Patent Publication Number: US-2009220312-A1

Title: Machine tool with chip processing function

Description:
FIELD OF THE INVENTION 
     The present invention relates to a machine tool with a chip guiding function which is used for turning operation or the like, and in particular, to a machine tool with a chip processing function which is suitable for ductile materials. 
     BACKGROUND OF THE INVENTION 
     In recent years, with developed mass production and improved performance of industrial products, there has been a demand for increased efficiency and precision of cutting operation. To meet the demand, appropriate control of chips and an increase in cutting speed are required. In connection with the cutting operation, chip controllability, tool life, cutting resistance, and machining accuracy are called four machinability items. Efforts have been made to improve each of the items. In particular, poor chip controllability is the worst factor hindering automation because of entangled chips and the like. 
     To improve the chip controllability, a chip breaker is generally used to heavily curl and destroy a chip into pieces (see, for example, “NC Machine Tool Usage Manual” edited by Tool Engineer editorial department of the Publishing Taiga Shuppan Co, Ltd, Sep. 10, 1990, pp. 94-95). Furthermore, a configuration has been proposed in which a hollow guide path for chips composed of a cover, a pipe, or the like is formed on a rake face of a cutting tool (see, for example, the Unexamined Japanese Patent Application Publication (Tokkai-Sho) No. 52-142379). A cut-off tool has been proposed which includes a guide groove formed in a rake face and through which the chip is passed all over the width thereof. Additionally, a cutting tool for counter boring has been proposed in which an edge portion leading to a cutting edge line is provided in the center of a rake face to prevent the chip from being rolled (see the Unexamined Japanese Patent Application Publication (Tokkai-Hei) No. 7-237005). 
     Furthermore, to reduce the cutting resistance, a technique of performing cutting operation while pulling the chip has been proposed (see “Effects of Tension on Chips during Cutting” Kazuo NAKAYAMA, Precision Machine, 30-1 (1964), pp. 46-52). When a cutting speed is increased to allow the cutting operation to be efficiently achieved, the quantity of cutting heat increases to reduce the tool life. Thus, the condition of a finished surface is degraded. To prevent this, cutting oil may be used. However, the use of the cutting oil may disadvantageously affect environments. The above-described technique of performing cutting operation while pulling the chip is expected to be effective for reducing the cutting resistance and the cutting heat and thus the wear of the tool. 
     With the chip breaker, a chip needs to be somewhat fragile so that the force of flow of the chip can be utilized to curl and destroy the chip into pieces. Thus, the chip breaker often fails to act on ductile materials such as steel used for press working and heat resistant alloys. This may result in the entangled chip or the damaged finished surface. Furthermore, even where the chip breaker functions properly, the cutting resistance varies periodically, possibly posing a vibration problem or reducing the machining accuracy. 
     The technique of forming, in the rake face of the cutting tool, the hollow guide path composed of a cover, a pipe, or the like or the guide groove through which a chip is passed is effective provided that a chip of the same width always flows in the same direction without being heavily curled. However, the width, direction, and curling of the chip vary depending on cutting conditions. If the width of the hollow guide path or guide groove is increased to allow for variation in chip width, the chip may be curled in the hollow guide path or guide groove. Furthermore, the flow direction of the chip also varies depending on cutting conditions. Thus, if the hollow guide path or guide groove has a narrow inlet, the chip is likely to be caught at the inlet. On the contrary, even if the inlet is enlarged, the chip may come into angled contact with the inner wall surface of the hollow guide path or guide groove and be caught thereon. Thus, the chip is jammed in the hollow guide path or guide groove. Consequently, putting the hollow guide path or guide groove to practical use is difficult. 
     The technique of providing the edge line portion in the center of the rake face is effective only on the counter boring for preventing the chip from being rolled. The technique cannot be applied to general turning operations. That is, in the counter boring processing, the original flow direction, width, and occurrence position of the chip are fixed. An edge portion leading along the chip flow direction to the cutting edge line is provided in the center of the chip. Thus, this technique fails to act on the general turning operations, in which the original flow direction, width, and occurrence position of the chip vary depending on the machining conditions. 
     In normal cutting, the chip flows in a spiral form. This is because a sideward curl and an upward curl occur during formation of the chip. The upward curl is perpendicular to the rake face and results from a secondary flow of the chip in the vicinity of the rake face of the tool caused by friction between the chip and the rake face. The sideward curl is parallel to the rake face and results from a sideward flow of a free surface side of the chip during generation of the chip. 
     Each curl direction is combined with the flow direction to determine a flow path for the chip. As described above, the cause of the curl varies with the type of the curl. Thus, the upward and sideward curls need to be separately dealt with in order to correct the curled chip. Furthermore, to regulate the flow path for the chip, not only each curl direction but also the flow direction needs to be regulated. 
     On the other hand, the results of basic studies indicate the technique of performing while pulling the chip is effective for reducing the cutting resistance. However, since no practical method for pulling the chip is available, the technique has not been put to practical use for a long time. 
     Even where for example, a roller sandwichingly feeding the chip is provided as means for pulling the chip, the flow path for the chip needs to be regulated in order to allow a tip portion of the chip to be guided to the roller during the initial period of formation of the chips. Without the regulation, the roller fails to catch the tip portion of the chip and thus cannot be put to practical use. Since the chip may be curled and the flow direction may vary depending on the cutting conditions or the like, regulating the flow path is difficult. 
     Provided that a ductile chip can be guided to a desire position without the need to destroy the chip into pieces, not only consecutive chip processing but also a technique of performing cutting with the chip under tension can be achieved. Then, the cutting resistance, required power, resulting heat, and the like can be reduced to improve the machinability in general. At the same time, cutting efficiency can be improved, and the tool life can be prolonged. 
     An object of the present invention is to provide a machine tool with a chip processing function which enables the sideward curl to be corrected without causing a jam, thus allowing the chip to be guided in a desired direction, the machine tool enabling consecutive chip processing and reducing the cutting resistance, required power, resulting heat, and the like to provide improved cutting efficiency and prolonged tool life. 
     Another object of the present invention is to enable the chip to be more reliably guided to a tensile force applying means. 
     Yet another object of the present invention is to perform such control as allows the tensile force applying means to reliably catch the tip portion of the chip even with a change in the cutting conditions. 
     Still object of the present invention is to provide a machine tool with a chip control function which performs such control as allows the chip to be guided in a desired direction and enables consecutive chip control, the machine tool reducing the cutting resistance, required power, resulting heat, and the like to provide improved cutting efficiency and prolonged tool life. 
     Further another object of the present invention is to allow the chip to be continuously fed under tension and also to allow appropriate tension to be easily applied. 
     Further another object of the present invention is to allow friction between the chip and the rake face to be offset by a tensile force to enable a more effective reduction in cutting resistance. 
     Further another object of the present invention is to facilitate processing of the chip and to increase the range of available options for a chip processing means. 
     SUMMARY OF THE INVENTION 
     A first configuration according to the present invention provides a machine tool with a chip processing function which brings a cutting tool into abutting contact with a workpiece for cutting, the machine tool being characterized by comprising a tensile force applying means provided on or in a vicinity of the cutting tool to apply a tensile force to a chip continuing from the workpiece and flowing from a cutting edge of the cutting tool, and a chip guiding means for guiding the chip to the tensile force applying means, and in that as the chip guiding means, the machine tool includes guide shape portion extending linearly away from a cutting edge line located at an edge of a rake face or a vicinity of the cutting edge line with respect to the cutting edge line to guide the chip, and the guide shape portion has a smaller width than the chip and is recessed or projected with respect to the rake face, and in that a part of the chip flowing onto the rake face is plastically deformed during generation of the chip, and the guide shape portion fits the plastically deformed portion to guide the chip. The guide shape portion may be a groove or a protrusion. 
     In this configuration, the chip guiding means is provided to guide the chip to the tensile force applying means, thus allowing processing to be performed with the chip under tension. Thus, consecutive chip processing can be carried out even on ductile materials such as press steel, heat resistant alloys, and soft aluminum on which the chip breaker fails to act. Since chip controllability is improved, automation for the ductile materials is facilitated, thus improving yield and machining accuracy. Furthermore, a technique of performing cutting with the chip under tension can be implemented. The cutting resistance, required power, resulting heat, and the like which are associated with friction can be reduced to improve the machinability in general. At the same time, the cutting efficiency can be improved, and the tool life can be prolonged. The prolonged tool life resulting from the reduced cutting resistance means, in the opposite sense, that with the tool life remaining unchanged, faster or heavier cutting can be achieved. The present embodiment thus increases efficiency compared to the conventional art. Furthermore, where a cutting-direction component (radial force) of a cutting force is offset by the tensile force, the amount of cut is prevented from varying depending on the cutting force. This significantly contributes to improving the machining accuracy. 
