
題目來源:自擬
教師準(zhǔn)備:從事機(jī)械設(shè)計及其自動化領(lǐng)域的教學(xué)及研究30年,自1999年起自擬并指導(dǎo)該方向的畢業(yè)設(shè)計題目整十年,有一定的研究基礎(chǔ)。
主要培養(yǎng)學(xué)生的能力:文獻(xiàn)查閱及實(shí)際調(diào)研能力;外文資料翻譯能力;基礎(chǔ)知識和專業(yè)知識的綜合運(yùn)用能力;數(shù)據(jù)資料的采集,處理與分析能力;計算機(jī)使用能力。
題目內(nèi)容針對減速箱體零件數(shù)控加工時專用的移動式交換工作臺進(jìn)行設(shè)計。目的是針對減速箱體的加工,設(shè)計專用機(jī)床夾具
要求:1
缸徑/mm: φ63 矩形和三角形(V-平)導(dǎo)軌
最大行程/mm: 50 傳遞功率 P=4.5(kW) 傳遞轉(zhuǎn)矩 T=29.43(N·m)
工作壓力/MPa: 0.05~1.0
使用溫度范圍/℃: -5~60
工作介質(zhì): 空氣
實(shí)
踐
環(huán)
節(jié)
安
排
實(shí)習(xí)
長春一汽三周
實(shí)驗(yàn)
計算機(jī)應(yīng)用
CAD繪圖45機(jī)時
1. 于駿一 鄒青主編《機(jī)械制造技術(shù)基礎(chǔ)》 機(jī)械工業(yè)出版社 2007
2. 譚慶昌 趙洪志主編《機(jī)械設(shè)計》 高等教育出版社 2005
3. 徐鴻本主編《機(jī)床夾具設(shè)計手冊》 遼寧科學(xué)技術(shù)出版社 2004
4. 鄧星鐘主編《機(jī)電傳動控制》 華中科技大學(xué)出版社 2001
5. 劉順安主編,《液壓傳動與氣壓傳動》 吉林科學(xué)技術(shù)出版社 1999
6. 高春甫 張宏穎主編《機(jī)電控制系統(tǒng)分析與設(shè)計》 科學(xué)出版社 2007
7. 《機(jī)床設(shè)計手冊》 機(jī)械工業(yè)出版社 1986
8. 《機(jī)械設(shè)計手冊.單行本.氣壓傳動與控制》 機(jī)械工業(yè)出版社 2007
9. 《機(jī)械設(shè)計手冊.單行本.機(jī)電一體化系統(tǒng)設(shè)計》 機(jī)械工業(yè)出版社 2007
10. 《機(jī)械設(shè)計手冊軟件版v3.0》
11. Mechanical Engineer's Handbook . MARGHITU, D. B. (2001)
12. Rules of Thumb for Mechanical Engineers . POPE, J. E. (1996)
13. Tribology in Machine Design . STOLARSKI, T. A. (1990)
14. Industrial Control Wiring Guide . MERCER, R. B. (2001)
15. Combination Machine- Engineering Principles . REIMPELL, J. (2001)
16. The Science and Technology of CNC . TANAKA, K. (1999)
教研室主任
審批簽字
分 院 院 長
審批簽字
注:題目類別和題目性質(zhì)請用符號√填在相應(yīng)欄內(nèi)。
長春理工大學(xué)光電信息學(xué)院學(xué)生畢業(yè)設(shè)計(論文)登記表
分院
機(jī)電工程分院
專業(yè)
機(jī)械制造及其自動化
班級
06234
學(xué)生姓名
茅樂
指導(dǎo)教師
陳玲
設(shè)計(論文)起止日期
2010.3.8 - 2010.6.20
教研室主任
陳玲
題目內(nèi)容針對減速箱體零件數(shù)控加工時專用的移動式交換工作臺進(jìn)行設(shè)計。目的是針對減速箱體的加工,設(shè)計專用機(jī)床夾具
要求:1
缸徑/mm: φ63 矩形和三角形(V-平)導(dǎo)軌
最大行程/mm: 50 傳遞功率 P=4.5(kW) 傳遞轉(zhuǎn)矩 T=29.43(N·m)
工作壓力/MPa: 0.05~1.0
使用溫度范圍/℃: -5~60
工作介質(zhì): 空氣
設(shè)計題目
減速器箱體專用機(jī)床夾具及移動式交換工作臺設(shè)計
一、課題研究的目的與意義
本課題針對臥式機(jī)床三面鉆孔設(shè)計機(jī)床夾具,設(shè)計減速器箱體零件數(shù)控加工時專用的移動式交換工作臺。
變速器箱體在整個減速器總成中的作用是起支撐和連接的作用的,它把各個零件連接起來,支撐傳動軸,保證各傳動機(jī)構(gòu)的正確安裝。變速器箱體的加工質(zhì)量的優(yōu)劣,將直接影響到軸和齒輪等零件位置的準(zhǔn)確性,也為將會影響減速器的壽命和性能。
