Patent Publication Number: US-2010130106-A1

Title: Machine tool with cooling nozzle and method for applying cooling fluid

Description:
RELATED APPLICATION 
     This international application claims the benefit of prior U.S. provisional patent application Ser. No. 60/892,502 filed Mar. 1, 2007, and prior U.S. regular patent application Ser. No. 12/040,602 filed Feb. 29, 2008. The entire contents of the prior patent applications are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The invention is in the field of computer numerically controlled machines. Various embodiments of the invention are in the field of coolant delivery within a computer numerically controlled machine 
     BACKGROUND 
     Coolant is supplied in computer numerically controlled machines for various purposes. Typically, the coolant, which is an oil, an aqueous emulsion, or other liquid, is introduced under pressure via a nozzle. Grinding operations in general require adequate coolant at the point of contact between workpiece and the grinding wheel. In such operations, coolant typically is directed under pressure at the grinding wheel or workpiece or at the point of contact between the workpiece and wheel. The workpiece may itself be a cutting tool that is reground in the grinding operation or may be a functional part. In other operations, such as milling, coolant likewise may be applied to the workpiece or the tool, or applied at the tool-workpiece interface (point of contact). Also, the cooling fluid may be applied during or after a machine operation as a cleaning spray to wash away swarf. 
     The prior art has provided machines that include coolant nozzles, which, in many cases, are proximate the chuck of the machine tool. With typical coolant nozzle placement, it can be difficult to control and properly direct the coolant. This can cause difficulties. For instance, in a grinding operation it is typical for the coolant to be applied to the grinding wheel, which spins and which tends to throw off the coolant via centrifugal forces. It is sometimes desirable to maintain a constant time to interface, or time between the initial contact of the coolant with the grinding wheel and the time the coolant on the wheel reaches the interface between the wheel and workpiece. The grinding wheel often erodes during a grinding operation, and the ground dimension of the workpiece can decrease, thus requiring adjustment to the coolant nozzle if a constant time-to-interface is desired. In other circumstances, it may be desirable to maintain a constant contact angle, or rotational angle between the point of contact of the coolant on the workpiece or tool and the point of contact at the workpiece interface. Again, it can be difficult to maintain a constant contact angle, particularly if the size of the tool or of the workpiece changes, or as the position of the workpiece is varied. 
     U.S. Pat. No. 6,772,042 B1 (assigned to Dimensional Control, Inc.) and U.S. Pat. No. 6,666,748 B2 (assigned to Makino Milling Machines Co., Ltd.) purport to provide servo-controlled programmable coolant nozzles that are used to direct coolant to grinding wheel. The heretofore described servo-controlled coolant nozzle and programmable coolant nozzle of the prior art require special machine modifications. Generally, it is desired to provide in some embodiments a coolant nozzle arrangement and in some embodiments a method that differs from the foregoing. 
     SUMMARY OF THE INVENTION 
     The invention provides in one embodiment a machine having a turret and a coolant nozzle that is mounted on the turret in a rotary fashion on a facet of the turret, generally under the control of a computer control system. The turret typically may be rotated to expose different facets, and the coolant nozzle may be installed on one of the facets and rotated out of functional position when not in use. The coolant nozzle may comprise a nozzle and a device for rotating the nozzle. The turret typically is moveable in linear X and Z directions, and possibly in a Y direction, thus permitting the cooling nozzle to be translated and rotated to various positions. The coolant nozzle is fluidically coupled to a source of cooling fluid by which coolant may be introduced under pressure through the nozzle. 
     The coolant nozzle may be moved relative to the workpiece or tool as the workpiece and tool move with respect to one another. In some embodiments, a constant coolant contact angle with respect to the wheel and workpiece may be maintained. In other embodiments, a constant time to interface for the coolant may be maintained. The constant time to interface embodiments are deemed particularly (but nor exclusively) suitable for so-called “viper” (very impressive performance extreme removal) grinding. As discussed in more detail in U.S. Pat. No. 6,123,606, viper grinding is characterized by employing a grinding wheel, typically a porous grinding wheel, that is brought to bear on a workpiece to cause a high rate of removal of workpiece material. Coolant is sprayed onto the grinding wheel, typically at high pressures (1000 psi is conventional) relative to coolant pressures employed in other machine operations. Coolant is typically absorbed by the porous grinding wheel to enable cooling of the wheel and workpiece and the coolant generally serves to clean the wheel. Viper grinding is deemed useful for materials that are difficult to machine, such as many titanium- and nickel-based materials. U.S. Pat. No. 6,123,606 is hereby incorporated by reference in its entirety for its disclosure of a grinding operation. 
