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存檔編碼：無(wú)無(wú)錫錫太太湖湖學(xué)學(xué)院院 2013 屆屆畢畢業(yè)業(yè)作作業(yè)業(yè)周周次次進(jìn)進(jìn)度度計(jì)計(jì)劃劃、檢檢查查落落實(shí)實(shí)表表 系別：信機(jī)系 班級(jí)：機(jī)械97 學(xué)生姓名：孫皓 課題（設(shè)計(jì)）名稱(chēng)：基于液壓夾緊的專(zhuān)用夾具設(shè)計(jì)支架 零件的工藝工裝設(shè)計(jì) 開(kāi)始日期：2013.11.12周次起止日期工作計(jì)劃、進(jìn)度每周主要完成內(nèi)容存在問(wèn)題、改進(jìn)方法指導(dǎo)教師意見(jiàn)并簽字備 注1-42012年11月12日-2012年12月10日教師下達(dá)畢業(yè)設(shè)計(jì)任務(wù)，學(xué)生初步閱讀資料，完成畢業(yè)設(shè)計(jì)開(kāi)題報(bào)告。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)存在問(wèn)題：對(duì)于實(shí)際操作不是很了解。改進(jìn)方法：參與工作，逐漸了解，參與其中。5-102012年12月11日-2013年1月24日指導(dǎo)專(zhuān)業(yè)實(shí)訓(xùn)掌握基本數(shù)控機(jī)床的操作存在問(wèn)題：發(fā)現(xiàn)自己欠缺很多動(dòng)手操作能力。改進(jìn)方法：多學(xué)，多問(wèn)，多動(dòng)手。10-112012年1月25日-3月4日指導(dǎo)畢業(yè)實(shí)習(xí)在企業(yè)里實(shí)習(xí)電氣檢測(cè)存在問(wèn)題：作為新手，一切都要從頭開(kāi)始學(xué)。改進(jìn)方法：多學(xué)，多問(wèn)，多動(dòng)手。122013年3月5日-3月9日填寫(xiě)畢業(yè)設(shè)計(jì)開(kāi)題報(bào)告填寫(xiě)畢業(yè)設(shè)計(jì)開(kāi)題報(bào)告存在問(wèn)題：對(duì)課題難易程度理解不夠，難點(diǎn)分析不足，分析能力欠缺，許多問(wèn)題不是很明白。改進(jìn)方法：在指導(dǎo)老師的幫助下，進(jìn)一步消化本課題。132013年3月10日-3月14日檢查畢業(yè)設(shè)計(jì)準(zhǔn)備情況修改完善畢業(yè)設(shè)計(jì)開(kāi)題報(bào)告存在問(wèn)題：對(duì)課題難點(diǎn)分析不足，分析能力欠缺，對(duì)課題理解不深，頭腦里沒(méi)設(shè)計(jì)的東西的概念改進(jìn)方法：在指導(dǎo)老師的幫助下，整改開(kāi)題報(bào)告。142012年2月27日-3月10日查閱參考資料查閱與設(shè)計(jì)有關(guān)的參考資料不少于10本，其中外文不少于2本存在問(wèn)題：由于工作原因，空閑時(shí)間很少，查閱資料太少。改進(jìn)方法：利用一切時(shí)間，去圖書(shū)館和網(wǎng)上查找相關(guān)資料152012年3月11日-3月15日工藝規(guī)程設(shè)計(jì)確定幾種工藝路線(xiàn)根據(jù)零件的功用分析，零件的幾何形狀、尺寸精度及位置精度等技術(shù)要求確定工藝路線(xiàn)存在問(wèn)題：缺乏實(shí)際操作經(jīng)驗(yàn)，制定的工藝方案不合理。改進(jìn)方法：多去咨詢(xún)老師了解實(shí)際生產(chǎn)過(guò)程，重新確立合理的工藝方案。162012年3月16日-3月20日整理、分析資料，比較各種設(shè)計(jì)方案查閱多種參考資料，結(jié)合課題比較設(shè)計(jì)方案存在問(wèn)題：夾具結(jié)構(gòu)設(shè)計(jì)不合理，尺寸計(jì)算有誤差公式運(yùn)用錯(cuò)誤。