K356-錐齒輪座加工工藝及鉆3-M6螺紋孔夾具設計【版本2】
K356-錐齒輪座加工工藝及鉆3-M6螺紋孔夾具設計【版本2】,k356,齒輪,加工,工藝,m6,螺紋,羅紋,夾具,設計,版本
目 錄前 言11 工藝規(guī)程制定21.1機械加工工藝規(guī)程制訂21.2機械加工工藝規(guī)程的組成21.3制訂機械加工工藝規(guī)程的原始資料22 零件的分析32.1零件的作用32.2零件的工藝分析33 工藝規(guī)程設計43.1基準面的選擇43.1.1 粗基準的選擇原則43.1.2 精基準的選擇原則43.2 制定工藝路線53.3 確定各工序的加工余量、計算工序尺寸及公差63.4 基本工時的確立84 鉆夾具設計194.1定位基準的選擇194.2定位元件的設計194.3切削力及夾緊力計算194.5夾緊力的確定204.5鉆套設計214.6夾具設計及操作簡要說明23結(jié) 論24前 言 機械制造業(yè)是制造具有一定形狀位置和尺寸的零件和產(chǎn)品,并把它們裝備成機械裝備的行業(yè)。機械制造業(yè)的產(chǎn)品既可以直接供人們使用,也可以為其它行業(yè)的生產(chǎn)提供裝備,社會上有著各種各樣的機械或機械制造業(yè)的產(chǎn)品。我們的生活離不開制造業(yè),因此制造業(yè)是國民經(jīng)濟發(fā)展的重要行業(yè),是一個國家或地區(qū)發(fā)展的重要基礎及有力支柱。從某中意義上講,機械制造水平的高低是衡量一個國家國民經(jīng)濟綜合實力和科學技術(shù)水平的重要指標。錐齒輪座的加工工藝規(guī)程及其鉆、攻4-M8螺紋孔的夾具是在學完了機械制圖、機械制造技術(shù)基礎、機械設計、機械工程材料等進行畢業(yè)設計之后的下一個教學環(huán)節(jié)。正確地解決一個零件在加工中的定位,夾緊以及工藝路線安排,工藝尺寸確定等問題,并設計出專用夾具,保證零件的加工質(zhì)量。本次設計也要培養(yǎng)自己的自學與創(chuàng)新能力。因此本次設計綜合性和實踐性強、涉及知識面廣。所以在設計中既要注意基本概念、基本理論,又要注意生產(chǎn)實踐的需要,只有將各種理論與生產(chǎn)實踐相結(jié)合,才能很好的完成本次設計。本設計選用錐齒輪座來進行工藝編制與夾具設計,以說明書、繪圖為主,設計手冊與國家標準為附來進行詳細說明。1 工藝規(guī)程制定1.1機械加工工藝規(guī)程制訂1、工藝規(guī)程 規(guī)定產(chǎn)品或零部件制造工藝過程和操作方法等的工藝文件。2、制訂工藝規(guī)程的原則 保證圖樣上規(guī)定的各項技術(shù)要求,有較高的生產(chǎn)效率,技術(shù)先進,經(jīng)濟效益高,勞動條件良好。3、制訂工藝規(guī)程的原始資料 4、制訂工藝規(guī)程的程序 計算生產(chǎn)綱領,確定生產(chǎn)類型;分析產(chǎn)品裝配圖,對零件圖樣進行工藝審查;確定毛坯的種類、形狀、尺寸及精度;擬訂工藝路線(劃分工藝過程的組成、選擇定位基準、選擇零件表面的加工方法、安排加工順序、選擇機床設備等);進行工序設計(確定各工序加工余量、工序尺寸及公差,選擇工藝裝備,計算時間定額等;確定工序的技術(shù)要求及檢驗方法,填寫工藝文件。1.2機械加工工藝規(guī)程的組成工藝過程由若干個按著一定順序排列的工序組成。工序是工藝過程的基本單元,也是生產(chǎn)組織和計劃的基本單元。工序又可細分為若干個安裝、工位及工步等。1、 工序 一個或一組人,在一個工作地對同一個或同時對幾個工件所連續(xù)完成的一部分工藝過程。2、 安裝 工件經(jīng)一次裝夾后所完成的那一部分工序3、 工位 為了完成一定的工序部分,一次裝夾工件后,工件與夾具或設備的可動部分相對刀具或設備的固定部分占據(jù)每一位置所完成的那部分工序。4、 工步 在加工表面和加工工具不變的情況下所連續(xù)完成的那一部分工序5、 走刀 在一個工步內(nèi)當被加工表面的切削余量較大,需分幾次切削時,則每進行一次切削稱為一次走刀。1.3制訂機械加工工藝規(guī)程的原始資料產(chǎn)品裝配圖及零件圖;產(chǎn)品質(zhì)量的驗收標準;產(chǎn)品的生產(chǎn)綱領及生產(chǎn)類型;原材料及毛坯的生產(chǎn)水平;現(xiàn)場生產(chǎn)條件(機床設備與工藝裝備、工人技術(shù)水平等);國內(nèi)外有關(guān)工藝、技術(shù)發(fā)展狀況。2 零件的分析2.1零件的作用 錐齒輪座是一個典型的交叉孔零件,主要應用在混凝土拖泵中導向輪部件上,其上要安裝兩個配對錐齒輪座,因此主要的工作表面為90mm和52mm的兩個孔。 2.2零件的工藝分析對該零件的平面、孔和螺紋進行加工,具體要求如下:155下端面 粗糙度Ra6.373孔 粗糙度Ra6.390孔 粗糙度Ra1.6155上端面 粗糙度Ra3.2100端面 粗糙度Ra6.3100外圓 粗糙度Ra1.680沉孔 粗糙度Ra6.382端面 粗糙度Ra6.352孔 粗糙度Ra1.64-M8螺紋 粗糙度Ra12.5M3螺紋 粗糙度Ra12.53-M6螺紋 粗糙度Ra12.54-M5螺紋 粗糙度Ra12.52-8錐孔 粗糙度Ra6.3 3 工藝規(guī)程設計3.1基準面的選擇基面的選擇是工藝規(guī)程設計中的重要工作之一?;孢x擇的正確、合理,可以保證質(zhì)量,提高生產(chǎn)效率。否則,就會使加工工藝過程問題百出,嚴重的還會造成零件大批報廢,使生產(chǎn)無法進行。3.1.1 粗基準的選擇原則1)如果必須首先保證工件上加工表面與不加工表面 之間的位置要求,應以不加工表面作為粗基準。如果在工件上有很多不需加工的表面,則應以其中與加工面位置精度要求較高的表面作粗基準。2)如果必須首先保證工件某重要表面的加工余量均勻,應選擇該表面作精基準。3)如需保證各加工表面都有足夠的加工余量,應選加工余量較小的表面作粗基準。4)選作粗基準的表面應平整,沒有澆口、冒口、飛邊等缺陷,以便定位可靠。5)粗基準一般只能使用一次,特別是主要定位基準,以免產(chǎn)生較大的位置誤差。3.1.2 精基準的選擇原則選擇精基準時要考慮的主要問題是如何保證設計技術(shù)要求的實現(xiàn)以及裝夾準確、可靠、方便。精基準選擇應當滿足以下要求:1)用設計基準作為定位基準,實現(xiàn)“基準重合”,以免產(chǎn)生基準不重合誤差。2)當工件以某一組精基準定位可以較方便地加工很多表面時,應盡可能采用此組精基準定位,實現(xiàn)“基準統(tǒng)一”,以免生產(chǎn)基準轉(zhuǎn)換誤差。3)當精加工或光整加工工序要求加工余量盡量小而均勻時,應選擇加工表面本身作為精基準,即遵循“自為基準”原則。該加工表面與其他表面間的位置精度要求由先行工序保證。4)為獲得均勻的加工余量或較高 的位置精度,可遵循“互為基準”、反復加工的原則。5)有多種方案可供選擇時應選擇定位準確、穩(wěn)定、夾緊可靠,可使夾具結(jié)構(gòu)簡單的表面作為精基準。 3.2 制定工藝路線制定工藝路線的出發(fā)點,應當是使零件的幾何形狀、尺寸精度及位置精度等技術(shù)要求能得到合理的保證。在生產(chǎn)綱領以確定為大批生產(chǎn)的條件下,可采用通用機床配以專用工夾具,并盡量使工序集中來提高生產(chǎn)效率。除此以外,還應考慮經(jīng)濟效果,以便降低生產(chǎn)成本。最終工藝方案如下:工序01:金屬型澆注工序02:時效處理以消除內(nèi)應力工序03:以155外圓作為定位基準,粗車155下端面、73孔、90孔、半精車90孔工序04:以90孔作為定位基準,粗車155上端面、100端面、100外圓、80沉孔 、半精車155上端面、100外圓、精車100外圓、潔角工序05:以155外圓作為定位基準,精車90孔、車槽工序06:以90孔作為定位基準,粗車82端面、52孔、半精車、精車52孔工序07:以90孔作為定位基準,鉆4-M8螺紋底孔6.8深21、攻4-M8深18螺紋工序08:以90孔作為定位基準,鉆M3螺紋底孔2.55深8、攻M3深6螺紋工序09:以90孔作為定位基準,鉆3-M6螺紋底孔5.1深15、攻M6深12螺紋工序10:以73孔作為定位基準,鉆4-M5螺紋底孔4.25深15、攻M5深12螺紋工序11:以90孔作為定位基準,配作2-8錐孔工序12:鉗工去毛刺工序13:檢驗至圖紙要求工序14:包裝、入庫3.3 確定各工序的加工余量、計算工序尺寸及公差 1. 155下端面的加工余量查機械制造工藝設計簡明手冊表2.2-4,得鑄件的單邊加工余量Z=2.5mm,鑄件尺寸公差為CT8級,表面粗糙度Ra為6.3。根據(jù)機械制造工藝設計簡明手冊表1.4-8,一步車削(即粗車、半精車)方可滿足其精度要求。2. 73孔的加工余量查機械制造工藝設計簡明手冊表2.2-4,得鑄件的單邊加工余量Z=1.5mm,鑄件尺寸公差為CT8級,表面粗糙度Ra為6.3。根據(jù)機械制造工藝設計簡明手冊表1.4-8,一步車削(即粗車、半精車)方可滿足其精度要求。3. 90孔 的加工余量查機械制造工藝設計簡明手冊表2.2-4,得鑄件的單邊加工余量Z=8.5mm,鑄件尺寸公差為CT8級,表面粗糙度Ra為1.6。