直徑φ430mm的數(shù)控車床總體設(shè)計(jì)與六角回轉(zhuǎn)刀架設(shè)計(jì)
直徑430mm的數(shù)控車床總體設(shè)計(jì)與六角回轉(zhuǎn)刀架設(shè)計(jì),直徑430mm的數(shù)控車床總體設(shè)計(jì)與六角回轉(zhuǎn)刀架設(shè)計(jì),直徑,mm,妹妹,數(shù)控車床,總體,整體,設(shè)計(jì),六角,回轉(zhuǎn),刀架
畢業(yè)設(shè)計(jì)(論文)430mm的數(shù)控車床總體設(shè)計(jì)及六角回轉(zhuǎn)刀架設(shè)計(jì)所在學(xué)院專 業(yè)班 級姓 名學(xué) 號指導(dǎo)老師年 月 日摘 要現(xiàn)代數(shù)控機(jī)床是未來工廠自動(dòng)化的基礎(chǔ)。數(shù)控設(shè)計(jì)范圍大、潛力大、投資少、見效快,促進(jìn)制造業(yè)技術(shù)進(jìn)步的重要手段。因此,數(shù)控系統(tǒng)設(shè)計(jì)車床的研究具有重要意義。本文在敘述了數(shù)控技術(shù)的歷史、現(xiàn)狀和發(fā)展的基礎(chǔ)上,通過機(jī)床設(shè)計(jì)的總體思想,提出了數(shù)控化設(shè)計(jì)的技術(shù)方案和新數(shù)控系統(tǒng)的選型配置方案;提高了傳動(dòng)的精度,重新設(shè)計(jì)機(jī)床的控制邏輯,通過對伺服系統(tǒng)的分析,完成了機(jī)床各主要參數(shù)的優(yōu)化和匹配。數(shù)控車床不僅能夠車外圓還能用于鏜孔、車端面、鉆孔與鉸孔。與其他種類的機(jī)床相比,車床在生產(chǎn)中使用最廣。本論文首先介紹了我國數(shù)控機(jī)床發(fā)展的過程與現(xiàn)狀 ,并分析了其存在的問題 ;對數(shù)控機(jī)床的發(fā)展趨勢進(jìn)行了探討;并對430mm數(shù)控車床傳動(dòng)系統(tǒng)進(jìn)行了設(shè)計(jì)與計(jì)算。主軸箱有安裝在精密軸承中的空心主軸和一系列變速齒輪組成。數(shù)控車床主軸可以獲得在調(diào)速范圍內(nèi)的任意速度,以滿足加工切削要求。目前,數(shù)控車床的發(fā)展趨勢是通過電氣與機(jī)械裝置進(jìn)行無級變速。變頻電機(jī)通過帶傳動(dòng)和變速齒輪為主軸提供動(dòng)力。通常變頻電機(jī)調(diào)速范圍35,難以滿足主軸變速要求;串聯(lián)變速齒輪則擴(kuò)大了齒輪的變速范圍 。本設(shè)計(jì)將原來的帶輪不卸荷結(jié)構(gòu)變?yōu)榱藥л喰逗山Y(jié)構(gòu),使輸入軸在帶處只受轉(zhuǎn)矩,將軸上的徑向力傳動(dòng)到車床機(jī)體上,改善了輸入軸的受力情況。關(guān)鍵詞:430mm,數(shù)控車床,機(jī)床,設(shè)計(jì),數(shù)控系統(tǒng)。 IIIAbstractModern CNC machine tools is the basis for the future of factory automation. CNC design range, potential is great, less investment, quick effect, promote manufacturing industry technological progress is an important means of. Therefore, the design of NC system for lathe has important significance to the research of.This paper describes the CNC technology history, current situation and development on the basis of machine tool design, through the overall idea, put forward the technical scheme design of NC and CNC system selection scheme; the drive to improve the accuracy, to design machine tool control logic, through the servo system of a machine tool, completed the main parameters optimization and matching.NC lathe can do boring, facing, drilling and Reaming in addition to turning.The use of lathes in the production than the other types of machine tools and more. And compared to other types of machine tools, lathes in the production is the most widely used.In this design ,the development and current situation of NC machine in China was introduced and a series of problems were presented .The development trend to NC lathe was discussed.Some countermeasures was presented for the development of NC machine in China and then the headstock of 430 lathe has been calculatly designed . Headstocks is composed of the hollow spindle which is installed in precision bearings and a series of transmission gears. The spindle can obtain any speed in the speed range to meet the processing requirements of cutting.At present, the development trend is to provide a continuously variable speed through the electrical or mechanical devices . Variable Frequency Motor conveys the power through belt drive and a set of transmission gears. The speed range of Variable Frequency Motor is usually 3-5 , which is difficult to meet the speed range requirements of the spindle speed; The transmission gears is to expand the scope of a variable-speed to meet the speed range of the spindle .In addition, in this design the design of the belt drive has been changed from the original unloading structure into the loading structure, transmissed the force to the lathe body so that input shaft is only forced torque, improved the forcing state of the input shaft. Key words: 430mm, CNC lathes, machine tools, design, numerical control system.目 錄摘 要IIAbstractIII目 錄IV第1章 數(shù)控機(jī)床發(fā)展概述11.1數(shù)控機(jī)床及其特點(diǎn)11.2數(shù)控機(jī)床的工藝范圍及加工精度11.2.1工藝范圍11.2.2加工精度11.3 數(shù)控機(jī)床的經(jīng)濟(jì)分析21.4 數(shù)控機(jī)床的發(fā)展趨向3第2章 數(shù)控機(jī)床總體方案的制訂及比較42.1 總體方案設(shè)計(jì)內(nèi)容42.1.1系統(tǒng)運(yùn)動(dòng)方式的確定52.1.2控制方式的選擇52.2 總體方案確定52.2.1 系統(tǒng)的運(yùn)動(dòng)方式伺服系統(tǒng)的選擇52.2.2 數(shù)控系統(tǒng)52.2.3 機(jī)械傳動(dòng)方式6第3章 確定切削用量及選擇刀具63.1科學(xué)選擇數(shù)控刀具63.1.1選擇數(shù)控刀具的原則63.1.2選擇數(shù)控車削用刀具73.2 設(shè)置刀點(diǎn)和換刀點(diǎn)73.3 確定切削用量83.3.1確定主軸轉(zhuǎn)速83.3.2確定進(jìn)給速度83.3.3 確定背吃刀量9第4章 430mm傳動(dòng)系統(tǒng)圖的設(shè)計(jì)94.1主傳動(dòng)系統(tǒng)的設(shè)計(jì)要求94.2總體設(shè)計(jì)94.2.1 擬定傳動(dòng)方案94.2.2 選擇電機(jī)114.2.3 主運(yùn)動(dòng)調(diào)速范圍的確定、計(jì)算各軸計(jì)算轉(zhuǎn)速、功率和轉(zhuǎn)矩144.2.4 轉(zhuǎn)速圖154.3傳動(dòng)皮帶的設(shè)計(jì)和選定164.3.1 同步帶傳動(dòng)設(shè)計(jì)164.4軸系部件的結(jié)構(gòu)設(shè)計(jì)194.4.1 I軸結(jié)構(gòu)設(shè)計(jì)194.4.2 II軸結(jié)構(gòu)設(shè)計(jì)224.4.3電磁摩擦離合器的計(jì)算和選擇28第5章 數(shù)控車床的六角回轉(zhuǎn)刀架的設(shè)計(jì)原理295.1數(shù)控車床的六角回轉(zhuǎn)刀架的換刀工程295.2數(shù)控車床的六角回轉(zhuǎn)刀架的設(shè)計(jì)要求315.3數(shù)控車床的六角回轉(zhuǎn)刀架的機(jī)構(gòu)設(shè)計(jì)中的幾個(gè)主要問題315.4本章小結(jié)31第6章 