【正文】 應(yīng)采用通用機(jī)床和專(zhuān)用工夾具。 （2）鍛件 機(jī)械強(qiáng)度要求高的鋼制作，一般要用鍛件毛坯。生產(chǎn)效率高。鑄件公稱(chēng)尺寸所允許的最大尺寸和最小尺寸之差稱(chēng)為鑄件尺寸公差。 基面的選擇基面的選擇是工藝規(guī)程設(shè)計(jì)中的重要工作之一。3．工藝方案的比較與分析上述兩個(gè)方案的特點(diǎn)在于：方案一是先加工 φ55 孔，以便于后續(xù)加工，并利用了兩件合鑄的優(yōu)勢(shì)，提高了工作效率，然后在銑床上把所有銑的工序全部弄完，省去了在各機(jī)床間切換的麻煩，最后加工孔；方案二是先銑斷，使之為兩個(gè)工件，分別加工。機(jī)床：Z5125A 立式鉆床，專(zhuān)用夾具。,過(guò)渡刃 Krε=30176。查《切削手冊(cè)》表 ，壽命 T=180min（4） 計(jì)算切削速度 按《切削手冊(cè)》 ，將 f 降一級(jí)為 f= mm/z。（1）銑削深度 因?yàn)榍邢髁枯^小，故可以選擇 ap=，一次走刀即可完成所需長(zhǎng)度。（5)校驗(yàn)機(jī)床功率 查《切削手冊(cè)》Pcc=,而機(jī)床所能提供功率為 PcmPcc。正確地設(shè)計(jì)并合理的使用夾具，是保證加工質(zhì)量和提高生產(chǎn)率，從而降低生產(chǎn)成本的重要技術(shù)環(huán)節(jié)之一。 （2）提高勞動(dòng)生產(chǎn)率 使用夾具裝夾工件方便、快速工件不需劃線找正，可顯著的減少輔助工時(shí)，提高勞動(dòng)生產(chǎn)率，工件在夾具裝夾后提高了工件的剛性，因此可加大切削用量，提高勞動(dòng)生產(chǎn)率，可使用多工位夾具，并可采用高小夾緊機(jī)構(gòu)，進(jìn)一步提高勞動(dòng)生產(chǎn)率。家具體上部加工的毛面與工件表面之間應(yīng)保證有一定的空隙，以免安裝時(shí)產(chǎn)生干涉，空隙大小可按以下經(jīng)驗(yàn)數(shù)據(jù)選取:夾具體是毛面，弓箭也是毛面，去 8~15mm；夾具體是毛面，而工件是光面時(shí)，取 4~10mm。總 結(jié)為期兩個(gè)半月的畢業(yè)設(shè)計(jì)已經(jīng)接近尾聲，回顧整個(gè)過(guò)程，我組同學(xué)在歐老師的指導(dǎo)下，取得了可喜的成績(jī)，畢業(yè)設(shè)計(jì)作為大學(xué)學(xué)習(xí)中的重要環(huán)節(jié)，使理論與實(shí)踐更加接近，加深了理論知識(shí)的理解，強(qiáng)化了生產(chǎn)實(shí)習(xí)中的感性認(rèn)識(shí)。（4）Chip control. Thus, good machinability good surface finish and integrity, long tool life, and low force And power requirements. As for chip control, long and thin (stringy) cured chips, if not broken up, can severely interfere with the cutting operation by being entangled in the cutting zone.Because of the plex nature of cutting operations, it is difficult to establish relationships that quantitatively define the machinability of a material. In manufacturing plants, tool life and surface roughness are generally considered to be the most important factors in machinability. Although not used much any more, approximate machinability ratings are available in the example below.1. Machinability Of SteelsBecause steels are among the most important engineering materials , their machinability has been studied extensively. The machinability of steels has been mainly improved by adding lead and sulfur to obtain socalled freemachining steels.Resulfurized and Rephosphorized steels. Sulfur in steels forms manganese sulfide inclusions (secondphase particles), which act as stress raisers in the primary shear zone. As a result, the chips produced break up easily and are small。