二級圓柱齒輪減速器及鏜孔工序夾具設計(含CAD圖紙+文檔)
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外文資料
Introduction of Machining Process
As a method of shape generation, mechanical processing is the most common and important method in all manufacturing processes. Machining process is a process of generating shape. In this process, the driving device makes some materials on the workpiece be removed in the form of chips. Although in some cases, the workpiece can not bear the situation, the use of mobile equipment to achieve processing, but most of the mechanical processing is through both supporting the workpiece and supporting tool equipment to complete. There are two aspects in the process of knowledge processing. Small batch production costs less. For casting, forging and pressure processing, every specific shape of the workpiece to be produced, even a part, almost costs a lot of processing costs. The structural shape produced by welding depends to a large extent on the form of effective raw materials. Generally speaking, through the use of valuable equipment without special processing conditions, almost any kind of raw materials can be started, with the aid of mechanical processing to process raw materials into any required structural shape, as long as the external size is large enough, that is possible. Therefore, for the production of a part, even when the structure of the part and the batch size to be produced are suitable for casting, forging or pressure processing, but usually mechanical processing is preferred. Rigorous accuracy and good surface finish, the second use of mechanical processing is based on high accuracy and possible surface finish. Many parts, if produced in large quantities by other means, are produced in small quantities with low tolerances and satisfying requirements in mechanical processing. On the other hand, many parts improve their general surface shape by rough processing technology, but only in the need for high precision and selected surface to be machined. For example, the internal thread, in addition to mechanical processing, almost no other processing methods can be processed. If the forged workpiece on the small hole processing, is also forged immediately after the completion of mechanical processing.
1.Basic Machining Parameters
The basic relationship between workpiece and tool in cutting is fully described by the following four factors: the geometry of tool, cutting speed, feed speed and back feed. Cutting tools must be made of a suitable material. They must be strong, tough, hard and wear-resistant. The geometric shape of the tool is characterized by the plane of the tool tip and the angle of the tool. It must be correct for every cutting process. Cutting speed is the rate at which the cutting edge passes through the surface of the workpiece. It is expressed in inches per minute. In order to process effectively, the cutting speed must be adapted to the matching of specific workpiece and cutting tool. Generally speaking, the harder the workpiece material is, the lower the speed is. Feed speed is the speed at which the tool cuts into the workpiece. If the workpiece or tool rotates, the feed is measured in inches per turn. When the cutter or workpiece moves back and forth, the feed is measured in inches per stroke. Generally speaking, when other conditions are the same, the feed rate is inversely proportional to the cutting speed. Back feed is measured in inches as the distance the tool enters the workpiece. It is equal to the chip width in rotary cutting or the chip thickness in linear cutting. Rough processing is deeper than finishing.
2.Tool Wear
From the numerous brittle cracks and edge cracks that have been treated, there are basically three types of tool wear: flank wear, rake wear and V-notch wear. The wear of flank occurs on both the main blade and the auxiliary blade. As for the main cutting edge, because it undertakes the task of cutting most metal chips, it leads to increasing cutting force and increasing cutting temperature. If it is left unchecked, it may lead to vibration of the tool and workpiece and the condition of effective cutting may no longer exist. As for the auxiliary blade, it determines the size and surface finish of the workpiece. The wear of the flank may result in substandard products and poor surface finish. Under most actual cutting conditions, the tool will be effective when the wear of the main rake face is larger than that of the secondary rake face, resulting in unqualified parts. Because of the uneven distribution of stress on the tool surface, the stress in the sliding contact area between the chip and the front tool face is the largest at the beginning of the sliding contact area, while it is zero at the end of the contact area, so abrasive wear occurs in this area. This is because there is more serious wear near the cutting block than near the blade, and the wear near the blade is lighter due to the loss of contact between the chip and the rake face. This results in pitting on the rake face at a certain distance from the cutting edge, which is usually considered as wear on the rake face. Usually, the wear cross section is circular. In many cases and for actual cutting conditions, the wear of rake face is lighter than that of flank face, so the wear of