!257887 狄、發明說明 【發明所屬之技術領域】 法本^明係一種線切割加工機控制線張力滾輪之控制方 、匕衣置其係涉及於以電極代替刀具的切割技術領域, 鉍曰亥以放電方式達成的線切割加工機,在控制線張力滚 :對線電極⑽re electrode)的張力以及㈣穿線的方法及 裝置。 【先前技術】 按由線切割加工機係由放電極給線電極的方式來代替 2具,讓線電極對工件進行線切割,因此線電極在循環當 中會由出線滾輪繞經線張力滾輪,再縱下穿過上、下機頭 而工件即是位於上、下機頭之間,線電極穿過下機頭再 入後收線滾輪組,後收線滾輪組並為一後收線馬達提供 收的動力。而線張力滾輪在線切割進行時,會提供 向:朝後收線滾輪組送線的扭力,藉以提供線電極的張力 來^電^不慎斷而需重新自動穿線’則又由線張力滾輪 來k線’讓線電極重新穿線。 目前所知’美國帛5,422,454號專利案,1 =張力滚輪連結的煞車制動器,及一顆驅動馬達 丁 r…、車制動态對線張力滾輪形占 對線電極產生張力,如果加工中斷線輪=:= 線#作下,停止煞車制動器的煞車力,由連桿:牙 而將線張力滾輪與煞車制動干、冓之切換 動錢離亚與驅動馬達連結, 1257887 再啟動該馬達來帶動線張力滾輪執行送線的動作 穿線完成,又需切換連桿機構來重新連接煞車制動=自動 此該美國專利案揭示複雜的連桿機構,以及需 ^因 合器裝置來分別帶動線張力滾輪不同狀態動作,離 製造成本高,而且機械式切換的時間,無料低^ = 工機的作業效率。 加 【發明内容】 本發明者有鑑於前述揭露線切割加工機在線張 的張力以及自動穿線的控制設計仍然存在需要改善的/問^ ,因此重新設計出-種線切割加卫機之控制線張力滾輪方 法及其裝置’尸、需乙只伺服馬達以及控制裝置,利用輸出 不同的驅動模式’來達到線張力滾輪在提供線張力與自』動 穿線的切換之間,完全無機械式動作以及切換時間,並降 低使用的動力成本,大幅提昇作業效率,&為其主要創作 目的。 為了可達到前述的創作目的,本發明所運用的技術手 段係在於提供一種線切割加工機控制線張力滾輪之控制方 法,其動作包含有: (1)由線張力控制裝置偵測線電極是否處於斷線,若 為斷線則判斷為斷線需穿線狀態,反之判斷為正常切割狀 態; (2)當為斷線需穿線狀態而欲進行穿線時,線張力控 制裝置輸出電子信號型態的命令將伺服馬達之控制模式切 換為位置控制模式,由伺服馬達帶動線張力滾輪主動送線 1257887 ,使線穿過上機 (3) ^ ; 件、下機頭而至後收線輪組; ,線張力控制梦箸仏山 丨測到線已到達後收線輪組時 控制模式切換為扭力控制模/^的命令將㈣馬達之 輪與後收線钯^ 4工、工使伺服馬達帶動線張力滾 交叹琛驅動馬達相互配合 力,完成穿線動作,並〇/1 電極f有-設定之張 ,回设為正常切割狀態。 為可達到前述目的,本發 提供一種線切$,丨Λ ^ " 運用的技術手段進一步 nτ刀割加工機 俜包#· 工制線張力滾輪之控制裝置,其 一出線滾輪,提供線雷十 極; 、、'、電極之來源,使其穩定供給線電 :線張力滾輪,用以供線電極圍繞轉動; 力^=馬彡’與線張力滾輪機械連結,用以驅動線張 力滾輪u,或者是提供反向扭力於線張力滚輪; 一設有線切斷器的線頭挾持裝置,用以切除廢線; 冑員及了機頭’兩者之間保持有-可供工件安 置的距離; -後收線輪組’係由—後收線驅動馬達驅動,用以帶 動線電極’使後收線輪組能拉動線電極經過所需的路徑, 亚可與線張力滾輪配合而施以線電極一設定之張力; -線張力控制裝置’連接伺服馬達,可判斷線電極斷 線與否’若線電極未斷,後收線滾輪組可以正常收到由出 線滾輪而來的線電極時,並且線張力滾輪由線張力控制裝 置切換飼服馬達為扭力控制模式,使線張力滾輪與後收線 1257887 輪組配合而提供線電極一設定張力,若線電極已 ,則線 張力滾輪由線張力控制裝置切換伺服馬達為位置控制模 ,線張力滾輪主動送線,做穿線之動作。 卫果"、 本發明可以獲得的功效,主要係改變以往機械式切換 的機構設計,由、線張力㈣裝置们則線切割加卫機是處於 常態加工,送出扭力控制模式的電子訊號給饲服馬 其對線張力滚輪施以扭力大小的命令量,使線張力滾輪對 =極施作張力,而當工作中斷線情形,線張力滾輪“ :由線張力控制裝置偵測得知,$出位置控 ; :號W令其以指定到達-設置位置的命令: 線張力滾輪以反向於線張力的轉向,提供自 極的穿線功能,在成功確定到達後收線驅動㈣ 立即自動切換為扭力控制模 、 捭祉& ^7綠張力滾輪回復到正常 & L張力狀態;因此本發 雜的月免耗械式切換的時間以及複 輪依線切割加工擔ρ ^ 思术徑制線張力滾 d加工機狀悲自動切換;並且只 ,較諸以往需I民呰施人 而,、伺服馬達 ,^ 要馬達離合器及複雜機構動作切換的讯呻 本發明節省更多動力能源mu*刀換的❹十 【實施方式】 以及動力成本,深具實用性。 本發明係—種線切割加工機之和制錄往+ ώ 其裝置,工機之控制線張力滾輪方法及 力滾輪在正^ α本纟日月的方法,主要係線張 … 书、、、切割加工時,由線張力控制裝置(2 〇 ) 运出切換控制的雷子H 市』衣置(2 0 ) 裝置( 。^,该電子信號係依據線張力控制 偵測線切副加工的狀態,來切換為扭力控制 8 1257887 模式,將其電子信號傳遞給伺服馬達(2 2 ),由伺服馬 達(2 2 )控制線張力滾輪(3 〇 )對線電極(5 〇 )執 行相反於穿線方向轉動的張力作用,反之,如工作中斷線 ,而需重新穿線時,線張力控制裝置(2 〇 )則送出切換 控制信號,則送出位置控制模式送出信號,命令伺服馬達 (2 2 )讓線張力滾輪(3 〇 )朝穿線方向來進給,執行 自動穿線到收線處。接下來便對實施本發明的具體裝置, 以及以裝置來實施方法的流程以一較佳實施來說明。 如第一至二圖,本發明之裝置係設置一供線電極(5 0 )捲繞的出線滾輪(丄〇 ),讓線電極(5 〇 )往上經 由第一導輪(1 2 )轉折,繞至線張力滾輪(3 〇 ),位 於線張力滾輪(3 〇 )鄰側設有一第二導輪(丄2丄), 前述線張力滾輪(3⑹係受到—包含㈣馬達(2 2 ) 的線張力控制裝置(20)來控制驅動,由線張力控制裝 ,(二)叙出切換控制信號的電子裝置,線張力控制裝 =〇)係電連接到-飼服馬達(22),飼服馬達( 2)又電連接一位置回授 F晋Γ 9 /1、^、 衣置(2 4 ),透過位置回授 為杈式命令的切換訊息接收裝置,用以扭 力控制模式,及位置 .^ 制极式之閉迴路回授控制信號,囔 線張力控制裝置(20)可對伺服 =讓 2%)、^ 制模式或速度控制模式,㈣服馬達( 線線張力滾輪(3 0 )的動作;以及 位於線張力滾輪(3 〇 ) 0 )依序貫穿過^ 糸往下供線電極(5 序貝牙過-包含線切斷器(42)的線頭夹持裝置 !257887 與上機頭(4 4 ) 4 Ο ),以及一上機頭(4 4 ) 保持一供工件(6 0 )安置距離的下 下機頭(4 6 )之下係供線電極(5員:6 ’位於 (1 2 2 ),讓線電極(5 〇 ) *第:、、.繞㈣第三導輪 入後收線滾輪組(4 7),後收線滾輪纽“7 : 後收線驅動馬達(4 8 )驅動收線動作。 