對(duì)夾具設(shè)計(jì)數(shù)據(jù)不了解改進(jìn)方法：查閱多種參考資料，改進(jìn)夾具結(jié)構(gòu)，提高計(jì)算正確率。172012年3月21日-3月25日改進(jìn)工藝路線(xiàn)在指導(dǎo)老師的幫助下，結(jié)合自己的實(shí)際完善工藝路線(xiàn)存在問(wèn)題：缺乏生產(chǎn)經(jīng)驗(yàn)，對(duì)夾具在實(shí)際中應(yīng)用改進(jìn)方法：多了解實(shí)際生產(chǎn)過(guò)程，重新確立合理的工藝方案。182013年3月26日-3月30日確定工藝路線(xiàn)進(jìn)行計(jì)算進(jìn)行參數(shù)計(jì)算及結(jié)構(gòu)分析存在問(wèn)題：對(duì)公式不熟悉改進(jìn)方法：查找相關(guān)資料書(shū)籍，回顧以前所有知識(shí)192013年4月2日-4月6日裝配圖初步繪制夾具裝配圖存在問(wèn)題：對(duì)CAD運(yùn)用不熟悉，畫(huà)圖速度較慢改進(jìn)方法：重新確定合理的表達(dá)視圖，多加運(yùn)用繪圖軟件，提高畫(huà)圖速度202013年4月9日-4月13日裝配圖修改夾具裝配圖存在問(wèn)題：2D裝配圖中部分標(biāo)準(zhǔn)件畫(huà)法不正確，尺寸不精確。改進(jìn)方法：按機(jī)械制圖要求改正不正確的畫(huà)法，修改尺寸。212013年4月16日-4月20日完成零件圖繪制模具零件圖，不少于5個(gè)存在問(wèn)題：零件圖的表達(dá)方案不合理，尺寸不符合實(shí)際需要，技術(shù)要求不規(guī)范。改進(jìn)方法：修改零件圖的表達(dá)方案，完善尺寸標(biāo)注和技術(shù)要求。222013年4月23日-4月30日說(shuō)明書(shū)完成設(shè)計(jì)說(shuō)明書(shū)存在問(wèn)題：說(shuō)明書(shū)的格式不規(guī)范，摘要不合理，關(guān)鍵詞不恰當(dāng)。改進(jìn)方法：根據(jù)說(shuō)明書(shū)規(guī)范要求更改，重新按要求編寫(xiě)摘要。232013年5月1日-5月7日摘要、小結(jié)完成摘要和小結(jié)存在問(wèn)題：說(shuō)明書(shū)的格式不規(guī)范，摘要不合理，關(guān)鍵詞不恰當(dāng)。改進(jìn)方法：根據(jù)說(shuō)明書(shū)規(guī)范要求更改，重新按要求編寫(xiě)摘要。242013年5月8日-5月19日檢查、指導(dǎo)設(shè)計(jì)說(shuō)明書(shū)、摘要和小結(jié)編寫(xiě)完成設(shè)計(jì)說(shuō)明書(shū)、摘要和小結(jié)存在問(wèn)題：說(shuō)明書(shū)的格式不規(guī)范，摘要不合理，關(guān)鍵詞不恰當(dāng)。改進(jìn)方法：根據(jù)說(shuō)明書(shū)規(guī)范要求更改，重新按要求編寫(xiě)摘要。252013年5月20日-5月25日上交資料、答辯整理所有資料上交指導(dǎo)教師，答辯資料整理欠合理，按學(xué)院要求整理并裝訂，進(jìn)行答辯 說(shuō)明：1、“工作計(jì)劃、進(jìn)度”、“指導(dǎo)教師意見(jiàn)并簽字”由指導(dǎo)教師填寫(xiě)，“每周主要完成內(nèi)容”，“存在問(wèn)題、改進(jìn)方法”由學(xué)生填寫(xiě)。2、本表由各系妥善歸檔，保存?zhèn)洳椤Ｖ艽纹鹬谷掌诠ぷ饔?jì)劃、進(jìn)度每周主要完成內(nèi)容存在問(wèn)題、改進(jìn)方法指導(dǎo)教師意見(jiàn)并簽字備 注編號(hào)
無(wú)錫太湖學(xué)院
