FZY-300液壓式半球閥閥座裝配機(jī)工作裝置設(shè)計【含15張CAD圖紙】
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畢業(yè)設(shè)計(論文)外文資料翻譯
設(shè)計題目: FZY-300液壓式半球閥閥座裝配機(jī)設(shè)計
—工作裝置設(shè)計
譯文題目: 先進(jìn)加工方法
院系名稱： 機(jī)電工程學(xué)院 專業(yè)班級：
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附 件： 1.外文資料翻譯譯文；2.外文原文。
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附件1：外文資料翻譯譯文
先進(jìn)加工方法
摘要：隨著產(chǎn)品硬件結(jié)構(gòu)的復(fù)雜化，新的、富有遠(yuǎn)見的加工方法正得到普及，這已經(jīng)成為近幾年機(jī)械加工行業(yè)的發(fā)展趨勢。隨著其他科技諸如電子技術(shù)及電子計算機(jī)技術(shù)的發(fā)展，機(jī)床的控制方法和材料成形方法也變得日新月異。甚至它們提供給設(shè)計者的設(shè)計方法和加工工藝可能遠(yuǎn)遠(yuǎn)超過那些最有經(jīng)驗的設(shè)計師。這就迫使機(jī)械設(shè)計人員從事與以往不同的研究。本文主要探討的是數(shù)控加工過程中所使用的工具。CNC控制器能用來驅(qū)動和控制機(jī)床運動，同時由于計算機(jī)技術(shù)的快速發(fā)展，數(shù)控機(jī)床的編程也變得越來越容易。
關(guān)鍵詞：數(shù)控機(jī)床；計算機(jī)輔助設(shè)計；計算機(jī)輔助制造
1. 數(shù)控機(jī)床的發(fā)展
在現(xiàn)今的加工制造領(lǐng)域，數(shù)控機(jī)床已經(jīng)得到廣泛地應(yīng)用。數(shù)控機(jī)床起源于英國，發(fā)展于美國。在第二次世界大戰(zhàn)之后，隨著商業(yè)和軍事的快速發(fā)展，在勞動密集型加工企業(yè)中，機(jī)械加工的精度往往得不到有效地保證，那么怎么克服常規(guī)加工方法中加工精度不足的問題呢？1949年美國政府授權(quán)美國空軍與Parsons公司簽約，讓他們找到一種靈活的、有力的制造系統(tǒng)，以便擴(kuò)大生產(chǎn)，提高生產(chǎn)效率。在1949—1951期間，他們聯(lián)合發(fā)明了一種可使用多種刀具的第一個數(shù)控系統(tǒng)。辛辛那提機(jī)床刀具公司把他們的一個28英寸的“Hydro—Tel”軍用機(jī)床改裝為三軸自動機(jī)床，同時改變了它們的外部輪廓。在美國數(shù)控機(jī)床發(fā)展的同時，英國公司ALIFRED Herber也制造出了一臺NC機(jī)床。1956年更可靠的曲線路徑控制系統(tǒng)開始使用。幾年后，美國與歐洲開始了更深遠(yuǎn)的研究。
早期的數(shù)控機(jī)床主要應(yīng)用于航空業(yè)，因為它用的零件的幾何形狀比較復(fù)雜，如渦輪機(jī)葉片，同時航空工業(yè)需要的復(fù)雜的控制系統(tǒng)。隨著點與點控制器的發(fā)展，數(shù)控機(jī)床更為廣泛地用于機(jī)械零件的加工當(dāng)中去。較簡單的點與點控制機(jī)床不僅比復(fù)雜的連續(xù)路徑的同類產(chǎn)品便宜，而且加工精度也比較高。
2.NC優(yōu)勢
數(shù)控機(jī)床與普通機(jī)床擁有相同的物理特性，其金屬切削的原理與普通機(jī)床也是一樣的。數(shù)控機(jī)床與普通機(jī)床最大的不同在于數(shù)控機(jī)床是用計算機(jī)控制主軸的動作，而CNC機(jī)床的最大優(yōu)勢在于準(zhǔn)確而快速的定位功能。CNC控制的機(jī)床可能簡單得像2軸鉆床加工中心。低轉(zhuǎn)速、高馬力的特性使其可以提高金屬的切削效率。高轉(zhuǎn)速主軸使其可以利用高切削速度的工具，如鉆頭、小直徑銑刀。這些依賴機(jī)床型號的切削刀具都是一些標(biāo)準(zhǔn)件，如磨床的刀具、鉆頭或車刀。數(shù)控機(jī)床對切削速度和進(jìn)給量的控制像普通機(jī)床一樣精確。數(shù)控機(jī)床不會在一次加工完成后停下來計劃下一次加工過程，它不會疲勞，不會中斷。當(dāng)能夠準(zhǔn)確控制數(shù)控機(jī)床的切削速度時，就可以通過控制進(jìn)給速度來提高加工效率，目前進(jìn)給速度已經(jīng)從原來的60英寸/分發(fā)展到200英寸/分、400英寸/分甚至1000英寸/分了。