     In alternative embodiments, the grinding wheel is mounted on a tool spindle of the machine, with a coolant nozzle mounted on a grinding wheel guard. The spindle may be translated and rotated about an axis that is perpendicular to the axis of rotation of the spindle and grinding wheel. 
     The invention also provides a method whereby the coolant nozzle may be moved relative to the workpiece or tool as the workpiece and tool move with respect to one another. In some embodiments the nozzle moves with respect to the axis of rotation of the grinding wheel. In other embodiments, the nozzle is stationary with respect to the axis of rotation of the grinding wheel. For instance, the nozzle may be mounted on a guard of the grinding wheel. 
     In various embodiments, the invention likewise encompasses an apparatus that includes one of the structures heretofore described and a computer control system with a computer-readable medium having computer-readable code disposed thereon that, when executed, is configured to cause movement of the nozzle. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front elevation view of a computer numerically controlled machine in accordance with one embodiment of the present invention, shown with safety doors closed; 
         FIG. 2  is a front elevation view of a computer numerically controlled machine illustrated in  FIG. 1 , shown with the safety doors open; 
         FIG. 3  is a perspective view of certain interior components of the computer numerically controlled machine illustrated in  FIGS. 1 and 2 , depicting a machining spindle, a first chuck, a second chuck, and a turret; 
         FIG. 4  a perspective view, enlarged with respect to  FIG. 3  illustrating the machining spindle and the horizontally and vertically disposed rails via which the spindle may be translated; 
         FIG. 5  is a side view of the first chuck, machining spindle, and turret of the machining center illustrated in  FIG. 1 ; 
         FIG. 6  is a view similar to  FIG. 5  but in which a machining spindle has been translated in the Y-axis; 
         FIG. 7  is a front view of the spindle, first chuck, and second chuck of the computer numerically controlled machine illustrated in  FIG. 1 , including a line depicting the permitted path of rotational movement of this spindle; 
         FIG. 8  is a perspective view of the second chuck illustrated in  FIG. 3 , enlarged with respect to  FIG. 3 ; 
         FIG. 9  is a perspective view of the first chuck and turret illustrated in  FIG. 2 , depicting movement of the turret and turret stock in the Z-axis relative to the position of the turret in  FIG. 2 ; 
         FIG. 10  is a front elevation of a computer numerically controlled machine illustrating a turret-mounted coolant nozzle in accordance with one embodiment of the invention. 
         FIG. 11  is a side elevation of the computer numerically controlled machine showing  FIG. 10 . 
         FIG. 12  is a side elevation of a computer numerically controlled machine, showing an alternative embodiment of a coolant nozzle. 
         FIG. 13  is a front elevation of a computer numerically controlled machine having another alternative coolant nozzle. 
         FIG. 14  is a side elevation of the machine shown  FIG. 13 . 
         FIG. 15  is a representation of a side view of a machine showing motion of a grinding wheel and of the coolant nozzle tool as the wheel decreases with diameter during the grinding operation so as to maintain constant time to interface. 
         FIG. 16  shows a curved coolant nozzle, without a rotary tool holder, mounted on the turret for grinding. 
         FIG. 17  is a front view, and  FIG. 18  is a side view, of a coolant nozzle, without a rotary tool holder, mounted on the turret for grinding, with the axis of rotation of the perpendicular to the control axis of to the work piece. 
         FIG. 19  is a perspective view of an embodiment of a coolant nozzle, illustrating a coolant nozzle in a rotary tool holder, the nozzle being rotatable in an A-axis. 
         FIG. 20  is a perspective view of an embodiment of a coolant nozzle, illustrating a coolant nozzle in a rotary tool holder, the nozzle being rotatable in a C-axis. 