畢業(yè)設(shè)計(jì)（論文）
相關(guān)資料
題目： 基于液壓夾緊的專(zhuān)用夾具設(shè)計(jì)
——支架零件的工藝工裝設(shè)計(jì)
信機(jī) 系 機(jī)械工程及自動(dòng)化專(zhuān)業(yè)
學(xué) 號(hào)： 0923816
學(xué)生姓名： 孫 皓
指導(dǎo)教師： 韓邦華 （職稱(chēng)：副教授 ）
（職稱(chēng)： ）
2013年5月25日
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
無(wú)錫太湖學(xué)院
畢業(yè)設(shè)計(jì)（論文）
開(kāi)題報(bào)告
題目： 基于液壓夾緊的專(zhuān)用夾具設(shè)計(jì)
——支架零件的工藝工裝設(shè)計(jì)
信機(jī) 系 機(jī)械工程及自動(dòng)化 專(zhuān)業(yè)
學(xué) 號(hào)： 0923816
學(xué)生姓名： 孫 皓
指導(dǎo)教師： 韓邦華 （職稱(chēng)：副教授 ）
（職稱(chēng)： ）
2012年11月24日
課題來(lái)源
無(wú)錫某企業(yè)生產(chǎn)實(shí)際
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
本課題是為了培養(yǎng)學(xué)生開(kāi)發(fā)和創(chuàng)新機(jī)械產(chǎn)品的能力，要求學(xué)生能夠結(jié)合零件加工工藝與常規(guī)普通銑床，針對(duì)在實(shí)際使用過(guò)程中存在的金屬加工機(jī)床的工件夾緊及驅(qū)動(dòng)問(wèn)題，綜合所學(xué)的機(jī)械理論設(shè)計(jì)與方法、氣動(dòng)與液壓傳動(dòng)等理論知識(shí)，對(duì)快速、高效夾緊裝置進(jìn)行改進(jìn)設(shè)計(jì)，進(jìn)而實(shí)現(xiàn)金屬加工機(jī)床的工件夾緊與驅(qū)動(dòng)的半自動(dòng)化控制。
2、國(guó)內(nèi)外研究概況及發(fā)展前景
夾具從產(chǎn)生到現(xiàn)在，大約可以分為三個(gè)階段：第一個(gè)階段主要表現(xiàn)在夾具與人的結(jié)合上，這是夾具主要是作為人的單純的輔助工具，是加工過(guò)程加速和趨于完善；第二階段，夾具成為人與機(jī)床之間的橋梁，夾具的機(jī)能發(fā)生變化，它主要用于工件的定位和夾緊。人們?cè)絹?lái)越認(rèn)識(shí)到，夾具與操作人員改進(jìn)工作及機(jī)床性能的提高有著密切的關(guān)系，所以對(duì)夾具引起了重視；第三階段表現(xiàn)為夾具與機(jī)床的結(jié)合，夾具作為機(jī)床的一部分，成為機(jī)械加工中不可缺少的工藝裝備。
在夾具設(shè)計(jì)過(guò)程中，對(duì)于被加工零件的定位、夾緊等主要問(wèn)題,設(shè)計(jì)人員一般都會(huì)考慮的比較周全，但是，夾具設(shè)計(jì)還經(jīng)常會(huì)遇到一些小問(wèn)題，這些小問(wèn)題如果處理不好，也會(huì)給夾具的使用造成許多不便，甚至?xí)绊懙焦ぜ募庸ぞ?。我們把多年?lái)在夾具設(shè)計(jì)中遇到的一些小問(wèn)題歸納如下：清根問(wèn)題在設(shè)計(jì)端面和內(nèi)孔定位的夾具時(shí)，會(huì)遇到夾具體定位端面和定位外圓交界處清根問(wèn)題。端面和定位外圓分為兩體時(shí)無(wú)此問(wèn)題,。夾具要不要清根，應(yīng)根據(jù)工件的結(jié)構(gòu)而定。如果零件定位內(nèi)孔孔口倒角較小或無(wú)倒角，則必須清根,如果零件定位孔孔口倒角較大或孔口是空位，則不需要清根，而且交界處可以倒為圓角R。端面與外圓定位時(shí)，與上述相同。