根據(jù)機械制造工藝設計簡明手冊表1.4-8,三步車削(即粗車、半精車、精車)方可滿足其精度要求。粗車 單邊余量Z=8.0mm半精車 單邊余量Z=0.4mm精車 單邊余量Z=0.1mm4. 155上端面的加工余量查機械制造工藝設計簡明手冊表2.2-4,得鑄件的單邊加工余量Z=2.5mm,鑄件尺寸公差為CT8級,表面粗糙度Ra為3.2。根據(jù)機械制造工藝設計簡明手冊表1.4-8,兩步車削(即粗車、半精車)方可滿足其精度要求。粗車 單邊余量Z=2.0mm半精車 單邊余量Z=0.5mm5. 100端面 的加工余量查機械制造工藝設計簡明手冊表2.2-4,得鑄件的單邊加工余量Z=2.0mm,鑄件尺寸公差為CT8級,表面粗糙度Ra為6.3。根據(jù)機械制造工藝設計簡明手冊表1.4-8,一步車削(即粗車)方可滿足其精度要求。6. 100外圓的加工余量查機械制造工藝設計簡明手冊表2.2-4,得鑄件的單邊加工余量Z=1.5mm,鑄件尺寸公差為CT8級,表面粗糙度Ra為1.6。根據(jù)機械制造工藝設計簡明手冊表1.4-8,三步車削(即粗車、半精車、精車)方可滿足其精度要求。粗車 單邊余量Z=1.0mm半精車 單邊余量Z=0.4mm精車 單邊余量Z=0.1mm 7.80沉孔 的加工余量查機械制造工藝設計簡明手冊表2.2-4,得鑄件的單邊加工余量Z=3.5mm,鑄件尺寸公差為CT8級,表面粗糙度Ra為6.3。根據(jù)機械制造工藝設計簡明手冊表1.4-8,一步車削(即粗車)方可滿足其精度要求。8.82端面加工余量查機械制造工藝設計簡明手冊表2.2-4,得鑄件的單邊加工余量Z=2.0mm,鑄件尺寸公差為CT8級,表面粗糙度Ra為6.3。根據(jù)機械制造工藝設計簡明手冊表1.4-8,一步車削(即粗車)方可滿足其精度要求。9.52孔加工余量查機械制造工藝設計簡明手冊表2.2-4,得鑄件的單邊加工余量Z=1.5mm,鑄件尺寸公差為CT8級,表面粗糙度Ra為1.6。根據(jù)機械制造工藝設計簡明手冊表1.4-8,三步車削(即粗車、半精車、精車)方可滿足其精度要求。粗車 單邊余量Z=1.0mm半精車 單邊余量Z=0.4mm精車 單邊余量Z=0.1mm10. 4-M8螺紋的加工余量查機械制造工藝設計簡明手冊表2.2-4,因其加工螺紋的尺寸不大故采用實心鑄造,鑄件尺寸公差為CT8級,表面粗糙度Ra為12.5。根據(jù)機械制造工藝設計簡明手冊表1.4-8,鉆.攻即可方可滿足其精度要求。鉆 單邊余量Z=3.4mm攻 單邊余量Z=0.6mm11. M3螺紋的加工余量查機械制造工藝設計簡明手冊表2.2-4,因其加工螺紋的尺寸不大故采用實心鑄造,鑄件尺寸公差為CT8級,表面粗糙度Ra為12.5。根據(jù)機械制造工藝設計簡明手冊表1.4-8,鉆.攻即可方可滿足其精度要求。鉆 單邊余量Z=1.275mm攻 單邊余量Z=0.225mm12. 3-M6螺紋的加工余量查機械制造工藝設計簡明手冊表2.2-4,因其加工螺紋的尺寸不大故采用實心鑄造,鑄件尺寸公差為CT8級,表面粗糙度Ra為12.5。根據(jù)機械制造工藝設計簡明手冊表1.4-8,鉆.攻即可方可滿足其精度要求。鉆 單邊余量Z=2.55mm攻 單邊余量Z=0.45mm13. 4-M5螺紋的加工余量查機械制造工藝設計簡明手冊表2.2-4,因其加工螺紋的尺寸不大故采用實心鑄造,鑄件尺寸公差為CT8級,表面粗糙度Ra為12.5。根據(jù)機械制造工藝設計簡明手冊表1.4-8,鉆.攻即可方可滿足其精度要求。鉆 單邊余量Z=2.125mm攻 單邊余量Z=0.375mm14. 2-8錐孔的加工余量查機械制造工藝設計簡明手冊表2.2-4,因其加工表面的尺寸不大故采用實心鑄造,鑄件尺寸公差為CT8級,表面粗糙度Ra為6.3。根據(jù)機械制造工藝設計簡明手冊表1.4-8,一步鉆削方可滿足其精度要求。 3.4 基本工時的確立工序01:金屬型澆注工序02:時效處理以消除內(nèi)應力工序03:以155外圓作為定位基準,粗車155下端面、73孔、90孔、半精車90孔工步一:粗車155下端面 1、 切削用量機床為C620-1型臥式車床, 所選刀具為YT5硬質(zhì)合金端面車刀。根據(jù)切削用量簡明手冊第一部分表1.1,由于C620-1型臥式車床的中心高度為200mm(表1.30),故選刀桿尺寸BH=16mm25mm,刀片厚度為4.5mm。根據(jù)表1.3,選擇車刀幾何形狀為卷屑槽帶倒棱型前刀面,前角,后角,主偏角,副偏角,刃傾角,刀尖圓弧半徑。1) 確定切削深度由于單邊余量為2.5mm,可在1次走刀內(nèi)切完。2) 確定進給量根據(jù)表1.4,在粗車QT500-7、刀桿尺寸為16mm25mm、3mm、工件直徑為0100mm時,=0.10.6mm/r按C620-1型臥式車床的進給量(表4.2-9),選擇=0.27mm/r確定的進給量尚需滿足機床進給機構(gòu)強度的要求,故需進行校驗。根據(jù)表1.30,C620-1機床進給機構(gòu)允許的進給力=3530N。根據(jù)表1.21,當2mm,0.35mm/r,=450m/min(預計)時,進給力=760N。的修正系數(shù)為=0.1,=1.17(表1.29-2),故實際進給力為 =7601.17N=889.2N 由于切削時的進給力小于機床進給機構(gòu)允許的進給力,故所選=0.27mm/r可用。3) 選擇車刀磨鈍標準及耐用度 根據(jù)表1.9,車刀后刀面最大磨損量取為1mm,可轉(zhuǎn)位車刀耐用度T=30min。4) 確定切削速度切削速度可根據(jù)公式計算,也可直接由表中查出?,F(xiàn)采用查表法確定切削速度。根據(jù)表1.10,當用YT15硬質(zhì)合金車刀加工鑄件,3mm,0.25mm/r,切削速度=450m/min。切削速度的修正系數(shù)為=0.8,=0.65,=0.81,=1.15,=1.0(均見表1.28),故=4500.80.650.811.15m/min218m/min 448r/min 按C620-1機床的轉(zhuǎn)速(表4.2-8),選擇=460r/min 則實際切削速度=218m/min5) 校驗機床功率由表1.24,3mm,0.27mm/r,46m/min時,=1.7KW。切削功率的修正系數(shù)=1.17,=1.13,=0.8,=0.65(表1.28),故實際切削時的功率為=0.72KW根據(jù)表1.30,當=460r/min時,機床主軸允許功率=5.9KW。 F所以,時工件不會轉(zhuǎn)動,故本夾具可安全工作。根據(jù)工件受力切削力、夾緊力的作用情況,找出在加工過程中對夾緊最不利的瞬間狀態(tài),按靜力平衡原理計算出理論夾緊力。最后為保證夾緊可靠,再乘以安全系數(shù)作為實際所需夾緊力的數(shù)值。即:安全系數(shù)K可按下式計算有:式中:為各種因素的安全系數(shù),查參考文獻5表可得: 所以有: 該孔的設計基準為中心軸,故以回轉(zhuǎn)面做定位基準,實現(xiàn)“基準重合”原則;參考文獻,因夾具的夾緊力與切削力方向相反,實際所需夾緊力F夾與切削力之間的關(guān)系F夾KF軸向力:F夾KF (N)扭距:Nm在計算切削力時必須把安全系數(shù)考慮在內(nèi),安全系數(shù)由資料機床夾具設計手冊查表可得:切削力公式: 式(2.17)式中 查表得: 即:實際所需夾緊力:由參考文獻16機床夾具設計手冊表得: 安全系數(shù)K可按下式計算,由式(2.5)有:式中:為各種因素的安全系數(shù),見參考文獻16機床夾具設計手冊表 可得: 所以 由計算可知所需實際夾緊力不是很大,為了使其夾具結(jié)構(gòu)簡單、操作方便,決定選用螺旋夾緊機構(gòu)。1.1.4 4.4 鉆孔與工件之間的切屑間隙鉆套的類型和特點:1、固定鉆套:鉆套直接壓入鉆模板或夾具體的孔中,鉆模板或夾具體的孔與鉆套外圓一般采用H7/n6配合,主要用于加工量不大,磨損教小的中小批生產(chǎn)或加工孔徑甚小,孔距離精度要求較高的小孔。2、可換鉆套:主要用在大批量生產(chǎn)中,由于鉆套磨損大,因此在可換鉆套和鉆模板之間加一個襯套,襯套直接壓入鉆模板的孔內(nèi),鉆套以F7/m6或F7/k6配合裝入襯套中。3、快換鉆套:當對孔進行鉆鉸等加工時,由于刀徑不斷增大,需要不同的導套引導刀具,為便于快速更換采用快換鉆套。4、特殊鉆套:尺寸或形狀與標準鉆套不同的鉆套統(tǒng)稱特殊鉆套。鉆套下端面與工件表面之間應留一定的空隙C,使開始鉆孔時,鉆頭切屑刃不位于鉆套的孔中,以免刮傷鉆套內(nèi)孔,如圖4.3。圖4.3 切屑間隙 C=(0.31.2)d。在本次夾具鉆模設計中考慮了多方面的因素,確定了設計方案后,選擇了C=8。因為此鉆的材料是鑄件,所以C可以取較小的值。1.1.5 4.5 鉆模板在導向裝置中,導套通常是安裝在鉆模板上,因此鉆模板必須具有足夠的剛度和強度,以防變形而影響鉆孔精度。鉆模板按其與夾具體連接的方式,可分為固定式鉆模板、鉸鏈式鉆模板、可卸式鉆模板、滑柱式鉆模板和活動鉆模板等。在此套鉆模夾具中選用的是可卸式鉆模板,在裝卸工件時需從夾具體上裝上或卸下,鉆螺栓緊固,鉆模精度較高。