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The main Elements of Horizontal Milling Machines Column and base The column and base form the foundation of the complete machine. Both are made from cast iron, designed with thick sections to ensure complete rigidity and freedom from vibration. The base, upon which the column is mounted, is also the cutting-fluid reservoir and contains the pump to circulate the fluid to the cutting area. The column contains the spindle, accurately located in precision bearings. The spindle is driven through a gearbox from a vee-belt drive from the electric motor housed at the base of the column. The gearbox enables a range of spindle speeds to be selected. Twelve spindle speeds from 32 to 1400rev/min are available. The front of the column carries the guide-ways upon which the knee is located and guided in a vertical direction. Knee The knee, mounted on the column guide-ways, provides the vertical movement of the table. Power feed is available, through a gearbox mounted on the side, from a separate built-in motor, providing a range of twelve feed rates from 6 to 250mm/min. Drive is through a lead-screw, whose bottom end is fixed to the machine base. Provision is made to raise and lower the knee by hand through a lead-screw and nut operated by a hand-wheel at the front. The knee has guide-ways on its top surface giving full-width support to the saddle and guiding it in a transverse direction. A lock is provided to clamp the knee in any vertical position on the column. Saddle The saddle, mounted on the knee guide-ways, provides the transverse movement of the table. Power feed is provided through the gearbox on the knee. A range of twelve feeds is available, from 12 to 500mm/min. Alternative hand movement is provided through a lead-screw and nut by a hand-wheel at the front of the knee. Clamping of the saddle to the knee is achieved by two clamps on the side of the saddle. The saddle has dovetail guide-ways on its upper surface, at right angles to the knee guide-ways, to provide a guide to the table in a longitudinal direction. Table The table provides the surface upon which all work-pieces and work-holding equipment are located and clamped. A series of tee slots is provided for this purpose. The dovetail guides on the undersurface locate in the guide-ways on the saddle, giving straight-line movement to the table in a longitudinal direction at right angle to the saddle movement. Power feed is provided from the knee gearbox, through the saddle, to the table lead-screw. Alternative hand feed is provided by a hand-wheel at each end of the table. Stops at the front of the table can be set to disengage the longitudinal feed automatically in each direction. Spindle The spindle, accurately mounted in precision bearings, provides the drive for the milling cutters. Cutters can be mounted straight on the spindle nose or in cutter-holding devices which in turn are mounted in the spindle, held in position by a draw-bolt passing through the hollow spindle. Spindles of milling machines have a standard spindle nose to allow for easy interchange of cutters and cutter-holding devices. The bore of the nose is tapered to provide accurate location, the angle of taper being 16.36”. The diameter of the taper depends on the size of the machine and may be 30, 40 or 50 IST (International standard Taper). Due to their steepness of angle, these tapers-known as non-stick or self-releasing-cannot be relied upon to transmit the drive to the cutter or cutter-holding device. Two driving keys are provided to transmit