Abstract:
A machine tool capable of performing screw-machining on a rotating workpiece has a tool rest which can attachably and detachably equip a turning tool with an insert on its tip and is provided so as to be freely driven to move in first and second axial directions orthogonal to each other. The tool rest is also being provided so as to freely rotate about a third axis orthogonal to the first and second axial directions so as to be positioned at a selected tool-rest angle with respect to the workpiece. The machine tool includes suitable features to allow inputting of machining information, computing of a cutting pattern, and execution of screw-machining.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a machine tool that can machine screws in which dimension and shape differ, even if exclusive screw-cutting tools fitting with the shape of screw thread are not used. 
     Until now, when cutting screws using lathes, etc., they do this machining using the exclusive lathe tools fitting with the shape of flank portions of a screw&#39;s ridge (rill) to be machined. 
     However, many kinds of tools are necessary, each of which fits with each inclination of flank portion of ridges to be machined, when such method is adopted. Therefore, the setup of these tools takes time as well, as the number of tools is occupied for the screw-machining and the number of tools used for other machining is limited. There was such inconvenience. 
     This invention is based on in the superscription circumstance, and its purpose is to offer the machine tool, which can machine screws with flank portions of various inclinations by one tool. 
     SUMMARY OF THE INVENTION 
     In order to solve the above-mentioned problems, the invention mentioned in claim  1  is a machine tool, which has a tool rest that can attachably and detachably equip a turning tool with an insert on its tip, said tool rest is provided so as to be freely driven to move in the first and second axial direction (X, Z axial direction) orthogonalizing for each other, and said tool rest is also provided so as to freely rotate with the third axis (B axis) as a center orthogonalizing for said first and second axial direction and to be positioned at each angle, and which can do screw-machining on a rotating workpiece by said turning tool, comprising: 
     input means for inputting machining information in the screw-machining; 
     cutting pattern computing portion, which computes a cutting pattern, in which said screw-machining is executed so as to rotate said turning tool with said third axis as a center and position it, based on the machining information input by said input means; and 
     screw-machining executing portion executing said screw-machining on said workpiece based on the cutting pattern computed by said cutting pattern computing portion. 
     The invention of claim  1  so executes the screw-machining based on the cutting pattern in which the turning tool is rotated with the third axis as a center and positioned. So it is possible to machine screws with flank portions of various inclination by a single tool, without machining flank portions of ridges by the tools, as the convention, fitting with the inclination of the each flank portion. 
     The invention mentioned in claim  2  is characterized as said cutting pattern computing portion computes said cutting pattern in such a manner that the first flank and the second flank of a ridge are machined by the separate process. 
     The invention of claim  2  machines the first flank and the second flank of a ridge by the separate process. So it is possible to form the different inclination on the first flank and the second flank easily and to easily machine a screw of complicated shape as a saw blade screw. 
     The invention mentioned in claim  3  is characterized as said cutting pattern computing portion computes said cutting pattern in such a manner that said turning tool is inverted in machining the first flank and the second flank of said ridge. 
     The invention of claim  3  makes it possible to machine screws of more various shapes, if the turning tool is inverted when machining the first flank and the second flank of the ridge. 
     The invention mentioned in claim  4  is characterized as said cutting pattern computing portion computes said cutting pattern in such a manner that finish machining for the first flank and the second flank of a ridge are done by the separate process. 
     The invention of claim  4  makes the high-precise machining of a ridge, if finishing the first flank and the second flank of a ridge by the separate process. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a control block diagram showing an example of a screw-machining apparatus to which the present invention is applied; 
     FIG. 2 is a view showing an example of screw-cutting program; 
     FIG. 3 is a view showing an example of screw-cutting with a rectangular tool; 
     FIG. 4 is a view showing an example of screw-cutting with a lozenge tool; 
     FIG. 5 is a view showing an example of computing of cutting pattern. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A complex machining machine tool  1  has a main control portion  2 , as shown in FIG.  1 . Such an input portion as a keyboard  5 , a system program memory  6 , a tool file  7 , a cutting pattern computing portion  8 , a machining program memory  9 , a spindle control portion  10 , a tool rest control portion  11  and a display  12  are connected with the main control portion  2  via bus lines  3 . A spindle motor  13  is connected with the spindle control portion  10 . A spindle  15  is connected with the spindle motor  13 . The spindle  15  is so provided to be freely driven to rotate with the axial center CT, parallel to the Z axis, as a center and be positioned. And a chuck  16  is provided with the spindle  15 . Claws  16   a  are provided with the chuck  16 , which can hold or release a workpiece  17  to be machined and be driven to move in the direction as shown by the arrows C and D. 