數(shù)控車床的六角回轉(zhuǎn)刀架的機(jī)構(gòu)設(shè)計(jì)326.1數(shù)控車床的六角回轉(zhuǎn)刀架的分度機(jī)構(gòu)結(jié)構(gòu)設(shè)計(jì)326.1.1分度機(jī)構(gòu)結(jié)構(gòu)設(shè)計(jì)的總思路326.1.2分度機(jī)構(gòu)的刀架主軸設(shè)計(jì)326.1.3主活塞的設(shè)計(jì)346.1.4端齒盤離合器的設(shè)計(jì)386.1.5分度活塞的設(shè)計(jì)456.2精定位機(jī)構(gòu)活動(dòng)插銷機(jī)構(gòu)設(shè)計(jì)466.2.1定位原理、設(shè)計(jì)思路466.2.2材料選擇476.2.3活動(dòng)插銷機(jī)構(gòu)的結(jié)構(gòu)設(shè)計(jì)476.2.4插銷機(jī)構(gòu)的公差帶設(shè)計(jì)486.2.5對插銷軸進(jìn)行校核496.2.6校核結(jié)論506.3 刀夾襯套的設(shè)計(jì)簡述51第7章 微機(jī)數(shù)控系統(tǒng)的設(shè)計(jì)527.1 微機(jī)數(shù)控系統(tǒng)的設(shè)計(jì)綱要527.1.1 硬件電路設(shè)計(jì)527.1.2 軟件電路設(shè)計(jì)537.2 8031單片機(jī)及其擴(kuò)展537.2.1 8031單片機(jī)的簡介537.2.2 8031單片機(jī)的系統(tǒng)擴(kuò)展547.2.3 存儲(chǔ)器擴(kuò)展567.2.4 I/O口的擴(kuò)展587.2.5 步進(jìn)電機(jī)驅(qū)動(dòng)電路597.2.6 脈沖分配器(環(huán)行分配器)607.2.7 光電隔離電路607.2.8 功率放大器607.2.9 其他輔助電路61結(jié) 論63致 謝64參考文獻(xiàn)6567第1章 數(shù)控機(jī)床發(fā)展概述1.1數(shù)控機(jī)床及其特點(diǎn)隨著數(shù)控技術(shù)的發(fā)展,采用數(shù)控系統(tǒng)的機(jī)床品種日益增多,有車床、車床、鏜床、鉆床、磨床、齒輪加工機(jī)床和電火花加工機(jī)床等。此外還有能自動(dòng)換刀、一次裝卡進(jìn)行多工序加工的加工中心、車削中心等。數(shù)控機(jī)床主要由數(shù)控裝置、伺服機(jī)構(gòu)和機(jī)床主體組成。輸入數(shù)控裝置的程序指令記錄在信息載體上,由程序讀入裝置接收,或由數(shù)控裝置的鍵盤直接手動(dòng)輸入。1.2數(shù)控機(jī)床的工藝范圍及加工精度1.2.1工藝范圍數(shù)控車床是一種高精度、高效率的自動(dòng)化機(jī)床,也是使用數(shù)量最多的數(shù)控機(jī)床,約占數(shù)控機(jī)床總數(shù)的25%。它主要用于精度要求高、表面粗糙度好、輪廓形狀復(fù)雜的軸類、盤類等回轉(zhuǎn)體零件的加工,能夠通過程序控制自動(dòng)完成園柱面、圓錐面、圓弧面和各種螺紋的切削加工,并能進(jìn)行切槽、鉆孔、擴(kuò)孔、鉸孔等加工。1.2.2加工精度由于數(shù)控車床具有加工精度高、能作直線和圓弧插補(bǔ)功能,有些數(shù)控車床還具有非圓曲線插補(bǔ)功能以及加工過程中具有自動(dòng)變速功能等特點(diǎn),所以它的工藝范圍要比普通車床要寬得多。1.精度要求高的回轉(zhuǎn)體零件由于數(shù)控車床剛性好,制造和對刀精度高,以及能方便和精確地進(jìn)行人工補(bǔ)償和自動(dòng)補(bǔ)償,所以能加工精度要求高的零件,甚至可以以車代磨。2.表面粗糙度要求高的回轉(zhuǎn)體零件數(shù)控車床具有恒線速切削功能,能加工出表面粗糙度小的均勻的零件。使用恒線速切削功能,就可選用最佳速度來切削錐面和端面,使切削后的工件表面粗糙度既小又一致。數(shù)控車床還適合加工各表面粗糙度要求不同的工件。粗糙度要求大的部位選用較大的進(jìn)給量,要求小的部位選用小的進(jìn)給量。3.輪廓形狀特別復(fù)雜和難于控制尺寸的回轉(zhuǎn)體零件由于數(shù)控車床具有直線和圓弧插補(bǔ)功能,部分車床數(shù)控裝置還有某些非圓曲線和平面曲線插補(bǔ)功能,所以可以加工形狀特別復(fù)雜或難于控制尺寸的的回轉(zhuǎn)體零件。4.帶特殊螺紋的回轉(zhuǎn)體零件普通車床所能車削的螺紋類型相當(dāng)有限,它只能車等導(dǎo)程的直、錐面公、英制螺紋,而且一臺車床只能限定加工若干導(dǎo)程的螺紋。而數(shù)控車床不但能車削任何等導(dǎo)程的直、錐面螺紋和端面螺紋,而且能車變螺距螺紋,還可以車高精度螺紋。1.3 數(shù)控機(jī)床的經(jīng)濟(jì)分析近幾年,隨著國民經(jīng)濟(jì)快速穩(wěn)定發(fā)展,我國機(jī)床制造行業(yè)受益于國家振興裝備制造業(yè)的大環(huán)境,有了長足進(jìn)展,這其中領(lǐng)先當(dāng)今機(jī)械制造技術(shù)水平的數(shù)控機(jī)床產(chǎn)業(yè)更勝一籌。 由于數(shù)控設(shè)備的先進(jìn)性、復(fù)雜性和發(fā)展的迅速性,以及品種型號、檔次的多樣性,決定了選用數(shù)控設(shè)備的復(fù)雜性和難度。如何從品種繁多、價(jià)格昂貴的產(chǎn)品中選擇適用的設(shè)備, 成為中小型企業(yè)十分關(guān)心的問題。數(shù)控車床是一種高精度、高效率的自動(dòng)化機(jī)床,也是使用數(shù)量最多的數(shù)控機(jī)床,約占數(shù)控機(jī)床總數(shù)的25%。它主要用于精度要求高、表面粗糙度好、輪廓形狀復(fù)雜的軸類、盤類等零件的加工,能夠通過程序控制自動(dòng)完成園柱面、圓錐面、圓弧面和各種螺紋的切削加工,并能進(jìn)行切槽、鉆孔、擴(kuò)孔、鉸孔等加工。由于數(shù)控車床具有加工精度高、能作直線和圓弧插補(bǔ)功能,有些數(shù)控車床還具有非圓曲線插補(bǔ)功能以及加工過程中具有自動(dòng)變速功能等特點(diǎn),所以它的工藝范圍要比普通車床要寬得多。1、精度要求高的零件由于數(shù)控機(jī)床剛性好,制造和對刀精度高,以及能方便和精確地進(jìn)行人工補(bǔ)償和自動(dòng)補(bǔ)償,所以能加工精度要求高的零件,甚至可以以銑代磨。2、表面粗糙度要求高的零件數(shù)控車床具有恒線速切削功能,能加工出表面粗糙度小的均勻的零件。使用恒線速切削功能,就可選用最佳速度來切削錐面和端面,使切削后的工件表面粗糙度既小又一致。數(shù)控車床還適合加工各表面粗糙度要求不同的工件。粗糙度要求大的部位選用較大的進(jìn)給量,要求小的部位選用小的進(jìn)給量。3、輪廓形狀特別復(fù)雜和難于控制尺寸的零件由于數(shù)控車床具有直線和圓弧插補(bǔ)功能,部分車床數(shù)控裝置還有某些非圓曲線和平面曲線插補(bǔ)功能,所以可以加工形狀特別復(fù)雜或難于控制尺寸的的零件。4、帶特殊螺紋的零件普通車床所能車削的螺紋類型相當(dāng)有限,它只能車等導(dǎo)程的直、錐面公、英制螺紋,而且一臺車床只能限定加工若干導(dǎo)程的螺紋。而數(shù)控車床不但能車削任何等導(dǎo)程的直、錐面螺紋和端面螺紋,而且能車變螺距螺紋,還可以車高精度螺紋。 1.4 數(shù)控機(jī)床的發(fā)展趨向數(shù)控機(jī)床是由美國發(fā)明家約翰帕森斯上個(gè)世紀(jì)發(fā)明的。隨著電子信息技術(shù)的發(fā)展,世界機(jī)床業(yè)已進(jìn)入了以數(shù)字化制造技術(shù)為核心的機(jī)電一體化時(shí)代,其中數(shù)控機(jī)床就是代表產(chǎn)品之一。數(shù)控機(jī)床是制造業(yè) 的加工母機(jī)和國民經(jīng)濟(jì)的重要基礎(chǔ)。它為國民經(jīng)濟(jì)各個(gè)部門提供裝備和手段,具有無限放大的經(jīng)濟(jì)與社會(huì)效應(yīng)。技術(shù)發(fā)展趨勢:高速、精密、復(fù)合、智能和綠色是數(shù)控機(jī)床技術(shù)發(fā)展的總趨勢,近幾年來,在實(shí)用化和產(chǎn)業(yè)化等方面取得可喜成績。主要表現(xiàn)在: 1.機(jī)床復(fù)合技術(shù)進(jìn)一步擴(kuò)展隨著數(shù)控機(jī)床技術(shù)進(jìn)步,復(fù)合加工技術(shù)日趨成熟,包括車-車復(fù)合、車車復(fù)合、車-鏜-鉆-齒輪加工等復(fù)合,車磨復(fù)合,成形復(fù)合加工、特種復(fù)合加工等,復(fù)合加工的精度和效率大大提高?!耙慌_機(jī)床就是一個(gè)加工廠”、“一次裝卡,完全加工”等理念正在被更多人接受,復(fù)合加工機(jī)床發(fā)展正呈現(xiàn)多樣化的態(tài)勢。 2數(shù)控機(jī)床的智能化技術(shù)有新的突破,在數(shù)控系統(tǒng)的性能上得到了較多體現(xiàn)。如:自動(dòng)調(diào)整干涉防 碰撞功能、斷電后工件自動(dòng)退出安全區(qū)斷電保護(hù)功能、加工零件檢測和自動(dòng)補(bǔ)償學(xué)習(xí)功能、高精度加工零件智能化參數(shù)選用功能、加工過程自動(dòng)消除機(jī)床震動(dòng)等功能 進(jìn)入了實(shí)用化階段,智能化提升了機(jī)床的功能和品質(zhì)。 3機(jī)器人使柔性化組合效率更高機(jī)器人與主機(jī)的柔性化組合得到廣泛應(yīng)用,使得柔性線更加靈活、 功能進(jìn)一步擴(kuò)展、柔性線進(jìn)一步縮短、效率更高。機(jī)器人與加工中心、車車復(fù)合機(jī)床、磨床、齒輪加工機(jī)床、工具磨床、電加工機(jī)床、鋸床、沖壓機(jī)床、激光加工機(jī) 床、水切割機(jī)床等組成多種形式的柔性單元和柔性生產(chǎn)線已經(jīng)開始應(yīng)用。 4精密加工技術(shù)有了新進(jìn)展數(shù)控金切機(jī)床的加工精度已從原來的絲級(0.01mm)提升到目前 的微米級(0.001mm),有些品種已達(dá)到0.05m左右。超精密數(shù)控機(jī)床的微細(xì)切削和磨削加工,精度可穩(wěn)定達(dá)到0.05m左右,形狀精度可達(dá) 0.01m左右。采用光、電、化學(xué)等能源的特種加工精度可達(dá)到納米級(0.001m)。通過機(jī)床結(jié)構(gòu)設(shè)計(jì)優(yōu)化、機(jī)床零部件的超精加工和精密裝配、采用 高精度的全閉環(huán)控制及溫度、振動(dòng)等動(dòng)態(tài)誤差補(bǔ)償技術(shù),提高機(jī)床加工的幾何精度,降低形位誤差、表面粗糙度等,從而進(jìn)入亞微米、納米級超精加工時(shí)代。 5功能部件性能不斷提高功能部件不斷向高速度、高精度、大功率和智能化方向發(fā)展,并取得成熟的應(yīng)用。全數(shù)字交流伺服電機(jī)和驅(qū)動(dòng)裝置,高技術(shù)含量的電主軸、力矩電機(jī)、直線電機(jī),高性能的直線滾動(dòng)組件,高精度主軸單元等功能部件推廣應(yīng)用,極大的提高數(shù)控機(jī)床的技術(shù)水平。