flank face is more commonly used as the scale sign of tool failure. However, as many authors have indicated, the temperature on the rake face rises faster than that on the flank face with increasing cutting speed, and the wear rate in any form is essentially affected by temperature changes. Therefore, the wear of rake face usually occurs in high-speed cutting. The tail of the main flank wear belt of the tool is in contact with the surface of the unprocessed workpiece, so the flank wear is more obvious than along the end of the wear belt, which is the most common. This is due to the local effect, which is like the hardened layer on the unprocessed surface. This effect is caused by the hardening of the workpiece caused by the previous cutting. Not only cutting, but also local high temperature produced by the blade, such as oxide skin, can cause this effect. This kind of local wear is usually called pitting wear and is occasionally very serious. Although the appearance of concave pits has no substantial impact on the cutting properties of the tool, the concave pits often deepen gradually. If the cutting continues, the tool will be in danger of fracture. If any progressive form of wear is allowed to continue to develop, the ultimate wear rate will increase significantly and the tool will have destructive failure damage, that is, the tool will no longer be used for cutting, resulting in the scrap of the workpiece, that is good, serious machine tool damage can be caused. For all kinds of cemented carbide tools and for all kinds of wear, it is considered that the end of tool life cycle has been reached before serious failure occurs. However, for all kinds of high-speed steel tools, the wear is non-uniform. It has been found that when the wear permits continuous or even serious failure, the most significant thing is that the tool can be used for regrinding. Of course, in practice, the cutting time is much shorter than the time when the tool is used for failure. One of the following phenomena is the characteristic of the beginning of tool failure: the most common is the sudden increase of cutting force, the serious increase of burnout rings and noise on the workpiece, etc.
3. The influence of cutting parameters on cutting temperature
In metal cutting operation, heat occurs in the main deformation zone and the secondary deformation zone. This results in complex temperature distributions throughout cutters, workpieces and chips. The figure shows a set of typical isothermal curves, from which it can be seen that, as can be expected, when the workpiece material is cut in the main deformation zone, there is a large temperature gradient along the whole chip width, while in the sub-deformation zone, when the chip is cut off, there is a higher temperature on the rake face near the chip. This results in higher cutting temperature near the cutting edge of the rake face and chips. In essence, because all the functions in metal cutting are converted into heat, it can be predicted that these factors, which consume Zeng's unit volume power of the cut metal, will increase the cutting temperature. When the rake angle of the tool increases and all other parameters remain unchanged, the power consumption per unit volume of the cutting metal will be reduced, and the cutting temperature will also be reduced. This situation is even more complicated when considering the increase of undeformed chip thickness and cutting speed. The increasing trend of undeformed chip thickness will lead to a proportional effect on the total heat passing through the workpiece. Tools and chips still maintain a fixed proportion, while the change of cutting temperature tends to decrease. However, with the increase of cutting speed, the amount of heat transferred to the workpiece decreases, which in turn increases the chip temperature rise in the main deformation zone. Furthermore, the sub-deformation zone is bound to be smaller, which will have a warming effect in this area. The change of other cutting parameters has no effect on the unit volume consumption of the cut, so it has no effect on the cutting temperature in fact. Because facts have shown that even a small change in cutting temperature will have a substantial impact on tool wear rate. This shows that it is appropriate to determine the cutting temperature from the cutting parameters. The most direct and accurate method for measuring the temperature of HSS cutters is the Wright-Trent method, which provides detailed information on the temperature distribution of HSS cutters. This technology is based on the metallographic microscopic measurement of high-speed steel tool cross-section. The aim is to establish the relationship between the microstructural change and the thermal change law. Wright has discussed the method of measuring cutting temperature and temperature distribution of HSS tools when processing a wide range of workpiece materials. This technology has been further developed by using electron microscopic scanning technology. The purpose of this technology is to study the microstructural changes caused by tempering high-speed steels with various martensitic structures. This technique is also used to study the temperature distribution of single point turning tools and twist drills for high speed steel.