變速器箱體是典型的箱體類零件,其結(jié)構(gòu)和形狀復(fù)雜,壁薄,外部為了增加其強(qiáng)度加有很多加強(qiáng)筋。有精度較高的多個平面、軸承孔,螺孔等需要加工,因?yàn)閯偠容^差,切削中受熱大,易產(chǎn)生震動和變形。
本課題研究的是對減速箱體零件數(shù)控加工時專用的移動式交換工作臺進(jìn)行設(shè)計,由于變速箱體上多加工面以及加工孔,所以加工方法的選擇直接影響加工效率,而機(jī)床夾具和工作臺的性能又會直接影響到機(jī)械加工的復(fù)雜程度和加工工序數(shù)和工步數(shù),從而會影響到變速箱體的性能和機(jī)加工效率。因而,本課題的研究無論是對變速箱生產(chǎn)工廠,還是對變速箱使用機(jī)械都具有非常重要的意義。
二. 國外的減速器,以德國、丹麥和日本處于領(lǐng)先地位,特別在材料和制造工藝方面占據(jù)優(yōu)勢,減速器工作可靠性好,使用壽命長。但其傳動形式仍以定軸齒輪傳動為主,體積和重量問題,也未解決好。最近報導(dǎo),日本住友重工研制的FA型高精度減速器,美國Alan-Newton公司研制的X-Y式減速器,在傳動原理和結(jié)構(gòu)上與本項(xiàng)目類似或相近,都為目前先進(jìn)的齒輪減速器。當(dāng)今的減速器是向著大功率、大傳動比、小體積、高機(jī)械效率以及使用壽命長的方向發(fā)展。因此,除了不斷改進(jìn)材料品質(zhì)、提高工藝水平外,還在傳動原理和傳動結(jié)構(gòu)上深入探討和創(chuàng)新,平動齒輪傳動原理的出現(xiàn)就是一例。減速器與電動機(jī)的連體結(jié)構(gòu),也是大力開拓的形式,并已生產(chǎn)多種結(jié)構(gòu)形式和多種功率型號的產(chǎn)品。目前,超小型的減速器的研究成果尚不明顯。在醫(yī)療、生物工程、機(jī)器人等領(lǐng)域中,微型發(fā)動機(jī)已基本研制成功,美國和荷蘭近期研制的分子發(fā)動機(jī)的尺寸在納米級范圍,如能輔以納米級的減速器,則應(yīng)用前景遠(yuǎn)大。
國內(nèi)的減速器生產(chǎn)起步晚,60年代生產(chǎn)、設(shè)計技術(shù)采用的是前蘇聯(lián)30~40年代的技術(shù),“七五”期間,國家投入大量財力、物力研制新型減速器,要求達(dá)到國外80年代的水平,“十五”期間,由于國家采取了積極的財政政策,拉動了內(nèi)需,固定資產(chǎn)投資力度加大,各行業(yè)的發(fā)展駛?cè)肓丝燔嚨馈L貏e是基礎(chǔ)建設(shè)的投資,使冶金、電力、建筑機(jī)械、建筑材料、能源等加快了發(fā)展,因此,對減速機(jī)的需求也逐步擴(kuò)大。預(yù)計“十一五”期間,隨著國家對機(jī)械制造業(yè)的重視,重大裝備國產(chǎn)化進(jìn)程的加快以及城市改造、場館建設(shè)等工程項(xiàng)目的開工,減速機(jī)的市場前景看好,整個行業(yè)仍將保持快速發(fā)展態(tài)勢,尤其是齒輪減速機(jī)的增長將會大幅度提高,這與進(jìn)口設(shè)備大多配套采用齒輪減速機(jī)有關(guān)。但總體而言,國內(nèi)企業(yè)同國外減速器系列產(chǎn)品的開發(fā)及更新工作近幾年進(jìn)展緩慢,與國外同行在此方面的差距有拉大的趨勢。而且與市場的需求也很不適應(yīng),長期以來,我國自主生產(chǎn)的減速傳動設(shè)備多數(shù)屬于通用性產(chǎn)品,人們往往把這一類設(shè)備定位于中低端產(chǎn)品。隨著經(jīng)濟(jì)全球化步伐的加快,德國、法國、日本等國家的傳動設(shè)備制造巨頭紛紛搶灘中國,占領(lǐng)我國減速機(jī)的中高端市場,國產(chǎn)減速機(jī)要想在國內(nèi)市場上與國外先進(jìn)減速機(jī)品牌競爭,甚至超越,還需要在技術(shù)等方面經(jīng)歷很長一段時間的發(fā)展道路。
三,擬采取的研究路線
近一周的時間內(nèi),在網(wǎng)上找尋了《銑床的萬能旋轉(zhuǎn)工作臺》《數(shù)控萬能旋轉(zhuǎn)工作臺加工》《[教育]加工工作臺》等相關(guān)視頻,再結(jié)合了之前在汽車廠參觀實(shí)習(xí)的觀摩情況,使得我對轉(zhuǎn)動式工作臺有了一個初步的印象與了解,采用移動式交換式工作臺可以提高加工效率,減少人工裝夾工件次數(shù),減少裝夾誤差,減少裝夾時間,提高生產(chǎn)效率。
4、 工作進(jìn)度
第一周 收集資料
第二周 調(diào)研
第三周 閱讀資料 撰寫開題報告
第四、五周 功能原理分析
第六、七周 總體方案設(shè)計