在數(shù)控機(jī)床出現(xiàn)之前，復(fù)雜形狀零件的加工是極其困難的。數(shù)控機(jī)床的出現(xiàn)使得這些復(fù)雜形狀零件的加工變得更加容易。通過改變加工程序可以很容易地實現(xiàn)不同零件的加工。數(shù)控機(jī)床不需要額外的時間和特別的預(yù)防措施就可以加工出高精度的零件。同時數(shù)控機(jī)床還不需要復(fù)雜的夾具，從而節(jié)省了裝卡的時間。一旦零件的加工程序編寫好，那么每一個零件的加工時間就是一樣的。這樣重復(fù)性的加工就可以精確地控制加工成本。在傳統(tǒng)加工過程中，為了提高加工效率，一批零件通常要大量加工。有了數(shù)控機(jī)床，就是一個零件都可以高效地加工出來。這樣就可以減少大量庫存，減少成本，提高經(jīng)濟(jì)效益。現(xiàn)在一臺數(shù)控機(jī)床可以完成多臺不同類型的普通機(jī)床同時才能完成的操作。它就像一個熟練的工程師，通過編程就可以很經(jīng)濟(jì)地加工出各種各樣的零件。
目前利用數(shù)控機(jī)床進(jìn)行加工制造時通常需要三類人。第一類人是數(shù)控編程人員，主要任務(wù)是編寫機(jī)床運行的代碼，這類人通常不需要與數(shù)控機(jī)床直接接觸；第二類人是程序安裝人員，主要是把程序裝入機(jī)床控制單元，然后檢查程序并進(jìn)行試件加工，數(shù)控機(jī)床的控制單元（單片機(jī)）還可以用于改變、更正加工程序；第三類人是操作人員以及加工完成后卸載零件。在一個小公司中，也許一個人就能完成三個人的工作。
數(shù)控機(jī)床一般分成兩大類。一類是利用G代碼和M代碼進(jìn)行編程輸入的；另一類是利用人機(jī)對話方式輸入。所謂的人機(jī)對話也被稱為人性化或提示輸入。
3.CAM和CNC
目前隨著計算機(jī)輔助制造技術(shù)的發(fā)展，其正在改變數(shù)控編程人員的工作，即從簡單的人工編程到變成一個最大的數(shù)控程序輸出機(jī)。自從數(shù)控機(jī)床出現(xiàn)，各種各樣的數(shù)控控制單元也各不相同。由于不同的控制單元利用不同的編程語言和代碼進(jìn)行編程，而不同的控制代碼可能不能被不同的控制單元識別。為了制造一種在不同控制單元上都可以利用的代碼，每一個數(shù)控機(jī)床制造商都在不斷地提高和更新它們的控制器。這些改進(jìn)主要包括新加的代碼在已有的代碼的基礎(chǔ)上工作。
計算機(jī)輔助制造系統(tǒng)還使得編程員有更多的精力專注于加工工藝的選擇而不是程序代碼的編寫。每當(dāng)編程員接到一個圖紙，他首先考慮的是怎么把它加工處來，從數(shù)控機(jī)床的選擇、加工工藝的選擇、夾具的選擇，每一個方面都必須考慮。這就要求數(shù)控編程人員對機(jī)床的特性、功能，如機(jī)床主軸馬力、最大轉(zhuǎn)速、工作臺重量等有一個了解。同時數(shù)控編程人員還必須對加工制造的知識有一定了解，比如為了得到需要的加工精度及表面粗糙度，選擇什么樣的刀具，刀具的材料如何等，這就要求對刀具的知識有一定地了解。因為刀具的不斷更新，過去的編程人員必須花費大量的時間來研究刀具、刀具材料等加工制造的基本知識。現(xiàn)在新的刀具信息不僅可以通過手冊或刀具制造商那里獲得，也可以從刀具制造商的軟件中獲得。
在加工制作過程中，也有各種軟件幫助編程人員。比如，Kennametal 公司的"TOOLPRO"軟件就可以幫助編程人員在面對不同的加工情況下怎樣選擇最佳的加工要素，如切削速度，進(jìn)給速度等。"TOOLPRO"軟件的另一個優(yōu)勢就是可以幫助編程人員選擇加工時所需的機(jī)床功率，這就比人工粗選精確得多。通過軟件的幫助，編程人員就可以很容易地確定在加工過程中需要的各種加工要素。比如精加工，當(dāng)零件在加工中最小進(jìn)給量確定了，就可以選擇最佳的切削速度，這就極大地提高了機(jī)床的加工效率。目前，在加工中心中使用的軟件主要是是ENGERSOLL CUTTING TOOL公司的ACTUAL CHIP THICKNESS的軟件，該軟件可以用來幫助編程人員預(yù)估在加工過程中，特別是高精度的加工中的進(jìn)給量。
有了這些軟件的幫助，現(xiàn)在的編程人員的工作就可以這樣進(jìn)行：
首先，編程人員繪制需要加工零件的模型。然后考慮零件的加工工序，是粗加工還是精加工、是車還是磨削，裝夾卡具是虎鉗、抓盤還是卡盤等。這些考慮之后，就可以用計算機(jī)編寫工藝卡了，該工藝卡包括各種記錄，如加工工件單位是公制還是英制、機(jī)床類型、參數(shù)、刀具選擇、切削材料類型、安裝夾緊等。
然后就是利用計算機(jī)模擬零件的加工過程。從軟件中選擇機(jī)床，確定加工過程中的各種參數(shù)。如鉆削的時候，當(dāng)孔的位置坐標(biāo)和加工深度確定以后，那么就可以精確地在該點加工孔了。如果位置錯了，還可以撤銷這一記錄，然后輸入新的坐標(biāo)。當(dāng)磨削端面的時候，切削運動一般是一條弧線，如果編程的時候錯誤地編成直線了，軟件還會自動報警，提醒編程人員。
在程序運行的過程中，顯示軌跡的命令可以在顯示器上顯示當(dāng)前刀具的運行軌跡，同時也會顯示各種刀具在加工過程中的使用順序，當(dāng)需要改變刀具的使用順序的時候，只用一個簡單的命令就可以實現(xiàn)。