     And, tool rest driving motors  19  (plural number) are connected with the tool rest control portion  11 . A tool rest  20  is so connected to the tool rest driving motors  19  that the tool rest  20  can be driven to move in the direction of the Z axis (the direction as shown by the arrows A and B) and in the direction as shown by the arrows E and F which is the right angle direction with the Z axis, that is, in the direction of the X axis direction by the tool rest driving motor  19 . Furthermore, the tool rest  20  is so provided as to be freely driven to move by the tool rest driving motor  19  in the Y axis direction which is the right angle direction with paper, having right angle with the X axis and the Z axis, and in the direction as shown by the arrows G and H which is the B axis direction with the Y axis as a center. 
     A tool holding portion  20   a  is formed on the tool rest  20 . A turning tool  21  is provided with the tool holding portion  20   a , being attachable to it, detachable from it and freely exchanged. The tool holding portion  20   a  is so provided as to freely fix and hold a tool in a predetermined holding state and to be freely driven to rotate in the direction as shown by the arrows I and J, which is the direction around the axial center CT 2 , and be positioned. 
     A rectangular byte for screw cutting  21 A among a plurality of turning tools  21  to be installed on the tool rest  20  has a main body  21   a  formed in the shape of round bar, as shown in FIG. 3. A rectangular insert  22 , which has a rectangular view as seen on a plane, is installed on the tip of the main body  21   a . And, a lozenge cutting tool for screw cutting  21 B among the plurality of tools  21  to be installed on the tool rest  20  has a main body  21   a  formed in the shape of round bar, as shown in FIG. 4. A lozenge insert  23 , which has a lozenge view as seen on a plane, is installed on the tip of the main body  21   a.    
     The complex machining machine tool  1  has the above-mentioned structure. Then, in order to form a screw having optional shape, such as a trapezium, a triangle and so on, on the workpiece  17  with the complex machining machine tool  1 , an operator firstly inputs various kinds of machining information necessary for the screw-machining by operating the keyboard  5 . The main control portion  2  reads out a known automatic program composing program from the system program memory  6  when the machining information is input to compose the machining program PRO for the screw-machining on the basis of the automatic program composing program. For example, the information is input into the machining program PRO, as is shown in FIG.  2 . At the digit of the unit name UNO, “THR OUT” which means screw-machining is input. At the digit of cutting pattern KP which indicates the cutting pattern of the screw, number “3” which means the arbitrary shape is input. In addition, the operator continues to input various machining information necessary for the machining by manipulating keyboards  5 . This machining information includes next items concerning the screw. These are, Lead RD shown in FIG.  3 (In FIG. 2, “10” which means 10 millimeters is input in lead RD.), angle AG (In FIG. 2, “60” which means 60° C. is input in angle AG.), number of threads NJ (In FIG. 2, “1” which means the 1-thread screw is input.), height HG (In FIG. 2, “2” which means 2 millimeters is input in height HG.), ridge width W (In FIG. 2, “5” which means 5 millimeters is input in ridge width W.), and tool name NA (This is “rectangle” which expresses the rectangle tool in FIG. 2.) used for the machining, which is also input. 
     When the machining information necessary for the machining is input and the machining program PRO is composed in this way, the composed machining program PRO is stored in the machining program memory  9 . 
     When the machining program PRO concerning the screw-machining is composed in this way, an operator instructs the main control portion  2  to perform the screw-machining on the workpiece  17  through the keyboard  5 . Receiving this, the main control portion  2  reads out the machining program PRO of the screw-machining concerning the workpiece  17  from the machining program memory  9  so as to perform the screw-machining, appropriately driving the spindle control portion  10  and the tool rest control portion  11 . 
     On this occasion, the main control portion  2  has the cutting pattern computing portion  8  to compute the detailed cutting pattern. That is, the cutting pattern computing portion  8  judges the screw&#39;s shape to be machined from tool name NA in the machining program PRO. The screw&#39;s shape to be machined is judged being trapezoidal screw or square screw, when tool name NA is “rectangle”, otherwise the screw&#39;s shape is judged being a triangular screw in case of “lozenge”. 
     Suppose the tool name NA should be “rectangle” and the screw&#39;s shape to be machined should be judged being a trapezoidal screw or a square screw. In this case, the cutting pattern computing portion  8  reads out the cutting pattern PAT 1  for a square screw stored in the system program memory  6  and computes and decides the concrete machining process based on the read cutting pattern PAT 1 . 