第八到十周 結(jié)構(gòu)方案設(shè)計
第十一、十二周 設(shè)計計算
第十三到十五周 計算機(jī)繪圖
第十六周 設(shè)計說明書
參考文獻(xiàn):
[1]王啟平.機(jī)床夾具設(shè)計[M] .哈爾濱.哈爾濱工業(yè)大學(xué)出版社,2005.
[2]劉治平.機(jī)電傳動控制[M].天津.天津大學(xué)出版社,2007.
[3]周飛.機(jī)械制造技術(shù)[M].北京.電子工業(yè)出版社,2007.
[4]馬恩.液壓與氣壓傳動[M].北京.電子工業(yè)出版社,2007.
[5]何存興.液壓傳動與氣壓傳動[M].武漢.華中科技大學(xué),2000.
[6]韓秋實(shí).機(jī)械制造技術(shù)基礎(chǔ)[M].北京.機(jī)械工業(yè)出版社,2004.
[7]徐灝.機(jī)械設(shè)計手冊Ⅱ[M].北京.機(jī)械工業(yè)出版社,1991.
[8]徐灝.機(jī)械設(shè)計手冊Ⅴ[M].北京.機(jī)械工業(yè)出版社,1991.
[9]常曉玲.電氣控制系統(tǒng)與可編程控制器[M].北京.機(jī)械工業(yè)出版社,2004.
[10] Andrew Wood.Bosch Rexroth to Focus on CNC and Machine Tool Auto mation At IMTS 2008[J].2008.
[11] R.Whalley.Machine tool modelling and profile following performance[J].2008.
[12] High-speed machining and demand for the development.
指導(dǎo)教師審閱意見:
2010 年 3 月 8 日
記事:
指導(dǎo)教師審閱意見:
2010年 6 月 15 日
High-speed machining and demand for the development
High-speed machining is contemporary advanced manufacturing technology an important component of the high-efficiency, High-precision and high surface quality, and other features. This article presents the technical definition of the current state of development of China''s application fields and the demand situation.
High-speed machining is oriented to the 21st century a new high-tech, high-efficiency, High-precision and high surface quality as a basic feature, in the automobile industry, aerospace, Die Manufacturing and instrumentation industries gained increasingly widespread application, and has made significant technical and economic benefits. contemporary advanced manufacturing technology an important component part.
HSC is to achieve high efficiency of the core technology manufacturers, intensive processes and equipment packaged so that it has a high production efficiency. It can be said that the high-speed machining is an increase in the quantity of equipment significantly improve processing efficiency essential to the technology. High-speed machining is the major advantages : improve production efficiency, improve accuracy and reduce the processing of cutting resistance.