讓刀問(wèn)題在設(shè)計(jì)圓盤(pán)類(lèi)刀具(如銑刀、砂輪等)加工的夾具時(shí)，會(huì)存在讓刀問(wèn)題。設(shè)計(jì)這類(lèi)夾具時(shí)，應(yīng)考慮銑刀或砂輪完成切削或磨削后，銑刀或砂輪的退刀位置，其位置大小應(yīng)根據(jù)所使用的銑刀或砂輪的直徑大小，留出超過(guò)刀具半徑的尺寸位置即可。更換問(wèn)題在設(shè)計(jì)加工結(jié)構(gòu)相同或相似，尺寸不同的系列產(chǎn)品零件夾具時(shí)，為了降低生產(chǎn)成本,提高夾具的利用率，往往會(huì)把夾具設(shè)計(jì)為只更換某一個(gè)或幾個(gè)零件的通用型夾具。
由于現(xiàn)代加工的高速發(fā)展，對(duì)傳統(tǒng)的夾具提出了較高要求，如快速、高效、安全等?；谝簤簥A緊的專(zhuān)用夾具設(shè)計(jì)，必須計(jì)算加工工序所受的切削力及切削力矩，按照夾緊方式進(jìn)行夾緊力的計(jì)算，進(jìn)而可以確定液壓缸的負(fù)載，通過(guò)選定整個(gè)液壓系統(tǒng)的壓力，最終可以確定液壓缸的各參數(shù)。
隨著機(jī)械工業(yè)的迅速發(fā)展，對(duì)產(chǎn)品的品種和生產(chǎn)率提出了愈來(lái)愈高的要求，使多品種，中小批生產(chǎn)作為機(jī)械生產(chǎn)的主流，為了適應(yīng)機(jī)械生產(chǎn)的這種發(fā)展趨勢(shì)，必然對(duì)機(jī)床夾具提出更高的要求。特別像后鋼板彈簧吊耳類(lèi)不規(guī)則零件的加工還處于落后階段。在今后的發(fā)展過(guò)程中，應(yīng)大力推廣使用組合夾具、半組合夾具、可調(diào)夾具，尤其是成組夾具。在機(jī)床技術(shù)向高速、高效、精密、復(fù)合、智能、環(huán)保方向發(fā)展的帶動(dòng)下，夾具技術(shù)正朝著高精高效模塊組合通用經(jīng)濟(jì)方向發(fā)展。
研究?jī)?nèi)容
通過(guò)實(shí)際調(diào)研和采集相對(duì)應(yīng)的設(shè)計(jì)數(shù)據(jù)，分析金屬切削加工過(guò)程中的機(jī)床工作臺(tái)工件夾緊、驅(qū)動(dòng)等方面的有關(guān)數(shù)據(jù)，再結(jié)合氣動(dòng)與液壓傳動(dòng)的相關(guān)理論知識(shí)，完成液壓夾緊傳動(dòng)方案分析及氣壓原理圖的擬定，并進(jìn)行主要功能元件的設(shè)計(jì)與選擇及傳動(dòng)系統(tǒng)的驗(yàn)算校核等。
擬采取的研究方法、技術(shù)路線(xiàn)、實(shí)驗(yàn)方案及可行性分析
通過(guò)實(shí)踐與大量搜集、閱讀相關(guān)資料相結(jié)合，在對(duì)金屬切削機(jī)床、金屬切削加工、機(jī)械設(shè)計(jì)與理論及氣動(dòng)與液壓傳動(dòng)等相關(guān)知識(shí)充分掌握后，對(duì)普通銑床的夾緊、驅(qū)動(dòng)裝置進(jìn)行數(shù)學(xué)建模，并通過(guò)模擬實(shí)驗(yàn)分析建立普通銑床的驅(qū)動(dòng)、夾緊裝置的實(shí)體模型，設(shè)計(jì)液壓專(zhuān)用夾具的驅(qū)動(dòng)、夾緊裝置，進(jìn)行現(xiàn)場(chǎng)實(shí)驗(yàn)，以達(dá)到產(chǎn)品的最優(yōu)化設(shè)計(jì)。
研究計(jì)劃及預(yù)期成果
研究計(jì)劃：
2013年1月12日-2013年02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30日-2013年03月05日：填寫(xiě)畢業(yè)實(shí)習(xí)報(bào)告。
