Abstract:
A multi-spindle CNC lathe comprises a frame assembly mounted on a base and including spaced apart, rigidly interconnected subframes defining spaced, parallel alignment surfaces. A plurality of spindles each includes a collet for rotating a stock about a spindle axis. An indexing mechanism positions the spindles in alignment with stations located at equally spaced intervals about a central axis. Internal tool slides mounted on the alignment surface of one of the subframes each comprise a servo mechanism for advancing and retracting a cutting tool along a work station axis. External tool slides mounted on the alignment surface of the other subframe each comprise a first servo mechanism for advancing and retracting a cutting tool toward and away from the work station axis and a second servo mechanism for selectively moving the cutting tool back and forth along a path extending parallel to the work station axis.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 09/740,360 filed Dec. 19 , 2000, currently pending, which is a continuation of application Ser. No. 09/557,279 filed Apr. 24, 2000, now U.S. Pat. No. 6,164,173, which is a continuation of application Ser. No. 09/283,595 filed Apr. 1, 1999, now abandoned, which is a continuation of application Ser. No. 09/044,353 filed Mar. 19, 1998, currently abandoned, which is a continuation of application Ser. No. 08/869,047 filed Jun. 4, 1997, now U.S. Pat. No. 5,918,514, which is a continuation of application Ser. No. 08/514,734 filed Aug. 14, 1995, now U.S. Pat. No. 5,676,030. 
    
    
     TECHNICAL FIELD 
     This invention relates generally to machine tools, and more particularly to a multi-spindle CNC lathe that is particularly adapted for use in conjunction with JIT and SPC manufacturing philosophies. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     Machine tools, including drills, lathes, milling machines, grinders and other finishing machines, are all characterized by a common objective: the manufacture of extreme accuracy and maximum economy. As such, interest in and development of machine tools has paralleled the advance of the industrial revolution. 
     Traditionally, machine tools were operated by machinists who were among the most highly skilled and the most highly paid of all workers. More recently, however, machine tools have been adapted to a procedure known as computer numeric control, or CNC, whereby the operation of machine tools is regulated by computers or other programmable controllers. In accordance with the CNC technique, the dimensions, surface finishes, and other characteristics of the part to be manufactured are supplied in the form of sequential operating instructions which are utilized by the CNC device to regulate the operation of the machine tool. This allows the completion of finished parts with more uniformity and more rapidity than has ever been possible heretofore. 
     The adaptation of single spindle lathes, milling machines, and similar devices to CNC techniques has largely been successful. However, in the case of multi-spindle machine tools, previous attempts at automation have largely comprised adapting the cams, gears, and other components comprising such machines to servo control. Perhaps because the approach has been one of adapting old designs to new techniques, the effort to date at automating the operation of multi-spindle lathes by means of CNC operation has largely been unsuccessful. 
     The present invention comprises a multi-spindle lathe which is entirely adapted for CNC operation. In accordance with the broader aspects of the invention, a plurality of spindles are positioned at spaced points about a central axis. Each spindle has a collet which receives a length of stock and rotates the stock about a spindle axis. An indexing mechanism is provided for selectively positioning the spindles at work stations located at equally spaced points about the central axis. Each work station comprises an internal tool slide adapted to receive a cutting tool and to advance the cutting tool toward and away from the rotating stock under the action of a servo mechanism. An external tool slide is also provided for each work station and is adapted to advance a cutting tool both toward and away from and parallel to the axis of rotation of the stock. At each work station the stock is turned rather than formed, meaning that the cutting tools of the individual work stations may be utilized to perform a variety of quite distinct machining operations. 
     The multi-spindle CNC lathe of the present invention is readily adapted for use in conjunction with both the Just In Time (JIT) and the Statistical Process Control (SPC) manufacturing philosophies. In accordance with JIT, only the exact No. of piece parts necessary to complete a particular assembly operation are ordered at any one time. This eliminates the investment in inventory which is necessary when large numbers of piece parts are ordered simultaneously, and also eliminates the possibility that previously ordered parts will become obsolete due to a change in design. The machine tool of the present invention is adapted to JIT because the economic batch is smaller. This is because machine tools incorporating the invention do not require the changing of the cutting tools utilized at the various work stations in order to change the nature of the piece parts being manufactured, and because set up time is reduced dramatically. 
     In accordance with SPC, completed piece parts are compared with a predetermined standard with a view towards maintaining the dimensions of each part at the center of the tolerance range. If the dimensions of the parts being manufactured begin to vary from the center of the tolerance 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the invention may be had by reference to the following Detailed Description, when taken in conjunction with the accompanying Drawings wherein: 
     FIG. 1 is a front view of a multi-spindle CNC lathe incorporating the present invention; 
     FIG. 2 is a front view of the base of the multi-spindle CNC lathe of FIG. 1 in which certain parts have been broken away more clearly to illustrate certain features of the invention; 
     FIG. 3 is a top view of the base of FIG. 2; 
     FIG. 4 is a longitudinal sectional view illustrating the frame and certain operating components of the multi-spindle CNC lathe of FIG. 1; 
     FIG. 5 is an enlargement of a portion of FIG. 4; 
     FIG. 6 is a front view of the multi-spindle CNC lathe of the present invention similar to FIG. 1 in which the covers of the apparatus have been removed; 
     FIG. 7 is an illustration of certain components of the multi-spindle CNC lathe of FIG. 6 taken along the line  7 — 7  of FIG. 6; 
     FIG. 8 is an illustration of certain components of the multi-spindle CNC lathe of FIG. 6 taken along the line  8 — 8  in FIG. 6; 
     FIG. 9 is an enlargement of a portion of FIG. 8; 
     FIG. 10 is a further illustration of certain components shown in FIG. 9; 
     FIG. 11 is a side view of one of the internal slide assemblies of the multi-spindle CNC lathe of FIG. 6 in which certain components have been broken more clearly to illustrate certain features of the invention; 
     FIG. 12 is an illustration of certain components of the multi-spindle CNC lathe of FIG. 6 taken along the line  12 — 12  of FIG. 6; 
     FIG. 13 is an illustration of one of the external slide assemblies of the multi-spindle CNC lathe of the present invention; 
     FIG. 14 is a sectional view taken along the line  14 — 14  of FIG. 13; 
     FIG. 15 is a sectional view taken along the line  15 — 15  of FIG. 14 further illustrating the external slide assemblies of the multi-spindle CNC lathe of the present invention; 
     FIG. 16 is longitudinal sectional view further illustrating the external slide assemblies of the multi-spindle CNC lathe of the present invention; 
     FIG. 17 is a sectional view taken along the line  17 — 17  of FIG. 13; 
     FIG. 18 is an enlargement of a certain portion of the apparatus illustrated in FIG. 17; 
     FIG. 19 is an illustration of certain of the components of the multi-spindle CNC lathe of the present invention taken along the line  19 — 19  of FIG.  6 . 
