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畢業(yè)設(shè)計(jì)(論文)
相關(guān)資料
題目:叉臂式車門(mén)玻璃升降器的設(shè)計(jì)
信機(jī) 系 機(jī)械工程及自動(dòng)化專業(yè)
學(xué) 號(hào):
學(xué)生姓名:
指導(dǎo)教師:
目 錄
一、畢業(yè)設(shè)計(jì)(論文)開(kāi)題報(bào)告
二、畢業(yè)設(shè)計(jì)(論文)外文資料翻譯及原文
三、學(xué)生“畢業(yè)論文(論文)計(jì)劃、進(jìn)度、檢查及落實(shí)表”
四、實(shí)習(xí)鑒定表
畢業(yè)設(shè)計(jì)(論文)
開(kāi)題報(bào)告
題目:叉臂式車門(mén)玻璃升降器的設(shè)計(jì)
信機(jī) 系 機(jī)械工程及自動(dòng)化 專業(yè)
學(xué) 號(hào):
學(xué)生姓名:
指導(dǎo)教師:
2
課題來(lái)源
江蘇省蘇州奧杰汽車技術(shù)有限公司
科學(xué)依據(jù)(包括課題的科學(xué)意義;國(guó)內(nèi)外研究概況、水平和發(fā)展趨勢(shì);應(yīng)用前景等)
(1)課題科學(xué)意義
正在開(kāi)發(fā)中的某車型的滑門(mén)需要一款玻璃升降器作為車門(mén)附件,用來(lái)控制滑門(mén)車窗的開(kāi)啟和關(guān)閉。本課題主要著重負(fù)責(zé)玻璃升降器的逆向設(shè)計(jì),運(yùn)用UG軟件建立玻璃升降器的三維數(shù)模,通過(guò)運(yùn)動(dòng)仿真模塊校核玻璃升降器在滑門(mén)上的布置和干涉情況,從而優(yōu)化結(jié)構(gòu),方便汽車配件廠盡快實(shí)現(xiàn)數(shù)控加工,加快汽車新產(chǎn)品上市。我國(guó)電動(dòng)玻璃升降器的發(fā)展很快,它不但在轎車中大量配套,而且開(kāi)始在輕型客車中大量配套。目前國(guó)內(nèi)外很多主機(jī)廠和汽車配件廠實(shí)現(xiàn)了基于原有設(shè)計(jì)平臺(tái)的逆向設(shè)計(jì),加快了產(chǎn)品開(kāi)發(fā)的過(guò)程,將來(lái)將會(huì)實(shí)現(xiàn)產(chǎn)品系列參數(shù)化設(shè)計(jì),只需對(duì)三維數(shù)模某些結(jié)構(gòu)尺寸修改參數(shù),就能實(shí)現(xiàn)產(chǎn)品的快速開(kāi)發(fā)。隨著汽車工業(yè)的發(fā)展,電動(dòng)玻璃升降器將呈現(xiàn)智能化、模塊化的發(fā)展趨勢(shì)。
研究?jī)?nèi)容
一.玻璃升降器設(shè)計(jì)部分:
1.適合該車型的玻璃升降器方案選擇;
2.逆向設(shè)計(jì)玻璃升降器的機(jī)械結(jié)構(gòu)。
二.玻璃升降器的運(yùn)動(dòng)仿真
三.玻璃升降器運(yùn)動(dòng)校核部分:
1.運(yùn)動(dòng)行程校核;
2. 傳動(dòng)動(dòng)力校核;
3.結(jié)構(gòu)干涉校核。
擬采取的研究方法、技術(shù)路線、實(shí)驗(yàn)方案及可行性分析
分析國(guó)內(nèi)外電動(dòng)玻璃升降器市場(chǎng)各種電動(dòng)玻璃升降器的特點(diǎn)以及適應(yīng)性、電動(dòng)玻璃升降器開(kāi)發(fā)中的問(wèn)題、各種電機(jī)性能、各部件機(jī)構(gòu)及工作原理、機(jī)械設(shè)計(jì)過(guò)程,通過(guò)對(duì)升降器各部件的性能分析,最終開(kāi)發(fā)出一款適合該車型的電動(dòng)玻璃升降器。
運(yùn)用UG軟件進(jìn)行逆向設(shè)計(jì),分析玻璃升降器總成及各部件的位置結(jié)構(gòu)和功能,建立三維數(shù)模,對(duì)總成進(jìn)行運(yùn)動(dòng)仿真,分析運(yùn)動(dòng)數(shù)據(jù),優(yōu)化結(jié)構(gòu)布置。