但是，CAM程序的加工順序與普通機(jī)床加工中的工序可能不相同。例如，在零件上加工孔時，普通機(jī)床上是操作人員根據(jù)已加工孔的外部輪廓來定位加工內(nèi)孔。在CAM中，程序員可以選擇各種不同的粗基準(zhǔn)進(jìn)行模擬加工，以便選出最有效的加工方法。在模擬的過程中，不同的顏色代表不同的刀具，這樣就可以方便的觀察不同刀具的運行軌跡。同時CAM系統(tǒng)還可以讓程序員從不同的角度，比如頂部、正面、側(cè)面觀察圖形，以便發(fā)現(xiàn)錯誤。比如刀具的軌跡，在俯視圖中可能正確，但在主視圖中，切削深度可能不一樣，這樣的變化很容易看得到。
當(dāng)?shù)毒呗窂郊凹庸ろ樞虼_定以后，機(jī)床加工的程序代碼就會自動生成。在機(jī)床加工工件的時候，機(jī)床代碼發(fā)生器需要四個文件。JOBPLAN文件表示刀具信息，GRAPHICS文件表示刀具路徑和切削順序，也用MACHINE DEFINE文件表示CNC代碼命令。這個文件可提供加工過程中需要的最大的進(jìn)給速度、轉(zhuǎn)速、加工時間等等。當(dāng)代碼發(fā)生器完成操作的時候，零件加工的計劃時間也就隨之確定。這個時間是根據(jù)進(jìn)給速度、運行的距離、兩點間在最大進(jìn)給速度下無切削運動的時間、換刀時間等等確定的。確定的加工時間可用來估計生產(chǎn)費用。若不僅僅只有一類CNC機(jī)床來加工該工件，比較不同機(jī)床的加工總時間就可以選擇一種更有效的機(jī)床來加工
4.CAD/CAM
目前另一個確立刀具路徑的方法是借助計算機(jī)輔助繪圖。因為零件的圖形輪廓和信息都存儲在電腦上。SmartCAM通過CAM CONNECTION讀取CAD圖，然后轉(zhuǎn)換圖形。相對于用程序表示外形，現(xiàn)在可以用圖形輪廓表示即可。但是程序員還需要編寫含有刀具信息的工藝卡。然后，使用SHOWPATH功能可以顯示每個刀具的路徑和使用的順序。
隨著CAD/CAM技術(shù)的交叉發(fā)展，CAD/CAM的工作方式也在變換著。一些CAD/CAM程序在計算機(jī)上可以在一些按鍵、圖紙、程序等方面相互轉(zhuǎn)換。
附件2：外文原文
ADVANCED MACHINING PROCESSES
Abstract: As the hardware of an advanced technology becomes more complex, new and visionary approaches to the processing of materials into useful products come into common use. This has been the trend in machining processes in recent years.. Advanced methods of machine control as well as completely different methods of shaping materials have permitted the mechanical designer to proceed in directions that would have been totally impossible only a few years ago.
Parallel development in other technologies such as electronics and computers have made available to the machine tool designer methods and processes that can permit a machine tool to far exceed the capabilities of the most experienced machinist.
In this section we will look at CNC machining using chip-making cutting tools. CNC controllers are used to drive and control a great variety of machines and mechanisms, Some examples would be routers in wood working; lasers, plasma-arc, flame cutting, and waterjets for cutting of steel plate; and controlling of robots in manufacturing and assembly. This section is only an overview and cannot take the place of a programming manual for a specific machine tool. Because of the tremendous growth in numbers and capability of computers ,changes in machine controls are rapidly and constantly taking place. The exciting part of this evolution in machine controls is that programming becom eseasier with each new advanced in this technology.