第2章 數(shù)控機(jī)床總體方案的制訂及比較 2.1 總體方案設(shè)計(jì)內(nèi)容數(shù)控機(jī)床可以較好的解決形狀復(fù)雜、精密多品種及中小批零件的加工問題,能夠穩(wěn)定加工質(zhì)量和提高生產(chǎn)率,隨著制造技術(shù)向自動(dòng)化、柔性化方向的發(fā)展,當(dāng)前機(jī)床的數(shù)控化率已經(jīng)成為衡量一個(gè)國家制造工業(yè)水平的重要標(biāo)志。機(jī)床的數(shù)控化設(shè)計(jì)一般是指對現(xiàn)有某臺普通車床的某些部位做一定的改裝,配上經(jīng)濟(jì)型數(shù)控裝置或標(biāo)準(zhǔn)型數(shù)控?cái)?shù)控系統(tǒng),從而使原機(jī)床具有數(shù)控加工能力。這種技術(shù)工作有其獨(dú)特的特點(diǎn)。機(jī)床的數(shù)控設(shè)計(jì),主要是對原有機(jī)床的結(jié)構(gòu)進(jìn)行創(chuàng)造性的設(shè)計(jì),最終使機(jī)床達(dá)到比較理想的狀態(tài)。數(shù)控車床是機(jī)電一體化的典型代表,其機(jī)械結(jié)構(gòu)同普通的機(jī)床有相似之處。然而,現(xiàn)代的數(shù)控機(jī)床不是簡單將傳統(tǒng)機(jī)床配備上數(shù)控系統(tǒng)即可,也不是在傳統(tǒng)機(jī)床的基礎(chǔ)上,僅對局部加以改進(jìn)而成。傳統(tǒng)機(jī)床存在著一些弱點(diǎn),如剛性不足,抗震性差,熱變形大,滑動(dòng)面的摩擦阻力大及傳動(dòng)元件之間存在間隙等,難以勝任數(shù)控機(jī)床對加工精度,表面質(zhì)量,生產(chǎn)率以及使用壽命等要求?,F(xiàn)代機(jī)床的部件結(jié)構(gòu),整體布局,外部造型都已經(jīng)形成了數(shù)控機(jī)床獨(dú)特的機(jī)械部件。因此,我們在對數(shù)控機(jī)床進(jìn)行數(shù)控設(shè)計(jì)的過程中,應(yīng)在考慮各種情況下,使普通機(jī)床的各項(xiàng)性能指標(biāo)盡可能的 與數(shù)控機(jī)床相接近。機(jī)床的設(shè)計(jì)主要應(yīng)具備兩個(gè)條件1.機(jī)床基礎(chǔ)件必須有足夠的剛度2.改裝的費(fèi)用要合適,經(jīng)濟(jì)性好。改裝前要對機(jī)床的性能指標(biāo)做出決定,改裝后其各項(xiàng)指標(biāo)能達(dá)到數(shù)控加工的要求。機(jī)械部分?jǐn)?shù)控化設(shè)計(jì)需涉及電機(jī)的選擇、工作臺進(jìn)給結(jié)構(gòu)、傳動(dòng)比分配與計(jì)算等方面的內(nèi)容。1伺服驅(qū)動(dòng)元件進(jìn)給電機(jī)選用混合式步進(jìn)電機(jī),其不僅步距角小運(yùn)行頻率高且功耗低低頻噪音小等優(yōu)點(diǎn)。廣泛用于開環(huán)控制系統(tǒng),不需要反饋裝置,結(jié)構(gòu)簡單可靠,壽命長。橫垂直進(jìn)給電機(jī)均選用同一型號以便于設(shè)計(jì)和日后維修。脈沖當(dāng)量t=0.01mm/脈沖,選用步距角=0.6 。對原機(jī)床的主傳動(dòng)系統(tǒng)均維持不變,以節(jié)約資金及縮短改裝時(shí)間。接到一個(gè)數(shù)控裝置的設(shè)計(jì)任務(wù)以后,必須首先擬定總體方案,繪制系統(tǒng)總體框圖,才能決定各種設(shè)計(jì)參數(shù)和結(jié)構(gòu),然后再分別對機(jī)械部分和電氣部分進(jìn)行設(shè)計(jì)。機(jī)床數(shù)控系統(tǒng)總體方案的擬定包括以下內(nèi)容:系統(tǒng)運(yùn)動(dòng)方式的確定、伺服系統(tǒng)的選擇、執(zhí)行機(jī)構(gòu)的結(jié)構(gòu)及傳動(dòng)方式的確定,計(jì)算機(jī)系統(tǒng)的選擇等內(nèi)容。一般應(yīng)根據(jù)設(shè)計(jì)任務(wù)和要求提出數(shù)個(gè)總體方案,進(jìn)行綜合分析、比較和論證,最后確定一個(gè)可行的總體方案。2.1.1系統(tǒng)運(yùn)動(dòng)方式的確定數(shù)控系統(tǒng)按運(yùn)動(dòng)方式可分為點(diǎn)位控制系統(tǒng)、點(diǎn)位直線控制系統(tǒng)和連續(xù)控制系統(tǒng)。2.1.2控制方式的選擇系統(tǒng)可分為開環(huán)控制系統(tǒng)、半閉環(huán)控制系統(tǒng)和閉環(huán)控制系統(tǒng)。經(jīng)濟(jì)型數(shù)控機(jī)床普遍采用開環(huán)伺服系統(tǒng)。開環(huán)控制系統(tǒng)中,沒有檢測反饋裝置,數(shù)控裝置發(fā)出的信號的流程是單向的,也正是由于信號的單向流程,它對機(jī)床移動(dòng)部件的實(shí)際位置不做檢測,所以機(jī)床加工精度要求不太高,其精度主要取決于伺服系統(tǒng)的性能。開環(huán)伺服系統(tǒng)主要由步進(jìn)電機(jī)驅(qū)動(dòng)。這類機(jī)床工作比較穩(wěn)定,反應(yīng)迅速,調(diào)試和維修都比較簡單。2.2 總體方案確定2.2.1 系統(tǒng)的運(yùn)動(dòng)方式伺服系統(tǒng)的選擇由于改造后的經(jīng)濟(jì)型數(shù)控機(jī)床應(yīng)具備定位,直線插補(bǔ),順、逆圓弧插補(bǔ),暫停,循環(huán)加工,公英制螺紋加工等功能,故應(yīng)選擇連續(xù)控制系統(tǒng)??紤]達(dá)到屬于經(jīng)濟(jì)型數(shù)控機(jī)床加工精度要求不高,為了簡化結(jié)構(gòu)、降低成本,采用步進(jìn)電機(jī)開環(huán)控制系統(tǒng)。2.2.2 數(shù)控系統(tǒng)根據(jù)機(jī)床要求,采用8位微機(jī)。由于MCS-51系列單片機(jī)具有集成度高,可靠性好,功能強(qiáng),速度快,抗干擾性強(qiáng),具有很高的性能價(jià)格比等特點(diǎn),決定采用MCS-51系列的8031單片機(jī)擴(kuò)展系統(tǒng)??刂葡到y(tǒng)由微機(jī)部分、鍵盤及顯示器、I/O接口及光電隔離電路、步進(jìn)電機(jī)功率放大電路等組成,系統(tǒng)的加工程序和控制命令通過鍵盤操作實(shí)現(xiàn),顯示器采用數(shù)碼管顯示加工數(shù)據(jù)及機(jī)床狀態(tài)等信息。2.2.3 機(jī)械傳動(dòng)方式為實(shí)現(xiàn)機(jī)床所要求的分辨率,采用步進(jìn)電機(jī)經(jīng)齒輪減速再傳動(dòng)絲桿,為保證一定的傳動(dòng)精度和平穩(wěn)性,盡量減少摩擦力,選用滾珠絲桿螺母副。同時(shí),為提高傳動(dòng)剛度和消除間隙,采用預(yù)加負(fù)荷的結(jié)構(gòu)。齒輪傳動(dòng)也要采用消除齒輪間隙的結(jié)構(gòu)。系統(tǒng)總體方案框圖如下: 圖2-1 系統(tǒng)總體方案框圖第3章 確定切削用量及選擇刀具3.1科學(xué)選擇數(shù)控刀具3.1.1選擇數(shù)控刀具的原則 選擇刀具壽命時(shí)可考慮如下幾點(diǎn)根據(jù)刀具復(fù)雜程度、制造和磨刀成本來選擇。復(fù)雜和精度高的刀具壽命應(yīng)選得比單刃刀具高些。對于機(jī)夾可轉(zhuǎn)位刀具,由于換刀時(shí) 間短,為了充分發(fā)揮其切削性能,提高生產(chǎn)效率,刀具壽命可選得低些,一般取15-30min。對于裝刀、換刀和調(diào)刀比較復(fù)雜的多刀機(jī)床、組合機(jī)床與自動(dòng)化 加工刀具,刀具壽命應(yīng)選得高些,尤應(yīng)保證刀具可靠性。車間內(nèi)某一工序的生產(chǎn)率限制了整個(gè)車間的生產(chǎn)率的提高時(shí),該工序的刀具壽命要選得低些當(dāng)某工序單位時(shí) 間內(nèi)所分擔(dān)到的全廠開支M較大時(shí),刀具壽命也應(yīng)選得低些。大件精加工時(shí),為保證至少完成一次走刀,避免切削時(shí)中途換刀,刀具壽命應(yīng)按零件精度和表面粗糙度 來確定。與普通機(jī)床加工方法相比,數(shù)控加工對刀具提出了更高的要求,不僅需要岡牲好、精度高,而且要求尺寸穩(wěn)定,耐用度高,斷和排性能壇同時(shí)要求安裝調(diào)整 方便,這樣來滿足數(shù)控機(jī)床高效率的要求。數(shù)控機(jī)床上所選用的刀具常采用適應(yīng)高速切削的刀具材料(如高速鋼、超細(xì)粒度硬質(zhì)合金)并使用可轉(zhuǎn)位刀片。刀具壽命與切削用量有密切關(guān)系。在制定切削用量時(shí),應(yīng)首先選擇合理的刀具壽命,而合理的刀具壽命則應(yīng)根據(jù)優(yōu)化的目標(biāo)而定。一般分最高生產(chǎn)率刀具壽命和最低成本刀具壽命兩種,前者根據(jù)單件工時(shí)最少的目標(biāo)確定,后者根據(jù)工序成本最低的目標(biāo)確定。3.1.2選擇數(shù)控車削用刀具在數(shù)控加工中,車削平面零件內(nèi)外輪廓 及車削平面常用平底立車刀,該刀具有關(guān)參數(shù)的經(jīng)驗(yàn)數(shù)據(jù)如下:一是車刀半徑RD應(yīng)小于零件內(nèi)輪廓面的最小曲率半徑Rmin,一般取RD=(0.8一 0.9)Rmin。二是零件的加工高度HRdp,電動(dòng)機(jī)直接驅(qū)動(dòng)主軸不能滿足恒功率變速要求,因此需要串聯(lián)一個(gè)有級變速箱,以滿足主軸的恒功率調(diào)速范圍。取,則對于數(shù)控車床,為了加工端面時(shí)滿足恒線速度切削的要求,應(yīng)使轉(zhuǎn)速有一些重復(fù),故取Z=2故前面?zhèn)鲃?dòng)比分配可取。各軸計(jì)算轉(zhuǎn)速 各軸輸入功率 各軸輸入轉(zhuǎn)矩 將以上計(jì)算結(jié)果整理后列于表2.2,供以后計(jì)算選擇,供以后計(jì)算使用:表2.3 各軸的傳動(dòng)參數(shù)參數(shù) 軸0軸(電機(jī)軸)I軸(傳動(dòng)軸)II軸(中間傳動(dòng)軸)III軸(主軸)計(jì)算轉(zhuǎn)()1000416.7208 104/416.7輸入功率(Kw) 5.5 5.285.124.79轉(zhuǎn)矩() 54121235 456.4/114傳動(dòng)比 ,4.2.4 轉(zhuǎn)速圖由電機(jī)的轉(zhuǎn)速范圍(包括恒功率變速范圍)和各軸傳動(dòng)比,作數(shù)控車床的轉(zhuǎn)速圖, 見圖4-2. 圖4.2 轉(zhuǎn)速圖4.3傳動(dòng)皮帶的設(shè)計(jì)和選定 (如無特殊說明,本小節(jié)公式均出自資料14)帶傳動(dòng)是由帶和帶輪組成傳遞運(yùn)動(dòng)和動(dòng)力的傳動(dòng)。