41.1.6 4.6定位誤差的分析3) 夾具安裝誤差因夾具在機床上的安裝不精確而造成的加工誤差,稱為夾具的安裝誤差。1.1.7 圖5-2中夾具的安裝基面為平面,因而沒有安裝誤差,=0.4) 夾具誤差因夾具上定位元件、對刀或?qū)蛟?、分度裝置及安裝基準之間的位置不精確而造成的加工誤差,稱為夾具誤差。夾具誤差主要包括定位元件相對于安裝基準的尺寸或位置誤差;定位元件相對于對刀或?qū)蛟ò瑢蛟g)的尺寸或位置誤差;導向元件相對于安裝基準的尺寸或位置誤差;若有分度裝置時,還存在分度誤差。以上幾項共同組成夾具誤差。5) 加工方法誤差因機床精度、刀具精度、刀具與機床的位置精度、工藝系統(tǒng)的受力變形和受熱變形等因素造成的加工誤差,統(tǒng)稱為加工方法誤差。因該項誤差影響因素多,又不便于計算,所以常根據(jù)經(jīng)驗為它留出工件公差的1/3.計算時可設。2. 保證加工精度的條件工件在夾具中加工時,總加工誤差為上述各項誤差之和。由于上述誤差均為獨立隨機變量,應用概率法疊加。因此保證工件加工精度的條件是即工件的總加工誤差應不大于工件的加工尺寸。為保證夾具有一定和夾具總圖上各項公差值確定得是否合理。知此方案可行。在分析計算工件加工精度時,需留出一定的精度儲備量。因此將上式改寫為或 當時,夾具能滿足工件的加工要求。值的大小還表示了夾具使用壽命的長短和夾具總圖上各項公差值確定得是否合理。知此方案可行。4.7 鉆套、襯套、鉆模板設計與選用工藝孔的加工只需鉆切削就能滿足加工要求。故選用可換鉆套(其結(jié)構(gòu)如下圖所示)以減少更換鉆套的輔助時間。為了減少輔助時間采用可換鉆套,以來滿足達到孔的加工的要求。表dDD1Ht基本極限偏差F7基本極限偏差D601+0.016+0.0063+0.010+0.004669-0.00811.84+0.016+0.00871.82.6582.63698121633.3+0.022+0.0103.347+0.019+0.010104581156101110162068+0.028+0.01112+0.023+0.0121581015181220251012+0.034+0.0161822121522+0.028+0.01526162836151826300.0121822+0.041+0.02030342036HT200222635+0.033+0.017392630424625HT200563035+0.050+0.0254852354255+0.039+0.02059305667424811066485070740.040鉆模板選用固定鉆模板,用沉頭螺釘錐銷定位于夾具體上。1.1.8 4.8 確定夾具體結(jié)構(gòu)和總體結(jié)構(gòu)對夾具體的設計的基本要求(1)應該保持精度和穩(wěn)定性在夾具體表面重要的面,如安裝接觸位置,安裝表面的刀塊夾緊安裝特定的,足夠的精度,之間的位置精度穩(wěn)定夾具體,夾具體應該采用鑄造,時效處理,退火等處理方式。(2)應具有足夠的強度和剛度保證在加工過程中不因夾緊力,切削力等外力變形和振動是不允許的,夾具應有足夠的厚度,剛度可以適當加固。(3)結(jié)構(gòu)的方法和使用應該不錯夾較大的工件的外觀,更復雜的結(jié)構(gòu),之間的相互位置精度與每個表面的要求高,所以應特別注意結(jié)構(gòu)的過程中,應處理的工件,夾具,維修方便。再滿足功能性要求(剛度和強度)前提下,應能減小體積減輕重量,結(jié)構(gòu)應該簡單。(4)應便于鐵屑去除在加工過程中,該鐵屑將繼續(xù)在夾在積累,如果不及時清除,切削熱的積累會破壞夾具定位精度,鐵屑投擲可能繞組定位元件,也會破壞的定位精度,甚至發(fā)生事故。因此,在這個過程中的鐵屑不多,可適當增加定位裝置和夾緊表面之間的距離增加的鐵屑空間:對切削過程中產(chǎn)生更多的,一般應在夾具體上面。(5)安裝應牢固、可靠夾具安裝在所有通過夾安裝表面和相應的表面接觸或?qū)崿F(xiàn)的。當夾安裝在重力的中心,夾具應盡可能低,支撐面積應足夠大,以安裝精度要高,以確保穩(wěn)定和可靠的安裝。夾具底部通常是中空的,識別特定的文件夾結(jié)構(gòu),然后繪制夾具布局。圖中所示的夾具裝配。加工過程中,夾具必承受大的夾緊力切削力,產(chǎn)生沖擊和振動,夾具的形狀,取決于夾具布局和夾具和連接,在因此夾具必須有足夠的強度和剛度。在加工過程中的切屑形成的有一部分會落在夾具,積累太多會影響工件的定位與夾緊可靠,所以夾具設計,必須考慮結(jié)構(gòu)應便于鐵屑。此外,夾點技術(shù),經(jīng)濟的具體結(jié)構(gòu)和操作、安裝方便等特點,在設計中還應考慮。在加工過程中的切屑形成的有一部分會落在夾具,切割積累太多會影響工件的定位與夾緊可靠,所以夾具設計,必須考慮結(jié)構(gòu)應便排出鐵屑。 結(jié) 論課程設計即將結(jié)束了,時間雖然短暫但是它對我們來說受益菲淺的,通過這次的課程設計使我們不再是只知道書本上的空理論,不再是紙上談兵,而是將理論和實踐相結(jié)合進行實實在在的設計,使我們不但鞏固了理論知識而且掌握了設計的步驟和要領,使我們更好的利用圖書館的資料,更好的更熟練的利用我們手中的各種設計手冊和AUTOCAD等制圖軟件,為我們進行畢業(yè)設計打下了良好的基礎。課程設計使我們認識到了只努力的學好書本上的知識是不夠的,還應該更好的做到理論和實踐的結(jié)合。因此同學們非常感謝老師給我們的辛勤指導,使我們學到了好多,也非常珍惜學院給我們的這次設計的機會。致 謝這次課程設計使我收益不小,為我今后的學習和工作打下了堅實和良好的基礎。但是,查閱資料尤其是在查閱切削用量手冊時,數(shù)據(jù)存在大量的重復和重疊,由于經(jīng)驗不足,在選取數(shù)據(jù)上存在一些問題,不過我的指導老師每次都很有耐心地幫我提出寶貴的意見,在我遇到難題時給我指明了方向,最終我很順利的完成了課程設計。這次課程設計成績的取得,與指導老師的細心指導是分不開的。在此,我衷心感謝我的指導老師,特別是每次都放下她的休息時間,耐心地幫助我解決技術(shù)上的一些難題,她嚴肅的科學態(tài)度,嚴謹?shù)闹螌W精神,精益求精的工作作風,深深地感染和激勵著我。從課題的選擇到項目的最終完成,她都始終給予我細心的指導和不懈的支持。多少個日日夜夜,她不僅在學業(yè)上給我以精心指導,同時還在思想、生活上給我以無微不至的關(guān)懷,除了敬佩指導老師的專業(yè)水平外,她的治學嚴謹和科學研究的精神也是我永遠學習的榜樣,并將積極影響我今后的學習和工作。在此謹向指導老師致以誠摯的謝意和崇高的敬意。 參 考 文 獻1, 鄒青 主編 機械制造技術(shù)基礎課程設計指導教程 北京: 機械工業(yè)出版社 2004,8 2, 趙志修 主編 機械制造工藝學 北京: 機械工業(yè)出版社 1984,23, 孫麗媛 主編 機械制造工藝及專用夾具設計指導 北京:冶金工業(yè)出版社 2002,12 4, 李洪 主編 機械加工工藝手冊 北京: 北京出版社 1990,125, 鄧文英 主編 金屬工藝學 北京: 高等教育出版社 20006, 黃茂林 主編 機械原理 重慶: 重慶大學出版社 2002,77, 丘宣懷 主編 機械設計 北京: 高等教育出版社 19978, 儲凱 許斌 等主編 機械工程材料 重慶: 重慶大學出版社 1997,129, 廖念釗 主編 互換性與技術(shù)測量 北京: 中國計量出版社 2000,110,樂兌謙 主編 金屬切削刀具 北京: 機械工業(yè)出版社 1992,1211,李慶壽 主編 機床夾具設計 北京: 機械工業(yè)出版社 1983,412,陶濟賢 主編 機床夾具設計 北京: 機械工業(yè)出版社 1986,413, 機床夾具結(jié)構(gòu)圖冊 貴州:貴州人民出版社 1983,714,龔定安 主編 機床夾具設計原理 陜西:陜西科技出版社,1981,715,李益民 主編 機械制造工藝學習題集 黑龍江: 哈兒濱工業(yè)大學出版社 1984, 716, 周永強等 主編 高等學校畢業(yè)設計指導 北京: 中國建材工業(yè)出版社 2002,1217,李益民等 主編 機械制造工藝設計簡明手冊 北京: 機械工業(yè)出版社 1992,1218,徐鴻本等 主編 切削手冊 北京: 機械工業(yè)出版社 2003,1130, J.M. Superior 2, Cranfield accepted 26 relies requirements, taking this as a general concept, is to make should be always linked to a requirement, and its purpose is International Journal of Machine Tools Fixture knowledge modelling, Fixture functional requirements 1. Introduction The main objective of any design theory is