The high-speed machining of meaning, at present there is no uniform understanding, there are generally several points as follows : high cutting speed. usually faster than that of their normal cutting 5 -10 times; machine tool spindle speed high, generally spindle speed in -20000r/min above 10,000 for high-speed cutting; Feed at high velocity, usually 15 -50m/min up to 90m/min; For different cutting materials and the wiring used the tool material, high-speed cutting the meaning is not necessarily the same; Cutting process, bladed through frequency (Tooth Passing Frequency) closer to the "machine-tool - Workpiece "system the dominant natural frequency (Dominant Natural Frequency), can be considered to be high-speed cutting. Visibility high-speed machining is a comprehensive concept.
1992. Germany, the Darmstadt University of Technology, Professor H. Schulz in the 52th on the increase of high-speed cutting for the concept and the scope, as shown in Figure 1. Think different cutting targets, shown in the figure of the transition area (Transition), to be what is commonly called the high-speed cutting, This is also the time of metal cutting process related to the technical staff are looking forward to, or is expected to achieve the cutting speed.
High-speed machining of machine tools, knives and cutting process, and other aspects specific requirements. Several were from the following aspects : high-speed machining technology development status and trends.
At this stage, in order to achieve high-speed machining, general wiring with high flexibility of high-speed CNC machine tools, machining centers, By using a dedicated high-speed milling, drilling. These equipment in common is : We must also have high-speed and high-speed spindle system feeding system, Cutting can be achieved in high-speed process. High-speed cutting with the traditional cutting the biggest difference is that "Machine-tool-workpiece" the dynamic characteristics of cutting performance is stronger influence. In the system, the machine spindle stiffness, grip or form, a long knife set, spindle Broach, torque tool set, Performance high-speed impact are important factors.
In the high-speed cutting, material removal rate (Metal Removal Rate, MRR), unit time that the material was removed volume, usually based on the "machine-tool-workpiece" whether Processing System "chatter." Therefore, in order to satisfy the high-speed machining needs, we must first improve the static and dynamic stiffness of machine spindle is particularly the stiffness characteristics. HSC reason at this stage to be successful, a very crucial factor is the dynamic characteristics of the master and processing capability.
In order to better describe the machine spindle stiffness characteristics of the project presented new dimensionless parameter - DN value, used for the evaluation of the machine tool spindle structure on the high-speed machining of adaptability. DN value of the so-called "axis diameter per minute speed with the product." The newly developed spindle machining center DN values have been great over one million. To reduce the weight bearing, but also with an array of steel products than to the much more light ceramic ball bearings; Bearing Lubrication most impressive manner mixed with oil lubrication methods. In the field of high-speed machining. have air bearings and the development of magnetic bearings and magnetic bearings and air bearings combined constitute the magnetic gas / air mixing spindle.
Feed the machine sector, high-speed machining used in the feed drive is usually larger lead, multiple high-speed ball screw and ball array of small-diameter silicon nitride (Si3N4) ceramic ball, to reduce its centrifugal and gyroscopic torque; By using hollow-cooling technology to reduce operating at high speed ball screw as temperature generated by the friction between the lead screw and thermal deformation.
In recent years, the use of linear motor-driven high-speed system of up to'''' Such feed system has removed the motor from workstations to Slide in the middle of all mechanical transmission links, Implementation of Machine Tool Feed System of zero transmission. Because no linear motor rotating components, from the role of centrifugal force, can greatly increase the feed rate. Linear Motor Another major advantage of the trip is unrestricted. The linear motor is a very time for a continuous machine shop in possession of the bed. Resurfacing of the very meeting where a very early stage movement can go, but the whole system of up to the stiffness without any influence. By using high-speed screw, or linear motor can greatly enhance machine system of up to the rapid response. The maximum a cceleration linear motors up to 2-10G (G for the acceleration of gravity), the largest feed rate of up to 60 -200m/min or higher.
2002 world-renowned Shanghai Pudong maglev train project of maglev track steel processing, Using the Shenyang Machine Tool Group Holdings Limited McNair friendship company production plants into extra-long high-speed system for large-scale processing centers achieve . The machine feeding system for the linear guide and rack gear drive, the largest table feed rate of 60 m / min, Quick trip of 100 m / min, 2 g acceleration, maximum speed spindle 20000 r / min, the main motor power 80 kW. X-axis distance of up to 30 m, 25 m cutting long maglev track steel error is less than 0.15 mm. Maglev trains for the smooth completion of the project provided a strong guarantee for technology
In addition, the campaign machine performance will also directly affect the processing efficiency and accuracy of processing. Mold and the free surface of high-speed machining, the main wiring with small cut deep into methods for processing. Machine requirements in the feed rate conditions, should have high-precision positioning functions and high-precision interpolation function, especially high-precision arc interpolation. Arc processing is to adopt legislation or thread milling cutter mold or machining parts, the essential processing methods.