key word: CNC CAD CAM
The Early Development Of Numerically Controlled Machine Tools
The highly sophisticated CNC machine tools of today, in the vast and diverse range found throughout the field of manufacturing processing, started from very humble beginnings in a number of the major industrialized countries. Some of the earliest research and development work in this field was completed in USA and a mention will be made of the UK's contribution to this numerical control development.
A major problem occurred just after the Second World War, in that progress in all areas of military and commercial development had been so rapid that the levels of automation and accuracy required by the modern industrialized world could not be attained from the lab our intensive machines in use at that time. The question was how to overcome the disadvantages of conventional plant and current manning levels. It is generally acknowledged that the earliest work into numerical control was the study commissioned in 1947 by the US government. The study's conclusion was that the metal cutting industry throughout the entire country could not copy with the demands of the American Air Force, let alone the rest of industry! As a direct result of the survey, the US Air Force contracted the Persons Corporation to see if they could develop a flexible, dynamic, manufacturing system which would maximize productivity. The Massachusetts Institute of Technology (MIT) was sub-contracted into this research and development by the Parsons Corporation, during the period 1949-1951,and jointly they developed the first control system which could be adapted to a wide range of machine tools. The Cincinnati Machine Tool Company converted one of their standard 28 inch "Hydro-Tel" milling machines or a three-axis automatic milling made use of a servo-mechanism for the drive system on the axes. This machine made use of a servomechanism for the drive system on the axes, which controlled the table positioning, cross-slide and spindle head. The machine cab be classified as the first truly three axis continuous path machine tool and it was able to generate a required shape, or curve, by simultaneous slide way motions, if necessary.