江蘇省蘇州奧杰汽車技術(shù)有限公司在汽車設(shè)計(jì)領(lǐng)域,運(yùn)用 當(dāng)今汽車工業(yè)最先進(jìn)的計(jì)算機(jī)輔助造型(CAS)、計(jì)算機(jī)輔助工程(CAE)、計(jì)算機(jī)輔助設(shè)計(jì)(CAD)和計(jì)算機(jī)輔助制造(CAM)軟件進(jìn)行設(shè)計(jì)開(kāi)發(fā),至今已積累了數(shù)十個(gè)車型,整車平臺(tái)及零部件開(kāi)發(fā)經(jīng)驗(yàn)。在玻璃升降器方面具備很強(qiáng)的設(shè)計(jì)開(kāi)發(fā)能力,同時(shí)國(guó)內(nèi)外市場(chǎng)對(duì)電動(dòng)玻璃升降器的需求不斷擴(kuò)大,對(duì)電動(dòng)玻璃升降器的智能化、模塊化越來(lái)越高,具備很大的市場(chǎng)可行性。
研究計(jì)劃及預(yù)期成果
研究計(jì)劃:
2012年11月12日-2012年12月25日:按照任務(wù)書(shū)要求查閱論文相關(guān)參考資料,填寫(xiě)畢業(yè)設(shè)計(jì)開(kāi)題報(bào)告書(shū)。
2013年1月11日-2013年3月5日:填寫(xiě)畢業(yè)實(shí)習(xí)報(bào)告。
2013年3月8日-2013年3月14日:按照要求修改畢業(yè)設(shè)計(jì)開(kāi)題報(bào)告。
2013年3月15日-2013年3月21日:學(xué)習(xí)并翻譯一篇與畢業(yè)設(shè)計(jì)相關(guān)的英文材料。
2013年3月22日-2013年4月11日:CAD繪圖。
2013年4月12日-2013年4月25日:UG設(shè)計(jì)。
2013年4月26日-2013年5月21日:畢業(yè)論文撰寫(xiě)和修改工作。
預(yù)期成果:
達(dá)到預(yù)期的實(shí)驗(yàn)結(jié)論:使用CAD設(shè)計(jì)繪制車門(mén)玻璃升降器裝配圖,并用UG繪制三維圖像,制作PPT文件,以及仿真。
特色或創(chuàng)新之處
玻璃升降器的整個(gè)機(jī)構(gòu)、功能、性能都可通過(guò)UG逆向設(shè)計(jì)得以實(shí)現(xiàn),實(shí)現(xiàn)了產(chǎn)品的快速設(shè)計(jì);通過(guò)運(yùn)動(dòng)仿真可以校核是否存在結(jié)構(gòu)干涉情況,降低了樣品試制的成本和風(fēng)險(xiǎn)。
交叉臂式電動(dòng)玻璃升降器 適用負(fù)載較大車門(mén)玻璃,結(jié)構(gòu)簡(jiǎn)單,制造成本低,使用壽命長(zhǎng),采用高防護(hù)電機(jī)驅(qū)動(dòng),實(shí)現(xiàn)車門(mén)玻璃的自動(dòng)升降,乘員操作方便靈活,提高了車型的整體舒適度和豪華感。
已具備的條件和尚需解決的問(wèn)題
已具備的條件:電腦;相關(guān)開(kāi)發(fā)軟件;部分技術(shù)資料。
尚需解決的問(wèn)題:學(xué)習(xí)UG軟件;確定產(chǎn)品的結(jié)構(gòu)尺寸和技術(shù)要求;逆向設(shè)計(jì)建立三維數(shù)模;總成運(yùn)動(dòng)仿真校核。
指導(dǎo)教師意見(jiàn)
指導(dǎo)教師簽名:
年 月 日
教研室(學(xué)科組、研究所)意見(jiàn)
教研室主任簽名:
年 月 日
系意見(jiàn)
主管領(lǐng)導(dǎo)簽名:
年 月 日
英文原文
Machine design theory
The machine design is through designs the new product or improves the old product to meet the human need the application technical science. It involves the project technology each domain, mainly studies the product the size, the shape and the detailed structure basic idea, but also must study the product the personnel which in aspect the and so on manufacture, sale and use question.