the drive. Over-arm and arbor support The majority of cutters used on horizontal machines are held on an arbor which is located and held in the spindle. Due to the length of the arbors used, support is required at the outer end to prevent deflection when cutting takes place. Support is provided by an arbor-support bracket, clamped to an over-arm which is mounted on top of the column in a dovetail slide. The over-arm is adjustable in or out for different lengths of arbor, or can be fully pushed in when arbor support is not required. Two clamping bolts are provided to lock the over-arm in any position. The arbor support is located in the over-arm dovetail and is locked by means of its clamping bolt. A solid bearing is provided in which the arbor runs during splindle rotation. Controls of Horizontal Milling Machines The various controls of a typical horizontal milling machine. These are identical to those of a vertical machine: Spindle speeds are selected through the levers 4, and the speed is indicated on the change dial 5. The speeds must not be changed which the machine is running. An inching button 3 is situated below the gear-change panel and, if depressed, inches the spindle and enables the gears to slide into place when a speed change is being carried out. Alongside the inching button is the switch for controlling the cutting-fluid pump 1 and one for controlling the direction of spindle rotation 2. The feed rates are selected by the lever 9 and indicated on the feed-rate dial. To engage the longitudinal table feed, lever 8 is moved in the required direction-right for right feed, lever 8 is moved in the required direction-right for right feed, left for left feed. Adjustable trip dogs 6 are provided to disengage the feed movement at any point within the traverse range. Limit stops are incorporated to disengage all feed movements in the extreme position, to prevent damage to the machine in the event of a trip dog being missed. To engage cross or vertical traverse, lever 12 is moved up or down. The feed can then be engaged by moving lever 11 in the required direction. With cross traverse selected, movement of lever 11 up-words produces in-feed of the saddle, moving it downwards produces out-feed of the saddle. With vertical traverse selected, movement of lever 11 up-words produces up-feed to the knee, moving it downwards produces down-feed to the knee. Rapid traverse in any of the above feed directions is engaged by an up-ward pull of lever 10. Rapid traverse continues as long as up-ward pressure is applied. When released, the lever will drop into the disengaged position. Alternative hand feed is provided by means of a single crank handle 7,which is engaged by slight pressure towards the machine. Spring ejectors disengage the handle on completion of the operation, for safety purposes-I. E. the handle will not fly round when feed or rapid traverse is engaged. The single crank handle is interchangeable on table, saddle, and knee movements. Milling Operations The variety of milling operations which may be performed on a given milling machine depends on the type of machine, the type of cutter used, and the accessories or attachments available for use with the machine. Milling machine are used for machining flat surfaces, including horizontal, vertical, and angular surfaces. They are used for machining many kinds of shoulders and grooves, including keyways, T-slots, and dovetails. They are used to machine formed or irregular surfaces with the use of many types of formed-tooth cutters. Milling machines equipped with a dividing