At about the same times as these American advances in machine tool control were taking Place, Alfred Herbert Limited in the United Kingdom had their first Mutinous path control system which became available in 1956.Over the next few years in both the USA and Europe, further development work occurred. These early numerical control developments were principally for the aerospace industry, where it was necessary to cut complex geometric shapes such as airframe components and turbine blades. In parallel with this development of sophisticated control systems for aerospace requirements, a point-to-point controller was developed for more general machining applications. These less sophisticated point-to-point machines were considerably cheaper than their more complex continuous path cousins and were used when only positional accuracy was necessary. As an example of point-to-point motion on a machine tool for drilling operations, the typical movement might be fast traverse of the work piece under the drill's position-after drilling the hole, anther rapid move takes place to the next hole's position-after retraction of the drill. Of course, the rapid motion of the sideways could be achieved by each axis in a sequential and independent manner, or simultaneously. If a separate control was utilisec for each axis, the former method of table travel was less essential to avoid any backlash in the system to obtain the required degree of positional accuracy and so it was necessary that the approach direction to the next point was always the same.
Advantages of Numerical Control
A manually operated machine tool may have the same physical characteristics as a CNC machine, such as size and horsepower. The principles of metal removal are the same. The big gain comes from the computer controlling the machining axes movements. CNC-controlled machine tools can be as simple as a 2-axis drilling machining center. With a dual spindle machining center, the low RPM, high horsepower spindle gives high metal removal rates. The high RPM spindle allows the efficient use of high cutting speed tools such as diamonds and small diameter cutters (Figure O-2). The cutting tools that remove materials are standard tools such as milling cutters, drills, boring tools, or lathe tools depending on the type of machine used. Cutting speeds and feeds need to be correct as in any other machining operation. The greatest advantage in CNC machining comes from the unerring and rapid positioning movements possible. A CNC machine does dot stop at the end of a cut to plan its next move; it does not get fatigued; it is capable of uninterrupted machining error free, hour after hour. A machine tool is productive only while it is making chips.
Since the chip-making process is controlled by the proper feeds and speeds, time savings can be achieved by faster rapid feed rates. Rapid feeds have increased from 60 to 200 to 400 and are now often approaching 1000 inches per minute (IPM). These high feed rates can pose a safety hazard to anyone within the working envelope of the machine tool.
Complex contoured shapes were extremely difficult to product prior to CNC machining .CNC has made the machining of these shapes economically feasible. Design changes on a part are relatively easy to make by changing the program that directs the machine tool.
A CNC machine produces parts with high dimensional accuracy and close tolerances without taking extra time or special precautions, CNC machines generally need less complex work-holding fixtures, which saves time by getting the parts machined sooner. Once a program is ready and production parts, each part will take exactly the same amount of time as the previous one. This repeatability allows for a very precise control of production costs. Another advantage of CNC machining is the elimination of large inventories; parts can be machined as needs .In conventional production often a great number of parts must be made at the same time to be cost effective. With CNC even one piece can be machined economically .In many instances, a CNC machine can perform in one setup the same operations that would require several conventional machines.
With modern CNC machine tools a trained machinist can program and product even a single part economically .CNC machine tools are used in small and large machining facilities and range in size from tabletop models to huge machining centers. In a facility with many CNC tools, programming is usually done by CNC programmers away from the CNC tools. The machine control unit (MCU) on the machine is then used mostly for small program changes or corrections. Manufacturing with CNC tools usually requires three categories of persons. The first is the programmer, who is responsible for developing machine-ready code. The next person involved is the setup person, who loads the raw stork into the MCU, checks that the correct tools are loaded, and makes the first part. The third person is the machine and unloads the finished parts. In a small company, one person is expected to perform all three of these tasks.
CNC controls are generally divided into two basic categories. One uses a ward address format with coded inputs such as G and M codes. The other users a conversational input; conversational input is also called user-friendly or prompted input. Later in this section examples of each of these programming formats in machining applications will be describes.
CAM and CNC
CAM systems have changed the job of the CNC programmer from one manually producing CNC code to one maximizing the output of CNC machines. Since CNC machine tools are made by a great number of manufacturers, many different CNC control units are in use. Control units from different manufacturers use a variety of program formats and codes. Many CNC code words are identical for different controllers, but a great number vary from one to another.
To produce an identical part on CNC machine tools with different controllers such as one by FANCU, OKUMA or DYNAPATH, would require completely different CNC codes. Each manufacturer is constantly improving and updating its CNC controllers. These improvements often include additional code words plus changes in how the existing code works.