     Since the recessed or projected guide shape portion having the smaller width than the chip is provided, where the workpiece is pressed against the rake face for cutting to form the flowing chip, a part of a surface of the chip which contacts with the rake face is plastically deformed by the guide shape portion. The plastically deformed portion fits the guide shape portion to allow the chip to be guided. Thus, the flow direction and sideward curl of the chip are corrected. When the guide shape portion is the groove, a protrusion-shaped plastically deformed portion is formed on the surface of the chip which contacts with the rake face. The protrusion-shaped plastically deformed portion is fitted into the guide shape portion to allow the chip to be guided. When the guide shape portion is the protrusion, a groove-shaped plastically deformed portion is formed in the surface of the chip which contacts with the rake face. The guide shape portion is fitted into the groove-shaped plastically deformed portion to guide the chip. 
     The guide shape portion creates the plastically deformed portion on the rake face side of the chip so as to fit and guide the chip. Thus, the flow direction and curl of the chip are corrected. Consequently, the chip can be smoothly guided even with variation in chip width. 
     That is, in a guide path such as a hole or a cover through which the chip is passed, excess width may cause the chip to be curled inside the guide path to come into abutting contact with an inner wall surface of the guide path or may change the flow direction of the chip to cause the chip to be caught at the inlet. This may result in a jam. However, the present technique can prevent such a jam problem. Furthermore, unlike the guide path such as a hole or a cover through which the chip is passed, the guide shape portion plastically deforms and fits the part of the rake face side of the chip. Thus, the guide shape portion not only guides the chip but also corrects the curl and flow direction of the chip. 
     The plastic deformation of the chip by the guide shape portion is a part of the plastic deformation required to form the chip, and does not prevent the flow of the chip. 
     The guide shape portion such as the guide groove or guide protrusion may be formed on the cutting edge line. However, the guide shape portion is preferably formed not on the cutting edge line but so as to extend from the vicinity of the cutting edge line because in this case, the guide shape portion avoids degrading a finished surface of a workpiece. Preferably, the depth of the guide groove or the height of the guide protrusion increases gradually with the distance from the cutting edge line, and after reaching a given depth or height, the guide shape portion further extends with the depth or height maintained. 
     As the chip guiding means, the machine tool includes, in addition to the guide shape portion such as the guide groove, a cover covering the rake face of the cutting tool to form a guide path between the rake face and the cover through which the chip passes. 
     Where for example, surfaces of a workpiece located in the respective directions are consecutively processed, for example, an angular relationship between the cutting tool and the workpiece surface may vary, preventing the chip from being reliably guided simply by the guide shape portion. In this case, the cover allows the chip to be more reliably guided. Combination of the correction by the guide shape portion such as the guide groove with regulation by the cover prevents the curled chip from being jammed in the guide path compared to the simple use of the cover. 
     As the chip guiding means, the rake face may be formed as a projecting curved surface such that a cross section of the rake face which is perpendicular to the cutting edge line is shaped like a projecting curve. In this case, the rake face may be the projecting curved surface whether or not the guide shape portion such as the guide groove is provided. 
     Where the rake face is the projecting curved surface, the chip conforms to the projecting curved surface of the rake face and is inhibited from being curled upward. In conventional tools, the rake face is formed as a recessed curved surface so as to positively curl the chip upward. In contrast, the present invention uses the projecting curved surface to eliminate the upward curl. Owing to the use of the projecting curved surface, the present cutting tool is applicable to turning operations in general, unlike those which use edge lines. Additionally, the upward curl relatively insignificantly affects the guidance of the chip to the desired position. Thus, the rake face has only to be the projecting curved surface where specially required. 
     As the chip guiding means, the machine tool may include a tool-or-the-like posture changing mechanism changing a posture of the cutting tool, the guide path, the tensile force applying means, or the like with respect to the workpiece, and a tool-or-the-like posture control means for allowing the tool-or-the-like posture changing mechanism to perform a posture changing operation according to a set rule. 
     The flow direction of the chip varies depending on the cutting conditions. Thus, the tool-or-the-like posture changing mechanism and the tool-or-the-like posture control means are provided to change the posture of the tool or the like depending on the cutting conditions. This enables the tensile force applying means to reliably catch the tip portion of the chip. The set rule is set such that the chip is directed toward the tensile force applying means depending on the cutting conditions. If the posture of the tool or the like is thus controlled, the guide groove need not be provided. 
     As the chip guiding means, the machine tool may include a guide path member internally forming a guide path through which the chip passes, a guide path posture changing mechanism changing a posture of the guide path member with respect to the workpiece, and a guide path posture control means for allowing the guide path posture changing mechanism to perform a posture changing operation according to a set rule. 
     Changing the posture of the guide path depending on the cutting conditions also enables the tensile force applying means to reliably catch the tip portion of the chip. Where the posture of the guide path is thus controlled, the guide groove is not provided. 
     Another configuration according to the present invention provides a machine tool with a chip processing function which brings a cutting tool into abutting contact with a workpiece for cutting, the machine tool being characterized by comprising a tensile force applying means provided on or in a vicinity of the cutting tool to apply a tensile force to a chip continuing from the workpiece and flowing from a cutting edge of the cutting tool, and a guiding means for guiding the chip to a chip inlet of the tensile force applying means, and in that as the chip guiding means, the machine tool includes a chip flow direction control means for regulating, for a driving source allowing the cutting tool to perform cutting and feeding the cutting tool, a relationship between a cut amount and a feed amount according to a set relationship, and the set relationship specifies that a flow direction of the chip determined by the cut amount, the feed amount, and a tool shape is such that the chip is directed to within a range within which the chip can receive a chip tip portion of the tensile force applying means. 
     The range within which the chip tip portion of the tensile force applying means can be received may be a part of the width of a pair of rollers sandwichingly pulling the chip within which the chip can be sandwiched between the rollers. Furthermore, if an inlet guide is provided on the tensile force applying means, the range is such that the chip can be guided through the inlet guide. 
     The flow direction of the chip varies depending on the relationship between the cut amount and the feed amount. Thus, by regulating the relationship between the cut amount and the feed amount as described above, the chip can be guided to the tensile force applying means without the need to provide the guide path. The period of the control by the chip flow direction control means may be limited to an initial cutting period from start of the cutting until the chip is caught by the tensile force applying means. Thereafter, the relationship between the cut amount and the feed amount can be changed. Alternatively, the chip flow direction control means may perform the control throughout the period of a single cutting process. The control by the chip flow direction control means may be used in combination with the guide path, through which the chip is guided. In this case, the chip can be more reliably guided to the tensile force applying means. 
     The tensile force applying means enables consecutive chip processing, and is effective for reducing the cutting resistance, required power, and the resulting heat as is the case with the first configuration. 
     In the present invention, the tensile force applying means may comprise a pair of rollers that can rotate with the chip sandwiched between the rollers and a servo motor rotating one of both of the rollers. 
     The rollers allow the chip to be continuously fed under tension. Furthermore, the servo motor enables speed control and torque control, allowing appropriate tension to be applied. 
     Where the tensile force applying means comprises the rollers and the servo motor, the machine tool may include a cutting synchronized rotation control means for controlling a rotation speed of the servo motor rotating the rollers so that a speed at which the chip is pulled by rotation of the rollers equals a cutting speed at which the rotating workpiece is cut by the cutting tool. 
     Making the chip pulling speed and the cutting speed equal allows the tensile force to substantially offset the friction between the chip and the rake face. 
     Where the tensile force applying means comprises the rollers and the servo motor, the machine tool may include a force sensor measuring a force acting between the cutting tool and the workpiece, and an acting force-based control means for mainly controlling a torque of the servo motor rotating the rollers, according to a detection output from the force sensor. 
     Where the force sensor is located so as to detect a resultant force acting on the tensile force applying means and the cutting tool, the resultant force is fed back to allow the torque of the servo motor to be operated. This in turn allows the friction between the chip and the rake face to be substantially offset. For example, feedback control is performed so that a detected value from the force sensor approaches zero. Alternatively, where the force sensor is located so as to detect only a force acting on the cutting tool, the servo motor is instructed to offer a torque offsetting the detected value from the force sensor. This allows the friction between the chip and the rake face to be substantially offset. 