head may be used for machining equally spaced flat surfaces, straight grooves, or spiral grooves on parts with a cylindrical shape. This type of machining is involved in making gears, taps, reamers, drills, milling cutters, and splines on shafts. Milling machines, particularly those of the vertical type, may be used for all of the common hole-machining operations which normally are performed on a drill press. With the milling machine, holes may be precisely located through the use of the table feed screws. The longitudinal and cross-feed screws are equipped with micrometer collars accurately graduated in hundredths of a millimeter (thousandths of an inch)or smaller. Hole depth also may be accurately controlled through the use of graduated collars on the vertical-feed control. Because of the wide variety of operations which may be performed on a milling machine and because of its general efficiency and speed of metal removal, it is one of the most important of the basic machine tools. It ranks in versatility and importance with the metal-working lathe. Safety and Maintenance For CNC Machine Safety Notes for CNC machine operations Safety is always a major concern in a metal-cutting operation. CNC equipment is automated and very fast, and consequently it is a source of hazards. The hazards have to be located and the personnel must be aware of them in order to prevent injuries and damage to the equipment. Main potential hazards include: rotating parts, such as the spindle, the tool in the spindle, chuck, part in the chuck, and the turret with the tools and rotating clamping devices; movable parts, such as the machining center table, lathe slides, tailstock center, and tool carousel; errors in the program such as improper use of the G00 code in conjunction with the wrong coordinate value, which can generate an unexpected rapid motion; an error in setting or changing the offset value, which can result in a collision of the tool with the part or the machine; and a hazardous action of the machine caused by unqualified changes in a proven program. To minimize or avoid hazards, try the following preventive actions: (1) Keep all of the original covers on the machine as supplied by the machine tool builder. (2) Wear safety glasses, gloves, and proper clothing and shoes. (3) Do not attempt to run the machine before you are familiar with its control. (4) Before running the program, make sure that the part is clamped properly. (5) When proving a program, follow there safety procedures: Run the program using the machine Lock function to check the program for errors in syntax and geometry. Slow down rapid motions using the RAPID OVERRIDE switch or dry run the program. Use a single-block execution to confirm each line in the program before executing it. When the tool is cutting, slow down the feed rate using the FEED OVERRIDE switch to prevent excessive cutting conditions. (6) Do not handle chips by hand and do not use chip hooks to break long curled chips. Program different cutting conditions for better chip control. Stop the machine if you need to properly clean the chips. (7) If there is any doubt that the insert will break under the programmed cutting conditions, choose a thicker insert or reduce feed or depth of cut. (8) Keep tool overhang as short as possible, since it can be a source of vibration that can break the insert. (9) When supporting a large part by the center, make sure that the hole-center is large enough to adequately support and hold the part. (10) Stop the machine when changing the tools, indexing inserts, or removing chip. (11) Replace dull or broken tools or inserts. (12) Write a list of offsets for active tools, and clear (set to zero) the offsets for tools removed from the machine. (13) Do not make changes in the program if your supervisor has prohibited your doing so. (14) If you have any safety-related concerns, notify your instructor or supervisor immediately. 