Carries on each kind of machine design work to be usually called designs the personnel or machine design engineer. The machine design is a creative work. Project engineer not only must have the creativity in the work, but also must in aspect and so on mechanical drawing, kinematics, engineerig material, materials mechanics and machine manufacture technology has the deep elementary knowledge.
If front sues, the machine design goal is the production can meet the human need the product. The invention, the discovery and technical knowledge itself certainly not necessarily can bring the advantage to the humanity, only has when they are applied can produce on the product the benefit. Thus, should realize to carries on before the design in a specific product, must first determine whether the people do need this kind of product
1 Lathes
Lathes are machine tools designed primarily to do turning, facing and boring, Very little turning is done on other types of machine tools, and none can do it with equal facility. Because lathes also can do drilling and reaming, their versatility permits several operations to be done with a single setup of the work piece. Consequently, more lathes of various types are used in manufacturing than any other machine tool.
The essential components of a lathe are the bed, headstock assembly, tailstock assembly, and the leads crew and feed rod.
The bed is the backbone of a lathe. It usually is made of well normalized or aged gray or nodular cast iron and provides s heavy, rigid frame on which all the other basic components are mounted. Two sets of parallel, longitudinal ways, inner and outer, are contained on the bed, usually on the upper side. Some makers use an inverted V-shape for all four ways, whereas others utilize one inverted V and one flat way in one or both sets, They are precision-machined to assure accuracy of alignment. On most modern lathes the way are surface-hardened to resist wear and abrasion, but precaution should be taken in operating a lathe to assure that the ways are not damaged. Any inaccuracy in them usually means that the accuracy of the entire lathe is destroyed.
The headstock is mounted in a foxed position on the inner ways, usually at the left end of the bed. It provides a powered means of rotating the word at various speeds . Essentially, it consists of a hollow spindle, mounted in accurate bearings, and a set of transmission gears-similar to a truck transmission—through which the spindle can be rotated at a number of speeds. Most lathes provide from 8 to 18 speeds, usually in a geometric ratio, and on modern lathes all the speeds can be obtained merely by moving from two to four levers. An increasing trend is to provide a continuously variable speed range through electrical or mechanical drives.
Because the accuracy of a lathe is greatly dependent on the spindle, it is of heavy construction and mounted in heavy bearings, usually preloaded tapered roller or ball types. The spindle has a hole extending through its length, through which long bar stock can be fed. The size of maximum size of bar stock that can be machined when the material must be fed through spindle.
The tailsticd assembly consists, essentially, of three parts. A lower casting fits on the inner ways of the bed and can slide longitudinally thereon, with a means for clamping the entire assembly in any desired location, An upper casting fits on the lower one and can be moved transversely upon it, on some type of keyed ways, to permit aligning the assembly is the tailstock quill. This is a hollow steel cylinder, usually about 51 to 76mm(2to 3 inches) in diameter, that can be moved several inches longitudinally in and out of the upper casting by means of a hand wheel and screw.
The size of a lathe is designated by two dimensions. The first is known as the swing. This is the maximum diameter of work that can be rotated on a lathe. It is approximately twice the distance between the line connecting the lathe centers and the nearest point on the ways, The second size dimension is the maximum distance between centers. The swing thus indicates the maximum work piece diameter that can be turned in the lathe, while the distance between centers indicates the maximum length of work piece that can be mounted between centers.
Engine lathes are the type most frequently used in manufacturing. They are heavy-duty machine tools with all the components described previously and have power drive for all tool movements except on the compound rest. They commonly range in size from 305 to 610 mm(12 to 24 inches)swing and from 610 to 1219 mm(24 to 48 inches) center distances, but swings up to 1270 mm(50 inches) and center distances up to 3658mm(12 feet) are not uncommon. Most have chip pans and a built-in coolant circulating system. Smaller engine lathes-with swings usually not over 330 mm (13 inches ) –also are available in bench type, designed for the bed to be mounted on a bench on a bench or cabinet.
Although engine lathes are versatile and very useful, because of the time required for changing and setting tools and for making measurements on the work piece, thy are not suitable for quantity production. Often the actual chip-production tine is less than 30% of the total cycle time. In addition, a skilled machinist is required for all the operations, and such persons are costly and often in short supply. However, much of the operator’s time is consumed by simple, repetitious adjustments and in watching chips being made. Consequently, to reduce or eliminate the amount of skilled labor that is required, turret lathes, screw machines, and other types of semiautomatic and automatic lathes have been highly developed and are widely used in manufacturing.