2013年3月08日-2013年03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03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04月28日：液壓夾具設(shè)計(jì)。
2013年4月29日-2013年05月21日：畢業(yè)論文撰寫(xiě)和修改工作。
預(yù)期成果：
通過(guò)現(xiàn)場(chǎng)調(diào)研、模擬、建模、實(shí)驗(yàn)、機(jī)器調(diào)試，達(dá)到產(chǎn)品的最優(yōu)化設(shè)計(jì)，大大降低勞動(dòng)強(qiáng)度和提高生產(chǎn)效率。
在設(shè)計(jì)液壓系統(tǒng)裝置時(shí)，在滿(mǎn)足產(chǎn)品工作要求的情況下，應(yīng)盡可能多的采用標(biāo)準(zhǔn)件，提高其互換性要求，以減少產(chǎn)品的設(shè)計(jì)生產(chǎn)成本。
特色或創(chuàng)新之處
適用于現(xiàn)代加工企業(yè)安全、高效的液壓夾具設(shè)計(jì)、夾緊裝置的優(yōu)化設(shè)計(jì)，可減少工人的勞動(dòng)強(qiáng)度、降低機(jī)械加工工藝時(shí)間和機(jī)械零件的生產(chǎn)成本。
已具備的條件和尚需解決的問(wèn)題
針對(duì)實(shí)際使用過(guò)程中存在的金屬加工工藝文件編制、工件夾緊及快速、高效夾具設(shè)計(jì)問(wèn)題，綜合所學(xué)的機(jī)械理論設(shè)計(jì)與方法與液壓與氣動(dòng)傳動(dòng)等方面的知識(shí)，實(shí)現(xiàn)適合于現(xiàn)代加工制造業(yè)、夾緊裝置的優(yōu)化設(shè)計(jì)，進(jìn)而提高學(xué)生開(kāi)發(fā)和創(chuàng)新機(jī)械產(chǎn)品的能力。
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
Basic Machining Operations and Cutting Technology
Machine tools have evolved from the early foot-powered lathes of the Egyptians and John Wilkinson's boring mill. They are designed to provide rigid support for both the workpiece and the cutting tool and can precisely control their relative positions and the velocity of the tool with respect to the workpiece. Basically, in metal cutting, a sharpened wedge-shaped tool removes a rather narrow strip of metal from the surface of a ductile workpiece in the form of a severely deformed chip. The chip is a waste product that is considerably shorter than the workpiece from which it came but with a corresponding increase in thickness of the uncut chip. The geometrical shape of workpiece depends on the shape of the tool and its path during the machining operation.