     FIG. 20 is an illustration of one of the spindles of the multi-spindle CNC lathe of the present invention showing the component parts thereof in a first orientation; 
     FIG. 21 is view similar to FIG. 20 showing the component parts of the spindle in a second orientation; 
     FIG. 22 is an illustration similar to FIG. 20 showing the component parts thereof in a third orientation; 
     FIG. 23 is a sectional view illustrating the glut actuator of the multi-spindle CNC lathe of the present invention; 
     FIG. 24 is a sectional view taken along the line  24 — 24  of FIG.  25  and illustrating the spindle carrier of the multi-spindle CNC lathe of the present invention; 
     FIG. 25 is an end view of the spindle carrier of the multi-spindle CNC lathe of the present invention; 
     FIG. 26 is an enlarged illustration of one of the castings comprising the frame of the present invention; 
     FIG. 27 is an illustration of the one of the stock carrying tubes of the multi-spindle CNC lathe of the present invention; 
     FIG. 28 is an enlarged sectional view further illustrating the stock carrying tubes of the multi-spindle CNC lathe of the-present invention; 
     FIG. 29 is a front view illustrating the stock carriage assembly of the multi-spindle CNC lathe of the present invention; 
     FIG. 30 is a partial sectional view illustrating the indexing mechanism of the multi-spindle CNC lathe of the present invention; 
     FIG. 31 is a partial sectional view illustrating a tool holder accessory useful in conjunction with the multi-spindle CNC lathe of the present invention; 
     FIG. 32 is a further illustration of the three point mounting system of the frame of the multi-spindle CNC lathe of the present invention; 
     FIG. 33 is a still further illustration of the three point mounting system of the frame of the multi-spindle CNC lathe of the present invention; 
     FIG. 34 is a perspective view illustrating the operation of the multi-spindle CNC lathe of the present invention; and 
     FIG. 35 is a perspective view further illustrating the operation of the multi-spindle CNC lathe of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring now to the Drawings, and particularly to FIG. 1 thereof, there is shown a multi-spindle CNC lathe  50  incorporating the present invention. The lathe  50  includes a base  52  which also serves as a coolant reservoir. A housing  54  extends upwardly from the base  52  and serves to enclose and protect both the mechanical components and the production components of the multi-spindle CNC lathe  50 . 
     A computer numeric control (CNC) system  56  is located at one end of the housing  54 . The CNC system  56  is preferably of the type sold by General Electric Company as and identified by that company as the Power Mate Motion Control Systems, and may include a computer monitor screen  58  and/or a plurality of status lights  60 . A keyboard  62  may be used to effect computer control over the operation of the lathe  50 . The CNC unit  56  may further include a conventional control panel  64 . 
     The housing  54  of the multi-spindle CNC lathe  50  further includes a sliding access door  66 . The door  66  is slidably supported on a slideways  68  and is provided with a viewing window  70 . The production components of the multi-spindle CNC lathe  50  are located behind the door  66  when it is in the closed position as illustrated in FIG. 1, and are observable through the viewing window  70  thereof. 
     A hinged door  72  provides access to the mechanical components of the lathe  50 . Access ports  74  are normally enclosed by removable covers  76 . A cover  78  enclosing the stock carriers of the lathe  50  extends leftwardly (FIG. 1) from the main portion of the housing  54 . 
     Referring now to FIGS. 2 &amp; 3, the base  52  of the multi-spindle CNC lathe  50  is shown in greater detail. The base  52  is comprised entirely of steel plates which are interconnected by welding. The base  52  is provided with a plurality of mounting blocks  80  and a plurality of mounting holes  82  which function to attach the operating components of the lathe  50  to the base  52 . 
     In addition to supporting and locating the operating components of the lathe  50 , the base  52  serves as a coolant reservoir. Coolant entering the base  52  is initially contained by a plate  84  which defines a coolant level  86 . Chips caused by operation of the multi-spindle CNC lathe  50  enter the base  52  through a port  88  and are received on a chip conveyor  90  located above the plate  84 . The conveyor  90  transports the chips out of the base  52 , whereupon the chips fall into a chip receiving container  92  under the action of gravity. 