to provide a suitable framework and methodology for the definition of a sequence of activities that conform the design process of a product or system 1. In general, all of them identify requirements as the starting point in the design process. In fact, the engineering discipline dealing with product design can be defined as the one that considers scientific and engineering knowledge to create product definitions and design solutions based on ideas and concepts derived from requirements and constraints 24. For this research, a relevant issue when considering explicit the meaning of two main terms: Functional Requirement (FR) and Constraint (C). A functional requirement, as it stated by different authors, represents what the product has to or must do independently of any possible solution, 2,4. A FR is a kind of requirement, and considering some basic principles widely recognized in the field of Requirements Engineering, we could add it is a unique and unambiguous statement in natural language of a single functionality, written in a way that it can be ranked, traced, measured, verified, and validated. A constraint can be defined as a restriction that in general affects some kind of requirement, and it limits the range of possible solutions while satisfying the requirements. So, a constraint A functional approach for the formalization R. Hunter a , J. Rios b, * a Department of Mechanical and Manufacturing Engineering, Escuela Tecnica Jose Gutierrez Abascal, b Currently in Enterprise Integration (Bldg 53), Received 14 January 2005; Available online Abstract The design of machining fixtures is a highly complex process that of the fixture design process Perez a , A. Vizan a de Ingenieros Industriales, Universidad Politecnica de Madrid, 28006 Madrid, Spain University, Cranfield, MK43 0AL, UK 14 April 2005 August 2005 on designer experience and his/her implicit knowledge to achieve Manufacture 46 (2006) 683697 functional requirements should be defined in the functional domain, which brings on the scene the issue of how to define and represent the functionality of a product. The way used to represent it will affect the reasoning process of the designer, and in that sense, the mapping between the functional 0890-6955/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijmachtools.2005.04.018 * Corresponding author. Tel.: C44 1234 754936; fax.: C44 1234 750852. to narrow the design outcome to acceptable solutions. Considering the Theory of Axiomatic Design 4, ably, the first aspect to think about is how the requirements are represented or declared. As it has been previously and the physical domains, being the later the one where the design solutions are developed. Several authors have investigated the concept of functionality and functional representation 2,58. Their design approach provides a view based on the Function-Behaviour-Structure frame- work, where function is defined using structure and behaviour 6. The objective is to fill the gap that allows a designer to progress from FRs to physical design solutions. The approach is that product functions are achieved by means of its structure, which seems to lead to an iterative causal approach, where solutions are sought until the selected structure causes the intended functionality. The approach adopted in the research presented in this paper is based on the definition of Fixture Functional Components (FFC), which can satisfy the fixture functionality, and on the mapping between such FFC and fixture commercial elements. An advanced approach to the definition of requirements and functions comes from the creation of ontologies. The ontological approach pursues the definition of the meaning of terms making use of some kind of logic, and the definition of axioms to enable automatic deduction and reasoning 9. The ontological approach has got a higher relevance since the representation of knowledge is considered the key factor in