故而依照本發明的裝置在實施時, 一 ’當工件(60)置於上、下機頭( 四圖 定位以後,線電極(…㈣出線滾:(;心:: 穿到後收線滾輪組(47),便對線電極(5〇)放^ 極開始對工件(6 0 )加工,而該正當 Λ止吊加工訊息,讓線 力控制裝Η 2 0)放出切換㈣信號—扭力控制模式給 伺服馬達(2 2 ),由伺服馬達(2 俄如备 (30)以反向於進給線電極(5〇)方向的穩定扭力, 提供線電極(5 0 ) —線張力; 如果工作中偵測到線電@ ( 5 〇 )斷線如第一、三圖 ,則會啟動線頭夾持裝置(4 〇 )來夾住斷掉的線頭,: 再由線切斷器(42)來對切斷線電極(50),而廢線 回收機構〔圖中未示〕會將線頭夾持裝置(4 0)以下的 廢線收回,使上機頭(44)與卫件(6 0)1的廢線清 理完成後’線張力控制裝置(2 0)彳以脈衝訊息來作開 迴路位置控制’切換到位置控制模式,改變飼服馬達(2 2 )帶動線張力滾輪(3 〇 )設定線電極(5 0 )進給到 後收線滾輪組(4 7 )位置的指令,讓飼服馬$ ( 2 2 ) 10 1257887 驅動線張力滾輪(3 Ο )以朝向線電極(5 〇 )進給方向 ,引導線頭貫穿上機頭(4 4 )'下機頭(4 6 )進入後 收線滾輪組(4 7 )遇到後收線驅動馬達(4 8 )即停止 〔该方式係可以在收線驅動馬達位置設置限位開關,當線 電極觸及限位開關便停止〕; 當線電極(5 0 )由後收線驅動馬達(4 8 )帶動時 ,線張力控制裝置(2 0 )们則及此,又切換到輪出扭力 控制模式的信號,讓伺服馬達(2 2 )切換為扭力控制模 式,讓線張力滾輪(3 0 )形成反向於線電極(5 〇 )進 給方向的-固定扭力’對線電極(5 〇 )有穩定的線張力 ’使後收線驅動馬達(4 8 )為主動狀態,伺服馬達(2 2 )切換為扭力控制模式而為被動狀態;前述線張力控制 裝置(2 0 )的位置控制模式如第一圖所示,是可以扭力 命令、位置命令、速度命令為之,其中叫立置命令與扭力 命令是可以脈衝式訊息的命令來下給伺服馬達(22), 如第二、四圖所示則係位置控制模式完全使用扭力命令, 當線電極(5 0 ) if線時’線張力滚輪(3 〇 )送、"線 採以扭力命令,直到位置回授裝£ ( 2 4 )偵測回授量改 變’在確U線成功後’伺服馬丨(22)便停止位置控 制模式而切換回到扭力控制模式;復如第^、五圖所示, 當線電極斷線時,、線張力滾輪(3 〇 )送線穿線如採以位 置命令者,則在線電極位置到達後收線滾輪組(4 7 ), 再由位置回授裝置(24)们則回授量改變,當確定穿線 成功後,祠服馬達(22)便停止位置控制模式而切換回 1257887 到扭力控制模式,·同理’速度命令 式流程相@,差異僅在於㈣力滾輪^圖的位置命令模 係使用速度命令,前述速度命令的=在送線穿線 (2 4 )來作閉迴路控制,傳達給伺服馬達(2 2广 使其透過速度命令的閉迴路位置控制的設定,來引導線張 力滾輪(3 0 )進給到後收線驅動馬達(4 8 ) ’達成穿 線成功目的。!257887 Di, invention description [Technical field of invention] Law Ben ^ Ming is a wire cutting machine control line tension roller control side, the clothing is related to the cutting technology field with electrodes instead of tools, A wire-cutting machine that is realized by a discharge method, a control wire tension roller: a tension on a wire electrode (10), and a method and a device for threading. [Prior Art] In place of the wire cutting machine, the wire electrode is used to replace the two wires, and the wire electrode is used for wire cutting the workpiece. Therefore, the wire electrode is wound by the wire roller around the warp tension roller during the cycle. Then pass the upper and lower heads vertically and the workpiece is located between the upper and lower heads. The wire electrode passes through the lower head and re-enters the take-up roller set. The rear take-up roller set is a rear take-up motor. Provide the power to receive. When the wire tension roller is cut in the line, it will provide the torque to the wire feeding line of the backward take-up roller group, so as to provide the tension of the wire electrode, the wire is inadvertently broken and needs to be automatically threaded again, and then the wire tension roller is used. The k line 'let the wire electrode re-thread. Currently known as 'U.S. Patent No. 5,422,454, 1 = brake brake connected by tension roller, and a drive motor D..., the dynamic tension of the wire on the wire takes up tension on the wire electrode, if the machining breaks the wire =:= Line # is done, stop the brake force of the brake, and connect the line tension roller and the brake to the brake by the connecting rod: the tooth, and switch the money to the drive motor. 1257887 Then start the motor to drive the line. The tension roller performs the threading action to complete the threading, and the link mechanism needs to be switched to reconnect the brake. = This automatic US patent case reveals a complicated linkage mechanism, and the device needs to be driven to respectively drive the wire tension roller to different states. Action, high cost of manufacturing, and mechanical switching time, no material low ^ = work efficiency of the machine. SUMMARY OF THE INVENTION The present inventors have re-designed the control line tension of the wire cutting and