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缸體機(jī)械加工工藝設(shè)計(jì)
發(fā)動機(jī)缸體是發(fā)動機(jī)零件中結(jié)構(gòu)較為復(fù)雜的箱體零件，其精度要求高，加工工藝復(fù)雜，并且加工加工質(zhì)量的好壞直接影響發(fā)動機(jī)整個(gè)機(jī)構(gòu)的性能，因此，它成為各個(gè)發(fā)動機(jī)生產(chǎn)廠家所關(guān)注的重點(diǎn)零件之一。
1. 發(fā)動機(jī)缸體的工藝特點(diǎn)
缸體為一整體鑄造結(jié)構(gòu)，其上部有4個(gè)缸套安裝孔；缸體的水平隔板將缸體分成上下兩部分；缸體的前端面從到后排列有三個(gè)同軸線的凸輪軸安裝孔和惰輪軸孔。
2. 發(fā)動機(jī)缸體工藝方案設(shè)計(jì)原則和依據(jù)
設(shè)計(jì)工藝方案應(yīng)在保證產(chǎn)品質(zhì)量的同時(shí)，充分考慮生產(chǎn)周期、成本和環(huán)境保護(hù)；根據(jù)本企業(yè)能力，積極采用國內(nèi)外先進(jìn)的工藝技術(shù)和裝備，不斷提高企業(yè)工藝水平。發(fā)動機(jī)缸體機(jī)械加工工藝設(shè)計(jì)應(yīng)遵循以下基本原則：
（1）加工設(shè)備選型原則 加工設(shè)備選型采用剛?cè)峤Y(jié)合的原則，加工設(shè)備以臥式加工中心為主，少量采用立式加工中心，關(guān)鍵工序—曲軸孔、缸孔、平衡軸孔加工采用高精度高速臥式加工中心，非關(guān)鍵工序—上下前后四個(gè)平面的粗銑采用高效并有一定調(diào)整范圍的專用機(jī)床加工；
（2）集中工序原則 關(guān)鍵工序—曲軸孔、缸孔、平衡軸孔的精加工缸蓋結(jié)合面的精銑，采用在集中在一道工序一次裝夾完成全部加工內(nèi)容方案，以確保產(chǎn)品精度滿足缸體關(guān)鍵品質(zhì)的工藝性能和有關(guān)技術(shù)要求。
根據(jù)汽車發(fā)動機(jī)缸體的工藝特點(diǎn)和生產(chǎn)任務(wù)要求，發(fā)動機(jī)缸體機(jī)械加工自動生產(chǎn)線由臥式加工中心CWK500和CWK500D加工中心、專用銑/鏜床、立式加工中心matec-30L等設(shè)備組成。
3. 發(fā)動機(jī)缸體機(jī)械加工工藝設(shè)計(jì)的主要內(nèi)容
發(fā)動機(jī)缸體結(jié)構(gòu)復(fù)雜，精度要求高，尺寸較大，是薄壁零件，有若干精度要求較高的平面和孔。發(fā)動機(jī)缸體機(jī)械加工的工藝特點(diǎn)是：主要是平面和孔的加工，加工平面一般采用刨、銑削等方法加工，加工孔主要采用鏜削，加工小孔多用鉆削。由于缸體結(jié)構(gòu)復(fù)雜，因此如何保證各表面的相互位置精度是加工中的一個(gè)重要問題。
3.1 毛坯的選擇
發(fā)動機(jī)缸體采用的材料一般是灰鑄鐵HT150、HT200、HT250，也有采用鑄鋁或者鋼板的，此發(fā)動機(jī)缸體采用高強(qiáng)度合金鑄鐵。缸體在加工前進(jìn)行時(shí)效處理，以消除鑄件內(nèi)應(yīng)力和改善毛坯的力學(xué)性能。
提高毛坯精度，減少加工余量，是提高自動生產(chǎn)線系統(tǒng)生產(chǎn)率及加工質(zhì)量的重要措施。由于國外箱體類零件毛坯質(zhì)量和精度較高，其生產(chǎn)線系統(tǒng)已實(shí)現(xiàn)了毛坯直接上線，既省去了毛坯檢查裝置，也節(jié)省了由于毛坯質(zhì)量問題而浪費(fèi)的加工工時(shí)，提高了綜合效益。因此，精化毛坯是提高生產(chǎn)率最有潛力的出路。對于發(fā)動機(jī)缸體生產(chǎn)線，可在零件上線前粗銑六個(gè)面，去除大部分余量，便于零件直接上線。
3.2機(jī)械加工工藝基準(zhǔn)的選擇和加工
選擇合理的加工工藝基準(zhǔn)，直接關(guān)系到能否保證零件的加工質(zhì)量。一般來說，工藝基準(zhǔn)可分為粗基準(zhǔn)和精基準(zhǔn)。
（1）粗基準(zhǔn)對于上線的毛坯，其粗基準(zhǔn)的選擇尤為重要，如果粗基準(zhǔn)選擇不合理，會使加工余量分布不均勻，加工面偏移，造成廢品。在缸體生產(chǎn)線中，我們采用側(cè)面作為粗基準(zhǔn)；