根據(jù)工作原理可分為兩類:摩擦帶傳動(dòng)和嚙合帶傳動(dòng)。摩擦帶傳動(dòng)是機(jī)床主要傳動(dòng)方式之一,常見的有平帶傳動(dòng)和同步帶傳動(dòng);嚙合傳動(dòng)只有同步帶一種。普通同步帶傳動(dòng)是常見的帶傳動(dòng)形式,其結(jié)構(gòu)為:承載層為繩芯或膠簾布,楔角為40、相對高度進(jìn)似為0.7、梯形截面環(huán)行帶。其特點(diǎn)為:當(dāng)量摩擦系數(shù)大,工作面與輪槽粘附著好,允許包角小、傳動(dòng)比大、預(yù)緊力小。繩芯結(jié)構(gòu)帶體較柔軟,曲撓疲勞性好。其應(yīng)用于:帶速V2530m/s;傳動(dòng)功率P700kW;傳動(dòng)比i10軸間距小的傳動(dòng)。一主要失效形式 1帶在帶輪上打滑,不能傳遞動(dòng)力; 2帶由于疲勞產(chǎn)生脫層、撕裂和拉斷; 3帶的工作面磨損。 保證帶在工作中不打滑的前提下能傳遞最大功率,并具有一定的疲勞強(qiáng)度和使用壽命是同步帶傳動(dòng)設(shè)計(jì)的主要依據(jù),也是靠摩擦傳動(dòng)的其它帶傳動(dòng)設(shè)計(jì)的主要依據(jù)。4.3.1 同步帶傳動(dòng)設(shè)計(jì) (1)設(shè)計(jì)功率的確定:由表8-7查得工況系數(shù)(2) 選定帶型:根據(jù)和由圖8-10確定選用A型。確定帶輪的基準(zhǔn)直徑并驗(yàn)算帶速傳V:1初選帶輪的基準(zhǔn)直徑由表8-6和表8-8確定:取小帶輪直徑=125mm2驗(yàn)算帶速V:因?yàn)?m/sV計(jì)算大帶輪的基準(zhǔn)直徑。=i=2.4125=300mm根據(jù)表8-8圓整為=315mm確定同步帶的中心距a和基準(zhǔn)長度Ld 1初定帶輪距得: 即: 初取 2計(jì)算帶所需的基準(zhǔn)長度:由表8-2選帶的基準(zhǔn)長度Ld=1800mm3計(jì)算實(shí)際中心距:安裝時(shí)所需最小軸間距:張緊或補(bǔ)償伸長所需最大軸間距:(5)驗(yàn)算小帶輪包角:所以小帶輪包角合適。(6)計(jì)算帶的根數(shù)Z。1單根同步帶的基本額定功率:根據(jù)dd1和=1000r/min查表8-4a得基本額定功率=1.428Kw。再根據(jù)=1000r/min、i=2.4和A型帶查表8-4b得=0.12Kw查表8-5得:2計(jì)算帶的根數(shù)z。取 根。計(jì)算單根同步帶的初拉力的最小值:應(yīng)使帶的實(shí)際初拉力計(jì)算壓軸力壓軸力的最小值為:(9)帶輪的結(jié)構(gòu)和尺寸:由表8-10可查得為了減輕傳動(dòng)軸上載荷,采用卸荷式帶輪結(jié)構(gòu),使帶輪上的載荷由軸承支撐進(jìn)而傳給箱體,軸只承受轉(zhuǎn)矩,裝配裝置參見裝配圖。4.4軸系部件的結(jié)構(gòu)設(shè)計(jì)4.4.1 I軸結(jié)構(gòu)設(shè)計(jì)(如無特殊說明,本小節(jié)公式均出自資料14)I軸上的零件主要是齒輪1。一端用凸臺定位,另一端用緊定螺釘定位。1.選定齒輪類型,精度等級,材料及齒數(shù).根據(jù)選定的傳動(dòng)方案,選用直齒圓柱齒輪傳動(dòng).(1)本次設(shè)計(jì)屬于金屬切削機(jī)床類,一般齒輪傳動(dòng),故選用6級精度.(2)材料選擇.由表10-1選擇小齒輪材料為40Cr(調(diào)質(zhì)),硬度為280HBS,大齒輪材料為45鋼(調(diào)質(zhì))硬度為240HBS,二者材料硬度差為40HBS.(3)選小齒輪齒數(shù)大齒輪齒數(shù) 2.按齒面接觸強(qiáng)度設(shè)計(jì) 由設(shè)計(jì)計(jì)算公式(10-9a)進(jìn)行試算,即: (2.5)確定公式內(nèi)的各計(jì)算數(shù)值(1)試選載荷系數(shù)(2)計(jì)算小齒輪傳遞的轉(zhuǎn)矩由上文可知為121N/m(3)由表10-7選取齒寬系數(shù)(4)由表10-6查得材料的彈性影響系數(shù)(5)由圖10-21d按齒面硬度查得小齒輪的接觸疲勞強(qiáng)度極限大齒輪的接觸疲勞強(qiáng)度極限;(6)由式10-13計(jì)算應(yīng)力循環(huán)次: (2.6)(7)由圖10-19查得接觸疲勞壽命系數(shù)(8)計(jì)算接觸疲勞許用應(yīng)力取失效概率為1%,安全系數(shù)S=1,由式(10-12)得: (2.7)2)計(jì)算(1)小齒輪分度圓直徑,代入中較小的值:(2.8) (2)計(jì)算圓周速度: (2.9)(3)計(jì)算齒寬: (2.10)(4)計(jì)算齒寬與齒高之比: 模數(shù) (2.11) 齒高 (2.12) (2.13)(5)計(jì)算載荷系數(shù)根據(jù),6級精度,由圖10-8查得動(dòng)載系數(shù);直齒輪,假設(shè)。由表10-3查得;由表10-2查得使用系數(shù);由表10-4查得6級精度,小齒輪懸臂支承時(shí): (2.14) 將數(shù)據(jù)代入得: ; (2.15)由,查圖10-13得;故載荷系數(shù): (2.16) (6)按實(shí)際的載荷系數(shù)校正所得的分度圓直徑,由式(10-10a)得: (2.17)(7)計(jì)算模數(shù): (2.18)3.按齒根彎曲強(qiáng)度設(shè)計(jì):由式(10-5)得彎曲強(qiáng)度的設(shè)計(jì)公式為: (2.19)1)確定公式內(nèi)的各計(jì)算數(shù)值(1)由圖10-20c查得小齒輪的彎曲疲勞強(qiáng)度極限;大齒輪的彎曲疲勞強(qiáng)度極限;(2)由圖10-18查得彎曲疲勞壽命系數(shù),;(3)計(jì)算彎曲疲勞許用應(yīng)力取彎曲疲勞安全系數(shù)S=1.4,由式(10-12)得: (2.20) (4)計(jì)算載荷系數(shù)K: (2.21) (5)查取齒形系數(shù)由表10-5查得;。(6)查取應(yīng)力校正系數(shù)由表10-5查得;。(7)計(jì)算大小齒輪的并加以比較: (2.22)大齒輪的數(shù)值大。2)設(shè)計(jì)計(jì)算:對比計(jì)算結(jié)果,由齒面接觸疲勞強(qiáng)度計(jì)算的模數(shù)大于由齒根彎曲疲勞強(qiáng)度計(jì)算的模數(shù),由于齒輪模數(shù)的大小主要取決于彎曲強(qiáng)度所決定的承載能力,而齒面接觸疲勞強(qiáng)度所決定的承載能力,僅與齒輪直徑(即模數(shù)與齒數(shù)的乘積)有關(guān),可取由彎曲疲勞強(qiáng)度算得的模數(shù)2.31并就近圓整為標(biāo)準(zhǔn)值m=2.5,按接觸強(qiáng)度算得的分度圓直徑,算出小齒輪齒數(shù):大齒輪齒數(shù)這樣設(shè)計(jì)出的齒輪傳動(dòng),即滿足了齒面接觸疲勞強(qiáng)度,又滿足了齒根彎曲疲勞強(qiáng)度,并做到結(jié)構(gòu)緊湊,避免浪費(fèi)。4.幾何尺寸計(jì)算1)計(jì)算分度圓直徑:2)計(jì)算中心距:3)計(jì)算齒輪寬度:取。5.驗(yàn)算:,合適。4.4.2 II軸結(jié)構(gòu)設(shè)計(jì)(如無特殊說明,本小節(jié)公式均出自資料14)1.軸的支承形式該軸不受或只受極小的軸向力,而右端所受徑向力矩明顯高于左端,故左端選用深溝球軸承,而右端選用一對角接觸球軸承背靠背安裝,如圖所示:圖4.4 中間軸的支承形式2.軸上零件的軸向定位II軸上的主要零件主要有三對直齒圓柱齒輪及其中兩直齒圓柱齒輪對應(yīng)的電磁離合器。滾子軸承的左端靠在端蓋上,右端用軸肩定位。與電機(jī)軸上齒輪相嚙合的齒輪左端用圓螺母固定,右端用軸肩定位.另外兩齒輪所對應(yīng)的電磁離合器位于它們中間,相互緊靠,兩齒輪的另兩端用螺釘鎖緊擋圈定位。軸右端的軸承左邊利用軸肩定位,右端用一摔油盤(有套筒的作用)和圓螺母進(jìn)行定位。(1)軸的選材和最小直徑得確定軸的材料選擇為:45號鋼(調(diào)質(zhì)處理)。軸的最小尺寸,由式(152), 式中,由表153,可取得110,故: 取35mm。由于取值較計(jì)算值大的多,所以不用再按彎扭合成強(qiáng)度條件計(jì)算和進(jìn)行疲勞強(qiáng)度校合。軸的零件圖如圖2-5.圖4.5 中間軸零件圖(2)齒輪的設(shè)計(jì)齒輪1和2的直徑相差較大,對齒輪1(小齒輪)在模數(shù)和選材及熱處理方面要求較高,所以首先進(jìn)行該對齒輪的設(shè)計(jì)。1.選定齒輪的精度等級和材料,初選齒數(shù)本數(shù)控機(jī)床的運(yùn)行速度較高,精度等級選擇6級精度;由表101,小齒輪材料選擇為40,調(diào)質(zhì)后表面淬火,硬度為280HBS;大齒輪材料選擇為45鋼,調(diào)制后表面淬火,硬度為240HBS。小齒輪的齒數(shù)初選為24, 242=482.按齒面接觸強(qiáng)度進(jìn)行設(shè)計(jì)按式(109)試算: 確定公式內(nèi)的各計(jì)算值:初選載荷系數(shù)Kt1.6;計(jì)算小齒輪傳遞的轉(zhuǎn)矩由前文可知小齒輪傳遞的轉(zhuǎn)矩為235;由表107及其說明,可選定齒寬系數(shù); 由表106,查得材料的彈性影響系數(shù)189.8;由圖1021d,按齒面接觸硬度查得小齒輪的接觸疲勞強(qiáng)度650MPa;大齒輪的接附錄譯文:The open system merit of Computer Numerical Control and Numerical control of production equipmentsAbstractThe open system merit is the system simple, the cost low, but the shortcoming is the precision is low. The reverse gap, the guide screw pitch error, stop inferiorly can affect the pointing accuracy by mistake. Following several kind of improvements measure may cause the pointing accuracy distinct improvement.The key word:numerical control 、NC 、the open systerm 1)reverse gap error compensates The numerical control engine bed processing cutting tool and the work piece relative motion is depends upon the drive impetus gear,the guide screw rotation, thus the