         FIG. 21  is a perspective view of an embodiment of a coolant nozzle, illustrating the coolant nozzle in a rotary tool holder, the nozzle being rotatable in a B-axis. 
         FIG. 22  is a perspective view of a computer numerically controlled machine employing the coolant nozzle illustrated in  FIG. 19  in a slot grinding operation. 
         FIG. 23  is a perspective view of a computer numerically controlled machine illustrating the coolant nozzle shown in  FIG. 20  in an outside diameter rough grinding operation. 
         FIG. 24  is a perspective view of the end of a nozzle in accordance with one embodiment of the invention. 
         FIG. 25  is a representation of a machining operation where the nozzle is mounted on a guard of a grinding wheel and is thus stationary relative to the axis of rotation of the grinding wheel, but wherein a constant time to interface is achieved by moving the nozzle and workpiece relative to one another. 
     
    
    
     DETAILED DESCRIPTION 
     Any suitable apparatus may be employed in conjunction with the methods of invention. In some embodiments, the methods are performed using a computer numerically controlled machine, illustrated generally in  FIGS. 1-9 . A computer numerically controlled machine is itself provided in other embodiments of the invention. The machine  100  illustrated in  FIGS. 1-9  is an NT-series machine, versions of which are available from Mori Seiki USA, Inc., the assignee of the present application. Other suitable computer numerically controlled machines include the NL-series machines with turret (not shown), also available from Mori Seiki USA, Inc. Other machines may be used in conjunction with the invention, including the NZ, NH, NV, and NMV machines, also available from Mori Seiki USA, Inc. 
     In general, with reference to the NT-series machine illustrated in  FIGS. 1-3 , one suitable computer numerically controlled machine  100  has at least a first retainer and a second retainer, each of which may be one of a spindle retainer associated with spindle  144 , a turret retainer associated with a turret  108 , or a chuck  110 ,  112 . In the embodiment illustrated in the Figures, the computer numerically controlled machine  100  is provided with a spindle  144 , a turret  108 , a first chuck  110 , and a second chuck  112 . The computer numerically controlled machine  100  also has a computer control system operatively coupled to the first retainer and to the second retainer for controlling the retainers, as described in more detail below. It is understood that in some embodiments, the computer numerically controlled machine  100  may not contain all of the above components, and in other embodiments, the computer numerically controlled machine  100  may contain additional components beyond those designated herein. 
     As shown in  FIGS. 1 and 2 , the computer numerically controlled machine  100  has a machine chamber  116  in which various operations generally take place upon a workpiece (not shown). Each of the spindle  144 , the turret  108 , the first chuck  110 , and the second chuck  112  may be completely or partially located within the machine chamber  116 . In the embodiment shown, two moveable safety doors  118  separate the user from the chamber  116  to prevent injury to the user or interference in the operation of the computer numerically controlled machine  100 . The safety doors  118  can be opened to permit access to the chamber  116  as illustrated in  FIG. 2 . The computer numerically controlled machine  100  is described herein with respect to three orthogonally oriented linear axes (X, Y, and Z), depicted in  FIG. 4  and described in greater detail below. Rotational axes about the X, Y and Z axes are connoted “A,” “B,” and “C” rotational axes respectively. 
     The computer numerically controlled machine  100  is provided with a computer control system for controlling the various instrumentalities within the computer numerically controlled machine. In the illustrated embodiment, the machine is provided with two interlinked computer systems, a first computer system comprising a user interface system (shown generally at  114  in  FIG. 1 ) and a second computer system (not illustrated) operatively connected to the first computer system. The second computer system directly controls the operations of the spindle, the turret, and the other instrumentalities of the machine, while the user interface system  114  allows an operator to control the second computer system. Collectively, the machine control system and the user interface system, together with the various mechanisms for control of operations in the machine, may be considered a single computer control system. In some embodiments, the user operates the user interface system to impart programming to the machine; in other embodiments, programs can be loaded or transferred into the machine via external sources. It is contemplated, for instance, that programs may be loaded via a PCMCIA interface, an RS-232 interface, a universal serial bus interface (USB), or a network interface, in particular a TCP/IP network interface. In other embodiments, a machine may be controlled via conventional PLC (programmable logic controller) mechanisms (not illustrated). 