     During operation of the lathe  50 , coolant constantly flows over a lip  94  located at′ one end of the plate  84 . From the lip  94  the coolant flows into and through a basket  96  which functions to strain the coolant, thereby removing any debris which is not transported out of the base  52  by the chip conveyor  90 . Preferably, two baskets  96  are employed in the operation of the lathe, one located in the working position as defined by a bracket  98  and the other positioned on a drain platform  100  which allows coolant to drain out of the basket  96  prior to the removal of debris therefrom. Coolant flowing through the basket  96  located in the working position as defined by the bracket  98  flows along a path defined by the arrows  102  and is returned to the operating components of the lathe  50  by a pump (not shown) which withdraws the coolant from the base at aperture  103 . This flow path maintains a uniform temperature of the base  52  and eliminates static spots which can cause the coolant to become rancid. 
     As is best shown in FIG. 4, the multi-spindle CNC lathe  50  includes a frame  104  comprising an important feature of the invention. The frame  104  includes precision castings  106  and  108  which function to support and align the operating components of the lathe  50 . The casting  106  comprises opposed walls  110  and  112 , and the casting  108  comprises opposed walls  114  and  116 . 
     The walls  110  and  112  of the casting  106  define opposed surfaces  120  and  122 , respectively. The surfaces  120  and  122  are ground flat and smooth utilizing Blanchard grinding or a functionally equivalent process. The same procedure assures precise parallelism between the surfaces  120  and  122 . The-walls  114  and  116  comprising the casting  108  define opposed surfaces  124  and  126  which are identically processed, and are therefore equally flat, smooth, and parallel. The surfaces  122  and  124  define the alignment surfaces of the frame  104  of the lathe  50 . 
     The frame  104  further comprises four tie rods  128  which are match machined in order to maintain precise parallelism between the surface  122  of the casting  106  and the surface  124  of the casting  108 . Each tie rod  128  includes an elongate central portion  130  extending to reduced diameter portion  132  which in turn extends to a threaded end member  134 . At the bottom of the casting  108 , a bushing  136  is mounted on each reduced diameter portion  132  and is received in aligned apertures  138  formed in the casting  108  and an aperture  140  formed in a mounting block  142 . 
     A plurality of nuts  144  are each threadedly engaged with a threaded end portion  134  of one of the tie rods  128 . The nuts  144  engage washers  146  which in turn engage compression members  148 . Thus, upon precise tightening of the nuts  144 , using, for example, a torque wrench, the castings  106  and  108  comprising the frame  104  are securely positioned with respect to one another. 
     At the upper ends of the castings  106  and  108 , and at the lower end of the casting  106 , the reduced end portions of the rods  128  extend through apertures  138 ′ formed in the castings  106  and  108 . Likewise, the nuts  144  engage the washers  146  which directly engage the castings  106  and  108 . 
     The casting  106  is supported on a mounting block  142 , which bridges across the base  52  and is supported by the mounting blocks  80  thereof. 
     The mounting blocks  142  and  142 ′ are secured to the base  52  by a plurality of threaded fasteners  152 . The mounting blocks  142  engage the mounting blocks  80  of the base  52  to precisely position the frame  104  with respect thereto. An important aspect of the present invention comprises the use of the three point mounting system comprising the two mounting blocks  142  and  142 ′ to mount the frame  104  on the base  52 . By this means any possibility of tipping, wobbling, or misalignment between the base  52  and the frame  104  is eliminated. 
     The three point mounting system which supports the frame  104  on the base  52  is further illustrated in FIGS. 32 and 33. Each mounting block  142  engages an individual mounting block  80  of the base  52  to support the casting  108  at two parts. In contrast, the mounting block  142 ′ bridges between two mounting blocks  80  and supports the casting  106  at a single, central point, thereby providing three point support for the frame  104 . A pin  150  extends through aligned apertures  138  in the casting  106 , and an aperture  103  formed in the center of the mounting block  142 ′. A nut  144  is threadably engaged within the end portion  134  of the pin  150 , and engages a washer  146  which engages a compression member  148 . 
     A spindle drive motor  154  is mounted at one end of the frame  104  of the multi-spindle CNC lathe  50 . The spindle drive motor is preferably a variable speed alternating current electric motor. The motor  154  is supported by a motor mounting adaptor  156  which is in turn supported by a bearing housing  158 . The bearing housing  158  is secured to the wall  110  of the casting  106  of the frame  104  by a plurality of threaded fasteners  160 . 
     The motor  154  has an output shaft  162  which extends to a flexible coupling  164 . The flexible coupling  164  in turn-drives a spindle drive shaft  166 . The drive shaft  166  is rotatably supported by a bearing  168  which is retained in the bearing housing  158  by an end plate  170  that is in turn secured by threaded fasteners  172 . A spacer  174  and a lock nut  176  complete the drive shaft/bearing assembly. 
     Referring to FIGS. 4 and 5, the drive shaft  166  extends through a piston  180  which is secured to a tubular ram  182  by a plurality of threaded fasteners  183 . The piston  180  is mounted in a cylinder  184  which is located the retaining ring  208  also function to secure the tubular ram  182  to a spindle carrier assembly  218 . 
     The working -components of the multi-spindle CNC lathe  50  is illustrated in FIGS. 6 through 19, inclusive. As is clearly shown, for example, in FIGS. 7,  8 , and  9 , the particular multi-spindle CNC lathe  50  illustrated in the Drawings and described herein comprises an eight spindle device. However, as will be appreciated by those skilled in the art, the present invention is readily adapted for use in conjunction with multi-spindle CNC lathes having any desired number of spindles as may be dictated by the requirements of a particular application of the invention. 
     Internal slide assemblies  220  comprising the multi-spindle CNC lathe  50  are illustrated in FIGS. 7,  8 ,  9 ,  10 , and  11 , inclusive. Referring particularly to FIGS. 7 and 11, each internal slide assembly  220  includes a motor  224  which is secured to a motor mounting plate  226  by a plurality of threaded fasteners  228 . The motor mounting plate  226  is in turn secured to a mounting plate  230  by a plurality of threaded fasteners  232 . The mounting plate  230  is in turn secured to the wall  110  of the casting  106  comprising the frame  104  by a plurality of threaded fasteners  234 . 