提高了我們的思考、解決問(wèn)題創(chuàng)新設(shè)計(jì)的能力，為以后的設(shè)計(jì)工作打下了較好的基礎(chǔ)。 夾具設(shè)計(jì)定位基準(zhǔn)的選擇據(jù)《夾具手冊(cè)》知定位基準(zhǔn)應(yīng)盡可能與工序基準(zhǔn)重合，在同一工件的各道工序中，應(yīng)盡量采用同一定位基準(zhǔn)進(jìn)行加工。（4）怎樣使夾具使用合理，便于裝卸。由于工件在加工時(shí)，受到各種力的作用若不將其固定，則工件會(huì)松動(dòng)、脫離，因此夾緊為工件提高了安全和可靠的加工條件。他們時(shí)機(jī)床和工件之間的連接裝置，使工件相對(duì)于機(jī)床獲得正確的位置。（5)校驗(yàn)機(jī)床功率 查《切削手冊(cè)》Pcc=,而機(jī)床所能提供功率為 PcmPcc。刀具：W18Cr4V 硬質(zhì)合金鋼端銑刀,牌號(hào) YG6。由于是對(duì)稱(chēng)銑，選較小量 f= mm/z。所以進(jìn)給量 f= ② 鉆削速度切削速度：根據(jù)手冊(cè)表 及表 ，查得切削速度 V=18m/min。工序 4 粗、精銑 φ55 孔兩端面，以 φ25 孔定位，選用 XA6132 臥式銑床和專(zhuān)用夾具。當(dāng)設(shè)計(jì)基準(zhǔn)與工序基準(zhǔn)不重合時(shí)，應(yīng)該進(jìn)行尺寸換算，這在以后還要專(zhuān)門(mén)計(jì)算，此處不在重復(fù)。帶孔的模鍛件不能直接鍛出通孔，應(yīng)留沖孔連皮等。選擇毛坯時(shí)應(yīng)該考慮如下幾個(gè)方面的因素：（1） 零件的生產(chǎn)綱領(lǐng)大量生產(chǎn)的零件應(yīng)選擇精度和生產(chǎn)率高的毛坯制造技術(shù)，用于毛坯制造的昂貴費(fèi)用可由材料消耗的減少和機(jī)械加工費(fèi)用的降低來(lái)補(bǔ)償。主要適用于批量較大的中小型零件。 確定毛坯的制造形式零件是由毛坯按照其技術(shù)要求經(jīng)過(guò)各種加工而最后形成的。 (1)確定各表面的加工方法。3．有良好的勞動(dòng)條件在制訂工藝方案上要注意采取機(jī)械化或自動(dòng)化的措施，盡量減輕工人的勞動(dòng)強(qiáng)度，保障生產(chǎn)安全、創(chuàng)造良好、文明的勞動(dòng)條件。該撥叉在改換檔位是要承受彎曲應(yīng)力和沖擊載荷的用，因此該零件具有足夠的強(qiáng)度和剛度以及韌性，以適應(yīng)撥叉的工作條件。我研究的課題是撥叉。畢 業(yè) 設(shè) 計(jì)（論 文）題目：變速撥叉零件的機(jī)械加工工藝及工藝裝備摘 要本論文設(shè)計(jì)的是變速撥叉的加工工序、設(shè)計(jì)方案、計(jì)算過(guò)程以及鉆孔的夾具設(shè)計(jì)。目前，計(jì)算機(jī)集成制造系統(tǒng)（CIMS）正在研究和開(kāi)發(fā)，也即將投入使用，它的出現(xiàn)將會(huì)更大程度的改變現(xiàn)代世界的機(jī)械行業(yè)。當(dāng)需要變速時(shí)，操縱變速桿，變換操縱機(jī)構(gòu)就通過(guò)撥叉頭部的操縱 槽帶動(dòng)撥叉與變速叉軸一起在變速箱中滑移，撥插腳撥動(dòng)雙聯(lián)變換齒輪在花鍵上滑動(dòng)一改變檔位，從而改變速度。充分利用現(xiàn)有生產(chǎn)條件，少花錢(qián)、多辦事。4．制訂零件的機(jī)械加工工藝路線。模鍛的生產(chǎn)效率高，但需要專(zhuān)用的模具，且鍛錘的噸位也要比自由鍛造大。生產(chǎn)效率高，零件的精度高，表面粗糙度值小，一般可不再時(shí)行精加工，但金屬粉末成本較高，適于大批大量生產(chǎn)中壓制形狀較簡(jiǎn)單的小型零件。對(duì)于鍛件應(yīng)考慮鍛造圓角和模鍛斜度。 主要因該考慮基準(zhǔn)重合的問(wèn)題。工序 3 鉆、擴(kuò)、粗鉸、精鉸 Φ25 孔，以 Φ40 外圓為定位基準(zhǔn)，選用 Z5125A 立式鉆床和專(zhuān)用夾具。此工序采用Φ23 的麻花鉆。查得 f=~。刀具：高速鋼鑲齒三面刃銑刀(1)進(jìn)給量 f 查表 af= mm/z (2)切削速度 vc 查得 v=27 m/mind=175mm 齒數(shù) z=16則 ns＝ ＝ =49 r/min1000vπ d 1000175按機(jī)床選取 nw= r/min所以實(shí)際切削速度 vc = = = m/minndπ1000 π 175(3)基本工時(shí) tt = =2 minLi+Lw+Lonf 175+16 工序 6：粗銑、精銑尺寸為 40 的外側(cè)面機(jī)床：XA6132 臥式銑床，專(zhuān)用夾具。查《切削手冊(cè)》表 ，壽命 T=180min（4）計(jì)算切削速度 查得 Vc＝98mm/s，則 n=439r/min,Vf=490mm/s據(jù) XA6132 銑床參數(shù)，選擇 nc=475r/min,Vfc=475mm/s,則實(shí)際切削速度 V c=*80*475/1000=,實(shí)際進(jìn)給量為 f zc=V fc/ncz=475/(300*10)=。