     As further illustrated in  FIGS. 1 and 2 , the computer numerically computer controlled machine  100  may have a tool magazine  142  and a tool changing device  143 . These cooperate with the spindle  144  to permit the spindle to operate with plural cutting tools (shown in  FIG. 1  as tools  102 ′). Generally, a variety of cutting tools may be provided; in some embodiments, plural tools of the same type may be provided. 
     The spindle  144  is mounted on a carriage assembly  120  that allows for translational movement along the X- and Z-axes, and on a ram  132  that allows the spindle  144  to be moved in the Y-axis. The ram  132  is equipped with a motor to allow rotation of the spindle in the B-axis, as set forth in more detail hereinbelow. As illustrated, the carriage assembly has a first carriage  124  that rides along two threaded vertical rails (one rail shown at  126 ) to cause the first carriage  124  and spindle  144  to translate in the X-axis. The carriage assembly also includes a second carriage  128  that rides along two horizontally disposed threaded rails (one shown in  FIG. 3  at  130 ) to allow movement of the second carriage  128  and spindle  144  in the Z-axis. Each carriage  124 ,  128  engages the rails via plural ball screw devices whereby rotation of the rails  126 ,  130  causes translation of the carriage in the X- or Z-direction respectively. The rails are equipped with motors  170  and  172  for the horizontally disposed and vertically disposed rails respectively. 
     The spindle  144  holds the cutting tool  102  by way of a spindle connection and a tool holder  106 . The spindle connection  145  (shown in  FIG. 2 ) is connected to the spindle  144  and is contained within the spindle  144 . The tool holder  106  is connected to the spindle connection  145  and holds the cutting tool  102 . Various types of spindle connections are known in the art and can be used with the computer numerically controlled machine  100 . Typically, the spindle connection  145  is contained within the spindle  144  for the life of the spindle. An access plate  122  for the spindle  144  is shown in  FIGS. 5 and 6 . 
     The first chuck  110  is provided with jaws  136  and is disposed in a stock  150  that is stationary with respect to the base  111  of the computer numerically controlled machine  100 . The second chuck  112  is also provided with jaws  137 , but the second chuck  112  is movable with respect to the base  111  of the computer numerically controlled machine  100 . More specifically, the machine  100  is provided with threaded rails  138  and motors  139  for causing translation in the Z-direction of the second stock  152  via a ball screw mechanism as heretofore described. To assist in swarf removal, the stock  152  is provided with a sloped distal surface  174  and a side frame  176  with Z-sloped surfaces  177 ,  178 . Hydraulic controls and associated indicators for the chucks  110 ,  112  may be provided, such as the pressure gauges  182  and control knobs  184  shown in  FIGS. 1 and 2 . Each stock is provided with a motor ( 161 ,  162  respectively) for causing rotation of the chuck. 
     The turret  108 , which is best depicted in  FIGS. 5 ,  6  and  9 , is mounted in a turret stock  146  ( FIG. 5 ) that also engages rails  138  and that may be translated in a Z-direction, again via ball-screw devices. The turret  108  is provided with various turret connectors or facets  134 , as illustrated in  FIG. 9 . Each turret connector  134  can be connected to a tool holder  135  or other connection for connecting to a cutting tool. Since the turret  108  can have a variety of turret connectors  134  and tool holders  135 , a variety of different cutting tools can be held and operated by the turret  108 . The turret  108  may be rotated in a C axis to present different ones of the tool holders (and hence, in many embodiments, different tools) to a workpiece. 
     It is thus seen that a wide range of versatile operations may be performed. With reference to tool  102  held in tool holder  106 , such tool  102  may be brought to bear against a workpiece (not shown) held by one or both of chucks  110 ,  112 . When it is necessary or desirable to change the tool  102 , a replacement tool  102  may be retrieved from the tool magazine  142  by means of the tool changing device  143 . With reference to  FIGS. 4 and 5 , the spindle  144  may be translated in the X and Z directions (shown in  FIG. 4 ) and Y direction (shown in  FIGS. 5 and 6 ). Rotation in the B-axis is depicted in  FIG. 7 , the illustrated embodiment permitting rotation within a range of 120° to either side of the vertical. Movement in the Y direction and rotation in the B axis are powered by motors (not shown) that are located behind the carriage  124 . Generally, as seen in  FIGS. 2 and 7 , the machine is provided with a plurality of vertically disposed leaves  180  and horizontal disposed leaves  181  to define a wall of the chamber  116  and to prevent swarf from exiting this chamber. 