     The motor  224  has an output shaft  236  which is secured to a drive pulley  238 . A drive belt  240  extends around the drive pulley  238  and a driven pulley  242 . The driven pulley  242  is mounted on a spacer  244  which is in turn secured to an adapter  246 . Thus, upon operation of the motor  224 , the adapter  246  is rotated under the action of the motor  224 , the output shaft  236 , the drive pulley  238 , the belt  240 , the driven pulley  242 , and the spacer  244 . 
     The adapter  246  is rotatably supported on the wall  110  by bearings  248 . The bearings  248  are supported in a bearing housing  250  by a plurality of threaded fasteners  252  which extend through the mounting plate  230 . A ball nut  254  is mounted on the adapter  246  and is secured thereto by a plurality of threaded fasteners  256 . 
     A ball screw  258  extends through and is operatively engaged with the ball nut  254 . The ball screw  258  is secured against rotation relative to the ball nut  254 . Thus, upon actuation of the motor  224  to rotate the adapter  246  and the ball nut  254 , the ball screw  258  is selectively extended or retracted. 
     A target adapter  260  extends from one end of the ball screw  258  and supports a target  262 . A sensor bracket  264  is secured to the mounting plate  226  by a plurality of threaded fasteners  266 . Proximity sensors  268 ,  270 , and  272  are mounted on the bracket  264 . Upon the alignment of the target  262  therewith, the proximity sensors  268 ,  270 , and  272  are actuated to generate a signal indicative of the positioning of the ball screw  258  relative to the frame  104  of the lathe  50 . Proximity sensor  270  is indicative of the normal positioning of the ball screw  258 , proximity sensor  272  is indicative of the fully retracted positioning of the ball screw  258 , and proximity sensor  268  is indicative of the fully extended position of the ball screw  258 . 
     The motor  224  operates under control of the CNC system  56  to position the ball screw  258 . The outputs of the proximity sensors  268 ,  270 , and  272  are directed to the CNC system  56 , which in turn operates the motor  224  to properly position the ball screw  258  in accordance with the program being run. 
     The ball screw  258  extends through a ball screw boot  274 . The boot  274  is secured to the wall  112  of the casting  106  of the frame  104  by a plurality of threaded fasteners  276 . At the distal end of the boot  274  there is provided a rod wiper  278 . 
     The end of the ball screw  258  remote from the target adapter  260  is provided with a threaded portion  280 . A pusher bracket  282  is secured to the end of the ball screw  258  by a nylon insert lock nut  284  threadably engaged with the end  280  of the ball screw  258 . A flat washer  286  is located between the pusher bracket  282  and the ball screw  258 . 
     A slide body  292  is secured to the pusher bracket  282  for reciprocation under the action of the ball screw  258  and the ball nut  254  which is in turn actuated by the motor  224  under the control of the CNC system  56 . Drive keys  294  are mounted at one end of the slide body  292  and is secured thereto by a plurality of threaded fasteners  296 . The slide body  292  is provided with a conventional central bore  298  and is adapted to receive a conventional tool holder, which in turn receives a conventional tool such as a drill, reamer, etc. 
     Those skilled in the art will appreciate the fact that the slide body  292  and tool holder received therein comprise static devices which are adapted to provide end working functions on rotating stock. The internal tool slide assembly  220  is also adapted for use with active slide components adapted for performing end working functions such as tapping, profile work, etc. and also for performing the pick up function after the work piece has been severed. 
     FIG. 31 illustrates an active tool holder assembly  700  which may be used in lieu of the passive tool holder assembly of FIG. 11 in the internal slide assembly of the multi-spindle CNC lathe  50  of the present invention, if desired. The tool collet holder assembly  700  includes a tool holder receiver  702  which is rotatably supported on a sub-frame  704  by bearings  706 . A motor  708  has an output  710  which drives a drive pulley  712 . A belt  714  extends around the drive-pulley  712  and a driven pulley  716  which is operatively connected to the tool holder receiver  702 . In the use of the apparatus  700 , a conventional tool holder is positioned in the bore  720  of the tool holder receiver  702 . The tool holder in turn receives a conventional tool. By means of the motor  708 , the tool is adapted for rotation as it is advanced toward and away from the rotating stock. By this means the tool may be utilized to provide, for example tapping of the stock. 
     Referring to FIG. 9, each slide body  292  has a pair of guide blocks  304  secured thereto by threaded fasteners  306 . The guide blocks  304  are received in correspondingly shaped, hardened and precision ground, guideways formed in a support body  308  and defined by components  307  and  314 . Sliding movement of the guide blocks  304 , and therefore the slide bodies  292 , is facilitated by the positioning of layers of polytetrafluroethylene  310  between the guide blocks  304  and the corresponding guideways. 
     The construction of the support body  308  will be best understood by simultaneous reference to FIGS. 5 and 9. The component parts  307  of the support body  308  comprising the guideways are secured to the cylinder  184  by a plurality of threaded fasteners  312 . The component parts  314  are secured by a plurality of threaded fasteners  316 . A cover plate  318  is mounted at the end of the support body  308  remote from the piston  180  and is secured by a plurality of threaded fasteners  320 . 
     Coolant is discharged from flexible nozzle assemblies  322  to the working area. The nozzle assemblies  322  are selectively mounted in discharged apertures  324  provided in the cover plate  318 . The apertures  324  extend to a passageway  326 . Coolant is directed into the passageway  326  for discharge from the flexible nozzle assemblies  322  through an inlet port  328  formed in the cylinder  184 . 