cultivating machine in view of the above-mentioned disclosure that the tension of the wire cutting machine and the control design of the automatic threading still need to be improved. The roller method and its device 'corpse, need only servo motor and control device, use different output drive mode' to achieve the line tension roller between the line tension and the self-moving thread, no mechanical action and switching Time, and reduce the cost of power used, greatly improve the efficiency of the work, & for its main creative purposes. In order to achieve the above-mentioned creative purpose, the technical means used in the present invention is to provide a wire cutting machine control line tension roller control method, the action thereof comprises: (1) detecting whether the wire electrode is in the line tension control device If the wire is broken, it is judged that the wire is broken and the thread is in the normal cutting state. (2) When the wire is broken and the thread is to be threaded, the thread tension control device outputs the electronic signal type command. Switching the control mode of the servo motor to the position control mode, the servo motor drives the wire tension roller to actively feed the wire 1257887, so that the wire passes through the upper machine (3) ^; the lower part and the lower take-up wheel set; Tension control nightmare mountain 丨 丨 丨 丨 丨 丨 丨 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制 控制The sigh drive motor cooperates with each other to complete the threading action, and the 〇/1 electrode f has a set-up sheet and is set back to the normal cutting state. In order to achieve the foregoing objectives, the present invention provides a wire cutting $, 丨Λ ^ " technical means for further nτ knife cutting machine 俜 Bao #· industrial line tension roller control device, an outlet roller, providing a line Ray ten pole; , , ', the source of the electrode, make it stable supply line power: wire tension roller for the wire electrode to rotate around; force ^= horse 彡 ' mechanical connection with the line tension roller, used to drive the line tension roller u, or provide reverse torque to the wire tension roller; a wire head holding device with a wire cutter for cutting the waste wire; the employee and the nose 'between the two - for the workpiece to be placed The distance--rear take-up wheel set is driven by the rear take-up drive motor to drive the wire electrode 'to enable the rear take-up wheel set to pull the wire electrode through the required path, and the sub-coil can be combined with the wire tension roller The tension is set by the wire electrode; - the wire tension control device is connected to the servo motor to determine whether the wire electrode is broken or not. 'If the wire electrode is not broken, the rear wire roller group can normally receive the wire from the wire roller. Electrode and wire tension roller The wire tension control device switches the feeding motor to the torque control mode, and the wire tension roller cooperates with the rear winding 1257887 wheel set to provide a set tension of the wire electrode. If the wire electrode is already, the wire tension roller is switched by the wire tension control device. The motor is a position control mode, and the line tension roller actively feeds