     The components of the machine  100  are not limited to the heretofore described components. For instance, in some instances an additional turret may be provided. In other instances, additional chucks and/or spindles may be provided. Generally, the machine is provided with one or more mechanisms for introducing a cooling liquid into the chamber  116 . 
     In the illustrated embodiment, the computer numerically controlled machine  100  is provided with numerous retainers. Chuck  110  in combination with jaws  136  forms a retainer, as does chuck  112  in combination with jaws  137 . In many instances these retainers will also be used to hold a workpiece. For instance, the chucks and associated stocks will function in a lathe-like manner as the headstock and optional tailstock for a rotating workpiece. Spindle  144  and spindle connection  145  form another retainer. Similarly, the turret  108 , when equipped with plural turret connectors  134 , provides a plurality of retainers (shown in  FIG. 9 ). 
     The computer numerically controlled machine  100  may use any of a number of different types of cutting tools known in the art or otherwise found to be suitable. For instance, the cutting tool  102  may be a milling tool, a drilling tool, a grinding tool, a blade tool, a broaching tool, a turning tool, or any other type of cutting tool deemed appropriate in connection with a computer numerically controlled machine  100 . As discussed above, the computer numerically controlled machine  100  may be provided with more than one type of cutting tool, and via the mechanisms of the tool changing device  143  and magazine  142 , the spindle  144  may be caused to exchange one tool for another. Similarly, the turret  108  may be provided with one or more cutting tools  102 , and the operator may switch between cutting tools  102  by causing rotation of the turret  108  to bring a new turret connector  134  into the appropriate position. 
     Other features of a computer numerically controlled machine include, for instance, an air blower for clearance and removal of chips, various cameras, tool calibrating devices, probes, probe receivers, and lighting features. The computer numerically controlled machine illustrated in  FIGS. 1-9  is not the only machine of the invention, but to the contrary, other embodiments are envisioned. 
     With reference to  FIG. 10 , the turret  108  includes a programmable coolant nozzle  200 , which is more clearly seen in  FIG. 11 . A spindle  144  includes a tool, such as a grinding wheel  202  that, in the illustrated embodiment, is performing a grinding operation on a workpiece  204  that is mounted in a side chuck  110 . The spindle  144  may be rotated about an axis R 1  that is perpendicular to the axis of rotation R 2  of the wheel  202  when the turret  108  is in a fixed position relative to a base of the machine. The coolant nozzle  200  in the illustrated embodiment is mounted in a rotary holder  206  that is operatively coupled to a motor, and which may be similar to tool holders  135 . The rotary holder  206  is capable of rotating the nozzle  200  about an axis of rotation R 4  which, in the embodiment of  FIGS. 10-11 , is perpendicular to the axes of rotation R 1 , R 2 , R 3  of the spindle  144 , the wheel  202 , and the workpiece  204 , respectively. The motor is coupled to the computer control system of the machine. The motor may be internal to the turret  108  or may be external to the turret  108 . The nozzle  200  is fluidically coupled to a source  208  of cooling fluid, whereby, under the control of the computer control system, fluid may selectively be delivered under pressure to the nozzle  200 . The source  208  may include pumping and filtering equipment, as well as other known components. The rotary holder  206  may be a conventionally driven rotary driven holder that includes a keyed arbor that engages a corresponding structure (not shown) within the turret  108 . In some embodiments a nozzle may be disposed on a conventional nonrotary holder. 