（2）粗基準(zhǔn)對于發(fā)動機(jī)缸體這種箱體零件來說，一般采用“一面兩銷”為全線的統(tǒng)一基準(zhǔn)。對于較長的自動自動生產(chǎn)線系統(tǒng)，由于定位銷孔在使用過程中的磨損造成定位不準(zhǔn)確，因此，將定位銷孔分為2-3段使用。在缸體定位銷孔的加工中，我們采用了以側(cè)面、底面和主軸孔定位，在加工中心上加工。
3.3 機(jī)械加工加工階段的劃分和工序的安排
一個(gè)零件往往有許多表面需要加工，當(dāng)然表面的加工精度是不同的。加工精度較高的表面，往往要經(jīng)過多次加工；而對于加工精度低的表面，只要經(jīng)過一兩次就行了。因此，擬定工藝順序時(shí)，要抓住“加工精度高的表面”這個(gè)矛盾，合理安排工序和合理劃分加工階段。安排工藝順序的原則是：先粗后精，先面后孔，先基準(zhǔn)后其他。在發(fā)動機(jī)缸體的機(jī)械加工中同樣應(yīng)遵循這一原則。
（1）粗加工階段 在發(fā)動機(jī)缸體的機(jī)械加工過程中，安排粗加工工序，對毛坯全面進(jìn)行粗加工，切去大部分余量，以保證生產(chǎn)效率；
（2）半精加工階段 在發(fā)動機(jī)缸體的機(jī)械加工過程中，為了保證一些重要表面的加工精度，安排一些半精加工工序，將精度和表面粗造度要求中等的一些表面加工完成，而對要求高的表面進(jìn)行半精加工，為以后的精加工做準(zhǔn)備；
3.4 缸體的主要加工表面和輔助工序
缸體主要加工表面和輔助工序有：
（1）平面加工 目前，銑削是發(fā)動機(jī)缸體平面加工的主要手段，國內(nèi)銑削進(jìn)給量一般為300-400mm/min，與國外銑削進(jìn)給量2000-4000 mm/min相比，相差甚遠(yuǎn)，有待于提高，因此，提高銑削進(jìn)給量，縮短輔助時(shí)間，是提高生產(chǎn)效率的主要途徑，發(fā)動機(jī)缸體精加工一些平面時(shí)的銑削進(jìn)給量達(dá)到2399mm/min，大大提高了效率；
頂面的銑削是缸體加工中的一個(gè)關(guān)鍵工序，其平面度要求為0.02/145mm，表面粗造度為Ra1.6um。在缸體的加工中，采用側(cè)面和主軸軸承孔定位，頂面、底面和中間瓦蓋面同時(shí)加工，在加工中采用線外對刀裝置，能較好地滿足發(fā)動機(jī)缸體加工精度要求；
（2）一般孔系的加工 一般孔系的加工仍采用傳統(tǒng)的鉆、擴(kuò)、鏜、鉸、攻絲等工藝方法。課題在設(shè)計(jì)具體的工藝方案時(shí)，采用涂層刀具、內(nèi)冷卻刀具等先進(jìn)刀具，采用大流量冷卻系統(tǒng)，大大提高了切削速度，提高了生產(chǎn)率；
（3）深油孔加工 傳統(tǒng)的加工方法是采用麻花鉆進(jìn)行分級進(jìn)給，其生產(chǎn)效率低，加工質(zhì)量差。在發(fā)動機(jī)缸體深油孔的加工中，采用槍鉆工藝；
4. 小結(jié)
通過對發(fā)動機(jī)缸體的結(jié)構(gòu)和工藝特點(diǎn)進(jìn)行分析，論述了發(fā)動機(jī)缸體機(jī)械加工工藝方案的原則和依據(jù)以及切削用量的選擇，并以高速銑削和調(diào)頭鏜孔為例，設(shè)計(jì)、分析了發(fā)動機(jī)缸體的高速銑削和調(diào)頭鏜孔工藝過程，及在加工中需要注意的問題。
Cylinder block machining process design
Engine parts engine block is a more complex structure of spare parts box, its high precision, complex process, and the processing quality will affect the overall performance engine, so it has become the engine manufacturer's focus parts one.
1. Technical Characteristics of the engine cylinder block
Cylinder cast for a whole structure, and its upper part 4 cylinder mounting hole; cylinder standard cylinder is divided into upper and lower divisions into two parts; cylinder to the rear of the front-side arrangement of the previous three coaxial mounting hole of the camshaft and the idler axle hole.