4. Design of Automatic Fixture
The traditional synchronous fixture used for assembling equipment moves the parts to the center of the fixture to ensure that the parts are removed from the conveyor or from the device disc and placed on the positioned position. However, in some applications, forcing parts to move to the central line may cause parts or equipment damage. When parts are fragile and small vibration may lead to scrap, or when the position is specified by the spindle or die of the machine tool, or when the tolerance requirements are very precise, it is preferable to let the fixture adapt to the position of the parts, rather than vice versa. For these tasks, Zaytran, Elyria, Ohio, USA, has developed asynchronous Western-type flexibility fixtures for general functional data. Because the clamp force and synchronization device are independent, the synchronization device can be replaced by a precise sliding device without affecting the clamp force. Fixture specifications range from 0.2 inch stroke, 5 pound clamping force to 6 inch stroke, 400 inch clamping force. The characteristic of modern production is that the batch size is becoming smaller and smaller, and the product specifications change most. Therefore, in the final stage of production, assembly is particularly vulnerable due to changes in production plans, batches and product designs. This situation is forcing many companies to devote more efforts to extensive rationalization reforms and assembly automation as mentioned earlier. Although the development of flexible fixture is lagging behind the development of flexible transportation processing equipment, such as industrial robots, it is still trying to increase the flexibility of fixture. In fact, the special investment of production equipment, an important fixture device, strengthens the economic support of making fixture more flexible. According to their flexibility, fixtures can be divided into: special fixtures, modular fixtures, standard fixtures, high flexible fixtures. Flexible fixtures are characterized by their high adaptability to different workpieces and low cost of replacement. Flexible fixtures with changeable structural forms are equipped with parts with changeable structural arrangements (such as needle-shaped buccal plates, multi-piece parts and sheet-shaped buccal plates), non-special clamping or clamping elements for standard workpieces (such as starting standard clamping fixtures and fixture fittings with movable components), or ceramic or hardened intermediates (such as flow particle bed fixtures and thermal fixtures). Tighten clamp. In order to produce, parts need to be tightened in fixtures. There are several steps which have nothing to do with the flexibility of fixtures. According to the part processed, i.e. the basic part and the working characteristics, the required position of the workpiece in the fixture is determined. Then the combination of several stable planes must be selected. These stable planes constitute the clamping of the workpiece fixed in the fixture to determine its position. The shape contour structure balances all forces and moments, and ensures that it is close to the working characteristics of the workpiece. Finally, it is necessary to calculate, adjust and assemble the required positions of dismountable or standard fixture elements so that the workpiece can be firmly clamped in the fixture. According to this program, the contour structure and assembly planning and recording process of fixture can be controlled automatically. The task of structural modeling is to produce a combination of several stable planes, so that the clamping forces on these planes will stabilize the workpiece and fixture. Traditionally, this task can be accomplished in a man-machine conversation, which is almost fully automated. One-man-machine conversation, that is to say, the advantage of automatic fixture structure modeling is that it can organize and plan fixture design, reduce the required designers, shorten the research cycle and better configure working conditions. In short, it can successfully improve the production efficiency and efficiency of fixture. With the full preparation of the construction scheme and a batch of materials, the first assembly can successfully save up to 60% of the time.
The use of automatic fixture can reduce manpower and facilitate rhythmic production. The use of automatic fixtures instead of people to work, this is a direct reduction of manpower - one side, together because the use of automatic fixtures can be connected to the work, this is another side of reducing manpower. Therefore, in the inductive processing active line of automated machine tools, there is no automatic fixture at present, in order to reduce manpower and more precise control of the production rhythm, so as to facilitate the rhythmic operation of production.
The use of automatic fixture is conducive to the degree of initiative in data transmission, workpiece loading and unloading, tool replacement and machine installation, and then can improve labor productivity and reduce production costs.