2 Numerical Control
One of the most fundamental concepts in the area of advanced manufacturing technologies is numerical control (NC). Prior to the advent of NC, all machine tools ere manually operated and controlled. Among the many limitations associated with manual control machine tools, perhaps none is more prominent than the limitation of operator skills. With manual control, the quality of the product is directly related to and limited to the skills of the operator. Numerical control represents the first major step away from human control of machine tools.
Numerical control means the control of machine tools and other manufacturing systems through the use of prerecorded, written symbolic instructions. Rather than operating a machine tool, an NC technician writes a program that issues operational instructions to the machine tool. For a machine tool to be numerically controlled, it must be interfaced with a device for accepting and decoding the programmed instructions, known as a reader.
Numerical control was developed to overcome the limitation of human operators, and it has done so. Numerical control machines are more accurate than manually operated machines, they can produce parts more uniformly, they are faster, and the long-run tooling costs are lower. The development of NC led to the development of several other innovations in manufacturing technology:Electrical discharge machining,Laser cutting,Electron beam welding.
Numerical control has also made machine tools more versatile than their manually operated predecessors. An NC machine tool can automatically produce a wide of parts, each involving an assortment of widely varied and complex machining processes. Numerical control has allowed manufacturers to undertake the production of products that would not have been feasible from an economic perspective using manually controlled machine tolls and processes.
Like so many advanced technologies, NC was born in the laboratories of the Massachusetts Institute of Technology. The concept of NC was developed in the early 1950s with funding provided by the U.S. Air Force. In its earliest stages, NC machines were able to made straight cuts efficiently and effectively.
However, curved paths were a problem because the machine tool had to be programmed to undertake a series of horizontal and vertical steps to produce a curve. The shorter the straight lines making up the steps, the smoother is the curve, Each line segment in the steps had to be calculated.
This problem led to the development in 1959 of the Automatically Programmed Tools (APT) language. This is a special programming language for NC that uses statements similar to English language to define the part geometry, describe the cutting tool configuration, and specify the necessary motions. The development of the APT language was a major step forward in the fur ther development from those used today. The machines had hardwired logic circuits. The instructional programs were written on punched paper, which was later to be replaced by magnetic plastic tape. A tape reader was used to interpret the instructions written on the tape for the machine. Together, all of this represented a giant step forward in the control of machine tools. However, there were a number of problems with NC at this point in its development.
A major problem was the fragility of the punched paper tape medium. It was common for the paper tape containing the programmed instructions to break or tear during a machining process. This problem was exacerbated by the fact that each successive time a part was produced on a machine tool, the paper tape carrying the programmed instructions had to be rerun through the reader. If it was necessary to produce 100 copies of a given part, it was also necessary to run the paper tape through the reader 100 separate tines. Fragile paper tapes simply could not withstand the rigors of a shop floor environment and this kind of repeated use.
This led to the development of a special magnetic plastic tape. Whereas the paper carried the programmed instructions as a series of holes punched in the tape, the plastic tape carried the instructions as a series of magnetic dots. The plastic tape was much stronger than the paper tape, which solved the problem of frequent tearing and breakage. However, it still left two other problems.
The most important of these was that it was difficult or impossible to change the instructions entered on the tape. To made even the most minor adjustments in a program of instructions, it was necessary to interrupt machining operations and make a new tape. It was also still necessary to run the tape through the reader as many times as there were parts to be produced. Fortunately, computer technology became a reality and soon solved the problems of NC associated with punched paper and plastic tape.
The development of a concept known as direct numerical control (DNC) solved the paper and plastic tape problems associated with numerical control by simply eliminating tape as the medium for carrying the programmed instructions. In direct numerical control, machine tools are tied, via a data transmission link, to a host computer. Programs for operating the machine tools are stored in the host computer and fed to the machine tool an needed via the data transmission linkage. Direct numerical control represented a major step forward over punched tape and plastic tape. However, it is subject to the same limitations as all technologies that depend on a host computer. When the host computer goes down, the machine tools also experience downtime. This problem led to the development of computer numerical control.
3 Turning
The engine lathe, one of the oldest metal removal machines, has a number of useful and highly desirable attributes. Today these lathes are used primarily in small shops where smaller quantities rather than large production runs are encountered.
The engine lathe has been replaced in today’s production shops by a wide variety of automatic lathes such as automatic of single-point tooling for maximum metal removal, and the use of form tools for finish on a par with the fastest processing equipment on the scene today.