     According to the present invention, the machine tool includes a chip processing means for severing or winding the chip having passed through the tensile force applying means. 
     Severing or winding the chip facilitates the processing. Since the tensile force is interposed between the tool and the chip processing means, the force of the chip processing means is prevented from acting directly on the portion of the chip which contacts with the tool. The range of available options for the chip processing means can be increased. Furthermore, a distance from the cutting tool to the chip processing means can be easily increased. The location and size of the chip processing means can be more freely determined. 
     The first configuration according to the present invention provides the machine tool with the chip processing function comprising the tensile force applying means provided on or in the vicinity of the cutting tool to apply the tensile force to the chip continuing from the workpiece and flowing from the cutting edge of the cutting tool, and the guiding means for guiding the chip to the tensile force applying means. As the chip guiding means, the machine tool includes the guide shape portion extending linearly away from the cutting edge line located at the edge of the rake face or the vicinity of the cutting edge line with respect to the cutting edge line to guide the chip, and the guide shape portion has the smaller width than the chip and is recessed or projected with respect to the rake face. A part of the chip flowing onto the rake face is plastically deformed, and the guide shape portion fits the plastically deformed portion to guide the chip. Thus, the sideward curl can be corrected and the chip can be directed in the desired direction, without causing a jam. Consecutive chip processing can be carried out, and the technique of performing cutting with the chip under tension can be implemented. Consequently, the cutting resistance, required power, resulting heat, and the like which are associated with friction can be reduced to improve the machinability in general. At the same time, the cutting efficiency can be improved, and the tool life can be prolonged. 
     Where as the chip guiding means, the machine tool includes the cover covering the rake face of the cutting tool to form the guide path between the rake face and the cover through which the chip passes, the chip can be more reliably guided. 
     Where, as the chip guiding means, the rake face is formed as the projecting curved surface such that the cross section of the rake face which is perpendicular to the cutting edge line is shaped like the projecting curve, the upward curl of the chip can be corrected. Thus, the chip can be more reliably guided to the tensile force applying means. 
     Where, as the chip guiding means, the machine tool includes the tool-or-the-like posture changing mechanism changing the postures of the cutting tool, the guide path, the tensile force applying means, and the like with respect to the workpiece, and the tool-or-the-like posture control means for allowing the tool-or-the-like posture changing mechanism to perform the posture changing operation according to the set rule, control can be performed such that the tensile force applying means can reliably catch the tip portion of the chip even with a change in the cutting conditions. 
     Where, as the chip guiding means, the machine tool includes the guide path member internally forming the guide path through which the chip passes, the guide path posture changing mechanism changing the posture of the guide path member with respect to the workpiece, and the guide path posture control means for allowing the guide path posture changing mechanism to perform the posture changing operation according to the set rule, control can also be performed such that the tensile force applying means can reliably catch the tip portion of the chip even with a change in the cutting conditions. 
     The another configuration according to the present invention provides the machine tool with the chip processing function comprising the tensile force applying means provided on or in the vicinity of the cutting tool to apply the tensile force to the chip continuing from the workpiece and flowing from the cutting edge of the cutting tool, and the guiding means for guiding the chip to the chip inlet of the tensile force applying means. As the chip guiding means, the machine tool includes the chip flow direction control means for regulating, for the driving source allowing the cutting tool to perform cutting and feeding the cutting tool, the relationship between the cut amount and the feed amount according to the set relationship, and the set relationship is such that the flow direction of the chip determined by the cut amount, the feed amount, and the tool shape is such that the chip is directed to within the range within which the chip tip portion of the tensile force applying means can be received. Thus, control can be performed so as to direct the chip in the desired direction. Consecutive chip processing can be carried out, and the technique of performing cutting with the chip under tension can be implemented. Consequently, the cutting resistance, required power, resulting heat, and the like which are associated with friction can be reduced to improve the machinability in general. At the same time, the cutting efficiency can be improved, and the tool life can be prolonged. Additionally, the chip flow direction also varies depending on the shape (mainly the nose radius) of the tool used. Thus, the set relationship may vary depending on the nose radius or the like. 
     When the tensile force applying means comprises the pair of rollers that can rotate with the chip sandwiched between the rollers and the servo motor rotating one of both of the rollers, the chip can be continuously fed under tension. Furthermore, the appropriate tension can be easily applied. 
     In this case, where the machine tool includes the cutting synchronized rotation control means for controlling the rotation speed of the servo motor rotating the rollers so that the speed at which the chip is pulled by the rotation of the rollers equals the cutting speed at which the rotating workpiece is cut by the cutting tool, the friction between the chip and the rake face can be substantially offset by the tensile force. Thus, the cutting resistance can be more effectively reduced. 
     When the machine tool includes the force sensor on either the cutting tool or the workpiece, and the acting force-based control means for controlling the torque of the servo motor based on the detection output from the force sensor, the friction between the chip and the rake face can also be substantially offset by the tensile force. Thus, the cutting resistance can be more effectively reduced. 
     When the machine tool includes the chip processing means for severing or winding the chip having passed through the tensile force applying means, the processing of the chip is facilitated. Furthermore, the range of available options for the chip processing means can be increased. 
     Other features, elements, processes, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a diagram illustrating a conceptual configuration of a machine tool with a chip processing function according to an embodiment of the present invention,  FIG. 1B  is a perspective view of a tip portion of the cutting tool, and  FIG. 1C  is a front view of a tip and a cover of the cutting tool. 
         FIG. 2  is a perspective view of the cutting tool. 
         FIGS. 3A and 3B  are plan views of examples of the tip of the cutting tool. 
         FIGS. 4A and 4B  are enlarged sectional views showing guide grooves in the cutting tool. 
         FIG. 5  is a perspective view of the cutting tool provided with the cover. 
         FIG. 6  is a front view and an exploded plan view showing the cover and the tip. 
         FIG. 7  is a perspective view of the cutting tool provided with a tensile force applying means. 
         FIG. 8  is a front view of the tip and the cover, showing a variation of the guide grooves in the cutting tool. 
         FIG. 9  is an exploded plan view of an example in which a guide path forming member is provided in the cutting tool. 
         FIG. 10  is a diagram illustrating a test method for the guide grooves in the cutting tool. 
         FIG. 11  is a diagram showing test conditions for the tests. 
         FIG. 12  is another diagram illustrating a test method for the cutting tool. 
         FIG. 13  is a diagram showing the results of the tests. 
         FIG. 14  is a photograph showing the test result. 
         FIG. 15  is a diagram illustrating a method for testing on upward curl in the cutting tool. 
         FIG. 16  is another diagram illustrating the test method. 
         FIG. 17  is a graph showing the test results. 
         FIG. 18  is a graph showing the results of simulation of chip stretch cutting. 
         FIG. 19  is a graph showing the results of the simulation with rake angle varied. 
         FIGS. 20A and 20B  are plan views of examples of the tip corresponding to variations of the cutting tool. 
         FIG. 21A  is a partly enlarged sectional view of the cutting tool in  FIG. 20A , and  FIG. 21B  is a diagram illustrating a relationship between a guide protrusion and the tip in the cutting tool. 
         FIG. 22  is a block diagram showing a conceptual configuration of a machine tool with a chip processing function corresponding to another embodiment of the present invention. 
         FIG. 23  is a front view of a lathe that is a machine tool main body of the machine tool. 
         FIG. 24  is a plan view of the machine tool main body. 
         FIG. 25  is a diagram illustrating an essential part of a conceptual configuration of a machine tool with a chip processing function according to yet another embodiment of the present invention. 
         FIG. 26  is a diagram illustrating a conceptual configuration of a machine tool with a chip processing function according to still another embodiment of the present invention. 
         FIG. 27  is a diagram illustrating a concept of chip direction control in the machine tool with the chip processing function. 
         FIG. 28  is a diagram illustrating an essential part of a conceptual configuration of a machine tool with a chip processing function according to further another embodiment of the present invention. 