Cutting Tools Tool Material development high-speed cutting and technological development of the history, tool material is continuous progress of history. The representation of high-speed cutting tool material is cubic boron nitride (CBN). Face Milling Cutter use of CBN, its cutting speed can be as high as 5000 m / min, mainly for the gray cast iron machining. Polycrystalline diamond (PCD) has been described as a tool of the 21st century tool, It is particularly applicable to the cutting aluminum alloy containing silica material, which is light weight metal materials, high strength, widely used in the automobile, motorcycle engine, electronic devices shell, the base, and so on. At present, the use of polycrystalline diamond cutter Face Milling alloy, 5000m/min the cutting speed has reached a practical level. In addition ceramic tool also applies to gray iron of high-speed machining;
Tool Coating : CBN and diamond cutter, despite good high-speed performance, but the cost is relatively high. Using the coating technology to make cutting tool is the low price, with excellent mechanical properties, which can effectively reduce the cost. Now high-speed processing of milling cutter, with most of the wiring between the Ti-A1-N composite technology for the way of multi-processing, If present in the non-ferrous metal or alloy material dry cutting, DLC (Diamond Like Carbon) coating on the cutter was of great concern. It is expected that the market outlook is very significant;
Tool clamping system : Tool clamping system to support high-speed cutting is an important technology, Currently the most widely used is a two-faced tool clamping system. Has been formally invested as a commodity market at the same clamping tool system are : HSK, KM, Bigplus. NC5, AHO systems.
In the high-speed machining, tool and fixture rotary performance of the balance not only affects the precision machining and tool life. it will also affect the life of machine tools. So, the choice of tool system, it should be a balanced selection of good products.
Process Parameters
Cutting speed of high-speed processing of conventional shear velocity of about 10 times. For every tooth cutter feed rate remained basically unchanged, to guarantee parts machining precision, surface quality and durability of the tool, Feed volume will also be a corresponding increase about 10 times, reaching 60 m / min, Some even as high as 120 m / min. Therefore, high-speed machining is usually preclude the use of high-speed, feed and depth of cut small cutting parameters. Due to the high-speed machining cutting cushion tend to be small, the formation of very thin chip light, Cutting put the heat away quickly; If the wiring using a new thermal stability better tool materials and coatings, Using the dry cutting process for high-speed machining is the ideal technology program.
High-speed machining field of application
Flexible efficient production line
To adapt to the needs of new models, auto body panel molds and resin-prevention block the forming die. must shorten the production cycle and reduce the cost of production and, therefore, we must make great efforts to promote the production of high-speed die in the process. SAIC affiliated with the company that : Compared to the past, finishing, further precision; the same time, the surface roughness must be met, the bending of precision, this should be subject to appropriate intensive manual processing. Due to the extremely high cutting speed, and the last finishing processes, the processing cycle should be greatly reduced.
To play for machining centers and boring and milling machining center category represented by the high-speed machining technology and automatic tool change function of distinctions Potential to improve processing efficiency, the processing of complex parts used to be concentrated as much as possible the wiring process, that is a fixture in achieving multiple processes centralized processing and dilute the traditional cars, milling, boring, Thread processing different cutting the limits of technology, equipment and give full play to the high-speed cutting tool function, NC is currently raising machine efficiency and speed up product development in an effective way. Therefore, the proposed multi-purpose tool of the new requirements call for a tool to complete different parts of the machining processes, ATC reduce the number of ATC to save time, to reduce the quantity and tool inventory, and management to reduce production costs. More commonly used in a multifunctional Tool, milling, boring and milling, drill ing milling, drilling-milling thread-range tool. At the same time, mass production line, against the use of technology requires the development of special tools, tool or a smart composite tool, improve processing efficiency and accuracy and reduced investment. In the high-speed cutting conditions, and some special tools can be part of the processing time to the original 1 / 10 below, results are quite remarkable.
HSC has a lot of advantages such as : a large number of materials required resection of the workpiece with ultrafine, thin structure of the workpiece, Traditionally, the need to spend very long hours for processing mobile workpiece and the design of rapid change, short product life cycle of the workpiece, able to demonstrate high-speed cutting brought advantages.