中文譯文
機械加工過程介紹
作為產生形狀的一種加工方法,機械加工是所有制造過程中最普遍使用的而且是最重要的方法。機械加工過程是一個產生形狀的過程,在這過程中,驅動裝置使工件上的一些材料以切屑的形式被去除。盡管在某些場合,工件無承受的情況下,使用移動式裝備來實現加工,但大多數的機械加工是通過既支承工件又支承刀具的裝備來完成。加工知識的過程有兩個方面。小批生產低費用。對于鑄造、鍛造和壓力加工,每一個要生產的具體工件形狀,即使是一個零件,幾乎都要花費高額的加工費用。靠焊接來產生的結構形狀,在很大程度上取決于有效的原材料的形式。一般來說,通過利用貴重設備而又無需特種加工條件下,幾乎可以以任何種類原材料開始,借助機械加工把原材料加工成任意所需要的結構形狀,只要外部尺寸足夠大,那都是可能的。因此對于生產一個零件,甚至當零件結構及要生產的批量大小上按原來都適于用鑄造、鍛造或者壓力加工來生產的,但通常寧可選擇機械加工。嚴密的精度和良好的表面光潔度,機械加工的第二方面用途是建立在高精度和可能的表面光潔度基礎上。許多零件,如果用別的其他方法來生產屬于大批量生產的話,那么在機械加工中則是屬于低公差且又能滿足要求的小批量生產了。另方面,許多零件靠較粗的生產加工工藝提高其一般表面形狀,而僅僅是在需要高精度的且選擇過的表面才進行機械加工。例如內螺紋,除了機械加工之外,幾乎沒有別的加工方法能進行加工。又如已鍛工件上的小孔加工,也是被鍛后緊接著進行機械加工才完成的。?
1?基本的機械加工參數
切削中工件與刀具的基本關系是以以下四個要素來充分描述的:刀具的幾何形狀,切削速度,進給速度,和背吃刀量。切削刀具必須用一種合適的材料來制造,它必須是強固、韌性好、堅硬而且耐磨的。刀具的幾何形狀以刀尖平面和刀具角為特征,對于每一種切削工藝都必須是正確的。切削速度是切削刃通過工件表面的速率,它是以每分鐘英寸來表示。為了有效地加工,切削速度高低必須適應特定的工件與刀具配合。一般來說,工件材料越硬,速度越低。進給速度是刀具切進工件的速度。若工件或刀具作旋轉運動,進給量是以每轉轉過的英寸數目來度量的。當刀具或工件作往復運動時,進給量是以每一行程走過的英寸數度量的。一般來說,在其他條件相同時,進給量與切削速度成反比。背吃刀量以英寸計是刀具進入工件的距離。它等于旋削中的切屑寬度或者等于線性切削中的切屑的厚度。粗加工比起精加工來,吃刀深度較深。?
2?刀具磨損??
從已經被處理過的無數脆裂和刃口裂紋的刀具中可知,刀具磨損基本上有三種形式:后刀面磨損,前刀面磨損和V型凹口磨損。后刀面磨損既發(fā)生在主刀刃上也發(fā)生副刀刃上。關于主刀刃,因其擔負切除大部金屬切屑任務,這就導致增加切削力和提高切削溫度,如果聽任而不加以檢查處理,那可能導致刀具和工件發(fā)生振動且使有效切削的條件可能不再存在。關于副刀刃,那是決定著工件的尺寸和表面光潔度的,后刀面磨損可能造成尺寸不合格的產品而且表面光潔度也差。在大多數實際切削條件下,由于主前刀面先于副前刀面磨損,磨損到達足夠大時,刀具將實效,結果是制成不合格零件。由于刀具表面上的應力分布不均勻,切屑和前刀面之間滑動接觸區(qū)應力,在滑動接觸區(qū)的起始處最大,而在接觸區(qū)的尾部為零,這樣磨蝕性磨損在這個區(qū)域發(fā)生了。這是因為在切削卡住區(qū)附近比刀刃附近發(fā)生更嚴重的磨損,而刀刃附近因切屑與前刀面失去接觸而磨損較輕。這結果離切削刃一定距離處的前刀面上形成麻點凹坑,這些通常被認為是前刀面的磨損。通常情況下,這磨損橫斷面是圓弧形的。