whatever engineering process, and it has been recognized as a way to facilitate the integration of engineering applications 10, to describe functional design knowledge 7, and to define requirements 11. Considering a purist approach, if an ontology does not include axioms to enable reasoning then it could be considered more like an information model, and in this sense, this is the approach developed in the work presented in this paper. When considering the methodologies developed for the design of fixtures, it can be stated that in general they are rational and propose a series of steps to follow. For example, the methodologies proposed by Scallan and Henriksen 12, 13, make use of this approach to describe in general terms the information needed in each stage of the fixture design process. Basically, the importance of modelling in detail such information, which mainly is related to fixture requirements, fixture functionality, fixture components, manufacturing resources, manufacturing processes, and design rules; resides on the possibility to automate the design process through the development of a knowledge- based application or system. It is relevant to mention that several authors have already aimed to develop knowledge- based applications for fixture design, none of them based on a functional approach, some of the most recently published works can be found in the Refs. 1419. In the following sections, this paper presents a methodology to formalize the design process of machin- ing fixtures based on the engineering concepts of functional requirements and fixture functions 20. The formalization of the functional requirements is achieved through the application of a structured way of specifica- R. Hunter et al. / International Journal of Machine684 tion via natural language. Additionally, IDEF0, MOKA mentioned, the way of expressing requirements definitively affects their interpretation and the creation of a design solution. In this sense, it is widely accepted, that the use of natural language is the most common way of expressing requirements and in consequence, their writing becomes an important issue. The anatomy proposed by Alexander et al. 24 to write requirements in a semi-structured way is used as basis to declare the functional requirements and constraints of fixtures 20. In machining, work holding is a key aspect, and fixtures are the elements responsible to satisfy this general goal. In their design process, the starting point is the definition of the machining fixtures functional requirements and constraints. Usually, a fixture solution is made of one or several physical elements, as a whole the designed fixture solution must methodology, and UML diagrams are used to capture, represent and formalize knowledge, being the ultimate goal to facilitate the automation of the fixture design process. The IDEF0 method is used to create an activity model of the fixture design process, allowing the identification of the information used in each one of the different tasks it comprises. UML has been used to complement the IDEF0 model by representing the interaction between the activities of the process. The MOKA methodology together with UML, are used to capture and represent knowledge involved in the fixture design process. Finally, to validate the proposed methodology, partial results obtained from the development of a prototype knowledge-based application are presented. 