         FIG. 29  is a diagram illustrating an essential part of a conceptual configuration of a machine tool with a chip processing function according to further another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the present invention will be described with reference to  FIGS. 1 to 22 .  FIG. 1  schematically shows a machine tool with a chip processing function. The machine tool brings a cutting tool  1  into abutting contact with a rotating workpiece W for cutting. The machine tool includes a tensile force applying means  11  for applying a tensile force to a chip  10  continuing with a workpiece W and flowing from a cutting edge line  5  of the cutting tool  1 , a chip guiding means  6  for guising the chip  10  to the tensile force applying means  11 , and a chip processing means  12  for processing the chip  10  having passed through the tensile force applying means  11 . Furthermore, a guide path (not shown in the drawings) such as a pipe is provided between the tensile force applying means  11  and the chip processing means  12  so that the chip  10  is passed and guided through the guide path. The chip processing means  12  is a device that carries out a process of severing or winding the chip  10 . 
     The workpiece W is rotated by a spindle  14 . The cutting tool  1  is attached to a tool rest  15  that is movable in two orthogonal axial directions. The tensile force applying means  11  is provided on or in the vicinity of the cutting tool  1 . 
     The cutting tool  1  is a cutting tool with a chip guiding function which includes the chip guiding means  6 . The chip guiding means  6  is composed of a guide groove  7  that is a guide shape portion formed in a rake face  4  and a cover  8  covering the rake face  7 . The cover  8  need not be necessarily provided. 
     The cutting tool  1  is a throw-away turning tool comprising a shank  2  serving as a shank portion, and a tip  3  mounted on a tip mounting seat portion  2   a  located at a tip portion of the shank  2 . The tip mounting seat portion  2   a  is formed as a cutout recessed portion. The tip  3  is fixed to the shank  2  with a fastener  9  such as a set screw which is inserted through a central mounting hole. The tip  3  is a component serving as a cutting edge and has a triangular planar shape. A surface of the tip  3  which lies opposite a surface thereof attached to the shank  2  makes up the rake face  4 . Each corner of the rake face  4  is formed like a circular arc, that is, a circular-arc nose portion is formed at the corner. The circular-arc portion forms a cutting edge line  5 . In the tip  3 , the cutting edge line  5  located at a use portion  2   b  corresponding to a leading end of the shank  2  is used for processing. However, where the cutting edge line  5  at the use position is worn away, the tip  3  is removed and re-fixed such that another cutting edge line  5  is located at the use portion  2   b . Instead of being formed as the circular-arc corner, the cutting edge line  5  may be formed on each side of the tip  3 . Furthermore, the tip  3  may be rectangular. 
     The cutting tool  1  is not limited to the throw-away cutting tool but may be a tool bit in another form or a solid turning tool (also referred to as a solid tool) made wholly of the same material. However, the throw-away turning tool will be described below by way of example. 
     The guide groove  7  extends from the vicinity of the cutting edge line  5  to guide the chip  10 . The guide groove  7  extends from the vicinity of the corner of the tip  3  to an opposite side. In the present embodiment, the guide groove  7  is formed to become gradually deeper from a position close to the cutting edge line  5 . Thus, in the figure, the guide groove  7  is shown continuing from the cutting edge line. However, the guide groove  7  is not formed on the cutting edge line  5 . The guide groove  7  becomes gradually deeper from the vicinity of the cutting edge line  5  and then extends at a constant depth. The guide groove  7  need not necessarily continue to the opposite side but may be shaped to become gradually shallower from the middle of the guide groove  7  so as to reach the rake face  4 . The guide groove  7  may extend from the cutting edge line  5 . However, where the guide groove is formed to extend from the vicinity of the cutting edge line  5  without being formed on the cutting edge line, the guide groove  7  is prevented from degrading a finished surface. This is advantageous for the surface roughness of the finished surface. 
     The guide groove  7  has a smaller width than the chip  10  so that a rake face-side part  10   a  of the chip  10  is fitted into the guide groove  7  so as to allow the chip  10  to be guided. The width of the chip  10  varies depending on the amount of cut and the like. However, conditions under which the cutting tool  1  can be used are determined based on a cutting load and machining accuracy. Thus, the range of the width of the chip  10  is determined by using the cutting tool  1  under appropriate use conditions. The width of the guide groove  7  is set to be smaller than that of the chip  10  resulting from the use of the cutting tool  1  under the appropriate use conditions. In the present example, the guide groove  7  extends from the center of the cutting edge line  5  having the circular-arc planar shape. 
     For simplification,  FIGS. 1 and 2  show only the guide groove  7  extending from the cutting edge line  5  located at the use portion. However, in reality, the guide groove  7  is formed so as to extend from all the cutting edge lines  5  located at the respective corners of the tip  3  as shown in  FIG. 3A . Thus, the guide grooves  7  cross one another in the center of the chip  3 . In the present example, the fastener  9  fixing the tip  3  makes up the rake face  4 . A part of each of the guide grooves  7  is formed at the position of the fastener  9 . 
     The guide groove  7  has, for example, such a circular-arc sectional shape as shown in  FIG. 4A . However, as in the case of an example shown in  FIG. 11 , the guide groove  7  may have a cross section in which the internal opposite sides of the groove are parallel to each other and in which a bottom surface of the groove is shaped like a circular arc, or a rectangular cross section. The guide groove  7  is formed by, for example, electric discharge machining. 
     The guide groove  7  is not limited to a single guide groove, but a plurality of the guide grooves  7  may be formed parallel to one another, for example, as shown in  FIGS. 3B and 4B . For example, the number of the guide grooves  7  may be two or three or at least three. Positions on the rake face  4  where the plurality of guide grooves  7  are formed exhibit a corrugated sectional shape. The entire rake face  4  may exhibit such a corrugated sectional shape. For simplification,  FIGS. 3B and 4B  also show only the guide grooves  7  extending from the one cutting edge line  5  located at the corresponding corner. However, the guide groove  7  extends from each of the other cutting edge lines  5  located at the respective corners as in the case of the illustrated portion of the rake face  4 . Furthermore, where the plurality of guide grooves  7  are formed in juxtaposition, the width of each of the guide grooves  7  is smaller than that of the chip  10 . However, the width of the guide groove group in which the plurality of guide grooves are arranged in juxtaposition may be larger than that of the chip  10 . 
     As shown in  FIGS. 5 and 6 , the cover  8  is a component that covers the rake face  4  to form a tunnel-like guide path  16  between the cover  8  and the rake face  4  through which the chip  10  passes. For example, a groove  8   a  is formed on a back surface of the cover  8  so that the guide path  16  is formed between the groove  8   a  and the rake face  4 . The guide path  16  is formed along the guide groove  7  corresponding to the use position  2   b  of the chip  3 . The guide path  16  has a width that allows the chip  3  to pass smoothly through the guide path  16 . The cross section of the guide path  16  may be shaped like a rectangle, a semicircle, or the like. 
     The cover  8  has, for example, substantially the same planar shape as the tip  3 . The cover  8  is fixed to the shank  2  with a fastener (not shown in the drawings). When having substantially the same planar shape as the tip  3 , the cover  8  is shaped to have an escape portion  8   b  formed by cutting off the vicinity of the corner corresponding to the use portion  2   b  of the tip (that is, the corner corresponds to the nose portion), in order to avoid obstructing a cutting operation. 
     The cover  8  may be formed flat. A wide groove (not shown in the drawings) that is wider than the chip may be formed on the rake face  4  of the tip  3 , with the guide groove  7  formed at the bottom of the wide groove. Alternatively, such a wide groove may be formed on both the cover  8  and the tip  3  so that the wide grooves on the opposite sides are combined together to internally form a guide path having sectional dimensions that allow the chip  10  to pass through. 
     Alternatively, the cover  8  may extend beyond the tip  3  onto a surface of the shank  2 . 
     If the plurality of guide grooves  7  are formed in juxtaposition in the rake face  4  as shown in  FIG. 8 , the guide path  16 , formed by the cover  8 , has a sectional shape that allows the chip  10  to pass through smoothly regardless of through which of the guide grooves  7  the chip  10  is guided. 
     As shown in  FIG. 7 , the tensile force applying means  11  is composed of a pair of rollers  17 ,  18  that can rotate while sandwiching the chip  10  between the rollers  17 ,  18 , and a servo motor  19  that rotates one or both of the rollers  17 ,  18 . In the present example, the roller  18 , located below in  FIG. 7 , is coupled directly to the servo motor  19  for rotation. The rollers  17 ,  18  are rotatably supported on a support frame  20  via a bearing (not shown in the drawings). The servo motor  19  is attached to the support frame  20 . The tensile force applying means  11  is attached to the shank  2  of the cutting tool  1  via the support frame  20 . An axial direction of the rollers  17 ,  18  is orthogonal to an extending direction of the guide groove  7 . 