5
高速切削加工的發(fā)展及需求
高速切削加工是當(dāng)代先進(jìn)制造技術(shù)的重要組成部分,擁有高效率、高精度及高表面質(zhì)量等特征。本文介紹此技術(shù)的定義、發(fā)展現(xiàn)狀、適用領(lǐng)域以及中國的需求情況。
高速切削加工是面向21世紀(jì)的一項(xiàng)高新技術(shù),它以高效率、高精度和高表面質(zhì)量為基本特征,在汽車工業(yè)、航空航天、模具制造和儀器儀表等行業(yè)中獲得了愈來愈廣泛的應(yīng)用,并已取得了重大的技術(shù)經(jīng)濟(jì)效益,是當(dāng)代先進(jìn)制造技術(shù)的重要組成部分。
高速切削是實(shí)現(xiàn)高效率制造的核心技術(shù),工序的集約化和設(shè)備的通用化使之具有很高的生產(chǎn)效率??梢哉f,高速切削加工是一種不增加設(shè)備數(shù)量而大幅度提高加工效率所必不可少的技術(shù)。高速切削加工的優(yōu)點(diǎn)主要在于:提高生產(chǎn)效率、提高加工精度及降低切削阻力。
有關(guān)高速切削加工的含義,目前尚無統(tǒng)一的認(rèn)識,通常有如下幾種觀點(diǎn):切削速度很高,通常認(rèn)為其速度超過普通切削的5-10倍;機(jī)床主軸轉(zhuǎn)速很高,一般將主軸轉(zhuǎn)速在10000-20000r/min以上定為高速切削;進(jìn)給速度很高,通常達(dá)15-50m/min,最高可達(dá)90m/min;對于不同的切削材料和所釆用的刀具材料,高速切削的含義也不盡相同;切削過程中,刀刃的通過頻率(Tooth Passing Frequency)接近于“機(jī)床-刀具-工件”系統(tǒng)的主導(dǎo)自然頻率(Dominant Natural Frequency)時,可認(rèn)為是高速切削??梢姼咚偾邢骷庸な且粋€綜合的概念。
1992年,德國Darmstadt工業(yè)大學(xué)的H. Schulz教授在CIRP上提出了高速切削加工的概念及其涵蓋的范圍,如圖1所示。認(rèn)為對于不同的切削對象,圖中所示的過渡區(qū)(Transition)即為通常所謂的高速切削範(fàn)圍,這也是當(dāng)時金屬切削工藝相關(guān)的技術(shù)人員所期待或者可望實(shí)現(xiàn)的切削速度。
高速切削加工對機(jī)床、刀具和切削工藝等方面都有一些具體的要求。下面分別從這幾個方面闡述高速切削加工技術(shù)的發(fā)展現(xiàn)狀和趨勢。
現(xiàn)階段,為了實(shí)現(xiàn)高速切削加工,一般釆用高柔性的高速數(shù)控機(jī)床、加工中心,也有釆用專用的高速銑、鉆床。這些設(shè)備的共同之處是:必須同時具有高速主軸系統(tǒng)和高速進(jìn)給系統(tǒng),才能實(shí)現(xiàn)材料切削過程的高速化。高速切削與傳統(tǒng)切削最大的區(qū)別是,“機(jī)床-刀具-工件”系統(tǒng)的動態(tài)特性對切削性能有更強(qiáng)的影響力。在該系統(tǒng)中,機(jī)床主軸的剛度、刀柄形式、刀長設(shè)定、主軸拉刀力、刀具扭力設(shè)定等,都是影響高速切削性能的重要因素。
在高速切削中,材料去除率(Metal Removal Rate,MRR),即單位時間內(nèi)材料被切除的體積,通常受限于“機(jī)床-刀具-工件”工藝系統(tǒng)是否出現(xiàn)“顫振”。因此,為了滿足高速切削加工的需求,首先要提高機(jī)床動靜剛度尤其是主軸的剛度特性?,F(xiàn)階段高速切削之所以能夠成功,一個很關(guān)鍵的因素在于對系統(tǒng)動態(tài)特性問題的掌握和處理能力。