Tolerances for the engine lathe depend primarily on the skill of the operator. The design engineer must be careful in using tolerances of an experimental part that has been produced on the engine lathe by a skilled operator. In redesigning an experimental part for production, economical tolerances should be used.
Turret Lathes Production machining equipment must be evaluated now, more than ever before, this criterion for establishing the production qualification of a specific method, the turret lathe merits a high rating.
In designing for low quantities such as 100 or 200 parts, it is most economical to use the turret lathe. In achieving the optimum tolerances possible on the turrets lathe, the designer should strive for a minimum of operations.
中文譯文
機(jī)械設(shè)計(jì)理論
機(jī)械設(shè)計(jì)是一門(mén)通過(guò)設(shè)計(jì)新產(chǎn)品或者改進(jìn)老產(chǎn)品來(lái)滿足人類需求的應(yīng)用技術(shù)科學(xué)。它涉及工程技術(shù)的各個(gè)領(lǐng)域,主要研究產(chǎn)品的尺寸、形狀和詳細(xì)結(jié)構(gòu)的基本構(gòu)思,還要研究產(chǎn)品在制造、銷售和使用等方面的問(wèn)題。
進(jìn)行各種機(jī)械設(shè)計(jì)工作的人員通常被稱為設(shè)計(jì)人員或者機(jī)械設(shè)計(jì)工程師。機(jī)械設(shè)計(jì)是一項(xiàng)創(chuàng)造性的工作。設(shè)計(jì)工程師不僅在工作上要有創(chuàng)造性,還必須在機(jī)械制圖、運(yùn)動(dòng)學(xué)、工程材料、材料力學(xué)和機(jī)械制造工藝學(xué)等方面具有深厚的基礎(chǔ)知識(shí)。
如前所訴,機(jī)械設(shè)計(jì)的目的是生產(chǎn)能夠滿足人類需求的產(chǎn)品。發(fā)明、發(fā)現(xiàn)和科技知識(shí)本身并不一定能給人類帶來(lái)好處,只有當(dāng)它們被應(yīng)用在產(chǎn)品上才能產(chǎn)生效益。因而,應(yīng)該認(rèn)識(shí)到在一個(gè)特定的產(chǎn)品進(jìn)行設(shè)計(jì)之前,必須先確定人們是否需要這種產(chǎn)品
1.車床
車床主要是為了進(jìn)行車外圓、車端面和鏜孔等項(xiàng)工作而設(shè)計(jì)的機(jī)床。車削很少在其他種類的機(jī)床上進(jìn)行,而且任何一種其他機(jī)床都不能像車床那樣方便地進(jìn)行車削加工。由于車床還可以用來(lái)鉆孔和鉸孔,車床的多功能性可以使工件在一次安裝中完成幾種加工。因此,在生產(chǎn)中使用的各種車床比任何其他種類的機(jī)床都多。
車床的基本部件有:床身、主軸箱組件、尾座組件、溜板組件、絲杠和光杠。