     The tensile force applying means  11  may be attached to, instead of the cutting tool  1 , the tool rest  15  ( FIG. 1 ), a tool holder mounted on the tool rest  15  to hold the cutting tool  1 , or the like. 
     As shown in  FIG. 9 , a guide path forming member  21  making up a guide path  21   a  through which the chip  10  passes may be provided between the guide groove  7  and both rollers  17 ,  18  of the tensile force applying means  11 . The guide path  21   a  is formed so as to guide the chip  10  to between the pair of rollers  17 ,  18 . In the present example, the guide path forming member  21  is composed of a pipe and fixed to the shank  2 . When the guide path forming member  21  is provided, the cover  8  in  FIG. 5  may be omitted. Alternatively, both the cover  8  and the guide path forming member  21  may be provided. 
     The guide path forming member  21  may be provided on the support frame  20  of the tensile force applying means  11  so as to serve as a component of the tensile force applying means  11 . Furthermore, in the example shown in  FIG. 9 , the guide path forming member  21  extends from the vicinity of the guide groove  7 . However, the guide path forming member  21  may be provided only in the vicinity of the rollers  17 ,  18  so as to serve as an inlet guide. That is, the guide path forming member  21  may comprises a chip inlet of the tensile force applying means  11 . If the guide path forming member  21  is not provided as the inlet guide, the chip inlet of the tensile force applying means  11  corresponds to a portion of the pair of rollers  17 ,  18  the width of which is appropriate to sandwich the chip  10  between the rollers  17 ,  18 . 
     In  FIG. 1 , the sectional shape of the rake face  4  of the cutting tool  1  is a projecting curved surface such that a cross section of the rake face  4  which is perpendicular to the cutting edge line  5  is a projecting curve, as shown in  FIG. 16B . The rake face  4  may be a plane or may be a recessed curved surface such that a cross section of the rake face  4  which is perpendicular to the cutting edge line  5  is a recessed curve. 
     The cutting tool  1  configured as described above includes the guide groove  7 , having the smaller width than the chip  10 . Thus, as shown in  FIG. 10 , where during cutting, the workpiece is pressed against the rake face  4  to form the chip  10 , a plastically deformed portion  10   a  to be fitted into the guide groove  7  is formed on a part of the rake face  4  side of the chip  10  as a protrusion. The plastically deformed portion  10   a  making up the protrusion is fitted into the guide groove  7  and guided. Thus, a flow direction and a sideward curl of the chip  10  are corrected. The plastically deformed portion  10   a  created in the part of the rake face  4  side of the chip  10  is fitted into the guide groove  7 . Thus, the chip  10  can be smoothly guided even with variation in the width of the chip  10 . 
     With the conventional guide path such as a hole or a cover though which the chip is passed, a tip portion of the chip enters the path with the flow direction of the chip unregulated. Thus, the chip may be displaced from the inlet of the guide path and fail to be guided or come into angled contact with an inner wall surface of the guide path; in the latter case, the chip is likely to be jammed in the guide path. A change in cutting conditions generally changes the flow direction. This prevents the chip from being guided in a target direction, resulting in the displacement from the inlet or the angled contact. Furthermore, the chip may be curled in the guide path to come into abutting contact with the inner wall surface of the guide path. In this case, the chip is also jammed in the guide path. 
     In contrast, the guide groove  7  guides the chip fitting the guide shape portion. Instead of simply guiding the chip, the guide shape portion corrects the flow direction and curl of the chip, thus smoothly guiding the chip while preventing the chip from being jammed. The formation of the plastically deformed portion  10   a  of the chip  10  by the guide groove  7  is a part of the plastic deformation required to form the chip, and does not prevent the flow of the chip. 
     For the smooth guiding, the appropriate relationship between the width of the chip  10  and the width of the guide groove  7  is limited. The allowable width of the chip  10  at which the chip  10  can be smoothly guided with respect to the width of the guide shape portion is larger than that for the guide path through which the chip is passed. An example of the appropriate groove width is shown below as a test example. 
     The sideward curl of the chip  10  is thus corrected to allow the chip  10  to be guided in the desired direction. Thus, consecutive chip processing can be carried out even on ductile materials such as press steel and heat resistant alloys on which the chip breaker fails to act. Furthermore, a method of performing processing with the chip tensed by the tensile force applying means  11  can be implemented. 
     When a plurality of the guide grooves  7  are formed in juxtaposition in the rake face  4  as shown in  FIGS. 3B and 4B , even with a change in cutting conditions, any of the guide grooves  7  corresponds to an appropriate position for the chip  10  to allow the chip  10  to be guided. The guide groove  7  thus allows the chip to be reliably guided. That is, from which position on the cutting edge line  5  the chip  10  extends may vary depending on the cutting conditions. Thus, the single guide groove  7  may fail to guide the chip  10 . However, where the plurality of guide grooves  7  are formed, any of the guide grooves  7  corresponds to the appropriate position for the chip  10  to allow the chip  10  to be effectively guided. 
     When the cover  8  is provided, the chip  10  can be more reliably guided. When a cutting operation covers a wide range, for example, where surfaces of the workpiece W located in the respective directions are consecutively processed, for example, an angular relationship between the cutting tool  1  and the workpiece surface may vary, preventing the chip  10  from being reliably guided simply by the guide groove  7 . In this case, the cover  8  allows the chip  10  to be more reliably guided. Combination of the correction by the guide groove  7  with regulation by the cover  8  prevents the curled chip from being jammed in the guide path  16  compared to the simple use of the cover  8 . 
     When the guide path forming member  21  in  FIG. 9  is provided, the chip can be more reliably guided. The guide groove  7  guides the chip along the rake face  4  and thus fails to guide the chip to a position away from the cutting edge line  5 . However, the guide path forming member  21  allows the chip  10  to be reliably guided to a desired position away from the cutting edge line  5 . 
     When the rake face  4  is a projecting curved surface as shown in  FIG. 16B , the chip  10  conforms to the projecting curved surface of the rake face  4  to inhibit the upward curl. In conventional tools, the rake face is formed as a recessed curved surface so as to positively curl the chip upward. In contrast, the present embodiment uses the projecting curved surface to eliminate the upward curl. The cutting tool with the projecting curved surface is applicable to turning operations in general, unlike those which use edge lines. Additionally, the upward curl relatively insignificantly affects the guidance of the chip  10  to the desired position. Thus, the rake face has only to be the projecting curved surface where specially required. 
     In the above-described embodiment, the guide shape portion provided on the rake face  4  of the cutting tool  1  is the guide groove  7 . However, for example, as shown in  FIGS. 20 and 21 , the guide protrusion  7 A may be provided as the guide shape portion.  FIGS. 20A and 20B  show examples in which the guide protrusion  7 A is provided in the tip  3  shown in  FIGS. 3A and 3B , in place of the guide groove  7 .  FIG. 20A  shows the example in which one guide protrusion  7 A is provided for each of the cutting edge lines  5  at the respective corners.  FIG. 20B  shows the example in which a plurality of the guide protrusions  7 A are arranged parallel to one another for one of the cutting edge lines  5  at the respective corners. In either case, like the guide groove  7 , the guide protrusion  7 A extends from the cutting edge line  5  or the vicinity thereof to the opposite side. The guide protrusion  7  becomes gradually higher from the vicinity of the cutting edge line  5  and then continues at a constant height. The guide protrusion  7 A need not necessarily extend to the opposite side but may be shaped to become gradually lower toward the opposite side so as to reach the rake face  4 . The transverse sectional shape of the guide protrusion  7 A is a semicircle, for example, as shown in  FIG. 21A . Furthermore, the guide protrusion  7 A is formed to have a smaller width than the chip  10 . The tip  3 A with the guide protrusion  7 A is attached to the shank  3  in  FIG. 2  to comprise a cutting tool with a chip guiding function. The tip  3 A with the guide protrusion  7 A can be used in place of the tip  3 A with the guide groove  7  in the cutting tool  1  in the examples shown in the above-described figures. 
     If the cutting tool with guide protrusion  7 A is used to perform cutting as shown in  FIG. 21B , where the workpiece is pressed against the rake face  4  to form the chip  10 , a groove-shaped plastically deformed portion  10   a A is formed on a surface of the chip  10  which contacts with the rake face  4 . The guide protrusion  7 A is fitted into the groove-shaped plastically deformed portion  10   a  to guide the chip. Thus, as is the case with the guide groove  7 , the flow direction and curl of the chip  10  are corrected. The chip  10  can thus be smoothly guided in the desired direction. 