為了更好地描述機(jī)床主軸的剛度特性,工程上提出新的無量綱參數(shù)—DN值,用以評價機(jī)床的主軸結(jié)構(gòu)對高速切削加工的適應(yīng)性。所謂DN值即“主軸直徑與每分鐘轉(zhuǎn)速之積”。新近開發(fā)的加工中心主軸DN值大都已超過100萬。為了減輕軸承的重量,還釆用了比鋼制品要輕得多的陶瓷球軸承;軸承潤滑方式大都釆用油氣混合潤滑方式。在高速切削加工領(lǐng)域,目前已開發(fā)空氣軸承和磁軸承以及由磁軸承和空氣軸承合并構(gòu)成的磁氣/空氣混合主軸。
在機(jī)床進(jìn)給機(jī)構(gòu)方面,高速切削加工所用的進(jìn)給驅(qū)動機(jī)構(gòu)通常都為大導(dǎo)程、多頭高速滾珠絲槓,滾珠釆用小直徑氮化硅(Si3N4)陶瓷球,以減少其離心力和陀螺力矩;釆用空心強(qiáng)冷技術(shù)來減少高速滾珠絲槓運(yùn)轉(zhuǎn)時由于摩擦產(chǎn)生溫升而造成的絲槓熱變形。
近幾年來,用直線電機(jī)驅(qū)動的高速進(jìn)給系統(tǒng)問世,這種進(jìn)給方式取消了從電動機(jī)到工作臺溜板之間的一切中間機(jī)械傳動環(huán)節(jié),實(shí)現(xiàn)了機(jī)床進(jìn)給系統(tǒng)的零傳動。由于直線電機(jī)沒有任何旋轉(zhuǎn)元件,不受離心力的作用,可以大大提高進(jìn)給速度。直線電機(jī)的另一大優(yōu)點(diǎn)是行程不受限制。直線電機(jī)的次極是一段一段連續(xù)鋪在機(jī)床的床身上。次極鋪到哪里,初極工作臺就可運(yùn)動到哪里,而且對整個進(jìn)給系統(tǒng)的剛度沒有任何影響。釆用高速絲槓或直線電機(jī),能夠大大提高機(jī)床進(jìn)給系統(tǒng)的快速響應(yīng)。直線電機(jī)最高加速度可達(dá)2-10G(G為重力加速度),最大進(jìn)給速度可達(dá)60-200m/min或更高。
2002年舉世矚目的上海浦東磁懸浮列車工程中的磁浮軌道鋼梁加工,釆用沈陽機(jī)床控股有限公司集團(tuán)中捷友誼公司廠生產(chǎn)的超長進(jìn)給系統(tǒng)高速大型加工中心實(shí)現(xiàn)。該機(jī)床的進(jìn)給系統(tǒng)為直線導(dǎo)軌和齒輪齒條傳動,工作臺最大進(jìn)給速度60m/min,快速行程100m/min,加速度2g,主軸最高轉(zhuǎn)速20000r/min,主電機(jī)功率80kW。其X軸的行程長達(dá)30m,切削25m長的磁浮軌道鋼梁誤差小于0.15mm,為磁懸浮列車工程的順利竣工提供了有力的技術(shù)保證。
此外,機(jī)床的運(yùn)動性能也將直接影響加工效率和加工精度。在模具及自由曲面的高速切削加工中,主要釆用小切深大進(jìn)給的加工方法。要求機(jī)床在大進(jìn)給速度條件下,應(yīng)具有高精度定位功能和高精度插補(bǔ)功能,特別是圓弧高精度插補(bǔ)。圓弧加工是釆用立銑刀或螺紋刀具加工零部件或模具時,必不可少的加工方法。
刀具材料的發(fā)展:高速切削技術(shù)發(fā)展的歷史,也就是刀具材料不斷進(jìn)步的歷史。高速切削的代表性刀具材料是立方氮化硼(CBN)。端面銑削使用CBN刀具時,其切削速度可高達(dá)5000m/min,主要用于灰口鑄鐵的切削加工。聚晶金剛石(PCD)刀具被稱之為21世紀(jì)的刀具,它特別適用于切削含有SiO2的鋁合金材料,而這種金屬材料重量輕、強(qiáng)度高,廣泛地應(yīng)用于汽車、摩托車發(fā)動機(jī)、電子裝置的殼體、底座等方面。目前,用聚晶金剛石刀具端面銑削鋁合金時,5000m/min的切削速度已達(dá)到實(shí)用化水平,此外陶瓷刀具也適用于灰口鑄鐵的高速切削加工;