床身是車床的基礎(chǔ)件。它能常是由經(jīng)過(guò)充分正火或時(shí)效處理的灰鑄鐵或者球墨鐵制成。它是一個(gè)堅(jiān)固的剛性框架,所有其他基本部件都安裝在床身上。通常在床身上有內(nèi)外兩組平行的導(dǎo)軌。有些制造廠對(duì)全部四條導(dǎo)軌都采用導(dǎo)軌尖朝上的三角形導(dǎo)軌(即山形導(dǎo)軌),而有的制造廠則在一組中或者兩組中都采用一個(gè)三角形導(dǎo)軌和一個(gè)矩形導(dǎo)軌。導(dǎo)軌要經(jīng)過(guò)精密加工以保證其直線度精度。為了抵抗磨損和擦傷,大多數(shù)現(xiàn)代機(jī)床的導(dǎo)軌是經(jīng)過(guò)表面淬硬的,但是在操作時(shí)還應(yīng)該小心,以避免損傷導(dǎo)軌。導(dǎo)軌上的任何誤差,常常意味著整個(gè)機(jī)床的精度遭到破壞。
主軸箱安裝在內(nèi)側(cè)導(dǎo)軌的固定位置上,一般在床身的左端。它提供動(dòng)力,并可使工件在各種速度下回轉(zhuǎn)。它基本上由一個(gè)安裝在精密軸承中的空心主軸和一系列變速齒輪(類似于卡車變速箱)所組成。通過(guò)變速齒輪,主軸可以在許多種轉(zhuǎn)速下旋轉(zhuǎn)。大多數(shù)車床有8~12種轉(zhuǎn)速,一般按等比級(jí)數(shù)排列。而且在現(xiàn)代機(jī)床上只需扳動(dòng)2~4個(gè)手柄,就能得到全部轉(zhuǎn)速。一種正在不斷增長(zhǎng)的趨勢(shì)是通過(guò)電氣的或者機(jī)械的裝置進(jìn)行無(wú)級(jí)變速。
由于機(jī)床的精度在很大程度上取決于主軸,因此,主軸的結(jié)構(gòu)尺寸較大,通常安裝在預(yù)緊后的重型圓錐滾子軸承或球軸承中。主軸中有一個(gè)貫穿全長(zhǎng)的通孔,長(zhǎng)棒料可以通過(guò)該孔送料。主軸孔的大小是車床的一個(gè)重要尺寸,因此當(dāng)工件必須通過(guò)主軸孔供料時(shí),它確定了能夠加工的棒料毛坯的最大尺寸。
尾座組件主要由三部分組成。底板與床身的內(nèi)側(cè)導(dǎo)軌配合,并可以在導(dǎo)軌上作縱向移動(dòng)。底板上有一個(gè)可以使整個(gè)尾座組件夾緊在任意位置上的裝置。尾座體安裝在底板上,可以沿某種類型的鍵槽在底板上橫向移動(dòng),使尾座能與主軸箱中的主軸對(duì)正。尾座的第三個(gè)組成部分是尾座套筒。它是一個(gè)直徑通常大約在51~76mm(2~3英寸)之間的鋼制空心圓柱體。通過(guò)手輪和螺桿,尾座套筒可以在尾座體中縱向移入和移出幾個(gè)英寸。
車床的規(guī)格用兩個(gè)尺寸表示。第一個(gè)稱為車床的床面上最大加工直徑。這是在車床上能夠旋轉(zhuǎn)的工件的最大直徑。它大約是兩頂尖連線與導(dǎo)軌上最近點(diǎn)之間距離的兩倍。第二個(gè)規(guī)格尺寸是兩頂尖之間的最大距離。車床床面上最大加工直徑表示在車床上能夠車削的最大工件直徑,而兩頂尖之間的最大距離則表示在兩個(gè)頂尖之間能夠安裝的工件的最大長(zhǎng)度。
普通車床是生產(chǎn)中最經(jīng)常使用的車床種類。它們是具有前面所敘的所有那些部件的重載機(jī)床,并且除了小刀架之外,全部刀具的運(yùn)動(dòng)都有機(jī)動(dòng)進(jìn)給。它們的規(guī)格通常是:車床床面上最大加工直徑為305~610mm(12~24英寸);但是,床面上最大加工直徑達(dá)到1270mm(50英寸)和兩頂尖之間距離達(dá)到3658mm的車床也并不少見(jiàn)。這些車床大部分都有切屑盤(pán)和一個(gè)安裝在內(nèi)部的冷卻液循環(huán)系統(tǒng)。小型的普通車床—車床床面最大加工直徑一般不超過(guò)330mm(13英寸)--被設(shè)計(jì)成臺(tái)式車床,其床身安裝在工作臺(tái)或柜子上。
雖然普通車床有很多用途,是很有用的機(jī)床,但是更換和調(diào)整刀具以及測(cè)量工件花費(fèi)很多時(shí)間,所以它們不適合在大量生產(chǎn)中應(yīng)用。通常,它們的實(shí)際加工時(shí)間少于其總加工時(shí)間的30%。此外,需要技術(shù)熟練的工人來(lái)操作普通車床,這種工人的工資高而且很難雇到。然而,操作工人的大部分時(shí)間卻花費(fèi)在簡(jiǎn)單的重復(fù)調(diào)整和觀察切屑過(guò)程上。因此,為了減少或者完全不雇用這類熟練工人,六角車床、螺紋加工車床和其他類型的半自動(dòng)和自動(dòng)車床已經(jīng)很好地研制出來(lái),并已經(jīng)在生產(chǎn)中得到廣泛應(yīng)用。