     The cutting pattern PAT 1  for a square screw is divided into next processes as is shown in FIG.  3 . These are, a) rough machining of the rill portion of the screw shown by circled numbers from  1  to  8  in the figure, b) rough machining of the flank portion  17   a  of the screw at the right side in the figure, shown by circled  9  in the figure, that is, rough machining in the first flank portion, c) finishing of the flank portion  17   a  of the screw at the right side in the figure, shown by circled  10  in the figure, that is, finishing in the first flank portion, d) rough machining of the flank portion  17   b  of the screw at the left side in the figure, shown by circled  11  in the figure, that is, rough machining in the second flank portion which faces the first flank portion, e) finishing of the flank portion  17   b  of the screw at the left side in the figure, shown by circled  12  in the figure, That is, finishing in the second flank portion. The detailed cutting data in each machining process is computed immediately from the input machining information, as is shown in FIG.  5 . 
     However cutting pattern PAT 2  for the triangular screw is read out from the system program memory  6 , when tool name NA is “lozenge”. This cutting pattern PAT 2  is shown in FIG.  4 ( a ). That is, a) rough machining of the rill portion of the screw shown by circled numbers from  1  to  3  in the figure, b) rough machining of the flank portion  17   a  of the screw at the right side in the figure, shown by circled numbers from  4  to  6  in the figure, that is, rough machining in the first flank portion, c) finishing of the flank portion  17   a  of the screw at the right side in the figure, shown by circled  7  in the figure, that is, finishing in the first flank portion, d) rough machining of the flank portion  17   b  of the screw at the left side in the figure, shown by circled numbers from  8  to  10  in the figure, that is, rough machining in the second flank portion which faces the first flank portion, e) finishing of the flank portion  17   b  of the screw at the left side in the figure, shown by circled  11  in the figure, that is, finishing in the second flank portion. Also the cutting pattern computing portion  8  similarly computes the cutting pattern PAT 2  based on the machining information input when composing the machining program PRO. 
     In this way, the main control portion  2  lets the spindle control portion  10  and the spindle driving motor  13  rotate the workpiece around the axial center CT based on the computed cutting patterns PAT 1  and PAT 2 , as well as it lets the tool rest control portion  11  and the tool rest driving motors  19  drive the tool rest to move in arrow A, B direction and arrow E, F direction, each of which is the X, Z axial direction. By this, the machining of the predetermined screw-cutting on the workpiece  17  by the bytes  21 A and  21 B is executed in the every process following the order indicated by circled numbers. 
     In either case of the cutting patterns PAT 1  and PAT 2 , what is characteristic is that the screw ridge is machined such that the bytes  21 A and  21 B are rotated in the arrow G, H direction, which is the B axial direction, to be positioned, as shown in FIG.  3  and FIG.  4 . Based on angle AG of the ridge of the machining program PRO, the cutting pattern computing portion  8  computes and decides this degree of the B axial angle, for example, as is shown by rough/finishing machining process (circled numbers from  9  to  12 ) of the first and the second flank portion in FIG.  5 . 
     That is to say, in rough machining and finishing in the flank portion, the bytes  21 A and  21 B carry out the machining such that these bytes are rotated in the arrow G, H direction, which is the B axial direction, and positioned. By this, it is possible to machine the flank portions  17   a  and  17   b  of the ridge at the optional angle, and to easily machine various screw ridges such as trapezoidal screws, square screws and triangular screws by tools of the little numbers such as a rectangular byte  21 A and a lozenge byte  21 B, even if the exclusive tools formed with the shape of a ridge is not used. 
     Still, it is also possible to do as following in the machining of a screw ridge. The cutting tools  21 A and  21 B are rotated with the axial center CT 2  of the tool holding portion  20   a  as a center in arrow I, J direction, which is the A axial direction, and positioned. In machining the first flank portion  17   a  and the second flank portion  17   b , each of which is on the left or right of the screw ridge, the cutting patterns PAT 1  and PAT 2  are decided such as inverting tools. Based on this, the cutting tools  21 A and  21 B are used. 
     The present invention is explained on the basis of the embodiments heretofore. The embodiments, which are described in the present specification, are illustrative and not limiting. The scope of the invention is designated by the accompanying claims and is not restricted by the descriptions of the specific embodiments. Accordingly, all the transformations and changes belonging to the claims are included in the scope of the present invention.