     Referring now to FIGS. 12 through 19, inclusive, the multi-spindle CNC lathe  50  includes a plurality of external slide assemblies  330 . Each external slide assembly  330  is supported on the wall  114  of the casting  108  of the frame  104  by a support bracket  332  which is secured to the wall  114  by a plurality of threaded fasteners  334 . Each external slide assembly  330  is adapted to support and position a cutting tool  336  relative to rotating stock. The external slide assemblies  330  function to move cutting tools  336  both toward and away from the rotating stock and toward and away from the wall  114  of the frame  104 , i.e., parallel to the stock. 
     Referring to FIGS. 13 and 15, each external slide assembly  330  includes a housing  340  which is guided by a circular guide  342  and a rectangular guide  344 . The guide  342  is mounted on the housing  340  and is slidably supported by bushings  343  mounted on the bracket  332 . The guide  344  is mounted on the bracket  332  and is secured by threaded fasteners  335 . 
     Referring to FIGS. 15 and 19, a motor  346  is mounted on a motor mounting plate  350  and is secured thereto by a plurality of threaded fasteners. The motor mounting plate  350  is in turn supported on a mounting plate  352  by a plurality of threaded fasteners  354 . 
     The motor  346  has an output shaft  356  which is connected to a drive pulley  358 . The drive pulley  358  drives a belt  360  which in turn drives a driven pulley  362 . The driven pulley  362  is secured on a adapter  364  by a spacer  366 . The adapter  364  is rotatably supported on the wall  116  by a bearing  368  which is mounted in a bearing housing  370 . The bearing housing  370  is secured in the plate  352  by a plurality of threaded fasteners  372 . 
     A ball nut  374  is secured to the adapter  364  by a plurality of threaded fasteners  376 . Thus, upon actuation of the motor  346  operating through the output shaft  356 , the drive pulley  358 , the drive belt  360 , and driven pulley  362 , the adapter  364 , and the spacer  366 , the ball nut  374  is actuated to rotate relative to the wall  116 . A ball screw  378  extends through and is operatively connected to the ball nut  374 . 
     A target adapter  380  is secured to one end of the ball screw  378  and has a target  382  mounted on the distal end thereof. A plurality of proximity sensors  384 ,  386 , and  388 , are mounted on a support plate  390  which is secured to the motor mounting plate  350  by a plurality of threaded fasteners  392 . When the target  382  is aligned with one of the proximity sensors  384 ,  386 , or  388 , a signal is generated indicative of the positioning of the housing  340  of the external slide assembly relative to the wall  114  of the frame  104 . 
     The end of the ball screw  378  remote from the target adapter  380  comprises a threaded end portion  394 . The ball screw  378  is secured to the housing  340  of the external slide assembly  330  by a nylon insert lock nut  396 . Therefore, upon operation of the motor  346 , the ball nut  374  functions to actuate the ball screw  378  to locate the housing  340  relative to the wall  114 . Referring to FIG. 16, the housing  340 . is supported for sliding movement toward and away from the wall  114  by guide members  342  and  344 . 
     The motor  346  operates under control of the CNC system  56  to position the ball screw  378 . The outputs of the proximity sensors  384 ,  386 , and  388  are directed to the CNC system  54  which in turn operates the motor  346  to position the ball screw  378  in accordance with the program being run. 
     As is best shown in FIGS. 16 and 17, a motor  400  is mounted at the end of the housing  340  remote from the cutting tool  336 . The motor  400  has an output shaft  402  which is connected to a flexible coupling  404  which is in turn connected to one end of a ball screw  406 . The ball screw  406  is rotatably supported by bearings  408  and  410  mounted in the housing  340 . 
     A ball nut  412  is mounted on and operatively connected to the ball screw  406 . The ball nut  412  is secured to a tool slide  414  which is slidably supported in the housing  340  by a plurality of threaded fasteners  416 . Thus, upon actuation of the motor  400  to rotate the ball screw  406 , the ball nut  412  functions to move the slide  414  and therefore the cutting tool  336  inwardly and outwardly relative to the housing  340 . 
     The motor  400  operates under control of the CNC system  56 . The motor  400  and the slide  414  have associated therewith a target and a plurality of proximity sensors like the target  382  and the sensors  384 ,  386 , and  388  associated with the ball screw  378 . The CNC system  56  receives signals from the sensors to allow control over the positioning of the cutting tool  336 . 
     Referring particularly to FIG. 18, there is shown a quick disconnect coupling for the cutting tool  336 . The cutting tool  336  is supported on a threaded fastener  416  positioned within the slide  414 . The cutting forces resulting from engagement of the cutting tool  336  with rotating stock are taken by a reaction block  418  which is secured to the slide  414  by a threaded fastener  419 . The threaded fastener  416  and therefore the cutting tool  336  are normally secured in the position shown in FIG. 18 by a retaining bar  420  having a ramp portion  422 . A pin  424  is positioned between the ramp portion  422  and the threaded fastener  416  and functions to retain the threaded fastener  416  and therefore the cutting tool  336  in place. A spring  426  normally retains the bar  420  in place. 
     A stop  428  is mounted in the housing  340  at the remote end of the slide  414 . When the slide  414  is fully retracted under the action of the ball nut  412  and the ball screw  406 , the bar  420  engages the stop  428 . This action compresses the spring  426  thereby relieving the pressure imposed on the pin  424  by the ramp portion  422 . This in turn allows the cutting tool  336  and the threaded fastener  416  to be disengaged from the slide  414 . 