在許多情況中和對于實際的切削狀況而言,前刀面磨損比起后刀面磨損要輕,因此后刀面磨損更普遍地作為刀具失效的尺度標志。然而因許多作者已經表示過的那樣在增加切削速度情況下,前刀面上的溫度比后刀面上的溫度升得更快,而且又因任何形式的磨損率實質上是受到溫度變化的重大影響。因此前刀面的磨損通常在高速切削時發(fā)生的。刀具的主后刀面磨損帶的尾部是跟未加工過的工件表面相接觸,因此后刀面磨損比沿著磨損帶末端處更為明顯,那是最普通的。這是因為局部效應,這像未加工表面上的已硬化層,這效應是由前面的切削引起的工件硬化造成的。不只是切削,還有像氧化皮,刀刃產生的局部高溫也都會引起這種效應。這種局部磨損通常稱作為凹坑性磨損,而且偶爾是非常嚴重的。盡管凹坑的出現對刀具的切削性質無實質意義的影響,但凹坑常常逐漸變深,如果切削在繼續(xù)進行的話,那么刀具就存在斷裂的危機。如果任何進行性形式的磨損任由繼續(xù)發(fā)展,最終磨損速率明顯地增加而刀具將會有摧毀性失效破壞,即刀具將不能再用作切削,造成工件報廢,那算是好的,嚴重的可造成機床破壞。對于各種硬質合金刀具和對于各種類型的磨損,在發(fā)生嚴重失效前,就認為已達到刀具的使用壽命周期的終點。然而對于各種高速鋼刀具,其磨損是屬于非均勻性磨損,已經發(fā)現:當其磨損允許連續(xù)甚至到嚴重失效開始,最有意義的是該刀具可以獲得重磨使用,當然,在實際上,切削時間遠比使用到失效的時間短。以下幾種現象之一均是刀具嚴重失效開始的特征:最普遍的是切削力突然增加,在工件上出現燒損環(huán)紋和噪音嚴重增加等。?
3?切削參數的改變對切削溫度的影響??
金屬切削操作中,熱是在主變形區(qū)和副變形區(qū)發(fā)生的。這結果導致復雜的溫度分布遍及刀具、工件和切屑。圖中顯示了一組典型等溫曲線,從中可以看出:像所能預料的那樣,當工件材料在主變形區(qū)被切削時,沿著整個切屑的寬度上有著很大的溫度梯度,而當在副變形區(qū),切屑被切落時,切屑附近的前刀面上就有更高的溫度。這導致了前刀面和切屑離切削刃很近的地方切削溫度較高。實質上由于在金屬切削中所做的全部功能都被轉化為熱,那就可以預料:被切離金屬的單位體積功率消耗曾家的這些因素就將使切削溫度升高。這樣刀具前角的增加而所有其他參數不變時,將使切離金屬的單位體積所耗功率減小,因而切削溫度也將降低。當考慮到未變形切屑厚度增加和切削速度,這情形就更是復雜。未變形切屑厚度的增加趨勢必導致通過工件的熱的總數上產生比例效應,刀具和切屑仍保持著固定的比例,而切削溫度變化傾向于降低。然而切削速度的增加,傳導到工件上的熱的數量減少而這又增加主變形區(qū)中的切屑溫升。進而副變形區(qū)勢必更小,這將在該區(qū)內產生升溫效應。其他切削參數的變化,實質上對于被切離的單位體積消耗上并沒有什么影響,因此實際上對切削溫度沒有什么作用。因為事實已經表明:切削溫度即使有小小的變化對刀具磨損率都將有實質意義的影響作用。這表明如何人從切削參數來確定切削溫度那是很合適的。測定高速鋼刀具溫度的最直接和最精確的方法是萊特&特倫特法,這方法也就是可提供高速鋼刀具溫度分布的詳細信息的方法。該項技術是建立在高速鋼刀具截面金相顯微測試基礎上,目的是要建立顯微結構變化與熱變化規(guī)律圖線關系式。當要加工廣泛的工件材料時,萊特已經論述過測定高速鋼刀具的切削溫度及溫度分布的方法。這項技術由于利用電子顯微掃描技術已經進一步發(fā)展,目的是要研究將已回過火和各種馬氏體結構的高速鋼再回火引起的微觀顯微結構變化情況。這項技術亦用于研究高速鋼單點車刀和麻花鉆的溫度分布。?