the wire to perform the threading action. Weiguo", the effect that can be obtained by the present invention is mainly to change the mechanical design of the mechanical switching in the past, and the line tension (four) devices are the wire cutting and adding machine, which is in the normal state processing, and the electronic signal feeding mode of the torque control mode is fed. Ma’s command amount of torque applied to the line tension roller is such that the tension of the line tension roller is applied to the pole, and when the line is broken, the line tension roller is detected by the line tension control device. Out position control; : No. W to make it the command to specify the arrival-set position: The line tension roller provides the self-polar threading function with the steering thread reversed from the line tension. After the successful determination, the line-receiving drive (4) automatically switches to The torque control mode, 捭祉 & ^7 green tension roller returns to the normal & L tension state; therefore, the time of the month-free and labor-free switching of the hybrid and the double-wheel-cut processing The tension roll d machine automatically switches between the sorrows; and it only saves more movements than the previous ones, the servo motor, the motor clutch and the complicated mechanism action switching. The power consumption mu* knife change ❹10 [implementation method] and the power cost, and has practicality. The invention is a method for the production of a wire cutting machine and a device for controlling the tension roller of the machine. The method of the force roller in the positive and negative times of the day, the main line of the line... When the book is processed, the line tension control device (2 〇) is shipped out of the control of the Leizi H City. The device (., the electronic signal is based on the line tension control to detect the state of the line cutting sub-machining, to switch to the torque control 8 1257887 mode, and transmit its electronic signal to the servo motor (2 2 ), by the servo motor (2) 2) The control line tension roller (3 〇) performs the tension action on the wire electrode (5 〇) opposite to the threading direction. Conversely, if the work breaks the line and needs to re-thread, the thread tension control device (2 〇) When the switching control signal is sent, the position control mode sends a signal, and the servo motor (2 2 ) is commanded to feed the wire tension roller (3 〇) in the threading direction, and automatic threading is performed to the take-up position. Next, the present invention is implemented. Specific The flow of the method and the method for implementing the method is described in a preferred embodiment. As shown in the first to second figures, the device of the present invention is provided with a wire take-up roller (丄〇) for winding the wire electrode (50). Let the wire electrode (5 〇) turn up through the first guide wheel (1 2 ), and wrap it around the line tension roller (3 〇). There is a second guide wheel on the adjacent side of the line tension roller (3 〇). The wire tension roller (3 (6) is controlled by a wire tension control device (20) including a (four) motor (2 2 ), and is controlled by a wire tension control device, and (2) an electronic device that switches a control