Most machining operations produce parts of differing geometry. If a rough cylindrical workpiece revolves about a central axis and the tool penetrates beneath its surface and travels parallel to the center of rotation, a surface of revolution is produced, and the operation is called turning. If a hollow tube is machined on the inside in a similar manner, the operation is called boring. Producing an external conical surface uniformly varying diameter is called taper turning. If the tool point travels in a path of varying radius, a contoured surface like that of a bowling pin can be produced; or, if the piece is short enough and the support is sufficiently rigid, a contoured surface could be produced by feeding a shaped tool normal to the axis of rotation. Short tapered or cylindrical surfaces could also be contour formed.
Multiple-edged tools can also be used. Drilling uses a twin-edged fluted tool for holes with depths up to 5 to 10 times the drill diameter. Whether the drill turns or the workpiece rotates, relative motion between the cutting edge and the workpiece is the important factor. In milling operations a rotary cutter with a number of cutting edges engages the workpiece, which moves slowly with respect to the cutter. Plane or contoured surfaces may be produced, depending on the geometry of the cutter and the type of feed. Horizontal or vertical axes of rotation may be used, and the feed of the workpiece may be in any of the three coordinate directions.
Introduction of Machining
Machining as a shape-producing method is the most universally used and the most important of all manufacturing processes. Machining is a shape-producing process in which a power-driven device causes material to be removed in chip form. Most machining is done with equipment that supports both the work piece and cutting tool although in some cases portable equipment is used with unsupported workpiece.
Low setup cost for small Quantities. Machining has two applications in manufacturing. For casting, forging, and press working, each specific shape to be produced, even one part, nearly always has a high tooling cost. The shapes that may be produced by welding depend to a large degree on the shapes of raw material that are available. By making use of generally high cost equipment but without special tooling, it is possible, by machining; to start with nearly any form of raw material, so long as the exterior dimensions are great enough, and produce any desired shape from any material. Therefore .machining is usually the preferred method for producing one or a few parts, even when the design of the part would logically lead to casting, forging or press working if a high quantity were to be produced.
Close accuracies, good finishes. The second application for machining is based on the high accuracies and surface finishes possible. Many of the parts machined in low quantities would be produced with lower but acceptable tolerances if produced in high quantities by some other process. On the other hand, many parts are given their general shapes by some high quantity deformation process and machined only on selected surfaces where high accuracies are needed. Internal threads, for example, are seldom produced by any means other than machining and small holes in press worked parts may be machined following the press working operations.
Primary Cutting Parameters
The basic tool-work relationship in cutting is adequately described by means of four factors: tool geometry, cutting speed, feed, and depth of cut.
The cutting tool must be made of an appropriate material; it must be strong, tough, hard, and wear resistant. The tool s geometry characterized by planes and angles, must be correct for each cutting operation. Cutting speed is the rate at which the work surface passes by the cutting edge. It may be expressed in feet per minute.
For efficient machining the cutting speed must be of a magnitude appropriate to the particular work-tool combination. In general, the harder the work material, the slower the speed.
Feed is the rate at which the cutting tool advances into the workpiece. Where the workpiece or the tool rotates, feed is measured in inches per revolution. When the tool or the work reciprocates, feed is measured in inches per stroke, Generally, feed varies inversely with cutting speed for otherwise similar conditions.
The depth of cut, measured inches is the distance the tool is set into the work. It is the width of the chip in turning or the thickness of the chip in a rectilinear cut. In roughing operations, the depth of cut can be larger than for finishing operations.
The Effect of Changes in Cutting Parameters on Cutting Temperatures
In metal cutting operations heat is generated in the primary and secondary deformation zones and these results in a complex temperature distribution throughout the tool, workpiece and chip. A typical set of isotherms is shown in figure where it can be seen that, as could be expected, there is a very large temperature gradient throughout the width of the chip as the workpiece material is sheared in primary deformation and there is a further large temperature in the chip adjacent to the face as the chip is sheared in secondary deformation. This leads to a maximum cutting temperature a short distance up the face from the cutting edge and a small distance into the chip.