     As illustrated in  FIGS. 12-14 , the coolant nozzle may take different forms. For instance, as shown in  FIG. 12 , the coolant nozzle tool may be an angled nozzle tool  200 A. In this embodiment, the nozzle  200 A is disposed at an oblique angle relative to the axis of rotation R 3  of the turret  108 . As shown in  FIGS. 13-14 , the tool alternatively may be a right-angle nozzle tool  200 B, and may be mounted on the side of the turret  108 . In each of these embodiments, the nozzle is mounted on a rotary tool holder  206  and is thereby rotatable independently of the rotation of the turret  108 . In the embodiment of  FIGS. 13-14 , the rotary holders  206  are configured to rotate the nozzles  200 B,  200 C on an axis of rotation R 4  that is parallel to the axes of rotation R 2 , R 3  of the wheel  202  and workpiece  204 , respectively. In a further embodiment, as shown in  FIG. 16 , the nozzle  200 E may be curved. 
     The machine tool  100  preferably is a numerically controlled machine tool  100  in which the turret  108  may be translated in the X and Z directions as is conventional using conventional programming techniques. Preferably, the chuck  110  likewise may be translated along axes perpendicular to the axis of rotation R 4  of the workpiece  204 . It is thus seen that a great degree of flexibility in the positioning of the nozzle  200  relative to the grinding wheel  202  and workpiece  204  may be achieved. In some embodiments, the turret  108  may be movable in a Y-direction as well. 
     As shown in  FIG. 15 , during the grinding operation, the grinding wheel  202  typically will become reduced in diameter to a reduced diameter (wheel  202 ′ representing the wheel  202  after reduction in diameter). The speed of revolution of the grinding wheel  202  has been increased by 100% to maintain the surface velocity of the wheel. By moving the grinding wheel  202  relative to the workpiece, as shown via path P, and by moving the coolant nozzle  200 D from position P 1  to position P 2  (indicated by  200 D′), a constant coolant time to interface with respect to the grinding wheel  202  thus may be maintained. The constant time to interface may be maintained within the limits of the machine. The coolant angle changes from 90 degrees (shown with the nozzle in position P 1 ) to 180 degrees (in position P 2 ) but the diameter of the wheel has been reduced by 50%, and thus the time to interface remains the same. 
     Various modifications of the above may be made. For instance, the wheel  202  and workpiece  204  are shown as having the form of right circular cylinders, but other forms are possible. 
     The position of the coolant nozzle will be controlled by the X- and Z-direction motion of the turret  108 , and then the nozzle is rotatable to control the rotary position of the nozzle. The nozzle may be mounted in a conventional tool holder that permits 360° rotation, such as tool holders  135  of the turret  108  depicted in  FIG. 9 . The coolant nozzle can direct the coolant either at a contact point between the work piece  204  and the grinding wheel  202  or directly on the grinding wheel  202  for continuous viper grinding. 
       FIGS. 17 and 18  show other possible orientations in which a coolant nozzles  200 F,  200 G are mounted on the turret  108  so as to direct coolant for continuous viper grinding. 
     The coolant nozzle may be rotatable about any suitable axis, such as the A-, B-, and C-axes illustrated in  FIG. 4 . As shown, for instance, in  FIGS. 19-21  respectively, the coolant nozzle  200 H,  200 I,  200 J may be rotatable about the A-, C-, or B-axes. Rotation is enabled when the coolant nozzle  200 H,  200 I,  200 J is disposed in the operating position of the turret  108 , which, in the illustrated embodiment, is at the “top” of the turret  108 . Generally, this operating position is the sole position at which coolant flows through a tool holder  206  disposed on the turret  108  and in which the turret motor is positioned to rotate the coolant nozzle. It is contemplated, however, that other operating positions on the turret are possible and that other axes of rotation of the coolant nozzle may be employed. Likewise, the coolant nozzle is shown as extending at a 90° angle relative to the axes of rotation R 1 , R 2 , and R 3  of the spindle  144 , the grinding wheel  202 , and the turret  108 , respectively, but in other embodiments the coolant nozzle may extend at an oblique angle with respect to the axes of rotation. 
     It is thus seen that various configurations are possible. For instance, with respect to  FIG. 22 , a slot grinding operation may be employed with the coolant nozzle  200 H illustrated in  FIG. 19  delivering cooling fluid to impinge upon the grinding wheel  202  as illustrated. Alternatively, as shown in  FIG. 23  with regard to the outside diameter rough grinding operation, the coolant nozzle  200 I illustrated in  FIG. 20  may be employed. More generally, other configurations of the coolant nozzle relative to the grinding wheel  202  and workpiece  204  are possible. 