4?自動夾具設計??
用做裝配設備的傳統同步夾具把零件移動到夾具中心上,以確保零件從傳送機上或從設備盤上取出后置于已定位置上。然而在某些應用場合、強制零件移動到中心線上時,可能引起零件或設備破壞。當零件易損而且小小振動可能導致報廢時,或當其位置是由機床主軸或模具來具體時,再或者當公差要求很精密時,那寧可讓夾具去適應零件位置,而不是相反。為著這些工作任務,美國俄亥俄州Elyria的Zaytran公司已經開發(fā)了一般性功能數據的非同步西類柔順性夾具。因為夾具作用力和同步化裝置是各自獨立的,該同步裝置可以用精密的滑移裝置來替換而不影響夾具作用力。夾具規(guī)格范圍是從0.2英寸行程,5英鎊夾緊力到6英寸行程、400英寸夾緊力?,F代生產的特征是批量變得越來越小而產品的各種規(guī)格變化最大。因此,生產的最后階段,裝配因生產計劃、批量和產品設計的變更而顯得特別脆弱。這種情形正迫使許多公司更多地致力于廣泛的合理化改革和前面提到過情況那樣裝配自動化。盡管柔性夾具的發(fā)展很快落后與柔性運輸處理裝置的發(fā)展,如落后于工業(yè)機器人的發(fā)展,但仍然試圖指望增加夾具的柔順性。事實上夾具的重要的裝置——生產裝置的專向投資就加強了使夾具更加柔性化在經濟上的支持。根據它們柔順性,夾具可以分為:專用夾具、組合夾具、標準夾具、高柔性夾具。柔性夾具是以它們對不同工件的高適應性和以少更換低費用為特征的。結構形式可變換的柔性夾具裝有可變更結構排列的零件(例如針形頰板,多片式零件和片狀頰板),標準工件的非專用夾持或夾緊元件(例如:啟動標準夾持夾具和帶有可移動元件的夾具配套件),或者裝有陶瓷或硬化了的中介物質(如:流動粒子床夾具和熱夾具緊夾具)。為了生產,零件要在夾具中被緊固,需要產生夾緊作用,其有幾個與夾具柔順性無關的步驟:根據被加工的即基礎的部分和工作特點,確定工件在夾具中的所需的位置,接著必須選擇若干穩(wěn)定平面的組合,這些穩(wěn)定平面就構成工件被固定在夾具中確定位置上的夾持狀輪廓結構,均衡所有各力和力矩,而且保證接近工件工作特點。最后,必須計算、調整、組裝可拆裝的或標準夾具元件的所需位置,以便使工件牢牢地被夾緊在夾具中。依據這樣的程序,夾具的輪廓結構和裝合的規(guī)劃和記錄過程可以進行自動化控制。?結構造型任務就是要產生若干穩(wěn)定平面的組合,這樣在這些平面上的各夾緊力將使工件和夾具穩(wěn)定。按慣例,這個任務可用人—機對話即幾乎完全自動化的方式來完成。一人—機對話即以自動化方式確定夾具結構造型的優(yōu)點是可以有組織有規(guī)劃進行夾具設計,減少所需的設計人員,縮短研究周期和能更好地配置工作條件。簡言之,可成功地達到顯著提高夾具生產效率和效益。在充分準備了構造方案和一批材料情況下,在完成首次組裝可以成功實現節(jié)約時間達60%。
自動夾具的使用能夠減輕人力,并便于有節(jié)奏的出產。使用自動夾具代替人進行作業(yè),這是直接削減人力的-個旁邊面,一起因為使用自動夾具能夠接連的作業(yè),這是削減人力的另一個旁邊面。因而,在主動化機床的歸納加工主動線上,當前簡直都沒有自動夾具,以削減人力和更精準的操控出產的節(jié)拍,便于有節(jié)奏的進行作業(yè)出產。
使用自動夾具有利于完成資料的傳送、工件的裝卸、刀具的替換以及機器的安裝等的主動化的程
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