     The multi-spindle CNC lathe  50  of the present invention further includes a plurality of spindles  430  of the type illustrated in FIGS. 20,  21 , and  22 . Each spindle  430  is rotatably supported in the spindle carrier  218  of FIG. 4 by bearings  432  and  434  and is retained therein by threaded fasteners  436  and  438 . 
     Each spindle  430  comprises a main body portion  440  having a planet gear  442  mounted thereon. Spacers  444  and  446  are interposed between the planet gear  442  and bearings  432  and  434  respectively. A collet receiving bore  448  extends through the main body  440  and a conventional self-opening collet  450  is disposed therein. A conventional collet aligning mechanism  452  may be positioned at the collet receiving end of the bore  448 . A driving key  454  assures proper alignment between the collet and the spindle. 
     The spindles  430  of the present invention comprise a unique collet opening, collet closing, and collet releasing mechanism. A glut  456  is slidably supported on a glut guide  458  and includes a dog  460  which engages a slot  462  formed in a collet actuator  464  mounted on the spindle  430 . The collet actuator  464  includes a retainer  466  which is secured by threaded fasteners  468 . A spring actuating member  470  is slidably supported within the main body  440  of the spindle  430 . A spring actuated retainer  472  is slidably supported on the spring actuator  470 . 
     The collet locked position′ is illustrated in FIG.  20 . At this point the glut  456  has been actuated to position the collet actuator  464  at its extreme rearward position relative to the collet  450 . A series of wedges  474  have been forced downwardly. This action moves a slider  476  rearwardly compressing compensating washers  478 , whereby a length of stock to be worked (not shown) is securely retained in the collet  450 . A dog  480  on the spring actuated retainer  472  is disengaged from the spring retainer  466  whereby a plunger  482  is fully extended under the action of a spring  484 . 
     In FIG. 21 the glut  456  is actuated to move the collet actuator  464  toward the planet gear  442 . The wedges  474  move upwardly under the action of the compensating washers  478  and centrifugal force. The retainer  466  approaches but does not quite engage the dog  480 , whereby the plunger  482  remains in position. At this point the self-opening collet  450  is released sufficiently to permit the repositioning of stock extending therethrough and/or to receive a new length of stock having the same dimensions as the previously engaged stock. 
     In FIG. 22 the glut  456  is actuated to move the collet actuator  464  to its extreme position. At this point the spring  484  is substantially compressed due to actuation of the plunger  482  by the spring actuating member  470  and the engagement of the dog  480  with the retainer  466 . This aligns a detent  486  with a retaining ball  488  to allow the ball  488  to move upwardly, thereby permitting the removal of the collet  450 . 
     Collet removal is indicated when a different size or type of stock is- to be retained by the collet  450  for rotation by the spindle  430 . Removal of the collet  450  may be effected either manually or automatically through the use of conventional collet removal and replacement apparatus. FIG. 23 illustrates a glut actuator  490  useful in the practice of the present invention to operate the dog  460  shown in FIG.  20 . The glut actuator  490  is mounted on the wall  116  of the casting  108  and is supported thereon by a mounting plate  492  which is secured to the wall  116  by a plurality of threaded fasteners  494 . A glut actuator  496  is secured to a movable housing  498  which is slidably supported on a guide rod  500 . The guide rod  500  is secured to the mounting plate  492  by a threaded fastener  502 . A piston  504  is fixedly mounted on the guide rod  500 , and is provided with seals  506 . An inner piston  508  is slidably supported on the guide rod  500  and is provided with seals  510 . An outer piston  512  is likewise slidably supported on the guide rod  500  and is provided with seals  514 . 
     The pistons  504 ,  508 , and  512  divide the housing  498  into four chambers  516 ,  518 ,  520 , and  522 . Hydraulic fluid inlet and outlet ports  526 ,  528 ,  530 , and  532  extend to the chambers  516 ,  518 ,  520  and  522 , respectively. Chamber  516  is secured against leakage by seals  534 , and chamber  522  is secured against leakage by seals  536 . 
     It will thus be understood by those skilled in the art that by selectively admitting pressurized hydraulic fluid to one of the chambers  516 ,  518 ,  520 , and  522 , and by simultaneously draining hydraulic fluid from the remaining chambers, the housing  498  and therefore the glut actuator  496  may be selectively located in any of four positions relative to the guide rod  500  and the chamber  516 . In this manner the glut actuator  490  of FIG. 23 functions to position the dog  460  of FIG. 20, thereby selectively engaging, disengaging, or releasing the collets  450  of the multi-spindle CNC lathe  50  of the present invention. The fourth position of the glut actuator  490  is used to allow indexing of the spindle carrier  218 . 
     Referring to FIG. 19, the multi-spindle CNC lathe  50  is shown as having eight gluts  456 , eight glut guides  458 , eight dogs  460 , and eight glut actuators  490 . This is to demonstrate the use of such components at any of the work stations and in as many No.s as needed for the particular application of the invention. Usually, no more than two gluts and glut actuators will be needed. 
     The spindle carrier  218  of FIG. 4 is further illustrated in the FIG.  24 . Multi-toothed coupling portion  540  having teeth  542  formed at equally spaced intervals therearound is secured between opposed body portions  544  and  546 . Coupling portion  540  is aligned by means of a dowel  548  and is secured in place by means of threaded fasteners  550 . The body portions  544  and  546  are in turn secured together by threaded fasteners  552 . 
     The spindle supporting bearings  434  illustrated in FIGS. 20,  21 , and  22  are received in a bearing receiving cavity  554  formed in body member  546 . The bearings  434  are secured in place by a plate  556  which is retained by the threaded fasteners  438 . The bearings  432  as illustrated in FIGS. 20,  21 , and  22  are received in a bearing receiving cavity  558  formed in the body member  544 . The bearings  432  are secured by a plate  560  which is secured in place by the threaded fasteners  436 . 