impetus work floor and so on moves the part to produce moves realizes. As traditional part gear, guide screw although the manufacture precision is very high, but always unavoidably has the gap. As a result of this kind of gap existence, when movement direction change, starts the section time to be able tocause inevitably actuates the part wasting time, appears the instruction pulse to push the motionless functional element the aspect. This has affected the engine bed processing precision, namely the instruction pulse and actual enters for the step does not tally,has the processing error therefore, the split-ring numerical control system all establishes generally has the reverse gap errorcompensatory function, with by makes up which wastes time the step reverse gap difference compensates is first actual reverse enters for the error, converts the pulse equivalent number it, compensates the subroutine as the gap the output, when the computer judgment appearswhen instruction for counter motion, transfers the gap to compensate the subroutine immediately, compensates the pulse after the output to eliminate the reverse gap to carry on again normally inserts makes up the movement. 2)often the value systematic characteristic position error compensatesA kind of storehouse by transfers for the designer. Like this in the components design stage, the designer only must input the characteristic the parameter, the system direct productioncharacteristic example model: We must save the related characteristic class in the database the structure information, the database table collection are use in saving this part of related information. According to the characteristic type definition need, we defined the characteristic class code table, the characteristic class edition information have outstanding shown the characteristic type; Defined the characteristic class structure outstanding to reach the characteristic class the structure; And relates through the components characteristic disposition table and the components characteristic level information. The characteristic level data sheet collection isthis components model database design core, has recorded characteristic example information and so on model design, craft. The characteristic structure table has recorded the characteristicgeometry structure; The characteristic size table, the characteristic shape position table of limits, the characteristic surface roughness table has recorded the characteristic project semantics quotation; The size table, the shape position table of limits, the surface roughnesstable saved all components characteristic data message. In the characteristic level, using characteristic ID, geometry principal linkage and so on essential factor ID, size ID, common difference ID, roughness ID carries on the data retrieval. We apply this components information model database under the factory environment some module CAD in the AM integrative system, has realized CAD and the CAPP characteristic information sharing well. Main use ready-made CAD/the CAM software (Unigra phics 1I) carries on the product design and the NC programming in this system, and through carries on two times of developments gains components to this software the size information; At the same time uses the dialogue window which develops voluntarily, lets design the personnel to input other characteristic information alternately, realizes this software and the system sharing database connection. When assistance technological design, the technological design personnel through the procedure inquiry function, inquires the components information from the sharing database which needs, carries on the interactive technological design. Thus has facilitated the CAPP components information acquisition, enhanced the technological design efficiency. When carries on the NC programming using UG, may from the sharing database gain the craft and the manufacture information which needs, carries on various working procedures the knife axle design and the processing simulation establishes an absolute zero spot on the numerical control engine bed, the actual various coordinate axes syzygy completely position error, makes the curve in order to determined compensates the spot. Attempts l to show is an actual position error curve, (error) carries on this curve y-coordinate take the pulse equivalent as the unit the division, makes the horizontal line, each horizontal line and the curve point of intersection namely compensates the spot for the goal. Chart 1 the center 1 to 6 oclock place position errors for, needs to do reduces the pulse to compensate; But needs to carry on 6 to 9 adds the pulse to compensate in the chart the shadow partially for to compensate the area. Compensates the range of points these to become the error The calibration corrections stores the computer, when work table by zero displacement in position, installs sends out the absolute zero point