     Now, examples of tests for checking the effects of the guide groove  7  will be described. The tests were carried out on the cutting tool  1  including the tip  3  shown in  FIG. 3A , with the groove width and sectional shape of the guide groove  7  varied. The cover  8  in  FIG. 1  was not provided. 
     The cutting tool  1  of a nose radius of 0.8 mm and a tip angle of 60 degrees was used. With the width and thickness of the formed chip  10  taken into account, four types of guide grooves  7  shown in  FIG. 11  were each formed at a central position of the nose by wire-cut electric discharge machining. Processing experiments were carried out under cutting conditions including a cutting speed of 200 m/min for each of the four types shown in  FIG. 13  and an approach angle of 15 degrees as shown in  FIG. 12 . 
     An original chip flow angle (see  FIG. 10A ) shown in  FIG. 13  is an estimated value calculated based on the Colwell&#39;s empirical rule. In the present experiments, a target value to which the chip flow angle is controlled by the guide groove  7  is 45 degrees (see  FIG. 12 ) in all cases. Thus, for example, under conditions including a depth of cut of 0.2 mm and a feed of 0.08 mm/rev, the original flow angle is estimated to be forcibly changed from 19 degrees to about 26 degrees. 
       FIG. 13  shows the results of the experiments. First, grooves A and B with smaller cross sections will be considered. In the two cases with a depth of cut of 0.2 mm, the sideward curl was inhibited unlike in the case of ordinary flat tools, and the chip flow direction was generally controlled to the direction of the guide groove  7 . However, this condition prevented a perfectly straight chip from being discharged along the guide groove  7 . This is expected to be because the position of the cutting edge line  5  involved in the cutting and the position of the guide groove  7  were slightly misaligned. The misalignment is expected to be avoided by for example, aligning the position of the guide groove  7  with a cutting position or providing a plurality of the guide grooves  7 . At a depth of cut of 0.5 mm and a feed of 0.3 mm/rev, the cutting position and the groove portion aligned with each other. The chip was guided along the guide groove  7  to flow straight as shown by a photograph in  FIG. 14 . On the other hand, at a depth of cut of 1 mm and a feed of 0.2 mm/rev, the chip was curled sideward and failed to flow along the guide groove  7 . This is expected to be due to a weak force acting to correct the flow of the chip because of the small cross section of the groove. For a groove C, in the two cases with a depth of cut of 0.2 mm, the chip  10  flowed straight along the guide groove  7 . On the other hand, in the two other cases with larger depths of cut, the strength was insufficient, resulting in damage to the tip portion of the tool. For a groove D, in the two cases with a depth of cut of 0.2 mm, the chip  10  flowed imperfectly. This is expected to be because the groove width was excessively large for the chip  10 . On the other hand, in the two other cases with the larger depths of cut, the chip  10  flowed straight along the guide groove  7 . 
     The chip  10  flowing straight along the guide groove  7  was determined to have a projecting shape on the rake face  4  side thereof which is opposite to the groove shape. Thus, the intended mechanism was determined to be able to control the flow direction and sideward curl of the chip  10  at least under the appropriate range of conditions. 
     The results of tests on inhibition of the upward curl will be described. As shown in  FIG. 16B , a cutting tool was produced in which the rake face  4  had a curvature opposite to that of the upward curl. The cutting tool  7  did not include the guide groove  7 . Approximate two-dimensional cutting was performed as shown in  FIG. 15 . Changes in upward curl depending on the radius of curvature were measured. Tools were produced in which the rake face had a radius of 0 (ordinary tool), 0.035, 0.065, or 0.17 mm −1  respectively. Five processing experiments were carried out for each of the tools at a width of cut of 1 mm, a depth of cut of 0.1 mm, and a cutting speed of 200 m/min. The rake angle at a tip portion of the cutting edge line was adjusted to 0 degree. 
       FIG. 17  shows the measurement results of the curvature of the upward curl of the chip  10  formed by each of the tools.  FIG. 17  indicates that the curvature of the upward curl decreased consistently with the curvature of the rake face and that no upward curl occurred where the rake face had a curvature of 0.1 mm −1  (the rake face had a radius of 10 mm).  FIG. 17  also indicates that where the rake face had a larger curvature, the chip was curled in the opposite direction. 
     As described above, the test results indicate that the upward curl can be inhibited by providing the rake face of the cutting tool with a projecting curvature. 
     The effects of the tensile force applying means  11  will be described. When the tensile force applying means  10  is provided such that cutting is performed with the chip  10  tensed by the tensile force applying means  10 , the cutting resistance, required power, resulting heat, and the like can be reduced to improve the machinability in general. At the same time, the cutting efficiency can be improved, and the tool life can be prolonged. Furthermore, the machining accuracy is improved. The prolonged tool life resulting from the reduced cutting resistance conversely means that with the tool life remaining unchanged, faster or heavier cutting can be achieved. The present embodiment thus increases efficiency compared to the conventional art. When provided on the shank  2  of the cutting tool  1 , the tensile force applying means  11  can be easily located closer to the cutting edge line  5 . Thus, the flowing chip  10  can be easily guided to the tensile force applying means  11 . In particular, the tip portion of the chip  10  can be easily caught by the tensile force applying means. 
     The tensile force applying means  11  is composed of the pair of rollers  17 ,  18  sandwiching the chip  10  between the rollers  17 ,  18 . Thus, the chip  10  can be tensed while being continuously fed. Furthermore, the use of the servo motor  19  enables speed and torque to be controlled, allowing the appropriate tension to be applied. 
     Simulation results of stretch cutting will be described. In stretch cutting of the chip, a relationship between an apparent decrease in friction angle resulting from stretching of the chip and processing power was analyzed utilizing a simple shear angle model. The results of the analysis are shown in  FIGS. 18 and 19 .  FIG. 18  shows a case in which the rake angle is 0 degrees.  FIG. 19  shows a case in which the rake angle is −20 degrees. In both cases, the friction angle is 30 degrees. In connection with the processing power,  FIGS. 18 and 19  show results based on the “maximum shear stress theory”, a concept often used for simple cutting simulation, and results based on the “minimum energy theory”. The results based on both theories indicate that as shown in  FIGS. 18 and 19 , the processing power is minimized where the apparent friction angle is closed to 0 degree. In this case, the chip is pulled with a force canceling the frictional force exerted between the chip and the rake face of the cutting tool. 
     Consequently, by performing cutting while applying a tensile force to the chip so as to set the apparent friction angle to 0 degree, the processing power including the tensile force is minimized, thus reducing frictional heat. This in turn reduces degradation of the cutting tool and a decrease in machining accuracy. 
       FIGS. 22 to 24  show an example of a machine tool with a function of controlling the tensile force applying means  11  so that the apparent friction angle is set to 0 degree. 
     In  FIG. 22 , the machine tool is composed of a machine tool main body  30  and a processing machine control device  50 . The term “machine tool main body  30 ” as used herein refers to a mechanical portion of the machine tool, that is, the whole machine tool except for a control system. 
     In  FIGS. 23 and 24 , the machine tool main body  30  is composed of a turret type lathe. A spindle  14  is supported on a bed  31  via a head stock  32 . A spindle chuck  14   a  gripping the workpiece W is provided at a spindle head of the spindle  14 . The spindle  14  is rotationally driven by a spindle motor  33  comprising a servo motor or the like. 
     The tool rest  15  is composed of a turret tool rest with a polygonal front shape. The cutting tool  1  is attached to one of outer peripheral surface portions  15   a  making up side portions of the polygon. The cutting tool  1  is the cutting tool  1  with the chip guiding function which has the guide groove  7  and the tensile force applying means  11  as shown in  FIGS. 1 and 7 . Tools attached to the outer peripheral surface portions  15   a  of the tool rest  15  may include cutting tools such as a turning tool and rotary tools (not shown in the drawings) such as a drill and a milling head. However, at least one of the tools is the cutting tool  1  with the chip guiding function. 