2.數(shù)字控制
先進(jìn)制造技術(shù)中的一個(gè)基本的概念是數(shù)字控制(NC)。在數(shù)控技術(shù)出現(xiàn)之前,所有的機(jī)床都是由人工操縱和控制的。在與人工控制的機(jī)床有關(guān)的很多局限性中,操作者的技能大概是最突出的問(wèn)題。采用人工控制是,產(chǎn)品的質(zhì)量直接與操作者的技能有關(guān)。數(shù)字控制代表了從人工控制機(jī)床走出來(lái)的第一步。
數(shù)字控制意味著采用預(yù)先錄制的、存儲(chǔ)的符號(hào)指令來(lái)控制機(jī)床和其他制造系統(tǒng)。一個(gè)數(shù)控技師的工作不是去操縱機(jī)床,而是編寫(xiě)能夠發(fā)出機(jī)床操縱指令的程序。對(duì)于一臺(tái)數(shù)控機(jī)床,其上必須安有一個(gè)被稱為閱讀機(jī)的界面裝置,用來(lái)接受和解譯出編程指令。
發(fā)展數(shù)控技術(shù)是為了克服人類操作者的局限性,而且它確實(shí)完成了這項(xiàng)工作。數(shù)字控制的機(jī)器比人工操縱的機(jī)器精度更高、生產(chǎn)出零件的一致性更好、生產(chǎn)速度更快、而且長(zhǎng)期的工藝裝備成本更低。數(shù)控技術(shù)的發(fā)展導(dǎo)致了制造工藝中其他幾項(xiàng)新發(fā)明的產(chǎn)生:
電火花加工技術(shù)、激光切割、電子束焊接
數(shù)字控制還使得機(jī)床比它們采用有人工操的前輩們的用途更為廣泛。
一臺(tái)數(shù)控機(jī)床可以自動(dòng)生產(chǎn)很多類的零件,每一個(gè)零件都可以有不同的和復(fù)雜的加工過(guò)程。數(shù)控可以使生產(chǎn)廠家承擔(dān)那些對(duì)于采用人工控制的機(jī)床和工藝來(lái)說(shuō),在經(jīng)濟(jì)上是不劃算的產(chǎn)品生產(chǎn)任務(wù)。
同許多先進(jìn)技術(shù)一樣,數(shù)控誕生于麻省理工學(xué)院的實(shí)驗(yàn)室中。數(shù)控這個(gè)概念是50年代初在美國(guó)空軍的資助下提出來(lái)的。在其最初的價(jià)段,數(shù)控機(jī)床可以經(jīng)濟(jì)和有效地進(jìn)行直線切割。
然而,曲線軌跡成為機(jī)床加工的一個(gè)問(wèn)題,在編程時(shí)應(yīng)該采用一系列的水平與豎直的臺(tái)階來(lái)生成曲線。構(gòu)成臺(tái)階的每一個(gè)線段越短,曲線就越光滑。臺(tái)階中的每一個(gè)線段都必須經(jīng)過(guò)計(jì)算。
在這個(gè)問(wèn)題促使下,于1959年誕生了自動(dòng)編程工具(APT)語(yǔ)言。這是一個(gè)專門(mén)適用于數(shù)控的編程語(yǔ)言,使用類似于英語(yǔ)的語(yǔ)句來(lái)定義零件的幾何形狀,描述切削刀具的形狀和規(guī)定必要的運(yùn)動(dòng)。APT語(yǔ)言的研究和發(fā)展是在數(shù)控技術(shù)進(jìn)一步發(fā)展過(guò)程中的一大進(jìn)步。最初的數(shù)控系統(tǒng)下今天應(yīng)用的數(shù)控系統(tǒng)是有很大差別的。在那時(shí)的機(jī)床中,只有硬線邏輯電路。指令程序?qū)懺诖┛准垘希ㄋ髞?lái)被塑料帶所取代),采用帶閱讀機(jī)將寫(xiě)在紙帶或磁帶上的指令給機(jī)器翻譯出來(lái)。所有這些共同構(gòu)成了機(jī)床數(shù)字控制方面的巨大進(jìn)步。然而,在數(shù)控發(fā)展的這個(gè)階段中還存在著許多問(wèn)題。
一個(gè)主要問(wèn)題是穿孔紙帶的易損壞性。在機(jī)械加工過(guò)程中,載有編程指令信息的紙帶斷裂和被撕壞是常見(jiàn)的事情。在機(jī)床上每加工一個(gè)零件,都需要將載有編程指令的紙帶放入閱讀機(jī)中重新運(yùn)行一次。因此,這個(gè)問(wèn)題變得很嚴(yán)重。如果需要制造100個(gè)某種零件,則應(yīng)該將紙帶分別通過(guò)閱讀機(jī)100次。易損壞的紙帶顯然不能承受嚴(yán)配的車間環(huán)境和這種重復(fù)使用。