     The nozzle may be rotatable about an axis of rotation R 4  that may vary depending on the configuration of the rotary holder  206 . For example, in the embodiments shown in  FIGS. 10-12 , the nozzles  200 ,  200 A have an axis of rotation R 4  that is in the A-axis of the machine. In the embodiment shown in  FIGS. 13-14 , the nozzles  200 B,  200 C each have an axis of rotation that is in the C-axis of the machine. In other embodiments, the nozzle may be rotatable in the B-axis of the machine, such as the nozzle  200 J shown in  FIG. 21 , or on an axis oblique to the A-, B-, and C-axes. 
     The coolant is supplied under pressure to the nozzle, and, in connection with viper grinding, the coolant is typically supplied under a pressure of 500-1500 psi. As shown in  FIG. 24 , the tip  210  of the nozzle  200 K may take the form of a narrow slit. It is believed in some embodiments that the slit configuration will enable laminar coolant flow, which may be desired in some cases. Such laminar flow can enable spraying coolant from a greater distance, thus avoiding the need to position the nozzle in close proximity to the grinding wheel  202  and/or the workpiece  204 . Other nozzle configurations are possible. For instance, the tip may take the form of a surface with plural small holes (not shown). Laminar flow may be possible in other nozzle configurations. 
     As shown in  FIG. 25 , the nozzle  200 L may be mounted on a guard  212  of the grinding wheel  202 . In this embodiment, the grinding wheel  202  may be disposed on the spindle  144  of the machine. The guard  212  and hence the nozzle  200 L are stationary with regard to the axis of rotation of the nozzle, i.e., the nozzle, guard, and wheel move together in the machine (although the wheel rotates and hence moves with respect to the nozzle and guard). To maintain a constant coolant contact angle, the workpiece  204  and grinding wheel  202  are moved relative to one another while the guard  212  and nozzle  200 L remain stationary with respect to the axis of rotation R 2  of the grinding wheel  202 . 
     The machine may (and typically will) include other nozzles for dispensing coolant. Some nozzles may operate under lower pressure (around 100 psi) than the pressures desired for viper grinding. In such cases, the machine may be equipped with plural pumps, one for lower pressure operations and one for higher pressure operations. One suitable high-pressure, high-volume pump is sold under the trademark CHIPBLASTER by Chipblaster of Meadville Pa. In some cases, plural nozzles are provided, one to spray coolant onto the grinding wheel (or workpiece) before the point of contact and one to spray coolant to serve a cleaning function after the point of contact. For viper grinding, a second cleaning coolant nozzle may be used but typically is not required. 
     The invention has been exemplified with respect to a grinding wheel, but other tools alternatively may be employed. Grinding wheels other than disc-shaped wheels are contemplated. Similarly, the invention has been exemplified with respect to the machine shown in the figures, but other machine configurations are possible. In some embodiments, a machine may be equipped with plural turrets, and in some embodiments one or more turrets may have a Y-axis component of motion. 
     The maintenance of a constant coolant contact angle or time to interface is deemed to be constant within the limits of performance of the machine. In some embodiments, the maintenance of a constant time to interface is accomplished by maintaining a constant time within a predetermined tolerance range, such that the nozzle is moved relative to the wheel or workpiece in intermittent steps. Similarly, the maintenance of a constant coolant contact angle may be accomplished by maintaining a constant angle within a predetermined tolerance range, such that, again, the nozzle is moved relative to the wheel workpiece in intermittent steps 
     All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference. Any description of certain embodiments as “preferred” embodiments, and other recitation of embodiments, features, or ranges as being preferred, is not deemed to be limiting, and the invention is deemed to encompass embodiments that are presently deemed to be less preferred. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended to illuminate the invention and does not pose a limitation on the scope of the invention. Any statement herein as to the nature or benefits of the invention or of the preferred embodiments is not intended to be limiting. This invention includes all modifications and equivalents of the subject matter recited herein as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context. The description herein of any reference or patent, even if identified as “prior,” is not intended to constitute a concession that such reference or patent is available as prior art against the present invention.