Since virtually all the work done in metal cutting is converted into heat, it could be expected that factors which increase the power consumed per unit volume of metal removed will increase the cutting temperature. Thus an increase in the rake angle, all other parameters remaining constant, will reduce the power per unit volume of metal removed and the cutting temperatures will reduce. When considering increase in unreformed chip thickness and cutting speed the situation is more complex. An increase in undeformed chip thickness tends to be a scale effect where the amounts of heat which pass to the workpiece, the tool and chip remain in fixed proportions and the changes in cutting temperature tend to be small. Increase in cutting speed; however, reduce the amount of heat which passes into the workpiece and this increase the temperature rise of the chip m primary deformation. Further, the secondary deformation zone tends to be smaller and this has the effect of increasing the temperatures in this zone. Other changes in cutting parameters have virtually no effect on the power consumed per unit volume of metal removed and consequently have virtually no effect on the cutting temperatures. Since it has been shown that even small changes in cutting temperature have a significant effect on tool wear rate it is appropriate to indicate how cutting temperatures can be assessed from cutting data.
The most direct and accurate method for measuring temperatures in high -speed-steel cutting tools is that of Wright & Trent, which also yields detailed information on temperature distributions in high-speed-steel cutting tools. The technique is based on the metallographic examination of sectioned high-speed-steel tools which relates microstructure changes to thermal history.
Trent has described measurements of cutting temperatures and temperature ?distributions for high-speed-steel tools when machining a wide range of workpiece materials. This technique has been further developed by using scanning electron ?microscopy to study fine-scale microstructure changes arising from over tempering of the tempered martens tic matrix of various high-speed-steels. This technique has also been used to study temperature distributions in both high-speed -steel single point turning tools and twist drills.
Wears of Cutting Tool
Discounting brittle fracture and edge chipping, which have already been dealt with, tool wear is basically of three types. Flank wear, crater wear, and notch wear. Flank wear occurs on both the major and the minor cutting edges. On the major cutting edge, which is responsible for bulk metal removal, these results in increased cutting forces and higher temperatures which if left unchecked can lead to vibration of the tool and workpiece and a condition where efficient cutting can no longer take place. On the minor cutting edge, which determines workpiece size and surface finish, flank wear can result in an oversized product which has poor surface finish. Under most practical cutting conditions, the tool will fail due to major flank wear before the minor flank wear is sufficiently large to result in the manufacture of an unacceptable component.
Because of the stress distribution on the tool face, the frictional stress in the region of sliding contact between the chip and the face is at a maximum at the start of the sliding contact region and is zero at the end. Thus abrasive wear takes place in this region with more wear taking place adjacent to the seizure region than adjacent to the point at which the chip loses contact with the face.
This result in localized pitting of the tool face some distance up the face which is usually referred to as catering and which normally has a section in the form of a circular arc. In many respects and for practical cutting conditions, crater wear is a less severe form of wear than flank wear and consequently flank wear is a more common tool failure criterion. However, since various authors have shown that the temperature on the face increases more rapidly with increasing cutting speed than the temperature on the flank, and since the rate of wear of any type is significantly affected by changes in temperature, crater wear usually occurs at high cutting speeds.
At the end of the major flank wear land where the tool is in contact with the uncut workpiece surface it is common for the flank wear to be more pronounced than along the rest of the wear land. This is because of localised effects such as a hardened layer on the uncut surface caused by work hardening introduced by a previous cut, an oxide scale, and localised high temperatures resulting from the edge effect. This localised wear is usually referred to as notch wear and occasionally is very severe. Although the presence of the notch will not significantly affect the cutting properties of the tool, the notch is often relatively deep and if cutting were to continue there would be a good chance that the tool would fracture.