涂層刀具:CBN和金剛石刀具盡管具有很好的高速切削性能,但成本相對較高。釆用涂層技術(shù)能夠使切削刀具既價格低廉,又具有優(yōu)異性能,可有效降低加工成本?,F(xiàn)在高速加工用的立銑刀,大都釆用TiAIN系的復(fù)合多層涂鍍技術(shù)進(jìn)行處理,如目前在對鋁合金或有色金屬材料進(jìn)行干式切削時,DLC(Diamond Like Carbon)涂層刀具就受到極大的關(guān)注,預(yù)計其巿場前景十分可觀;
刀具夾持系統(tǒng):刀具的夾持系統(tǒng)是支撐高速切削的重要技術(shù),目前使用最為廣泛的是兩面夾緊式工具系統(tǒng)。已作為商品正式投放巿場的兩面夾緊式工具系統(tǒng)主要有:HSK、KM、Bigplus、NC5、AHO等系統(tǒng)。
在高速切削的情況下,刀具與夾具回轉(zhuǎn)平衡性能的優(yōu)劣,不僅影響加工精度和刀具壽命,而且也會影響機(jī)床的使用壽命。因此,在選擇工具系統(tǒng)時,應(yīng)盡量選用平衡性能良好的產(chǎn)品。
高速加工的切削速度為常規(guī)切速的10倍左右。為了使刀具每齒進(jìn)給量基本保持不變,以保證零件的加工精度、表面質(zhì)量和刀具的耐用度,則進(jìn)給量也必須相應(yīng)提高10倍左右,達(dá)到60m/min以上,有的甚至高達(dá)120m/min。因此,高速切削加工通常是釆用高轉(zhuǎn)速、大進(jìn)給和小切深的切削工藝參數(shù)。由于高速切削的切削余量往往很小,所形成的切屑很薄很輕,把切削時產(chǎn)生的熱量很快帶走;若釆用全新耐熱性更好的刀具材料和涂層,釆用干切削工藝也是高速切削加工的理想工藝方案。
用高速加工中心組成高效率的柔性生產(chǎn)線(FTL或FML),具有小型化、柔性突出以及易于變更加工內(nèi)容等顯著特點(diǎn)。圖2為上汽集團(tuán)某發(fā)動機(jī)公司利用該生產(chǎn)線加工發(fā)動機(jī)機(jī)體、汽缸蓋、濾清器座等工件的實(shí)例。
為了盡快適應(yīng)新車型的需要,汽車車身覆蓋件模具和樹脂防沖擋的成形模具等,均必須縮短制作周期和降低生產(chǎn)成本,因此,必須下大力推進(jìn)模具生產(chǎn)高速化的進(jìn)程。上汽集團(tuán)所屬各公司認(rèn)為:與過去的精加工相比,進(jìn)一步實(shí)現(xiàn)高精度化;同時必須滿足表面粗糙度、彎曲度的精度要求,為此應(yīng)施以適當(dāng)?shù)氖止ぞ藜庸ぃ捎谇邢魉俣鹊臉O大提高,與過去的精加工工序相比,加工周期應(yīng)大幅度縮短。
為了發(fā)揮以車削加工中心和鏜銑類加工中心為代表的高速切削加工技術(shù)和自動換刀功能的優(yōu)勢,提高加工效率,對復(fù)雜零件的加工應(yīng)盡可能釆用集中工序的原則,即要求在一次裝夾中實(shí)現(xiàn)多道工序的集中加工,淡化傳統(tǒng)的車、銑、鏜、螺紋加工等不同切削工藝的界限,充分發(fā)揮設(shè)備和刀具的高速切削功能,是當(dāng)前提高數(shù)控機(jī)床效率、加快產(chǎn)品開發(fā)的有效途徑。為此,對刀具提出了多功能的新要求,要求一種刀具能完成零件不同工序的加工,減少換刀次數(shù),節(jié)省換刀時間,以減少刀具的數(shù)量和庫存量,有利于管理和降低制造成本。較常用的有多功能車刀、銑刀、鏜銑刀、鉆銑刀、鉆-銑螺紋-倒角等刀具。與此同時,在批量生產(chǎn)線上,使用針對工藝需要開發(fā)的專用刀具、復(fù)合刀具或智能刀具,可以提高加工效率和精度,減少投資。在高速切削條件下,有的專用刀具可將零件的加工時間降至原來的1/10以下,效果十分顯著。
高速切削具有相當(dāng)多的好處,例如:有大量材料需要切除的工件,具有超細(xì)、薄結(jié)構(gòu)的工件,傳統(tǒng)上需要花相當(dāng)長的機(jī)動工時加工的工件以及設(shè)計變更快速、產(chǎn)品周期短的工件,均能顯示出高速切削所帶來的優(yōu)點(diǎn)。