A CAM system allows the CNC programmer to concentrate on the creation of an efficient machining process, rather than relearning changed code formats. A CNC programmer looks at the print of a part and then plans the sequence of machining operations necessary to make it (Figure O-3). This plan includes everything, from the selection of possible CNC machine tools, to which，tooling to use, to how the part is held while machining takes place. The CNC programmer has to have a thorough understanding of all the capacities and limitations of the CNC machine tools that a program is to be made for. Machine specifications such as horsepower, maximum spindle speeds, workpiece weight and size limitations, and tool changer capacity are just some of the considerations that affect programming.
Another area of major importance to the programmer is the knowledge of machining processes. An example would be the selection of the surface finish requirement specified in the part print. The sequence of machining processes is critical to obtain acceptable results. Cutting tool limitations have to be considered and this requires knowledge of cutting tool materials, tool types, and application recommendations.
A good programmer will spend a considerable amount of time in researching the rapidly growing volume of new and improved tools and tool materials. Often the tool that was on the cutting edge of technology just two years ago is now obsolete. Information on new tools can come from catalogs or tool manufacturers' tooling engineers. Help in tool selection or optimum tool working conditions can also be obtained from tool manufacturer software. Examples would be Kennametal's "TOOLPRO", software designed to help select the best tool grade, speed, and feed rates for different work materials in turning application. Another very important feature of "TOOLPRO" is the display of the horsepower requirement for each machining selection. This allow the programmer to select a combination of cutting speed, feed rate, and depth of cut that equals the machine's maximum horsepower for roughing cuts. For a finishing cut, the smallest diameter of the part being machined is selected and then the cutting speed varied until the RPM is equal to the maximum RPM of the machine. This helps in maximizing machining efficiency. Knowing the horsepower requirement for a cut is critical if more than one tool is cutting at the same time.
Software for a machining center application would be Ingersoll Tool Company's "Actual Chip Thickness", a program used to calculate the chip thickness in relation to feed-per-tooth for a milling cutter, especially during a shallow finishing cut. Ingersoll's "Rigidity Analysis" software ealculates tool deflection for end mills as a function of tool stiffness and tool force.
To this point we looked at some general qualifications that a programmer should possess. Now we examine how a CAM system works. Point Control Company's SmartCam system uses the following approach. First, the programmer makes a mental model of the part to be machined. This includes the kind of machining to be performed-turning or milling. Then the part print is studied to develop a machining sequence, roughing and finishing cuts, drilling, tapping, and boring operations. What work-holding device is to be used, a vise or fixture or clamps? After these considerations, computer input ；an be started. First comes the creation of a JOBPLAN. This JOBPLAN consists of entries such as inch or metric units, machine type, part ID, type of workpiece material, setup notes, and a description of the required tools.
This line of information describes the tool by number, type, and size and includes the appropriate cutting speed and feed rate. After all the selected tools are entered, the file is saved.
The second programming step is the making of the part. This represents a graphic modeling of the projected machining operation. After selecting a tool from the prepared JOBPLAN, parameters for the cutting operation are entered. For a drill, once the coordinate location of the hole and the depth are given, a circle appears on that spot. If the location is incorrect, the UNDO command erases this entry and allows you to give new values for this operation. When an end mill is being used, cutting movements (toolpath) are usually defined as lines and arcs. As a line is programmed, the toolpath is graphically displayed and errors can be corrected instantly.
At any time during programming, the command SHOWPATH will show the actual toolpath for each of the programmed tools. The tools will be displayed in the sequence in which they will be used during actual machining. If the sequence of a tool movement needs to be changed, a few keystrokes will to that.
Sometimes in CAM the programming sequence is different from the actual machining order. An example would be the machining of a pocket in a part. With CAM, the finished pocket outline is programmed first, then this outline is used to define the roughing cuts to machine the pocket. The roughing cuts are computer generated from inputs such as depth and width of cut and how much material to leave for the finish cut. Different roughing patterns can be tried out to allow the programmer to select the most efllcient one for the actual machining cuts. Since each tool is represented by a different color, it is easy to observe the toolpath made by each one.
A CAM system lets the programmer view the graphics model from varying angles, such as a top, front, side, or isometric view. A toolpath that looks correct from a top view, may show from a front view that the depth of the cutting tool is incorrect. Change
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