     Referring again to FIG. 24, the body portions  544  and  546  are preferably secured in place prior to the machining of the bearing receiving cavities  554  and  558 , thereby assuring precise alignment between the cavities. It will be appreciated that it is occasionally necessary to disassemble the body portions  544  and  546 . To this end there is provided an alignment ring  562  having extended profile portions  564 . The profile portions comprise segments of approximately 60 degrees which are in turn separated by vacant segments of approximately 60 degrees. By means of the profile portions  564  of the alignment ring  562 , the body portions  544  and  546  of the spindle carrier  218  may be separated and reassembled without loss of alignment between the bearing receiving cavities  554  and  558 . 
     A sun gear  570  is rotatably supported within the spindle carrier  218 . The sun gear  570  is rotatably supported by bearings  572  which are retained by a plate  574 . The plate  574  is in turn retained by threaded fasteners  576 . 
     The sun gear  570  has an internal spline  578  which engages in the internal spline  579  of the drive shaft  166  in FIG.  4 . In this manner the sun gear is rotated under the action of the spindle drive motor  154 . The sun gear  570  engages the planet gears  442  of the spindles  430 , whereby the motor  154  functions to rotate the spindles at a predetermined speed. 
     The spindle carrier  218  is secured to the tubular ram  182  by means of the threaded fasteners  210  which engage complementary threaded apertures  580  formed in the body portion  546 . Thus, upon actuation of the piston  180 , the positioning of the spindle carrier  218  is shifted longitudinally relative to the frame  104 . 
     Referring to FIG. 26, the casting  108  comprising the frame  104  has a multi-toothed coupling portion  582  secured therein by threaded fasteners  586 . The coupling portion  582  comprises a plurality of teeth  588  which are inverse to the teeth  542  of the coupling portion  540  of the spindle carrier  218 . Thus, when the piston  180  is actuated to move the ram  182  toward the casting  108 , the teeth  542  of the spindle carrier  218  engage the teeth  588  of the coupling portion  582  on the casting  108  to secure the spindle carrier  218  against rotation relative to the frame  104  of the multi-spindle CNC lathe  50 . Conversely, when the piston  180  is actuated to move the ram  182  away from the casting  108 , the teeth  542  on the spindle carrier  218  are disengaged from the teeth  588  of the coupling portion  582  on the casting  108 , whereupon the spindle carrier  218  is adapted for indexing relative to the frame  104  of the lathe  50 . 
     The frame  104  is provided with a bearing member  590 . The bearing member  590  has a precisely machined internal surface  592  which rotatably supports the spindle carrier  218  for indexing. To this end the lower segment of the bearing surface  216  is provided with a layer of polytetrafluroethylene  594  to facilitate rotation of the spindle carrier  218  relative to the bearing member  590   
     The multi-spindle CNC lathe  50  is provided with a plurality of stock carrier assemblies  600  which are best illustrated in FIGS. 27 and 28. Each stock carrier assembly  600  includes an inner stock carrying tube  602  which extends through one of the spindles  430  and is supported therein for rotation with the collet  450  received in and rotated by the spindle  430 . Each tube  602  is secured to a nut  604  which is threadedly engaged with the spindle  430 , thereby securing the tube  602  for rotation with the collet  450 . The use of a stock carrying tube adapted for rotation with the stock received therein comprises an important feature of the present invention and is a significant departure from the prior art. 
     Throughout a significant portion of its length the tube  602  extends through a stationary tube  606 . The tube  606  is provided with a conventional closure  608  located at the end thereof remote from the spindle  430 . The particular closure  608  illustrated in FIG. 27 is of the bayonet variety and is provided with a handle  610  which is moved inwardly to release the closure  608  for the insertion of stock into and through the tubes  606  and  602 . At all other times the closure  608  remains positioned as shown in FIG. 27 to seal the interior of the tube  606  against leakage of coolant therefrom. 
     The rotating tube  602  has a plurality of apertures  612  formed therein to permit the flow of coolant out the tube  602  into the tube  606 . The tube  606  extends to a seal  614  which prevents leakage of coolant from the end of the tube  606  remote from the closure  608 . A secondary seal  616  is mounted on the seal  614  and extends along the tube  602  further to prevent leakage of coolant. 
     Each tube  606  is further provided with fixtures  618  and  620  which function to admit coolant into the tube  606 . Whenever it is desired to advance the position of the stock located within and rotating with the tube  602 , the pressure of the coolant within the tube  606  is increased. It will be understood that one end of the stock is situated within the assembly comprising the tubes  602  and  606 , and is therefore subject to the application of an endwise force resulting from the increase in coolant pressure. However, the opposite end of the stock is situated within the collet and is therefore not subject to the increased pressure of the coolant within the tubes  602  and  606 . By this means there is provided an endwise force on the stock which pushes the stock through the collet  450  without requiring the use of independent stock advancing mechanisms. The presence of the coolant within the tubes  602  and  606  also provides significant vibration damping and noise reduction as compared with prior art stock advancing mechanisms. 
     The stock carriage mechanism of the multi-spindle CNC lathe  50  is illustrated in FIG.  29 . The stock carriage tubes  602  and  606  of the stock carriage assembly  600  are supported on a carriage assembly  622 . Rings  624  are provided at each end of a stock carriage housing  626 . Rollers  628  are provided on the carriage assembly  622  and engage the rings  624 . By this means the carriage assembly  622  and therefore the stock carriage assembly  600  is adapted for revolution about the central axis  632  of the multi-spindle CNC lathe  50 . 