signal, and a wire tension Control device = 〇) is electrically connected to the feeding motor (22), and the feeding motor (2) is electrically connected to a position to return the F Γ 9 / 1, ^, clothing (2 4), through the position feedback The switching message receiving device for the 杈-type command is used for the torque control mode, and the position of the closed-loop feedback control signal of the pole type, and the tension control device (20) can be used for the servo=2%) Mode or speed control mode, (4) service motor (line tension roller (3 0) action; and located in line Zhang Roller (3 〇) 0) sequentially through the ^ 糸 down supply line electrode (5 order shell teeth over - line cutter (42) line head clamping device! 257887 and upper head (4 4) 4 Ο ), and an upper head (4 4 ) to hold a lower supply head (4 6 ) for the workpiece (60) to be placed below the supply line electrode (5 members: 6 ' located at (1 2 2), Let the wire electrode (5 〇) *::,, around (four) the third guide wheel into the rear take-up roller set (4 7), the rear take-up roller button "7: the rear take-up drive motor (4 8) drive the take-up line action. Therefore, when the device according to the present invention is implemented, a 'when the workpiece (60) is placed on the upper and lower heads (after the four images are positioned, the wire electrodes (...) are rolled out: (; heart:: to the rear take-up roller Group (47), the wire electrode (5〇) is placed on the workpiece to start machining the workpiece (60), and the proper operation is to stop the processing information, so that the line force control device 2 0) release switching (four) signal - torque control The mode is given to the servo motor (2 2 ), and the servo motor (2) is provided with a stable torque in the direction opposite to the feed wire electrode (5〇), and the wire electrode (50) is provided. If the line power @ ( 5 〇) disconnection is detected, such as the first and third diagrams, the thread clamp (4 〇) will be activated to clamp the broken thread: The wire electrode (50) is cut off, and the waste wire recovery mechanism (not shown) retracts the waste wire below the wire holding device (40), so that the upper head (44) and the guard ( 6 0) 1 After the waste line cleaning is completed, 'Line tension control device (2 0) 彳 pulse signal for open loop position control' switch to position control mode, change the feeding motor (2 2 ) Drive the wire tension roller (3 〇) to set the position of the wire electrode (5 0 ) to the position of the rear take-up roller set (4 7 ), and let the feeding horse $ ( 2 2 ) 10 1257887 drive the line tension roller (3 Ο ) In the direction of feed toward the wire electrode (5 〇), the guide wire thread runs through the upper head (4 4 )' lower head (4 6 ) and enters the rear take-up roller set (4 7 ) to encounter the rear take-up drive motor (4 8) Stop [This mode can set the limit switch at the position of the take-up drive motor, and the line electrode will stop when it touches the limit switch]; When the line electrode (5 0 ) is driven by the rear take-up drive motor (4 8 ) Then, the line tension control device (20) switches to the signal of the torque control mode, and the servo motor (2 2 ) is switched to the torque control mode, so that the line tension roller (30) is reversed. The