2. Analysis of machining fixtures requirements In Section 1, two terms have been defined: functional requirement and constraint. Requirements have always existed, the way in which they are expressed, and how they are integrated in the product design process, are aspects that are addressed from different disciplines, for example: product design engineering and requirements engineering among others. In general, Requirements Engineering refers to the discipline dealing with the capture, formalization, representation, analysis, management and verification of requirements fulfilment. However, all these aspects need to be integrated in the product design process, and require- ments should lead to the definition of the possible product design solutions, which in general demands an integrated view of the requirements issue. It is important to keep in mind that the development of such discipline is strongly related to Software Engineering and Systems Engineering, and in fact much of the research related to requirements come from authors from these engineering areas 2123. When considering the analysis of requirements, prob- Tools in this case a KBE application for the design of machining fixtures; and the second one is the functional requirements of the components subject of the application; in this case machining fixtures. An example of the former ones for an application developed in collabor- ation with an industrial partner is presented by Rios et al. 28. For this kind of FRs specification, UML seems to be for fixture FRs. MOKA ICARE: ENTITY Name Reference Entity Type Function Constraints Functional Requirements for the Fixture Constraints Functional Requirements (CFR) Structure Define constrains to Functional Requirements for the fixture t support the fun e structur de of the fixtur Re 03-07-04 1.0 In progres form R. Hunter et al. / International Journal of Machine Tools it is independent of the knowledge representation to be used in the implementation, and it does not require from the fixture designer a deep knowledge of any software modelling technique. The definition of these fixture functions is a first step in the modelling needed for a KBE application development. For example, considering stability as one of the main constraints affecting the fixture FRs, any fixture functional solution should satisfy this constraint. To achieve that, it would be necessary to define a fixture function (FF) for stability methodology. Part machining: operations strategies cutting parameters cutting tool parameters volume to remove Optimization method Analysis model Constraints: Deformation Stability Interference Part orientation Part support: support points support vectors support surfaces Determine cut Determ Determine cl Determine cl Determ Determ R. Hunter et al. / International Journal of Machine Tools & Manufacture 46 (2006) 683697 689 Part location: locating points locating vectors locating surfaces Part information: mechanical properties friction coefficient raw material shape and dimensions part shape and dimensions tolerances evaluation, and this function could be called from the fixture function clamp (clamp_FF) presented as example in the Fig. 6. From a high level perspective, the stability_FF would need as input: part information (i.e.: material mechanical properties, shape, dimensions and tolerances), machining process information (i.e.: machining operations, machining strategies, volumes to remove, cutting parameters, cutting tool parameters), and fixture functional element information (i.e.: function, constraints, rules, containing volume, point and vector of application). Part of this information will have to be used to determine some derived parameters like cutting and allowed clamping forces. Making use of such infor- mation together with an analysis model, for example the one proposed by Liao et al. 32, and optimization methods, for example the one proposed by Pelinescu et al. 33, such stability_FF could be developed and implemented. The complexity in the detailed specification of such stability_FF is extremely high, and demands its own research by itself Fig. 6. High-level function template Fig. 7. Structure of the AFNOR fixture Fixture functional elements: function constraints rules containing volume Function Clamp (clamp_FF) F4 ting forces ine clamping surface amping points amping orientation ine clamping forces ine clamping elements 32,34,35, but the definition of