localization signal in the absolute zero point micros witch, later computer as necessary will send out the goal to compensate to compensate the signal, will carry on the position error to the engine bed to compensate. The cosine generator assigns slide guage initiation signal a electricity and by step of transmission.3) feedbacks compensates the open-loop control Chart 2 has produced this kind of system schematic diagram. This system surveys two parts by the open-loop control and the induction synchromesh direct position to be composed. Here position examination does not serve as the position the feedback, but is compensates the feedback as the position error. Its cardinal principle is: Installs the instruction pulse by the engine bed numerical control which CNC sends out, on the one hand the supplies open system, thecontrol step-by-steps the electrical machinery according to the instruction revolution, and the direct drive platen moves, constitutes the open-loop control; On the other hand this instruction pulse supplies the induction synchromesh the measurement system (namely digitally, cosine generator), as position demand signal a by. The work in the warning way induction synchromesh this time not only is the position sensor, also is the comparator, it by, The cosine generator assigns slide guage initiation signal a electricity and by step of transmission.4) conclusions Under the CIMS environment the technology which develops unceasingly based on characteristic components information modeling, how enhances the components order of complexity which the characteristic design can complete; How causes question and so on request which the characteristic design adoption trick recognition, the characteristic semantics transforms also to wait for the people to solve. This article introduced the characteristic technology in the components information modeling application, describes this components data model database realization with emphasis; Establishes the components information database system may satisfy the CIMS system well to the letter. Numerical control (NC) is a form of programmable automation in which the processing equipment is controlled by means of numbers, letters, and other symbols. The numbers, letters, and symbols are coded in an appropriate format to define a program of instructions for a particular workpart or job. When the job changes, the program of instructions is changed. The capability to change the program is what makes NC suitable for low-and medium-volume production. It is much easier to write new programs than to make major alterations of the processing equipment.Basic components of NC A numerical control system consists of the following three basic components:Program of instructionsMachine control unitProcessing equipmentThe general relationship among the three components is illustrated in Fig.2.1. The program is fed into the control unit, which directs the processing equipment accordingly.The program of instructions is the detailed step-by-step commands that direct the processing equipment. In its most common form, the commands refer to positions of a machine tool spindle with respect to the worktable on which the part is fixtured. More advanced instructions include selection of spindle speeds, cutting tool, and other function. The most common medium in use over the last several decades has been 1-in. -wide punched tape. Because of the widespread use of the punched tape, NC is sometimes called “tape control”. However, this is a misnomer in modern usage of numerical control. Coming into use more recently have been magnetic tape cassettes and floppy diskettes.The machine control unit (MCU) consists of the electronics and control hardware that read and interpret the program of instruction and convert it into mechanical actions of the machine tool or other processing equipment.The processing equipment is the third basic component of an NC system. It is the component that performs useful work. In the most common example of numerical control, one that performs machining operations, the processing equipment consists of the worktable and spindle as well as the motors and controls needed to drive them.TYPES OF CONTROL SYSTEMSThere are two basic types of control systems in numerical control: point-to-point and contouring. In the point-to-point system, also called positioning, each axis of the machine is driven separately by leadscrews and, depending on the type of operation, at different velocities. The machine moves initially at maximum velocity in order to reduce nonproductive time but decelerates as the tool reaches its numerically defined position. Thus in an potation such as drilling or punching, the positioning and cutting take place sequentially. After the hole is drilled or punched, the tool retracts, moves rapidly to another position, and repeats the operation. The path followed from one position to another is important in only one