Engine block process design principles and the basis for
Design Technology program should be to ensure product quality at the same time, give full consideration to the production cycle, cost and environmental protection; based on the enterprises ability to actively adopt advanced process technology and equipment, and constantly enhance their level of technology. Engine block machining process design should follow the following basic principles:
(1) The selection of processing equipment ,the principle of selection adopted the principle of selection adopted the principle of combining rigid-flexible, processing each horizontal machining center is located mainly small operations with vertical machining center, the key process a crank hole, cylinder hole, balancer shaft hole High-speed processing of high-precision horizontal machining center, an upper and lower non-critical processes before and after the four-dimensional high-efficiency rough milling and have a certain adjustment range of special machine processing;
(2) focus on a key process in principle process the body cylinder bore, crankshaft hole, Balance Shaft hole surface finishing and the combination of precision milling cylinder head, using a process focused on a setup program to complete all processing elements in order to ensure product accuracy The key quality processes to meet the cylinder capacity and the relevant technical requirements;
According to the technological characteristics of automobile engine cylinder block and the production mandate, the engine block machining automatic production line is composed of horizontal machining center CWK500 and CWK500D machining centers, special milling/boring machine, vertical machining centers matec-30L and other appliances.
2. Engine block machining process design the main content
Engine block complex structure, high precision, arge size, is thin-walled parts, there are a number of high precision plane and holes. Engine block machining process characteristics; mainly flat and the hole processing, processing of flat generally use planing, milling methods such as processing, processing of hole used mainly boring, processing and multi-purpose drilling holes. As the cylinder complex structure. so how to ensure that the mutual position of the surface processing precision is an important issue.
3.1 The selection of blank
Engine block on the materials used are generally gray cast iron HT150,HT200,HT250,there is also cast aluminum or steel plate, this engine block using high-strength alloy cast iron. Cylinder in the processing prior to aging treatment in order to eliminate stress and improve the rough casting mechanical properties.
Improve the rough accuracy, reduction of machining allowance, is to improve the automated production line system productivity and processing quality of the important measures. As the foreign box-type parts of rough quality and high precision, and its production-line system has been implemented directly on the blank line, not only eliminating the need for blank check device also saves the rough quality problems due to waste of machining time, increase overall efficiency. Therefore, the refinement of rough is to improve the productivity of the most promising way out. For the engine block production line, can be rough in parts on-line pre-milling six face, removing most of the margin, to facilitate direct on-line parts.
3.2 Machining process selection and processing of the benchmark
Choose the right processing technology base is directly related to the processing quality can ensure the parts. Generally speaking, process benchmarking can be divided into coarse and fine reference base.
(1) The baseline for the on-line thick rough, which is particularly important the choice of benchmark crude, if crude benchmark choice unreasonable, will the uneven distribution of machining allowance, processing and surface offsets, resulting in waste. In the cylinder production line, we have adopted for the coarse side of the base;
(2) Refined the base of this box for the engine block parts, the general use of "side two sales "for a full range of uniform benchmarks, For the longer automated production positioning, therefore, will be divided into 2-3 segment pin holes used. In the cylinder pin hole of the process, we have adopted to the side, bottom and the spindle hole positioning, in the processing center on the process.
3.3 Machining Processing Stages and processes of the arrangements
Often a part of many apparent need for processing, of course, the surface machining accuracy are different. Processing of high precision surface, often after repeated processing; As for the processing of the surface of low precision, only need to go through one or two on the list. Thus, when the development process in order to seize the "processing high precision surface, "this conflict, the reasonable arrangement processes and rational division stage of processing. Arrange the order of the principle of process is: after the first coarse refined, the first surface after the hole, the first benchmark other. In the engine block machining, the same should follow this principle.
(1) roughing stage engine block machining process, the arrangements for roughing process, to fully carry out rough rough, trim most of the margin in order to ensure production efficiency;
(2) semi-finishing phase of the engine block machining, in order to ensure the accuracy of the middle of some important surface processing, and arrange some semi-finishing operations, will be required accuracy and surface roughness of the surface of the middle of some processing to complete, while demanding the surface of semi-finished, to prepare for future finishing;
3.4 cylinder surface of the main processing and secondary processes
Cylinder surface and support the main processing operations are:
(1) plane processing at present, the milling of engine blocks is the primary means of planar processing,domestic milling feed rate is generally 300-400mm/min,and foreign 2000-4000mm/min milling feed rate compared to far cry,to be on increasing,therefore,improve the milling feed rate,reduce overhead time is to improve the productivity of the major means of finishing a number of plane engine block when the milling feed rate to reach 2399mm/min,greatly improved efficiency;
Top surface of the cylinder milling is a key process in the process,the flatness requirements for 0.02/145mm,the surface roughness of Ra1.6um.Processing in the cylinder,the use of side and spindle bearing bore positioning,top,bottom and middle vagay only aperture while processing used in the processing line outside of the knife device can better meet the engine block machining accuracy;
(2) General holes machining holes in general are still using the traditional processing of drilling,expansion,boring,reaming,tapping and other craft approach. Issues in the design process of specific programs,use of coated cutting tools,cutting tools and other advanced tools within the cooling,and using a large flow of cooling systems,greatly improving the cutting speed,improved productivity;
3. Summary
Through the engine block of the structure and process characteristics of the analysis,discusses the engine block machining process design principles and basis of the choice of cutting parameters,and U-turn at high speed milling and boring,for example,design,analysis of the engine cylinder body of high-speed milling and turnover boring process,and in the processing need to pay attention to.