a high level function where all the information needed for its development could be represented, is one of the objectives of the research presented in this paper. Phase 3: The third phase, functional design (FD), is aimed to create a set of functional solutions for the fixture design. A functional solution is independent of any particular commercial fixture component, and it is rep- resented by means of a set of fixture functional elements. A fixture functional element satisfies at least one of the functions identified as inherent to a fixture, i.e.: centre, position, orientate, clamp, and support. These elements are represented by means of graphical symbols, also called functional symbols, which apart from the functionality also represent some qualifiers that affect them. Such fixture functional symbols are based on the technological elements defined in the AFNOR standard NF E 04-013 - 1985 36. Fig. 7 presents their structure, which comprises: kind of representation. technological elements. Type Function *Surface class: Machined *Type contact surface: Punctual technology, state of the part surface, function of the technological element, and the kind of contact between the part surface and the fixture element. In order to progress from the functional design to the detailed one, which is the next phase, it has been defined a mapping table between functional symbols and commercial fixture elements 20, Table 2 represents an example. For the creation of the possible functional solutions a set of input information, analysis models, optimization func- tions, and rules has to be included in the software functions previously defined in the second phase. Basically, the inputs defined are: Part information: material mechanical properties, shape and dimensions of the part to be machined, and the associated tolerances. Functional element information: functions, associated restrictions, orientation, containing volume, contact parameters, and location point. Part manufacturing process: sequence of operations, and for each operation: machining strategy, cutting para- meters, cutting tool, and volume to remove. Production estimation of: number of set-ups, set-up times, batch size, production rate, and target cost. Resource information: machine morphology, and machine capacity. Functional design brings benefits to design environments Table 2 Relation between AFNOR elements and fixture commercial components Fixture function Functional representation Clamp function (Attribute) Type technology Surface Class *Type technology *Surface class *Type contact surface *Type function R. Hunter et al. / International Journal of Machine690 where the solution is mainly driven by the satisfaction of quantitative functions, as opposite to environments where subjective aspects like aesthetics has a major relevance. In particular, in the fixture design environment, the advantage of creating a functional solution derives from not using a full library of commercial fixture elements but a reduced number of basic functional elements, which can be transformed into the former ones in a second design phase. And this is particularly relevant when some kind of artificial intelligence technique is going to be applied in the implementation phase, since many of these techniques are based on the initial generation of a complete design space where the possible solutions are contained, if the design space can be reduced then the determination of the solutions can be done more efficiently. And with the functional design approach the design space is divided in two subsets, one subset dealing with the functional solution and other dealing with the physical one. Phase 4: The fourth phase, detailed design (DD) comprises the creation of detailed solutions from a functional one. To undertake this phase the mapping tables previously mentioned and the corresponding interpretation rules have to be used. To mention as well, that