這就導(dǎo)致了一種專門(mén)的塑料磁帶的研制。在紙帶上通過(guò)采用一系列的小孔來(lái)載有編程指令,而在塑料帶上通過(guò)采用一系列的磁點(diǎn)瞇載有編程指令。塑料帶的強(qiáng)度比紙帶的強(qiáng)度要高很多,這就可以解決常見(jiàn)的撕壞和斷裂問(wèn)題。然而,它仍然存在著兩個(gè)問(wèn)題。
其中最重要的一個(gè)問(wèn)題是,對(duì)輸入到帶中指令進(jìn)行修改是非常困難的,或者是根本不可能的。即使對(duì)指令程序進(jìn)行最微小的調(diào)整,也必須中斷加工,制作一條新帶。而且?guī)ㄟ^(guò)閱讀機(jī)的次數(shù)還必須與需要加工的零件的個(gè)數(shù)相同。幸運(yùn)的是,計(jì)算機(jī)技術(shù)的實(shí)際應(yīng)用很快解決了數(shù)控技術(shù)中與穿孔紙帶和塑料帶有關(guān)的問(wèn)題。
在形成了直接數(shù)字控制(DNC)這個(gè)概念之后,可以不再采用紙帶或塑料帶作為編程指令的載體,這樣就解決了與之有關(guān)的問(wèn)題。在直接數(shù)字控制中,幾臺(tái)機(jī)床通過(guò)數(shù)據(jù)傳輸線路聯(lián)接到一臺(tái)主計(jì)算機(jī)上。操縱這些機(jī)床所需要的程序都存儲(chǔ)在這臺(tái)主計(jì)算機(jī)中。當(dāng)需要時(shí),通過(guò)數(shù)據(jù)傳輸線路提供給每臺(tái)機(jī)床。直接數(shù)字控制是在穿孔紙帶和塑料帶基礎(chǔ)上的一大進(jìn)步。然而,它敢有著同其他信賴于主計(jì)算機(jī)技術(shù)一樣的局限性。當(dāng)主計(jì)算機(jī)出現(xiàn)故障時(shí),由其控制的所有機(jī)床都將停止工作。這個(gè)問(wèn)題促使了計(jì)算機(jī)數(shù)字控制技術(shù)的產(chǎn)生。
微處理器的發(fā)展為可編程邏輯控制器和微型計(jì)算機(jī)的發(fā)展做好了準(zhǔn)備。這兩種技術(shù)為計(jì)算機(jī)數(shù)控(CNC)的發(fā)打下了基礎(chǔ)。采用CNC技術(shù)后,每臺(tái)機(jī)床上都有一個(gè)可編程邏輯控制器或者微機(jī)對(duì)其進(jìn)行數(shù)字控制。這可以使得程序被輸入和存儲(chǔ)在每臺(tái)機(jī)床內(nèi)部。它還可以在機(jī)床以外編制程序,并將其下載到每臺(tái)機(jī)床中。計(jì)算機(jī)數(shù)控解決了主計(jì)算機(jī)發(fā)生故障所帶來(lái)的問(wèn)題,但是它產(chǎn)生了另一個(gè)被稱為數(shù)據(jù)管理的問(wèn)題。同一個(gè)程序可能要分別裝入十個(gè)相互之間沒(méi)有通訊聯(lián)系的微機(jī)中。這個(gè)問(wèn)題目前正在解決之中,它是通過(guò)采用局部區(qū)域網(wǎng)絡(luò)將各個(gè)微機(jī)聯(lián)接起來(lái),以得于更好地進(jìn)行數(shù)據(jù)管理。
3.車削加工
普通車床作為最早的金屬切削機(jī)床的一種,目前仍然有許多有用的和為人要的特性和為人們所需的特性。現(xiàn)在,這些機(jī)床主要用在規(guī)模較小的工廠中,進(jìn)行小批量的生產(chǎn),而不是進(jìn)行大批量的和產(chǎn)。
在現(xiàn)代的生產(chǎn)車間中,普通車床已經(jīng)被種類繁多的自動(dòng)車床所取代,諸如自動(dòng)仿形車床,六角車床和自動(dòng)螺絲車床。現(xiàn)在,設(shè)計(jì)人員已經(jīng)熟知先利用單刃刀具去除大量的金屬余量,然后利用成型刀具獲得表面光潔度和精度這種加工方法的優(yōu)點(diǎn)。這種加工方法的生產(chǎn)速度與現(xiàn)在工廠中使用的最快的加工設(shè)備的速度相等。