2. Daily Maintenance Checking the External View (1) Machine oil (cutting oil, lubrication oil) has been scattered onto the servomotor, detector, or main unit of the NC, or is leaking. (2) Damage is found on the cables of the movable blocks, or the cables are twisted. (3) Filter clogging (4) A door of the control panel is not open. (5) Ambient vibration (6) The unit is located in a dusty location. (7) Something that causes high frequency is placed near the control unit. Checking the inside of the control unit Check that the following troubles have been eliminated: (1) Cable connectors are loosened. (2) Installing screws are loosened. (3) Attachment amplifier screws are loosened. (4) The cooling fan operates abnormally. (5) Cable damage. (6) Printed circuit boards have been inserted abnormally. 3. Fault Diagnosis and Action When a running fault occurs, examine the correct cause to take proper action. To do this, execute the checks below: Checking the Fault Occurrence Status Check the following: When did the fault occur? During what operation did the fault occur? What fault? (1) When did the fault occur? Time of day when the fault occurred. (2) During what operation did the fault occur? What running mode? For automatic operationprogram number, sequence number, and contents of program? For manual operationMode? Operating procedure? Preceding and succeeding operations? Set / display units screen? During I/O operation? Machine system status? During tool change? Controlled axis hunting? What fault occurred? What does the alarm display of the set/display units alarm diagnosis screen indicate? Display the alarm diagnosis screen to check the contents of alarm. What dose the driving amplifier status display indicate? Check the contents of alarm based on the driving amplifier status display What dose the machine sequence alarm indicate? Is the CRT screen normal? Is the control axis hunting? (3) Frequency of fault? When did the fault occur? Frequency? (Did the fault occur during operation of another machine?) If the frequency is too small, or the fault occurred during operation of another machine, the cause may be noises of the supply voltage. For example, in this case, check that 1 the supply voltage is normal (does momentary drop occur during operation of another machine?) and 2 measures have been taken against noises. In specific mode? When did the ceiling crane move? Frequency for the same kind of work? Dose the fault occur when the same operation is made? (Repeatability check) Change the conditions (override, contents of program, operating procedure, etc.). Dose the same fault occur? 2. Fault Example (1) The power cannot be turned on. Check the following points: The power is being supplied? (2) The NC unit dose not operate when being activated. Check the following points: Mode selected normally? All conditions for start satisfied? Depending on the machine, the start may be locked until the predetermined conditions are satisfied. Check this by referring to the manual published by the machine manufacturer. Override or manual speed=0? No reset signal is being generated. No feed hold signal is being generated. Machine lock is on. 3. Alarm Message When the menu key ALARM is