respect: The time required should be minimized for efficiency. Point-to-point systems are used mainly in drilling, punching, and straight milling operations.In the contouring system, also known as the continuous path system, positioning and cutting operations are both along controlled paths but at different velocities. Because the tool cuts as it travels along a prescribed path, accurate control and synchronization of velocities and movements are important. The contouring system is used on lathes, milling machines, grinders, welding machinery, and machining centers.Movement along the path, or interpolation, occurs incrementally, by one of several basic methods. In all interpolations, the path controlled is that of the center of rotation of the tool. Compensation for different tools, different diameter tools, or tool wear during machining, can be made in the NC program.There are a number of interpolation schemes that have been developed to deal with the various problems that are encountered in generating a smooth continuous path with a contouring-type NC system. They include:Linear interpolationCircular interpolationHelical interpolationParabolic interpolationCubic interpolationEach of these interpolation procedures permits the programmer (or operator) to generate machine instructions for linear or curvilinear paths, using a relatively few input parameters. The interpolation module in the MCU performs the calculations and directs the tool along the path.Linear interpolation is the most basic and is used when a straight-line path is to be generated in continuous-path NC. Two-axis and three-axis linear interpolation routines are sometimes distinguished in practice, but conceptually they are the same. The program is required to specify the beginning point and end point of the straight line, and the feed rate that is to be followed along the straight line. The interpolator computes the feed rates for each of the two (or three) axes in order to achieve the specified feed rate.Linear interpolation for creating a circular path would be quite inappropriate because the programmer would be required to specify the line segments and their respective end points that are to be used to approximate the circle. Circular interpolation schemes have been developed that permit the programming of a path consisting of a circular arc by specifying the following parameters of the arc: the coordinates of its end points, the coordinates of its center, its radius, and the direction of the cutter along the arc. The tool path that is created consists of a series of straight-line segments, but the segments are calculated by the interpolation module rather than the programmer. The cutter is directed to move along each line segment one by one in order to generate the smooth circular path. A limitation of circular interpolation is that the plane in which the circular arc exists must be a plane defined by two axes of the NC system.Helical interpolation combines the circular interpolation scheme for two axes described above with linear movement of a third axis. This permits the definition of a helical path in three-dimensional space.Parabolic and cubic interpolation routines are used to provide approximations of free-form curves using higher-order equations. They generally require considerable computational power and are not as common as linear and circular interpolation. Their applications are concentrated in the automobile industry for fabricating dies for car body panels styled with free-form designs that cannot accurately and conveniently be approximated by combining linear and circular interpolations.PROGRAMMING FOR NCA program for numerical control consists of a sequence of directions that causes an NC machine to carry out a certain operation, machining being the most commonly used process. Programming for NC may be done by an internal programming department, on the shop floor, or purchased from an outside source. Also, programming may be done manually or with computer assistance.The program contains instructions and commands. Geometric instructions pertain to relative movements between the tool and the workpiece. Processing instructions pertain to spindle speeds, feeds, tools, and so on. Travel instructions pertain to the type of interpolation and slow or rapid movements of the tool or worktable. Switching commands pertain to on/off position for coolant supplies, spindle rotation, direction of spindle rotation, tool changes, workpiece feeding, clamping, and so on. Manual Programming Manual part programming consists of first calculating dimensional relationships of the tool, workpiece, and work table, based on the engineering drawings of the part, and manufacturing operations to be performed and their sequence. A program sheet is then prepared, which consists of the necessary information to carry out the operation, such as cutting tools, spindle speeds, feeds, depth of cut, cutting