the fixture software functions apply in a similar way, but with a different input, which basically is the geometry (containing volume) associated with the fixture element, this is particularly relevant for the interference checking. How- ever, in this case the space of possible solutions is reduced by the fact that only those commercial elements that can be mapped to the functional ones can be used, and that a point of application and an orientation vector for the elements to be used are data as well. A detailed solution contains the finalfixturecommercialelementstobeusedinthe machining of the part and their set-up. Finally, the fifth phase, validation of the design (FV), is aimed to make a final evaluation and validation of the functional requirements and their associated constraints defined in the first phase. However, it is important to mention that in addition to a final validation, the functional approach, with the separation of the design spaces in two parts, allows implementing the validation in two prior stages. First in the functional design phase, so the possible functional design Type contact surface *Type function: Machining Fixture Commercial elements selected type *Type technology: Clamp Tools & Manufacture 46 (2006) 683697 solutions fulfil the imposed requirements, and second in the detailed design phase. This can be made by means of the optimization method that can be included in the Fixture Function (FF), as it was previously mentioned in the Phase 3. Based on this methodology, a detailed definition of the fixture functional design process is presented in the next section. 4. Fixture functional design process model As it was mentioned in the introduction, the functional approach to design has drawn the attention of several researchers 2,5,6,7,8. However, as it is pointed out by Kitamura 7, in general, the functional knowledge is left implicit, there are not clear definitions of the functional concepts, and the generic functions proposed in the literature are too generic to be used by designers. In this sense, the ontological approach is an interesting contri- bution to formalize the functional design knowledge. The approach adopted in this research deals with the definition of what would be the first step in a fixture ontology development, which is the modelling of the fixture information. The functional approach to fixture design, based on an information model definition, has some characteristics that can be deduced from the facts presented in the previous sections, that is: a reduced number of functions that a fixture has to perform, the possibility of formalizing the FRs specification with quantitative qualifiers, and the reduction of the design space by using functional elements. However, prior to the definition of any fixture information model, it is necessary to define the fixture design process and the information flow along it. Following is the activity model developed in this research to represent the fixture design process. The model is represented using the IDEF0 technique and UML, and it allows identifying the knowledge units needed during such process, and the interaction among used modelling techniques to represent the process and part of the information related to the fixture design process 37,38, but without taking a functional approach to it. Starting with the input knowledge units related to part geometry, manufacturing process plan, machining resources, and following the IDEF0 methodology, the first step is to create a context diagram or highest-level diagram, of the fixture design process. The knowledge units that constitute the final output to the process are the fixture detailed design, and the fixture assembly plan. The resource knowledge units are the machine-tool unit and the modular fixture elements one. The IDEF0 methodology is based on the definition of a hierarchical b
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