pressed, the ALARM/DIAGN screen is displayed. (1) Alarm The code and number or message relating to an operation alarm, program error, servo alarm, or system error are displayed. (2) Stop code The automatic operation disable state or stop state in automatic operation mode is displayed in code and error number. (3) Alarm message The alarm messages specified by the user PLC (built-in) are displayed. (4) Operator message The operator messages specified by the user PLC are displayed. When an alarm occurs, the class code will display on all screens. Refer to the Appendix. List of alarms for details on the alarms. 臥式銑床的主要部件 床身和底座 床身和底座是整個銑床的基礎,它們均由鑄鐵制成,并設計成厚壁狀,以保證有足夠的剛度和抗震性。床身安裝在底座上,底座同時也是儲存切削液的容器,底座內(nèi)裝有使切削液循環(huán)到切削區(qū)去的幫。 床身上裝有主軸,且精確地將主軸定位于精密軸承之中。主軸是由裝在底座上的驅(qū)動電機通過 V 帶及齒輪箱來驅(qū)動的。齒輪箱使主軸的轉(zhuǎn)速有一選擇范圍,銑床有從 32r/min 到 1400r/min 的十二級轉(zhuǎn)速可供選擇。床身前面有導軌,升降臺裝在導軌上,并可沿導軌垂直運動。 升降臺 安裝在床身導軌上的升降臺,能使機床工作 臺垂直運動。 一臺獨立的電機,通過邊上的齒輪箱使升降臺實現(xiàn)機動進給,它可提供有6mm/min 到 250mm/min 的十二級進給量,驅(qū)動是通過絲桿實現(xiàn)的。絲桿的下端固定在機床的底座上。還有手動控制升降臺的裝置,這是通過前面的手輪控制絲桿和螺母來實現(xiàn)的。升降臺的頂面上有一與升降臺等寬的導軌,用來支撐床鞍,并使之作橫向運動。 鎖緊裝置可使升降臺鎖在床身任一個垂直位置上。 床鞍 裝在升降臺導軌上的床鞍,可使工作臺橫向運動。 床鞍的機動進給由升降臺上的齒輪箱提供。共有從 12mm/min 至 500mm/min的十二級進給量 。另外,用升降臺前面的手輪,經(jīng)絲桿和螺母,可實現(xiàn)床鞍的手動進給。 床鞍邊上的兩塊夾持裝置可將床鞍夾持在升降臺上。 床鞍頂面上的燕尾形導軌與升降臺導軌相垂直,可使工作臺縱向運動。 工作臺 在工作臺表面上有一組 T 形槽,可用來裝夾工件或夾具。工作臺下面的燕尾裝置在床鞍的導軌中,可使工作臺作縱向直線運動,這一運動方向與床鞍的運動方向相垂直。 工作臺機動進給是由升降臺齒輪箱通過拖板到工作臺絲杠來實現(xiàn)的。手動進給可由工作臺每一端的手輪驅(qū)動。工作臺前端的擋塊可以調(diào)整,使得每個方向上的縱向進給自動脫開。 主軸 精確地安裝在 精密軸承中的主軸,為銑刀提供驅(qū)動力。銑刀可直接安裝在主軸端部,或者安裝在刀夾裝置上,再將刀夾裝置安裝在主軸上,用一穿過主軸軸孔的牽引螺栓將 其固定在合適的位置上。銑床主軸具有標準軸端,可方便刀具或刀夾裝置的更換。軸端孔具有錐度,以便精確定位,錐角為 16 度 36 分。錐孔內(nèi)徑取決于機床的尺寸,一般為 30, 40 及 50IST(國標標準錐度)。由于其角度大,這些錐體連接(眾所周知不能自鎖)不能將運動傳到刀具或刀夾裝置上,所以用兩個鍵來傳遞動力。 懸梁及刀桿支架 臥式銑床上用的大部分刀具都是裝在刀桿上,再將刀桿固定在主軸 上的。由于所用刀桿較長,故需在其外端加上支承,以防切削時發(fā)生彎曲。支承由刀桿支架提供,該支架固定在懸梁上,懸梁安裝在床身頂部的燕尾導軌上。懸梁可隨刀桿的長度前后調(diào)整。當不需要刀桿支承時,可將懸梁全部推回去。兩個夾緊螺栓將懸梁鎖在任一位置上。刀桿支架套在懸梁的燕尾導軌上,并可用夾緊螺栓把它鎖緊在懸梁上。當?shù)稐U隨主軸轉(zhuǎn)動時,刀桿在支架的整體軸承中運轉(zhuǎn)。 臥式銑床的控制 有多種控制的典型臥式機床。這里有相同的立式機器。 心軸快速運轉(zhuǎn)是通過手柄 4經(jīng)由選擇的,并且速度是調(diào)換刻度盤 5的指示器。當機器運轉(zhuǎn)時速度不必改變, 假如是平臥的點動按鈕 3 是位于齒輪調(diào)換板的下面,當速度正在改變的時候,漸進的心軸和使齒輪滑座能夠進入一個地方。在點動按鈕旁邊開關(guān)是為控制切削液注入和心軸旋轉(zhuǎn) 2 是為了控制方向,進給速度是手柄 9 選擇的和指示流入刻度盤速度。 使從事于縱向工作臺的流入手柄 8 是移動在規(guī)定的方向,向右向左進給,可調(diào)整的擋塊 6 是規(guī)定解除進給運動,在任何用途范圍里面來回移動。限制擋塊是在最終的位置,合并的解除所有的進給運動,來阻止避免擋塊萬一受到傷害。 手柄 12 向上或向下移動,使從事于穿過或垂直移動的進給,使從事于手柄11 需要的范圍。通過移 動手柄 11 選擇向上引起大拖板進給,向下移動引起大拖板進給。 手柄 11 向上運動引起銑床升降臺的向上,向下運動引起銑床升降臺向下進給。 手柄 10 向上拉使從事于進給方向迅速來回移動。繼續(xù)向上的力運用中來回移動。當放松時,手柄將下降松開位置。選擇手動進給規(guī)定單個手動曲柄 7,向機器實施輕微的力,手動松開彈性推頂器來完成運轉(zhuǎn),為了安全目的,工業(yè)工程中,當進給或者迅速來回移動將不能快速運轉(zhuǎn),單個的手動曲柄是交換工作臺,大拖板,升降臺運動。 銑床操作 多種銑床操作可以完成銑床機器為典型的機器,切削刀具的類型和輔助設備或輔助 機構(gòu)通用的機構(gòu)。銑床用于表面光滑包括臥式,立式和角度的表面。他們是用于機器許多肩和凹槽,包括鍵槽, T 型槽和燕尾槽。以許多為明確嚙合的切削刀具為典型,他們被使用在機器明確或不規(guī)則的表面。 銑床配備有分度頭被使用于機器同樣的光滑表面,在圓柱形上有直的凹槽,螺旋凹槽,在軸上包括齒輪,絲錐,絞刀,鉆頭,銑床切削刀具和花鍵為典型。 銑床,尤其是立式銑床類型,普通的孔操作通常用鉆床進行操作。用銑床操作孔可以精確地在工作臺上設置孔的位置??v向和橫向裝配旋入用千分尺測得0.01 毫米( 0.01 英寸)或者更小??咨钜部梢酝ㄟ^垂 直調(diào)節(jié)精確地獲得尺寸。 因為操作銑床有很多種類,金屬切削是由于普通地功率和速率,它是基本機床中最重要的,它是用車床加工金屬工作中通用的和重要的。 計算機數(shù)控機床的安全和維護 1 計算機數(shù)控機床安全操作注意事項 在金屬切削操作中安全性一直是特別受關(guān)注的。由于計算機數(shù)控設備自動化程度高并且速度快,所以它是一個危險源。為了防止人員傷害和對設備的損壞,必須找出存在危險的根源,且操作人員必須提高警惕。主要的潛在危險包括:旋轉(zhuǎn)部件,如主軸,主軸內(nèi)的刀具,卡盤,卡盤里的工件,帶著刀具的轉(zhuǎn)塔刀架以及旋轉(zhuǎn)的夾具裝置;運動 部件,如加工中心的工作臺 ,車床拖板,尾架頂尖,多工序旋轉(zhuǎn)托盤;程序錯誤,例如 G00 代碼的不正確使用而引起坐標值錯誤,產(chǎn)生意想不到的快速移動;設置或改變偏移值時出錯,可能導致刀具與工件或刀具與機床之間的碰撞;隨意地更改已驗證的程序,也會引起機床產(chǎn)生危險動作。為了減少或避免危險,盡量遵循以下保護措施。 ( 1) 使用機床制造商提供的機器原有防護罩。 ( 2) 帶上安全眼鏡,手套,穿上合適的衣服和鞋。 ( 3) 不熟悉機床操作控制前不要開動機床。 ( 4) 運行程序之前,確認零件已被正確夾緊。 (
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