     An indexing mechanism  640  for the multi-spindle CNC lathe  50  is illustrated in FIG. 30. A motor  642  drives an indexer  643  which has an output  644  that drives a drive pulley  646 . A belt  648  extends around the drive pulley  646  and functions to actuate a driven pulley  650  under the action of the motor  642  and the indexer  643 . The driven pulley  650  is connected to a rotator plate  652  which is connected to the carriage assembly  622  by a plurality of threaded fasteners  658 . Thus, upon actuation of the motor  642  and indexer  643 , the carriage assembly  622  and the stock carriage tubes mounted thereon are revolved around the axis  632 . 
     A spider  656  is mounted to the assembly  622  for rotation therewith under the action of the motor  642  and the indexer  643 . The spider  656  comprises a plurality of pins  660  each having opposed spherical ends  662 . The spherical ends  662  of the pins  660  are received in bores  664 , thereby accommodating a predetermined amount of misalignment between the assembly  622  and a connector  666  which is secured to the spindle carrier  218  by means of a 
     In the operation of the multi-spindle CNC lathe  50 , one or more of the closures  608  is disengaged to permit the insertion of stock into the tube  606  and the tube  602  of the stock carrier assembly. The glut actuator assembly  490  is then actuated to operate the dog  460  to open one or more of the collets  450 . Stock is initially positioned manually. Thereafter, pressure of the coolant within the tubes  602  and  606  of the stock carrier assembly is selectively increased, whereupon the stock is advanced through the corresponding collet  450  until it is properly positioned. 
     Indexing of the stock relative to the tools of the multi-spindle CNC lathe  50  begins with actuation of the piston  180  to move the ram  182  rightwardly (FIG. 5) thereby disengaging the teeth  542  of the coupling portion  540  of the stock carrier  218  (FIG. 24) from the teeth  588  of the coupling portion  582  which is secured to the frame  104  (FIG.  26 ). The indexing motor  642  (FIG. 30) is then actuated to index the carriage assembly  622  and therefore the tubes  602  and  606 , and also the stock carrier  218  having the spindles  430  and the collets  450  mounted thereon. This action causes the stock, the tube  602  and  606 , the spindles  430 , and the collets  450  to revolve about the axis  632  of the multi-spindle CNC lathe  50  until the stock is properly positioned relative to the frame. 
     The internal slide assemblies  220  of the multi-spindle CNC lathe  50  are mounted on the support body  308  which is secured to the wall  112  of the casting  106  of the frame  104 . Therefore, as the stock is indexed under the action of the motor  642 , the internal slide assemblies do not move, but instead remain stationary and in position to engage the next individual piece of stock which is aligned therewith. 
     Likewise, the external slide assemblies  330  are supported on support brackets  332  which are secured to the wall  114  of the casting  108  of the frame  104  by threaded fasteners  334 . Therefore, the external slide assemblies  330  do not move as the stock is indexed under the action of the motor  642 , but instead remain positioned for engagement with the next piece of stock which is aligned therewith. 
     An important feature of the present invention comprises the fact that the external slide assemblies  330  are adapted to move the tools  336  not only toward and away from, that is, perpendicular to the rotating stock, but also along the length of, that is parallel to the stock. The tools  336  do not comprise forming tools, but instead comprise general purpose metal working tools which may be utilized to form any desired shape in the external surfaces of the stock pieces. It is therefore not necessary to remove and replace the tools  336  when adapting the multispindle CNC lathe  50  of the present invention to the manufacture of a different product. 
     This in turn means that the multi-spindle CNC lathe  50  of the present invention is readily adapted to the Just In Time, or JIT, manufacturing philosophy in that the lathe  50  may be utilized to manufacture a small number of parts and to have the parts available at the precise moment that they are needed in subsequent manufacturing operations. The multi-spindle CNC lathe  50  of the present invention is also readily adapted to the Statistical Process Control, or SPC, manufacturing philosophy whereby wearing of the tools utilized in the internal slide assemblies  220  and the external slide assemblies  330  is constantly monitored and adjusted by actuating the slide assemblies  220  and  330  to assure manufacturing tolerances which are well within the acceptable range. 
     After all of the tools comprising the internal slide assemblies  220  and all of the tools comprising the external slide assembly  330  have completed their respective functions, the tools are disengaged from the rotating stock. At this point the piston  180  is actuated to disengage the teeth  542  of the stock carrier  218  from the teeth  588 , whereupon the motor  642  is actuated to index the stock into alignment with the next successive work station. As will be understood by those skilled in the art, one or more of the spindles comprising the multi-spindle CNC lathe  50  comprises a cutoff station, wherein the finished work is disengaged from the stock. Upon cutoff, the stock is selectively advanced through the respective collets under the action of increased pressure in the coolant in the associated tubes  602  and  606 . 
     All of the component parts of the multi-spindle CNC lathe operate under the control of the CNC system  56 . In this manner there is facilitated the use of general purpose cutting tools, rather than forming tools, which in turn facilitates the JIT manufacturing philosophy. Likewise, the CNC system facilitates the SPC manufacturing philosophy by constantly repositioning the cutting tools to accommodate wear. 
     Those skilled in the art will appreciate the fact that in the operation of the multi-spindle CNC lathe of the present invention, the two servo mechanisms comprising each external slide assembly operate simultaneously in order to form the complex configurations which are typically fabricated on single spindle and multi-spindle legs. Preferably, each internal slide assembly  220  operates simultaneously with its corresponding external slide assembly  330  in order that the multi-spindle CNC lathe  50  can function at maximum efficiency. It will be understood, rearrangements, modifications, and substitutions of parts and elements without departing from the spirit of the invention.