在加工中除了需要機(jī)床、刀具、量具之外，成批生產(chǎn)時(shí)還要用機(jī)床夾具。（2）夾緊 工件定位后將其固定，使其在加工過(guò)程中保持定位位置不錯(cuò)的操作。（3）設(shè)計(jì)的夾具怎樣排削；此次加工利用麻花鉆和擴(kuò)刀、鉸刀，排削通過(guò)鉆模板與工件之間的間隙排削。設(shè)計(jì)時(shí)要在滿(mǎn)足精度的前提下提高勞動(dòng)生產(chǎn)效率，降低勞動(dòng)強(qiáng)度?？偟膩?lái)說(shuō)，這次設(shè)計(jì)，使我們?cè)诨纠碚摰木C合運(yùn)用及正確解決實(shí)際問(wèn)題等方面得到了一次較好的訓(xùn)練。 this improves machinability. The size, shape, distribution, and concentration of these inclusions significantly influence machinability. Elements such as tellurium and selenium, which are both chemically similar to sulfur, act as inclusion modifiers in resulfurized steels.Phosphorus in steels has two major effects. It strengthens the ferrite, causing increased hardness. Harder steels result in better chip formation and surface finish. Note that soft steels can be difficult to machine, with builtup edge formation and poor surface finish. The second effect is that increased hardness causes the formation of short chips instead of continuous stringy ones, thereby improving machinability.Leaded Steels. A high percentage of lead in steels solidifies at the tip of manganese sulfide inclusions. In nonresulfurized grades of steel, lead takes the form of dispersed fine particles. Lead is insoluble in iron, copper, and aluminum and their alloys. Because of its low shear strength, therefore, lead acts as a solid lubricant and is smeared over the toolchip interface during cutting. This behavior has been verified by the presence of high concentrations of lead on the toolside face of chips when machining leaded steels.When the temperature is sufficiently highfor instance, at high cutting speeds and feeds —the lead melts directly in front of the tool, acting as a liquid lubricant. In addition to this effect, lead lowers the shear stress in the primary shear zone, reducing cutting forces and power consumption. Lead can be used in every grade of steel, such as 10xx, 11xx, 12xx, 41xx, etc. Leaded steels are identified by the letter L between the second and third numerals (for example, 10L45). (Note that in stainless steels, similar use of the letter L means “l(fā)ow carbon,” a condition that improves their corrosion resistance.)However, because lead is a wellknown toxin and a pollutant, there are serious environmental concerns about its us