fluids, power, and tool or workpiece ally a paper tape is first prepared for trying out and debugging the program. Depending on how often it is to be used, the tape may be made of more durable Mylar.Manual programming can be done by someone knowledgeable about the particular process and able to understand, read, and change part programs. Because they are familiar with machine tools and process capabilities, skilled machinists can do manual programming with some training in programming. However, the work is tedious, time consuming, and uneconomical-and is used mostly in simple point-to-point applications. Computer-Aided Programming Computer-aided part programming involves special symbolic programming languages that determine the coordinate points of corners, edges, and surfaces of the part. Programming language is the means of communicating with the computer and involves the use of symbolic characters. The programmer describes the component to be processed in this language, and the computer converts it to commands for the NC machine. Several languages having various features and applications are commercially available. The first language that used English-like statements was developed in the late 1950s and is called APT (for Automatically Programmed Tools). This language, in its various expanded forms, is still the most widely used for both point-to-point and continuous-path programming.Computer-aided part programming has the following significant advantages over manual methods: Use of relatively easy to use symbolic languageReduced programming time. Programming is capable of accommodating a large amount of data concerning machine characteristics and process variables, such as power, speeds, feed, tool shape, compensation for tool shape changes, tool wear, deflections, and coolant use. Reduced possibility of human error, which can occur in manual programming Capability of simple changeover of machining sequence or from machine to machine. Lower cost because less time is required for programming.Selection of a particular NC programming language depends on the following factors: Level of expertise of the personnel in the manufacturing facility. Complexity of the part. Type of equipment and computers available. Time and costs involved in programming.Because numerical control involves the insertion of data concerning workpiece materials and processing parameters, programming must be done by operators or programmers who are knowledgeable about the relevant aspects of the manufacturing processes being used. Before production begins, programs should be verified, either by viewing a simulation of the process on a CRT screen or by making the part from an inexpensive material, such as aluminum, wood, or plastic, rather than the material specified for the finished part.Reference:1 Zhang Huashu under. parallel environment based on characteristic components definition model J. mechanical science with technology, 1,999, 18 (1): 14l 144.2 forest morning star, Du full text, Xu Jianxin. characteristic and (,M)/CAPP/CAM integrative system J. the computer-aided design and makes, 1998, 28 (5): 5155.3 Zeng Hui E, Zhou Qingzhong. studied J based on the characteristic mechanical product modelling . the machinery to suppose Counts with the manufacture the regulation, 1,999, 28 (2): 12 l4.譯文:數(shù)控機(jī)床開環(huán)控制伺服系統(tǒng)與數(shù)控生產(chǎn)設(shè)備摘要開環(huán)系統(tǒng)的優(yōu)點(diǎn)是系統(tǒng)簡單、成本低,但缺點(diǎn)是精度低。反向間隙、絲杠螺距誤差、起停誤差等都會(huì)影響定位精度。下面幾種改進(jìn)措施可以使定位精度明顯改善。關(guān)鍵字:數(shù)控系統(tǒng)、開環(huán)系統(tǒng)1) 反向間隙誤差補(bǔ)償數(shù)控機(jī)床加工刀具與工件的相對運(yùn)動(dòng)是依靠驅(qū)動(dòng)裝置帶動(dòng)齒輪、絲杠轉(zhuǎn)動(dòng),從而推動(dòng)工作臺面等移動(dòng)部件產(chǎn)生位移來實(shí)現(xiàn)的。作為傳統(tǒng)元件的齒輪、絲杠盡管制造精度很高,但總免不了存在間隙。由于這種間隙存在,當(dāng)運(yùn)動(dòng)的方向改變時(shí),開始段時(shí)間必然會(huì)引起驅(qū)動(dòng)元件的空走,出現(xiàn)指令脈沖推不動(dòng)執(zhí)行元件的局面。這就影響了機(jī)床的加工精度,即指令脈沖與實(shí)際進(jìn)給步數(shù)不相符合,產(chǎn)生加工誤差 因此,開環(huán)數(shù)控系統(tǒng)一般都設(shè)置有反向間隙誤差補(bǔ)償功能,用以補(bǔ)足空走的步數(shù)反向間隙差補(bǔ)償就是首先實(shí)測反向進(jìn)給的誤差,把它折算成脈沖當(dāng)量數(shù),作為間隙補(bǔ)償子程序的輸出量,當(dāng)計(jì)算機(jī)判斷出現(xiàn)的指令為反向運(yùn)動(dòng)時(shí),隨即調(diào)用間隙補(bǔ)償子程序,通過輸出補(bǔ)償脈沖消除反向間隙后再進(jìn)行正常的插補(bǔ)運(yùn)行。2) 常值系統(tǒng)性定位誤差補(bǔ)償類庫以供設(shè)計(jì)者調(diào)用。這樣在零件的設(shè)計(jì)階段,設(shè)計(jì)者只需輸入特征的參數(shù),系統(tǒng)直接生成特征的實(shí)例模型:在數(shù)據(jù)庫中我們必須存儲(chǔ)相關(guān)的特征類的結(jié)構(gòu)信息,數(shù)據(jù)庫表集就是用于存儲(chǔ)這一部分的相關(guān)信息。根據(jù)特征類型定義的需要,我們定義了特征類編碼表、特征類版本信息表表示特征類型;定義了特征類構(gòu)造表表達(dá)特征類的結(jié)構(gòu);并通過零件特征配置表與零件的特征層信息聯(lián)系起來。特征層數(shù)據(jù)表集是本零件模型數(shù)據(jù)庫設(shè)計(jì)的核心,記錄了特征實(shí)例模型的設(shè)計(jì)、工藝等信息。特征構(gòu)造表記錄了特征的幾何結(jié)構(gòu);特征尺寸表、特征形位公差表、特征表面粗糙度表記錄了特征的工程語義引用;尺寸表、形位公差表、表面粗糙度表存儲(chǔ)了所有零件特征的數(shù)據(jù)信息。在特征層,利用特征ID、幾何要素ID、尺寸ID、公差I(lǐng)D、粗糙度ID等主鍵進(jìn)行數(shù)據(jù)檢索。我們將該零件信息模型的數(shù)據(jù)庫應(yīng)用于工廠環(huán)境下某型組件的CAD AM 集成系統(tǒng)中,較好地實(shí)現(xiàn)了CAD與CAPP的特征信息共享。在該系統(tǒng)中主要使用現(xiàn)成的CADCAM 軟件(Unigraphics 1I)進(jìn)
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