wire electrode (5 〇) feed direction - fixed torque 'has a stable wire tension on the wire electrode (5 〇)' makes the rear take-up drive motor (4 8 ) active, and the servo motor (2 2 ) switches to torque The control mode is passive; the position control mode of the aforementioned line tension control device (20) is as shown in the first figure. As shown, it can be a torque command, a position command, a speed command, wherein the stand command and the torque command are commands that can be pulsed to the servo motor (22), as shown in the second and fourth figures. The position control mode uses the torque command completely. When the line electrode (5 0 ) is the line, the 'line tension roller (3 〇) is sent, and the line is torque commanded until the position feedback is loaded (2 4 ) detection feedback. The quantity change 'After the U line is successful', the servo horse (22) stops the position control mode and switches back to the torque control mode; as shown in Fig. 5 and Fig. 5, when the wire electrode is broken, the wire tension roller (3 〇) If the wire feeding thread is taken by the position commander, the wire electrode position will reach the rear wire roller group (4 7 ), and then the position feedback device (24) will change the feedback amount. When it is determined that the threading is successful, The motor (22) stops the position control mode and switches back to the 1257887 to the torque control mode. The same reason is the 'speed command type flow phase@. The only difference is that the position command mode of the force roller is used. Speed command = in the delivery line (2 4 ) The closed loop control is transmitted to the servo motor (2 2 wide to make the setting of the closed loop position control of the speed command to guide the line tension roller (30) to feed to the rear take-up drive motor (4 8) 'Achieve the purpose of threading successfully.
12 1257887 【圖式簡單說明】 (一)圖式部分 第一圖:係本發明控制驅動的流程方塊圖。 第二圖··係本發明在正常加工的整體配置示意圖。 第三圖··係本發明在斷線狀態的整體配置示意圖。 第四圖··係本發明在位置控制模式完全使用扭力命令的流 程方塊示意圖。 第五圖:係本發明在位置控制模式中使用位置命令的12 1257887 [Simple description of the diagram] (1) Schematic part The first diagram is a block diagram of the control drive of the present invention. The second figure is a schematic diagram of the overall configuration of the present invention in normal processing. The third figure is a schematic diagram of the overall arrangement of the present invention in the disconnected state. The fourth figure is a flow block diagram of the present invention in which the torque command is completely used in the position control mode. Figure 5: The use of position commands in the position control mode of the present invention
方塊不意圖。 (二)元件代表符號 (1 〇 )出線滾輪 (1 2 1 )第二導輪 (2 0 )線張力控制裝置 (24)位置回授裝置 (3 0 )線張力滾輪 (4 0 )線頭夾持裝置 (4 4 )上機頭 (4 7 )後收線滾輪組 (5 0 )線電極 (6 0 )工件 (12)第一導輪 (1 2 2 )第三導輪 (2 2 )伺服馬達 (4 2 )線切斷器The block is not intended. (2) Component symbol (1 〇) Outlet roller (1 2 1) Second guide wheel (20) Line tension control device (24) Position feedback device (3 0) Line tension roller (4 0) Clamping device (4 4 ) on the head (4 7 ) rear take-up roller set (5 0 ) line electrode (60) workpiece (12) first guide wheel (1 2 2) third guide wheel (2 2 ) Servo motor (4 2 ) wire cutter
(4 6 )下機頭 (4 8 )後收線驅動馬達 13(4 6) Lower head (4 8 ) Rear take-up drive motor 13