     The turret type tool rest  15  is indexably mounted on an upper feed bar portion  34   b  of a feed bar  34  via a turret shaft  35 . The feed bar  34  is composed of a feed bar base  34   a  and the upper feed bar portion  34   b . The feed bar base  34   a  is installed on the bed  31  via guides  36  so as to advance and retract freely in a horizontal direction (X axis direction) orthogonal to an axial direction (Z axis direction) of the spindle. The upper feed bar portion  34   b  is mounted on the feed bar base  34   a  so as to advance and retract freely in the axial direction (Z) of the spindle. The feed bar base  34   a  is drivingly advanced and retracted freely by an X axis servo motor  37  via a feed screw mechanism  38 . The upper feed bar portion  34   b  is drivingly advanced and retracted freely by a Z axis servo motor  39  via a feed screw mechanism  40 . The feed bar base  34   a  and the upper feed bar portion  34   b  advance and retract to move the tool rest  15  in two orthogonal axial directions. Furthermore, an indexing motor  41  mounted on the upper feed bar portion  34   b  turns the tool rest  15  for indexation. 
     The machine tool main body  30  has the chip processing means  12  shown in  FIG. 1 . In the illustrated example, the tool rest  15  is located parallel to the spindle  14 . However, the tool rest  15  may be located orthogonally to or opposite the spindle  14 . The tool rest  15  is not limited to the turret type but may be shaped like comb teeth or may support only one cutting tool  1 . Furthermore, the machine tool with the chip processing function is applicable not only to the lathe but also to various machine tools using the cutting tool  1 . 
       FIG. 22  shows a conceptual configuration of the control system. The processing machine control device  50  is composed of a computerized numerical control device and a programmable controller. The processing machine control device  50  has an arithmetic control section  51  composed of a CPU (Central Processing Unit), a memory, and the like and a processing information storage means  52 . The control section  51  executes a processing program  53  to control components of the machine tool main body  30 . The processing information storage means  52  has a storage section for the machining program  53  and a parameter storage section  54 . The parameter storage section  54  stores information on various control operations as parameters. The processing program  53  contains axial movement commands for the axial (X axis, Z axis) directions of the tool rest  15 , an axial movement command corresponding to a rotation command for the spindle  14 , and the like. Non-execution command description portion of the processing program  53  contains information on the tool such as the shape of the cutting tool  1  (the nose radius, approach angle, and rake angle, and the angle of a guide groove, if any), and information on the workpiece such as the material and type of the workpiece W. 
     The arithmetic control section  51  has a basic control section  55 , an axial movement control section  56 , and a sequence control section  57 . The basic control section  55  reads the commands from the processing program  53  in the order in which the commands are stored. The basic control section  55  then allows the axial movement control section  56  to execute the axial movement commands. The basic control section  54  transfers the sequence commands from the processing program  53  to the sequence control section  57 . The sequence control section  57  controls sequence operations of the machine tool main body  30 , for example, rotational indexation of the turret tool rest  15  and opening and closing of a machine body cover (not shown in the drawings), in accordance with a built-in sequence program (not shown in the drawings). 
     The axial movement control section  56  is means for controlling axial movement of the X axis servo motor  37 , the Z axis servo motor  39 , the spindle motor  33 , and the like in the machine tool main body  30 . The axial movement control section  56  has a servo control means (not shown in the drawings) to perform closed loop control on the axial servo motors  37 ,  39 ,  33  in accordance with instruction values in the axial movement commands transmitted from the processing program  53  via the basic control section  55 . Information from position detectors (not shown in the drawings) such as pulse coders or encoders which are provided on the axial servo motors  37 ,  39 ,  33  is used for the closed loop control. 
     The processing machine control device  50  basically configured as described above includes a cutting speed calculating means  58  and a cutting synchronized rotation control means  59  which will be described below. The cutting speed calculating means  58  calculates the current cutting speed from the beginning to end of cutting. The cutting speed calculating means  58  calculates the cutting speed based on, for example, various pieces of information such as the processing program  53  which are stored in the processing information storage means  52 , and the current position information recognized by the axial movement control section  56 . The cutting speed is the peripheral speed of a portion of the workpiece W which is contacted by the cutting tool  1  and thus varies as the workpiece diameter decreases in association with the progress of the cutting. However, the current peripheral speed and thus the cutting speed can be calculated based on the current axial values and the rotation number of the spindle from the axes of the axial movement control section  56 , which performs the closed loop control, or the instruction values for the current axial values and the spindle rotation number obtained from the processing program  53 , and data on tool dimensions stored in the processing information storage means  52 . For example, provided that tool length data L is stored in the processing information storage means  52  and the X axis position (x) and the spindle rotation number (n) are obtained from the axial movement control section  56 , the cutting speed calculating means  58  calculates the position of the cutting edge from the X axis position (x) and the tool length data L. The cutting speed calculating section  58  further calculates the turning radius of the cutting edge position and then determines the peripheral speed based on the turning radius and the spindle rotation number (n). 
     The cutting synchronized rotation control means  59  controls the rotation speed of the servo motor  19  for rotationally driving the rollers  17 ,  18  so that the speed at which the chip  10  is pulled by rotation of the rollers  17 ,  18  of the tensile force applying means  11  (that is, the peripheral speed of the driving side of the rollers  17 ,  18 ) equals the cutting speed at which the rotating workpiece W is cut by the cutting tool  1 . The servo motor  19  includes the speed detector (not shown in the drawings). The cutting synchronized rotation control means  59  performs the closed loop control. 
     The term “synchronized rotation control” as used herein is not limited to strict synchronized control but means control such that the speed at which the chip  10  approximately equals the cutting speed. The cutting synchronized rotation control means  59  may perform such control as makes the chip  10  pulling speed approximately equal to the cutting speed. The speed detector for the servo motor  19  may be, for example, a tacho-generator. Furthermore, the servo motor  19  generally has an incremental pulse coder. Thus, the servo motor  19  may obtain speed information from the position detector such as the pulse coder or encoder. 
     As described above, the cutting speed calculating means  58  and the cutting synchronized rotation control means  59  are provided to perform control such that the speed at which the chip  10  is pulled by the rollers  17 ,  18  of the tensile force applying means  11  equals the cutting speed. Thus, the cutting can be achieved with a tensile force applied so as to set the apparent friction angle to approximately zero degree. This approximately minimizes the processing power including the tensile force, thus reducing frictional heat. This in turn reduces degradation of the cutting tool and a decrease in machining accuracy. Furthermore, the peripheral speed is calculated based on the information from the processing program  53  and the like or the current position information and the like from the axial movement control section  56 . Thus, the synchronized control of the tension speed and cutting speed can be performed without the need to add a dedicated sensor. The present embodiment thus requires only a simple configuration. 
     If the tensile force applying means  11  is composed of the rollers  17 ,  18  and the servo motor  19 , whether or not the chip  10  has been caught up between the rollers  17 ,  18  can be determined based on a current feedback value from the servo motor  19  (where the chip starts to be pulled, a load is imposed to maintain speed synchronization, thus increasing motor torque, that is, current). Thus, a means for determining whether or not the chip  10  has been caught up between the rollers  17 ,  18  (not shown in the drawings) may be provided. Furthermore, the means (not shown in the drawings) may be provided for issuing an alarm if the chip  10  is determined not to have been caught up between the rollers  17 ,  18  within a set time after the start of the cutting. 
       FIG. 25  shows another example of a machine tool with a function of controlling the tensile force applying means  11  so that the apparent friction angle is set to 0 degree. In this example, the machine tool includes a force sensor  61  located, for example, in the vicinity of the cutting edge line  5  of the cutting tool  1 , to detect a force acting on the cutting tool  1 . The machine tool also includes an acting force-based rotation control means  62  for controlling, depending on a value detected by the force sensor  61 , the force (motor torque) generated by rotation of the rollers  17 ,  18  of the tensile force applying means  11  to pull the chip  10 . The force sensor  61  detects, for example, the radial force of the cutting force and is installed by being imbedded in the shank  2  (between the cutting tool  1  and the tensile force applying means  11 ). The acting force-based rotation control means  62  gives a torque instruction to the servo motor so as to cancel an output from the force sensor  61 . The correspondence between the output from the force sensor  61  and the torque instruction value provided to the servo motor can be pre-calibrated. The force detected by the sensor  61  is generated by, for example, the friction between the chip  10  and the rake face  4 . Thus, offsetting this force allows the chip  10  to be controllably pulled so as to set the apparent friction angle to 0 degree. 
     In this example, the force sensor  61  is located to detect only the cutting force applied to the cutting tool  1 . However, the sensor may be placed between the tool rest or the like and the tool shank, supporting both the cutting tool  1  and the tensile force applying means  11 , in order to detect forces applied to both the cutting tool  1  and the tensile force applying means  11 . In this case, the portion supported by the force sensor is large in mass, resulting in reduced detection responsiveness. However, the sensor can instead detect the resultant force applied to both the cutting tool  1  and the tensile force applying means  11 . Thus, by increasing or reducing the torque instruction value provided to the servo motor so as to set the detected value of the resultant force to zero, the apparent friction angle can be accurately set to zero. 