If any form of progressive wear allowed to continue, dramatically and the tool would fail catastrophically, i. e. the tool would be no longer capable of cutting and, at best, the workpiece would be scrapped whilst, at worst, damage could be caused to the machine tool. For carbide cutting tools and for all types of wear, the tool is said to have reached the end of its useful life long before the onset of catastrophic failure. For high-speed-steel cutting tools, however, where the wear tends to be non-uniform it has been found that the most meaningful and reproducible results can be obtained when the wear is allowed to continue to the onset of catastrophic failure even though, of course, in practice a cutting time far less than that to failure would be used. The onset of catastrophic failure is characterized by one of several phenomena, the most common being a sudden increase in cutting force, the presence of burnished rings on the workpiece, and a significant increase in the noise level.
Mechanism of Surface Finish Production
There are basically five mechanisms which contribute to the production of a surface which have been machined. These are:
(l) The basic geometry of the cutting process. In, for example, single point turning the tool will advance a constant distance axially per revolution of the workpiecc and the resultant surface will have on it, when viewed perpendicularly to the direction of tool feed motion, a series of cusps which will have a basic form which replicates the shape of the tool in cut.
(2) The efficiency of the cutting operation. It has already been mentioned that cutting with unstable built-up-edges will produce a surface which contains hard built-up-edge fragments which will result in a degradation of the surface finish. It can also be demonstrated that cutting under adverse conditions such as apply when using large feeds small rake angles and low cutting speeds, besides producing conditions which lead to unstable built-up-edge production, the cutting process itself can become unstable and instead of continuous shear occurring in the shear zone, tearing takes place, discontinuous chips of uneven thickness are produced, and the resultant surface is poor. This situation is particularly noticeable when machining very ductile materials such as copper and aluminum.
(3) The stability of the machine tool. Under some combinations of cutting conditions; workpiece size, method of clamping ,and cutting tool rigidity relative to the machine tool structure, instability can be set up in the tool which causes it to vibrate. Under some conditions this vibration will reach and maintain steady amplitude whilst under other conditions the vibration will built up and unless cutting is stopped considerable damage to both the cutting tool and workpiece may occur. This phenomenon is known as chatter and in axial turning is characterized by long pitch helical bands on the workpiece surface and short pitch undulations on the transient machined surface.
(4)The effectiveness of removing swarf. In discontinuous chip production machining, such as milling or turning of brittle materials, it is expected that the chip (swarf) will leave the cutting zone either under gravity or with the assistance of a jet of cutting fluid and that they will not influence the cut surface in any way. However, when continuous chip production is evident, unless steps are taken to control the swarf it is likely that it will impinge on the cut surface and mark it. Inevitably, this marking besides looking.
(5)The effective clearance angle on the cutting tool. For certain geometries of minor cutting edge relief and clearance angles it is possible to cut on the major cutting edge and burnish on the minor cutting edge. This can produce a good surface finish but, of course, it is strictly a combination of metal cutting and metal forming and is not to be recommended as a practical cutting method. However, due to cutting tool wear, these conditions occasionally arise and lead to a marked change in the surface characteristics.
Surface Finishing and Dimensional Control
Products that have been completed to their proper shape and size frequently require some type of surface finishing to enable them to satisfactorily fulfill their function. In some cases, it is necessary to improve the physical properties of the surface material for resistance to penetration or abrasion. In many manufacturing processes, the product surface is left with dirt .chips, grease, or other harmful material upon it. Assemblies that are made of different materials, or from the same materials processed in different manners, may require some special surface treatment to provide uniformity of appearance.
Surface finishing may sometimes become an intermediate step processing. For instance, cleaning and polishing are usually essential before any kind of plating process. Some of the cleaning procedures are also used for improving surface smoothness on mating parts and for removing burrs and sharp corners, which might be harmful in later use. Another important need for surface finishing is for corrosion protection in a variety of: environments. The type of protection procedure will depend largely upon the anticipated exposure, with due consideration to the material being protected and the economic factors involved.
Satisfying the above objectives necessitates the use of main surface-finishing methods that involve chemical change of the surface mechanical work affecting surface properties, cleaning by a variety of methods, and the application