     The present embodiment requires the force sensor  61  but is applicable to a case in which the current cutting speed cannot be calculated from the information stored in the processing machine control device. 
       FIG. 24  shows a machine tool with a chip processing function according to yet another embodiment of the present invention. In the present embodiment, the chip guiding means  6  is controllably guided by a chip flow direction control means  63 . In the present embodiment, the guide groove  7  in the rake face  4  need not be formed, or the chip flow direction control means  63  may be used in combination with the guide groove  7 . Furthermore, the cover  8  in  FIG. 1  may be or may not be provided. The guide path forming member  21  in  FIG. 9  may be provided. An inlet guide (not shown in the drawings) may be provided on the tensile force applying means  11 . 
     First, the principle of chip flow direction control will be described with reference to  FIG. 27 . When the workpiece W is cut in the X axis direction and fed in the Z axis direction to form a cut cross section w (a shaded area in  FIG. 27 ), the chip  10  flows in a direction F substantially orthogonal to a straight line L connecting points wa, wb together which are located at opposite ends of the cut cross section w (this rule is known as the Colwell empirical rule). Thus, given a tool shape, the chip  10  can be allowed to flow in a desired direction by regulating a relationship between the cut amount and the feed amount. 
     Based on the above-described rule, the chip flow direction control means  6  in  FIG. 26  determines the relationship between the cut amount and the feed amount such that the tip portion of the chip  10  is directed to within the range within which the chip  10  can receive a chip tip portion of the tensile force applying means  11 . The chip flow direction control means  6  regulates the relationship between the cut amount and the feed amount output by the axial movement control section  56  according to a set relationship. The set relationship specifies that the flow direction of the chip, determined by the cut amount, the feed amount, and the tool shape, is such that the chip is directed to within the range within which the chip can receive the chip tip portion of the tensile force applying means. 
     The relationship between the cut amount and the feed amount is generally determined by an instruction from the processing program  53 . The instruction from the processing program  53  varies the relationship between the cut amount and the feed amount. The period of the control by the chip flow direction control means  63  may be limited to an initial cutting period from the start of the cutting until the chip  10  is caught by the tensile force applying means  11 . Thereafter, the relationship between the cut amount and the feed amount may be changed. Alternatively, the chip flow direction control means  63  may perform the control throughout the period of a single cutting process. 
     If the period of the control by the chip flow direction control means  63  is limited to the initial cutting period, for example, where an NC program is pre-generated by CAM, the amount of time until the chip is caught may be predicted such that where that time elapses, the regulation is canceled and the cut amount and the feed amount are changed. Alternatively, a timer may be used to set the period during which the chip flow direction control means  63  performs the control. Alternatively, the control may be canceled where the tensile force applying means  11  is determined to successfully grip the chip  10 . When the tensile force applying means  11  is composed of the rollers  17 ,  18  and the servo motor  19 , whether or not the chip  10  is caught up between the rollers  17 ,  18  can be determined based on an output from the detector (or the force sensor  61 ) for the servo motor  19 . The control may be canceled after the determination. 
     In this configuration, the flow direction of the chip  10  is controllably regulated, thus allowing the cutting tool  1  to be simply configured. The remaining part of the configuration of the present embodiment is similar to that of the machine tool with the chip processing function described with reference to  FIG. 20 . Also in the present embodiment, the processing machine control device  50  include the above-described cutting speed calculating means  58  and a cutting synchronized rotation control means  59  to control the pulling speed of the tensile force applying means  11  in synchronism with the cutting speed. 
       FIG. 28  shows still another embodiment of the present invention. A machine tool with a chip processing function according to the present embodiment includes, as the chip guiding means  6 , a tool-or-the-like posture changing mechanism  64  that changes the posture of the cutting tool  1  with respect to the workpiece W, and a tool-or-the-like posture control means  65  for allowing the tool-or-the-like posture changing mechanism  64  to perform a posture changing operation according to a set rule. The tool-or-the-like posture changing mechanism  64  is provided on the tool rest  15  or a tool holder  66  provided on the tool rest  15 . The tool-or-the-like posture changing mechanism  64  rotates the cutting tool  1  and the like around, for example, an axis of the shank  2 . Alternatively, the tool-or-the-like posture changing mechanism  64  rotates the cutting tool  1  or the like around, for example, an axis passing through the center of the tool nose portion and parallel to the cutting direction. 
     The tool-or-the-like posture control means  65  is provided, for example, in the processing machine control device  50  described above with reference to  FIG. 22 . The set rule for the tool-or-the-like posture control means  65  specifies a relationship between the posture of the cutting tool  1  or the like and the processing conditions such as the cut amount, the feed amount, and the tool shape. According to the processing conditions obtained from the stored contents and the like of processing information storage means  52  ( FIG. 22 ), the tool-or-the-like posture control means  65  determines the posture of the cutting tool  1  so that the chip  10  is directed toward the tensile force applying means  11 . The set rule may be appropriately prepared based on simulation, test processing, or the like. 
     The tool-or-the-like posture changing mechanism  64  or the like may be provided in the cutting tool  1  in combination with the cutting tool  1  or alone without the guide groove  7 . Alternatively, the tool-or-the-like posture changing mechanism  64  may be used in combination with the cover  8  or the guide path forming member  21  in  FIG. 9 . 
     The flow direction of the chip  10  varies depending on the cutting conditions such as the cut amount, the feed amount, and the tool shape. Thus, by changing the posture of the tool or the like depending on the cutting conditions, the tip portion of the chip  10  can be guided to the tensile force applying means  11 , which can then catch the tip portion. 
     The period of the posture control of the tool or the like by the tool-or-the-like posture control means  54  may be limited to the initial cutting period from the start of the cutting until the chip  10  is caught by the tensile force applying means  11 . Alternatively, the tool-or-the-like posture control means  54  may perform the posture control throughout the period of a single cutting process. 
     The remaining part of the configuration of the present embodiment is similar to that of the machine tool with the chip processing function shown in  FIG. 22 . 
       FIG. 29  shows further another embodiment of the present invention. The machine tool with the chip processing function includes, as the chip guiding means  6 , a guide path forming member  21  provided between the cutting edge line  5  and both the rollers  17 ,  18  of the tensile force applying means  11  and internally forming the guide path  21   a  through which the chip  10  passes. The machine tool also include a guide path posture changing mechanism  67  that changes the posture of the guide path member  21  with respect to the workpiece W and a guide path posture control means  68  for allowing the guide path posture changing mechanism  67  to perform a posture changing operation according to a set rule. The angle of the guide path posture change mechanism  67  can be varied in the plane of the rake face using the center of the node portion of the cutting edge  5  as a pivotal center. The cover  8  in  FIG. 5  may be provided, and the guide path forming member  21 , the posture of which is changed by the guide path posture changing mechanism  67 , may be provided between the cover  8  and the rollers  17 ,  18 . 
     The guide path posture control means  68  is provided, for example, in the processing machine control device  50  described above with reference to  FIG. 22 . The set rule for the guide path posture control means  68  specifies a relationship between the direction of the guide path forming member  21  and the processing conditions such as the cut amount, the feed amount, and the tool shape. According to the processing conditions obtained from the stored contents and the like of a processing information storage means  52  ( FIG. 22 ), the guide path posture control means  68  determines the direction of the guide path forming member  21 . The set rule may be appropriately prepared based on simulation, test processing, or the like. 
     By thus changing the direction of the guide path forming member  21  depending on the cutting conditions or the like, the tip portion of the chip  10  can be reliably guided to the tensile force applying means  11 . Furthermore, the chip  10  can be smoothly guided without being jammed in the guide path forming member  21 . 
     In the above-described embodiments, the present invention is applied to the cutting tool used for turning. However, the cutting tool with the chip processing function according to the present invention is applicable to a cutting tool such as a planer which cuts a translating workpiece. 
     While the present invention has been described with respect to preferred embodiments thereof, it will be apparent to those skilled in the art that the disclosed invention may be modified in numerous ways and may assume many embodiments other than those specifically set out and described above. Accordingly, it is intended by the appended claims to cover all modifications of the present invention that fall within the scope of the invention.